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Shoulder:Glenohumeral Arthritis/Reverse Shoulder Arthroplasty

2021-11-20T16:26:08Z

Marko.nabergoj: Complications - section impingement

==Bullet Points==

*Indications for reverse shoulder arthroplasty expended. Weight-bearing patients, preoperative deltoid or acromial impairment, in certain circumstances, are not an absolute contraindication to reverse shoulder arthroplasty.

*Deltopectoral, anterosuperior (transdeltoid), and deltoid and subscapularis sparing approaches are currently used. Transacromial approach has been abandoned.

*Adequate deltoid tension obtained through restoration of humeral and arm length is one of the keys for postoperative function and prevention of instability following reverse shoulder arthroplasty. With a classic Grammont prosthesis postoperative humeral lengthening is approximately 2 mm and arm lengthening is approximately 24 mm.

*Subclinical neurologic lesions after Medial Glenoid/Medial Humerus Design are a frequent with consequence of lengthening with a drastically increasing prevalence above 40 mm of arm lengthening. Lateralized designs seem to be protective. Arm lengthening should be controlled with 0 to 2 cm being a reasonable goal to avoid postoperative neurological impairment.

*Medial Glenoid/Medial Humerus 155 degrees neck-shaft angle designs are progressively replaced by lateralized and lower neck-shaft angle (145-135 degrees) designs that theoretically attain, compared to traditional Grammont-type prosthesis, an optimal compromise in range of motion and soft tissue tension.

*Anterior forward flexion and Constant scores after reverse shoulder arthroplasty plateau at 6 months postoperative whereas internal and external rotation continue to improve up to 2 years postoperative. Several preoperative factors are correlated with postoperative range of motion.

*Previously, complications have been reported to affect 19% to 68% of patients and include acromial fracture, haematoma, infection, instability, mechanical baseplate failure, neurological injury, periprosthetic fracture and scapular notching. The rate of postoperative complications has dramatically decreased.

*The launch of a variety of reverse shoulder arthroplasty designs on the market has introduced a myriad of prosthetic configurations that has rendered analysis and delivery of universal guidelines difficult.

==Key words==
Reverse total shoulder arthroplasty; prosthesis; postoperative function; humerus and arm length; deltoid impairment; muscle insufficiency; complications; indications, contraindications; impingement; humeral lateralization; glenoid; neck-shaft angle; function; range of motion; active forward flexion; predicting factors; results; clinical outcomes; weight-bearing joint; wheelchair; crutches.

==History==
Paul Grammont was born on April 1940 in Salins-les-Bains, in the northeastern part of France. He began medical studies in Lyon. Very quickly he became interested in surgery, and more specifically in orthopaedic surgery. He first became the fellow and then assistant of Professor Albert Trillat. He became a Professor of Orthopaedic Surgery and Traumatology in 1974 at the age of 34. He then moved to Dijon (France) where he became the Chairman of the Orthopaedic Department of the University Hospital. While he had few laboratory resources, he began many of his biomechanical shoulder experiments in his own garage. Grammont was creative: besides developing the reverse shoulder prosthesis,<ref>Grammont PM, Latfay, J, Deries X. [In French] Etude et réalisation d’une nouvelle prothèse d’épaule. Rhumatologie 1987;39: 407-418</ref> he also developed an early patellofemoral prosthesis<ref>Renard JF, Grammont P. [In French] La prothe`se autocentrique de rotule: technique et re´sultats apre`s 7 ans de recul. Rhumatologie.
1989;41:241–245.</ref> and one of the first nails with a self-advancing mechanism designed to lengthen long bones like the tibia and the femur (Albizia nail).<ref>Guichet JM, Grammont PM, Trouilloud P. [A nail for progressive lengthening. An animal experiment with a 2-year follow-up]. Chirurgie. 1992;118(6-7):405-410</ref> Paul Grammont died in Lyon the 30 March 2013.

==Anecdotes==
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==Human Development==
During evolution the permanently orthograde posture has freed the human shoulder girdle of its quadruped functions. The anterior limbs became the upper limbs with the characteristics of a non-weight-bearing joint. Major bony and muscular adaptations occurred.<ref>Baulot, E. Sirveaux, F. Boileau, P. Grammont's idea: The story of Paul Grammont's functional surgery concept and the development of the reverse principle. Clin Orthop Relat Res. 2011 Sep;469(9):2425-31</ref> The scapulohumeral complex underwent drastic changes to facilitate prehension, leading to major bony and muscular modifications. A relative atrophy of the supraspinatus muscle occurred, as illustrated by a decrease in the scapular index.<ref>Inman, VT. Saunders, M. Abbott, MC. Observations on the function of the shoulder joint. J Bone Joint Surg Br 1944;26(1):1-30</ref><ref>Pearl, R., and Schultz, F.: Human Biology: A Record of Research. Edited, Baltimore, Warwick and York Inc Publishers, 1930</ref> The decrease in the effectiveness of the latter muscle was at the same time compensated for by the increase in size, mass, and lateral extension of the acromion process. The progressive distal migration of the point of insertion of the deltoid muscle and lateralization of the acromion indicate the more dominant position occupied by the deltoid with strengthening in particular of the middle deltoid abduction component.<ref name=":27">Grammont, P. M.: Place de l’ostéotomie de l’épine de l’omoplate avec translation, rotation, élévation de l’acromion dans les ruptures chroniques de la coiffe des rotateurs. Lyon Chir 1979;55:327–329</ref>

The glenohumeral joint is highly mobile and relatively unconstrained. Stability of the joint relies upon concavity-compression whereby the rotator cuff exerts a compressive force of the humeral head upon the glenoid. In the absence of concavity-compression, the unopposed contraction of the deltoid creates a force vector that displaces the head superiorly rather than in abduction. Depending on the type of rotator cuff lesion, a patient may present with pseudoparalysis.

To compensate the loss of function of the rotator cuff, several options have been proposed; the most reasonable, whenever possible, is to repair the rotator cuff. Good results are obtained in the vast majority of the cases with healing of the rotator cuff on the tuberosities. In some circumstances, rotator cuff repair is however contraindicated or technically impossible.

For instance, a rotator cuff insufficiency associated with pain and pseudoparalysis remains a challenging condition. It is extremely difficult, if not impossible, to obtain a functionally good result with a conventional prosthetic arthroplasty in this situation, where only a “limited goals surgery” is appropriate, a concept introduced by Neer.<ref>Neer, C. S., 2nd; Craig, E. V.; and Fukuda, H.: Cuff-tear arthropathy. J Bone Joint Surg Am 1983;65(9):1232-44</ref> Effectively, hemiarthroplasty provides satisfactory pain relief but poor motion,<ref>Sanchez-Sotelo, J.; Cofield, R. H.; and Rowland, C. M.: Shoulder hemiarthroplasty for glenohumeral arthritis associated with severe rotator cuff deficiency. J Bone Joint Surg Am 2001;83(12):1814-22</ref> whereas total anatomic shoulder arthroplasty is complicated with early loosening of the glenoid component.<ref>Barrett, W. P.; Franklin, J. L.; Jackins, S. E.; Wyss, C. R.; and Matsen, F. A., 3rd: Total shoulder arthroplasty. J Bone Joint Surg Am 1987;69(6):865-72</ref>

In order to provide active forward elevation above 90 degrees, the abduction role of the deltoid has to be increased. This can be obtained by several mechanisms, such as an osteotomy of the scapular spine<ref name=":27" /> or more commonly by medializing the center of rotation the glenohumeral joint.<ref>Grammont, P. M.; Bourgon, J.; and Pelzer, P.: Study of a Mechanical Model for a Shoulder Total Prosthesis: Realization of a Prototype. In ECAM de Lyon. Edited, Dijon, Université Dijon, 1981</ref> The concept of functional surgery is born from the latter option: whereas no effective anatomic solution exists, restoration of function has to be proposed through a novel morphology.

The first-generation of reverse shoulder arthroplasty has been implanted in Germany and France.<ref>Gérard, Y.; Leblanc, J. P.; and Rousseau, B.: A complete shoulder prosthesis. Chirurgie 1973;99:655–663</ref><ref>Kolbel, R., and Friedebold, G.: [Shoulder joint replacement]. Arch Orthop Unfallchir 1973;76(1):31-9</ref> However, early loosening and mechanical complications forced to abandon their use. Nevertheless, successive improvements imagined by Grammont followed and, in 1991, a reverse shoulder arthroplasty called the “Delta III” has been developed.<ref name=":36">Baulot, E.; Chabernaud, D.; and Grammont, P. M.: [Results of Grammont's inverted prosthesis in omarthritis associated with major cuff destruction. Apropos of 16 cases]. Acta Orthop Belg 1995;61(Suppl 1):112-9</ref> The two major innovations were a large metal hemisphere with no neck on the glenoid side, and a small humeral polyethylene cup (covering less than half of the hemisphere), oriented with a nonanatomic inclination of 155 degree.

==Biomechanics==

#REDIRECT [[https://wiki.beemed.com/view/Shoulder:Biomechanics]<nowiki>]</nowiki>

Reverse shoulder arthroplasty, often used in multiply operated patients with distorted anatomy, imparts physiological and biomechanical changes that may increase the potential for complications.<ref name=":5">Farshad M, Gerber C. Reverse total shoulder arthroplasty-from the most to the least common complication. Int Orthop. 2010 Dec;34(8):1075-82</ref>

First, the arthroplasty position medializes and lowers the glenohumeral center of rotation, thereby increasing the lever of the deltoid muscle (Medial Glenoid/Medial Humerus Design). Deltoid tension, increased by the lowered center of rotation, increases muscle fiber recruitment of the anterior and posterior deltoid that compensates for a deficient rotator cuff (Figure). The medialization increased the deltoid moment arm up to 20%, and an inferior move increased the efficacy of the deltoid up to 30%.<ref>Terrier A, Reist A, Merlini F, Farron A. Simulated joint and muscle forces in reversed and anatomic shoulder prostheses. J Bone Joint Surg Br 2008;90:751-6.</ref>

[[File:Muscle recruitment.jpg|thumb|center|(A) Native shoulder. The center of rotation is in the humeral head, and the level of arm of deltoid does not allow deltoid recruitment. (B) Bony increased-offset reverse shoulder arthroplasty with lateral glenoid/medial humerus design. As in native shoulders, the bony lateralization of the center of rotation decreases recruitment of the deltoid for rotation. (C) Grammont reverse shoulder arthroplasty with humeral lateralization with a medial glenoid/lateral humerus design. Medialization of the center of rotation and humeral lateralization allows important deltoid recruitment. Reproduced from Collin et al.,<ref name=":6">Collin P, Liu X, Denard PJ, Gain S, Nowak A, Lädermann A. Standard versus bony increased-offset reverse shoulder arthroplasty: a retrospective comparative cohort study. J Shoulder Elbow Surg. 2018;27(1):59-64</ref> with permission.]]

Second, to provide an inherently stable reverse shoulder arthroplasty, the weight bearing part is convex and the supported part concave (reversal of the ball and socket). The fixed nature of the glenosphere places torsional forces on the humerus that may affect humeral component instability.<ref name=":37">Melis B, DeFranco M, Lädermann A, Molé D, Favard L, Nérot C, Maynou C, Walch G. An evaluation of the radiological changes around the Grammont reverse geometry shoulder arthroplasty after eight to 12 years. J Bone Joint Surg Br. 2011 Sep;93(9):1240-6</ref> The native spinning joint becomes a hinge joint, new configuration that leads to various impingements’ types and locations.

Third, the semi-constrained nature of the prosthesis restores glenohumeral stability which provides the stable fulcrum which is essential for active anterior elevation.

Finally, lengthening of the arm which provides space for range of motion of the proximal humerus,<ref name=":32">Lädermann A, Edwards TB, Walch G. Arm lengthening after reverse shoulder arthroplasty: a review. Int orthop 2014;38:991-1000</ref> enhances stability, and re-tensions the deltoid. The latter factor is critical due to the semi-constrained design of the prosthesis. The increase in compressive force between the humeral and glenoid components has a stabilizing effect.<ref>Gagey O, Hue E. Mechanics of the deltoid muscle. A new approach. Clin Orthop Relat Res 2000:250-7</ref> Under such tension, the reverse glenoid component provides the stable fulcrum essential for shoulder anterior elevation and prosthesis stability.<ref name=":28">Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and biomechanics. J Shoulder Elbow Surg 2005;14:147S-61S</ref> This tension is determined by arm length.

===Arm Lengthening===
Failure to adequately tension the deltoid may result in prosthetic instability and poor function which are the most common clinically significant complications following reverse shoulder arthroplasty. On the other hand, other complications following reverse shoulder arthroplasty can be related to excessive deltoid tension such as neurological lesions, fractures of the acromion, or fixed abduction of the arm.<ref name=":28" /><ref>Boileau P, Watkinson D, Hatzidakis AM, Hovorka I. Neer Award 2005: The Grammont reverse shoulder prosthesis: results in cuff tear arthritis, fracture sequelae, and revision arthroplasty. J Shoulder Elbow Surg 2006;15:527-40</ref> Adequate deltoid tension is thus accepted as a key to prosthetic function and stability.<ref name=":28" /><ref name=":32" />

The glenosphere has to be implanted on the lower part of the glenoid to avoid notching and to improve rotation at 90 degrees of abduction.<ref>De Biase CF, Ziveri G, Delcogliano M, de Caro F, Gumina S, Borroni M, Castagna A, Postacchini R.The use of an eccentric glenosphere compared with a concentric glenosphere in reverse total shoulder arthroplasty: two-year minimum follow-up results. Int Orthop. 2013 Oct;37(10):1949-55</ref><ref name=":3">Lädermann A, Tay E, Collin P, Piotton S, Chiu CH, Michelet A, Charbonnier C. Effect of critical shoulder angle, glenoid lateralization, and humeral inclination on range of movement in reverse shoulder arthroplasty. Bone Joint Res. 2019;8(8):378-386</ref><ref>Lévigne C, Garret J, Boileau P, Alami G, Favard L, Walch G. Scapular notching in reverse shoulder arthroplasty: is it important to avoid it and how? Clin Orthop Relat Res. 2011 Sep;469(9):2512-20</ref><ref name=":37" /><ref name=":38">Mizuno N, Denard PJ, Raiss P, Walch G. The clinical and radiographical results of reverse total shoulder arthroplasty with eccentric glenosphere. Int Orthop. 2012 Aug;36(8):1647-53</ref><ref name=":39">Nyffeler RW, Werner CM, Gerber C. Biomechanical relevance of glenoid component positioning in the reverse Delta III total shoulder prosthesis. J Shoulder Elbow Surg 2005;14:524-8.</ref> The type of glenosphere (size, eccentricity) allowed the adjustment of arm length by several millimeters (about 1% of arm length). Consequently, the key factors for arm length are the height of the stem, type of stem, polyethylene thickness and the use of an augment or spacer. Collectively, these factors allow arm lengthening by up to several centimeters (about 10% of arm length).<ref name=":32" /> The tension is thus determined by arm length. The latter is dependent of 1) the position of the glenosphere in the frontal plane (Figure), 2) the size of the glenosphere, 3) the use of an eccentric or inferiorly tilted glenosphere, 4) the use of a spacer, 5) the thickness of the polyethylene, 6) the height of humeral cut and stem implantation (Figure 3)<ref name=":29">Lädermann A, Walch G, Lubbeke A, Drake GN, Melis B, Bacle G, Collin P, Edwards TB, Sirveaux F. Influence of arm lengthening in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2012 Mar;21(3):336-41</ref> and prosthetic design (Figure).

[[File:Image2-19.jpg|thumb|center|Influence of position of glenosphere in vertical plane. (A) A rather high implantation of the baseplate or the use of a non-eccentric glenosphere does not allow proper deltoid re-tensioning. (B) The use of an eccentric glenosphere or a low position of the glenosphere in the vertical plane allows satisfactory deltoid re-tensioning,<ref name=":29" /> with permission]]

[[File:Image3-21.jpg|thumb|center|Influence of the humeral cut on arm length. (A) Preoperative status with a lack of deltoid tension. (B-C) An aggressive humeral cut results in a low implantation of the stem with a lack of deltoid tension. (D-E) A minimal humeral cut leads to a high implantation of the prosthetic stem with adequate deltoid tension. From: Lädermann et al., with permission,<ref name=":29" /> with permission]]

[[File:Image4-23.jpg|thumb|center|The neck-shaft angle is one of the biggest variabilities between different prosthesis designs. A steeper or more anatomic neck-shaft angle (Grammont-type 155 degrees vs. 145 degrees and 135 degrees designs) leads to a decrease in the acromiohumeral distance. For every 10 degrees decrease the acromiohumeral distance shortens by approximately 3 mm. In other words, between a 155 degrees and a 135 degrees configuration, arm lengthening varies by about 10 mm.]]

From a clinical perspective lengthening of the arm and humerus, distalization angle, acromio-prosthesis distance (Figures) have been used as surrogates for deltoid tension since they intuitively correlate with deltoid tension and they have been correlated with functional outcome and risk of postoperative instability.<ref>Boutsiadis A, Lenoir H, Denard PJ, Panisset JC, Brossard P, Delsol P, Guichard F, Barth J. The lateralization and distalization shoulder angles are important determinants of clinical outcomes in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2018 Jul;27(7):1226-1234</ref><ref name=":30">Lädermann A, Williams MD, Melis B, Hoffmeyer P, Walch G. Objective evaluation of lengthening in reverse shoulder arthroplasty.J Shoulder Elbow Surg. 2009 Jul-Aug;18(4):588-95</ref><ref name=":29" /> Most of these factors nowadays can easily be evaluated thank to navigation software.<ref name=":40">Iannotti JP, Walker K, Rodriguez E, Patterson TE, Jun BJ, Ricchetti ET. Accuracy of 3-Dimensional Planning, Implant Templating, and Patient-Specific Instrumentation in Anatomic Total Shoulder Arthroplasty. J Bone Joint Surg Am. 2019 Mar 6;101(5):446-457</ref><ref name=":41">Walch G, Vezeridis PS, Boileau P, Deransart P, Chaoui J. Three-dimensional planning and use of patient-specific guides improve glenoid component position: an in vitro study. J Shoulder Elbow Surg. 2015 Feb;24(2):302-9</ref>

[[File:Figure3.jpg|thumb|center|The epicondylar line (EL) is defined between the most lateral part of the medial and lateral epicondyle. Another line, the diaphyseal axis (DI), is determined by a line drawn in the centre of the proximal medullary canal. Intersection between the epicondylar line and the diaphyseal axis represent the point C. Intersection between the diaphyseal axis and top of the humeral head is named H. The point A is located at the intersection between the diaphyseal axis and a perpendicular line passing through the most lateral and inferior point of the acromion. A, C, and H are represented by small white points, large white points corresponding to centimeter marker stuck on the skin of the arm. A, acromion; C, condyles; H, head; EL, epicondylar line; DI, diaphyseal axis; preop, preoperative; contro, controlateral; EF, enlargement factor, <ref name=":30" /> with permission]]

[[File:DLA 1 blinded.png|thumb|center|The distalization shoulder angle (DSA) angle is formed by a line connecting the most lateral border of the acromion and the superior glenoid tubercle and a line connecting the superior glenoid tubercle and the most superior border of the greater tuberosity. In this case, it is measured at 61 degrees.]]

===Lateralization in Reverse Shoulder Arthroplasty===
The basic biomechanical principles of the Grammont reverse shoulder arthroplasty are a medialization of the glenohumeral center of rotation, the use of a larger ball on the glenoid component, and a lowering of the humerus. These principles increase the deltoid lever arm and provide a space for unrestricted range of motion of the proximal humerus and a stable fulcrum essential for active elevation and stability.<ref name=":28" /> However, many complications, such as limited postoperative range of motion or impingement that could be attributed to the medialized glenoid design, have been reported in the literature.<ref name=":1">Gerber C, Pennington SD, Nyffeler RW. Reverse total shoulder arthroplasty. J Am Acad Orthop Surg 2009;17:284-95</ref> To address these problems, several authors have proposed a change in the design of the Grammont prosthesis, promoting an increased bony or metallic glenoid offset.<ref name=":31">Boileau P, Moineau G, Roussanne Y, O'Shea K. Bony increased-offset reversed shoulder arthroplasty: minimizing scapular impingement while maximizing glenoid fixation. Clin Orthop Relat Res 2011;469:2558-67</ref><ref name=":13">Gutierrez S, Levy JC, Frankle MA, Cuff D, Keller TS, Pupello DR, Lee WE 3rd. Evaluation of abduction range of motion and avoidance of inferior scapular impingement in a reverse shoulder model. J Shoulder Elbow Surg 2008;17:608-15</ref> Different methods to measure glenoid lateralization have been proposed.<ref>Frankle MA, Teramoto A, Luo ZP, Levy JC, Pupello D. Glenoid morphology in reverse shoulder arthroplasty: classification and surgical implications. J Shoulder Elbow Surg 2009;18:874-85</ref><ref name=":8">Jobin CM, Brown GD, Bahu MJ, Gardner TR, Bigliani LU, Levine WN, Ahmad CS. Reverse total shoulder arthroplasty for cuff tear arthropathy: the clinical effect of deltoid lengthening and center of rotation medialization. J Shoulder Elbow Surg 2012;21:1269-77</ref>

====Definitions====
It is important to understand the differences between humeral or glenoid lateralization. These factors can be used to predict range of motion and vary based on prosthesis and technical factors. Humeral lateralization is defined as the distance from the center of the polyethylene cup, and the lateral part of the greater tuberosity (Figure). It can be estimated by the lateralization shoulder angle (Figure).

[[File:Image5-25.jpg|thumb|center|3D distances corresponded to the radius of spheres. Offset of the sphere were centered on the center of the polyethylene cup (pivot point) and of the bony glenoid center (GC) for humeral (A) and global offset (B), respectively, and included the lateral part of the greater tuberosity. ]]

[[File:LSA.png|thumb|center|The lateralization shoulder angle is formed by a line connecting the superior glenoid tubercle and the most lateral border of the acromion and a line connecting the most lateral border of the acromion and the most lateral border of the greater tuberosity. In this case, it is measured at 77 degrees.]]

It depends upon glenoid wearing, reaming and grafting, contact of the baseplate with the glenoid, the offset of the glenosphere and/or baseplate, the glenosphere diameter and tilt, the level of the humeral cut, the humeral neck-shaft angle, the humeral prosthetic design, the use of a spacer, the polyethylene thickness (humeral polyethylene socket offset), and the remaining proximal and lateral humeral bone stock.

At the other end of the spectrum, failure to adequately restore bone or prosthetic humeral lateralization may result in loss of humeral contour,<ref>Chacon A, Virani N, Shannon R, Levy JC, Pupello D, Frankle M. Revision arthroplasty with use of a reverse shoulder prosthesis-allograft composite. J Bone Joint Surg Am. 2009 Jan;91(1):119-27</ref> and deltoid shape curve and thus deltoid retensionning, and could lead to prosthetic instability and poor postoperative function.<ref name=":29" /><ref name=":30" />

===Neck-shaft angle===
More anatomic neck-shaft angles decrease the rate of scapular notching and improve postoperative range of motion.<ref name=":3" /><ref name=":11" />

The launch of this variety of designs on the market has introduced a myriad of prosthetic configurations that has rendered analysis and delivery of universal guidelines difficult.

===Range of motion after reverse shoulder arthroplasty: which combinations of humeral stem and glenosphere work the best?===
Reproduced from Lädermann et al., with permission.<ref>Lädermann A, Collin P, Denard PJ. Range of motion after reverse shoulder arthroplasty: Which combinations of humeral stem and glenosphere work the best? Obere Extremität 2020 doi:10.1007/s11678-020-00599-5</ref>
====Introduction====
The initial reverse shoulder arthroplasty design was excellent at restoring forward flexion but had several design-related complications including bony impingement and scapular notching,<ref name=":11">Lädermann A, Denard PJ, Collin P, Zbinden O, Chiu JC, Boileau P, Olivier F, Walch G. Effect of humeral stem and glenosphere designs on range of motion and muscle length in reverse shoulder arthroplasty. Int Orthop. 2020;44(3):519-30</ref><ref name=":37" /> instability,<ref>Chae J, Siljander M, Wiater JM. Instability in Reverse Total Shoulder Arthroplasty. J Am Acad Orthop Surg 2018;26:587-596</ref> acromial fractures,<ref name=":18">Haidamous G, Lädermann A, Frankle M, Gorman A, Denard PJ. The risk of postoperative scapular spine fracture following reverse shoulder arthroplasty is increased with an onlay humeral stem. J Shoulder Elbow Surg. 2020;9:S1058-2746(20)30337-2.</ref> limited range of motion (particularly internal and external rotation),<ref name=":10">Denard PJ, Lädermann A, Haidamous G, Hartzler R, Parsons BO, Lederman ES, Tokish JM. Radiographic Parameters Associated With Excellent Versus Poor Range Of Motion Outcomes Following Reverse Shoulder Arthroplasty. Shoulder & Elbow 2020;9:1758573220936234.</ref><ref>Lädermann A, Denard PJ, Tirefort J, Collin P, Nowak A, Schwitzguebel A J-P. Subscapularis- and deltoid-sparing vs traditional deltopectoral approach in reverse shoulder arthroplasty: a prospective case-control study. J Orthop Surg Res 2017;12:112</ref> and humeral stem loosening.<ref name=":37" /><ref>Lädermann A, Schwitzguebel AJ, Edwards TB, Godeneche A, Favard L, Walch G, Sirveaux F, Boileau P, Gerber C. Glenoid loosening and migration in reverse shoulder arthroplasty. Bone Joint J. 2019;101-B:461-469</ref> Many of these have been attributed to the initial Grammont design which featured a medialized glenosphere and 155 degrees straight stem (Medial Glenoid/Medial Humerus Design).<ref name=":1" />

A variety of changes in prosthetic design have been proposed to address these issues either on the humeral side or on the glenoid side, the goal being to decrease scapular notching, maximize efficiency of the remaining rotator cuff, improve stability and improve range of motion. On the glenoid side authors have promoted increased lateralization either with bone or metal.<ref name=":31" /><ref name=":4">Gutiérrez S, Comiskey CA 4th, Luo ZP, Pupello DR, Frankle MA. Range of impingement-free abduction and adduction deficit after reverse shoulder arthroplasty. Hierarchy of surgical and implant-design-related factors. J Bone Joint Surg Am . 2008;90(12):2606-15</ref> On the humeral side, a more anatomic humeral inclination (i.e. 145 or 135 degrees) and inlay and onlay systems designs have introduced a myriad of prosthetic configurations that has rendered analysis and delivery of universal guidelines difficult.

Therefore, the aim of this chapter is to evaluate the advantages and inconvenience of different reverse shoulder arthroplasty’s designs and to provide recommendations accordingly.

====Glenoid Configuration====
Glenoid configuration has an important effect on postoperative range of motion. The three most important variables are glenoid offset, eccentricity, and glenosphere size. None of these latter parameters influence significantly the measured bone strains at the glenoid near the bone-implant interface.<ref>Pauzenberger L, Dwyer C, Obopilwe E, Nowak MD, Cote M, Romeo AA, Mazzocca AD, Dyrna F. Influence of glenosphere and baseplate parameters on glenoid bone strains in reverse shoulder arthroplasty. BMC musculoskeletal disorders 2019;20(1):587</ref>

=====Glenoid Offset (lateralization)=====
The initial Grammont-style reverse shoulder arthroplasty utilized a glenosphere with a medialized center of rotation. While this design reliably improved forward elevation, the high rate of scapular notching and internal and external rotation deficit observed with this design have been attributed to the medialized glenoid design.<ref name=":1" /><ref>Lawrence C, Williams GR, Namdari S. Influence of Glenosphere Design on Outcomes and Complications of Reverse Arthroplasty: A Systematic Review. Clinics in orthopedic surgery 2016;8:288-297</ref> To address these problems, glenoid lateralization have been proposed to decrease scapular notching, improve soft tissue tension, and increase impingement-free range of motion. The glenoid component is considered as lateralized if lateralization equals or exceeds 5 mm compared to Grammont design.<ref>Werthel JD, Walch G, Vegehan E, Deransart P, Sanchez-Sotelo J, Valenti P. Lateralization in reverse shoulder arthroplasty: a descriptive analysis of different implants in current practice. Int Orthop 2019;43:2349-2360</ref> It is important to note that this lateralization of the center of rotation is relative to the implant designed by Grammont, but still medialized compared to the native glenohumeral joint. Lateralization can be achieved by either the placement of bone medial to the baseplate (bone increase offset reverse shoulder arthroplasty (BIO-RSA))<ref name=":31" /> or with metallic lateralization via the baseplate or glenosphere. While both have been associated with clinical improvement,<ref>Ernstbrunner L, Werthel JD, Wagner E, Hatta T, Sperling JW, Cofield RH. Glenoid bone grafting in primary reverse total shoulder arthroplasty. J Shoulder Elbow Surg 2017;26:1441-1447</ref><ref>Klein SM, Dunning P, Mulieri P, Pupello D, Downes K, Frankle MA. Effects of acquired glenoid bone defects on surgical technique and clinical outcomes in reverse shoulder arthroplasty. J Bone Joint Surg Am 2010;92:1144-1154</ref> metallic lateralization appears to be less subject to displacement, particularly with lateralization beyond 5 mm.<ref>Denard PJ, Lederman E, Parsons BO, Romeo AA. Finite element analysis of glenoid-sided lateralization in reverse shoulder arthroplasty. J Orthop Res 2017;35:1548-1555</ref>

Basic science studies show several benefits of lateralization. In both sawbone<ref name=":13" /> and computer models,<ref name=":4" /><ref name=":21">Kim SJ, Jang SW, Jung KH, Kim YS, Lee SJ, Yoo YS. Analysis of impingement-free range of motion of the glenohumeral joint after reverse total shoulder arthroplasty using three different implant models. Journal of orthopaedic science : official journal of the Japanese Orthopaedic Association 2019;24:87-94</ref><ref name=":3" /> lateralization improves range of motion in all directions.<ref name=":3" /> Lateralization also leads to improvement in stability.<ref>Ferle M, Pastor MF, Hagenah J, Hurschler C, Smith T. Effect of the humeral neck-shaft angle and glenosphere lateralization on stability of reverse shoulder arthroplasty: a cadaveric study. J Shoulder Elbow Surg 2019;28:966-973</ref>

The question remains how much lateralization is ideal. While clinical evidence is currently lacking, computer modeling suggests that 5 to 10 mm of lateralization relative to the native glenoid is ideal.<ref name=":3" /><ref name=":14">Werner BS, Chaoui J, Walch G. The influence of humeral neck shaft angle and glenoid lateralization on range of motion in reverse shoulder arthroplasty. J Shoulder Elbow Surg 2017;26(10):1726-1731</ref><ref>Gutiérrez S, Greiwe RM, Frankle MA, Siegal S, Lee WE 3rd. Biomechanical comparison of component position and hardware failure in the reverse shoulder prosthesis. J Shoulder Elbow Surg 2007;16:S9-S12</ref> Nevertheless, clinical data to date has not necessarily proved that lateralization improves range of motion<ref name=":6" /> or outcome scores<ref>Helmkamp JK, Bullock GS, Amilo NR, Guerrero EM, Ledbetter LS, Sell TC, Garrigues GE. The clinical and radiographic impact of center of rotation lateralization in reverse shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg, 2018, 27:2099-2107</ref> compared to a traditional reverse shoulder arthroplasty. Greiner et al. performed a randomized controlled trial of 17 Grammont reverse shoulder arthroplasties and 17 BIO-RSAs and reported no difference in Constant scores at 1 year postoperative.<ref>Greiner S, Schmidt C, Herrmann S, Pauly S, Perka C. Clinical performance of lateralized versus non-lateralized reverse shoulder arthroplasty: a prospective randomized study. J Shoulder Elbow Surg, 2015, 24:1397-1404</ref> In a retrospective study, Athwal et al. did not observe substantial range of motion, strength, or outcome scores.<ref name=":22">Athwal GS, MacDermid JC, Reddy KM, Marsh JP, Faber KJ, Drosdowech D. Does bony increased-offset reverse shoulder arthroplasty decrease scapular notching? J Shoulder Elbow Surg, 2015, 24:468-473</ref> The frequency of scapular notching, however, was significantly higher (P=.022) in the reverse shoulder arthroplasty cohort than in the BIO-RSA cohort: 75% versus 40%.<ref name=":22" /> This finding has been also reported by Zitkovsky et al.<ref name=":15">Zitkovsky HS, Carducci MP, Mahendraraj KA, Grubhofer F, Jawa A. Lateralization and Decreased Neck-Shaft Angle Reduces Scapular Notching and Heterotopic Ossification. J Am Acad Orthop Surg. 2020 Apr 8. doi: 10.5435/JAAOS-D-19-00808. Online ahead of print.</ref> At 10 years follow-up, Kennon et al. confirmed that scapular notching rates are significantly higher with medialized components compared to lateralized ones (77% in vs. 47%, P= .013).<ref>Kennon JC, Songy C, Bartels D, Statz J, Cofield RH, Sperling JW, Sanchez-Sotelo J. Primary reverse shoulder arthroplasty: how did medialized and glenoid-based lateralized style prostheses compare at 10 years? J Shoulder Elbow Surg. 2020;29(7S):S23-S31</ref> Notably, all of the these studies utilized a 155 degrees humeral prothesis and thus further comparative studies are required with 135 and/or 145 degrees protheses.

=====Glenosphere Eccentricity=====
Inferior eccentric positioning of the glenosphere can also be used to decrease the adduction deficit and thus reduce scapular notching.<ref name=":21" /><ref name=":7">Lädermann A, Denard PJ, Boileau P, Farron A, Deransart P, Walch G. What is the best glenoid configuration in onlay reverse shoulder arthroplasty? Int Orthop. 2018;42(6):1339-1346</ref> Mizuno et al. previously reported that an inferiorly eccentric glenosphere reduced the severity of scapular notching with a 155 degrees prosthesis,<ref name=":38" /> improving thus postoperative rotations elbow at side.<ref name=":2">Lädermann A, Gueorguiev B, Charbonnier C, Stimec BV, Fasel JH, Zderic I, Hagen J, Walch G. Scapular Notching on Kinematic Simulated Range of Motion After Reverse Shoulder Arthroplasty Is Not the Result of Impingement in Adduction. Medicine (Baltimore). 2015;94(38):e1615</ref> While the differences are small, the eccentric glenosphere provided the greatest ability to limit scapular notching while maximizing range of motion by increasing the subacromial space.<ref name=":7" /><ref name=":3" /> Abduction is effectively positively correlated with acromiohumeral distance (r = 0.93; p < 0.001) which is increased with an eccentric glenosphere.<ref name=":11" /> Rotation in abduction is important to activities of daily living. Interestingly, the latter are impossible in most configurations due to inexistent subacromial space (Figure 9). Postero-inferior eccentricity can improve also extension and could favorize as well internal rotation hand in the back (Figure).

[[File:Figure 1.png|thumb|Rotations rotation at 90 degrees of abduction might be impossible due to inexistent subacromial space. Eccentric positioning of the glenosphere creates subacromial space.]]

[[File:Figure 2 Postero-inferior eccentricity.png|thumb|Postero-inferior eccentricity improves extension. A) Inferior eccentricity alone (yellow arrow) allows 52 degrees of extension. B) 40 degrees of postero-inferior eccentricity (yellow arrow) improves extension to 73 degrees.]]

It is important to note, however, that inferior overhang of the glenosphere can be achieved either by an eccentric glenosphere or by baseplate position. Conversely, an eccentric glenosphere with an improperly positioned superior baseplate will not provide clinical benefit. Thus, the surgeon must be cognizant of both the overhang of the given glenosphere relative to the selected baseplate, as well as any eccentricity in the glenosphere. Furthermore, the benefits of overhang or eccentricity must be weighed against the risks of nerve injury and acromial fracture associated with arm lengthening. The ideal amount of overhang relative to the glenoid appears to be about 2.5 mm based on clinical evidence.<ref name=":10" />

=====Glenosphere size=====
The size of the glenosphere influences theoretically and clinically postoperative range of motion. Lädermann et al. found that a small glenosphere (36 mm) improves external rotation in abduction.<ref name=":7" /> However, with the elbow at side, larger diameter glenospheres have been shown to provide a greater impingement-free arc of motion, and decrease scapular notching in biomechanical studies. Werner et al. reported superior values for extension and external rotation with a 39 mm glenosphere compared to a 36 mm glenosphere mm.<ref name=":14" /> Berhouet et al. demonstrated in a cadaveric study that a 42 mm glenosphere was associated with improved rotational range of motion compared to a 36 mm glenosphere (p <0.05).<ref>Berhouet J, Garaud P, Favard L. Evaluation of the role of glenosphere design and humeral component retroversion in avoiding scapular notching during reverse shoulder arthroplasty.J Shoulder Elbow Surg . 2014;23(2):151-8</ref> Another study comparing functional scores and range of motion differences between two groups of patients, one receiving a 36 mm glenosphere and the other receiving a 44 mm glenosphere, found that patients with the larger glenosphere had a 12 degrees increase in external rotation in adduction compared to those with the smaller glenosphere (p <.001).<ref>Muller AM, Born M, Jung C, Flury M, Kolling C, Schwyzer HK, Audigé L. Glenosphere size in reverse shoulder arthroplasty: is larger better for external rotation and abduction strength? J Shoulder Elbow Surg 2018;27(1):44-52</ref> Similarly, Mollon et al. showed that a 42 mm glenosphere size generated a 15 degree improvement in forward flexion and a 6 degree improvement in external rotation compared to the 38 mm size, with an overall improvement in pain scores.<ref>Mollon B, Mahure SA, Roche CP, Zuckerman JD. Impact of glenosphere size on clinical outcomes after reverse total shoulder arthroplasty: an analysis of 297 shoulders. J Shoulder Elbow Surg. 2016;25(5):763-71</ref> Finally, a study by Haidamous et al. demonstrated that larger glenosphere size and inferior positioning as well as posterior humeral offset are associated with improved postoperative range of motion following reverse shoulder arthroplasty with a 135 degrees humeral component.<ref name=":10" /> Nevertheless, larger glenospheres limit abduction and rotations in abduction and are prone to higher volumetric wear rates and experienced greater polyethylene volume loss.<ref>Haggart J, Newton MD, Hartner S, Ho A, Baker KC, Kurdziel MD, Wiater JM. Neer Award 2017: wear rates of 32-mm and 40-mm glenospheres in a reverse total shoulder arthroplasty wear simulation model. J Shoulder Elbow Surg . 2017;26(11):2029-2037</ref> Additionally, one must consider patient size. Overstuffing can occur. Matsuki et al., for instance, demonstrated that small- and large-stature patients achieved lower improvement in range of motion with an RSA system with only 2 glenosphere sizes (38 and 42) likely because the small patients were overstuffed and the large patients did not have large enough glenospheres and/or lateralization.<ref>Matsuki K, King JJ, Wright TW, Schoch BS. Outcomes of reverse shoulder arthroplasty in small- and large-stature patients. J Shoulder Elbow Surg. 2018;27(5):808-815</ref>

====Humeral Stem Designs====
The primary humeral stem variables include stem geometry, neck-shaft angle, inlay versus onlay configuration, and humeral spacers.

=====Stem geometry=====
Short curved stems were initially developed to facilitate implantation, maintain bone stock, and preserve rotator cuff insertion.<ref>Lädermann A, Chiu JC, Cunningham G, Hervé A, Piotton S, Bothorel H, Collin P. Do short stems influence the cervico-diaphyseal angle and the medullary filling after reverse shoulder arthroplasties? Orthop Traumatol Surg Res. 2020;106(2):241-246</ref> These stems also change humeral offset based on their positioning in the humeral canal. In one study an onlay curve stem lead to a 7-mm increase in humeral offset compared to a traditional inlay straight Grammont prosthesis.<ref name=":12">Lädermann A, Denard PJ, Boileau P, Farron A, Deransart P, Terrier A, Ston J, Walch G. Effect of humeral stem design on humeral position and range of motion in reverse shoulder arthroplasty. Int Orthop. 2015;39(11):2205-13</ref> Curve stems decrease the acromiohumeral distance, which may lead to acromial impingement at small abduction angles.<ref name=":12" /> On the other hand, humeral lateralization can be useful to compensate for medialization in case of bone loss (Figure) and has been theorized to improve the mechanics of the remaining rotator cuff and deltoid musculature.<ref>Parry S, Stachler S, Mahylis J. Lateralization in reverse shoulder arthroplasty: A review. Journal of orthopaedics 2020;22:64-67</ref> Stem design appeared to have also a substantial effect on abduction, as combinations with the straight Grammont stem had greater abduction (73–80%), compared to those with the onlay curved stem (54–69%).<ref name=":11" />

[[File:Managing the eroded glenoid in shoulder arthroplasty Noumea 2019.jpg|thumb|Humeral lateralization can help to restore global lateralization in case of glenoid bone loss. A) Massive glenoid bone loss compensated by glenoid allograft and a straight stem (Lateral Glenoid/Medial Humerus concept). Observe that the central peg hardly reaches the native glenoid. Such construct has a potential for failure (B). Another option would have been to use a smaller glenoid graft and a curved stem (Lateral Glenoid/Lateral Humerus)]]

=====Neck-shaft angle (inclination)=====
The Grammont reverse shoulder arthroplasty was designed as a non-anatomic implant with a relative valgus humeral neck inclination of 155 degrees. Based on the work by Gutierrez et al.,<ref name=":13" /> neck-shaft angle has decreased in modern prosthetic designs to a more varus or anatomic inclination of 145 or 135 degrees.

The neck shaft angle is a major factor influencing length of the arm,<ref name=":37" /> but has little effect on humeral lateralization; by changing inclination from 155 degrees to 135 degrees within an onlay design, humeral offset only increased by about 2 mm.<ref name=":12" />

Theoretically, compared to low neck shaft angle stems, higher inclinations (155 degrees) increased abduction by 100% and external rotation in abduction, regardless of glenosphere designs.<ref name=":12" /><ref name=":3" /> This finding is important as such external rotation is a major factor in the ability to perform activities of daily activities such as hair care and facial grooming. However, a 155 degrees is associated with decreased adduction external rotation at the side<ref name=":12" /><ref>Nelson R, Lowe JT, Lawler SM, Fitzgerald M, Mantell MT, Jawa A. Lateralized Center of Rotation and Lower Neck-Shaft Angle Are Associated With Lower Rates of Scapular Notching and Heterotopic Ossification and Improved Pain for Reverse Shoulder Arthroplasty at 1 Year. Orthopedics. 2018;41(4):230-6</ref><ref name=":14" /> and extension due to medial bony impingement (which also leads to scapular notching).<ref name=":3" /><ref name=":11" /><ref name=":4" /><ref name=":14" /><ref>Oh JH, Shin SJ, McGarry MH, Scott JH, Heckmann N, Lee TQ. Biomechanical effects of humeral neck-shaft angle and subscapularis integrity in reverse total shoulder arthroplasty. J Shoulder Elbow Surg.2014;23(8):1091-8</ref><ref>Virani NA, Cabezas A, Gutiérrez S, Santoni BG, Otto R, Frankle M. Reverse shoulder arthroplasty components and surgical techniques that restore glenohumeral motion. J Shoulder Elbow Surg. 2013;22(2):179-87</ref> Lateralization obtained via a lower neck shaft angle increases adduction, by 357% between a 155 degrees prosthesis compared with a 135 degrees prosthesis. Also, an increase in extension, of 381%, and external rotation elbow at side, of 116%, are observed with a 135 degrees prosthesis.<ref name=":12" /> Such finding are important as external rotation with the elbow at the side and extension led to friction between the scapular pillar and the polyethylene insert. Even if this friction phenomenon does not limit range of motion, it likely contributes to progressive polyethylene wear and scapular notching.<ref name=":2" /> Reducing the neck-shaft angle can, however, have some negative effects on reverse shoulder arthroplasty contact mechanics. The contact area is reduced by 29% for 155 degrees to 145 degrees and by 59% for 155 degrees to 135 degrees. Consequently, there is an increased maximum contact stress by 71% for 155 degrees to 145 degrees and by 286% for 155 to 135 degrees.<ref>Langohr GD, Willing R, Medley JB, Athwal GS, Johnson JA. Contact mechanics of reverse total shoulder arthroplasty during abduction: the effect of neck-shaft angle, humeral cup depth, and glenosphere diameter. J Shoulder Elbow Surg. 2016;25(4):589-97</ref>

Gobezie et al. published the results of a randomized controlled trial comparing humeral inclination of 135 degrees to 155 degrees among patients undergoing reverse shoulder arthroplasty with a neutral glenosphere (no lateralization) and found no significant difference in forward flexion, external rotation, or functional outcomes.<ref name=":16">Gobezie R, Shishani Y, Lederman E, Denard PJ. Can a functional difference be detected in reverse arthroplasty with 135° versus 155° prosthesis for the treatment of rotator cuff arthropathy: a prospective randomized study. J Shoulder Elbow Surg. 2019;28(5):813-8</ref> They and other studies have confirmed that scapular notching is decreased with a 135 degrees prothesis.<ref name=":15" /><ref name=":16" /><ref name=":17">Erickson BJ, Frank RM, Harris JD, Mall N, Romeo AA. The influence of humeral head inclination in reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg. 2015;24(6):988-93</ref> A systematic review of 2222 shoulders comparing 135 degrees and 155 degrees prostheses reported higher rates of scapular notching in the 155 degrees group (16.8% vs. 2.8%), improved external rotation in the 135 degrees group, and no difference in instability of forward flexion between groups.<ref name=":17" />

Lastly, in case of fracture, reverse shoulder arthroplasty with a 135 degrees neck shaft angle is associated with higher tuberosity healing rates compared to 145 degrees or 155 degrees.<ref>O'Sullivan J, Lädermann A, Parsons BO, Werner B, Steinbeck J, Tokish JM, Denard PJ. A systematic review of tuberosity healing and outcomes following reverse shoulder arthroplasty for fracture according to humeral inclination of the prosthesis. J Shoulder Elbow Surg. 2020;29(9):1938-49</ref>

=====Onlay vs Inlay=====
Compared to on inlay design, an onlay humeral design with the same 155 degrees inclination increased humeral offset by 6.6 mm.<ref name=":12" /> Acromiohumeral distance varied by 9.8 mm with the smallest occurring with the onlay 135 degrees model and the largest occurring with a Grammont inlay 155 degrees. Compared to the inlay design, an onlay humeral design with the same 155 degrees inclination decreased the acromioclavicular distance by 4.1 mm. Compared to the onlay 155 degrees model, with the inlay 155 degrees model there was a 10 degree decrease (77.8 to 67.9 degrees) in abduction and a 5 degree (range, −15.3 to −20.2 degrees) increase in adduction.<ref name=":12" />

Clinically, Beltrame et al. conducted a prospective clinical study comparing onlay and inlay steams. They found that onlay design 145 degrees may provide better active external rotation, extension, adduction.<ref>Beltrame A, Di Benedetto P, Cicuto C, Cainero V, Chisoni R, Causero A. Onlay versus Inlay humeral steam in Reverse Shoulder Arthroplasty (RSA): clinical and biomechanical study. Acta Biomed. 2019;90(12-S):54-63</ref> However, there are numerous bias in their study (i.e. different neck shaft angle and stem lateralization) that prevent integration of their results in the present analysis.

In a retrospective comparative radiological study, Haidamous et al. showed similarly that an onlay humeral stem design resulted in a 10 mm increase in distalization compared to an inlay humeral stem, and a 2.5 times (11.9% vs 4.7%) increased risk of scapular spine fracture.<ref name=":18" /> It seems thus that the combination of lateralization and distalization in an onlay system dramatically increases the incidence of scapular spine fractures.

Lengthening of the supraspinatus and infraspinatus is systematically observed with an onlay design. It is greatest using onlay stems (7–30%) and lateralized glenospheres (13–31%).<ref name=":11" /> Subscapularis lengthening is observed for onlay stems combined with lateralized glenospheres (5–9%), while excessive subscapularis shortening is observed for the inlay stem combined with all glenospheres except the lateralized design (> 15%).<ref name=":11" />

=====Polyethylene Insert=====
Since inferior impingement between the polyethylene and the scapula is systematic with the arm at the side, another potential way to limit friction and notching in external rotation is to create a notch in the polyethylene inferiorly between 3 and 9 o’clock as it has been done in some prostheses (e.g., Arrow and SMR). Another solution to increase range of motion is to reduce the depth of the polyethylene inlay. De Wilde et al. found that for every 3-mm decrease in depth of polyethylene cup, ROM increased by 12 degrees.<ref>De Wilde LF, Poncet D, Middernacht B, Ekelund A.Prosthetic overhang is the most effective way to prevent scapular conflict in a reverse total shoulder prosthesis. Acta Orthop 2010 81:719-726</ref>

====Discussion====
The literature is controversial with regard to possibilities of regaining range of motion following reverse shoulder arthroplasty. While prosthetic designs are varied and lead to substantial changes in computer models, many of the theoretical advantages have not been confirmed clinically. Table summarizes implant design considerations to improve range of motion. The optimal compromise in range of motion for a primary reverse shoulder arthroplasty without bone loss could be a Lateral Glenoid/Medial (or Intermediate) Humerus design with a low neck shaft angle (145-135 degrees) and an inlay concept. However, all prosthetic designs should be considered on a case-by-case basis to optimize outcome. Glenoid and humeral prosthetic design has to be chosen depending on pre- and intra-operative factors including patient expectations, bone morphology, soft tissue state such as rotator cuff or nerve, approaches, surgical exposure, etc. It may, for example, not be possible to utilize a large glenosphere in all patients as they may not be appropriate for the anatomy of smaller individuals and might be more challenging technically. As a result, the surgeon must continuously weigh the benefits and possibilities of available implant-related variables regarding patient’s specific conditions. The systematic use of patient-specific instrumentation and navigation as well as preoperative determination of components are obviously the next steps in providing more accurate component positioning and size and thus improving range of motion. Despite the advances made by glenoid lateralization and inferiorization, there remains ample opportunity for continued improvement and innovation in prosthetic design.

=Preoperative planning=

Preoperative planning is mandatory as it allows to improve range of motion.<ref>Kolmodin J, Davidson IU, Jun BJ, Sodhi N, Subhas N, Patterson TE, Li ZM, Iannotti JP, Ricchetti ET. Scapular Notching After Reverse Total Shoulder Arthroplasty: Prediction Using Patient-Specific Osseous Anatomy, Implant Location, and Shoulder Motion. J Bone Joint Surg Am. 2018 Jul 5;100(13):1095-1103</ref> To guarantee the best possible functional results, restoration of the appropriate humeral and arm length, a and free range of motion should be the goal.<ref name=":8" /><ref name=":29" /><ref>Renaud P, Wahab H, Bontoux L, Dauty M, Richard I, Bregeon C. [Total inverted shoulder prosthesis and rotator cuff insufficiency: evaluation and determination of anatomical parameters predictive of good functional outcome in 21 shoulders]. Ann Readapt Med Phys 2001 ;44(5):273-80</ref> Even if the available softwares do not take into account soft tissue (stiffness, fatty infiltration,…), they are already able to plan and analyze lateralization and distalization.<ref name=":40" /><ref name=":41" />

=Indications and Contraindications=
==Indications==
Reverse shoulder arthroplasty is a powerful tool that has opened new barriers, especially for reconstructive shoulder surgery. Traditionally, the ideal candidate has been a patient above 70 years old with symptomatic cuff tear arthropathy. Appropriate candidates now include young patients, who have shown excellent clinical improvement with high implant survivorship of up to 10 years.<ref>Black EM, Roberts SM, Siegel E, Yannopoulos P, Higgins LD, Warner JJ. Reverse shoulder arthroplasty as salvage for failed prior arthroplasty in patients 65 years of age or younger. J Shoulder Elbow Surg 2014;23:1036-42</ref><ref>Ek ET, Neukom L, Catanzaro S, Gerber C. Reverse total shoulder arthroplasty for massive irreparable rotator cuff tears in patients younger than 65 years old: Results after five to fifteen years. J Shoulder Elbow Surg 2013;22:1199-208</ref><ref>Muh SJ, Streit JJ, Wanner JP, Lenarz CJ, Shishani Y, Rowland DY, Riley C, Nowinski RJ, Edwards TB, Gobezie R. Early follow-up of reverse total shoulder arthroplasty in patients sixty years of age or younger. J Bone Joint Surg Am 2013;95:1877-83</ref><ref>Otto RJ, Clark RE, Frankle MA. Reverse shoulder arthroplasty in patients younger than 55 years: 2- to 12-year follow-up. J Shoulder Elbow Surg 2017;26:792-7</ref><ref>Sershon RA, Van Thiel GS, Lin EC, McGill KC, Cole BJ, Verma NN, Romeo AA, Nicholson GP. Clinical outcomes of reverse total shoulder arthroplasty in patients aged younger than 60 years. J Shoulder Elbow Surg 2014;23:395-400</ref><ref>Walters JD, Barkoh K, Smith RA, Azar FM, Throckmorton TW. Younger patients report similar activity levels to older patients after reverse total shoulder arthroplasty. J Shoulder Elbow Surg2016;25:1418-24</ref>

Many pathologies that could not be treated previously found a solution through this design, and indications are currently expanding. It is now used for various conditions such as failed total shoulder arthroplasty or hemiarthroplasty, complex proximal humeral fractures and defective fracture union or nonunion, chronic locked dislocation, immunological arthritis with or without associated rotator cuff tears, failed or irreparable massive rotator cuff tears, and tumors.<ref>Smith CD, Guyver P, Bunker TD. Indications for reverse shoulder replacement: A systematic review. J Bone Joint Surg [Br] 2012;94:577-83</ref>
===Acute proximal humerus fracture===
Reverse shoulder arthroplasty is a more reliable treatment than hemiarthroplasty for complex proximal humerus fractures at least in elderly patients because its functional outcomes appear to depend less on tuberosity healing and rotator cuff integrity (Figure).<ref>Lädermann A, Chiu J, Collin P, Piotton S, Nover L, Scheibel M. Hemi- vs reverse shoulder arthroplasty for acute proximal humeral fractures: a systematic review of level I and II studies. Obere Extremität 2019;14:127–35</ref>

[[File:Figure 25 Millon.jpg|thumb|center|Reverse shoulder athroplasty for fracture.
Frontal, axial and lateral Lamy radiographs after a reverse total shoulder implant. Note the lower positioning of the glenoid baseplate, the satisfactory reconstruction of the tuberosities, and the absence of cement at the autograft level.]]

===Malunited/nonunited proximal humerus fracture===
Surgical options to address malunited proximal humerus fractures are determined largely by the existing deformity. They can be categorized broadly as humeral head-preserving techniques (e.g. osteotomies, soft-tissue releases and removal of bony protuberances) or humeral head-sacrificing techniques. Amongst the latter, reverse shoulder arthroplasty proved to be the most reliable.

[[File:Malunion Rickenbach.png|thumb|center|Reverse shoulder arthroplasty for malunion of proximal humeral fracture. A) Anteroposterior radiograph of a malunited proximal humerus fracture; B) post-operative radiograph of the fracture sequelae treated with reverse shoulder arthroplasty.]]

===Glenohumeral Osteoarthritis With Severe Glenoid Bone Loss===
The use of reverse shoulder arthroplasty in patients with severe glenoid bone loss and osteoarthritis is the best option. Excellent results have been reported in patients with osteoarthritis, an intact rotator cuff and substantial glenoid bone loss treated with reverse shoulder arthroplasty with or without bone grafting (Video).

[[File:Glenohumeral Osteoarthritis With Severe Glenoid Bone Loss.mp4|thumb|Fifty-one years old patient with right glenoid dysplasia (C glenoid) and an intact rotator cuff. Computed tomography (CT) scan of the shoulder shows 60 degrees of retroversion. The patient has been treated with combined bony and metallic augmentation. At three months follow-up, range of motion improves and imaging reveals satisfactory glenoid reconstruction.]]

===Chronic Locked Glenohumeral Joint Dislocation===
Chronic locked glenohumeral dislocation can also be treated with reverse shoulder arthroplasty (Figure).<ref>Statz JM, Schoch BS, Sanchez-Sotelo J, Sperling JW, Cofield RH.Shoulder arthroplasty for locked anterior shoulder dislocation: a role for the reversed design. Int Orthop. 2017 Jun;41(6):1227-1234</ref>

[[File:Locked dislocation treated by RSA.png|thumb|Locked dislocation of a right shoulder. On the right, postoperative X-ray.]]

===Rheumatoid Arthritis With or Without Associated Rotator Cuff Tears===
Excellent to satisfactory results have been reported for patients with rheumatoid arthritis treated with reverse shoulder arthroplasty. There is no higher complication rates as compared to reverse shoulder arthroplasty in cuff tear arthropathy.<ref>Cho CH, Kim DH, Song KS. Reverse Shoulder Arthroplasty in Patients with Rheumatoid Arthritis: A Systematic Review. Clin Orthop Surg. 2017 Sep;9(3):325-331</ref>

===Revision Arthroplasty===
Revision surgery after primary shoulder arthroplasty (i.e. hemiarthroplasty, resurfacing or total shoulder arthroplasty) produced high patient satisfaction (Figure). It is, however, associated with higher complication and failure rates compared to reverse shoulder arthroplasty for patients without previous arthroplasty.<ref>Gauci MO, Cavalier M, Gonzalez JF, Holzer N, Baring T, Walch G, Boileau P. Revision of failed shoulder arthroplasty: epidemiology, etiology, and surgical options. J Shoulder Elbow Surg. 2019 Oct 6. pii: S1058-2746(19)30531-2</ref>

[[File:Pitacollo TSA-RSA.jpg|thumb|center|A) Anteroposterior radiograph of a failed anatomic total shoulder arthroplasty; B) Anteroposterior post-operative radiograph after reverse shoulder arthroplasty.]]

===Tumours===
Reverse shoulder arthroplasty is an acceptable option for patients after wide resection of the proximal humerus and rotator cuff tendons for malignant bone tumours. However, a prerequisite for the ability to implant a reverse shoulder arthroplasty in these cases requires preservation of the axillary nerve and deltoid muscle to be successful.<ref>Bonnevialle N, Mansat P, Lebon J, Laffosse JM, Bonnevialle P. Reverse shoulder arthroplasty for malignant tumors of proximal humerus. J Shoulder Elbow Surg. 2015 Jan;24(1):36-44.</ref><ref name=":23" />

==Contraindications==
Absolute contraindications include general factors such as non compliance patients (severe psychiatric/neurologic disability, substance abuse), neuro-arthropathies (Charcot) and high patient morbidity (ASA 4+), and local factors like an uncontrolled active infection and substantial deltoid insufficiency because of the very high probability of recurrent instability and the minimal potential gain in function.<ref name=":23" />

=Clinical Practice Guideline=
The goal of this section is to provide clinicians with recommendations based on the best available evidence; to inform clinicians of when there is no evidence; and finally, to help clinicians deliver the best health care possible.

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=Approaches=
==Introduction==
Reverse shoulder arthroplasty can be performed through several approaches, the deltopectoral and anterosuperior being the most common, each with their advantages and disadvantages. The preparation is standardized for all approaches. The patient lies in the beach chair position with a 60° tilt of the chest, at the lateral extremity of the table, leaving the anterior and posterior sides of the shoulder free from obstruction. The elbow must be free from any support to enable the operating assistant to apply a proximally directed force at the elbow allowing proximal subluxation of the humeral head. The front arm rests on an armrest and is draped free.

==Deltopectoral Approach==
The deltopectoral approach allows increased visibility and accessibility of the humerus, better positioning of the glenoid component, reduced implant loosening and scapular notching, and does not compromise the deltoid, which is the important motor of the shoulder. This approach tenotomises the subscapularis or osteotomizes the lesser tuberosity. Failure (observed in 45% of cases, Collin, unpublished data) and dysfunction of the repaired subscapularis remains a concern after both tenotomy and lesser tuberosity osteotomy despite multiple variations in subscapularis takedown and reattachment techniques. Neurologic atrophy and fatty infiltration of the subscapularis muscle belly have been also reported to causes pain and impaired function.

===Surgical technique===
The deltopectoral approach consisted of a 10 to 15 cm skin incision being made from the coracoid process toward the deltoid insertion. The infraclavicular fossa (Mohrenheim fossa) is found, the cephalic vein identified and the consistent medial branches, which give the appearance of the Mercedes Benz symbol, are ligated. A self-retaining retractor is used to maintain exposure between the deltoid and pectoralis major. The subacromial bursa was resected to allow placement of a Hohmann retractor under the deltoid over the top of the coracoid process. The arm was abducted and internally rotated. The subacromial bursa is resected to allow placement of a Brown-Deltoid retractor.

====Subscapularis Tenotomy====
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====Osteotomy of the Lesser Tuberosity====
The osteotomy is initiated at the bicipital groove with a 2-mm saw blade and then completed with a curved osteotome. An approximately 2.5 cm2 in the coronal plane and 5 mm thick fleck of lesser tuberosity is taken such that the osteotomy entered the joint medially without violating the humeral head.<ref>Giuseffi SA, Wongtriratanachai P, Omae H, Cil A, Zobitz ME, An KN, Sperling JW, Steinmann SP. Biomechanical comparison of lesser tuberosity osteotomy versus subscapularis tenotomy in total shoulder arthroplasty. J Shoulder Elbow Surg 2012;21:1087-95.</ref><ref>Ponce BA, Ahluwalia RS, Mazzocca AD, Gobezie RG, Warner JJ, Millett PJ. Biomechanical and clinical evaluation of a novel lesser tuberosity repair technique in total shoulder arthroplasty. J Bone Joint Surg Am 2005;87(Suppl 2):1-8</ref>

A complete release of the subscapularis tendon is then performed and the tendon is pushed in the subscapularis fossa. A glenoid retractor is placed anteriorly. The humeral head is resected with a guide or a free-handed anatomic cut respecting native humeral head version and inclination.

====Subscapularis Repair====
The healing rate of the subscapularis following reverse shoulder arthroplasty is only 52.6%.<ref name=":0">Collin P, Rol M, Muniandy M, Gain S, Lädermann A, Ode G. Relationship between postoperative integrity of subscapularis tendon and functional outcome in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2021;30;S1058-2746(21)00523-1</ref> Internal rotation function in patients with an intact subscapularis at two years after reverse shoulder arthroplasty is significantly better than in patients with failed or absent tendon repairs. Primary repair of reparable subscapularis tendons during reverse shoulder arthroplasty should be thus strongly considered.<ref name=":0" />

====Lesser Osteotomy Repair====
Before placement of the humeral stem, two holes are created with a 2-mm drill bit in the bicipital groove at the superior and inferior aspects of the lesser tuberosity osteotomy. One hole was created in the metaphysis just medial to the lesser tuberosity osteotomy. The sutures are then passed from lateral to medial by entering the bicipital groove, passing around the humeral stem, and exiting medially (Figure). A racking hitch is positioned to rest in the bicipital groove. The two sutures are passed through the subscapularis just medial to the lesser tuberosity osteotomy. The needle is removed from each construct to leave two superior and two inferior limbs (Figure). Then, one of the superior limbs and one of the inferior limbs were shuttled through the superior racking hitch knot (Figure). The suture limbs are passed through a tensioner to remove slack and to tension the repair (Figure).

{| class="wikitable"
|-
|[[File:Capture d’écran 2020-03-28 à 08.56.41.png|thumb|Passage of the sutures. A suture with a half racking suture on the end is passed from lateral to medial through the inferior two holes, and (B) a separate suture is passed through the superior hole.]]
|[[File:Capture d’écran 2020-03-28 à 08.57.27.png|thumb|Passage of the sutures through the subscapularis and needle removal. The stem is placed so that the sutures pass around the prosthesis. (A) The sutures are passed through the subscapularis tendon, and (B) the wedged ends are cut to provide access to four free limbs.]]
|-
|[[File:Capture d’écran 2020-03-28 à 08.58.02.png|thumb|Passage of the sutures through the knots. (A) One suture limb from each pair is selected and (B) passed through the half racking suture.]]
|[[File:Capture d’écran 2020-03-28 à 08.58.27.png|thumb|Tensioning of the sutures. The suture limbs passed through the half racking suture are tensioned. Tensioning is done under visual inspection.]]
|}

==Anterosuperior (Transdeltoid) Approach==
Molé et al. reported superolateral approach that has the main advantage of better post-operative stability, because the anterior structures, including ligament complexes, are preserved.<ref>Molé D, Wein F, Dézaly C, Valenti P, Sirveaux F. Surgical technique: the anterosuperior approach for reverse shoulder arthroplasty. Clin Orthop Relat Res. 2011 Sep;469(9):2461-8</ref> This approach is different from the transacromial approach originally described by Grammont and Baulot<ref name=":35">Grammont PM, Baulot E. Delta shoulder prosthesis for rotator cuff rupture. Orthopedics 1993;16:65-8</ref> and the anterosuperior approach described by Mackenzie.<ref>Mackenzie D. The antero-superior exposure for total shoulder replacement. Orthop Traumatol 1993;2:71-7</ref> While this technique has shown good results, it involves splitting of the deltoid muscle with the risk of weakening of the anterior deltoid (mechanical or neurologic by damage to the distal branches of axillary nerve) and improper postoperative function.

===Surgical technique===
The skin incision extends from the posterior part of the acromioclavicular joint. It is 9 cm long and runs along the axis of the arm. The surgeon dissociates the anterior deltoid fibers and positions a stop suture on the distal portion of the dissociation to prevent any injury of the axillary nerve. The deltoid muscle fibers are divided to open and excise the subacromial bursa and the anterior deltoid from the anterior edge of the acromion and takes away the proximal attachment of the coracoacromial ligament as one piece. The humeral head osteotomy should be generous to allow optimal exposure of the glenoid. Glenoid exposure is completed, labrum is resected, and peripheral capsular release performed. The inferior labrum is carefully released with a knife while maintaining contact with the bony rim and avoiding electric cautery, considering the proximity of the axillary nerve, which is not visualized. This allows the positioning of a hooked retractor that presses the humeral epiphysis, which is protected by a trial humeral prosthesis. Once the glenoid implant is in place, the surgeon subluxates the humerus superiorly and anteriorly and cuffs the trial humeral stem with a trial insert; the reduction enables the surgeon to test the stability and tension. At the end of surgery, the deltoid is closed using laterolateral sutures.

==Deltoid and Subscapularis Sparing Approach (Subscapularis On)==
Indications for subscapularis-on approach were all types of primary reverse shoulder with an intact subscapularis.

[[File:SSc sparing reduit.mp4|thumb|center|Illustrates a right subscapularis-on RSA with superior glenoid erosion.]]

===Surgical technique===
The skin incision extends from the tip of the coracoid process and runs along the axis of the arm. A deltopectoral approach is performed (please refer to deltopectoral approach). After excision of the bursa, the surgeon explores the cuff through rotator interval. Once an intact subscapularis is confirmed, deep dissection is carried out either through the supraspinatus tear or after detaching it. With the arm held in extension and adduction, two long blunt-tipped Hohmann retractors are placed around the humeral head, allowing clear exposure of the proximal humerus (Figure).

[[File:Fig 2.jpg|thumb|center|Illustration: With the arm held in extension and adduction, two long broad-tipped Hohmann retractors are placed around the humeral head, retracting the subscapularis and the remnant posterior rotator cuff, allowing clear exposure of the humeral head.]]

The humerus is prepared to accommodate a stem. After a retroversion guide placement, the level of the humeral head osteotomy is marked with an electrocautery device (Figure), and a free-hand osteotomy is performed. The humeral head osteotomy should be generous to allow optimal exposure of the glenoid.

[[File:Fig 3.jpg|thumb|center|A 20 degrees retroversion guide is placed and the level of the osteotomy is marked on the humeral head with an electrocautery device.]]

The humeral shaft is then prepared (Figure).

[[File:Fig 4.jpg|thumb|center|Following humeral head removal, preparation of the humeral shaft is completed using only compactors.]]

If the initial osteotomy is too shallow or the inclination is suboptimal, it is then revised to maximize the anatomic fit between the prosthesis and the bone. After preparing the humerus, a trial humeral prosthesis is inserted in humeral canal to protect the humeral epiphysis during glenoid preparation. Cartilage removal, labrum resection, and peripheral capsular release are then completed sequentially. Tight inferior glenohumeral ligaments, which may prevent adequate exposure of the glenoid or post-operative shoulder mobility, are released using an electrocautery device with close contact with the inferior glenoid rim. A forked retractor is then inserted inferiorly to maintain visualization and accessibility to the glenoid (Figure).

[[File:Fig 5.jpg|thumb|center|A forked retractor is placed inferior to the glenoid to maintain visualization and accessibility. The glenoid is prepared according to the recommended surgical technique to obtain neutral inclination and version.]]

This maneuver pushes the humeral epiphysis inferiorly or antero-inferiorly (compared to standard deltopectoral approach in which the humeral head is dislocated posteriorly) for better visualization of the glenoid. The glenoid is prepared according to the recommended surgical technique to obtain neutral inclination and version. Preoperative planning software is used to determine the amount of inferior tilt and whether an augmented baseplate is required. The baseplate is secured onto the glenoid with non-locking and locking peripheral screws. An eccentric 36 or 39 mm glenosphere is used to limit impingement in adduction, extension and external rotation. It is not recommended implanting a larger glenosphere as the excessive lateralization may hinder access to the humerus. The glenosphere is impacted into the baseplate. Once the glenoid implant is in place, the surgeon subluxs the humerus superiorly and anteriorly. A stem is inserted. The shoulder is reduced via gentle traction on the arm and range of motion tested in all planes to ensure stability and confirm the prosthesis moves easily without impingement. The prothesis is then dislocated for final implantation of a definitive polyethylene. Osteophytes are removed and lateral tuberoplasty can be performed to maximize flexibility and avoid bony impingement. The surgical incision measures about 7 to 10 cm (Figure).

[[File:Fig 6 améliorée.jpg|thumb|center|Length of the surgical incision.]]

===Postoperative Rehabilitation===
By using this subscapularis-on approach, patients do not require any immobilization with a sling following the operation. Immediate active motion in all planes is allowed post-operatively.

===Complications===
Tuberosity avulsions that require suture cerclage can bee observed (Figure).

[[File:Figure 8.jpg|thumb|center|A) Example of tuberosity avulsions (black arrows) requiring 3 suture cerclages. B) Tuberosity healing was observed at two-year follow-up. ]]

===Advantages of Subscapularis-on Approach===
There are several reasons why the integrity of the subscapularis tendon should be maintained when performing a reverse shoulder arthroplasty. First, acute muscle lengthening related to the non-anatomic design of the prosthesis plays a role. The muscle lengthening occurs mainly in the supraspinatus (19 mm with a bony increased offset reverse shoulder arthroplasty (BIO-RSA) implant), followed by the upper part of the subscapularis, which accounts for 70% or more of the strength and function of the subscapular muscle-tendon unit. Muscle lengthening could theoretically make reinsertion of the subscapularis more challenging, particularly with lateral offset designs.
Secondly, the inferior part of the subscapularis has no tendon macroscopically; the muscle attaches directly to the bone, making reinsertion difficult. Healing rate is consequently low, at around 55%. Thirdly, the subscapularis is described as being the largest muscle in the rotator cuff and stronger (53% of global strength of the rotator cuff) than the supraspinatus, infraspinatus and teres minor combined.<ref name=":33">Keating JF, Waterworth P, Shaw-Dunn J, Crossan J. The relative strengths of the rotator cuff muscles. A cadaver study. J Bone Joint Surg Br 1993;75:137-40</ref> If a muscle has to be divided, it seems logical to sacrifice the supraspinatus that accounts for only 14% of the global strength.<ref name=":33" /> Fourth, the subscapularis plays a crucial role in anterior elevation. Collin et al. previously demonstrated that the subscapularis is the most important rotator cuff muscle for elevation in native shoulders.<ref>Collin P, Matsumura N, Lädermann A, Denard PJ, Walch G. Relationship between massive chronic rotator cuff tear pattern and loss of active shoulder range of motion. J Shoulder Elbow Surg 2014;23:1195-202</ref>

===Disadvantages of Subscapularis-on Approach===
The main disadvantage of the subscapularis-on technique is limited surgical exposure. Even though specialized jigs were not required for the above-mentioned technique, the development of specifically-designed instrumentation for this procedure seems necessary. Moreover, limited exposure prevents the use of patient-specific surgical guides. Development of less invasive guides or navigation systems may become inevitable in the future. Even if good exposure of the humeral head is achieved, the free-hand humeral osteotomy can be problematic. Subscapularis-on approach is technically challenging in certain cases (e.g. stiff shoulders, small patients) and may not be practical or possible in all circumstances. Intra-operatively, important lateralization (> 5 mm) of the glenoid is impossible, as subsequent exposure of the humerus is insufficient to implant the stem.

=Specific Conditions=
==Reverse Shoulder Arthroplasty in Patients with Preoperative Deltoid Impairment==
===Definition, Causes, and Classification of Deltoid Impairment===
The deltoid is critical for shoulder motion and any pathology involving this muscle is highly detrimental to normal glenohumeral function. It generates over 50% of the force necessary to elevate the arm in scapula plane in a normal shoulder and is the only muscle remaining to provide an abduction moment in patients with massive rotator cuff tears.<ref>Bianchi S, Martinoli C, Abdelwahab IF. Imaging findings of spontaneous detachment of the deltoid muscle as a complication of massive rotator cuff tear. Skeletal radiology 2006;35:410-5</ref> Deltoid impairment is defined as any condition which compromise its physiological function. Such impairment may be permanent or transient and can occur from a variety of conditions.

The deltoid muscle may be shortened upon itself and lose function by disruption of normal length-tension relationships (Figure).

[[File:Image21-57.jpg|thumb|center|Proximal migration of the humeral head leads to a lack of deltoid tension.]]

Effectively, as the Blix curve describes, maintenance of length is required for a muscle to generate adequate tension.<ref>Blix M. Die lange und dle spannung des muskels. Skand Arch Physiol 1891:295-318</ref> Therefore shortening either by proximal migration of the deltoid insertion (rotator cuff arthropathy) or distal migration of the origin (scapular spine fracture) will compromise deltoid function. Proximal migration in particular can be considered a transient cause of deltoid impairment since it can be treated with reverse shoulder arthroplasty. Distal migration, on the other hand, may be permanent or transient depending on the situation.

In the most severe conditions, part or all of the deltoid muscle may be completely absent. Such permanent impairment is rare but may be observed following deltoid muscular flap transfer (for irreparable rotator cuff tears, Figure)<ref>Gazielly D. The deltoid flap procedure. Tech Shoulder Elbow Surg 2000:117–27</ref><ref name=":42">Glanzmann MC, Flury M, Simmen BR. Reverse shoulder arthroplasty as salvage procedure after deltoid muscle flap transfer for irreparable rotator cuff tear: a case report. J Shoulder Elbow Surg 2009;18:e1-2</ref><ref name=":20">Tay AK, Collin P. Irreparable spontaneous deltoid rupture in rotator cuff arthropathy: the use of a reverse total shoulder replacement. J Shoulder Elbow Surg 2011;20:e5-8</ref> or following tumor resection (Figure).

[[File:Image22-59.jpg|thumb|center| Status after a left deltoid muscular flap transfer for irreparable rotator cuff tears. A: Schematic drawing of the surgical technique (with permission of Gazielly D.). B: Frontal magnetic resonance imaging demonstrates absence of the deltoid muscle laterally. C. Clinical photo demonstrating atrophy of the anterior and middle deltoid.]]

[[File:Image23-61.jpg|thumb|center|A: Intraoperative view of a left anterior deltoid resection in the context of proximal humerus neoplasm. Isolation of the anterior deltoid through which an open biopsy had previously been performed. B: Resection of the entire anterior deltoid and proximal humerus. C: Intraoperative view following implantation of a reverse shoulder arthroplasty. D: Postoperative anterior-posterior radiograph.]]

One of the most common forms of deltoid impairment seen clinically is disruption of the muscle origin (without removal of the entire muscle belly). This most commonly occurs in the postsurgical setting after an open rotator cuff repair in which a deltoid split approach is used and part of the deltoid origin is take-down to gain exposure (Figure).<ref>Sher JS, Iannotti JP, Warner JJ, Groff Y, Williams GR. Surgical treatment of postoperative deltoid origin disruption. Clin Orthop Relat Res 1997:93-8</ref>

[[File:Image24-63.jpg|thumb|center|Sequelae of a right open rotator cuff repair involving violation of the deltoid insertion. A: clinical appearance with an anterior deltoid with severe atrophy. B: Anterior-posterior radiograph demonstrating rotator cuff arthropathy. C: Postoperative anterior-posterior view of the reverse shoulder arthroplasty. D and E: Coronal and sagittal views of postoperative anterior forward elevation.]]

Failure of the deltoid to heal back to the acromion can easily be appreciated clinically by a defect to palpation. Additionally, deltoid insertion disruption can occur through chronic attritional rupture as in chronic rotator cuff arthropathy with anterosuperior escape,<ref>Blazar PE, Williams GR, Iannotti JP. Spontaneous detachment of the deltoid muscle origin. J Shoulder Elbow Surg 1998;7:389-92</ref><ref>Morisawa K, Yamashita K, Asami A, Nishikawa H, Watanabe H. Spontaneous rupture of the deltoid muscle associated with massive tearing of the rotator cuff. J Shoulder Elbow Surg 1997;6:556-8</ref> or following trauma (Figure).<ref>Chiba D, Sano H, Nakajo S, Fujii F. Traumatic deltoid rupture caused by seatbelt during a traffic accident: a case report. Journal of orthopaedic surgery 2008;16:127-9</ref><ref>Lin JT, Nagler W. Partial tear of the posterior deltoid muscle in an elderly woman. Clinical journal of sport medicine : official journal of the Canadian Academy of Sport Medicine 2003;13:120-1</ref>

[[File:Image25-65.jpg|thumb|center|Evaluation in an acute phase of left posterior deltoid insertion disruption on T2 weighted fat saturated magnetic resonance imaging (MRI) arthrogram sagittal sequences revealed an edema (red arrows) propagating into the muscle.]]

The deltoid muscle may be globally impaired in the setting of persistent denervation,<ref>Wilbourn AJ, Aminoff MJ. AAEM minimonograph 32: the electrodiagnostic examination in patients with radiculopathies. American Association of Electrodiagnostic Medicine. Muscle Nerve 1998:1612-31</ref> grade 3 or 4 fatty infiltration,<ref>Goutallier D, Postel JM, Bernageau J, Lavau L, Voisin MC. Fatty muscle degeneration in cuff ruptures. Pre- and postoperative evaluation by CT scan. Clin Orthop Relat Res 1994:78-83</ref> previous surgical approach, trauma (Figure), post radiation syndrome, or myopathy (myositis, Parkinson, Duchenne muscular dystrophy, etc.).<ref>Moser T, Lecours J, Michaud J, Bureau NJ, Guillin R, Cardinal E. The deltoid, a forgotten muscle of the shoulder. Skeletal radiology 2013;42:1361-75</ref>

[[File:Image29-73.jpg|thumb|Preoperative (A, anterior-posterior and B, lateral scapular views) and post reverse shoulder arthroplasty (C anterior-posterior view) of a right shoulder after a gunshot in a patient that presented post-traumatically with global neurological impairment including the axillary nerve.]]

Once the etiology is determined, the deltoid impairment should be then classified according to its location and extent. Lädermann et al.<ref name=":23">Lädermann A, Walch G, Denard PJ, Collin P, Sirveaux F, Favard L, Edwards TB, Kherad O, Boileau P. Reverse shoulder arthroplasty in patients with pre-operative impairment of the deltoid muscle. The bone & joint journal 2013;95-B:1106-13</ref> proposed a classification for deltoid impairment based on location: type 1 corresponds to an impairment localized anteriorly, type 2 an anterior and middle one, type 3 involves only the middle deltoid, and type 4 is a global impairment (Figure). As discussed subsequently, this classification related to prognosis with type 4 in particular having a poorer function following reverse shoulder arthroplasty.

[[File:Classification atteinte deltoid.jpg|thumb|center|Deltoid impairment based on location: type 1 corresponds to an impairment localized anteriorly, type 2 an anterior and middle one, type 3 involves only the middle deltoid, and type 4 is a global impairment. ]]

====Results====
Glanzmann et al. first published a case report of the results of a reverse shoulder arthroplasty after deltoid muscle flap transfer.<ref name=":42" /> At two years follow-up, the patient was satisfied and had a Constant score of 62 points, suggesting that the entire deltoid may not be necessary for a successful outcome. Tay and Collin also described successful results of a reverse shoulder arthroplasty implanted in the setting of an irreparable rupture of the middle portion of the deltoid muscle.<ref name=":20" /> No intra- or postoperative complication was noticed. At two years follow-up, the patient was pain free, had active anterior elevation of 150 degrees, and the Constant score was 65 points. Gulotta et al. reported in their biomechanical study that scapular plane elevation may still be possible following a reverse shoulder arthroplasty in the setting of anterior deltoid deficiency. When the anterior deltoid is deficient, there is a compensatory increase in the force required by the subscapularis and middle deltoid.<ref>Gulotta LV, Choi D, Marinello P, Wright T, Cordasco FA, Craig EV, Warren RF. Anterior deltoid deficiency in reverse total shoulder replacement: a biomechanical study with cadavers. J Bone Joint Surg Br 2012;94:1666-9</ref> In this condition, surgeons should focus on preserving the subscapularis as much as possible during approach of reverse shoulder arthroplasty. Whatley et al. reported three cases who had postoperative rupture of the anterolateral deltoid following failed mini-open or open rotator cuff repairs. Successful repair of the deltoid was achieved using a transosseous suture repair in all three patients.<ref>Whatley AN, Fowler RL, Warner JJ, Higgins LD. Postoperative rupture of the anterolateral deltoid muscle following reverse total shoulder arthroplasty in patients who have undergone open rotator cuff repair. J Shoulder Elbow Surg 2011;20:114-22</ref> Essilfie et al. presented a case with deltoid failure after anatomical total shoulder arthroplasty revised with reverse shoulder arthroplasty. His ASES score after reverse shoulder arthroplasty was better than historical outcomes for resection arthroplasty and glenohumeral arthrodesis.<ref>Essilfie A, McKnight B, Heckmann N, Rick Hatch GF, 3rd, Omid R. Revision reverse total shoulder arthroplasty in a patient with preoperative deltoid insufficiency: a case report. J Shoulder Elbow Surg 2017;26:e232-e5</ref> Lattisimus dorsi muscle transfer can also provide an augmentation in patients with deltoid insufficiency.<ref name=":43">Dosari M, Hameed S, Mukhtar K, Elmhiregh A. Reverse shoulder arthroplasty for deltoid-deficient shoulder following latissimus dorsi flap transfer. Case report. Int J Surg Case Rep 2017;39:256-9</ref><ref>Goel DP, Ross DC, Drosdowech DS. Rotator cuff tear arthropathy and deltoid avulsion treated with reverse total shoulder arthroplasty and latissimus dorsi transfer: case report and review of the literature. J Shoulder Elbow Surg 2012;21:e1-7</ref> Dosari et al. presented a patient with a history of gunshot injury and loss of most of his shoulder bony and muscular structures. Due to deltoid muscle deficiency, the patient underwent lattisimus dorsi muscle flap followed by reverse shoulder arthroplasty with successful result.<ref name=":43" /> Deltoid reconstruction at the same time of reverse shoulder arthroplasty is also a viable choice as a salvage procedure for patients with deltoid deficiency.<ref name=":25">Marinello PG, Amini MH, Peers S, O'Donnell J, Iannotti JP. Reverse total shoulder arthroplasty with combined deltoid reconstruction in patients with anterior and/or middle deltoid tears. J Shoulder Elbow Surg 2016;25:936-41</ref> Marinello suggested if less than 50% of any part of the anterior or middle deltoid was involved (≤3 cm), reattachment or reconstruction was not needed. If all of the anterior and/or middle deltoid were involved, then reattachment or reconstruction was indicated.<ref name=":25" /> In a multicentered study, Lädermann et al. reviewed 49 patients (49 shoulders) at a mean of 38 ± 30 months postoperative following reverse shoulder arthroplasty in the setting of deltoid impairment.<ref name=":23" /> Postoperative complications occurred in nine (18%) patients, including two postoperative dislocations and two acute postoperative neurological lesions. Five (10%) patients required additional surgery. Active forward elevation and Constant score improved significantly. However, these values are significantly lower for patients suffering from global deltoid impairment (type 4) compared to types 1 through 3. The mean postoperative forward elevation was lower in the setting of global deltoid impairment (70 degrees) compared to partial impairment (127 degrees, 136 degrees and 125 degrees, groups 1-3 respectively) (P=.002). The postoperative Constant score was lower in the setting of global impairment (41) compared to partial impairment (57, 63 and 68, groups 1-3 respectively) (P=.006). Overall, the rate of patient satisfaction was 98% at final follow-up.<ref name=":23" /> Schneeberger et al. retrospectively reviewed the outcome of 19 patients treated with reverse shoulder arthroplasty after failed deltoid flap reconstruction.<ref>Schneeberger AG, Muller TM, Steens W, Thur C. Reverse total shoulder arthroplasty after failed deltoid flap reconstruction. Arch Orthop Trauma Surg 2014;134:317-23</ref> They noticed a high rate of complication (37%), including one instability. Nonetheless, at a mean follow-up of 4.5 years, only two patients had moderate to severe pain, all patients regained anterior active elevation above 90 degrees, and 15 of 19 patients were very satisfied.

It seems that the most important factor for postoperative result is the extent of the lesion, and not its cause. Interestingly, patient satisfaction is high in all publications on reverse shoulder arthroplasty in the setting of deltoid impairment. However, this is likely related to very poor preoperative function and moderate preoperative expectations of this population.

==Acromial Insufficiency==
Pre- or postoperative acromial pathology, which could theoretically compromise deltoid condition and affect the proper function of the prosthesis, is of legitimate concern.

===Preoperative===
Postoperative fractures occur at least in 3% of cases and their causes are numerous. Preoperatively, the acromion may be subject to a congenital or acquired abnormality such as an os acromiale. It can also already be eroded, fragmented or even fractured from the underlying head in case of cuff tear arthropathy (Figure), or osteoporosis-induced insufficiency.

[[File:Image37-89.jpg|thumb|center|Preoperative insufficiency of a left acromion on an anteroposterior view. Note that a large part of the acromion just seems to have disappeared.]]

[[File:Bouvier.jpg|thumb|center|Preoperative spine fracture in a patient suffering from rotator cuff arthropathy with severe Glenoid bone loss.]]

===Postoperative===
It has been suggested that these fractures may be the result of a stress coming from the tip of the superior metaglene fixation screw.<ref name=":34">Crosby LA, Hamilton A, Twiss T. Scapula fractures after reverse total shoulder arthroplasty: classification and treatment. Clin Orthop Relat Res 2011;469:2544-9</ref> Another risk factor is osteoporosis<ref>Otto RJ, Virani NA, Levy JC, Nigro PT, Cuff DJ, Frankle MA. Scapular fractures after reverse shoulder arthroplasty: evaluation of risk factors and the reliability of a proposed classification. J Shoulder Elbow Surg. 2013 Nov;22(11):1514-21</ref><ref name=":24">Schenk P, Aichmair A, Beeler S, Ernstbrunner L, Meyer DC, Gerber C. Acromial Fractures Following Reverse Total Shoulder Arthroplasty: A Cohort Controlled Analysis. Orthopedics. 2020 Jan 1;43(1):15-22</ref> The role of prosthetic design, distalization, global lateralization and Glenoid medicalization is still debated.<ref name=":24" /><ref>Wong MT, Langohr GDG, Athwal GS, Johnson JA. Implant positioning in reverse shoulder arthroplasty has an impact on acromial stresses. J Shoulder Elbow Surg. 2016 Nov;25(11):1889-1895</ref>

Acromial fractures can be classified as avulsion fractures of the anterior acromion (Type I), fractures of the acromion posterior to the acromioclavicular joint (Type II) and fractures of the scapular spine (Type III).<ref name=":34" />

The symptomatology usually appears within the first year with sudden pain and decrease of function. The localization of the former is typically posterior. The fracture is best seen on an axillary lateral view to differentiate acromial fracture from scapular spine fracture (Figure).

[[File:Acromial fracture.png|thumb|center|Postoperative anteroposterior X-ray demonstrate an acromial fracture.]]

The use of positron emission tomography-computed tomography is helpful in diagnosis of non-displaced fractures.

[[File:SPECT CT acromial fracture.png|thumb|center|SPECT CT of a left shoulder after a reverse shoulder arthroplasty. The patient developed pain 6 months after surgery. X-ray did not revealed fracture. SCPECT CT clearly demonstrated a hypersignal on the acromion.]]

Good results have surprisingly been reported in patients with preoperative acquired or congenital acromial pathology or postoperative acromial fracture.<ref>Mottier F, Wall B, Nove-Josserand L, Galoisy Guibal L, Walch G. [Reverse prosthesis and os acromiale or acromion stress fracture]. Rev Chir Orthop Reparatrice Appar Mot 2007;93:133-41</ref> This can be explained by the persistent attachment of the deltoid to the spine of the scapula and clavicle and the more predominant postoperative scapulothoracic motion compared to the glenohumeral one. In case of postoperative acromial or scapular fractures, results are usually disappointing.<ref>Neyton L, Erickson J, Ascione F, Bugelli G, Lunini E, Walch G. Grammont Award 2018: Scapular fractures in reverse shoulder arthroplasty (Grammont style): prevalence, functional, and radiographic results with minimum 5-year follow-up. J Shoulder Elbow Surg. 2019 Feb;28(2):260-267</ref>

The best treatment option for acromial fractures is thus conservative, as it does not lead to major shoulder dysfunction. Outcome of scapular spine fractures are more unpredictable with displacement of the bony support for the entire deltoid, pain and dysfunction. Consequently, some authors recommend open reduction, internal fixation and allograft associated with postoperative immobilization on a 60° abduction splint in order to avoid nonunion and acromiohumeral contact secondary to inferior acromial tilt.<ref name=":34" />

==Latissimus Dorsi Transfert in Combination with the Reverse Shoulder Arthroplasty==
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==Reverse Shoulder Arthroplasty in Weight Bearing Patients==
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=Results=
With a mean anterior forward flexion of 137 degrees and a mean external rotation elbow at the side of 6 degrees, reverse shoulder arthroplasty typically provides satisfactory clinical outcomes for a variety of complex shoulder diagnoses associated with severe pain and limitation of range of motion.<ref name=":26">Wall B, Nove-Josserand L, O'Connor DP, Edwards TB, Walch G. Reverse total shoulder arthroplasty: a review of results according to etiology. J Bone Joint Surg Am 2007;89:1476-85</ref> However, some patients have had unexpectedly poor functional improvements after reverse shoulder arthroplasty.<ref name=":26" /> Poor postoperative range of motion following reverse shoulder arthroplasty, has been associated with younger age,<ref name=":44">Hartzler RU, Steen BM, Hussey MM, Cusick MC, Cottrell BJ, Clark RE, Frankle MA. Reverse shoulder arthroplasty for massive rotator cuff tear: risk factors for poor functional improvement. J Shoulder Elbow Surg 2015;24:1698-706</ref> gender,<ref name=":45">Schwartz DG, Cottrell BJ, Teusink MJ, Clark RE, Downes KL, Tannenbaum RS, Frankle MA. Factors that predict postoperative motion in patients treated with reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2014 Sep;23(9):1289-95</ref> surgeon experience,<ref>Walch G, Bacle G, Lädermann A, Nové-Josserand L, Smithers CJ. Do the indications, results, and complications of reverse shoulder arthroplasty change with surgeon's experience? J Shoulder Elbow Surg. 2012 Nov;21(11):1470-7</ref> preoperative diagnosis such as posttraumatic arthritis and revision arthroplasty,<ref>Cuff D, Pupello D, Virani N, Levy J, Frankle M. Reverse shoulder arthroplasty for the treatment of rotator cuff deficiency. J Bone Joint Surg Am 2008;90:1244-51.</ref><ref name=":26" /> pre- and intraoperative range of motion or deltoid impairment,<ref name=":23" /><ref name=":45" /> postoperative arm lengthening<ref name=":32" /><ref>Lädermann A, Lubbeke A, Collin P, Edwards TB, Sirveaux F, Walch G. Influence of surgical approach on functional outcome in reverse shoulder arthroplasty. Orthopaedics & traumatology, surgery & research : OTSR 2011;97:579-82</ref><ref name=":30" /> or neurological lesion.<ref name=":44" /><ref name=":46">Lädermann A, Lübbeke A, Mélis B, Stern R, Christofilopoulos P, Bacle G, Walch G. Prevalence of neurologic lesions after total shoulder arthroplasty. J Bone Joint Surg Am 2011;93:1288-93</ref> Surgery of the non-dominant side, lower preoperative range of motion, and lower functional outcome scores preoperatively are predictive of a slower recovery of active anterior forward flexion after reverse shoulder arthroplasty.<ref>Collin P, Matsukawa T, Denard PJ, Gain S, Lädermann A.Pre-operative factors influence the recovery of range of motion following reverse shoulder arthroplasty. Int Orthop. 2017 Oct;41(10):2135-2142</ref>

=Complications=
The first series of reverse shoulder arthroplasty with an at least two years follow-up, confirmed the preliminary results with excellent functional outcome and stable glenoid fixation.<ref name=":36" /> Beck S, Patsalis T, Busch A, Dittrich F, Dudda M, Jäger M, Wegner A. A substantial and durable improvement in the long term has been reported.<ref>Beck S, Patsalis T, Busch A, Dittrich F, Dudda M, Jäger M, Wegner A. Long-term results of the reverse Total Evolutive Shoulder System (TESS). Arch Orthop Trauma Surg. 2019 Aug;139(8):1039-1044</ref><ref>Ernstbrunner L, Rahm S, Suter A, Imam MA, Catanzaro S, Grubhofer F, Gerber C. Salvage reverse total shoulder arthroplasty for failed operative treatment of proximal humeral fractures in patients younger than 60 years: long-term results. J Shoulder Elbow Surg. 2019 Oct 6. pii: S1058-2746(19)30537-3.</ref><ref>van Ochten JHM, van der Pluijm M, Pouw M, Felsch QTM, Heesterbeek P, de Vos MJ. Long - Term survivorship and clinical and radiological follow - up of the primary uncemented Delta III reverse shoulder prosthesis. J Orthop. 2019 Mar 24;16(4):342-346</ref> However, the complexity of this procedure with regards to its singular anatomy and special patient population, is reflected by the large number of reported problems and complications. As defined by Zumstein et al., problems can be defined as intra- or postoperative events that are not likely to affect the patient’s final outcome.<ref name=":19">Zumstein MA1, Pinedo M, Old J, Boileau P. Problems, complications, reoperations, and revisions in reverse total shoulder arthroplasty: a systematic review. J Shoulder Elbow Surg. 2011 Jan;20(1):146-57</ref> This will include hematomas, phlebitis, heterotopic ossification, algodystrophy and will not be part of the treated subjects of this thesis. Complications are defined as any intra- or postoperative events that are likely to have a negative influence on the patient’s final outcome, such as intraoperative cement extravasation, intra- or postoperative fractures, dislocations, infections, neurological lesions, radiographic changes such as glenoid or humeral lucent lines, scapular notching, stress shielding, aseptic loosening, reinterventions (without replacement of the component) or revisions (with replacement of the component).

==Radiological Changes==
This is the most frequently reported complication after reverse shoulder arthroplasty.<ref name=":19" /> Long-term studies reported their prevalence.<ref name=":37" />

===Impingements===
Scapular notching was initially described as the result of an impingement of the prosthetic metaphysis against the scapular neck with the arm in adduction consequent to humerus medialization.<ref>[https://doi.org/10.1302/0301-620x.86b3.14024]</ref> A study by Lädermann et al revealed that two types of impingement interactions coexist, the frank abutment-type impingement (between greater tuberosity and the acromion) and friction-type impingement (anterior, posterior notching and inferior scapular notching) (Fig. 2). Abutment-type impingement seems to restrict movement in abduction and flexion with contact located on the lateral acromion or the coracoid process.<ref name=":2" /> Friction impingements have been shown to be anterior, posterior, and inferior and are due to a combination of many motions, especially of extension and internal or external rotation with the arm at the side.<ref name=":2" /> Inferior scapular notching is the most common scapular notching, thus we refer to it mainly as scapular notching.

====Scapular Notching====
Scapular notching is the most frequent radiographic change after a reverse shoulder arthroplasty and has been reported as high as 88%.<ref name=":37" /> It was initially described as the result of abutment of the prosthetic metaphysis against the scapular neck with the arm in adduction consequent to humerus medialization. Repetitive contact between polyethylene and bone may result in polyethylene wear debris, chronic inflammation and osteolysis,<ref name=":39" /> radiolucency around the glenoid component,<ref>Werner CM, Steinmann PA, Gilbart M, Gerber C. Treatment of painful pseudoparesis due to irreparable rotator cuff dysfunction with the Delta III reverse-ball-and-socket total shoulder prosthesis. J Bone Joint Surg Am 2005;87:1476-86</ref> loosening of the glenoid component,<ref>Cazeneuve JF, Cristofari DJ. Delta III reverse shoulder arthroplasty: radiological outcome for acute complex fractures of the proximal humerus in elderly patients. OOrthop Traumatol Surg Res 2009;95:325-9</ref> presence of an inferior bone spur, and ossification in the glenohumeral space.<ref name=":37" />

Scapular notching (Figure) typically occurs within six months after surgery and appears to stabilize in most cases. The use of an anterosuperior approach, a high position of the baseplate on the glenoid and superior tilting have all been associated with higher rates of notching caused by mechanical impingement with the arm in adduction. Eccentric glenospheres with an inferior offset and glenoid components with a more lateral offset (bony or metal) can reduce the risk of notching.<ref name=":11" /><ref name=":3" /> Mizuno et al. analyzed the influence of an eccentric glenosphere in 47 consecutive cases compared with a historical group treated by the same surgeon. The rates of notching were not different but the severity of notching was less when using an eccentric glenosphere.<ref name=":38" /> Other authors have reported a negligible rate of notching when using an inferior offset component.

[[File:Scapular notching.png|thumb|center|Scapular notching. The severe superior glenoid bone loss (left) has not been corrected intraoperatively (middle), resulting in a severe scapular notching of grade 4 according to Sirveaux.]]

Two types of impingement interactions are noted (Figure).

[[File:Image41-97.jpg|thumb|Two types of impingement interactions coexist; it could correspond to a friction of the polyethylene against the bone (Figure A and B). These repetitive frictions might lead with time to progressive bony abrasion. These phenomena are probably the cause of a rapid apparition of scapular notching. They are the results of multiple motions (adduction, rotations, extension) and not the consequence of a simple contact with the pillar in adduction arm at the side as previously believed. Contrarily, some impingements are related to an abutment with no possibilities to either component to continue the movement (Figure C and D). ]]

====Anterior Impingement====
Anterior impingement can also occur in the setting of reverse shoulder arthroplasty. Anterior impingement may specifically jeopardize the clinical outcome and implant survivorship, ranging from limitation in internal rotation to dislocation by decoaptation, or failure.<ref>De Wilde L1, Walch G. Humeral prosthetic failure of reversed total shoulder arthroplasty: a report of three cases. J Shoulder Elbow Surg. 2006 Mar-Apr;15(2):260-4</ref> As the conformation of the joint changes from spinning to hinging in reverse shoulder arthroplasty, implant version of the humeral stem seems to be the most predictive factor for the occurrence anterior scapular notching. Grammont already warned that excessive retroversion led to decreased internal rotation.<ref name=":35" /> The anterior notching mostly occurred in adduction. The best compromise between anterior and posterior notching to favor a functional arc of motion seems to be 20 to 40 degrees of humeral retroversion.<ref>Stephenson DR, Oh JH, McGarry MH, Rick Hatch GF 3rd, Lee TQ. Effect of humeral component version on impingement in reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2011 Jun;20(4):652-8</ref> On the other hand, glenoid component version doesn’t seem to influence notching in the axial plane.<ref>Favre P, Sussmann PS, Gerber C. The effect of component positioning on intrinsic stability of the reverse shoulder arthroplasty. J Shoulder Elbow Surg 2010;19:550–556</ref>

==Infection==
The incidence of infections after primary reverse shoulder arthroplasty is around 5%,<ref name=":5" /> which is higher than in anatomic shoulder arthroplasty.<ref>Fehringer EV, Mikuls TR, Michaud KD, Henderson WG, O'Dell JR. Shoulder arthroplasties have fewer complications than hip or knee arthroplasties in US veterans. Clin Orthop Relat Res 2010;468:717-22</ref><ref>Seebauer L. Total reverse shoulder arthroplasty: European lessons and future trends. Am J Orthop (Belle Mead NJ). 2007 Dec;36(12 Suppl 1):22-8</ref> Reasons are the large dead space caused by the ball-and-socket configuration, the frequent postoperative hematoma, the extensive surgical dissection, and in some patients the compromised general health and the numerous previous surgeries. The commonly identified low-virulence organisms are Cutibacterium acnes and Staphylococcus epidermidis. Proven and suspected infections should be revised operatively. Acute infection of less than three weeks in a stable arthroplasty should be treated with debridement and antibiotics. Late infections should be treated with arthroplasty removal, debridement and reimplantation.

==Instability==

Dislocation is one of the most common complications after reverse shoulder arthroplasty, with rates as high as 14% which account for almost half of the complications in some series. Intraoperative criteria have been proposed by other authors to assess prosthetic stability. The recommendations are numerous and include 1) a prosthesis implantation in such a way that it is difficult to reduce, 2) the absence of pistoning of the prosthesis when applying axial traction on the arm, 3) stability throughout a full range of motion, 4) passive adduction of the arm with elbow at side, 5) palpation of the tension in the conjoint tendon after reduction with the arm at the side and the elbow extended, 6) no asymmetric subluxation or tilting of the proximal humeral component on the glenosphere during adduction, and 7) free glenohumeral motion without scapula-thoracic motion between 0° to 60° of abduction. Most cases of dislocation occur during the first few months after implantation and are a result of a technical error. Risk factors for dislocation include body mass index > 30, male sex, previous surgery, subscapularis deficiency and high neck shaft angle (155 degrees). The etiology of dislocation is multifactorial. It can occur due to 1) deltoid insufficiency, 2) lack of anterior restraints including subscapularis insufficiency, conjoint tendon weakness, and pectoralis major insufficiency, 3) malpositioning of the components, 4) impingement, and 5) infection. Instability is more frequent in cases of revision arthroplasty. Deltoid insufficiency can be caused by preoperative factors or can result from a postoperative lack of deltoid tension, acromion fracture, polyethylene wear, stem subsidence, or postoperative neurological palsy. Lädermann et al. noted a strong correlation (p < 0.0001) between preoperative humeral length and dislocation. Postoperative shortening of the humerus, as compared to preoperative or contralateral humeral length, was observed in all cases of dislocation.<ref name=":30" /> Subscapularis integrity is important if a 155 degrees is used.<ref>Edwards TB, Williams MD, Labriola JE, Elkousy HA, Gartsman GM, O'Connor DP. Subscapularis insufficiency and the risk of shoulder dislocation after reverse shoulder arthroplasty. J Shoulder Elbow Surg 2009;18:892-6</ref><ref>Cheung EV, Sarkissian EJ, Sox-Harris A, Comer GC, Saleh JR, Diaz R, Costouros JG. Instability after reverse total shoulder replacement. J Shoulder Elbow Surg 2011;20:584-90</ref> Low neck shaft angles (145 and 135 degrees) are more stable designs and subscapularis integrity seems less important to prevent instability.

[[File:Instability.jpg|thumb|center|One month after implantation of a reverse shoulder arthroplasty for a proximal humeral fracture. The X-ray revealed a prosthetic dislocation. Electroneuromyography (ENMG) confirmed a severe axonotmesis of the axillary nerve.]]

==Neurological Lesions==
Lengthening of the arm during reverse shoulder arthroplasty, because of its nonanatomic design and/or maneuver of glenohumeral reduction, may be a major factor responsible for the increased prevalence of neurologic injury. Clinically relevant neurological complications involving the brachial plexus or the axillary nerve, however, are rare following reverse shoulder arthroplasty. A prospective study determined the electrodiagnostic occurrence of peripheral nerve lesions following 155 degrees neck shaft angle reverse shoulder arthroplasty.<ref name=":46" /> If one also takes into account subclinical deterioration of preoperative lesions, 63% of patients in this study had postoperative neurologic lesions. However, only 5% of patients had a lesion that was present beyond 6 months postoperative. The rate of postoperative lesions seems lower using low neck shaft angles.<ref>Lowe JT, Lawler SM, Testa EJ, Jawa A. Lateralization of the glenosphere in reverse shoulder arthroplasty decreases arm lengthening and demonstrates comparable risk of nerve injury compared with anatomic arthroplasty: a prospective cohort study. J Shoulder Elbow Surg. 2018 Oct;27(10):1845-1851</ref> It seems consequently that distalization put the nerve at risk and that lateralization is rather protective for the plexus.

==Glenoid or humeral non- or disassembly==
Glenoid or humeral non- or disassembly, and polyethylene disassociation are minor problems and are mainly due to prosthetic design (Figure).

[[File:Glenoid dissociation.png|thumb|center|Glenoid disassembly. Six weeks postoperative anteroposterior, Neer and axial imaging revealing a disassembly of the glenosphere on the metaglene.]]

==Periprothetic fractures==
===Humerus===
Humeral fractures occurred intra- or postoperatively.

====Intraoperative====
Intraoperatively, they can appear in the metaphyseal area (“controlled fracture” according to Walch) and are related to retractor positioning. Humeral diaphyseal fractures occur intraoperatively in case of an incorrect sizing of the component or excessive external rotation during preparation of the glenoid and release. They usually require the use of a longer implant to bypass the fracture line or an open reduction internal fixation (ORIF).

====Postoperative====
Postoperatively, fractures usually result from trauma (Figure). They can be treated either conservatively if the component is stable or they require revision in cases of unstable components.

[[File:Image47-109.jpg|thumb|center|Postoperative fracture under the stem of the prosthesis that has been treated conservatively.]]

[[File:Image49-113.png|thumb|Patient known for a right reverse shoulder arthroplasty that sustained a fall on the ipsilateral elbow. A transverse supracondylar fracture of the distal humerus is noted on lateral view.]]

==Heterotopic ossification==
Heterotopic ossification after reverse shoulder arthroplasty (Figure) is a relatively common finding of unknown clinical importance.

[[File:Heterotopic ossifications.png|thumb|center|Heterotopic ossification after reverse shoulder arthroplasty ]]

=References=
<references />

Anteroinferior Glenohumeral Instability

2021-08-05T16:22:36Z

Marko.nabergoj: text

==Bullet points==

*One of most common shoulder injuries, 1.7% annual rate in general population.

*High recurrence rate that correlates with age at dislocation, up to 80-90% in teenagers (90% chance for recurrence in age <20).

*The stability of the glenohumeral joint depends on soft tissue stabilizers, bone morphology and dynamic stabilizers such as the rotator cuff and long head of the biceps tendon.

*Osseous lesions, either humeral or glenoid, are identified in 95.0%. The risk of failure of arthroscopic treatment is higher if not addressed. A glenoid bony defect of >20-25% is considered "critical" and is biomechanically highly unstable and require bony procedure to restore bone loss (Latarjet, Bristow, other sources of autograft or allograft).

*A Malgaigne (Hill Sachs) defect is a chondral impaction injury in the posterosuperior humeral head secondary to contact with the glenoid rim. It is present in 80% of traumatic dislocations and 25% of traumatic subluxations.

*Axillary nerve injury is most often a transient neurapraxia of the axillary nerve and is present in up to 5% of patients.

*Incidence of associated rotator cuff tears increase with age of 40 (30% at 40, 80% at 60).

*Static glenohumeral stabilizers are the bone, the ligaments, the capsule, the labrum, and the negative pressure. The dynamic ones are the rotator cuff and long head of biceps tendon.

*The labrum contributes to 50% of additional glenoid depth.

*Anterior static shoulder stability with arm in 90 degrees of abduction and external rotation is provided by the anterior band of inferior glenohumeral ligament (main restraint).

*The middle glenohumeral ligament provides static restraint with arm in 45 degrees of abduction and external rotation.

*The superior glenohumeral ligament provides static restraint with arm at the side.

*The physical examination demonstrates instability if the apprehension test is positive, multidirectional hyperlaxity when the external rotation at side is equal or above 85 degrees, and a pathological laxity of the inferior glenohumeral ligament if the hyperabduction test is positive.

*Three views plain radiographs, including true anteroposterior of the glenohumeral joint, scapular Y (scapular lateral), and Velpeau axillary views are the mainstay of imaging in the setting of acute traumatic anterior instability. Plain radiographs including anteroposterior in neutral, internal and external rotations, scapular Y and Bernageau views are obtained for recurrent instability. Magnetic resonance imaging (MRI) arthrogram is useful to assess for labral or rotator cuff tears, computed tomography (CT) for bone loss assessment.

*Conservative treatment after the first traumatic anterior dislocation is recommended for patients who are not actively engaged in sports, above the age of 30 years old, with a low functional demand, with an associated humeral fracture, or for the athlete with an in-season shoulder dislocation.

*Rehabilitation consist of strengthening of dynamic stabilizers (rotator cuff and periscapular musculature), exercises for proprioception and other specific treatments if apprehension persists.

*Surgical treatment included Bankart repair, capsular plication +/- soft tissue procedures (such as remplissage or dynamic anterior stabilization (DAS) if < 20% bone loss.

*If bone loss ≥ 20%, bone reconstruction with Latarjet, Bristow or free bone block transfers such as Eden-Hybinette is recommended.

==Key words==
Anterior glenohumeral instability; anatomy; humerus; scapula; ligaments; shoulder dislocation; subluxation; reduction; bone loss; Malgaigne; Hill-Sachs; Bankart; capsular shift; remplissage; dynamic anterior stabilization (DAS); Latarjet; Bristow; free bone block transfer; Eden-Hybinette; complication; recurrences; therapeutic implications.

==History==
The first recorded depictions of shoulder reduction are ancient.<ref>Iqbal S, Jacobs U, Akhtar A, Macfarlane RJ, Waseem M. A history of shoulder surgery. Open Orthop J 2013;7:305-9.</ref>

Egyptian hieroglyphs dated 3000 years earlier, pictorially depict a leverage method of shoulder manipulation. They have been followed by the Greeks and Romans. Around 400 BC, Hippocrates, the father of Western medicine, introduced the traction method to reduce the shoulder.
<ref>Hussein MK. Kocher's method is 3,000 years old. J Bone Joint Surg Br 1968;50:669-71.</ref><ref>Celsus A. De Medicina.</ref><ref>Hippocrates. Corpus Hippocraticum—De articulis.</ref>

In 1855, Malgaigne was the first one to describe the humeral bone loss also called Hill-Sachs lesion.<ref>Malgaigne J. Traité des fractures et des luxations. Paris: J.-B. Baillière; 1855.</ref>

In the 1890s, the understanding of the unstable shoulder was elucidated by the work of two French researchers, Broca and Hartman who introduced the concept of capsulolabral damage following dislocations as possible cause of recurrent instability. Notably, most of the findings considered current hallmarks of shoulder instability, including Bankart lesion, bony Bankart, Kim lesion, as well as anterior and posterior labral periosteal sleeve avulsions and glenoid avulsions of glenohumeral ligaments, were described in their papers decades before the eponymous figures to whom they are now commonly assigned depicted them.<ref>Broca A, Hartmann H. Contribution à l'étude des luxations de l'épaule (luxations anciennes et luxations récidivantes). Bull Soc Anat 1890;4:416-23.</ref>

In 1906, Perthes in Germany and a few years later, Bankart in the UK ascertained that the detachment of the labrum caused instability of the shoulder and emphasized reattachment of the labrum to stabilize the joint.<ref>Perthes G. Ueber Operationen beihabitueller Schulterluxation. Dtsch Z Chir 1906;85:199–227.</ref><ref>Bankart AS. Recurrent or Habitual Dislocation of the Shoulder-Joint. British medical journal 1923;2:1132-3.</ref>

Current free bone grafting techniques are based on the initial descriptions by Eden in 1918 and Hybinette in 1932 using autologous iliac crest.<ref>Eden R. Zur Operation der habituellen Schulterluxation unter Mitteilung eines neuen Verfahrens bei Abriss am inneren Pfannenrande. Dsch Z Chir 1918;144:269.</ref><ref>Hybinette S. De la transplantation d’un fragment osseux pour remédier aux luxations récidivantes de l’épaule. Acta Chir Scand 1932:411-45.</ref>

Due to donor site morbidity with autologous iliac crest bone grafting techniques, different auto- and allogeneic bone materials have been evaluated as alternatives. Open and arthroscopic approaches using distal clavicle, femoral head, distal tibial allografts or coracoid process are currently used. The first coracoid process transplant was probably realized by the German surgeon Noeske in 1921.<ref>Anonymous. Zentralbl Chir 1924;43:2402.</ref>

Nowadays, two most popular bony procedures included the Latarjet and its variant, the Bristow.<ref name=":1">Latarjet M. Treatment of recurrent dislocation of the shoulder. Lyon Chir 1954;49:994-7.</ref><ref name=":2">Helfet AJ. Coracoid transplantation for recurring dislocation of the shoulder. J Bone Joint Surg Br 1958;40-B:198-202.</ref>

==Anecdote==
(unpublished data, courtesy of Gilles Walch) At the beginning of the 1950s, Albert Trillat, the head of the orthopedic surgical clinic at the Edouard Herriot Hospital in Lyon (France) and also the promoter of the "no-touch technique", reported combination of an anterior labro-ligamentous complex reinsertion when feasible with a reduction of a so-called coraco-glenoid outlet by means of a coracoid osteoclasy and nail fixation (Figures).<ref>Trillat A. Traitement de la luxation récidivante de l'épaule. Considérations techniques. Lyon Chir 1954:986-93.</ref>
[[File:1562526202257-lg.jpg|thumb|500x500px|Postoperative anteroposterior X-ray of a right Trillat.|alt=|left]]
[[File:1562526204072-lg.jpg|alt=|none|thumb|500x500px|The illustrations demonstrate the effect of the procedure that reduce the coraco-glenoid outlet and lower the subscapularis. Courtesy of Gilles Walch.]]
Another surgeon, Michel Latarjet, who was mainly active in the field of thoracic surgery, visited Dr. Trillat to learn the aforementioned technique. When Latarjet supposedly tried to reproduce the Trillat procedure, he carried an involuntary complete coracoid osteotomy. Thenceforth, not knowing what to do with the bony fragment, he fixed it to the anterior glenoid through the subscapularis using a screw. From this mishap was born the operation which now bears his name.<ref name=":1" />

==Anatomical Considerations==
The glenohumeral joint has six degrees of freedom with minimal bony constraint that provides a large functional range of motion. It thus renders this diarthrodial joint particularly vulnerable to instability. The glenohumeral joint is stabilized by dynamic and static structures. The dynamic stabilizers include the rotator cuff, the long head of the biceps, and the deltoid. The static stabilizers of the joint include the capsule, the glenohumeral ligaments, the labrum, the negative pressure within the joint capsule, and the bony congruity of the joint. The superior glenohumeral ligament functions primarily to resist inferior translation and external rotation of the humeral head in the adducted arm. The middle glenohumeral ligament functions primarily to resist external rotation from 0 degree to 90 degrees and provides anterior stability to the moderately abducted shoulder. The inferior glenohumeral ligament is composed of two bands; anterior and posterior, and the intervening capsule. The primary function of the anterior band of the inferior glenohumeral ligament is to resist anteroinferior translation.<ref name=":3">Burkart AC, Debski RE. Anatomy and function of the glenohumeral ligaments in anterior shoulder instability. Clin Orthop Relat Res 2002:32-9.</ref>

==Prevalence==
The glenohumeral joint is the most commonly dislocated large joint of the body, affecting approximately 1.7% of the general population.<ref>Romeo AA, Cohen BS, Carreira DS. Traumatic anterior shoulder instability. Orthop Clin North Am 2001;32:399-409.</ref>

In greater than 90% of cases, the instability is anterior, has a traumatic origin, and occurs in young athletes involved in contact sports.<ref>Goss TP. Anterior glenohumeral instability. Orthopedics 1988;11:87-95.</ref><ref>Owens BD, Agel J, Mountcastle SB, Cameron KL, Nelson BJ. Incidence of glenohumeral instability in collegiate athletics. Am J Sports Med 2009;37:1750-4.</ref>

Ongoing sports participation in this population is associated with a high recurrence rate.<ref>Owens BD, Dickens JF, Kilcoyne KG, Rue JP. Management of mid-season traumatic anterior shoulder instability in athletes. J Am Acad Orthop Surg 2012;20:518-26.</ref>

==Pathoanatomy and biomechanics==
Anterior shoulder instability usually occurs with an anteriorly directed force applied to an abducted and externally rotated arm, or from a direct blow. During an anterior dislocation, many of the passive and active stabilizers may be damaged. The glenoid labrum, the glenohumeral ligaments, and the glenohumeral joint capsule, representing the soft tissue passive stabilizers will be injured; an avulsion of the anterior labrum, the classic Bankart lesion (Figure) or its variations (glenolabral articular disruption (GLAD), Perthes, anterior labroligamentous periosteal sleeve avulsion (ALPSA)) is almost invariably present,11,22,23 although it does not produce instability in isolation.<ref>Bankart AS. Recurrent or Habitual Dislocation of the Shoulder-Joint. British medical journal 1923;2:1132-3.</ref><ref>Neviaser TJ. The anterior labroligamentous periosteal sleeve avulsion lesion: a cause of anterior instability of the shoulder. Arthroscopy 1993;9:17-21.</ref><ref>Neviaser TJ. The GLAD lesion: another cause of anterior shoulder pain. Arthroscopy 1993;9:22-3.</ref><ref>Speer KP, Deng X, Borrero S, Torzilli PA, Altchek DA, Warren RF. Biomechanical evaluation of a simulated Bankart lesion. J Bone Joint Surg Am 1994;76:1819-26.</ref>
[[File:1562526629855-lg.jpg|thumb|600x600px|A) Coronal T2 MRI views of a right shoulder. The white arrow points a Bankart lesion. B) Arthroscopic view of the same lesion from a posterior portal.|alt=]]
The anteroinferior glenohumeral ligaments and the capsule can be detached from the glenoid rim, and a plastic deformation of the glenohumeral ligaments or an HAGL lesion (Figure) are other common features.<ref>Wolf EM, Cheng JC, Dickson K. Humeral avulsion of glenohumeral ligaments as a cause of anterior shoulder instability. Arthroscopy 1995;11:600-7.</ref>
[[File:1562526631138-lg.jpg|thumb|761x761px|Coronal T2 MRI views of a right shoulder. The white arrow points a HAGL lesion. A retensioning of the inferior glenohumeral ligament (capsular shift according to Neer) will be inefficient.|alt=]]
The plastic deformation of these structures becomes progressively more severe with subsequent episodes.<ref>Bigliani LU, Pollock RG, Soslowsky LJ, Flatow EL, Pawluk RJ, Mow VC. Tensile properties of the inferior glenohumeral ligament. J Orthop Res 1992;10:187-97.</ref><ref>Habermeyer P, Gleyze P, Rickert M. Evolution of lesions of the labrum-ligament complex in posttraumatic anterior shoulder instability: a prospective study. J Shoulder Elbow Surg 1999;8:66-74.</ref><ref>Urayama M, Itoi E, Sashi R, Minagawa H, Sato K. Capsular elongation in shoulders with recurrent anterior dislocation. Quantitative assessment with magnetic resonance arthrography. Am J Sports Med 2003;31:64-7.</ref>

The middle glenohumeral ligament functions to limit both anterior and posterior translations of the arm at 45 degrees of abduction and 45 degrees of external rotation whereas the inferior glenohumeral ligament resists translation of the arm in greater degrees of abduction.<ref name=":3" />

In addition to progressive soft tissue injury, recurrent dislocations can facilitate bony injury. Bony lesions are frequent in recurrent cases and may include defects of the glenoid (bony Bankart or beveling of the anterior glenoid resulting in loss of glenoid concavity), impaction of the posterolateral humeral head (Malgaigne lesion), or even coracoid or proximal humerus fractures (Figure).<ref>Griffith JF, Antonio GE, Yung PS, Wong EM, Yu AB, Ahuja AT, Chan KM. Prevalence, pattern, and spectrum of glenoid bone loss in anterior shoulder dislocation: CT analysis of 218 patients. AJR American journal of roentgenology 2008;190:1247-54.</ref><ref>Buscayret F, Edwards TB, Szabo I, Adeleine P, Coudane H, Walch G. Glenohumeral arthrosis in anterior instability before and after surgical treatment: incidence and contributing factors. Am J Sports Med 2004;32:1165-72.</ref><ref>Edwards TB, Boulahia A, Walch G. Radiographic analysis of bone defects in chronic anterior shoulder instability. Arthroscopy 2003;19:732-9.</ref>
[[File:1562527520975-lg.jpg|thumb|600x600px|A) Sagittal view of a CT arthrogram of a left shoulder demonstrates a significant Bankart fracture (white arrow) that produces an “inverted-pear” glenoid. B) Plain anteroposterior radiograph reveals an anteroinferior glenohumeral dislocation with an “engaged” Malgaigne (Hill-Sachs) lesion of the humerus.|alt=]]
Given that the average glenoid diameter is about 24 mm, a 6 mm-wide or larger fragment of the glenoid will typically equate to a 25% or more of the articular surface and is considered a large bony fragment.<ref name=":4">Burkhart SS, De Beer JF. Traumatic glenohumeral bone defects and their relationship to failure of arthroscopic Bankart repairs: significance of the inverted-pear glenoid and the humeral engaging Hill-Sachs lesion. Arthroscopy 2000;16:677-94.</ref><ref>Burkhart SS, Debeer JF, Tehrany AM, Parten PM. Quantifying glenoid bone loss arthroscopically in shoulder instability. Arthroscopy 2002;18:488-91.</ref>

Such significant glenoid bone loss can be viewed arthroscopically as an inverted pear configuration. All Malgaigne lesions are by definition engaging lesions (since it has engaged at least once). Thus, the notion of “engaging” versus “non-engaging” can lead to significant confusion. Some have proposed that the important lesions are those that engage in the 90-90 position.

Finally, the active restraint, mainly a lesion of the rotator cuff above the age of 40, will complete this complex situation.<ref name=":5">Antonio GE, Griffith JF, Yu AB, Yung PS, Chan KM, Ahuja AT. First-time shoulder dislocation: High prevalence of labral injury and age-related differences revealed by MR arthrography. JMRI 2007;26:983-91.</ref><ref>Itoi E, Tabata S. Rotator cuff tears in anterior dislocation of the shoulder. Int orthop 1992;16:240-4.</ref>

The glenohumeral joint is stabilized by a so-called “concavity compression” principle with the rotator cuff pulling the humeral head into the glenoid concavity and therefore ensuring stability through counteracting decentering translational forces.<ref>Lazarus MD, Sidles JA, Harryman DT, 2nd, Matsen FA, 3rd. Effect of a chondral-labral defect on glenoid concavity and glenohumeral stability. A cadaveric model. J Bone Joint Surg Am 1996;78:94-102.</ref><ref>Matsen FA, 3rd, Harryman DT, 2nd, Sidles JA. Mechanics of glenohumeral instability. Clinics in sports medicine 1991;10:783-8.</ref><ref>Yamamoto A, Takagishi K, Osawa T, Yanagawa T, Nakajima D, Shitara H, Kobayashi T. Prevalence and risk factors of a rotator cuff tear in the general population. J Shoulder Elbow Surg 2010;19:116-20.</ref>

==Natural History and Risk Factors of Dislocation or Recurrences==
To understand the natural history of instability and its importance for the appropriate management of this pathology, the following questions should be answered: What happens in the shoulder after the first dislocation? Which structures suffer damage? Who are the patients at higher risk of recurrence? How does the disease evolve without treatment? Will surgical treatment avoid future negative outcomes and prevent degenerative joint disease? Who should we treat and when?<ref>Carpinteiro EP, Barros AA. Natural History of Anterior Shoulder Instability. Open Orthop J. 2017 Aug 31;11:909-918.</ref>

80% of anterior-inferior dislocations occur in young patients. Recurrent instability is common and multiple dislocations are the rule. Instability is influenced by a large number of variables, including age of onset, activity profile, number of episodes,delay between first episode and surgical treatment. The different risks factors are:

-Young males (up to 100% of recurrence),<ref name=":6">Postacchini F, Gumina S, Cinotti G. Anterior shoulder dislocation in adolescents. J Shoulder Elbow Surg 2000;9:470-4.</ref><ref name=":7">Hovelius L, Augustini BG, Fredin H, Johansson O, Norlin R, Thorling J. Primary anterior dislocation of the shoulder in young patients. A ten-year prospective study. J Bone Joint Surg Am 1996;78:1677-84.</ref>

-Practice of contact sports, forced overhead activity,

-Sport practice at a competitive level,<ref name=":8">Balg F, Boileau P. The instability severity index score. A simple pre-operative score to select patients for arthroscopic or open shoulder stabilisation. J Bone Joint Surg Br 2007;89:1470-7.</ref>

-Bony impairment,

-Concomitant hyperlaxity.<ref>Habermeyer P, Jung D, Ebert T. [Treatment strategy in first traumatic anterior dislocation of the shoulder. Plea for a multi-stage concept of preventive initial management]. Der Unfallchirurg 1998;101:328-41.</ref>

==Classification==
Instability can be classified as primary or recurrent. The latter can be further classified as dislocation, subluxation, apprehension, or an unstable painful shoulder. In frank dislocation, the articular surfaced of the joint are completely separated. Subluxation is defined as symptomatic translation of the humeral head on the glenoid without complete separation of the articular surfaces. Apprehension is classically defined by fear of imminent dislocation in the 90-90 position. This could correspond to an instability phenomena or a persistent fear after a successful glenohumeral stabilization (please refer to Apprehension chapter).<ref name=":9">Haller S, Cunningham G, Laedermann A, Hofmeister J, Van De Ville D, Lovblad KO, Hoffmeyer P. Shoulder apprehension impacts large-scale functional brain networks. AJNR American journal of neuroradiology 2014;35:691-7.</ref>

The unstable painful shoulder presents as pain only (as opposed to a sense of instability) during an apprehension maneuver at clinical examination.<ref name=":10">Boileau P, Zumstein M, Balg F, Penington S, Bicknell RT. The unstable painful shoulder (UPS) as a cause of pain from unrecognized anteroinferior instability in the young athlete. J Shoulder Elbow Surg 2011;20:98-106.</ref><ref name=":11">Patte D, Bernageau J, Rodineau J, Gardes JC. [Unstable painful shoulders (author's transl)]. Rev Chir Orthop Reparatrice Appar Mot 1980;66:157-65.</ref>

The majority of these patients has a history of trauma, but simply do not report a clear history of trauma. Careful preoperative and/or arthroscopic examination will show that the majority of these patients also has evidence of instability (i.e. labral tear, glenoid fracture, or Malgaigne (Hill-Sachs) lesion)

Five types of traumatic anterior dislocation have been described. The subcoracoid dislocation has an antero-inferior direction and is the most common. Other types, including subglenoid, subclavicular, retroperitoneal, and intrathoracic are rare and usually associated with severe trauma.<ref>Patel MR, Pardee ML, Singerman RC. Intrathoracic Dislocation of the Head of the Humerus. J Bone Joint Surg Am 1963;45:1712-4.</ref><ref>Wirth MA, Jensen KL, Agarwal A, Curtis RJ, Rockwood CA, Jr. Fracture-dislocation of the proximal part of the humerus with retroperitoneal displacement of the humeral head. A case report. J Bone Joint Surg Am 1997;79:763-6.</ref>

Osseous defects of the anterior glenoid rim can be classified into three types according to their pathomorphology. In particular, acute (type I) and chronic glenoid rim defects (type II and III) are differentiated, which are provoked either by an acute glenoid fracture or recurrent shoulder dislocations with subsequent erosion of the glenoid rim. Type I lesions are further divided into bony Bankart lesions (type Ia), solitary glenoid rim fractures (type Ib) and multifragmented glenoid rim fractures (type Ic). In most cases, type I glenoid defects can sufficiently be reconstructed by mobilization and anatomical refixation of the fragment.

In cases of complex multifragmented glenoid rim fractures (type Ic), however, it may be necessary to resect the fragments and augment the glenoid defect. Type II defects include chronic fragment-type of lesions that are characterized by an extra-anatomically consolidated or pseudarthrotic fragment of insufficient dimensions for a defect reconstruction due to resorption processes. A bony glenoid augmentation may be indicated, depending on the dimensions of the glenoid defect and the remaining fragment. Erosion-type of defects (type III) are predominantly observed in patients with recurrent anterior shoulder dislocations. These usually develop on the basis of a glenoid fracture with subsequent resorption of the fragment, or as a result of chronic abrasion of the anterior glenoid rim. If the bone loss adopts substantial dimensions, mere soft-tissue stabilization procedures are not sufficient in re-establishing stability.

==Clinical Presentation and Essential Physical Examination==
The history should document age, hand dominance, occupation, participation in sporting activities, initial mechanism of the injury, the position of the arm (extension, abduction, and external rotation favors anterior dislocation), how long the shoulder stays out, the method of reduction, the number of recurrences (frank dislocation vs subluxation), and the effectiveness of a previous nonoperative or operative treatment. The diagnosis of recurrent traumatic anterior glenohumeral instability is usually made easily on the basis of the history, radiographs, and a positive apprehension sign. However, when collision athletes are seen, care should be taken because they may not experience clear dislocation or subluxation and only complain of pain or weakness.

A comprehensive physical examination is essential. The aim is to define the direction of instability, the presence of an associated pathologic hyperlaxity, and to exclude neurological and rotator cuff impairment. Passive and active glenohumeral range of motion should be assessed. Rotator cuff examination includes strength tests such as belly-press, bear hug, Jobe tests and strength in external rotation against resistance (please refer to Rotator Cuff Pathology/Rotator cuff complete lesion). Tests for anterior and superior labral lesions are not systematically performed as they have a poor sensitivity and specificity.<ref>Cook C, Beaty S, Kissenberth MJ, Siffri P, Pill SG, Hawkins RJ. Diagnostic accuracy of five orthopedic clinical tests for diagnosis of superior labrum anterior posterior (SLAP) lesions. J Shoulder Elbow Surg 2012;21:13-22.</ref>

The neurovascular status of the upper extremity is assessed, particularly with regard to the axillary nerve since there is a high incidence of injury to this nerve with traumatic instability (Figure).
[[File:1562529745788-lg.jpg|thumb|600x600px|A) A 54-year-old patient sustained a fracture dislocation of the right shoulder. At clinical examination, no peripheral pulse was palpated. B) During open reduction, the axillary artery (white arrows) was found kinked around the fractured humeral head.|alt=|border]]
Laxity is a normal, physiologic and asymptomatic finding, that corresponds to translation of the humeral head in any direction to the glenoid.<ref>Gerber C, Terrier F, Ganz R. The Trillat procedure for recurrent anterior instability of the shoulder. J Bone Joint Surg Br 1988;70:130-4.</ref>

Laxity is assessed with the sulcus sign, anterior-posterior drawer, hyperabduction tests, and external rotation elbow at side. The two former tests are only qualitative and are not routinely performed by the authors. Hyperlaxity is constitutional, multidirectional, bilateral and asymptomatic. Hyperlaxity of the shoulder is probably best defined as external rotation elbow at the side equal or greater than 85 degrees.<ref>Walch G, Agostini JY, Levigne C, Nove-Josserand L. [Recurrent anterior and multidirectional instability of the shoulder]. Rev Chir Orthop Reparatrice Appar Mot 1995;81:682-90.</ref>

This non-pathological finding is a risk factor for instability but does not by itself demand treatment unless there is clear pathological laxity. Pathological laxity of the inferior glenohumeral ligament is observed when passive abduction in neutral rotation in the glenohumeral joint is above 105 degrees, there is apprehension above 90 degrees of abduction, or if a difference of more than 20 degrees between the two shoulders is noted.<ref>Gagey OJ, Gagey N. The hyperabduction test. J Bone Joint Surg Br 2001;83:69-74.</ref><ref name="HoveliusRahme2016Primary">Hovelius L, Rahme H. Primary anterior dislocation of the shoulder: long-term prognosis at the age of 40 years or younger. Knee Surg Sports Traumatol Arthrosc 2016;24:330-42.</ref>

For apprehension the patient is initially invited to demonstrate his or her functional problem to the examiner (no-touch examination). This examination alone, coupled with a good history, often provides the information needed. However, if the direction of the instability remains unclear, the apprehension (crank) test, an abducted and externally rotated position suggestive of anterior instability is performed. Fear of dislocation or a feeling of anterior pain is considered positive for damage to the anterior capsulolabral complex, which should be relieved with posterior translation of the humerus (relocation maneuver). To summarize, the physical examination demonstrates instability if the apprehension test is positive, multidirectional hyperlaxity when the external rotation at side is equal or above 85 degrees, and a pathological laxity of the inferior glenohumeral ligament if the hyperabduction test is positive.

==Apprehension==
Apprehension can be difficult to diagnose pre- or post-operatively, as it seems more complex than a pure mechanical problem of the shoulder. Although clinical definition seems to be well established, its underlying pathologic mechanism remains unclear. This may explain the wide reported range (3% to 51%) of patients with ongoing apprehension or who will avoid any shoulder movement after an open or arthroscopic stabilization, despite a clinically stable joint.<ref name="HoveliusRahme2016Primary" /><ref>Hovelius L, Vikerfors O, Olofsson A, Svensson O, Rahme H. Bristow-Latarjet and Bankart: a comparative study of shoulder stabilization in 185 shoulders during a seventeen-year follow-up. J Shoulder Elbow Surg 2011;20:1095-101.</ref><ref name=":14">Lädermann A, Lubbeke A, Stern R, Cunningham G, Bellotti V, Gazielly DF. Risk factors for dislocation arthropathy after Latarjet procedure: a long-term study. International orthopaedics 2013;37:1093-8.</ref>

Failure to recognize and adequately address this issue may result in poor outcome and lead to unnecessary surgery or even revision. Furthermore, identifying this condition may allow establishing adequately targeted rehabilitation programs.

===Definition===
An important aspect to incorporate in dislocation management is apprehension, defined as anxiety and motor resistance in patients with a history of anterior glenohumeral instability. Clinically, apprehension sign is defined as fear of imminent dislocation when placing the arm in abduction and external rotation, and should be distinct from mere pain which can be related to inflammation, stiffness and other shoulder pathologies.<ref>Jobe FW, Kvitne RS, Giangarra CE. Shoulder pain in the overhand or throwing athlete. The relationship of anterior instability and rotator cuff impingement. Orthop Rev 1989;18:963-75.</ref><ref>Rowe CR, Zarins B. Recurrent transient subluxation of the shoulder. The Journal of bone and joint surgery American volume 1981;63:863-72.</ref>

Proprioception, as defined by Charles Scott Sherrington, is the sense of the relative position of neighboring parts of the body and strength of effort being employed during movement.<ref>Sherrington C. The Integrative Action of the Nervous System. New York: Charles Scribner's Sons; 1906.</ref>

It is distinct from exteroception, by which one perceives the outside world, and interoception, by which one perceives pain, hunger, or the movement of internal organs. The brain integrates information from proprioception and from the vestibular system into its overall sense of body position, movement, and acceleration. Kinesthesia refers either to the brain's integration of proprioceptive or vestibular inputs.

===“Localization” of Apprehension===
The pathogenesis of apprehension is not fully understood. Theoretically, apprehension could be related to:

1) Brain changes induced by dislocations<ref name=":9" /><ref>Cunningham G, Zanchi D, Emmert K, Kopel R, Van De Ville D, Lädermann A, Haller S, Hoffmeyer P. Neural Correlates of Clinical Scores in Patients with Anterior Shoulder Apprehension. Medicine and science in sports and exercise 2015;47:2612-20.</ref><ref name=":15">Zanchi D, Cunningham G, Lädermann A, Ozturk M, Hoffmeyer P, Haller S. Structural white matter and functional connectivity alterations in patients with shoulder apprehension. Sci Rep 2017;7:42327.</ref><ref name=":16">Zanchi D, Cunningham G, Lädermann A, Ozturk M, Hoffmeyer P, Haller S. Brain activity in the right-frontal pole and lateral occipital cortex predicts successful post-operatory outcome after surgery for anterior glenoumeral instability. Sci Rep 2017;7:498.</ref>

2) Peripheral neuromuscular lesions consecutive to dislocation affecting proprioception<ref name=":17">Atef A, El-Tantawy A, Gad H, Hefeda M. Prevalence of associated injuries after anterior shoulder dislocation: a prospective study. International orthopaedics 2015.</ref>

3) Persistent mechanical instability consisting in micro-motion<ref name=":19">Lädermann A, Denard PJ, Tirefort J, Kolo FC, Chagué S, Cunningham G, Charbonnier C. Does surgery for instability of the shoulder truly stabilize the glenohumeral joint?: A prospective comparative cohort study. Medicine (Baltimore) 2016;95:e4369.</ref>
[[File:1562540576908-lg.jpg|center|thumb|600x600px|Apprehension may be related to (A) central nervous system sequelae, (B) peripheral neurological, muscular or capsular/ligamentous lesions consecutively to dislocation, or (C) mechanical instability as micromovements. Reproduced from Lädermann et al., with permission.]]

====Brain====
Fear, anxiety and anticipation of situations that could lead to a dislocation are essential cognitive processes in shoulder apprehension. Functional magnetic resonance imaging (fMRI) measures brain activity by detecting changes associated with blood flow.<ref>Logothetis NK, Pauls J, Augath M, Trinath T, Oeltermann A. Neurophysiological investigation of the basis of the fMRI signal. Nature 2001;412:150-7.</ref>

When exploring neuronal connections and cerebral changes induced by shoulder dislocation, research revealed that several cerebral areas are modified, representing the different aspects of shoulder apprehension. Specific reorganizations are found in apprehension-related functional connectivity of the primary sensory-motor areas (motor resistance), dorsolateral prefrontal cortex (cognitive control of motor behavior), and the dorsal anterior cingulate cortex/dorsomedial prefrontal cortex and anterior insula (anxiety and emotional regulation) (Figure).<ref name=":9" />
[[File:1562542592373-lg.gif|center|thumb|450x450px|Patients vs control participants had a significantly (P < .05 corrected) higher task-correlated functional connectivity in two almost mirror symmetric components. Reproduced from Haller et al., with permission.]]
 Those regions are involved in the cognitive control of motor behavior. Hence, there is motor control anticipation and muscular resistance (protective reflex mechanism), in order to avoid shoulder movement that could lead to dislocation.<ref>Cieslik EC, Zilles K, Caspers S, et al. Is there "one" DLPFC in cognitive action control? Evidence for heterogeneity from co-activation-based parcellation. Cereb Cortex 2013;23:2677-89.</ref>

Fractional anisotropy, representing white matter integrity, is increased in the left internal capsule and partially in the thalamus in patients compared to healthy controls. Fractional anisotropy correlated positively with pain visual analog scale (VAS) scores (p < .05) and negatively with simple shoulder test (SST) scores (p < .05).<ref name=":15" />

This suggests an abnormal increased axonal integrity and therefore pathological structural plasticity due to the over-connection of white matter fibers in the motor pathway. These structural alterations affect several dimensions of shoulder apprehension as pain perception and performance in daily life.

Shoulder stabilization could allow the brain to partially “recover”. Patients with shoulder apprehension underwent clinical and functional magnetic resonance imaging (fMRI) examination before and one year after shoulder stabilization surgery. Clinical examination showed a significant improvement in postoperative shoulder function compared with preoperative. Coherently, results showed decreased activation in the left pre-motor cortex postoperatively, demonstrating that stabilization surgery induced improvements both at the physical and at the brain level, one year postoperatively (Figure 9). Most interestingly, right–frontal pole and right-occipital cortex activity is associated with good outcome in shoulder performance.<ref name=":16" />
[[File:1562542592786-lg.gif|center|thumb|400x400px|Task related General Linear Model (GLM) shows higher activation in baseline vs. follow-up for apprehension videos vs. control videos, representing partial brain healing. Reproduced from Zanchi et al., with permission.]]

====Peripheral Neuromuscular Lesion====
During a traumatic dislocation, there are a disruption of the shoulder tendinomuscular (in 10% of cases) and peripheral nerve lesions (in 14% of cases).<ref>Robinson CM, Shur N, Sharpe T, Ray A, Murray IR. Injuries associated with traumatic anterior glenohumeral dislocations. J Bone Joint Surg Am 2012;94:18-26.</ref>

However, this does not account for subclinical neurologic damage that may be much more preponderant. Capsuligamentous structures surrounding the glenohumeral joint are richly innervated with proprioceptors and therefore play an important sensorimotor role in addition to their primary mechanical stabilizising function. Thus, when considering the extensive and frequent damage to these structures after shoulder dislocation (Figure), there is bound to be an important loss in glenohumeral proprioception.<ref name=":5" /><ref name=":17" />

The latter plays a significant role in stabilization of a normal healthy shoulder and after any shoulder injury by contributing to motor control.<ref name=":18">Fyhr C, Gustavsson L, Wassinger C, Sole G. The effects of shoulder injury on kinaesthesia: a systematic review and meta-analysis. Man Ther 2015;20:28-37.</ref>
[[File:1562542594443-lg.jpg|center|thumb|600x600px|Arthroscopic view of a left shoulder through a posterior portal. This patient has sustained more than 50 subluxations. The axillary nerve is clearly identifiable (white asterisk). There is no more capsule or inferior glenohumeral ligament, and the subscapularis muscle is hardly recognizable. Reproduced from Lädermann A, Benchouk S, Denard P. Traumatic Anterior Shoulder Instability: General concepts & proper management. In: Park J, ed. Sports Injuries to the Shoulder and Elbow. Berlin Heidelberg: Springer-Verlag; 2015, with permission.]]
Surgical stabilization has been shown to help proper healing of these structures and thus restoring proprioception of the glenohumeral joint.<ref>Myers JB, Lephart SM. Sensorimotor deficits contributing to glenohumeral instability. Clin Orthop Relat Res 2002:98-104.</ref>

====Glenohumeral Joint====
The third etiologic factor for apprehension is persistent micro-motion in the glenohumeral joint despite a clinically stable shoulder, satisfactory radiographic results, and no new episode of subluxation or dislocation. Shoulder dislocation causes damage to the capsuloligamentous complex in 52% of the cases, and the glenoid labrum in 73% of the cases.<ref>Liavaag S, Stiris MG, Svenningsen S, Enger M, Pripp AH, Brox JI. Capsular lesions with glenohumeral ligament injuries in patients with primary shoulder dislocation: magnetic resonance imaging and magnetic resonance arthrography evaluation. Scandinavian journal of medicine & science in sports 2011;21:e291-7.</ref><ref name=":5" />

The plastic deformation of these structures becomes progressively worse with subsequent episodes.The plastic deformation of these structures becomes progressively worse with subsequent episodes. In addition to progressive soft tissue injury, recurrent dislocations induce bony lesions, which may involve the glenoid (bony Bankart), the posterolateral humeral head (Malgaine), or both. Severity of apprehension, quantified as the moment at which it appears during the course of abduction and external rotation, seems to be correlated to the extent of bone loss. Capsular redundancy has also been recognized as a risk factor for ongoing apprehension after surgical stabilization and Ropars et al. found a significantly decreased apprehension in patients with associated capsulorraphy to Latarjet procedures, compared with patients with Latarjet and no capsular reconstruction.<ref name=":12">Ropars M, Cretual A, Kaila R, Bonan I, Herve A, Thomazeau H. Diagnosis and treatment of anteroinferior capsular redundancy associated with anterior shoulder instability using an open Latarjet procedure and capsulorrhaphy. Knee Surg Sports Traumatol Arthrosc 2016;24:3756-64.</ref>

However, these changes may be very subtle and therefore not detectable on standard clinical magnetic resonance imaging in neutral position. This has been described by Patte et al. in non-operated patients and popularized under the name of "unstable painful shoulder".<ref name=":11" /><ref name=":10" />

This micro-motion may yet still be present after surgical stabilization. Shoulder stabilization may thus only prevent new episodes of dislocation, rather than actually truly stabilizing the shoulder.<ref>Singer GC, Kirkland PM, Emery RJ. Coracoid transposition for recurrent anterior instability of the shoulder. A 20-year follow-up study. J Bone Joint Surg Br 1995;77:73-6.</ref><ref>Lädermann A, Tirefort J, Zanchi D, Haller S, Charbonnier C, Cunningham G. Shoulder Apprehension: a Multifactorial Approach. EFORT Open Rev. 2018 24;3(10):550-557</ref>

A study described glenohumeral translation in patients with traumatic anteroinferior instability and subsequently analyzed the effect of glenohumeral stabilization on this translation. For all movements, the authors recorded humeral head position of the contralateral and ipsilateral shoulders in relation to the glenoid center pre- and 1 year post-operatively. They observed an anterior translation of the humeral head (Figure), especially during flexion and abduction movements (p < .05 and p < .05, respectively). One year after surgery, all patients had a clinically stable shoulder and none presented with a new episode of dislocation or subluxation.

However, anterior translation of the humeral head was not significantly reduced and remained close to preoperative values confirming that shoulder stabilization does not stabilize the shoulder but uniquely prevents further dislocation. These findings have several important implications. First, it may explain residual pain, apprehension, and impossibility to return to sport at the same level as reported in other studies. Second, persistent abnormal motion between the glenoid and the humeral head might be the underlying cause of dislocation arthropathy that is observed with a prevalence of 36%. Repeated sliding of the humeral head against the glenoid associated with degenerative changes of cartilage properties and decreased biological healing potential related to aging, could lead to a vicious circle of extensive cartilage damage.<ref name=":19" />
[[File:1562542595262-lg.jpg|center|thumb|600x600px|(A) Abduction simulation obtained from shoulder’s CT reconstruction and optical motion capture, (B) and (C) show a zoom in the shoulder (front and top views). In image (C), we clearly observe an anterior translation (arrow) of the humeral head center (pink sphere) with respect to the glenoid center (white sphere). Note that the clavicle is not shown for clarity. Reproduced from Lädermann et al., with permission.]]
 

==Scores==

===Single Assessment Numeric Evaluation (SANE)-instability score===
A modified Single Assessment Numeric Evaluation (SANE) score specific to shoulder instability, the SANE-instability score, has been developed.<ref name=":0">Lädermann A, Denard PJ, Collin P, Mohamed Ibrahim M, Bothorel H, Chiu JC. Single Assessment Numeric Evaluation for instability as an alternative to the Rowe score. J Shoulder Elbow Surg. 2020;S1058-2746(20)30686-8</ref> The SANE-instability score (100 points) is assessed with a single question: “What is the overall percent value of your shoulder if a completely stable shoulder represents 100%?” A high correlation between the Rowe and SANE-instability scores for shoulder instability has been found before and after treatment, as well as for different patient age groups and treatment types. This score is easy to collect and use because it can be collected in the office or remotely, thereby saving considerable time and potentially improving compliance.<ref name=":0" />

===Rowe===
The 1978 Rowe score is calculated with the 3 following items: stability (50 points), motion (20 points), and function (30 points).<ref>Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end-result study. J Bone Joint Surg Am. 1978; 60: 1-16</ref>

===Walch-Duplay===
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===WOSI===
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===ISIS===
Boileau et al. proposed a simple 10-point scale scoring system (instability severity index score (ISIS)) based on factors derived from a pre-operative questionnaire, physical examination, and anteroposterior radiographs to determine the risk of treatment failure following isolated arthroscopic Bankart repair (Table). In this model an ISIS of 3 or less was associated with a 5% rate of recurrence, an ISIS of 4 to 6 was associated with a 10% rate of recurrence, and an ISIS over 6 was associated with a 70% rate of recurrence. Although it has imperfections, this score, validated since, has merit to easily remind the clinician of factors that are important to consider when evaluating a patient.<ref name=":8" /><ref>Rouleau DM, Hebert-Davies J, Djahangiri A, Godbout V, Pelet S, Balg F. Validation of the instability shoulder index score in a multicenter reliability study in 114 consecutive cases. Am J Sports Med 2013;41:278-82.</ref>

'''''Table: The instability severity index score is based on a pre-operative questionnaire, clinical examination, and radiographs.'''''
[[File:1562543299662-lg.jpg|center|thumb|899x899px|Figure. 12 * AP, anteroposterior]]
 

==Essential Radiology==
Radiographic evaluation is based on whether the dislocation is acute or chronic.

===Acute Dislocation===
Three views plain radiographs, including true anteroposterior of the glenohumeral joint, scapular Y (scapular lateral), and Velpeau axillary views are the mainstay of imaging in the setting of traumatic anterior instability.<ref>Bloom MH, Obata WG. Diagnosis of posterior dislocation of the shoulder with use of Velpeau axillary and angle-up roentgenographic views. J Bone Joint Surg Am 1967;49:943-9.</ref>

The latter view is crucial to obtain, as the two first alone do not allowed to exclude a dislocation. The goal is to confirm the direction of dislocation and to evaluate associated lesions. One reduced, further imaging studies in the setting of an associated fracture (computed tomography (CT)), suspicion of rotator cuff injury (ultrasonography or magnetic resonance imaging (MRI)), or vascular impairment (injected CT) may be warranted.

===Preoperative Planning in Case of Recurrent Dislocation===
The first step is to analyze, if available, plan radiographs with the shoulder out of joint to confirm the direction of instability. Plain radiographs including anteroposterior in neutral, internal and external rotations, scapular Y and Bernageau views are then obtained.<ref>Bernageau J, Patte D, Debeyre J, Ferrane J. [Value of the glenoid profile in recurrent luxations of the shoulder]. Rev Chir Orthop Reparatrice Appar Mot 1976;62:142–7.</ref>

Bone loss, static instability, post-dislocation arthropathy, and coracoid non-union (if a Latarjet or a Bristow procedures are planned) have to be estimated. Magnetic resonance imaging (MRI) arthrogram is useful to assess for soft tissue such as an anterior labral tear (Figure). 
[[File:1562543301909-lg.jpg|center|thumb|600x600px|Coronal T1 SPIR magnetic resonance imaging (MRI) of a right shoulder showing disruption of the anteroinferior glenoid labrum. B]]
Associated intra-articular pathology such as SLAP, HAGL, and rotator cuff lesions or a paralabral cyst are also assessed (Figure).

The evaluation is completed by a 3D computed tomography arthrogram in the setting of recurrent instability in which there is primary concern for bone loss. The extent of both glenoid bone loss and Hill-Sachs lesions are best assessed by computed tomography scan and are used to determine the need for a bony procedure as opposed to arthroscopic Bankart repair (Figures).
[[File:1562543901744-lg.jpg|center|thumb|600x600px|A) Sagittal view of a CT arthrogram of a left shoulder demonstrates a significant Bankart fracture that produces an “inverted-pear” glenoid. B) Plain anteroposterior radiograph reveals an anteroinferior glenohumeral dislocation with an “engaged” Malgaigne (Hill-Sachs) lesion of the humerus.]]
 
[[File:1562544592047-lg.jpg|center|thumb|600x600px|Axial computed tomography (CT) arthrogram view showing a large Malgaigne lesion.]]
 

==Treatments==
The degree, nature and combination of injuries induced by traumatic glenohumeral instability are highly variable. Damage to the bony and soft tissue stabilizers of the shoulder, as well as neurologic impairment, must be detected and analyzed in order to provide the patient with the most adequate treatment option. This new knowledge should be applied to rehabilitation therapy and surgical stabilization techniques. As the current stabilization techniques do not seem to prevent residual glenohumeral micro-motion, it remains to be determined which factors help to minimize this phenomenon, whether it is, the increase in the anteroposterior diameter of the glenoid with a bone graft, the sling effect provided by the conjoined tendon or the long head of the biceps, the capsulorraphy, the repaired labrum or the remplissage.<ref>Lädermann A, Bohm E, Tay E, Scheibel M. Bone-mediated anteroinferior glenohumeral instability : Current concepts. Der Orthopade 2018.</ref><ref name=":13">Collin P, Lädermann A. Dynamic Anterior Stabilization Using the Long Head of the Biceps for Anteroinferior Glenohumeral Instability. Arthrosc Tech 2018;7:e39-e44.</ref><ref>Young AA, Maia R, Berhouet J, Walch G. Open Latarjet procedure for management of bone loss in anterior instability of the glenohumeral joint. J Shoulder Elbow Surg 2011;20:S61-9.</ref><ref name=":12" />

===Methods of Reduction===
Around 400 BC, Hippocrates, the father of Western medicine, introduced the traction method to reduce the shoulder. The patient lay supine whilst the physician standing on the patient's affected side held the arm and applied traction. The stockinged foot of the physician placed in the axilla served as counter traction. This technique was detailed in the Hippocratic Corpus, and as it remained the primary medical text for centuries so did the method. Similar technique of reduction was re-introduced in the 1870 as a painless technique by Theodor Kocher, but is now obsolete because of the likelihood of serious complications.<ref>Kocher E. Eine neue Reductionsmethode für Schulterverrenkung. Berlin Klin 1870;7:101-5.</ref>

===Conservative (Nonoperative) Treatment===
Heading towards a better understanding of the complex and multifactorial origins of glenohumeral instability and apprehension, postoperative management may in turn also be improved, notably in challenging cases of patients with persistent apprehension, despite a clinically stable shoulder. Knowing that shoulder apprehension could be the result of ongoing cerebral abnormalities or residual micro-motion may avoid costly series of onerous investigations, useless physiotherapy sessions or even re-operations. Furthermore, this perspective offers a new angle of a therapeutic approach that differs from conventional manual rehabilitation methods centered on the glenohumeral joint itself. If persistent apprehension or micro-motion is detected, growing research evidence supports the use of a multidisciplinary approach including:

1) A "reafferentation" (reconveying and connecting the neurological peripheral input to the cortex)89 of the shoulder particularly focused on proprioceptive work,69 which has been proved to lead to superior neuromuscular control than strengthening alone.<ref>Horvat JC. [Reconstruction of the spinal cord and its motor connections using embryonal nervous tissue transplantation and peripheral nerve autotransplantation. A study in the adult rat]. Neurochirurgie 1991;37:303-11.</ref><ref>Salles JI, Velasques B, Cossich V, Nicoliche E, Ribeiro P, Amaral MV, Motta G. Strength training and shoulder proprioception. J Athl Train 2015;50:277-80.</ref><ref name=":18" />

2) A biofeedback therapy where the patient directly visualizes his abnormal response to a negative stimulus on fMRI or electroencephalogram, and can thereby actively correct it. This treatment modality has already shown to improve shoulder control and performance in various settings.<ref>deCharms RC, Maeda F, Glover GH, Ludlow D, Pauly JM, Soneji D, Gabrieli JD, Mackey SC. Control over brain activation and pain learned by using real-time functional MRI. Proceedings of the National Academy of Sciences of the United States of America 2005;102:18626-31.</ref><ref>Antunes A, Carnide F, Matias R. Real-time kinematic biofeedback improves scapulothoracic control and performance during scapular-focused exercises: A single-blind randomized controlled laboratory study. Hum Mov Sci 2016;48:44-53.</ref><ref>Huang HY, Lin JJ, Guo YL, Wang WT, Chen YJ. EMG biofeedback effectiveness to alter muscle activity pattern and scapular kinematics in subjects with and without shoulder impingement. J Electromyogr Kinesiol 2013;23:267-74.</ref>

3) A cognitive behavioral approach to decondition this pathological residual apprehension by making them realize residual apprehension does not necessarily lead to recurrent instability with gradual exposition that has already shown successful results in the treatment of kinesiophobia,94-96 a condition based on a re-injury fear-avoidance model initially described in low-back pain,97 further popularized in sports medicine98 and various upper limb conditions.<ref>Das De S, Vranceanu AM, Ring DC. Contribution of kinesophobia and catastrophic thinking to upper-extremity-specific disability. J Bone Joint Surg Am 2013;95:76-81.</ref>

4) Electric stimulation of hypoactive rotator cuff and periscapular muscles.<ref>Moroder P, Minkus M, Bohm E, Danzinger V, Gerhardt C, Scheibel M. Use of shoulder pacemaker for treatment of functional shoulder instability: Proof of concept. Obere Extrem 2017;12:103-8.</ref>

===Treatment of Acute First Traumatic Dislocations===
The first step, whenever possible, is to obtain a complete set of radiographs before attempting a reduction. This will allow an assessment of the type of dislocation and associated bone injuries. Attempting to reduce a fracture dislocation can have troublesome clinical and legal consequences (Figure).
[[File:1562546209492-lg.jpg|center|thumb|600x600px|A) An anteroposterior plain radiograph of a left shoulder shows an anterior dislocation with a nondisplaced humeral neck fracture on the prereduction radiographs. B) Radiographs after attempting a closed reduction without adequate muscle relaxation reveal displacement of the fracture with the humeral head remaining anteriorly.]]
Exceptions are an impossibility to have reasonably fast access to radiology or a patient with neurological impairment. Because of the possible association of nerve injuries and, to a lesser extent, vascular injuries (Figure), an essential part of the physical examination is an assessment of the neurovascular status of the upper extremity before reduction.<ref>de Laat EA, Visser CP, Coene LN, Pahlplatz PV, Tavy DL. Nerve lesions in primary shoulder dislocations and humeral neck fractures. A prospective clinical and EMG study. J Bone Joint Surg Br 1994;76:381-3.</ref><ref>Brown FW, Navigato WJ. Rupture of the axillary artery and brachial plexus palsy associated with anterior dislocation of the shoulder. Report of a case with successful vascular repair. Clin Orthop Relat Res 1968;60:195-9.</ref>
[[File:1562529745788-lg.jpg|center|thumb|600x600px|A) A 54-year-old patient sustained a fracture dislocation of the right shoulder. At clinical examination, no peripheral pulse was palpated. B) During open reduction, the axillary artery (white arrows) was found kinked around the fractured humeral head.]]
They are numerus appropriate methods of reduction that have been described. The second step is to use the technique of closed reduction which is mastered by the doctor who will perform the maneuver. The glenohumeral joint should be reduced as gently and expeditiously as possible. In the case of fracture dislocation, the reduction is best performed under general anesthesia to have adequate muscle relaxation. After reducing the dislocation, plain radiographs are obtained to verify the adequacy of the reduction.

Results concerning conservative treatment are still debatable. A stable shoulder is obtained at ten years in only half of patients with conservative treatment.<ref name=":7" />

However, recurrence rate is highly dependent on age and activity of the patient; studies have reported a 72% to 95% recurrence in patients under 20 years of age, and 70% to 82% recurrence between the ages of 20 and 30 years, and only 30% in those over 30 years of age.<ref>te Slaa RL, Brand R, Marti RK. A prospective arthroscopic study of acute first-time anterior shoulder dislocation in the young: a five-year follow-up study. J Shoulder Elbow Surg 2003;12:529-34.</ref><ref name=":6" /><ref>Robinson CM, Howes J, Murdoch H, Will E, Graham C. Functional outcome and risk of recurrent instability after primary traumatic anterior shoulder dislocation in young patients. J Bone Joint Surg Am 2006;88:2326-36.</ref>

Many patients above the age of 30 would consequently undergo unnecessary surgery if proposed after the first dislocation. Conservative treatment after the first traumatic anterior dislocation may be thus recommended for patients who are not actively engaged in sports, above the age of 30 years old, with a low functional demand, with an associated humeral fracture, or for the athlete with an in-season shoulder dislocation. For the latter situation, athletes are allowed to attempt to return to competition provided there is enough time left in the season to permit adequate rehabilitation with progression to sport-specific drills.

Rehabilitation, including return of range of motion and strengthening of dynamic stabilizers may facilitate return to sport within several weeks. Motion-limiting braces that prevent extreme shoulder abduction, extension, and external rotation are often prescribed as it may reduce the risk of recurrence. However, such braces are not well-tolerated in patients who must complete certain overhead tasks such as throwing. Moreover, a second in-season shoulder dislocation should lead to removal from sport and proceeding with stabilization so as to avoid further glenohumeral damage.

A number of studies have compared nonoperative treatment and arthroscopic stabilization. Overall, these studies report a sevenfold reduction in the risk of recurrent instability after arthroscopic stabilization, when compared with nonoperative treatment for the first-time dislocator.<ref>Murray IR, Ahmed I, White NJ, Robinson CM. Traumatic anterior shoulder instability in the athlete. Scandinavian journal of medicine & science in sports 2013;23:387-405.</ref>

A Cochrane review concluded that early surgical intervention is warranted in young adults aged less than 30 years engaged in highly demanding physical activities.<ref>Handoll HH, Almaiyah MA, Rangan A. Surgical versus non-surgical treatment for acute anterior shoulder dislocation. The Cochrane database of systematic reviews 2004:CD004325</ref>

Consequently, for patients who are actively engaging in a collision or contact or overhead sport, who risk their life in case a new dislocation (e.g. firemen, proponents of extreme sports like base jumping, and climbing), with associated static anterior subluxation, an interposed tissue or a nonconcentric reduction, or patients with rotator cuff avulsion, conservative measures are usually inadequate and prompt surgery is indicated.

===Surgical (Operative) Treatment===
Recurrent dislocation is not trivial. Each episode creates new lesions and increases the risk of developing dislocation arthropathy. The concept of early operative surgical management of the first-time dislocator has consequently been introduced to address the high recurrence rate in the young athletic population. Surgery should be proposed, as having the ultimate aim to achieve a pain-free stable shoulder while preserving range of motion. The surgical approach is based on the extent of bone loss and patient-specific risk factors for recurrence.

====Soft tissue procedures====
=====Bankart and Associate Repairs=====
The aim of a Bankart repair is to restore anatomy by reattaching the labrum to the glenoid (Figure) and tighten the inferior glenohumeral ligament by shifting from inferior to superior. Several technical factors are also important to success. It is important to place anchors at the margin of the articular surface (as opposed to the glenoid neck) to allow recreation of the labral bumper. The surgeon must be sure to obtain a proper inferior to superior shift of the capsule (Neer’s modification). Although this surgery can be performed in an open manner, the advantage of an arthroscopic approach is that it preserves the subscapularis and allows assessment of associated pathology. The literature demonstrates that patients with low risk of recurrence will benefit from either an anatomic open or arthroscopic repair with an acceptable rate of recurrence.<ref>Harris JD, Gupta AK, Mall NA, Abrams GD, McCormick FM, Cole BJ, Bach BR Jr, Romeo AA, Verma NN. Long-term outcomes after Bankart shoulder stabilization. Arthroscopy 2013;29:920-33.</ref>
[[File:1562546210935-lg.jpg|center|thumb|600x600px|Illustration of a Bankart repair (sagittal view of a right shoulder). Courtesy of Gilles Walch.]]

HAGL (Humeral Avulsion of the Glenohumeral Ligaments) lesions are uncommon causes of anterior instability. There are 3 variants of HAGL lesions: 1. Avulsion from bone 2. Capsular split 3. Combined bone avulsion and capsular split. These lesions can be addressed by repair or more easily by a Latarjet.

=====Remplissage=====
Remplissage has been described by Connoly and may be used as an adjunct to arthroscopic Bankart repair in the setting a of large Malgaigne (Hill-Sachs) lesion with glenoid bone loss of <25%.<ref>Connoly J. Humeral head defects associated with shoulder dislocations. American Academy of Orthopaedic Surgeons Instructional course lectures: Mosby; 1972:42-54.</ref>

This technique consists of a posterior capsulodesis and infraspinatus tenodesis that fills the Malgaigne lesion. The purpose is to render the Malgaigne lesion extra-capsular, avoiding its engagement. Wolf et al. and Boileau et al. presented encouraging mid- to long-term results of arthroscopic remplissage and concomitant anterior Bankart repair.<ref name=":20">Boileau P, O'Shea K, Vargas P, Pinedo M, Old J, Zumstein M. Anatomical and functional results after arthroscopic Hill-Sachs remplissage. J Bone Joint Surg Am 2012;94:618-26.</ref><ref name=":21">Wolf EM, Arianjam A. Hill-Sachs remplissage, an arthroscopic solution for the engaging Hill-Sachs lesion: 2- to 10-year follow-up and incidence of recurrence. J Shoulder Elbow Surg 2014;23:814-20.</ref>

Surgical Technique
The arthroscope can typically remain in the posterior portal because the 70 degrees angle enhances appropriate visualization. Depending on patient anatomy, the arthroscope can be switched to the anterolateral portal to obtain another view of the defect. A spinal needle is centered over the Malgaigne (Hill-Sachs) lesion, and an accessory posterolateral portal is created 2 fingerbreadths lateral to the posterior viewing portal to allow orthogonal insertion of suture anchors. The use of a cannula is optional. A shaver is used to abrade the Malgaigne (Hill-Sachs) lesion. Two anchors are inserted in the valley of the defect adjacent to the articular margin, 1 superior and 1 inferior. If used, the cannula is at this point retracted into the subdeltoid space. A curved penetrating grasper is used to retrieve the inferior anchor suture, followed by a straight penetrating grasper for the superior anchor suture. The humeral head is reduced, and the inferior sutures are tied in mattress fashion in the subdeltoid space, followed by the superior sutures, to complete the remplissage.

=====Subscapularis Tendon Augmentation or Capsular Reconstruction=====
When traditional arthroscopic Bankart repair is not possible due to severe capsulolabral deficiency, different types of open or arthroscopic subscapularis tendon augmentation or capsular reconstruction have been described.<ref name=":27">Denard PJ, Narbona P, Lädermann A, Burkhart SS. Bankart augmentation for capsulolabral deficiency using a split subscapularis tendon flap. Arthroscopy 2011;27:1135-41.</ref><ref>Maiotti M, Massoni C, Russo R, Schroter S, Zanini A, Bianchedi D. Arthroscopic Subscapularis Augmentation of Bankart Repair in Chronic Anterior Shoulder Instability With Bone Loss Less Than 25% and Capsular Deficiency: Clinical Multicenter Study. Arthroscopy 2016.</ref><ref>Maiotti M, Russo R, Zanini A, Schroter S, Massoni C, Bianchedi D. Arthroscopic Bankart repair and subscapularis augmentation: an alternative technique treating anterior shoulder instability with bone loss. J Shoulder Elbow Surg 2016;25:898-906.</ref><ref>Russo R, Della Rotonda G, Cautiero F, Ciccarelli M, Maiotti M, Massoni C, Di Pietto F, Zappia M. Arthroscopic Bankart repair asciated with subscapularis augmentation (ASA) versus open Latarjet to treat recurrent anterior shoulder instability with moderate glenoid bone loss: clinical comparison of two series. Musculoskelet Surg 2016.</ref>

[[File:1562546211256-lg.jpg|center|thumb|609x609px|Bankart augmentation with split subscapularis tendon transfer. (A) A flap of the posterior portion of the superior half of the subscapularis tendon is created. (B) The subscapularis flap is mobilized in a trapdoor fashion such that the capsular surface of the subscapularis tendon is reflected from medial to lateral as a separate lamina while the outer surface is left unaltered. Note, arrows in (A) and (B) point to the free margin of the subscapularis tendon flap. (C) The subscapularis flap undergoes tenodesis to the anterior glenoid suture anchors to augment capsulolabral deficiency. Reproduced from Denard et al.,<ref name=":27" /> with permission.|alt=]]

Surgical technique
A standard diagnostic arthroscopy is performed with a 30 degrees arthroscope, viewing through a posterior portal with a pump maintaining pressure of 50 mm Hg. The labrum is inspected in its entirety. An anterior portal is established just above the lateral half of the subscapularis and medial to the sling of the biceps, by use of an 18-gauge spinal needle with an outside-in technique. An anterosuperolateral portal is similarly established off the anterolateral border of the acromion. This portal should be placed so that it provides a 45 degrees angle of approach to the superior glenoid. The arthroscope is placed in the anterosuperolateral portal, and the anterior labrum is more thoroughly inspected. The remaining capsulolabral sleeve is dissected from the glenoid neck with an arthroscopic elevator until the subscapularis muscle is visible deep to the cleft. A 2- to 3-mm strip of articular cartilage is removed along the glenoid rim with a ring curette, creating an enhanced bone bed for capsulolabral repair. A capsulolabral repair is performed inferiorly with whatever good tissue remains. An anteroinferior anchor is placed. After placement of this anchor, if there is insufficient capsulolabral tissue to create the desired “bumper” along the anterior glenoid rim, the surgeon must consider various reconstructive options, including a split subscapularis tendon flap.

=====Augmentation With Split Subscapularis Flap=====
To augment the capsulolabral deficiency, a flap of the posterior portion of the superior half of the subscapularis tendon is mobilized and undergoes tenodesis to the anterior glenoid. This flap is created in a “trapdoor” fashion such that the capsular surface of the subscapularis tendon is reflected from medial to lateral as a separate lamina while the outer surface in left unaltered. By use of arthroscopic scissors introduced through the anterior portal, a longitudinal incision through one-half the thickness of the subscapularis is created in the superior half of the tendon (Figure).
[[File:1562547676763-lg.jpg|center|thumb|600x600px|Left shoulder, anterosuperolateral viewing portal, showing creation of a split subscapularis flap to augment a Bankart repair in the setting of capsulolabral deficiency. The flap is created with arthroscopic scissors introduced through an anterior portal. Suture is also seen from an inferior Bankart repair (arrow). (SSc, subscapularis tendon.). Reproduced from Denard et al.<ref name=":27" />, with permission.]]

Care is taken not to violate the full thickness of the subscapularis. The subscapularis flap dissection progresses from medial to lateral until the leading medial edge of the flap is mobile enough to reach the anterior glenoid. After mobilization of the subscapularis tendon flap, additional suture anchors are placed on the previously prepared glenoid strip at the 3-o'clock and 4-o'clock positions. Sutures from the anchor are passed through the subscapularis flap and tied as described previously. This completes the augmentation with a split subscapularis tendon flap (Figure).

[[File:1562547677981-lg.jpg|center|thumb|1071x1071px|Left shoulder, anterosuperolateral viewing portal, showing completed arthroscopic Bankart repair augmented with a split subscapularis flap in the setting of capsulolabral deficiency. (A) Completed repair showing restoration of anterior soft tissue by use of the split subscapularis tendon (SSc) flap. (B) The split between the subscapularis (arrow) is visualized anterior to the flap that has undergone tenodesis. (G, glenoid; H, humeral head.). Reproduced from Denard et al.,<ref name=":27" /> with permission.]]

Postoperatively, the patient's extremity is placed in a sling for 6 weeks. At the end of six weeks, stretching exercises are commenced with full forward flexion allowed and external rotation to half that of the contralateral shoulder. The goal is to achieve half the external rotation of the normal side at three months postoperatively. Strengthening is delayed until four months postoperatively because this is usually a last-resort salvage procedure. Return to full activities is delayed until one year postoperatively.

=====Dynamic Anterior Stabilization (DAS)=====
[[File:1562547970547-lg.mp4|center|thumb|600x600px|Video]]

Dynamic anterior stabilization transfers the long head of the biceps to the anterior glenoid margin, thereby creating a “sling effect” (Figure).
[[File:1562547677283-lg.jpg|center|thumb|700x700px|(A) Native shoulder. (B) Latarjet procedure. The coracoid graft including the conjoint tendon is secured to the anterior glenoid by means of two 4.5-mm screws. (C) Dynamic anterior stabilization. The long head of the biceps is transferred to the anterior glenoid margin. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]
 The dynamic anterior stabilization technique provides decreased anterior glenohumeral translation in cases of Bankart lesions with limited anterior bone loss (<20%)<ref>Mehl J, Otto A, Imhoff FB, Murphy M, Dyrna F, Obopilwe E, Cote M, Lädermann A, Collin P, Beitzel K, Mazzocca AD. Dynamic Anterior Shoulder Stabilization With the Long Head of the Biceps Tendon: A Biomechanical Study. Am J Sports Med. 2019 May;47(6):1441-1450.</ref>

In comparison with isolated Bankart repair, it is able to stop the anterior translation less anterior and therefore reduces the risk of a conflict between the humeral head and the anterior margin of the glenoid. It is also easier and safer than arthroscopic Latarjet. Moreover, it does not require screws nor traction of the coracoid process, and should consequently reduce the risks of neurologic damage. Furthermore, the procedure can be performed with only 3 small incisions (Video), as it does not require coracoid transfer, which eliminates risks of nerve dissection, graft overhang and cortical resorption, hence reducing the probability for dislocation arthroplasty. Lastly, the pectoralis minor remains intact, which would avoid scapular dyskinesis. The potential drawbacks of the dynamic anterior stabilization are that it relies on the long head of biceps tendon, which has smaller diameter than the conjoint tendon and could therefore have a weaker “sling effect” than that of the standard Latarjet. Also, there are, like in the Latarjet procedure, the risks of biceps pain, and secondary iatrogenic factors. Furthermore, in cases with larger bone defects (≥ 20 %) there is a relevant posterior and inferior shift of the humeral head in relation to the glenoid, when the arm is brought in the ABER position.(reference to be completed) Indications and limitations are yet to be defined. MRI scans showed that the transposed long head of the biceps successfully healed to the glenoid rim and remained intact at the 6- and 12-month follow-ups in patients who underwent dynamic anterior stabilization for the treatment of chronic anteroinferior glenohumeral instability with bipolar and/or SLAP II lesions with limited (<13.5%) to subcritical (13.5%—25%) glenoid bone loss.<ref name=":28">de Campos Azevedo C, Ângelo AC. All-Suture Anchor Dynamic Anterior Stabilization Produced Successful Healing of the Biceps Tendon: A Report of 3 Cases. JBJS Case Connect . 2021:17;11(1)</ref> However, it is recommended that future studies are carried out with a more long-term follow-up.

Preoperative Patient Positioning
The operation, illustrated in the video, is performed in the semi-beach chair position under general anesthesia with an interscalene block. An examination under anesthesia is performed before prepping and draping the arm.

Initial Exposure and Portal Placement
An intra-articular approach is used through a standard posterior portal (soft spot), a standard diagnostic arthroscopy is performed with a 30-degree arthroscope and a pump maintaining pressure at 60 mm Hg. Antero-lateral and anterior portals are then established by an outside-in technique using a spinal needle as a guide. The rotator interval is opened, and the internal structures (glenoid defects, humeral defects, etc.) are further assessed with a probe.

Anterior Glenoid Preparation
From a lateral viewing portal, the labrum, if necessary, is detached from the glenoid, and a suture is passed around the labrum and pulled through the posterior portal to increase access for preparation of the anterior glenoid (Figure). The glenoid neck is cleaned from soft tissues at around 3 o’clock with a burr.

[[File:1562549774413-lg.jpg|center|thumb|600x600px|Intra-articular view of a right shoulder, anterolateral viewing portal. A suture is passed around the detached labrum and pulled through the posterior portal to increase access for preparation of the anterior glenoid. ∗ indicates the labrum, the black arrows the access to the glenoid neck, and HH the humeral head. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

Addressing the Long Head of Biceps and Subscapularis Split
The long head of biceps is then tenotomized and the biciptal groove is opened laterally and distally to avoid detaching the subscapularis (Figure).
[[File:1562549775232-lg.jpg|center|thumb|600x600px|Retrocoracoid space of a right shoulder, anterolateral viewing portal. After LHB tenotomy, the bicipital sheath (black arrows) is opened laterally and the LHB (∗) is found. (CT, conjoint tendon; LHB, long head of the biceps.). Reproduced from Collin et al.,<ref name=":13" /> with permission.]]
The biceps is then exteriorized, and secured 20 mm from the proximal tendon. From a lateral viewing portal the subscapularis is exposed on three sides, together with the lateral margin of the conjoint tendon. Three options exist to create a split in the middle of the subscapularis above the junction of the superior two-thirds used in the standard Latarjet procedure: From a lateral viewing portal, either a switching stick (Wissinger Rod) can be passed across the glenohumeral joint through a posterior approach at the level of the inferior glenoid (Figure), an outside-in approach can be used or simply by passing through the subscapularis muscle with a suture passer, by grabbing the sutures that secure the biceps and pulling the biceps through the tendon.

[[File:1562549776269-lg.jpg|center|thumb|600x600px|Intraoperative view of a right shoulder with passage of the switching stick (∗) across the glenohumeral joint at the level of the inferior glenoid to the subscapularis. (HH, humeral head). Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

The switching stick is now found in the retrocoracoid space and maintained lateral to the conjoint tendon to avoid damaging the nerve plexus. The probe is then introduced through the anterior portal to complete the split.

Long Head of Biceps Tenodesis to Anterior Glenoid
A drill is then used to prepare a hole at 3 o'clock from anterior to posterior within the neck of the glenoid, 2.0 cm deep, depending on the length of the interference screw. The LHB tendon is then passed through the subscapularis split into the pre-drilled hole, to establish the “sling effect”, and fixed using a tenodesis screw (Figure).

[[File:1562549775588-lg.jpg|center|thumb|600x600px|Intraoperative view of a right shoulder through the subscapularis split, anterolateral viewing portal. The long head of the biceps tendon (black arrow) is fixed using a tenodesis screw (∗) to establish the “sling effect”. Reproduced from Collin et al.<ref name=":13" />, with permission.]]

Alternatively, the biceps may be managed without exteriorization, as shown in the linked video.[https://www.vumedi.com/video/all-suture-anchor-double-double-pulley-dynamic-anterior-stabilization/] When choosing this technical variant, two all-suture anchors (double loaded with sutures) must me placed on the glenoid rim and each of the respective eight suture limbs must be passed through the biceps before the tenotomy is completed; a double-pulley technique is used to shuttle the biceps through the subscapularis tendon split to the anteroinferior glenoid; the biceps is fixed to the glenoid with a total of four knots (Figure).

[[File:Figure 4 jpeg.jpg|none|thumb|959x959px|Representation of the posterior portal arthroscopic view of the trans-subscapular transposition of the long head of the biceps using the double double-pulley on a right shoulder in the beach chair position. A) Two knots of the double double-pulley are tied after all suture limbs were passed through the long head of the biceps (LHB) tendon; B) the remaining 4 opposing suture limbs are pulled and the LHB tendon reaches the anteroinferior glenoid rim after passing through the subscapularis tendon (SC) split; C) the dashed line represents the final course of the LHB tendon through and anteriorly to the subscapularis tendon. The opposing 4 suture limbs will each be used to obtain an additional 2 knots to reinforce the fixation of the LHB to the glenoid rim. Reproduced from de Campos Azevedo and Ângelo<ref name=":28" />, with permission.]]

Labral Repair
With the arthroscope through the posterior portal, a standard Bankart repair is performed using 2-3 suture anchors. The anchors are placed on the glenoid rim at 3, 4, and 5 o’clock to enable the retention of the capsulo-ligamentous structures and to re-establish the labral damper effect (Video and Figure).
[[File:1562549775598-lg.jpg|center|thumb|600x600px|Intra-articular view through the posterior portal. Associated capsulolabral repair using 2 to 3 anchors recreates normal articular concavity (bumper effect). The anchors are placed on the glenoid rim between 3 and 6 o'clock, depending on the lesion. ∗ indicates the labrum. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

Postoperative Rehabilitation
Patients are instructed to wear a simple sling for 10 days encouraging rest and reducing the risk of post-operative hematoma formation. Rehabilitation with self-mobilization in elevation and external rotation is allowed from day 0. At 10 days, activities of daily living are allowed and self-mobilization in elevation and external rotation continued. Return to low-risk sports (eg, jogging, cycling, and swimming) is allowed at 6 weeks, and high-risk (throwing and collision) sports at 3 months only after satisfactory clinical and radiographic evaluations confirm satisfactory healing of the coracoid graft. Initially, no physiotherapy is recommended.

====Bony procedures====
In the setting of glenoid bone loss ≥20% of the glenoid diameter an arthroscopic Bankart repair has an unacceptably high rate of recurrence. Burkhart and DeBeer reported a 4% recurrence rate for arthroscopic Bankart repair when glenoid bone loss was <25%. However, with glenoid bone loss ≥25%, the recurrence rate was 67% with an arthroscopic approach. They subsequently recommended a bony procedure procedure in the population with substantial glenoid bone loss.<ref name=":4" />

Treatment is based on patient factors and associated pathology as previously discussed. In general, for patients under the age of 30, primary stabilization following a first traumatic anterior instability episode is offered. Such patients are counseled on the natural history or anterior instability and the potential for subsequent injury. For the majority of patients over the age of 30, nonoperative treatment is advised with standard sling immobilization for three weeks followed by progressive strengthening and return to activities. For such patients with persistent weakness or recurrent instability a magnetic resonance imaging (MRI) or MRI arthrogram is obtained to evaluate for an associated rotator cuff tear and stabilization is performed.

In consideration of the current literature, the following indications for osseous reconstruction procedures of the glenoid concavity can be recommended: - Substantial erosion-type defects (type IIIb), which constitute the instability-associated main pathology. - Chronic fragment-type defects (type II), where the glenoid area and concavity cannot be reconstructed by mobilization and refixation of the fragment. - In the rare patient with an acute, non-reconstructible, multifragmented glenoid fracture (type Ic). - In cases of revision surgery, e.g. after failed soft-tissue stabilization, a glenoid augmentation procedure is recommended also for smaller bony defects (type IIIa).

=====Open Latarjet=====
In 1954, Latarjet reported a coracoid transfer procedure in which the inferior aspect of the coracoid was secured to the anterior glenoid. The excellent stability of this procedure is obtained by a triple effect first proposed by Patte:<ref>Patte D, Debeyre J. Luxations récidivantes de l’épaule. Tech Chir Orthop Paris: Encycl Med Chir 1980:44–52.</ref>

1) the sling effect of the conjoint tendon when the arm is abducted and externally rotated, 2), the ‘‘bony effect’’ that increases or restore the glenoid anteroposterior diameter (Figure), and 3) the retensionning of inferior capsule to the stump of coracoacromial ligament, rending the coracoid extra-articular.
{| class="wikitable"
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![[File:1562549774884-lg.jpg|center|thumb|412x412px]]A
![[File:1562549775216-lg.jpg|center|thumb|300x300px]]B
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''Illustration of the three effects A) the sling effect, B) the bony effect and C) the retensioning of the capsule. Courtesy of Gilles Walch.'' 

When the arm is at an end-range position, the sling effect contributes 76-77% at different loads and the capsule the remaining 23-24% to the stabilization of the humeral head. At the mid-range position of the arm, the sling effect facilitates 51-62% and the bone block 38-49% of the stability. The sling effect, therefore, seems to constitute the number one stabilizing mechanism of the Latarjet procedure at both, the mid- and end-range of motion. The internal-external range of motion is thereby not significantly impaired.<ref>Yamamoto N, Muraki T, An KN, Sperling JW, Cofield RH, Itoi E, Walch G, Steinmann SP. The stabilizing mechanism of the Latarjet procedure: a cadaveric study. J Bone Joint Surg Am 2013;95:1390-7.</ref>

The Latarjet procedure is associated with a very low recurrence rate even in the setting of substantial glenoid bone loss and has become the gold standard of treatment in such settings. In addition, this non-anatomic method of anterior glenohumeral stabilization has progressively expanded and is actually the primary technique of choice for many European surgeons, as it prevents recurrent anterior instability in approximately 95 to 99% of cases. This procedure is also favored by some as a first choice in many contact athletes.<ref>Joshi MA, Young AA, Balestro JC, Walch G. The Latarjet-Patte procedure for recurrent anterior shoulder instability in contact athletes. Clinics in sports medicine 2013;32:731-9.</ref>

[[File:1562549775732-lg.jpg|center|thumb|600x600px|Illustration of a partial remodelling after an anteroposterior 2.5 cm tricortical iliac crest bone block. Antero-posterior (A) and Neer (B) view of a right shoulder after iliac crest bone block. Observe on 3 years computer tomography (CT) scan follow-up, the anteroposterior diameter of the glenoid remains supraphysiologic, explaining the efficiency of this open procedure.]]
Surgical technique (Video)
[[File:1563403564475-lg.mp4|center|thumb|300x300px|Video]]

Patient preparation
The patient is positioned in a classical, 40 degrees, beach chair position, preferably under a combination of general anesthesia and locoregional interscalene block to maximize the patient and the surgeon’s comfort. A single prophylactic antibiotic dose is highly recommended, as infectious complications are not uncommon in the proximity of the axilla. The upper limb is draped freely to allow manipulation of the shoulder and placed on an arm board. The operative site, including the sternoclavicular joint medially, is covered with iodine incise drape.

Incision
The incision is performed under the tip of the coracoid process extending 4 to 5 cm distally.
[[File:Gfaddw .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The tip of the coracoid process is palpated, and the incision is performed under the tip of the coracoid process extending 4 to 5 cm distally.]]
The dissection begins at the level of the Mohrenheim fossa, a triangular region just inferior to the clavicle, between the deltoid and pectoralis major muscles which do not contain neurovascular structures. The deltopectoral interval is then opened bluntly with two Richardson retractors, letting the cephalic vein medially.
[[File:Figure 2da a.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The dissection begins at the level of the Mohrenheim fossa, a triangular region just inferior to the clavicle, between the deltoid and pectoralis major muscles, which do not contain neurovascular structures. The deltopectoral interval is then opened bluntly with two Richardson retractors.]]
The Gelpi retractor is placed deep in the approach, while the cephalic vein is retracted laterally. The whole coracoid process with the insertion of pectoralis minor, coracoacromial ligament, and the conjoined tendon (CT) is exposed by placing the Hohmann retractor on its tip.
[[File:Figure 3d a aw.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The whole coracoid process with the insertion of pectoralis minor, coracoacromial, and the CT is exposed by placing the Hohmann retractor on its tip.]]
The pectoralis minor is released from the coracoid process with electrocautery while the arm is internally rotated and adducted.
[[File:Figure 4d ada .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Pectoralis minor (blue arrow) is released from the coracoid process (CP) while the arm is in adduction and internal rotation. CT – conjoined tendon.]]
The upper limb is abducted and fully externally rotated to improve the coracoacromial ligament visualization, which is then released approximately 1.5 cm laterally from its attachment.
[[File:Figure 5da ada .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The coracoacromial ligament (white arrow) is released 1.5 cm laterally from its attachment on the coracoid process (CP). The arm is abducted and externally rotated for 90° to improve its visualization. CT – conjoined tendon.]]
Coracoid graft harvest and preparation
A 90° angled saw blade is used to perform a coracoid process osteotomy at its base as far back as possible but still just anterior to the coracoclavicular ligament, starting superomedialy and proceeding inferolateraly.
[[File:Figure 64v q.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. A 90° angled saw blade is used for coracoid osteotomy, which is performed at the base of the coracoid process (CP) as far back as possible, however still in front of the coracoclavicular ligaments. CT – conjoined tendon.]]
When the coracoid process gets loose, a chisel is meticulously used to complete the osteotomy.
[[File:Figure 7dqwq qd.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The coracoid osteotomy is meticulously finished with a chisel. CP – coracoid process. ]]
The coracoid process is rotated for 180° while being held with a grasper. It is attentively released until the muscle belly is uncovered in order to be easily and safely manipulated. The coracoid process should not be placed outside the surgical field to avoid tension in musculocutaneous nerve neuropraxia. Its undersurface is flattened and slightly decorticated with a saw blade to create a healthy bleeding surface that will precisely conform to the later prepared anterior glenoid.
[[File:Figure 8q q .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The undersurface of the coracoid process (CP) is flattened and slightly decorticated with a saw blade to create a healthy bleeding surface that will precisely conform to the later prepared anterior glenoid.]]
The two 4 mm holes for screw fixation are drilled equally distant from the base and the tip, 1 cm apart and 8-9 mm laterally from the insertion of the coracoacromial.
[[File:Figure 9das as.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Two 4 mm holes for screw fixation are predrilled perpendicularly and centrally in the coracoid graft, 1 cm apart, and 8-9 mm laterally from the insertion of the coracoacromial. ]]
It is essential that the holes are drilled perpendicularly to the surface and centrally to the graft. There are two options for labral fixation, either by transosseous coracoid fixation or by fixation with anchors at the later medial coracoid-glenoid edge. If the surgeon chooses the transosseous coracoid fixation, two holes for later labral fixation are predrilled with a K-wire on the lateral coracoid process bony rim where the coracoacromial inserts, but so that they are placed bellow it and do not pass it. A non-resorbable suture is shuttled through each of them. The coracoid process is retracted medially with the pectoralis major muscle.

Glenoid exposure and preparation
The arm is placed in abduction and external rotation and the subscapularis split between the upper 2/3 and lower 1/3 of the subscapularis is performed by sharply introducing horizontally placed scissors towards the anterior glenoid neck.
[[File:Figure 10Ada s.png|none|thumb|Left upper extremity of a patient placed in a semi beach-chair position. The arm is placed in abduction and external rotation. ]]
[[File:Figure 10Bdaads a.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The subscapularis split between the upper 2/3 and lower 1/3 of the subscapularis (SSc) is performed by sharply introducing horizontally placed scissors through the subscapularis muscle towards the anterior glenoid neck. Then they are rotated for 90°.]]
Then, they are rotated for 90°. Their blades are extended to widen the split, while a Hohmann retractor is placed between the blades on the medial side of anterior glenoid neck. The division is additionally increased with a No. 15 blade.
[[File:Figure 11A.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position.The blades of the scissors are extended to widen the split, while a Hohmann retractor is placed between the blades on the medial side of the AGN. AGN – anterior glenoid neck.]]
[[File:Figure 11B.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The split is additionally increased with a No. 15 blade. SSc - Subscapularis, * - anterior capsule.]]
The superior and inferior parts of the subscapularis are held apart by two Gelpi retractors, one placed superficially and one deeper, while a Hohmann retractor is placed on the inferior aspect of the glenoid neck. The glenohumeral joint's exact location is exposed by reducing the anteriorly dislocated humeral head, and a vertical incision is performed.
[[File:Figure 12.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The exact location of the glenohumeral joint is exposed by reducing the anteriorly dislocated humeral head, and a vertical incision is performed in an inferior to a superior direction to protect the axillary nerve. * – anterior capsule.]]
A Trillat instrument is introduced in the joint to slightly posteriorly subluxate the humeral head to get a better view of the anterior labrum, and a wide glenoid retractor is exchanged with the Hohmann retractor on the medial side of the anterior glenoid to improve the visualization of the anterior glenoid. The labrum is horizontally released at the level of 3 o'clock position, and the release is extended inferiorly until the 5 o'clock position. Two non-resorbable sutures are passed through the superior and inferior half of the released labrum for later labral reconstruction.
[[File:Figure 13.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The labrum is horizontally released at the level of 3 o'clock position, and the release is extended inferiorly until the 5 o'clock position. A resorbable suture is passed through the superior half of the released labrum (white arrow). Afterward, another suture is passed through the inferior half of the released labrum for later labral reconstruction. ]]
A curved osteotome is used to slightly decorticate the anterior glenoid neck from 3 o'clock to 5 o'clock position to a healthy and bleeding flat bone bed.
[[File:Figure 14.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. A curved osteotome is used to lightly decorticate the AGN from 3 to 5 o'clock position to a healthy and bleeding flat bone bed. AGN – anterior glenoid neck.]]
The inferior hole aimed less than 10° away from the glenoid articular surface is predrilled with a 2.75 mm cannulated drill in the anterior glenoid neck, located 8-9 mm from the anterior glenoid.
[[File:Figure 15.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The inferior pilot hole aimed less than 10° away from the glenoid articular surface is drilled first with a K-wire and then with a 2.75 mm cannulated drill in the AGN, located 8 mm from the anterior glenoid. AGN – anterior glenoid neck. G – glenoid.]]
When drilling, it is important to stay as parallel as possible to the glenoid surface, as an angle exceeding ten degrees in the axial plane puts the suprascapular nerve at high risk of lesion at its course on the posterior glenoid rim (Figure).<ref name=":23">Lädermann A, Denard PJ, Burkhart SS. Injury of the suprascapular nerve during Latarjet procedure: an anatomic study. Arthroscopy 2012;28:316-21.</ref>[[File:1562551669419-lg.jpg|center|thumb|591x591px|A) The suprascapular nerve passes through the scapular notch beneath the transverse scapular ligament to enter the supraspinatus fossa and provide motor innervation to the supraspinatus muscle. The nerve then courses distally around the base of the scapular spine (spinoglenoid notch) to enter the infraspinatus fossa and provide motor innervation to the infraspinatus muscle. B) The infraspinatus branches of the suprascapular nerve are at risk during screw placement for Latarjet reconstruction. Reproduced from Lädermann et al., with permission.]]

Coracoid Positioning and Fixation

The coracoid process is retrieved and the two sutures that were previously placed through the labrum are inserted through the two predrilled graft holes if the transosseous labral fixation is underway. The coracoid process is placed at the prepared anterior glenoid neck surface. A K-wire is passed through the lower predrilled coracoid and glenoid hole to position the coracoid process on the anterior glenoid neck. The screw length is measured, and the screw is introduced for preliminary fixation.
[[File:Figure 16.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The coracoid process (CP) is placed at the prepared AGN surface. First, the inferior screw is introduced for preliminary fixation of the coracoid process so that the graft can still slightly rotate around the screw. CT – conjoined tendon.]]
A thin Darrach retractor is used to place the superior part of the coracoid process flush with the glenoid face. Afterward, the superior hole is drilled with a 2.75 mm cannulated drill in the anterior glenoid neck, the length is measured, and the screw is introduced but not fully tightened.
[[File:Figure 17.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. A Darrach (D) is used to place the superior part of the coracoid process flush with the glenoid face. The superior hole is drilled with a 2.75 mm cannulated drill in the AGN, the length is measured, and the screw is introduced but not fully tightened. CP – coracoid process, white arrow – coracoacromial ligament.]]
The anterior labrum is fixed on the coracoid process by tightening the knots of the sutures passing through the labrum.
[[File:Figure 18A.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Reattachment of the labrum (white arrow) on the coracoid process (CP) remains to be done. The labral reattachment (white arrow) has been performed ]]
[[File:Figure 18B.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Reattachment of the labrum (white arrow) on the coracoid process (CP) remains to be done. G – glenoid.]]
Then the coracoid is fully fixed by completely tightening the two partially threaded 4.0 mm cancellous screws. This accomplishes an excellent compression between the coracoid process and the anterior glenoid neck due to the lag-by-design technique. If, however, the surgeon an anchor technique, around two anchors are placed at the medial coracoid-glenoid edge, and fixation of the labrum is performed.

Capsulo-labral reconstruction
Finally, the anterior capsule is reconstructed by the imbrication of the coracoacromial ligament with a resorbable suture. While the operated arm is held in external rotation to avoid the postoperative rotational deficit, the humeral head is reduced posteriorly in the center of the glenoid during adduction, slight anterior forward flexion, and a posterior level push.
[[File:Figure 19A.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Humeral head is anteriorly dislocated.]]
[[File:Figure 19B.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Finally, the anterior capsule (white arrow) is reconstructed by the imbrication of the coracoacromial ligament (CA) with a resorbable suture. It is crucial that during the reconstruction, the arm is placed in adduction, anterior forward flexion, and external rotation and that the anteriorly dislocated humeral head is reduced. ]]
Only then, an adequate capsular tension is expected. The wound is copiously irrigated.

Closure
The wound is copiously irrigated. The lateral tendinous part of the subscapularis is repaired with a non-resorbable suture. A standard layered closure is performed.

=====Arthroscopic Latarjet=====
Surgical Technique
Operations are performed in the usual semi-beach chair position under general anesthesia with an interscalenic block or catheter. Arthroscopic Latarjet are carried out using a total of 5 portals (posterior, anterolateral, anterior, suicide, and superior to access the superior coracoid (Figure 34).
[[File:1562552295999-lg.jpg|center|thumb|600x600px|A) Anterior view, B) posterior view. The modified 5 portals are used for the arthroscopic Latarjet. AL anterolateral, A anterior, S superior, Su suicide portal, P posterior portal. Reproduced from Cunningham et al., with permission.]]
 Intra-articular approach is carried out through the standard “soft spot” posterior portal. The rotator interval is opened, and the internal structures (glenoid defects, humeral defects, HAGL, etc.) are further assessed with the probe. To provide a healthy bed for graft healing, the glenoid neck is abraded between 2 and 5 o’clock with a burr. A release of the subscapularis on 270 degrees and of the lateral side of conjoint tendon are then performed. The two subscapularis nerves and the axillary nerve are only located and not dissected as this may lead to neurological lesions. From a lateral viewing portal, a switching stick is inserted through the posterior approach, passed across the glenohumeral joint at the level of the glenoid defect and then advanced through subscapularis to establish the level of split. From the suicide portal, a modified cannulated subscapularis splitter is advanced on the switching stick to facilitate the split.

The probe is then introduced through the anterior portal to complete the split. The latter is thus done before coracoid osteotomy consequently protecting the plexus. At this point, with the scope in the anterior portal, the coracoid is prepared and then osteotomized with osteotome rather than a burr, in order to keep maximum graft length. The graft is extracted through the suicide portal and prepared outside, as inside debridement and trimming might be less accurate and puts the plexus at risk. The coracoid is then secured on the coracoid positioning cannula and positioned on the glenoid neck flush with the glenoid border. Two long K-wires are inserted through the coracoid positioning cannula, and the glenoid is drilled with a 3.2-mm drill bit. The length of the definitive screw is directly read from the depth gauge on the drill. The fixation is obtained with two 4.5-mm cannulated malleolar screws (Figure).

[[File:1562552292659-lg.jpg|center|thumb|600x600px|A) arthroscopic view and B) postoperative anteroposterior x-ray of a left Latarjet procedure. * indicates the graft fixed on the anterior glenoid. Reproduced from Lädermann et al., with permission.]]

=====Open Bristow=====
Independently of Latarjet, Helfet reported in 1958 a slightly different procedure named after his master, Bristow, where the coracoid with conjoined tendon attached was pressed against the anterior glenoid by suturing it to a slit in the subscapularis tendon instead of a screw.<ref name=":2" />

Despite the frequent synonymous labeling as “Bristow-Latarjet” coracoid transfer, the techniques remain distinct and non-equivalent reconstructive procedures. When differentiating between the coracoid transfer techniques, the stabilizing effect by the Bristow technique is inferior to that of the Latarjet procedure in cases of substantial glenoid bone loss due to the difference in coracoid graft size but also due to the direction of the conjoint tendon (Figure).<ref>Giles JW, Degen RM, Johnson JA, Athwal GS. The Bristow and Latarjet procedures: why these techniques should not be considered synonymous. J Bone Joint Surg Am 2014;96:1340-8.</ref>

[[File:1562552295240-lg.jpg|center|thumb|600x600px|Direction of the conjoint tendon in A) Latarjet and B) Bristow procedure (courtesy of George Athwal). Note that the conjoint tendon (blue arrow) during Latarjet has to go around the inferior subscapularis (dark blue). Contrarily, the conjoint tendon exits directly through the split during Bristow procedure. * indicates the origin of the conjoint tendon. Reproduced from Lädermann et al., with permission.]]

Surgical technique
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=====Arthroscopic Bristow=====
[[File:1562553238652-lg.mp4|center|thumb|600x600px|Video]]

Coracoid Preparation, Drilling, and Osteotomy
The arthroscope is initially maintained in the posterior viewing portal. By use of electrocautery through the anterolateral portal, the rotator interval is opened and the subscapularis is followed medially to the coracoid. During this time, the arm should be internally rotated to relax the subscapularis. The coracoid is dissected and the coracoacromial ligament is released. The anterior portal is established just medial to the coracoid, and the pectoralis minor is released. The undersurface of the coracoid is flattened with a motorized rasp through the anterolateral portal. The coracoid is drilled with a coracoid drill guide, a polydioxanone suture is passed through the bone tunnel, and the coracoid peg button is shuttled in place. Through the anterolateral portal, the coracoid undergoes osteotomy 1.5 to 2.0 cm from its tip.

Glenoid Preparation and Anchor Insertion
The labrum is released from the anterior glenoid neck, and a polydioxanone suture is placed through the labrum at the 5-o'clock position. The anterior glenoid neck is abraded to a flat surface using a motorized rasp and a suture anchor inserted at the 3-o'clock position to be used later for the Bankart repair.

Subscapularis Splitting and Axillary Nerve Protection
By use of switching sticks, the arthroscope is transferred to the northwest portal, the anterior glenoid neck preparation is confirmed, and a short half-pipe cannula is placed through the posterior portal. The glenoid drill guide is inserted over the cannula and placed flush with the glenoid face at the 5-o'clock position. A switching stick retracts the labrum and subscapularis through the west portal, and the glenoid tunnel is drilled from posterior with a 2.8-mm K-wire (the outer sleeve is left in place to facilitate the cortical-button transfer later). The posterior subscapularis spreader replaces the glenoid drill guide and is pushed through the subscapularis muscle along with the 5-o'clock position, at the inferior one-third junction of the subscapularis. An anterior bursectomy is performed through the south portal to identify the “3 sisters” (anterior humeral circumflex vasculature), which are followed to the “2 brothers” (musculocutaneous and axillary nerves). The nerves are carefully protected with a nerve retractor, and the tip of the posterior spreader is slowly opened within the subscapularis muscle. The tendon is split from medial to lateral while the capsule is being preserved, and the anterior subscapularis spreader is inserted through the east portal with its tip medial to the posterior spreader.

Coracoid Transfer and Fixation
By use of a suture retriever through the posterior sleeve, the cortical button and coracoid bone block are transferred through the subscapularis muscle and lie flush with the anterior glenoid neck. This fixation is made using 2 round, 6.5-mm, slightly convex titanium buttons, connecting with a loop of continuous suture, forming 4 parallel strands. The glenoid cortical button is slid over the 4 white suture strands, a sliding-locking Nice knot is tied, and the button is advanced onto the posterior glenoid neck. A specific suture tensioner is used to increase bone compression to 100 N.

Bankart Repair
Using the previously placed glenoid anchor, we complete the labral repair, placing the bone block in an extra-articular position. Additional anchors can be inserted depending on the clinical situation and patient anatomy. The tensioning device is removed posteriorly, and 3 surgeon's knots are tied to complete the coracoid fixation.

=====Eden-Hybinette and Other Free Bone Block Transfers=====
Aiming to reduce donor site morbidity associated with the harvesting of autologous bone blocks, autografts of the iliac crest and distal clavicle and allograft of femoral head and distal tibia have been evaluated (Figure).<ref>Mascarenhas R, Raleigh E, McRae S, Leiter J, Saltzman B, MacDonald PB. Iliac crest allograft glenoid reconstruction for recurrent anterior shoulder instability in athletes: Surgical technique and results. International journal of shoulder surgery 2014;8:127-32.</ref><ref name=":24">Provencher MT, Ghodadra N, LeClere L, Solomon DJ, Romeo AA. Anatomic osteochondral glenoid reconstruction for recurrent glenohumeral instability with glenoid deficiency using a distal tibia allograft. Arthroscopy 2009;25:446-52.</ref><ref>Weng PW, Shen HC, Lee HH, Wu SS, Lee CH. Open reconstruction of large bony glenoid erosion with allogeneic bone graft for recurrent anterior shoulder dislocation. Am J Sports Med 2009;37:1792-7.</ref><ref>Zhao J, Huangfu X, Yang X, Xie G, Xu C. Arthroscopic glenoid bone grafting with nonrigid fixation for anterior shoulder instability: 52 patients with 2- to 5-year follow-up. Am J Sports Med 2014;42:831-9.</ref>

Anatomically, iliac crest bone blocks offer the possibility of a nearly unrestricted graft size, but also the coracoid process was found to be a sufficient graft source to re-establish the anatomy for most glenoid defect cases.<ref>Bueno RS, Ikemoto RY, Nascimento LG, Almeida LH, Strose E, Murachovsky J. Correlation of coracoid thickness and glenoid width: an anatomic morphometric analysis. Am J Sports Med 2012;40:1664-7.</ref>

Provencher et al. described the use of an osteochondral tibia allograft with the advantages of a cartilaginous interface, improved graft availability and an excellent glenoid articular conformity.<ref name=":24" />

Radiologically, successful bony consolidation and a remodeling process of the allografts have been observed, as described for autologous glenoid reconstruction. However, a slightly higher recurrence rates of 0-22% were observed.

[[File:1562555338099-lg.jpg|center|thumb|600x600px|Illustration and arthroscopic intra-operative view of a left anatomic and intra-articular iliac crest bone grafting technique with graft fixation by two bio-compression screws. Reproduced from Lädermann et al., with permission.]]

Surgical Technique
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=====Trillat=====
[[File:Capture d’écran 2020-01-28 à 22.02.11.png|thumb|Native situation]]

[[File:Capture d’écran 2020-01-28 à 22.02.54.png|thumb|Illustration of a shoulder after Trillat procedure]]

[[File:Capture d’écran 2020-01-28 à 22.03.20.png|thumb|Effect of the Trillat procedure with the arm in abduction-external rotation]]

==Rehabilitation==

===Non-Operative Treatment of Acute First Traumatic Dislocations===
Although positioning the arm in external rotation has been recommended, it has now clearly been demonstrated that immobilization of the shoulder in internal rotation after primary, traumatic anterior shoulder dislocation is sufficient.<ref>Vavken P, Sadoghi P, Quidde J, Lucas R, Delaney R, Mueller AM, Rosso C, Valderrabano V. Immobilization in internal or external rotation does not change recurrence rates after traumatic anterior shoulder dislocation. J Shoulder Elbow Surg 2013.</ref><ref>Itoi E, Hatakeyama Y, Sato T, Kido T, Minagawa H, Yamamoto N, Wakabayashi I, Nozaka K. Immobilization in external rotation after shoulder dislocation reduces the risk of recurrence. A randomized controlled trial. J Bone Joint Surg Am 2007;89:2124-31.</ref><ref>Braun C, McRobert CJ. Conservative management following closed reduction of traumatic anterior dislocation of the shoulder. Cochrane Database Syst Rev. 2019 May 10;5:CD004962.</ref>

There is conflicting evidence regarding the length of immobilization required after dislocation but three weeks is typically recommended, followed by physical therapy for strengthening of the rotator cuff and scapular stabilizers. Range of motion of the elbow, wrist, and hand are permitted immediately. Then, closed-chain exercises facilitate rotator cuff function to enhance joint stability and stimulate muscular coactivation and proprioception.<ref>Jaggi A, Lambert S. Rehabilitation for shoulder instability. Br J Sports Med 2010;44:333-40.</ref>

For throwing athletes, a program is initiated and advanced, beginning at three months. A full return to sports is typically permitted at five to six months.

===Rehabilitation Protocol After Bankart and Remplissage Stabilization===
The shoulder is immobilized for four weeks using a sling. Passive and assisted-active exercises are then initiated for forward flexion and external rotation. After six weeks, patients begin strengthening exercises of the rotator cuff and scapular stabilizers. For patients with a remplissage strengthening is delayed until twelve weeks postoperative. Patients are permitted to practice noncontact sports as soon as they recover their range of motion. Full return to throwing or contact sports is usually allowed after six months according to each individual’s functional recovery.

===Rehabilitation Protocol After Dynamic Anterior Stabilization===
Patients are instructed to wear a simple sling for 10 days encouraging rest and reducing the risk of post-operative hematoma formation. Rehabilitation with self-mobilization in elevation and external rotation is allowed from day 0. At 10 days, activities of daily living are allowed and self-mobilization in elevation and external rotation continued. Return to low-risk sports (eg, jogging, cycling, and swimming) is allowed at 6 weeks, and high-risk (throwing and collision) sports at 3 months. Initially, no physiotherapy is recommended.<ref name=":13" />

===Rehabilitation Protocol After Latarjet Reconstruction===
The shoulder is immobilized for ten days using a sling. The patient is asked to stretch in flexion and external rotation at least five times per day. No physical therapy is prescribed. The patient is not allowed to carry with his operated arm or to flex the elbow against resistance during the first six weeks. Activities of daily living are encouraged as comfort permits. At six weeks, non-contact sports are allowed. Return to contact sports is usually possible after three months assuming confirmation of bony union of the coracoid graft.

==Results and Complications==

===Soft tissue procedures (Bankart, Remplissage)===
Arthroscopic Bankart stabilization with use of suture anchors offers the advantage of being minimally invasive, allows assessment of associated pathology, and allows the surgeon to restore anatomy while reattaching the labral lesion and retensionning the glenohumeral ligament. While the short-term outcome of Bankart has been excellent, mid-term reported results show higher rates of recurrent of instability. According to the meta-analysis by Hobby et al., recurrence (dislocation and subluxation) after arthroscopic Bankart repair with suture anchors varies between 0 to 29.6%, with a mean of 8.9%.<ref>Hobby J, Griffin D, Dunbar M, Boileau P. Is arthroscopic surgery for stabilisation of chronic shoulder instability as effective as open surgery? A systematic review and meta-analysis of 62 studies including 3044 arthroscopic operations. J Bone Joint Surg Br 2007;89:1188-96.</ref>

This rate of course varies with patient factors, particularly the amount of bony deficiency. Preoperatively, pitfalls are consequently to underestimate risk factors for recurrence for this surgery. In adolescent contact athletes undergoing arthroscopic labral repair, the overall recurrence rate is 51%. Rugby players who undergo primary arthroscopic shoulder stabilization aged <16 years have 2.2 times the risk of developing a further instability episode when compared to athletes aged ≥16 years at the time of index surgery, with a recurrence rate of 93%.<ref>Torrance E, Clarke CJ, Monga P, Funk L, Walton MJ. Recurrence After Arthroscopic Labral Repair for Traumatic Anterior Instability in Adolescent Rugby and Contact Athletes. Am J Sports Med 2018;46:2969-74.</ref>

Bankart repair combined with Malgaigne (Hill-Sachs) remplissage for large defects of the posterosuperior aspect of the humeral head may be an elegant approach in case of isolated humeral defect. Reported results are promising with a high rate of healing of the posterior aspect of the capsule and the infraspinatus tendon into the humeral defect, and a moderate loss of external rotation with the arm at the side. Moreover, most patients were able to return to sport including those involving overhead activities, around 70% at the same level.<ref name=":20" /><ref name=":21" />

The Malgaigne remplissage is believed to be a posterior capsulotenodesis that acts as a checkrein diminishing anterior humeral head translation and reducing the risk of postoperative redislocation. However, some authors have observed that according to the location of the impaction fracture, the procedure actually corresponds to a capsulomyodesis including the teres minor muscle, rather than a capsolutenodesis as classically described (Figure).
[[File:1562556949052-lg.jpg|center|thumb|600x600px|Posterior view of a right shoulder specimen after rotator cuff repair and Malgaigne (Hill-Sachs) remplissage (three lower knots). Note the proximity of the superior knot to the infraspinatus muscle (black arrow). The two inferior knots perforate the teres minor muscle (white arrow) realizing a capsulomyodesis.]]
 Concerns about remplissage may include the potential muscle lesion to the external rotators, increased cost, and increased difficulty and operative time. Yet, beyond a slight loss in postoperative external rotation, there is no documented additional complication to remplissage.

===Open Bone Block Procedures===
Open anatomical bone grafting procedures show very good clinical mid- to long-term results. With this procedure return to sports activities is possible for at least 83% of patients regardless of the size of glenoid defect. In a study of 107 patients, Lädermann et al. reported a mean postoperative Walch-Duplay score of 93, good or excellent results in 97% of cases, and 95% of patients very satisfied or satisfied with their outcome.<ref name=":14" />

However, complications exist both in the short- and long-term. A systematic review of 30 studies with a total of 1658 coracoid transfers, also including more recent surgeries with shorter follow-up periods, reported a low recurrence rate of 6.0%. The arthropathy rates is also reduced to 17-36% compared to the original procedures. A systematic review of 30 studies, comprising a total of 1658 open coracoid transfers, recorded graft non-union or postoperative graft migration (10.1%), hardware complications (6.5%), instability (6.0%), graft osteolysis (1.6%), infection (1.5%), nerve palsy (1.2%), intraoperative fractures (1.1%) and hematoma (0.7%) with a revision surgery conducted in 4.9% of the cases. Hardware problems were identified as the most frequent reason for revision surgery. In addition to failure of stabilization, hardware or graft malpositioning and respective screw breakage, loosening or migration is attended with a high risk for soft tissue as well as articular surface damage.<ref name=":22">Butt U, Charalambous CP. Arthroscopic coracoid transfer in the treatment of recurrent shoulder instability: a systematic review of early results. Arthroscopy 2013;29:774-9.</ref>

Regarding the postoperative muscle function, a significant strength deficit of the internal and external rotators was observed in comparison to the contralateral, unaffected shoulder.<ref>Caubere A, Lami D, Boileau P, Parratte S, Ollivier M, Argenson JN. Is the subscapularis normal after the open Latarjet procedure? An isokinetic and magnetic resonance imaging evaluation. J Shoulder Elbow Surg 2017;26:1775-81.</ref>

Risk of neurological impairment of the musculocutaneous nerve can be reduced by gently manipulating the coracoid process during preparation and avoiding an excessive medial dissection.<ref>Clavert P, Lutz JC, Wolfram-Gabel R, Kempf JF, Kahn JL. Relationships of the musculocutaneous nerve and the coracobrachialis during coracoid abutment procedure (Latarjet procedure). Surgical and radiologic anatomy : SRA 2009;31:49-53.</ref>

The suprascapular nerve is at risk posteriorly during screw insertion and can be protected by parallel placement of the screws within 10 degrees of the glenoid surface in the axial plane (Figures).<ref name=":23" />
[[File:1562556944819-lg.jpg|center|thumb|500x500px|The infraspinatus branches of the suprascapular nerve are at risk during screw placement for Latarjet reconstruction when a divergence of more than 10 degrees between the screws and the glenoid surface in the axial plane is noted. Photograph showing intimate proximity between screws placed for Latarjet procedure and suprascapular nerve. Reproduced from Lädermann et al., with permission.]]
[[File:1562556938948-lg.jpg|center|thumb|459x459px|Schema of screw and spinoglenoid notch orientation. (A) Axial view. The medial-to-lateral orientation was recorded by measuring the angle of the screws (α 1 angle) and of the spinoglenoid notch wire (β1 angle) relative to the glenoid plane. (B) Sagittal view. The superior-to-inferior orientation was determined by measuring the angle of the screws (α2 angle) and the spinoglenoid notch (β2 angle) perpendicular to the glenoid. (CG, coracoid graft; G, glenoid; HH, humeral head; SN, suprascapular nerve.). Reproduced from Lädermann et al., with permission.]]
[[File:1562556945397-lg.jpg|center|thumb|600x600px|Axial (A) and anteroposterior (B) plain radiographs of a left shoulder. The two screws diverge from the plane of the glenoid, pointing in direction of the spinoglenoid notch. A magnification (C) of the axial view demonstrates poor contact (white arrow) between the glenoid and the graft (delimited by red dotted line). Parallel screws would have led to better contact and a lower risk of suprascapular nerve injury]]
 

===Arthroscopic Bone Block Procedures===
Similarly, very good short-term results are achieved after arthroscopic glenoid rim reconstruction without events of postoperative redislocation and the advantage of subscapularis muscle preservation.<ref name=":25">Anderl W, Pauzenberger L, Laky B, Kriegleder B, Heuberer PR. Arthroscopic Implant-Free Bone Grafting for Shoulder Instability With Glenoid Bone Loss: Clinical and Radiological Outcome at a Minimum 2-Year Follow-up. Am J Sports Med 2016;44:1137-45.</ref><ref name=":26">Kraus N, Amphansap T, Gerhardt C, Scheibel M. Arthroscopic anatomic glenoid reconstruction using an autologous iliac crest bone grafting technique. J Shoulder Elbow Surg 2014;23:1700-8.</ref>

At present, however, merely short-term results of the arthroscopic techniques are published and only by the pioneers of these techniques. Following the arthroscopic coracoid transfer techniques, recurrence rates of 0-2% were observed after short- to mid-term follow-up investigations.<ref>Boileau P, Thélu CÉ, Mercier N, Ohl X, Houghton-Clemmey R, Carles M, Trojani C. Arthroscopic Bristow-Latarjet combined with bankart repair restores shoulder stability in patients with glenoid bone loss. Clin Orthop Relat Res 2014;472:2413-24.</ref><ref>Dumont GD, Fogerty S, Rosso C, Lafosse L. The arthroscopic latarjet procedure for anterior shoulder instability: 5-year minimum follow-up. Am J Sports Med 2014;42:2560-6.</ref><ref>Zhu YM, Jiang C, Song G, Lu Y, Li F. Arthroscopic Latarjet Procedure With Anterior Capsular Reconstruction: Clinical Outcome and Radiologic Evaluation With a Minimum 2-Year Follow-Up. Arthroscopy 2017.</ref>

The arthroscopic approach is, however, quite challenging and requires a lengthy learning curve. When directly comparing the arthroscopic and open techniques, a similar functional outcome and patient satisfaction were achieved, but screw placement inaccuracy, persistent apprehension, recurrence rate and complications were higher for the arthroscopic approach.<ref>Cunningham G, Benchouk S, Kherad O, Lädermann A. Comparison of arthroscopic and open Latarjet with a learning curve analysis. Knee Surg Sports Traumatol Arthrosc 2016;24:540-5.</ref>

A slightly reduced percentage of graft non-union or postoperative graft migration (8.1%), hardware problems (2.3%), instability (1.7%) and nerve injury (0.6%) was recorded, while the rate of osteolysis (4.1%) increased. Conversion to an open approach had to be conducted in 3.5% of the surgeries. However, a smaller number of cases conducted by fewer surgeons is available for evaluation of the arthroscopic approach. Larger case numbers by different surgeons and long-term results are therefore required to validate these first positive outcomes.<ref name=":22" />

===Remodeling of the Graft With Bone Block Procedure===
Regardless of the bone grafting technique employed, whether an implant-free or screw-based fixation method, a remodeling process according to Wolff’s law is observed with successful reconstruction of the anatomical pear-shaped glenoid configuration. Approximately 60% of the entire coracoid graft has been observed to undergo osteolysis. The superficial part of the proximal coracoid is predominantly affected, while the deep portion of the distal coracoid aspect showed the least osteolysis and best osseous union.<ref>Di Giacomo G, Costantini A, de Gasperis N, De Vita A, Lin BK, Francone M, Rojas Beccaglia MA, Mastantuono M. Coracoid graft osteolysis after the Latarjet procedure for anteroinferior shoulder instability: a computed tomography scan study of twenty-six patients. J Shoulder Elbow Surg 2011;20:989-95.</ref>

For the free bone grafting procedures, a partial extra-articular resorption of the initially oversized glenoid reconstruction may lead to restoration of the anatomic glenoid configuration over time in terms of a remodeling process (Figure).<ref>Moroder P, Hirzinger C, Lederer S, Matis N, Hitzl W, Tauber M, Resch H, Auffarth A. Restoration of anterior glenoid bone defects in posttraumatic recurrent anterior shoulder instability using the J-bone graft shows anatomic graft remodeling. Am J Sports Med 2012;40:1544-50.</ref><ref name=":26" />
[[File:1562557690817-lg.jpg|center|thumb|600x600px|Three-dimensional computer tomography reconstruction displaying an erosion-type defect (type III) before surgery (Figure 45 a), immediately after reconstruction using a free iliac crest autograft (Figure 45 b) and one year postoperatively (Figure 45 c) after completion of the remodeling with restoration of the anatomical glenoid configuration. Reproduced from Lädermann et al., with permission.]]
===Complication due to harvesting process of the iliac crest===
In comparison to the coracoid transfer procedure, free bone grafting techniques offer the advantage with potentially less severe complications. Complications of autologous bone grafting are predominantly associated with the harvesting process of the iliac crest bone block including pain, hypoesthesia and hematoma observed in 0-13% of the patients. Attempting to reduce donor site morbidity, current studies are evaluating the use of allogeneic bone material as an alternative to autografts. Further complications reported after open autologous iliac crest bone grafting comprise hardware failure (0-4%), shoulder hematoma (0-4%), subscapularis insufficiency (0-3%), graft fracture (0-2%), infection (0-2%) and adhesive capsulitis (0-2%).<ref>Auffarth A, Schauer J, Matis N, Kofler B, Hitzl W, Resch H. The J-bone graft for anatomical glenoid reconstruction in recurrent posttraumatic anterior shoulder dislocation. Am J Sports Med 2008;36:638-47.</ref><ref>Deml C, Kaiser P, van Leeuwen WF, Zitterl M, Euler SA. The J-Shaped Bone Graft for Anatomic Glenoid Reconstruction: A 10-Year Clinical Follow-up and Computed Tomography-Osteoabsorptiometry Study. Am J Sports Med 2016;44:2778-83.</ref><ref>Scheibel M, Nikulka C, Dick A, Schroeder RJ, Gerber Popp A, Haas NP. Autogenous bone grafting for chronic anteroinferior glenoid defects via a complete subscapularis tenotomy approach. Arch Orthop Trauma Surg 2008;128:1317-25.</ref><ref>Steffen V, Hertel R. Rim reconstruction with autogenous iliac crest for anterior glenoid deficiency: forty-three instability cases followed for 5-19 years. J Shoulder Elbow Surg 2013;22:550-9.</ref><ref>Warner JJ, Gill TJ, O'Hollerhan J D, Pathare N, Millett PJ. Anatomical glenoid reconstruction for recurrent anterior glenohumeral instability with glenoid deficiency using an autogenous tricortical iliac crest bone graft. Am J Sports Med 2006;34:205-12.</ref>

An investigation of 6449 patients reported an overall donor site morbidity rate of 19.4% after iliac crest bone harvesting including infections, chronic pain, fractures and nerve injuries at the harvesting site.<ref>Dimitriou R, Mataliotakis GI, Angoules AG, Kanakaris NK, Giannoudis PV. Complications following autologous bone graft harvesting from the iliac crest and using the RIA: a systematic review. Injury 2011;42 Suppl 2:S3-15.</ref>

The currently published studies evaluating arthroscopic autologous iliac crest bone grafting reported a singular case of donor site morbidity and one case of graft fracture in the 30 patients treated.<ref name=":25" /><ref name=":26" />

===Dislocation arthropathy===
Another complication is the development of dislocation arthropathy with a rate similar to other type of procedures (Figure).<ref>Hovelius LK, Sandstrom BC, Rosmark DL, Saebo M, Sundgren KH, Malmqvist BG. Long-term results with the Bankart and Bristow-Latarjet procedures: recurrent shoulder instability and arthropathy. J Shoulder Elbow Surg 2001;10:445-52.</ref>
[[File:1562557685456-lg.jpg|center|thumb|300x300px|Illustration of the three stage of dislocation arthropathy according to Samilson. Courtesy of Gilles Walch.]]
Even if the development of dislocation arthropathy is concerning (around 30%) (Figure), it is rather associated with the disease rather than to the surgery itself.
[[File:1562557685288-lg.jpg|center|thumb|600x600px|A) Anteroposterior plain radiographs of a left shoulder in a 32 year-old woman presenting with recurrent dislocations. Dislocation arthropathy Samilson B is obvious. B) CT scan of the same shoulder demonstrates significant glenoid and humeral bone loss.]]
While the precise cause is unknown, surgery in patients older than 40 years of age, a prolonged period between the initial dislocation and surgery and a lateral overhang of the transferred coracoid process in relation to the glenoid rim have been identified as risk factors. Contrarily, hyperlaxity was observed to be a protective factor against development of a dislocation arthropathy, which may be explained by the lower glenohumeral contact pressures.<ref name=":14" />

===Pull-out===
Anchor (Bankart repair) or screw (Latarjet, Bristow, free graft transfer) pull-out may happen (Figure).
[[File:1562557690266-lg.jpg|center|thumb|600x600px|A) Radiographs of a left shoulder ten days after a Latarjet reconstruction. The patient has been allowed to remove sling but not to do sport. B) The patient ignored the recommendation and was immediately jogging. He returned five hours after the last examination. Controlled radiographs revealed pullout of the graft due to contraction of the short head of the biceps on the coracoid graft.]]
 

==What would Codman have thought about this?==
The role of the supraspinatus in dislocation...

CHAPTER IX
THE ROLE OF THE SUPRASPINATUS IN DISLOCATIONS AND FRACTURES OF THE SHOULDER JOINT

THIS chapter does not aim to be an exhaustive treatise on fractures and dislocations of the shoulder, although a very large number of articles have been studied in order to compile it. During the summer of 1928, Dr. T. W. Stevenson reviewed the literature for me, with especial effort to find to what extent the bursa and the short rotators had been referred to. At about the same time, I took advantage of the service of the Library Bureau of the American College of Surgeons, with the request that they find for me all the references they could concerning rupture of the supraspinatus tendon. After a careful search they were unable to find any articles whatever which were devoted to the subject, although occasionally they found references to rupture or avulsion of the tendons in cases of dislocation on which operations had been done.
So far as I know there is no record in the literature of what I call the "Pivotal- Paradox," described on page 43. I, myself, did not understand this paradox when I started to write the book, and only gradually puzzled out its meaning and significance. Certainly none of the authors, who have written on dislocations and fractures in this region, seem aware of the facts that in complete elevation of the arm almost no rotation can occur and that the extent of rotation diminishes as the arm is elevated. The lack of this knowledge of normal functions seems to me to render most of the previous explanations of the mechanism of dislocations and fractures in this region nearly worthless, for several important deductions can be made by the use of these facts. I have consequently eliminated much that I had previously written about the opinions of authorities.
In complete elevation there is only one possible geometric relation of the two units, i.e., the head of the humerus and its tuberosities, with the scapula and its processes. No matter in what degree of rotation you start to raise your arm and no matter in what plane you raise it, the capacity for rotation will be less and less as the arm ascends until, in complete elevation, tuberosities and processes will be locked in a fixed position. In this fixed position the articular head of the humerus will be shown by X-ray in the antero-posterior view, to face nearly outward, and in the lateral view to face somewhat forward, i.e., it actually faces obliquely outward and forward, exactly reversed from its anatomic position. The axis of the condyles of the lower end of the humerus becomes antero-posterior, with the internal condyle pointing forward. The humerus has rotated inward 90° and has become inverted. You may say that the angle between the shaft and the axis of the neck gained 45° by inversion and then 45° by external rotation, or you may say, if you please, it first gained 45° by internal rotation and then another 45° by inversion. Do not proceed with this chapter until you are sure that you have understood this paragraph, even if it is necessary for you to take a humerus in your hand.
The reader must bear in mind that this pivotal position may be assumed by extension of the scapula on the humerus as well as by extension of the humerus on the scapula. For instance, the arm may be in this position when a boxer delivers a telling punch, "putting his body into it." However, the true pivotal position implies that the clavicle is elevated and carried backward to its extreme limit when the arm is elevated to its extreme degree. In other words, the scapula and humerus may move into their share of the pivotal position without the clavicle rising (subordinate pivotal positions), but the arm, to attain complete elevation and the true pivotal position, must be raised to the side of the head.
The scapulo-humeral joint will lock in different positions according to the degree of rotation of the humerus, in a very queer way. (See Figs. 25 and 26.) There can be very little scapulo-humeral abduction with the humerus in full internal rotation; i.e., when the forearm is behind the back, even if clavicle is raised. Starting with your clavicle held down, try elevation of your arm in either internal or external rotation, and then compare the extent of motion when you start with it raised. You will see why authors have differed so much in their estimates of the degree of motion possible in the scapulohumeral joint. To get the maximum you must perform elevation in internal rotation in the sagittal plane or external rotation in the coronal plane; you cannot interchange. These motions cannot be estimated by putting the scapula of a cadaver in a vise, because in life they vary with the relative positions of humerus, scapula and clavicle.
It is as if the secondary humeral joint, limited by the acromion and coracoid, were built with two long sloping sides meeting at an angle above the head, so that when the arm is raised in any plane it eventually comes to rest in the trough formed at the angle of the coronal and sagittal planes and cannot rotate any more. Nature's command is: "Make any combination of elevation and rotation within this enclosure which you wish, but if you exceed these normal limits, you may dislocate or fracture your humerus."

A logical conclusion from these facts is that in whatever way a forward or lateral fall occurs, no strain will come on the scapulohumeral structures until they assume this locked position in complete elevation, provided rotation of the humerus is unhindered as the arm is being elevated. In other words, when the arm is being elevated in mid-rotation in the sagittal plane and arrives at a little above a horizontal position, if inward rotation be prevented, some structure must give, provided the fall continues in this plane. This is exactly reversed in the case of falls in the coronal plane, for when outward rotation is prevented, some break in bone or soft parts must occur. The latter example is the usual one in dislocation and fracture of the head of the humerus.
Let us imagine the same forces applied in another way, i.e., by leverage on the arm when the body is in a fixed position, for mechanically it is the same problem whether the falling patient exerts force on the outstretched arm, or the fixed patient has the same force applied to the arm. Let us imagine the arm thrust into a pipe and force applied to that pipe as in the following diagrams, by lifting its free end up from the plane of the paper- (Fig. 53.)
In making an effort to remember the combinations of rotation and elevation of the arm which may or may not be made, a simple formula is this: evolution has fitted the human animal to fall directly forward on his face with his arm and forearm in almost any position in relation to his body, but, once he has fallen, his arm and forearm cannot be brought much behind the plane of his body in the position in which he lies on his face on the ground, without in some way raising his body.
We may learn a good deal about the shoulder joint from watching the maneuvers of a wrestler endeavoring to turn his opponent from a face-downward position. These maneuvers are essentially the same as those represented in the diagrams above, that is, they depend on getting the flexed forearm in such a position that a little more leverage would break or dislocate the humerus, unless the prone wrestler does permit his body to be raised. Of all the possible positions in which his forearm and arm can be pulled backward, that in which the arm lies at the side will show the greatest backward mobility, i.e., "dorsal flexion."
In lateral falls, when the abducted arm is held behind the plane of the body, the same dislocating or breaking strains that the wrestler endeavors to secure may be produced, the force being supplied by gravity. Moreover, falls will be more violent and sudden, and perhaps catch the muscles when relaxed, instead of having the opposing muscles offer resistance by the voluntary tension which the prone wrestler can assume.

FIGURE 53. LEVERAGES CAUSING ANTERIOR AND POSTERIOR DISLOCATIONS
In interpreting this plate the reader must imagine the arm thrust into a pipe, and he must suppose that the patient's body remains in ironlike rigidity while the outer end of the pipe is raised directly upward from the plane of the paper. Provided the body remained rigid and the tube were raised in this manner, a dislocation of the head of the humerus or fracture must occur. Typical backward or subacromial dislocation would occur in Figures 2, 6 and 7, while subcoracoid dislocation would occur in the other positions.

As in simple frontal falls, so in simple dorsal falls no dislocation of the shoulder will occur, if the arms are free, for we may lie on our backs with our arms in any position anterior to the coronal plane of the body. Even when the dorsal fall occurs with the forearm behind the back or behind the head, dislocation is unlikely.
Thus we reach the conclusion that only headlong, lateral, or semi-lateral, sudden falls can produce the forced elevation combined with prevention of rotation which is necessary to cause anterior luxation of the shoulder joint.
It is possible to conjecture, from a more detailed study of the questions just considered, which forms of dislocation, or varied locations of the lines of fracture, will occur in the shoulder if the lines of force are known. For instance, it is safe to say that only the results of forces applied as in Cuts 2, 6 and 7, in Fig. 53, may result in subacromial dislocation, while all of the others produce subglenoid dislocation.
To express the writer's belief in another way: anterior dislocations of the humeral head occur after the arm has reached the fixed "pivotal position," or more often by prevention of rotation when the arm is at least above the level of the shoulder and the extent of possible rotation therefore greatly diminished; subacromial displacements occur when the arm is below the level of the shoulder and is rotated internally.
This belief is founded not only on the facts already mentioned, but on two others. The first is the remarkable ability of the arm to rotate quickly. Any one who has done any wrestling will remember how elusive were his opponent's arms, unless his elbows were bent, and how easily they slipped out of his grasp as he endeavored to obtain a "shoulder lock." The second is the utter unreliability of the histories given by patients of falls "on the shoulder." The reader is again referred to p. 10. Patients with these injuries almost always say that they struck their shoulders and do not realize that they fell with their arms elevated, i.e., raised to fend off the ground. The inertia of the body is so great as compared to that of the arm, that even in a sudden fall the arm may be thrust forward or outward before the body reaches the ground. A man must already be hugging something, as a football, under his arm in order to fall on his shoulder.
The fact that the arm rotates readily in a safe direction as it is instinctively raised (i.e., raised in relation to the scapula, although pointing downward) during a fall, means that subconsciously the arm will usually reach the relatively safe pivotal position. Meantime the palm meets the ground and the force becomes disseminated to the various ligaments, muscles and bones of hand, wrist, elbow, shoulder and back, each in turn breaking the fall until the final bony lock in the pivotal position brings the stress to a limit. Even then the pec-toralis, the teres major and latissimus, and finally the clavicle, may still further disseminate the stresses. But notice that in this elevated position the lines of force of these muscles converge toward the glenoid, so that they are not, in this position, functioning as rotators as they do when the arm is at the side. The higher the axis of the humerus the more their power is exerted toward the face of the glenoid in their effort to avert the leverage of the shaft from gaining a fulcrum on the acromial edge. However, while they are in use in fending off the ground, the pectoralis and latissimus are acting also as strong internal rotators. This is the period of danger (Fig. 55), for the pivotal position, once reached, means safety, unless the downward factor in the fall is great. When the arm is in the pivotal position, the broad tendon of the latissimus actually covers the unprotected axillary portion of the capsule and tends to prevent the head from dislocating, although the pull of this muscle is in the main downward. In this position the long head of the triceps, the teres major and the latissimus actually form a support for the lower half of the capsule.

FIGURE 54. ACTION OF PECTORALIS MAJOR IN DISLOCATION
This diagram pertains to the discussion of whether the pectoralis major and latissimus dorsi should be regarded as furnishing a fulcrum in case of fracture of the upper end of the humerus. The contention is made that the pull of these muscles not only does not act as a fulcrum, but to some extent relieves the strain on the surgical neck, by pulling the tuberosities away from the true fulcrum which is the acromion. If these muscles acted as a fulcrum, the power would be applied on the glenoid and would immediately rotate the whole scapula, so that the acromion would become a fulcrum. The writer holds that in such accidents there can be no disruptive force in the region of the head of the humerus unless the acromion does act as a fulcrum.
The diagram further illustrates the fact that the power of the supraspinatus is applied in such a manner as to restrain dislocation, but that in forced elevation of the arm the upper edge of the glenoid acts as a wedge driven in between two points of application of strain. This idea is amplified in Plate IX.

Many authors have contended that besides the obvious bony fulcrums which occur, there may be others momentarily maintained by contracted muscles, which may lead to fracture or dislocation. Perhaps this is true, but I have been able to work out few such mechanical positions. For instance, the lever formed by the humerus when the arm is in the anatomic position, the pectoralis and latis-simus contracted, and outward force applied at the elbow, may be considered either to have its fulcrum on the glenoid or to apply power there, with the pectoralis, etc., as a fulcrum. The latter might be the proper way to consider the problem if fracture occurred in the long arm of the lever, distal to these muscular attachments. It seems more logical to me to regard the applications of muscle pulls as forces acting on the obvious bony fulcrums. However, there can be no doubt that when these muscles are contracted they would tend to prevent outward rotation of the humerus.

FIGURE 55. TRAJECTORY OF CENTER OF GRAVITY
The center of gravity of a person in falling necessarily always has a trajectory formed by the momentum with which he falls forward, combined with that with which he falls downward, and that which is exerted in relation to the median plane. The writer contends that in most instances, dislocations and fractures in the region of the upper end of the humerus take place when the trajectory meets the ground at or posterior to the point of impaction of the elbow, and also internal to this point. If the trajectory came far anterior to the point of the elbow, the arm would be folded to the side, or if it came far posterior to the point of the elbow, the arm would extend harmlessly beside the head. If it came near the median plane or to the opposite side of it, the arm would slip outward into the hammock position. It therefore seems highly probable that most of these fractures happen when the arm is internally rotated by the pectoralis, etc., and the fall is of such a sudden and violent character that the humerus does not have time to rotate.
If the vertical factor in the trajectory were great so that the patient was falling nearly straight, head downward, fracture or dislocation in the pivotal position would occur. The writer believes that in every case there is acromio-humeral contact, and therefore always a subordinate pivotal position (see Fig. 25).

I am not in sympathy with the view of those authors who hold that the contracted pectoralis and latissimus act as a fulcrum to promote dislocation or fracture of the head of the humerus. I think the reverse is true, so far as their adductor action is concerned, for I am convinced that this action merely tends to prevent dislocation, since the force is applied to the long arm of the lever distal to the true fulcrum which is the acromion.
Lack of space prevents elaboration of the following additional reasons which support this conviction.

The directions of the majority of the fibers of the pectoralis
major suggest that -their contraction would bring the head toward
the glenoid from the very start of elevation, i.e., they would directly
oppose dislocation.
In other words, the lower fibers of the pectoralis are inserted higher on the humerus than the upper fibers; thus all fibers of the muscle tend to pull in a line away from the acromion as a fulcrum while the arm is being raised.
The combined power of the adductors would not be enough to break the humerus, if both ends of the latter were fixed. Therefore, their power would not be enough to act as a fulcrum for a fracture in the short arm of the lever, although it might be sufficient in the long arm.
Even if the power on the long arm of the lever'acting through the muscles as a fulcrum, became applied to the glenoid and to the supraspinatus and other opposing muscles, the result would merely tip the scapula so as to apply the acromion as a fulcrum.
Until the acromion became a fulcrum no disruptive force could take place between the scapula and humerus.
If the humerus touched the acromion at all and the pectoralis, etc., applied their power exactly opposite this point, the leverage exerted on the glenoid would not be changed in any way; nor would it be changed much if the point of application were moved a little away from the neutral point on the long arm of the lever. However, that slight change would diminish rather than enhance the tendency to dislocation.
The X-ray shows close apposition of acromion and humerus, when the arms are akimbo, in the salute position and in complete elevation.
The acromion is always the fulcrum, although in the above positions different parts of the acromial edge come in contact with different parts of the circumference of the humeral head. (Fig. 25.)
Although I believe that the pull of the pectoralis and latissimus actually help to prevent dislocation by their action as adductors, I am strongly of the opinion that as internal rotators they actually help to promote dislocation. The reasons may be briefly stated a& follows: On account of the position of insertions of their tendons, to be adductors, they first have to be internal rotators. As adductors they do their best to fend off the ground until the last possible moment when the acromion has begun to be a fulcrum. Meanwhile, as internal rotators, they are drawing the arm into a subordinate pivotal position and thus prevent external rotation, which is the only method of escape for the arm if it must rise in the coronal plane. Thus we can conceive of their having power enough to keep the humerus internally rotated until it is too late for it to turn, although we cannot conceive of their being able to act as direct adductors strongly enough to withstand the falling weight of the body. If, in any case, they instinctively relax in time for rotation to occur, the arm will rise to the side of the head and no harm will have been done. Occasionally, however, the relaxation is too late, or vice versa, the violence is too sudden, and the arm will be caught in internal rotation in or near the coronal plane. It will then be too late for the adductors to relax in order to let rotation occur and thus permit the arm to ascend by the head.
The nearer the bent arm, in internal rotation, lies to the sagittal plane the safer it will be; the nearer the externally rotated arm lies to the coronal plane the safer it will be and vice versa. As a matter of fact, in healthy youth it is astounding how rapidly this instinctive rotation will occur. The football player may be hurled headlong by impact with other players in such a way that his body may be twisting laterally as it falls, yet his outstretched arms fend off the ground just long enough to prevent his breaking his neck, and in spite of the sudden, twisting violence, rotation at the last moment usually avoids dislocation of the shoulder.
Yet occasionally the resultant of all the forces of the fall makes the trajectory of the center of gravity strike posterior to the point of the elbow and to its inner side, while the humerus is internally rotated, and anterior dislocation will occur.
If the reader wishes to go into this in more detail he may force his mind to project a combination of Figures 26 and 55. It is difficult enough to visualize the normal workings of the shoulder joint, but it is still more difficult to foretell the results, on this beautifully adjusted apparatus, of a fall downstairs. Yet I think these general principles usually apply.
On the supposition that our conclusion that the humerus must obtain a fulcrum on the acromion in order to exert a disruptive force to produce dislocation is correct, let us consider what occurs in the inner unit of the shoulder, Figure 8, Chapter I.
The fulcrum on the edge of the acromion obtains its skeletal support, whatever the position of the arm, directly through the clavicle to the sternum. As has been said, not only is upward dislocation of the acromio-clavicular joint prevented by the fact that the clavicular portion of it is superior, but by the strong coraco-clavicular ligaments. Thus the clavicle in any position furnishes a strong radius through which the pressure on the fulcrum is firmly sustained. Moreover, the S shape of the clavicle has been shown to not only withstand great pressure in a line between its two ends, but to have great elasticity when the pressure is released.
I wish to accent again three characteristics of the scapulohumeral joint.

The capsule is necessarily loose.
The upper half is muscular and strong; the lower half is fibrous and weak.
Since the humerus can rotate many degrees (probably 100+) without moving the scapula, any one of the short rotators may receive the chief burden of the strain according to the degree of rotation when the acromion becomes the fulcrum. The following remarks will be based on the supposition that the supraspinatus is uppermost, as in Fig. 9, but would apply equally well when any of the other rotators were directly opposed to the force moving the elbow.
As the elbow rises upward not only is the supraspinatus contracted but the upper edge of the glenoid becomes a wedge in the reentrant angle, between the articular cartilage and inner surface of the supraspinatus. This accounts for the frequency with which fracture of the tuberosity accompanies dislocation. In most cases not only the facet on the tuberosity for the supraspinatus will be carried away, but also a concavo-convex piece of bone comprised of the greater tuberosity and part of the lesser, and extending down to the point where the humerus touches the acromion, and including even the bicipital groove as a whole with its tendon intact. (See Plate IX.)
If the force goes no further we shall have a false dislocation, for the lower part of the capsule being loose and there being no support above, the head will glide over the lower edge of the glenoid and fall into the lower part of the capsule, stretching it downward. Correspondingly, the dislocation will be at once reduced as the arm falls to the side, for it will not be pushed through a hole in the capsule and thus have an impediment to easy reduction.

PLATE IX. FRATURES OF THE TUBEROSITY AND FALSE DISLOCATION
The mechanism of fracture of the greater tuberosity and its relation to false and true dislocations.
a. The pivotal position.
6. When leverage is exerted against the acromion as a fulcrum, the biceps tendon guides the upper edge of the glenoid to enter the sulcus as a wedge, thus tending to chip off the tuberosities. This wedge is not a point but the curved edge of the fibrocartilage backed by the rim of the glenoid.
c. The inferior extremity of the fragment is therefore at the point of impaction of the acromion. The biceps tendon, tuberosity and subacromial bursa remain in their normal relations. A false dislocation of the head may then occur without rupturing the lower part of the capsule because tension is relieved by the rent in the upper portion. The lower part of the capsule, which is normally capacious, will be merely carried beneath the glenoid, as the arm descends.
d. The same lesion with the muscles depicted. A portion of the subscapularis still remains attached to the lesser tuberosity, but most of the greater tuberosity, and part of the lesser, remain in Continuity with the fragment.
e-f. Schematic drawings to illustrate the difference between a false and a true dislocation. False dislocation must necessarily be accompanied by rupture of the upper portion of the capsule, together with fracture of the greater tuberosity or rupture of the tendons. There is no structure except possibly the biceps tendon likely to interfere with its replacement, but in a case of true dislocation where the lower part of the capsule alone gives way, the sides of the capsular rent would tend to become tight around the neck of the bone, when efforts are made at reduction. In the worst cases where the two forms are combined an operation is required.
It seems as if some cases must occur in which the biceps tendon would be freed because the line of fracture might extend down the groove and the tendon would thus be separated from the greater tuberosity, and lie between the fragments. I think it usually remains in contact with both fragments if it is not evulsed from the glenoid by the same violence, in which case it retracts into the groove.

This I believe to be the mechanism in most cases of fracture of the tuberosity, whether the accompanying dislocation is recognized or not. On the other hand, both the bone and the supraspinatus attachment may hold in whole or in part, and be stretched down over the glenoid, until the lower portion of the capsule is tensed and torn and permits the head to slip through it and remain subglenoid, with the torn capsule tense on each side of the surgical neck. This will be the ordinary uncomplicated true dislocation.
Violent falls may produce a combination, first wedging off the tuberosity and then driving the head through the lower capsule.
Other variations may be:
1. Instead of the whole tuberosity being wedged off, the supraspinatus may tear away only the facet of insertion.
2. Evulsion of the supraspinatus at the blue line may occur.
3. Rupture of the supraspinatus may take place just above the palisades.
4. Very rarely a lip may be pried away from the lower edge of the glenoid instead of having the capsular attachment give way. I suspect that this is more apt to occur when the forearm is very much rotated internally and the arm is akimbo.
5. Rupture of the long head of the biceps may accompany true or false dislocation, or any of the above variations.
In general, in types 1, 2 and 3, we may expect additional tearing either toward the side of the infraspinatus or toward the side of the subscapularis, according to the degree of rotation of the humerus on the scapula at the time of the fall.
These are the very obvious lesions which may occur, but I believe the most common complication to be the " rim rents " described in Chapter V, which occur not only with dislocation, but in many cases where these structures are just able to resist dislocation, although the synovia becomes separated from the articular margin and a few inner fibers of the tendon are torn.
Another factor which may resist dislocation remains to be considered—the atmospheric pressure which holds the bursal surfaces together. In the typical false dislocation with fracture of the tuberosity, I do not believe that the relations of roof and floor of the bursa are destroyed. Until air is let into the bursa the surfaces tend to remain in contact. Many a time I have demonstrated this on the operating table. The same is true of the joint. To test in actual pounds the degree of pull required to separate these surfaces remains for some future observer. I feel confident that many pounds of direct pull would be required in the living to separate either bursa or joint to any great extent unless fluid is present. Even when the bursa is opened one cannot pull the joint surfaces apart without undue force unless the supraspinatus is torn, when they fall apart as soon as the air enters. The surface area of the bursa and that of the joint must be very nearly the same, roughly two inches in diameter, each. In X-ray tests one must remember that the cartilages do not show and that the presence of fluid permits separation.
A thorough understanding of what has been said in the preceding pages of this chapter is so important that a summary seems necessary at this point.
1. In spite of the usual histories which patients give of striking on the shoulder, the cause of dislocations or fractures is rarely, if ever, direct, but is usually a backward or downward (i.e., backward and downward in relation to the body as the patient falls) force, acting in the pivotal position, or in a subordinated pivotal position, through the humerus as a lever, with the acromion as a fulcrum, and the weight represented below by the lower portion of the capsule supported by the triceps, latissimus and teres major, and above by the resistance of the supra- and infra-spinatus, the long head of the biceps, and the atmospheric pressure in joint and bursa.
2. During a fall, unless the elbow is maintained in flexion, rotation of the humerus readily occurs; but since no lateral motion at the elbow is possible, fixation of a flexed forearm in a given position may greatly alter the direction of force applied at the shoulder, so that dislocation might occur at a point in elevation short of the pivotal position, but usually above the horizontal. For example, a lateral fall in the coronal plane when the humerus is held in internal or mid-rotation, in such a manner that external rotation is prevented (as by contraction of the pectoralis major), or a somewhat headlong fall in the sagittal plane while internal rotation of the forearm is prevented, might result in fracture or dislocation.
3. It is very unlikely that forward dislocation ever takes place unless the fall is at least somewhat headlong, i.e., one in which the elbow strikes a point anterior to the trajectory of the center of gravity.
4. In most instances subglenoid dislocation must be at first momentarily erect. The descent of the arm into the sling position, in which we usually find it, will be in internal rotation with the head of the humerus still displaced below and anterior to the glenoid, with the subscapularis relaxed and the other short rotators stretched over the glenoid. The long head of the triceps will be between the teres major below and the minor above, and the articular surface of the humerus will face backward on the origin of the long head of the triceps.
5. It seems probable that backward or subacromial dislocation never takes place from forces operating on the arm when it is being elevated, but must occur below the horizontal when the humerus is only abducted to a sufficient degree to permit the flexed forearm to be forced backward behind the body in internal rotation. Vice versa, anterior dislocation usually occurs only when the arm is above the horizontal, although theoretically, if the elbow were at the side and the humerus were rotated outward by the flexed forearm, anterior dislocation might occur from a sudden lateral fall which forced the forearm in external rotation behind the body. This would be a very unnatural way to fall, however.
If we accept the above explanation of the mechanics of dislocation, we may proceed to speculate on the reasons why fracture instead of dislocation often occurs from exactly similar falls. Age seems to be the determining factor, but this factor may be subdivided into two secondary ones, i.e., the relative tensile strength of the structures at different ages, and the relative mobility of the bones in youth and in age.
Assuming stress in the pivotal position:
In early youth the humerus ascends high under the acromion, and as the epiphyseal line is relatively the weakest point, epiphyseal separation will probably occur.
As a rule, in youth and manhood after union of the epiphyses, tendon and muscle and bone are strong relatively to the lower portion of the capsule, so that dislocation will take place. If any fracture occurs it will usually be at the greater tuberosity. Occasionally it will occur at the surgical neck.
In old age the trabecular structure about the base of the tuberosities will be weak; therefore, comminuted fracture will readily occur. If the bone holds, dislocation will usually be accompanied by rupture of the supraspinatus, for the muscles and tendons will be weak and cannot disseminate the force.
The second factor, i.e., the extent to which the head of the humerus may pass beneath the acromion, is also important in determining the seats of fracture in youth and in age.
In childhood the tip of the acromion is soft and cartilaginous, and thus the stress on the bony portion of -the acromion would be met at about the epiphyseal line, although the head of the bone passes far beneath the cartilaginous acromion.

FIGURE 56. EPIPHYSES OF A CHILD'S SHOULDER BONES
Outline drawing from X-ray of child with both arms elevated. By use of a dotted line the figure on the left is made to appear as an anterior view while that on the right appears as a posterior. At this age the tip of the acromion is pure cartilage and does not appear in the film. Notice that the head of the humerus passes beneath the acromion just far enough so that the bony portion of the acromion would gain a point of impact very close to the epiphyseal line. The cartilaginous tip would bend and the breaking force would occur at the epiphyseal junction.
This figure also shows that the line of epiphyseal union of the coracoid is at its base. I have never recognized a separation of this epiphysis. My work has been such that I have seen comparatively few injured children, but I think that it is quite possible that this lesion does occur, and may be detected by characteristic symptoms. It is certainly one of those conditions which we should expect on purely mechanical grounds.

In youth the tuberosity also passes far beneath the acromial edge, and this will bring the fulcrum to bear low down on the surgical neck, just above the attachment of the powerful pectoralis major. Usually dislocation will occur with or without fracture of the tuberosity. Occasionally the surgical neck will give way at the fulcrum.
In the stiff, aged joint, the tuberosity will barely pass beneath the acromion, and impact of the latter will come at the point just below the tuberosities, where the cancellated bone is weak, so that comminuted, intracapsular fracture will usually occur.
It is likely that there may be some changes in the exact lines of these comminuted fractures according to the degree of rotation which the humerus attains at the time of fracture. That is, the acromion will be applied at quite different points on the tuberosity in external and in internal rotation.
Other factors may be important also. For instance, the rapidity of the application of force; the degrees of contraction of the various muscles; congenital or habitual variations in the structure or position of the bones and of other tissues; the weight of the body; many minor circumstances or unusual combinations of any of the above factors. However, the point I wish to make is that the pivotal position is to the human arm in its varied activities as his earth is to the fox. The elusive arm must be driven to its pivotal position to be caught, or tricked by preventing rotation on the way. With continued effort we may always dig the fox out, and with continued backward force we may always break or dislocate the head of the humerus,, although the human arm is as clever in evasive rotation as the fox is in doubling.
There are many other points on which a consideration of the "Pivotal Paradox" is enlightening and which are worthy of study, for a thorough understanding of the mechanics of dislocations must be of help in their diagnosis and treatment. However, it will require many studies by many people before practical experience will cease to be our guide. Whether the deductions I have made above prove to be right or wrong, the following practical facts support them and are confirmed by all writers and by each surgeon in his own experience.
The causes of anterior dislocations are usually headlong or lateral falls with the arms thrust forward to fend off the ground.
The same kinds of falls may also produce the following lesions of the upper end of the humerus:

(1) Separation of the humeral epiphysis.
(2) Fracture of the surgical neck.
(3) Fracture of the tuberosities.
(4) Fracture of the anatomic neck.
(5) Comminuted fractures in which the typical form consists of four fragments; i.e., the two tuberosities, the anatomic head, and the shaft. (See Fig. 60.)

Any of these forms may be complicated by concomitant dislocation of the articular head, whether or not it remains attached to the shaft.
The fractures will be discussed in the next chapter and dislocations in the remainder of this one. However, the two subjects are inseparable and one should realize that both fracture and dislocation occur in many cases which are classed as either lesion. I am inclined to think that a combination is the rule, especially in cases of fracture of the tuberosities, and that many supposedly simple fractures are accompanied by false dislocation of the head which immediately becomes spontaneously reduced. Previous dislocation is evident in cases of complete separation at the anatomic neck in which the head remains displaced, but unless the latter is completely separated, it will be dragged back by the tuberosities, which are rarely dislocated because they are sucked back by the bursa and almost invariably remain attached to the short rotators. In other words, these tendons may rupture without the occurrence of any bone lesion, but if one does occur, the tendons remain attached to the fragment. Only small crumbs of the tuberosities ever become really free even in the most comminuted fractures.
The number of shoulder injuries compared to the total number of industrial accidents reported in Massachusetts during eight years is shown in tabular form. This table is not perfectly accurate, so far as the figures on dislocations and fractures are concerned, because it was not arranged for the particular purpose for which I am using it. For instance, all fractures of the clavicle and all fractures of the humerus are included because no distinctions had been made as to the part of the bone injured. It is probable, therefore, that the number of dislocations is fairly exact, but that the number of fractures of the upper end of the humerus is considerably less than the figure given, and probably in every year less than the number of dislocations. Probably many of the cases which were classed as fractures also had dislocations and vice versa. Although there is a striking tendency toward uniformity of the numbers through the different years, the proportion of dislocations to fractures varies somewhat for the above reasons. It is fairly safe to say, however, that about one-fifth of all shoulder injuries occurring in industry are fractures or dislocations of the upper end of the humerus. It is likely that if we could get similar statistics from the population not engaged in industry, fractures would be more common than dislocations, because fractures in this region usually occur in elderly people. Unfortunately, there can as yet be no statistics to determine how often the supraspinatus is injured as a complication of these so-called major (?) injuries, nor what proportion it forms of the other injuries which are unclassified. I believe that it costs our community more than all the other lesions together, not only because it is so common as the major lesion in fractures and dislocations, but because there are many unrecognized minor cases.

The shoulder is the most frequently dislocated joint in the body. This fact is quite properly generally ascribed to its relative instability. Dislocation of the humerus occurred 108 times in 528 cases of dislocation reported by Eliason, and it has been stated by various authors that forty to sixty per cent of all dislocations are of the shoulder. Many shoulders are probably dislocated and immediately reduced by the patient or his companions as they lift him after a fall, without knowledge that dislocation has occurred.
Dislocations of the head of the humerus have been classified in several ways, although for practical purposes only two classes are of importance, i.e., the forward or subcoracoid, and the backward or subacromial forms. As the latter are rare, "dislocation of the shoulder" usually refers to the former.

The first four varieties in the table are essentially the same. If the tear of the capsule and stretching of the muscle bellies away from their beds-are extensive, the dislocated head can be moved easily from a subglenoid to a subcoracoid or to even a subclavicular position. As has been shown, the erect subglenoid position probably occurs in every case momentarily, as the patient falls with the upraised arm, although depression and internal rotation at once ensue from muscular contraction, causing the arm to assume the position at the side in which we usually find it. Very rarely does the erect phase last long enough to be classified!
Subspinous is merely an extreme degree of subacromial dislocation. It occurs when the infraspinatus has been badly torn from its bed so that a large space under the spine of the scapula accommodates the displaced head. Upward dislocation implies an accompanying fracture of the acromion and is nothing more than a curiosity in extremely severe accidents. I have never seen it.

DIAGNOSIS OF ANTERIOR DISLOCATION

In simple subcoracoid dislocation of the humerus, the well-known signs are as follows:

History of a trauma to the shoulder in which something was felt to give way and a severe, acute, nauseating pain was experienced.
Active and passive movements are limited and painful.
The forearm is held flexed and internally rotated.
The elbow is away from the side and cannot be completely adducted, thus causing the long axis of the shaft to incline upward and inward.
Patient stands inclined to the affected side so as to bring the axis of the humerus to a vertical position.
Measuring from the acromion to external epicondyle, the upper arm appears lengthened.
The anterior axillary fold (on the affected side) is lower.
The shoulder is flattened.
The acromial process is prominent.
The head is palpable under the coracoid.
A soft crepitus can be elicited while manipulating the shoulder.
In other words, the facts to be learned from the history, inspection, palpation, motions and mensuration, plus the aid of the X-ray, will usually make the diagnosis beyond doubt. In fact, the diagnosis is generally so obvious that we must be on our guard not to overlook concomitant injuries and complications. While examining the patient one should take especial note of the circulation of the arm, and of the sensitivity of the skin over the arm and shoulder. The power of the deltoid, rhomboids, clavicular part of the pectoralis major, supraspinatus and infraspinatus, etc., should be carefully noted with a view to detecting paralysis. When the case is typical, the eleven signs are exceedingly plain, but this does not mean that when they are absent there is no dislocation.

It is very important for the reader to understand that all of the above signs, except the first and the last, fail when the articular head has been replaced on the tuberosity, which has itself been displaced into the glenoid. At this point the reader should refer to the history of Case 71, page 288, and study the accompanying diagrams. Our mistakes in diagnosis will occur in these cases where the head of the humerus can hardly be said to be out of place, but is certainly not in place, for the short rotators with the evulsed facets lie between it and the glenoid. (Fig. 58 and Case 115, p. 389.)
The second symptom was absent in Case 115 because the nerves were paralyzed or so retracted as not to be influenced when the arm was moved. The replacement of the head to nearly its normal position had completely removed the third to tenth symptoms and even the eleventh symptom, in this particular case, was absent or very difficult to detect.
Of course, such cases of pseudo-reduction are not common, but they occur now and then, so that we must never fail to bear in mind that cases of dislocation which are not quite satisfactory may become extremely unsatisfactory, if the supraspinatus or other short rotators are torn, or have dragged the facets toward the glenoid.
Treatment. The main therapeutic principles are: reduction, fixation and gradual return to function.
Reduction in most cases can be obtained by the Kocher or by the Astley Cooper traction methods. These procedures are too well known to describe in this text. The Kocher method is most generally used because much less force needs to be exerted, and hence less trauma should occur during the reduction. However, as Kocher himself said in his original article, it does not always work and it is sometimes necessary to use the Astley Cooper method.
Much has been said concerning the optimum position in which to maintain reduction. This would seem to suggest that the ideal position had not been found. Some modern authors, notably Stevens, are of the opinion that the arm should be put up in abduction and external rotation.
A simple way of obtaining abduction and external rotation is to put the patient in recumbency, and fasten the hand to the head of the bed. A suitable ambulatory splint can be used, or both methods in conjunction. A splint maintaining abduction and external rotation is cumbersome, and attracts a great deal of attention. The ordinary airplane splint abducts, but internally rotates the arm. Abduction and external rotation put the patient in the position of a traffic officer stopping a line of cars. The writer does not advocate this abduction treatment, and prefers not to fix the arm at all.
The advocates for maintaining the arm in the sling position after reduction, contend that the torn capsule heals better because it is relaxed. This seems reasonable, unless the rent is longitudinal, in which case its edges would be approximated better in abduction. It has never been determined positively whether rents in the capsule are usually longitudinal or transverse. Some writers claim that the capsule is torn from the forward edge of the glenoid, and my opinion is that this is the usual condition, for this only means the tearing of the pillars which form the opening of the bursa subscapularis. More observations of cases where death has occurred from the same accident as that which dislocated the limb are much needed. If we knew in general how the capsule is usually torn, the answer to the question of whether to maintain adduction or abduction would be much more plain.
The writer believes that at present there is too great a tendency to confine the arm after reduction. It would seem more logical to let the patient use his arm a little—even to urge him to do so, in order that debris and blood clot may work out of the joint capsule into the areolar tissue, where they would be readily absorbed. If the capsule were emptied of the blood clot, it would seem that it would be more likely to have its edges fuse together again without leaving any distortion or undue irregularity. On the other hand, I believe that motion should not be forced for fear of tearing edges which are beginning to unite. For those who think this policy too radical, it would be safer to treat most cases in the sling position than in the abducted one, unless the surgeon were very well versed in the study of the shoulder joint. I think stooping exercises should be begun at once and continued daily in any case. We should use fixation only for comfort, and this means very little, for one may be sure that if there is severe pain after reduction some complication exists.

Prognosis. It would seem an easy thing to make a prognosis in cases of dislocation, but as will be seen shortly, complications are frequent, often unrecognized, and greatly modify the period of disability. A fair prognosis in uncomplicated cases would seem to be a return to normal function in from four to eight weeks. However, complications are, I am sure, more frequent than is generally realized.

FIGURE 57
X-rays of the case alluded to in the text in which the articular head had become displaced beneath the deltoid and was excised through a sabre-cut incision. This patient recovered with a useful arm, and was able to play excellent golf for many years afterwards. Undoubtedly fracture and dislocation occurred at the same time, and the head was left behind in the erect phase of dislocation, when the arm came to the side. The articular surface remained in nearly the position which it occupies in normal elevation. It seems possible that if this fact is recognized in similar cases, reduction might be accomplished by again placing the shaft in elevation, opposing the raw surface of the articular head to that of the tuberosity, and holding them together while the arm is brought to the side in the coronal plane.
Figure a, before operation.
Figure b, a few months after operation. The acromion, which had been sawed across for the sabre-cut incision, has been wired about two steel pegs.
Figure c, taken nineteen years later, when the patient was eighty. There had been no trouble from the wire or pegs in the intervening years. At this time motion in the joint still persisted, but "was very limited in degree. However, it was sufficient to permit a slight amount of abduction and rotation, which permitted him to use his arm freely for ordinary purposes. Although this operation was successful in restoring a fair degree of usefulness, if I were obliged to operate again for such a condition I should not remove the articular head, and would endeavor to reconstruct a normal joint, perhaps employing Dr. Nicola's suggestion of anchoring the articular head by means of the biceps tendon. Before incising, I should hyperelevate the arm in internal rotation in order to appose the fractured surfaces.

Gubler, in a study of insurance records of 252 workmen's compensation cases, states that recovery occurred in 94.1% of the cases after an average of thirty-eight days of treatment. Another investigator, Kuttner, reports a far different experience. He was able to trace fifty-four uncomplicated cases from among 168 treated during the previous five years. Only seven (13%) had regained full use of the limb without loss of strength or motion. In fourteen (26%) the range of motion was complete, but the strength was reduced one-half or more. The remaining thirty-two (61%) had some loss of motion, which in twenty-six amounted to inability to raise the elbow laterally above the level of the shoulder. He states that all of these cases were uncomplicated (which we doubt), and had been treated in the hospital by immobilization for a week, followed by massage and mechanotherapy for two to three months. Goebel reports similar unfavorable results on twenty-four patients. Twelve had full function, but subjective complaints. Twelve had limitation of motion. Lexer reports forty cases; ten with complete restoration, fifteen with some limitation, fifteen with pain and loss of strength.
These reports are self-explanatory, and coincide with my observation of results obtained in general hospitals. The conclusion is that most of these patients received other injuries at the time of the accident or during treatment. I believe that uncomplicated cases tend to recover in about four weeks, unless interfered with by injudicious treatment, such as prolonged fixation.

Complications. Injuries to other structures about the joint are common and students should be most thoroughly warned of this fact. It is not so much that these complicating lesions are difficult to detect at the time of the first treatment, but that they are not suspected. It is a fact that these complicating lesions do often exist and do maintain disability and pain long after the joint itself has returned to normal, yet there is no organized effort of our profession to correct this condition. Industrial cases may be labelled malingerers, psychoneurotics, hysterics, or cases of traumatic neuroses, because of this prolonged disability with few detected physical signs. The five common complications of dislocation are the following:

Fracture of tuberosities.
Avulsion of the facets, or rupture of the tendons.
Fracture of the glenoid rim of the scapula.
Injury to the brachial plexus.
Rupture of the axillary artery or of other vessels.
Fracture of the greater tuberosity has hitherto been thought to be by far the most common injury accompanying dislocation. Graessner found the greater tuberosity broken twenty-four times in forty-eight dislocations, but in many of them the fragment was only a small scale of bone, indicating an avulsion of the tendon. Delbet found it in twenty-two out of one hundred and ten cases. Dollinger in five out of thirty-nine. Goebel twenty in forty-three cases. Schlaepfer found it eight times in one hundred and twenty cases, or 7.4%. Gubler reports it in eighteen out of two hundred and fifty-two cases, or 7.1%. Gubler also reports ten cases of other bone injury, and ten of nerve injury in his series. In my opinion, many of the cases where only a small facet is torn away should be classed with supraspinatus injuries rather than with fractures of the tuberosity, because they result in free communication between the joint and the bursa.
The bone injuries are generally easy to diagnose if looked for. The typical signs of fracture, especially ecchymosis down the arm along the biceps, are usually present and the X-ray is of great assistance. The real difficulty is too great a tendency to treat the major abnormality, the dislocation, and to overlook very important, but less obvious, injuries. Sometimes failure to recognize complications is due to careless X-ray examination, but more often to the inexperience of the doctor who first treats the patient. Rupture or avulsion of tendons attached to the tuberosities should be suspected when the films are negative.
The injuries to nerves and arteries will be considered in Chapter XI.

REFERENCES OF AUTHORITIES TO THE ROLE OF THE SUPEASPINATUS
IN DISLOCATION

Little is to be found in the literature to confirm my beliefs or to explain why the short rotators come to be so frequently injured. Only a few writers have realized the frequency of such injuries, and I do not think that any" of them have appreciated the significance of the fact that the bursa and joint are thus put into communication.
Stimson says that the supraspinatus is sometimes, probably often, torn from its attachment to the humerus, and the same is true in less degree of the infraspinatus, and occasionally even of the teres minor. He states also that avulsion of the tuberosities may take the place of laceration of the tendons. Preston says that injury to the capsule is not infrequently accompanied by injury to the tendons which overlie and reinforce it, and when the violence producing the luxation is great, there may be a destruction of tendon continuity.
Stevens gives an excellent description of shoulder dislocation with especial reference to the short rotators. According to him, an anterior dislocation is an impossibility without putting a strain upon the tendons of the supraspinatus, infraspinatus and teres minor. With the humeral head in subcoracoid dislocation, the distance from origin to insertion of the supraspinatus is greatly increased, and in addition the tendon is angled over the rim of the empty glenoid. Similarly the posterior rotators are pulled over the posterior rim of the glenoid, and are almost always injured. "We may," he says, "assume that in every case of dislocation of the humerus, and especially in anterior dislocation, there is an injury to the tendon of the supraspinatus, and that often it is ruptured."
Very few other authors even allude to this tendon.
The following cases as well as the above quotations from the literature support the assertion that the facet of the supraspinatus may be torn off in dislocation.

CASE REPORTS

No. 12. Mr. A. F. K. Age 45. Massachusetts General Hospital No. 174082 W. S., Jan. 23, 1911.
A subcoracoid dislocation of four months' duration. Open reduction of dislocation. Supraspinatus was found retracted with facet of insertion. Heavy silk sutures to unite it with tuberosity. Feb. 24; 1912: An excellent functional result, but scar is ugly.

No. 22. Mr. J. H. D. Age 69. Massachusetts General Hospital No. 182238, April 22, 1912.
Five weeks ago fell, injuring right shoulder. Reduced by M.D. Went back to work. One week ago dislocated it again when drunk. I made an unsuccessful attempt at reduction in the Accident Room, and then carried the patient under ether to the operating room, and through the usual incision for the bursa I opened directly into the joint. A defect corresponding to the facet of the supraspinatus was found, the supraspinatus being retracted under the acromion. There was no piece of loose bone corresponding to the defect, although the whole joint was carefully searched. It must therefore be assumed that the loose piece had been absorbed. The dislocation was reduced, supraspinatus reinforced with silk and the wound closed. Two years later he wrote me: " I can do quite a lot with it, only when I reach overhead it gives way and causes some pain."

No. 71. Mrs. E. C. Age 68. On June 10, 1921, fell downstairs, broke left wrist and dislocated left shoulder. Ether was given by the local doctor, and he supposed he had reduced the dislocation. She consulted me on August 9, 1921, and after taking X-rays, I reported to the physician who had sent her to me that I thought that the shoulder joint had been reduced. The accompanying X-ray seemed to me to show that the bone was in place. I know now that this appearance is deceptive. In such cases as this, the tuberosity has been retracted into the glenoid and the head of the humerus rides on it. Therefore, there is not very much change of contour in the position of the shoulder, because the total amount of bony substance between the tip of the shoulder and the glenoid is the same, although the position of the tuberosity is reversed and lies in the glenoid. The following is an account of the operation which I did on April 5, 1922, nearly a year after the injury.
Sabre-cut incision. Prominent anterior mass proved to be head of humerus minus the tuberosity. The tuberosity had been retracted by the posterior short rotators and lay partly in the glenoid cavity and partly overlapping its posterior margin. The biceps tendon was displaced so as to lie between the head of the bone and the glenoid. It was excised. The retracted tuberosity was also excised. The synovial and tendinous capsule of the joint was completely gone, except at the anterior edge, namely, the portion formed by the subscapularis tendon. A good, practical result was obtained, i.e., a movable, painless, weak shoulder, lacking power in abduction, but more useful than a painful joint.

It is my belief that in most of these cases of dislocation where the X-ray shows a portion of the tuberosity to be absent, careful pictures will show its presence in the glenoid or just below the glenoid. The capsule forms a pouch below the glenoid and this pouch catches the smaller fragments if they have become loose. The cases are deceptive because a reasonable amount of motion may be found within the first few weeks and the position of the head is so nearly normal that it is not realized that the head does not actually touch the glenoid.

FIGURE 58. THE USUAL CAUSE OF FAILURE TO REDUCE A DISLOCATION
Mrs. E. C.— X-ray (a) before the local doctor attempted reduction. The fragments of tuberosities may be seen external to the lower edge of the glenoid. The head of the bone is displaced far beneath the coracoid process; the form of dislocation might be classified as subclavicular. It is probable that in this case there was both a true and a false dislocation. After reduction (b) the tuberosities seem to be absent, though indications of their fragments are shown near the lower edge of the glenoid. I have operated upon a number of other similar cases (e.g., Nos. 5 and 92), so that I have formed the opinion that when the X-ray after reduction shows the absence of the tuberosity, radical operation is indicated, even if the X-ray does not demonstrate the fragments. It is my belief that this form of displacement accounts for the great majority of instances, which the authors quoted in this chapter speak of, as unsatisfactory results.

Case 115, to be reported later, was also an illustration of this condition. Two of the most alert industrial surgeons whom I know were fooled by the superficial appearance in this case, and I, myself, did not recognize it on my first visit. Even Stevens, whom I regard as having been particularly well informed about conditions in the shoulder, shows in his illustration, "Fig. 4," what I believe to be a case of this kind. He speaks of the fragments as having disappeared behind the head of the humerus. In cases showing X-rays similar to this, I would recommend exploration through the routine incision of the bursa. If it is obvious that the fragment has retracted into the glenoid, I recommend enlarging the incision to a "sabre-cut," and making an attempt to suture the structures in their normal position.
Before leaving the subject of anterior dislocation, I should like to italicize the following paragraph:
I believe that after the reduction of every case of dislocation of the humerus, the patient should be allowed to recover from the anaesthetic and be urged to move his arm freely, before any bandaging is applied. All motions may be safely performed except abduction in external rotation, and even this may be done with due care and using extension at the same time. If we find paralysis of any of the muscles, areas of skin anaesthesia, undue axillary swelling, gritting sensation in the joint, or a tendency for the joint to slip out of place, the patient should be at once hospitalized and consultation obtained.

(The author here advises the reader to study the next chapter on fractures and then to return to the remainder of this chapter, which discusses some of the more unusual forms of dislocation.)

FIGURE 58
(c) Explanation. Erect dislocation, as usual, preceded the subcoracoid position. The fragments of tuberosity, still held together by the musculo-tendinous cuff, slipped down on the glenoid, while the head was dislocated below and the arm fell to the side. Reduction was attempted and seemed successful, but the head of the humerus merely became superimposed on the fragments so that it seemed that the dislocation had been reduced, and the contour of the swollen shoulder became nearly normal. The biceps tendon was carried with the fragments on to the glenoid. In Case 115 there was scarcely any fracture except at the facets of insertion; the whole musculo-tendinous cuff had dropped back on the glenoid. In most cases the retracted tuberosities are held on the glenoid by the short rotators, as this man holds his hat on the further side of the tree. The biceps tendon may (Case 115) or may not (Case 71) be torn in such cases.

Subacromial dislocation is rare. I can only recall one case in private practice. This was in a young man who was a personal friend. It is twenty years since I reduced his dislocation, immediately after the accident, and the shoulder has given him no trouble since. Probably most of these subacromial or subspinous cases run as smooth a course, but occasionally, as in the following instance, one proves to need operation.

No. 33. Mrs. C. B. Age 38. Massachusetts General Hospital No. 184814 W. S., Sept. 7, 1912.
A case of recurrent subspinous dislocation which had remained unreduced for three months. "Sabre-cut" incision, the joint carefully inspected and cleaned of old granulations and detritus. None of the short rotators had been ruptured. Dislocation reduced and acromion wired in place. April 17, 1914, she writes, "I am thankful to say my shoulder is all right. It does not seem to be as strong as the other one, otherwise it is fine."

This is the type of case in which the "sabre-cut" incision is particularly applicable, in fact, it is almost indispensable if one wishes to obtain a satisfactory cleaning out of the glenoid. In all these operations for old dislocations I have found the glenoid to be filled with old granulations and detritus. Satisfactory reduction could not have been done without thorough cleaning of the cartilaginous surface.
The second case is an illustration of what I believe to be the usual mechanism of subacromial dislocation. She gave the history that seven years previously the first dislocation had occurred, during a convulsion while she was in labor. Six months later she dislocated it again while " closing a door behind her." The last time it was dislocated by "turning quickly around in her chair."
In the case first mentioned, the young man sustained his injury while being thrown from a sitting posture on a toboggan which had struck a rock. He was thrown in the air—presumably still holding the railing of the toboggan. This might produce the same effect of internally rotating the arm, as in closing a door behind the back.

OLD DISLOCATIONS

Speed considers a dislocation as old and irreducible after three months. The obstacles to reduction are the same as for a simple dislocation plus such secondary changes as:

Cicatricial contraction from healing scars in the capsule and adhesions to surrounding structures.
Displaced bone fragments, osteophytic outgrowths, callus, etc.
Muscles shortened and atrophied.
Synovial space obliterated
One can readily understand the difficulty of reducing an old dislocation if he will study the specimens to be seen in anatomic museums. The remarkable attempts of nature to derive some utility from a dislocated shoulder joint make reduction most difficult. At the point where the humeral head lies against the scapula, a tremendous bony proliferation takes place, and inevitably ankylosis or pseudoarthrosis results. The glenoid becomes atrophied and filled with fibrous tissue.
The varying combinations of pain, deformity, and limitation of motion which these patients present have incited surgeons to attempt relief. Every surgeon of large experience htts probably made a few attempts to help such patients, but before long finds that they form a class of cases in which he can be generous to his younger colleagues, who also in time learn by experience. As a matter of fact, these are serious cases and demand expert care, although this is not attainable at present, for there are no such experts, so far as I am aware.
There are five general lines of treatment from which we may choose.

(1) To leave nature to do the best she can.
(2) To attempt bloodless reduction under an anaesthetic.
(3) To attempt open reduction.
(4) To resect the head of the humerus.
(5) To perform arthrodesis.

Andrews concluded that an attempt at reduction by manipulation is extremely dangerous. In his words, "The bloodless method has a gory trail of accidents." He finds fifty cases of hemorrhage, mostly fatal, up to 1905. An interesting one was reported by J. C. Warren, in whose case a large aneurysmal tumor arose after attempts at reduction. The subclavian was tied and recovery ensued.
If a new joint can be produced at all, it should be possible to do it by the "sabre-cut" incision, for all the structures of the joint are readily visible and accessible. I have encountered two chief difficulties. One has been the fusion of the retracted tendons and tuberosities with the glenoid alluded to in Case No. 71. If many months have passed, there is little left of the cartilaginous surface of the glenoid when the debris has been removed from it. However, this is not the chief obstacle—the real one being the absence of any synovial membrane to prevent adhesions of the cartilaginous head in its new bed. If the cartilaginous head is not too badly destroyed and seems likely to function, I should advise completing the attempt to make a new joint, but if the head has been eroded and there is no synovia left to surround it, adhesions will surely take place, and almost no motion will be secured. An irritable, painful joint with only a few degrees of mobility will result. In such a case, I think that one should deliberately perform excision or arthrodesis. The method of arthroplasty recently suggested by Dr. Laurence Jones of Kansas City offers a most hopeful solution of this problem.

RECURRENT OR HABITUAL DISLOCATION OF THE SHOULDER JOINT

Recurrent dislocation is not a common lesion, but it has interested a large number of investigators. Speed says that this lesion is peculiar to athletes and epileptics. This is more than a witticism, but not entirely true. Almost every author has put forward a somewhat different theory as to the cause of recurrent dislocation, and Speed has gathered together the most important ones. They are:

Defect in the head of the humerus acquired at first dislocation, or perhaps congenital.
Defect in the glenoid—acquired fracture of the edge, or congenital shallowness.
Rupture of the insertions of the external rotators of the head of the humerus.
Avulsion of tuberosities with or without rupture of the rotators.
Detachment of capsule from anterior lip of glenoid.
Enlarged joint from relaxed capsule following tears which have been given insufficient time for strong cicatrization, or repeated stretching without tears.
A seventh theory may be added. Since the shoulder joint is not a real joint, and is dependent for its integrity on a very complicated neuro-muscular cooperation, the essential feature in some of these interesting cases may be a failure of this cooperation. Reference to Plate I will show how easily incoordinated pulls from two opposing muscles might result in instability of the head on its fulcrum. Rupture or stretching of the tendon of the latissimus might thus make the joint unstable in the pivotal position. Certainly from an X-ray point of view the bony structures in most of these cases are normal.
The slight support furnished the joint by the bony structures has been considered, and it would seem more reasonable to suspect a defect in the major supporting structures, the muscles and their tendons, than in the bony structure. The importance of the supra-spinatus and of the other short rotators has been emphasized, and it has been noted with what frequency their continuity is broken in ordinary dislocations. More authors have found occasion to mention lesions of the short rotators and tuberosities in recurrent dislocations than in simple dislocations, because the majority of the former cases are treated surgically, so that more opportunity is afforded for observation.
Considerable evidence is given in favor of each of the causes listed by Speed and probably any one of them could well account for a recurrent dislocation. Hildebrand found two cases of fracture of the anterior rim of the glenoid with laceration of the capsule, in which he obtained good results by reshaping and deepening the glenoid. In an X-ray study of twenty-one cases in Hildebrand's clinic in Berlin, Pilz found definite bony defects in the humeral head in fifteen, de Fourmestraux found a deformity of the head in four out of eighty cases. Henderson reported no bone injury found by X-ray in many cases. We have seen several cases in which no abnormality could be found with careful X-ray examination.
According to Stevens recurrent dislocations at the shoulder joint are always due to more or less tearing of the supraspinatus, infraspinatus, teres minor, and more rarely of the subscapularis, and their subsequent repair by scar tissue in a position of stretch. No definite cases to prove this were given.
Thomas concludes that habitual dislocation is due to a traumatic, cicatricial, anterior, hernial pouch of the capsule. The most constant lesion which he found was a tear in the anterior and lower part of the capsule. In an experimental luxation of the shoulder on a cadaver, he placed the head in complete subcoracoid dislocation, and found the supraspinatus, infraspinatus and teres minor not torn or greatly stretched. However, any assumption that such lesions do not occur in the living is unwarranted, for the conditions are so different. In such experiments lax atonic tissues replace the living contractile muscles, and the force is gradually and gently applied as compared to the sudden smashing force acting in the living. A force suddenly applied against active muscles would have much greater rupturing power than a much greater force evenly applied against dead muscles.
One of the earliest mentions of the role of the supraspinatus was by Duchenne, who wrote: "Recurrent dislocation cannot occur with a normal supraspinatus." Yet I do not entirely agree with this great authority, for in none of my cases of habitual dislocation have I demonstrated such a rupture, and in two I actually did demonstrate that there was no rupture. Furthermore, I have never seen habitual dislocation complicate a case of ruptured supraspinatus.
Speed states that the head of the humerus twists out of the glenoid through the inferior portion of the capsule, and he believes that to permit this dislocation there must be a great strain on the supraspinatus tendon, or even a tear in it.
It is in the treatment of these recurrent cases that the greatest variations of opinion are to be found. Almost every author has contributed a different technique. The surprising thing is that so many varied methods should produce such uniformly excellent results as are claimed for them, yet the number of methods suggests that none is highly successful. The essential points of some of these methods of treatment will be briefly given with their results, when obtainable. Many of the reports are based upon too few cases followed for too brief a period. It is noticeable that few authors have reported later series in a second paper, and this suggests that the late results and greater experience have not supported them in their early statements.

Treatment.

Two general principles of treatment have been applied to habitual dislocation. They are:

Prevention—control primary dislocation, and allow healing of capsule.
Reconstruction.
A. Suspending head of humerus from above.
B. Support from below.
1. Reefing.
2. Bone operation on glenoid.
C. Combinations of above.
D. Use of the long head of the biceps as a round ligament.
A shearing-off of the attachment of the capsule to the fibrocartilage of the glenoid is described by Bankart as the cause of recurrent dislocation. The defect is permanent and his operation aims to repair the rent. His incision runs from above the clavicle downward and outward over the coracoid for about five inches. The deltoid and pectoralis major are separated, not cut, and the coracoid divided and driven downward with the muscles attached. The subscapularis tendon is divided and the capsule sutured to the glenoidal labium. The subscapularis and coracoid are sutured in place. Four weeks of rest is followed by active and passive motion. Four successful cases are reported.
Carrell, who gives the above classification of treatment, uses an ingenious combination of A. and B. An anterior incision exposes the long head of the biceps. The tendon is sectioned at its lowest level, and reflected from its sheath to where it emerges from the capsule. The distal end of the muscle is attached to the short head. To the free tendon is attached a piece of fascia about six inches long. A posterior incision running down four inches from the acromion separates the deltoid and exposes the teres minor. The fascia is passed under the neck, weaving in and out of the capsule. It emerges just above the teres minor and is passed through a drill hole in the acromion. The arm is immobilized at the side and motion begun in three weeks. Good results are reported in four cases. One wonders whether the posterior incision can be made without injury to the circumflex nerve. Recently Fowler has suggested a modification of this suspension operation. The biceps tendon is not interfered with, but a strip of fascia lata is passed through the capsule below the neck and anchored, both on the acromion and on the coracoid.
A bone transplant was placed by Eden under the raised periosteum of the neck of the scapula so that one-half to one centimeter stuck out in front of the joint. He also reefed the capsule and kept the arm abducted for three weeks.
Henderson's tenosuspension operation has been popular in America, but as seen by the discussion following Fowler's paper, it cannot be a thoroughly satisfactory procedure. Keller uses a crucial plication of the capsule through a posterior incision. Loeffler places a band of fascia from the greater tuberosity of the humerus to the acromion. Mandl used Finsterer's operation with success. The head of the humerus is held back by a band on the anterior surface of the joint, taking the place of the normal joint capsule. The band is composed of "part of the coraco-brachialis and part of the biceps." Oudard divides the subscapularis and overlaps it so as to shorten it about three centimeters. The tip of the coracoid is cut and a bone graft three to four centimeters long is inserted between base and tip. The coracoid may be slit and one-half slid down so as to lengthen the coracoid three centimeters. Nine cases were treated successfully. Six additional cases are reported. Perkins devised an operation in 1906 for suture of the torn capsule and reports good results. A restraining ligament was made by Plummer and Potts using a fascial strip from the greater tuberosity to the acromion. They report two cases with good results. Nine cases of recurring dislocation were treated in a year by Riviere, who pleated the capsule by placing interrupted sutures through the subscapu-laris. Landes uses a fascia lata cord or several silk sutures and suspends the head of the humerus by passing this cord through a drill hole and slinging it over the clavicle just lateral to the coracoid. Selig, who considers atrophy or rupture of the external rotators the main cause of habitual dislocation, makes an incision through the supraspinatus fossa, separates the trapezius fibers, and shortens the supraspinatus tendon by plication.
It is Sever's belief that the subscapularis and supraspinatus prevent dislocation when the arm is elevated by opposing the pectoralis major, which adducts and draws the humerus forward, and pulls the upper part of the humerus inward and downward. He says that in all operations for recurrence, the good comes from cutting the pectoralis major and shortening the subscapularis. No results are stated. He notes that repair of the infraspinatus and supraspinatus can also be done at the same time. Other authors, notably Allis, have also held similar views.
The operation advocated by Speed is done through an incision just below the coracoid and extending down four inches. The pectoralis major is divided one and one-half inches from its insertion into the humerus, and the axillary structures put aside. The edge of the glenoid is next palpated, after which, a drill hole one inch deep is made diagonally into the neck of the scapula. A bone transplant from the tibia is driven in with three-fourths inch projecting. This is supposed to prevent the head of the humerus from slipping out forward into anterior dislocation, at the same time not interfering with the normal range of motion.
A heavy silk ligature reenforces the anterior part of the capsule in the operation of Spitzy. A curved incision exposes the deltoid insertion, which is cut and retracted. A heavy silk ligature is passed around the surgical neck and tied in front. The ends are left long so that they can pass upward anterior to the capsule, and be tied over the coracoid. The capsule is then folded over the ligature and sewed, thus shortening the capsule. The deltoid is re-attached, and after a rest period of four weeks exercise is begun.
Thomas was an exponent of the capsule pleating operation. He used a posterior axillary incision, and took a reef in the capsule. He claimed exceedingly good results, as do the others. He performed capsulorrhaphy on eighteen epileptics suffering from recurrent dislocation. Twelve cases were successful, for a time at least. A capsule pleat and fascial transplant across the front of the joint is performed by Valtancoli, who reports eighty-six per cent cures.
It would seem that a patient stands some chance of cure by any of these methods. Therefore, it would be to the patient's advantage to choose the simplest, since his chances of recovery are as good as if he had the most complicated one. It is interesting to speculate why such a diversity of treatments should produce so uniform a result. It may be explained by the temporary or permanent limitation of joint function consequent to the operation. Some of the above procedures have as an object the limitation of motion, and all of them probably do limit motion. The trauma of the instrumentation, the bleeding and exudate, and the placing of sutures result in the formation of scar tissue. In addition the arm is immobilized for a time. Fixation and a sensitive scar produce pain on motion, and a certain mental impression which results in a patient's using his arm in a very gingerly way for a long time. Actual limitation or voluntary limitation are important reasons why the arm is not soon again moved into extreme elevation. It is highly probable that the late results of all these methods would not be entirely satisfactory.
Some authors have advocated and devised external apparatus to check abduction within a safe limit. These hobbles are a nuisance and offer no cure, but do prevent dislocation. The lesion is annoying and causes so much disability that many of these cases beg for operation. The treatment should be suited to the type of lesion and to the habits of the individual patient. Bony defects should be repaired or modified by plastic methods. Nicola's operation seems to be applicable, whatever the cause.
The writer has on two occasions done negative exploratory operations for this condition by opening the bursa but without entering the joint. The following case may be of interest to those who believe that deformities of the head of the bone may be the cause of recurrent dislocation, for in this patient a thorough exploration was done.

Case No. 24. Mr. K. N. Age 26. Massachusetts General Hospital No. 182833 E. S., May 22, 1912.

A large, powerful young man. First injury six months before while wrestling. Repeated dislocations after slight muscular efforts since then. "Sabre-cut" incision, supraspinatus divided and joint explored. The capsule was found to be torn, especially the portions at the lower and inner edge of the glenoid. A sort of hernia of the synovial membrane existed, which evidently made a pouch for the head when dislocated. A plastic repair was done on this part of the capsule. Part of the articular surface was missing, as if it had been broken off and absorbed. The patient was seen by me about a year after the operation, and at that time had a perfect result. I have not been able to trace him since.

This particular condition of axillary tearing of the capsule has been described by Thomas of Philadelphia, and considered by him to be the most common lesion in shoulder injuries. I have little doubt that it is a factor common to all recurrent dislocations. One cannot imagine dislocations occurring without a tear of the capsule of the joint. In all these cases the pillars of capsule which bound the opening of the bursa subscapularis must be more or less torn to enable the head of the humerus to lie in the subcoracoid position.
I have seen numerous cases of habitual dislocation, but owing to my lack of faith in any particular technique I have done few operations. I have been content to teach the patient about the mechanism of dislocation and explain to him that he cannot dislocate his arm without combining rotation and abduction. He may abduct the arm as much as he is able to do so in internal rotation in the coronal plane with impunity. These cases are usually in young men, and as has been said before, in athletes or in epileptics. Athletes may avoid dislocation by giving up those forms of athletics which tend to produce it. I have known two young men, who were my personal friends, both of whom were subject to this annoying difficulty. Both patients eventually outgrew it or changed their habits so that it did not occur. One of them, for instance, had to give up boxing because the arm would at times dislocate if he gave a forward blow. In doing this, the relation of scapula and humerus are practically the same as when they are in the pivotal position. He was a skillful athlete at other forms of amusement. It seems to me that for this type of patient it is better to change habits than to submit to operation.
In the cases of epileptics, it is imperative that the patient should wear an apparatus which prevents the combination of external rotation and abduction or should be operated upon. It has not been my fortune to have the care of any such cases. Should I be compelled to operate for this condition, I should at present choose the operation of Nicola. I here reprint some remarks made by Dr. Nicola at the discussion of Dr. Fowler's paper.
"For three years I have been using my own operation, which does not utilize any foreign material. It is done through one incision, the convalescence is short, and so far as I know there have been no recurrences on operations done by me as well as by about thirty other operators. It seems to me that it is getting more and more difficult for the student of orthopedics to decide which type of operation to use. In the end the operation that will become most popular is the one that is very simple to perform and can be done most frequently on almost any type of dislocation, no matter what the pathologic changes are (bony defects, muscle tears or capsular tears) ; and, finally, it is a matter of convalescence. In the operation which I have been doing, the line of incision begins just above the coracoid process and extends down and out in the line of the fibers of the deltoid. In my original description I stated that this should come between the pectoralis major and the deltoid, but I find that it is easy to approach it merely by going through the lines of the fibers of the deltoid. Before cutting the tendon, one should be sure to put transfixion sutures in both ends because frequently the arm may extend and the lower segment of the biceps tendon will slip behind the pectoralis and cause great anxiety. After the tendon is divided, a hole is drilled through the head of the humerus. I usually go anywhere along the bicipital groove and point the drill so that it comes out at the upper end of the angle of the head. The tendon is passed through the head and is sutured on itself, so that there is no muscle loss and the tendon has a tendency to restrict the movement and, therefore, keeps the head in the glenoid cavity. Some of the men have used this operation for fracture of the surgical neclc of the humerus when there has been downward displacement of the head into the axilla, and there they replace the head in position and drill a hole so that they maintain the head in position."
This operation appeals to me as more likely to fulfill the conditions required than any of the others. Fowler's operation also seems to me a rational procedure, but not so simple as Nicola's.
Extract from a personal letter from Dr. Nicola, June 6, 1930: "The cases reported in the reprint which you received, together with the rest, have been followed over a period of two years. The boxer has been back in the ring and has won two semifinal contests with no recurrence of dislocation. Case No. 3, which was an epileptic, was killed in an auto accident eight months after the operation. Through friendship with the coroner, I was able to examine the tendon of the long head of the biceps with special reference to the point which you made in your letter. I found that instead of thinning out of the long head of the biceps which extended to the glenoid cavity, the tendon above the humerus was thickened about the size of the little finger."
Extract from personal letter from Dr. Nicola, June 6, 1932: "I have personally done twenty-four of these operations with one hundred per cent cures. I have not heard of any recurrences from the various men who are associated with me at the Hospital for the Ruptured and Crippled. I hope that you will soon find an opportunity to operate upon such a case and to convince yourself that this operation is very simple to perform. I am now doing it through a two and one-half inch incision taken just below the clavicle on the inner side of the coracoid process and extending downward through the fibers of the deltoid muscle. The hole through the head of the humerus is made with a one-fourth inch gauge, instead of a drill. This facilitates matters considerably."
This operation I am sure could be readily done through my routine bursal incision which separates the deltoid fibers directly over the bicipital groove.

INFANTILE DISLOCATION OF THE SHOULDER

Lesions of the bursa or of the supraspinatus tendon in childhood apparently do not occur, at least they have never fallen within my experience. However, a not very infrequent lesion in childhood, namely, birth palsy complicated by dislocation of the shoulder, sometimes causes confusion in the diagnosis of shoulder lesions in later years. We see the shoulder deformed from a lesion which occurred at or soon after birth.
There has been much discussion as to whether the term congenital dislocation of the shoulder joint should ever be used. It seems very probable that a large number of so-called congenital subluxations, if not a majority of the published cases, were instances of obstetric palsy in which the dislocation remained after the paralysis had recovered. Infantile dislocation may be discussed under three headings, according to whether it existed before birth, occurred at birth or resulted soon after from paralysis caused at birth.

(1) Abnormality of development—true congenital dislocation. The existence of such a clinical entity has been questioned, but it has been established without any doubt, although it must be very rare. R. W. Smith of Dublin, in 1839, was the first to bring this condition before the profession. He published an account of three cases in the Dublin Journal of that year. Two of these were males, age 20. The dislocation was subcoracoid. The muscles about the shoulder were wasted. One patient had club foot. The third case was an insane woman, age 29, in whom the condition was bilateral.
At post-mortem examination there were facets just under the cora-coid, with a displacement of the capsule anteriorly to enclose the joint. The head of the humerus was flattened, and the acromion and coracoid elongated and hooked downward. In all the cases abduction was limited. Eleven years later Smith published two additional cases. In 1841 Guerin presented two cases and demonstrated a symmelian foetus which showed this abnormality on both sides. Since these reports, numerous cases have appeared in the literature. Grieg analyzed the cases of fifty-eight authors in the Edinburgh Medical Journal of 1923. He makes the following statement. "So far I have only found twelve cases reported to date in which evidence brought before the profession fails to justify any other conclusion than that they are cases of true primary congenital dislocation of the shoulder."

(2) Dislocation produced by obstetric manipulation or during birth. This group is open to criticism because proof of its existence is not satisfactory. T. T. Thomas was firmly of the opinion that traumatic dislocation not only occurs, but is the primary factor with regard to paralysis. He believed that paralysis is secondary to a rent in the capsule due to a traumatic dislocation. Taylor, writing in 1921, states that neither he nor any of three obstetricians of a large Lying-in Hospital had ever seen a case of Erb's palsy in which the subluxation preceded paralysis. In 1866 Loignan wrote a thesis for a Paris doctorate on the subject. He found that he could not dislocate the shoulder by manipulation. The constant lesion which occurred, if sufficient force were used, was a fracture of the humeral shaft through the soft bone under the epiphysis. Other investigators, notably Sever, have been unable to produce traumatic dislocation or rupture of the capsule by manipulation in infant cadavers. The writer feels that dislocation occurring at birth is so rare as to be negligible in diagnosis.

(3) Acquired subluxation due to injury of the plexus. Obstetric paralysis was first described by Smellie in 1768. He thought the condition was due to prolonged pressure on the arm while the child was in the pelvis. It was brought before the profession, however, by Duchenne, who in 1872 described four cases in infants and believed it to be due to pressure on the nerve trunks. Erb described the palsy in adults in 1874. Since that time it has been known as Erb-Duchenne paralysis. Erb believed it to be due to pressure on the fifth cervical root, known as Erb's point. Fieux opposed this view and adopted the theory that traction is responsible. He demonstrated on infant cadavers the fact that when the head is forcibly drawn away from the shoulder, the fifth cervical root is torn just proximal to its junction with the sixth nerve. With more force, the latter nerve may also be torn. Only the muscles of the upper arm are paralyzed. The palsy is usually flaccid.
Infants with Erb's palsy present a typical history and appearance. There is usually a difficult birth where traction on the head has been made under ether relaxation. The arm hangs limp and vertically at the side, the elbow is extended and the forearm pro-nated. There is inability to abduct, elevate, outwardly rotate, or supinate. There is extreme internal rotation so that the palm often faces outward. After a short time, there is wasting from disuse, and flattening of the shoulder soon appears. Passive motions' are free at first, but the healthy muscles soon contract and produce limitation of motion—notably of external rotation. The muscles paralyzed are the deltoid, supra- and infra-spinatus, teres minor, biceps, brachialis and brachioradialis. There is no sensory disturbance.
Clark, Taylor and Prout estimated one case of palsy in 2,000 births. Most cases of birth palsy show some luxation of the head of the humerus. Fairbanks saw twenty-eight subluxations in thirty-seven cases of palsy, or seventy-six per cent; Thomas reported nine in twelve. Taylor has reported sixty-eight cases, forty-six of which showed subluxation. He has never seen the condition in patients less than six weeks old. Of those patients who had palsy, who were more than six weeks old, seventy-seven per cent showed subluxation. In 109 X-ray studies reported by Sever in 1916, sixty-four or fifty-nine per cent showed subluxation. The ages in this series varied from one day to eighteen years.
It should be noted that this form of dislocation is posterior, while the first two forms are anterior or inferior.

Mechanism of Posterior Subluxation. The appearance of the arm soon undergoes a change from the flaccid condition which follows the immediate injury for a few weeks after birth. The upper arm is brought forward and adducted by contraction of the well muscles. The elbow is usually a little flexed, the pronated forearm passing downward and inward across the front of the body. Abduction is checked before the arm comes to a right angle. Backward motion is usually impossible and external rotation is markedly limited. With the elbow at the side, it is often impossible to rotate the humerus out sufficiently to bring the forearm into the forward plane. The bones of the affected side—the humerus, scapula and clavicle—are smaller than those on the opposite side. This is an important point in the diagnosis of late cases. The front of the shoulder is flattened, while there is a fullness behind, below the acromion, due to the head of the humerus. The muscles which tend to prevent posterior dislocation are the teres minor, supraspinatus, infraspinatus, and posterior part of the deltoid. The pectoralis major, the teres major and latissimus dorsi are rarely even partially paralyzed and rotate the humerus strongly inward. The subscapularis acts as a powerful internal rotator. These muscles become contracted while the paralyzed ones are stretched. The teres major and latissimus dorsi exert traction downward and posteriorly. The anterior portion of the capsule becomes shortened secondarily. Since the arm is held in an internally rotated position, there is a constant jstrain on the neck of the humerus, tending to twist it backward. In the plastic young bone, this twisting occurs and the plane of the head of the bone to the shaft may be changed ten or fifteen degrees. The dislocation is not truly posterior—it is rather a rotation of the head than a dislocation, so that the articular portion is rotated backward and the side of the head lies on the glenoid without having escaped from its capsule.
During the first year nothing can be seen in the way of bony deformity in the X-ray, except possibly a slight posterior subluxation and relatively small size of the head compared to that of the other side. As the child grows older, the subluxation increases. There is increased outward displacement and elevation of the scapula. The acromion and coracoid become hooked downward in front of the head of the humerus. The clavicle is shortened and its curves are more marked than in the normal. The coracoid process is usually elongated. The glenoid becomes shallow. These changes of the bones occur while the paralysis exists, and even if the paralysis clears up, they persist.

Treatment. In early cases the arm may be held in abduction, elevation, external rotation and supination by a light wire splint. Sever, however, prefers to let the child use the hand and arm freely with the risk of contractures. Passive motion and massage are carried out at frequent intervals. Operation is deferred until the child is three or four years of age. Once contractures have developed, it is best to cut the contracted muscles. Manipulation is of little value because of the tendency to recurrence, unless the paralyzed muscles have regained their tone. Sever has described his operation at length in a paper read before the Section on Orthopedic Surgery of the American Medical Association, 1925. He cuts the pectoralis and subscapularis tendons and removes one-half inch to three-quarters inch of the tip of the coracoid with its muscle attachments. If necessary he removes the hooked acromion to allow reduction. The arm is put up in a light splint in abduction, elevation, external rotation and supination. Muscle reeducation by active and passive motion is begun after eight to ten days. The splint is worn night and day for three months, but is removed daily for exercises.

Prognosis. This depends largely on the recovery of the paralyzed muscles in early cases. If the child is seen early, contractures and subluxation may be minimized by passive motion until the nerves have regenerated. In late cases, however, where contractures have developed and there is no tendency of the nerves to regenerate, operation has to be resorted to and gives a good, hut not brilliant, functional result. Sever records partial recovery in 297 of 394 cases which were operated upon. After operation there is great difficulty in inwardly rotating the arm. He states that this may be eventually overcome, however.
I have had very little personal experience in these cases, but the following case taught me such an important lesson that an account of it is presented in the hope that it may stimulate some one to follow up a series of such cases in which operations had been done in childhood.

CASE 70.
A strong boy, age 14, was referred to me for trouble with his shoulder, with the story that he had had difficulty since he was a baby, and that while he was a very strong, active boy otherwise, he was greatly handicapped by his shrunken, weak, deformed right arm. The diagnosis in the case puzzled me a good deal at first, for there was no paralysis, and the X-ray simply showed a rather small and deformed humeral head and glenoid cavity. In spite of this, by palpation, it was easy to feel that the head of the humerus was posterior to the glenoid under the acromion. Both the coracoid and the acromion were hooked down in an unnatural manner, which was easy to understand when one recognized the true character of the lesion, for the acromion process had nothing beneath it and was not performing its normal function. All parts of the shoulder, including the bones, were smaller than those of the opposite side. There was practically no motion in the scapulo-humeral joint and the arm was held in internal rotation. An extraordinary amount of compensatory mobility had developed in the motion of the scapula on the chest wall— not only in flexion and extension, but in abduction and adduction.
It was clearly a case of birth palsy in which the bones had remained out of place after the muscular paralyses had recovered, and therefore the patient now only suffered from the consequence of the luxation.
I operated on June 16, 1921, through a "sabre-cut" incision, and to my surprise, found that the cartilaginous surfaces of the glenoid and of the head of the humerus had remained in nearly a normal condition, although they had been separated for so many years. The capsule was stretched and distorted, but not disrupted. The cartilaginous surface of the glenoid was rather puckered and the articular head of the humerus was small and rather misshapen, although less so than one would think from the appearance in the X-ray, which of course showed the surface of the bony centers of the epiphysis and not the cartilage. The contraction of the subscapularis and pectoralis major was so great that I had to divide their tendons in order to get the head of the bone in place. The coracoid process was so deformed that I had to excise about two-thirds of it subperiosteal^ in order to reduce the humerus. The "sabre-cut" incision, of course, mobilized the acromion. After reducing the head of the bone, I was able to put four silk sutures "a-distance" to reunite the cut ends of the subscapularis. I did not attempt to correct the torsion of the neck, although it caused some eversion of the arm when the head of the bone was in place. The whole wound was sutured, and the patient was put up in plaster in semi-abduction and semi-external rotation.
It was most remarkable to watch the boy's convalescence. There was a good surgical recovery, but the miraculous part was to see the promptness with which the bones and muscles tended to grow into normal condition. Within six months he had nearly normal use of his shoulder, and the condition of the muscles had greatly improved.
As the patient lived in another city I lost track of him about six months after the operation and did not see him again for ten years, when I looked him up in preparation for this book. It is fortunate that I did so, for the lesson which I learned was important and may be of help to others.
During the ten years that had passed, the boy had become a man of twenty-four, whose occupation was in moving buildings. He did much of the manual labor himself. When he came into my office he looked strong and vigorous, and I had to ask him which shoulder was the bad one. Then my disappointment came.
A skillfully made movable pad inside his coat concealed the small size of his right shoulder. His vigorous handshake and well-developed forearm gave no hint of the practically ankylosed joint which was displayed when he removed his clothes. On closer examination I found both coracoid and acromion clutching down on the head of the bone like crooked fingers grasping it and holding it fixed. It appeared as if the acromion process had bent downward from the point where I had divided it and had become fixed in this position.
After a time the explanation occurred to me. At fourteen, the acromion and coracoid are cartilaginous epiphyses, for they have not yet ossified. After my operation, although the head of the humerus was in place, it was small and underdeveloped because of imperfect function for fourteen years. Consequently the cartilaginous acromion and coracoid became bent down over it, grasped it, and then, at about twenty, turned to bone and held it fixed. I did not at the time of the operation realize that the greater part of the acromion does not unite with the spinous process until about twenty. I think now that if I had insisted that this boy should have slept with his arm elevated until he was twenty, and had kept up appropriate exercises, he might have obtained a more perfect shoulder. It is not a great hardship to form the habit of sleeping with the arm in the hammock position. Many people do this by preference. He had been able to hold his arm in this position when I last saw him six months after the operation. Later the strength of the divided internal rotators returned and tended to rotate the arm to its old position, and also to resist elevation in external rotation. The head of the bone being small, the cartilaginous acromion slowly yielded to fit over its convexity. I think that it is highly probable that if the late results of other operations which have been done for these cases were critically examined, the same disappointing condition might be found in later years. Operations should not be undertaken on these cases unless the parents are warned that the patient should be under the surgeon's care until his epiphyses are united; i.e., when the patient is about twenty. I am inclined to think that nature's results at the end of ten years would compare very favorably with those of surgeons.

ACROMIO-CLAVICULAR DISLOCATION

A brief consideration of lesions of the acromio-clavicular joint seems advisable, although strictly speaking, neither the subacromial bursa nor the supraspinatus tendon are involved. One must remember that the coraco-acromial ligament intervenes between these structures. When this joint is dislocated the coraco-acromial ligament goes intact with the scapula. In severe cases the coraco-clavicular ligaments (conoid and trapezoid) are torn.
Mechanism. The acromio-clavicular joint, itself, is weak, but the conjunction of the two bones derives its strength from the conoid and trapezoid ligaments which are attached to the coracoid process of the scapula. Upward dislocation of the clavicle is favored by the upward and outward slope of the joint. The clavicular facet looks downward, outward, and backward. Dislocation is almost always caused by direct violence. A blow on the back of the acromion or a fall on the tip of the shoulder drives the acromion downward, inward, and forward, and the clavicle with the coracoid process as a fulcrum is torn away.
Dislocation is classed as complete or incomplete according to whether or not the facets clear each other. The ligaments of the joint itself are more or less torn, even in incomplete dislocation, but the conoid and trapezoid ligaments are usually torn in complete dislocation.
Diagnosis. The diagnosis is to be made from the history of trauma, pain and disability. The outer end of the clavicle is prominent and movable, and can be readily reduced, but reduction is hard to maintain if the coraco-clavicular ligaments are ruptured.
Treatment. Upward, outward, and backward traction on the scapula is indicated and can be applied by various braces or by recumbency. The most favored method is the clavicular cross. A T-shaped splint is applied to the back, and the shoulders strapped to the cross arms.
Open reduction and fixation are occasionally necessary. Several operations have been devised, most of them using fascial strips. Representative among these may be cited Bunnell's ingenious method. He threads a cord of fascia through holes in the acromion and clavicle, and places a loop under the coracoid process.
Prognosis. If the reduction can be maintained, the chances are good that a patient will regain function in the course of several months, but soreness and some pain may persist for years. Arthritic changes may take place. I personally have never found it necessary to operate on acromio-clavicular dislocation, but in extreme cases I should recommend Bunnell's operation.

ACROMIO-CLAVICULAR ARTHRITIS

In contrast to the mechanism of the scapulo-humeral articulation, that of the acromio-clavicular joint is typical of the kind in which arthritis is prone to occur. It is a hinge joint with a very limited degree of motion. For its size, when in action, it carries an immense burden of weight. For instance, as one pushes open a heavy door, this little joint has to bear the equivalent weight of almost the^ whole power exerted. The same is true of the joint on the sternal end of the clavicle, but that joint has a much larger surface area. In laboring men who carry or lift heavy burdens, spurring from arthritis of the acromio-clavicular joint is so common as to form almost as normal a tissue as the great calluses in their hands. In many of the older individuals, the rims of new-formed bone actually fuse, so that the joint becomes obliterated. These changes may progress with very little pain and discomfort to the individual, or they may be accompanied by the usual signs of arthritis, which occasionally are so severe that they incapacitate the patient.
The acromio-clavicular joint holds an exposed position on the shoulder, and falling objects not infrequently strike the joint directly—perhaps breaking some of the small bony lips, causing hemorrhage about or in the joint. Such cases may be laid up for months on account of the local tenderness when they attempt to use the arm. I find it very difficult, in giving an opinion on compensation cases, to state when such individuals should be expected to return to work. The X-ray appearance is far from being a criterion. A man may have a very ragged and hypertrophied-looking joint and yet be conscious of no symptoms. Another man with barely perceptible changes may have much local tenderness. On the whole, it is surprising how well these laboring men are able to bear acromioclavicular arthritis. The diagnosis of these lesions rests entirely on the readily ascertained facts of localized swelling and tenderness, supported by the X-ray evidence of lipping of the joint. Confusion in diagnosis only arises when one allows one's self to center his attention on this joint and to ignore other really more important lesions. Never forget that this condition may attract your attention too readily, and by its presence conceal a lesion of the supraspinatus which is far more serious. Acromio-clavicular arthritis must be judged by the degree of symptoms, not by its X-ray appearance, for often there is much lipping of the edges of these joints and yet no symptoms at all.
Treatment. As a rule, these cases respond well to rest. A few weeks' confinement of the arm in a sling soon after a bruise on one of these joints is all that should be attempted. I am convinced that complete fixation of this joint is unfortunate. I do think that rest is very important in acute stages. Patients who have had prolonged symptoms have usually had either prolonged energetic treatment or prolonged fixation.
In a few subacute and prolonged cases, I have cut into the joint with the same idea that one has in cases of periostitis, where one incises to cause relief of tension. As a rule, however, I believe that simple rest is the only form of treatment which is important. The usual physiotherapy methods may be of some use, but my personal experience with them has been little.
Remember that the acromio-clavicular joint is not in immediate anatomic relation with the subacromial bursa. The coraco-acromial ligament intervenes. Therefore, acromio-clavicular arthritis does not prevent rotation or abduction in the scapulo-humeral joint, except in extreme positions. If these motions are not present, do not blame the acromio-clavicular joint entirely, even if it is swollen and tender.
Arthritic changes in this joint commonly occur after luxation or subluxation, and soreness may continue many months and sometimes a few years after such accidents. Men who do their own work generally continue at it in spite of this protracted soreness, but employees are apt to find their shoulders too sore to permit labor, if their compensation is paid. Thus this little lesion may be the cause of their never working again, for it is a commonplace that a year of loafing is a serious matter for an elderly laborer. Surgical obliteration of the joint should be considered, in some cases at least, as a mental stimulant. It is not an important joint.

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RIVIERE, G. Capsulorrhapie de l'articulation de l'£paule pour luxation recidivante. Lvon Chir. 1918. 15. 437-439. Abst. J. A. M. A. 1919. 72. 612.
SCHI.AEPFER, K. Uncomplicated dislocations of the shoulder; their rational treatment and late results. Amer. J. Med. Sc. 1924. 167. 244-255.
SELIO, R. Die bei der habituellen Schulterluxation gebrauchlichen Operations methoden von anatomischen Grundsatzen aus betrachtet. Was leistet der Musculus supraspinatus. Deut. Zeit. fur Chir. 1915. 132. 581-588.
SEVER, J. W. The rational treatment of fractures of the upper end of the humerus. Report of end results. J. A. M. A. 1923. 80. 1603-1608.
SEVER, J. W. Recurrent dislocation of the shoulder joint. Mechanical consideration of its treatment. J. A. M. A. 1921. 925-927.
SINZ, P. Inaugural-Dissertation. Erlangen. 1982.
SPEED, K. Recurrent anterior dislocation at the shoulder. Operative cure by bone graft. Surg. Gyn. and Obst. 1927. 44. 468-477.
SPEED, K. Fractures and dislocations.
Lea and Febiger, Phila. 1916. p. 857-440.
SPITZY, H. Stabilization of the shoulder joint for habitual dislocation.
Surg. Gyn. and Obst. 1928. 46. 256-257. STEVENS, J. H. The action of the short rotators on the normal abduction of the
arm, with a consideration of their action in some cases of subacromial bursitis
and allied conditions.
Amer. J. Med. Sc. 1909. 138. 870-884. STEVENS, J. H. Dislocation of the shoulder.
Ann. Surg. 1926. 83. 84-103. STEVENS, J. H. Fractures of the upper end of the humerus.
Ann. Surg. 1919. 69. 147-160. STIMSON, L. A. Fractures and dislocations.
Lea and Febiger, Phila. 1917. TAYLOR, R. T. Fracture dislocation of the shoulder. Arch. Surg. 1928. 17. 475-483. THOMAS, T. T. Habitual or recurrent dislocation of the shoulder. Etiology and
pathology.
Amer. J. Med. Sc. 1909. 137. 229-246.
J. A. M. A. 85. No. 16, s. 1202. 1925. TREVES, F. Surgical applied anatomy.
Lea and Febiger, Phila. 5th ed. VALTANCOLI, G. Sulla lussazione abituale di spalla.
Chir. d. Organi di Movimento. 1924. 9. 131-140. WARREN, J. C. Am. J. Med. Sci. 1846. XI. WILSON, P. D. & COCHRANE, W. A. Fractures and dislocations.
Lippincott & Co. 1925. p. 59-153.

NOTE—Sinz (1932) gives a very extensive Bibliography. He recommends a bone transplant to the glenoid (after Perthes or Eden) but apparently was unaware of the work of Nicola.

==References==
<references />

File:Figure 19B.png

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Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. Finally, the anterior capsule (white arrow) is reconstructed by the imbrication of the coracoacromial ligament (CA) with a resorbable suture. It is crucial that during the reconstruction, the arm is placed in adduction, anterior forward flexion, and external rotation and that the anteriorly dislocated humeral head is reduced.

File:Figure 19A.png

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Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. Finally, the anterior capsule (white arrow) is reconstructed by the imbrication of the coracoacromial ligament (CA) with a resorbable suture. It is crucial that during the reconstruction, the arm is placed in adduction, anterior forward flexion, and external rotation. In this figure we see that the humeral head is stil anteriorly dislocated.

File:Figure 18B.png

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Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. Reattachment of the labrum (white arrow) on the coracoid process (CP) remains to be done. G – glenoid.

File:Figure 18A.png

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Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. Reattachment of the labrum (white arrow) on the coracoid process (CP) remains to be done a). The labral reattachment (white arrow) has been performed

File:Figure 17.png

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Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. A Darrach (D) is used to place the superior part of the coracoid process flush with the glenoid face. The superior hole is drilled with a 2.75 mm cannulated drill in the AGN, the length is measured, and the screw is introduced but not fully tightened. CP – coracoid process, white arrow – coracoacromial ligament.

File:Figure 16.png

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Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The coracoid process (CP) is placed at the prepared AGN surface. First, the inferior screw is introduced for preliminary fixation of the coracoid process so that the graft can still slightly rotate around the screw. CT – conjoined tendon.

Anteroinferior Glenohumeral Instability

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Marko.nabergoj: Text

==Bullet points==

*One of most common shoulder injuries, 1.7% annual rate in general population.

*High recurrence rate that correlates with age at dislocation, up to 80-90% in teenagers (90% chance for recurrence in age <20).

*The stability of the glenohumeral joint depends on soft tissue stabilizers, bone morphology and dynamic stabilizers such as the rotator cuff and long head of the biceps tendon.

*Osseous lesions, either humeral or glenoid, are identified in 95.0%. The risk of failure of arthroscopic treatment is higher if not addressed. A glenoid bony defect of >20-25% is considered "critical" and is biomechanically highly unstable and require bony procedure to restore bone loss (Latarjet, Bristow, other sources of autograft or allograft).

*A Malgaigne (Hill Sachs) defect is a chondral impaction injury in the posterosuperior humeral head secondary to contact with the glenoid rim. It is present in 80% of traumatic dislocations and 25% of traumatic subluxations.

*Axillary nerve injury is most often a transient neurapraxia of the axillary nerve and is present in up to 5% of patients.

*Incidence of associated rotator cuff tears increase with age of 40 (30% at 40, 80% at 60).

*Static glenohumeral stabilizers are the bone, the ligaments, the capsule, the labrum, and the negative pressure. The dynamic ones are the rotator cuff and long head of biceps tendon.

*The labrum contributes to 50% of additional glenoid depth.

*Anterior static shoulder stability with arm in 90 degrees of abduction and external rotation is provided by the anterior band of inferior glenohumeral ligament (main restraint).

*The middle glenohumeral ligament provides static restraint with arm in 45 degrees of abduction and external rotation.

*The superior glenohumeral ligament provides static restraint with arm at the side.

*The physical examination demonstrates instability if the apprehension test is positive, multidirectional hyperlaxity when the external rotation at side is equal or above 85 degrees, and a pathological laxity of the inferior glenohumeral ligament if the hyperabduction test is positive.

*Three views plain radiographs, including true anteroposterior of the glenohumeral joint, scapular Y (scapular lateral), and Velpeau axillary views are the mainstay of imaging in the setting of acute traumatic anterior instability. Plain radiographs including anteroposterior in neutral, internal and external rotations, scapular Y and Bernageau views are obtained for recurrent instability. Magnetic resonance imaging (MRI) arthrogram is useful to assess for labral or rotator cuff tears, computed tomography (CT) for bone loss assessment.

*Conservative treatment after the first traumatic anterior dislocation is recommended for patients who are not actively engaged in sports, above the age of 30 years old, with a low functional demand, with an associated humeral fracture, or for the athlete with an in-season shoulder dislocation.

*Rehabilitation consist of strengthening of dynamic stabilizers (rotator cuff and periscapular musculature), exercises for proprioception and other specific treatments if apprehension persists.

*Surgical treatment included Bankart repair, capsular plication +/- soft tissue procedures (such as remplissage or dynamic anterior stabilization (DAS) if < 20% bone loss.

*If bone loss ≥ 20%, bone reconstruction with Latarjet, Bristow or free bone block transfers such as Eden-Hybinette is recommended.

==Key words==
Anterior glenohumeral instability; anatomy; humerus; scapula; ligaments; shoulder dislocation; subluxation; reduction; bone loss; Malgaigne; Hill-Sachs; Bankart; capsular shift; remplissage; dynamic anterior stabilization (DAS); Latarjet; Bristow; free bone block transfer; Eden-Hybinette; complication; recurrences; therapeutic implications.

==History==
The first recorded depictions of shoulder reduction are ancient.<ref>Iqbal S, Jacobs U, Akhtar A, Macfarlane RJ, Waseem M. A history of shoulder surgery. Open Orthop J 2013;7:305-9.</ref>

Egyptian hieroglyphs dated 3000 years earlier, pictorially depict a leverage method of shoulder manipulation. They have been followed by the Greeks and Romans. Around 400 BC, Hippocrates, the father of Western medicine, introduced the traction method to reduce the shoulder.
<ref>Hussein MK. Kocher's method is 3,000 years old. J Bone Joint Surg Br 1968;50:669-71.</ref><ref>Celsus A. De Medicina.</ref><ref>Hippocrates. Corpus Hippocraticum—De articulis.</ref>

In 1855, Malgaigne was the first one to describe the humeral bone loss also called Hill-Sachs lesion.<ref>Malgaigne J. Traité des fractures et des luxations. Paris: J.-B. Baillière; 1855.</ref>

In the 1890s, the understanding of the unstable shoulder was elucidated by the work of two French researchers, Broca and Hartman who introduced the concept of capsulolabral damage following dislocations as possible cause of recurrent instability. Notably, most of the findings considered current hallmarks of shoulder instability, including Bankart lesion, bony Bankart, Kim lesion, as well as anterior and posterior labral periosteal sleeve avulsions and glenoid avulsions of glenohumeral ligaments, were described in their papers decades before the eponymous figures to whom they are now commonly assigned depicted them.<ref>Broca A, Hartmann H. Contribution à l'étude des luxations de l'épaule (luxations anciennes et luxations récidivantes). Bull Soc Anat 1890;4:416-23.</ref>

In 1906, Perthes in Germany and a few years later, Bankart in the UK ascertained that the detachment of the labrum caused instability of the shoulder and emphasized reattachment of the labrum to stabilize the joint.<ref>Perthes G. Ueber Operationen beihabitueller Schulterluxation. Dtsch Z Chir 1906;85:199–227.</ref><ref>Bankart AS. Recurrent or Habitual Dislocation of the Shoulder-Joint. British medical journal 1923;2:1132-3.</ref>

Current free bone grafting techniques are based on the initial descriptions by Eden in 1918 and Hybinette in 1932 using autologous iliac crest.<ref>Eden R. Zur Operation der habituellen Schulterluxation unter Mitteilung eines neuen Verfahrens bei Abriss am inneren Pfannenrande. Dsch Z Chir 1918;144:269.</ref><ref>Hybinette S. De la transplantation d’un fragment osseux pour remédier aux luxations récidivantes de l’épaule. Acta Chir Scand 1932:411-45.</ref>

Due to donor site morbidity with autologous iliac crest bone grafting techniques, different auto- and allogeneic bone materials have been evaluated as alternatives. Open and arthroscopic approaches using distal clavicle, femoral head, distal tibial allografts or coracoid process are currently used. The first coracoid process transplant was probably realized by the German surgeon Noeske in 1921.<ref>Anonymous. Zentralbl Chir 1924;43:2402.</ref>

Nowadays, two most popular bony procedures included the Latarjet and its variant, the Bristow.<ref name=":1">Latarjet M. Treatment of recurrent dislocation of the shoulder. Lyon Chir 1954;49:994-7.</ref><ref name=":2">Helfet AJ. Coracoid transplantation for recurring dislocation of the shoulder. J Bone Joint Surg Br 1958;40-B:198-202.</ref>

==Anecdote==
(unpublished data, courtesy of Gilles Walch) At the beginning of the 1950s, Albert Trillat, the head of the orthopedic surgical clinic at the Edouard Herriot Hospital in Lyon (France) and also the promoter of the "no-touch technique", reported combination of an anterior labro-ligamentous complex reinsertion when feasible with a reduction of a so-called coraco-glenoid outlet by means of a coracoid osteoclasy and nail fixation (Figures).<ref>Trillat A. Traitement de la luxation récidivante de l'épaule. Considérations techniques. Lyon Chir 1954:986-93.</ref>
[[File:1562526202257-lg.jpg|thumb|500x500px|Postoperative anteroposterior X-ray of a right Trillat.|alt=|left]]
[[File:1562526204072-lg.jpg|alt=|none|thumb|500x500px|The illustrations demonstrate the effect of the procedure that reduce the coraco-glenoid outlet and lower the subscapularis. Courtesy of Gilles Walch.]]
Another surgeon, Michel Latarjet, who was mainly active in the field of thoracic surgery, visited Dr. Trillat to learn the aforementioned technique. When Latarjet supposedly tried to reproduce the Trillat procedure, he carried an involuntary complete coracoid osteotomy. Thenceforth, not knowing what to do with the bony fragment, he fixed it to the anterior glenoid through the subscapularis using a screw. From this mishap was born the operation which now bears his name.<ref name=":1" />

==Anatomical Considerations==
The glenohumeral joint has six degrees of freedom with minimal bony constraint that provides a large functional range of motion. It thus renders this diarthrodial joint particularly vulnerable to instability. The glenohumeral joint is stabilized by dynamic and static structures. The dynamic stabilizers include the rotator cuff, the long head of the biceps, and the deltoid. The static stabilizers of the joint include the capsule, the glenohumeral ligaments, the labrum, the negative pressure within the joint capsule, and the bony congruity of the joint. The superior glenohumeral ligament functions primarily to resist inferior translation and external rotation of the humeral head in the adducted arm. The middle glenohumeral ligament functions primarily to resist external rotation from 0 degree to 90 degrees and provides anterior stability to the moderately abducted shoulder. The inferior glenohumeral ligament is composed of two bands; anterior and posterior, and the intervening capsule. The primary function of the anterior band of the inferior glenohumeral ligament is to resist anteroinferior translation.<ref name=":3">Burkart AC, Debski RE. Anatomy and function of the glenohumeral ligaments in anterior shoulder instability. Clin Orthop Relat Res 2002:32-9.</ref>

==Prevalence==
The glenohumeral joint is the most commonly dislocated large joint of the body, affecting approximately 1.7% of the general population.<ref>Romeo AA, Cohen BS, Carreira DS. Traumatic anterior shoulder instability. Orthop Clin North Am 2001;32:399-409.</ref>

In greater than 90% of cases, the instability is anterior, has a traumatic origin, and occurs in young athletes involved in contact sports.<ref>Goss TP. Anterior glenohumeral instability. Orthopedics 1988;11:87-95.</ref><ref>Owens BD, Agel J, Mountcastle SB, Cameron KL, Nelson BJ. Incidence of glenohumeral instability in collegiate athletics. Am J Sports Med 2009;37:1750-4.</ref>

Ongoing sports participation in this population is associated with a high recurrence rate.<ref>Owens BD, Dickens JF, Kilcoyne KG, Rue JP. Management of mid-season traumatic anterior shoulder instability in athletes. J Am Acad Orthop Surg 2012;20:518-26.</ref>

==Pathoanatomy and biomechanics==
Anterior shoulder instability usually occurs with an anteriorly directed force applied to an abducted and externally rotated arm, or from a direct blow. During an anterior dislocation, many of the passive and active stabilizers may be damaged. The glenoid labrum, the glenohumeral ligaments, and the glenohumeral joint capsule, representing the soft tissue passive stabilizers will be injured; an avulsion of the anterior labrum, the classic Bankart lesion (Figure) or its variations (glenolabral articular disruption (GLAD), Perthes, anterior labroligamentous periosteal sleeve avulsion (ALPSA)) is almost invariably present,11,22,23 although it does not produce instability in isolation.<ref>Bankart AS. Recurrent or Habitual Dislocation of the Shoulder-Joint. British medical journal 1923;2:1132-3.</ref><ref>Neviaser TJ. The anterior labroligamentous periosteal sleeve avulsion lesion: a cause of anterior instability of the shoulder. Arthroscopy 1993;9:17-21.</ref><ref>Neviaser TJ. The GLAD lesion: another cause of anterior shoulder pain. Arthroscopy 1993;9:22-3.</ref><ref>Speer KP, Deng X, Borrero S, Torzilli PA, Altchek DA, Warren RF. Biomechanical evaluation of a simulated Bankart lesion. J Bone Joint Surg Am 1994;76:1819-26.</ref>
[[File:1562526629855-lg.jpg|thumb|600x600px|A) Coronal T2 MRI views of a right shoulder. The white arrow points a Bankart lesion. B) Arthroscopic view of the same lesion from a posterior portal.|alt=]]
The anteroinferior glenohumeral ligaments and the capsule can be detached from the glenoid rim, and a plastic deformation of the glenohumeral ligaments or an HAGL lesion (Figure) are other common features.<ref>Wolf EM, Cheng JC, Dickson K. Humeral avulsion of glenohumeral ligaments as a cause of anterior shoulder instability. Arthroscopy 1995;11:600-7.</ref>
[[File:1562526631138-lg.jpg|thumb|761x761px|Coronal T2 MRI views of a right shoulder. The white arrow points a HAGL lesion. A retensioning of the inferior glenohumeral ligament (capsular shift according to Neer) will be inefficient.|alt=]]
The plastic deformation of these structures becomes progressively more severe with subsequent episodes.<ref>Bigliani LU, Pollock RG, Soslowsky LJ, Flatow EL, Pawluk RJ, Mow VC. Tensile properties of the inferior glenohumeral ligament. J Orthop Res 1992;10:187-97.</ref><ref>Habermeyer P, Gleyze P, Rickert M. Evolution of lesions of the labrum-ligament complex in posttraumatic anterior shoulder instability: a prospective study. J Shoulder Elbow Surg 1999;8:66-74.</ref><ref>Urayama M, Itoi E, Sashi R, Minagawa H, Sato K. Capsular elongation in shoulders with recurrent anterior dislocation. Quantitative assessment with magnetic resonance arthrography. Am J Sports Med 2003;31:64-7.</ref>

The middle glenohumeral ligament functions to limit both anterior and posterior translations of the arm at 45 degrees of abduction and 45 degrees of external rotation whereas the inferior glenohumeral ligament resists translation of the arm in greater degrees of abduction.<ref name=":3" />

In addition to progressive soft tissue injury, recurrent dislocations can facilitate bony injury. Bony lesions are frequent in recurrent cases and may include defects of the glenoid (bony Bankart or beveling of the anterior glenoid resulting in loss of glenoid concavity), impaction of the posterolateral humeral head (Malgaigne lesion), or even coracoid or proximal humerus fractures (Figure).<ref>Griffith JF, Antonio GE, Yung PS, Wong EM, Yu AB, Ahuja AT, Chan KM. Prevalence, pattern, and spectrum of glenoid bone loss in anterior shoulder dislocation: CT analysis of 218 patients. AJR American journal of roentgenology 2008;190:1247-54.</ref><ref>Buscayret F, Edwards TB, Szabo I, Adeleine P, Coudane H, Walch G. Glenohumeral arthrosis in anterior instability before and after surgical treatment: incidence and contributing factors. Am J Sports Med 2004;32:1165-72.</ref><ref>Edwards TB, Boulahia A, Walch G. Radiographic analysis of bone defects in chronic anterior shoulder instability. Arthroscopy 2003;19:732-9.</ref>
[[File:1562527520975-lg.jpg|thumb|600x600px|A) Sagittal view of a CT arthrogram of a left shoulder demonstrates a significant Bankart fracture (white arrow) that produces an “inverted-pear” glenoid. B) Plain anteroposterior radiograph reveals an anteroinferior glenohumeral dislocation with an “engaged” Malgaigne (Hill-Sachs) lesion of the humerus.|alt=]]
Given that the average glenoid diameter is about 24 mm, a 6 mm-wide or larger fragment of the glenoid will typically equate to a 25% or more of the articular surface and is considered a large bony fragment.<ref name=":4">Burkhart SS, De Beer JF. Traumatic glenohumeral bone defects and their relationship to failure of arthroscopic Bankart repairs: significance of the inverted-pear glenoid and the humeral engaging Hill-Sachs lesion. Arthroscopy 2000;16:677-94.</ref><ref>Burkhart SS, Debeer JF, Tehrany AM, Parten PM. Quantifying glenoid bone loss arthroscopically in shoulder instability. Arthroscopy 2002;18:488-91.</ref>

Such significant glenoid bone loss can be viewed arthroscopically as an inverted pear configuration. All Malgaigne lesions are by definition engaging lesions (since it has engaged at least once). Thus, the notion of “engaging” versus “non-engaging” can lead to significant confusion. Some have proposed that the important lesions are those that engage in the 90-90 position.

Finally, the active restraint, mainly a lesion of the rotator cuff above the age of 40, will complete this complex situation.<ref name=":5">Antonio GE, Griffith JF, Yu AB, Yung PS, Chan KM, Ahuja AT. First-time shoulder dislocation: High prevalence of labral injury and age-related differences revealed by MR arthrography. JMRI 2007;26:983-91.</ref><ref>Itoi E, Tabata S. Rotator cuff tears in anterior dislocation of the shoulder. Int orthop 1992;16:240-4.</ref>

The glenohumeral joint is stabilized by a so-called “concavity compression” principle with the rotator cuff pulling the humeral head into the glenoid concavity and therefore ensuring stability through counteracting decentering translational forces.<ref>Lazarus MD, Sidles JA, Harryman DT, 2nd, Matsen FA, 3rd. Effect of a chondral-labral defect on glenoid concavity and glenohumeral stability. A cadaveric model. J Bone Joint Surg Am 1996;78:94-102.</ref><ref>Matsen FA, 3rd, Harryman DT, 2nd, Sidles JA. Mechanics of glenohumeral instability. Clinics in sports medicine 1991;10:783-8.</ref><ref>Yamamoto A, Takagishi K, Osawa T, Yanagawa T, Nakajima D, Shitara H, Kobayashi T. Prevalence and risk factors of a rotator cuff tear in the general population. J Shoulder Elbow Surg 2010;19:116-20.</ref>

==Natural History and Risk Factors of Dislocation or Recurrences==
To understand the natural history of instability and its importance for the appropriate management of this pathology, the following questions should be answered: What happens in the shoulder after the first dislocation? Which structures suffer damage? Who are the patients at higher risk of recurrence? How does the disease evolve without treatment? Will surgical treatment avoid future negative outcomes and prevent degenerative joint disease? Who should we treat and when?<ref>Carpinteiro EP, Barros AA. Natural History of Anterior Shoulder Instability. Open Orthop J. 2017 Aug 31;11:909-918.</ref>

80% of anterior-inferior dislocations occur in young patients. Recurrent instability is common and multiple dislocations are the rule. Instability is influenced by a large number of variables, including age of onset, activity profile, number of episodes,delay between first episode and surgical treatment. The different risks factors are:

-Young males (up to 100% of recurrence),<ref name=":6">Postacchini F, Gumina S, Cinotti G. Anterior shoulder dislocation in adolescents. J Shoulder Elbow Surg 2000;9:470-4.</ref><ref name=":7">Hovelius L, Augustini BG, Fredin H, Johansson O, Norlin R, Thorling J. Primary anterior dislocation of the shoulder in young patients. A ten-year prospective study. J Bone Joint Surg Am 1996;78:1677-84.</ref>

-Practice of contact sports, forced overhead activity,

-Sport practice at a competitive level,<ref name=":8">Balg F, Boileau P. The instability severity index score. A simple pre-operative score to select patients for arthroscopic or open shoulder stabilisation. J Bone Joint Surg Br 2007;89:1470-7.</ref>

-Bony impairment,

-Concomitant hyperlaxity.<ref>Habermeyer P, Jung D, Ebert T. [Treatment strategy in first traumatic anterior dislocation of the shoulder. Plea for a multi-stage concept of preventive initial management]. Der Unfallchirurg 1998;101:328-41.</ref>

==Classification==
Instability can be classified as primary or recurrent. The latter can be further classified as dislocation, subluxation, apprehension, or an unstable painful shoulder. In frank dislocation, the articular surfaced of the joint are completely separated. Subluxation is defined as symptomatic translation of the humeral head on the glenoid without complete separation of the articular surfaces. Apprehension is classically defined by fear of imminent dislocation in the 90-90 position. This could correspond to an instability phenomena or a persistent fear after a successful glenohumeral stabilization (please refer to Apprehension chapter).<ref name=":9">Haller S, Cunningham G, Laedermann A, Hofmeister J, Van De Ville D, Lovblad KO, Hoffmeyer P. Shoulder apprehension impacts large-scale functional brain networks. AJNR American journal of neuroradiology 2014;35:691-7.</ref>

The unstable painful shoulder presents as pain only (as opposed to a sense of instability) during an apprehension maneuver at clinical examination.<ref name=":10">Boileau P, Zumstein M, Balg F, Penington S, Bicknell RT. The unstable painful shoulder (UPS) as a cause of pain from unrecognized anteroinferior instability in the young athlete. J Shoulder Elbow Surg 2011;20:98-106.</ref><ref name=":11">Patte D, Bernageau J, Rodineau J, Gardes JC. [Unstable painful shoulders (author's transl)]. Rev Chir Orthop Reparatrice Appar Mot 1980;66:157-65.</ref>

The majority of these patients has a history of trauma, but simply do not report a clear history of trauma. Careful preoperative and/or arthroscopic examination will show that the majority of these patients also has evidence of instability (i.e. labral tear, glenoid fracture, or Malgaigne (Hill-Sachs) lesion)

Five types of traumatic anterior dislocation have been described. The subcoracoid dislocation has an antero-inferior direction and is the most common. Other types, including subglenoid, subclavicular, retroperitoneal, and intrathoracic are rare and usually associated with severe trauma.<ref>Patel MR, Pardee ML, Singerman RC. Intrathoracic Dislocation of the Head of the Humerus. J Bone Joint Surg Am 1963;45:1712-4.</ref><ref>Wirth MA, Jensen KL, Agarwal A, Curtis RJ, Rockwood CA, Jr. Fracture-dislocation of the proximal part of the humerus with retroperitoneal displacement of the humeral head. A case report. J Bone Joint Surg Am 1997;79:763-6.</ref>

Osseous defects of the anterior glenoid rim can be classified into three types according to their pathomorphology. In particular, acute (type I) and chronic glenoid rim defects (type II and III) are differentiated, which are provoked either by an acute glenoid fracture or recurrent shoulder dislocations with subsequent erosion of the glenoid rim. Type I lesions are further divided into bony Bankart lesions (type Ia), solitary glenoid rim fractures (type Ib) and multifragmented glenoid rim fractures (type Ic). In most cases, type I glenoid defects can sufficiently be reconstructed by mobilization and anatomical refixation of the fragment.

In cases of complex multifragmented glenoid rim fractures (type Ic), however, it may be necessary to resect the fragments and augment the glenoid defect. Type II defects include chronic fragment-type of lesions that are characterized by an extra-anatomically consolidated or pseudarthrotic fragment of insufficient dimensions for a defect reconstruction due to resorption processes. A bony glenoid augmentation may be indicated, depending on the dimensions of the glenoid defect and the remaining fragment. Erosion-type of defects (type III) are predominantly observed in patients with recurrent anterior shoulder dislocations. These usually develop on the basis of a glenoid fracture with subsequent resorption of the fragment, or as a result of chronic abrasion of the anterior glenoid rim. If the bone loss adopts substantial dimensions, mere soft-tissue stabilization procedures are not sufficient in re-establishing stability.

==Clinical Presentation and Essential Physical Examination==
The history should document age, hand dominance, occupation, participation in sporting activities, initial mechanism of the injury, the position of the arm (extension, abduction, and external rotation favors anterior dislocation), how long the shoulder stays out, the method of reduction, the number of recurrences (frank dislocation vs subluxation), and the effectiveness of a previous nonoperative or operative treatment. The diagnosis of recurrent traumatic anterior glenohumeral instability is usually made easily on the basis of the history, radiographs, and a positive apprehension sign. However, when collision athletes are seen, care should be taken because they may not experience clear dislocation or subluxation and only complain of pain or weakness.

A comprehensive physical examination is essential. The aim is to define the direction of instability, the presence of an associated pathologic hyperlaxity, and to exclude neurological and rotator cuff impairment. Passive and active glenohumeral range of motion should be assessed. Rotator cuff examination includes strength tests such as belly-press, bear hug, Jobe tests and strength in external rotation against resistance (please refer to Rotator Cuff Pathology/Rotator cuff complete lesion). Tests for anterior and superior labral lesions are not systematically performed as they have a poor sensitivity and specificity.<ref>Cook C, Beaty S, Kissenberth MJ, Siffri P, Pill SG, Hawkins RJ. Diagnostic accuracy of five orthopedic clinical tests for diagnosis of superior labrum anterior posterior (SLAP) lesions. J Shoulder Elbow Surg 2012;21:13-22.</ref>

The neurovascular status of the upper extremity is assessed, particularly with regard to the axillary nerve since there is a high incidence of injury to this nerve with traumatic instability (Figure).
[[File:1562529745788-lg.jpg|thumb|600x600px|A) A 54-year-old patient sustained a fracture dislocation of the right shoulder. At clinical examination, no peripheral pulse was palpated. B) During open reduction, the axillary artery (white arrows) was found kinked around the fractured humeral head.|alt=|border]]
Laxity is a normal, physiologic and asymptomatic finding, that corresponds to translation of the humeral head in any direction to the glenoid.<ref>Gerber C, Terrier F, Ganz R. The Trillat procedure for recurrent anterior instability of the shoulder. J Bone Joint Surg Br 1988;70:130-4.</ref>

Laxity is assessed with the sulcus sign, anterior-posterior drawer, hyperabduction tests, and external rotation elbow at side. The two former tests are only qualitative and are not routinely performed by the authors. Hyperlaxity is constitutional, multidirectional, bilateral and asymptomatic. Hyperlaxity of the shoulder is probably best defined as external rotation elbow at the side equal or greater than 85 degrees.<ref>Walch G, Agostini JY, Levigne C, Nove-Josserand L. [Recurrent anterior and multidirectional instability of the shoulder]. Rev Chir Orthop Reparatrice Appar Mot 1995;81:682-90.</ref>

This non-pathological finding is a risk factor for instability but does not by itself demand treatment unless there is clear pathological laxity. Pathological laxity of the inferior glenohumeral ligament is observed when passive abduction in neutral rotation in the glenohumeral joint is above 105 degrees, there is apprehension above 90 degrees of abduction, or if a difference of more than 20 degrees between the two shoulders is noted.<ref>Gagey OJ, Gagey N. The hyperabduction test. J Bone Joint Surg Br 2001;83:69-74.</ref><ref name="HoveliusRahme2016Primary">Hovelius L, Rahme H. Primary anterior dislocation of the shoulder: long-term prognosis at the age of 40 years or younger. Knee Surg Sports Traumatol Arthrosc 2016;24:330-42.</ref>

For apprehension the patient is initially invited to demonstrate his or her functional problem to the examiner (no-touch examination). This examination alone, coupled with a good history, often provides the information needed. However, if the direction of the instability remains unclear, the apprehension (crank) test, an abducted and externally rotated position suggestive of anterior instability is performed. Fear of dislocation or a feeling of anterior pain is considered positive for damage to the anterior capsulolabral complex, which should be relieved with posterior translation of the humerus (relocation maneuver). To summarize, the physical examination demonstrates instability if the apprehension test is positive, multidirectional hyperlaxity when the external rotation at side is equal or above 85 degrees, and a pathological laxity of the inferior glenohumeral ligament if the hyperabduction test is positive.

==Apprehension==
Apprehension can be difficult to diagnose pre- or post-operatively, as it seems more complex than a pure mechanical problem of the shoulder. Although clinical definition seems to be well established, its underlying pathologic mechanism remains unclear. This may explain the wide reported range (3% to 51%) of patients with ongoing apprehension or who will avoid any shoulder movement after an open or arthroscopic stabilization, despite a clinically stable joint.<ref name="HoveliusRahme2016Primary" /><ref>Hovelius L, Vikerfors O, Olofsson A, Svensson O, Rahme H. Bristow-Latarjet and Bankart: a comparative study of shoulder stabilization in 185 shoulders during a seventeen-year follow-up. J Shoulder Elbow Surg 2011;20:1095-101.</ref><ref name=":14">Lädermann A, Lubbeke A, Stern R, Cunningham G, Bellotti V, Gazielly DF. Risk factors for dislocation arthropathy after Latarjet procedure: a long-term study. International orthopaedics 2013;37:1093-8.</ref>

Failure to recognize and adequately address this issue may result in poor outcome and lead to unnecessary surgery or even revision. Furthermore, identifying this condition may allow establishing adequately targeted rehabilitation programs.

===Definition===
An important aspect to incorporate in dislocation management is apprehension, defined as anxiety and motor resistance in patients with a history of anterior glenohumeral instability. Clinically, apprehension sign is defined as fear of imminent dislocation when placing the arm in abduction and external rotation, and should be distinct from mere pain which can be related to inflammation, stiffness and other shoulder pathologies.<ref>Jobe FW, Kvitne RS, Giangarra CE. Shoulder pain in the overhand or throwing athlete. The relationship of anterior instability and rotator cuff impingement. Orthop Rev 1989;18:963-75.</ref><ref>Rowe CR, Zarins B. Recurrent transient subluxation of the shoulder. The Journal of bone and joint surgery American volume 1981;63:863-72.</ref>

Proprioception, as defined by Charles Scott Sherrington, is the sense of the relative position of neighboring parts of the body and strength of effort being employed during movement.<ref>Sherrington C. The Integrative Action of the Nervous System. New York: Charles Scribner's Sons; 1906.</ref>

It is distinct from exteroception, by which one perceives the outside world, and interoception, by which one perceives pain, hunger, or the movement of internal organs. The brain integrates information from proprioception and from the vestibular system into its overall sense of body position, movement, and acceleration. Kinesthesia refers either to the brain's integration of proprioceptive or vestibular inputs.

===“Localization” of Apprehension===
The pathogenesis of apprehension is not fully understood. Theoretically, apprehension could be related to:

1) Brain changes induced by dislocations<ref name=":9" /><ref>Cunningham G, Zanchi D, Emmert K, Kopel R, Van De Ville D, Lädermann A, Haller S, Hoffmeyer P. Neural Correlates of Clinical Scores in Patients with Anterior Shoulder Apprehension. Medicine and science in sports and exercise 2015;47:2612-20.</ref><ref name=":15">Zanchi D, Cunningham G, Lädermann A, Ozturk M, Hoffmeyer P, Haller S. Structural white matter and functional connectivity alterations in patients with shoulder apprehension. Sci Rep 2017;7:42327.</ref><ref name=":16">Zanchi D, Cunningham G, Lädermann A, Ozturk M, Hoffmeyer P, Haller S. Brain activity in the right-frontal pole and lateral occipital cortex predicts successful post-operatory outcome after surgery for anterior glenoumeral instability. Sci Rep 2017;7:498.</ref>

2) Peripheral neuromuscular lesions consecutive to dislocation affecting proprioception<ref name=":17">Atef A, El-Tantawy A, Gad H, Hefeda M. Prevalence of associated injuries after anterior shoulder dislocation: a prospective study. International orthopaedics 2015.</ref>

3) Persistent mechanical instability consisting in micro-motion<ref name=":19">Lädermann A, Denard PJ, Tirefort J, Kolo FC, Chagué S, Cunningham G, Charbonnier C. Does surgery for instability of the shoulder truly stabilize the glenohumeral joint?: A prospective comparative cohort study. Medicine (Baltimore) 2016;95:e4369.</ref>
[[File:1562540576908-lg.jpg|center|thumb|600x600px|Apprehension may be related to (A) central nervous system sequelae, (B) peripheral neurological, muscular or capsular/ligamentous lesions consecutively to dislocation, or (C) mechanical instability as micromovements. Reproduced from Lädermann et al., with permission.]]

====Brain====
Fear, anxiety and anticipation of situations that could lead to a dislocation are essential cognitive processes in shoulder apprehension. Functional magnetic resonance imaging (fMRI) measures brain activity by detecting changes associated with blood flow.<ref>Logothetis NK, Pauls J, Augath M, Trinath T, Oeltermann A. Neurophysiological investigation of the basis of the fMRI signal. Nature 2001;412:150-7.</ref>

When exploring neuronal connections and cerebral changes induced by shoulder dislocation, research revealed that several cerebral areas are modified, representing the different aspects of shoulder apprehension. Specific reorganizations are found in apprehension-related functional connectivity of the primary sensory-motor areas (motor resistance), dorsolateral prefrontal cortex (cognitive control of motor behavior), and the dorsal anterior cingulate cortex/dorsomedial prefrontal cortex and anterior insula (anxiety and emotional regulation) (Figure).<ref name=":9" />
[[File:1562542592373-lg.gif|center|thumb|450x450px|Patients vs control participants had a significantly (P < .05 corrected) higher task-correlated functional connectivity in two almost mirror symmetric components. Reproduced from Haller et al., with permission.]]
 Those regions are involved in the cognitive control of motor behavior. Hence, there is motor control anticipation and muscular resistance (protective reflex mechanism), in order to avoid shoulder movement that could lead to dislocation.<ref>Cieslik EC, Zilles K, Caspers S, et al. Is there "one" DLPFC in cognitive action control? Evidence for heterogeneity from co-activation-based parcellation. Cereb Cortex 2013;23:2677-89.</ref>

Fractional anisotropy, representing white matter integrity, is increased in the left internal capsule and partially in the thalamus in patients compared to healthy controls. Fractional anisotropy correlated positively with pain visual analog scale (VAS) scores (p < .05) and negatively with simple shoulder test (SST) scores (p < .05).<ref name=":15" />

This suggests an abnormal increased axonal integrity and therefore pathological structural plasticity due to the over-connection of white matter fibers in the motor pathway. These structural alterations affect several dimensions of shoulder apprehension as pain perception and performance in daily life.

Shoulder stabilization could allow the brain to partially “recover”. Patients with shoulder apprehension underwent clinical and functional magnetic resonance imaging (fMRI) examination before and one year after shoulder stabilization surgery. Clinical examination showed a significant improvement in postoperative shoulder function compared with preoperative. Coherently, results showed decreased activation in the left pre-motor cortex postoperatively, demonstrating that stabilization surgery induced improvements both at the physical and at the brain level, one year postoperatively (Figure 9). Most interestingly, right–frontal pole and right-occipital cortex activity is associated with good outcome in shoulder performance.<ref name=":16" />
[[File:1562542592786-lg.gif|center|thumb|400x400px|Task related General Linear Model (GLM) shows higher activation in baseline vs. follow-up for apprehension videos vs. control videos, representing partial brain healing. Reproduced from Zanchi et al., with permission.]]

====Peripheral Neuromuscular Lesion====
During a traumatic dislocation, there are a disruption of the shoulder tendinomuscular (in 10% of cases) and peripheral nerve lesions (in 14% of cases).<ref>Robinson CM, Shur N, Sharpe T, Ray A, Murray IR. Injuries associated with traumatic anterior glenohumeral dislocations. J Bone Joint Surg Am 2012;94:18-26.</ref>

However, this does not account for subclinical neurologic damage that may be much more preponderant. Capsuligamentous structures surrounding the glenohumeral joint are richly innervated with proprioceptors and therefore play an important sensorimotor role in addition to their primary mechanical stabilizising function. Thus, when considering the extensive and frequent damage to these structures after shoulder dislocation (Figure), there is bound to be an important loss in glenohumeral proprioception.<ref name=":5" /><ref name=":17" />

The latter plays a significant role in stabilization of a normal healthy shoulder and after any shoulder injury by contributing to motor control.<ref name=":18">Fyhr C, Gustavsson L, Wassinger C, Sole G. The effects of shoulder injury on kinaesthesia: a systematic review and meta-analysis. Man Ther 2015;20:28-37.</ref>
[[File:1562542594443-lg.jpg|center|thumb|600x600px|Arthroscopic view of a left shoulder through a posterior portal. This patient has sustained more than 50 subluxations. The axillary nerve is clearly identifiable (white asterisk). There is no more capsule or inferior glenohumeral ligament, and the subscapularis muscle is hardly recognizable. Reproduced from Lädermann A, Benchouk S, Denard P. Traumatic Anterior Shoulder Instability: General concepts & proper management. In: Park J, ed. Sports Injuries to the Shoulder and Elbow. Berlin Heidelberg: Springer-Verlag; 2015, with permission.]]
Surgical stabilization has been shown to help proper healing of these structures and thus restoring proprioception of the glenohumeral joint.<ref>Myers JB, Lephart SM. Sensorimotor deficits contributing to glenohumeral instability. Clin Orthop Relat Res 2002:98-104.</ref>

====Glenohumeral Joint====
The third etiologic factor for apprehension is persistent micro-motion in the glenohumeral joint despite a clinically stable shoulder, satisfactory radiographic results, and no new episode of subluxation or dislocation. Shoulder dislocation causes damage to the capsuloligamentous complex in 52% of the cases, and the glenoid labrum in 73% of the cases.<ref>Liavaag S, Stiris MG, Svenningsen S, Enger M, Pripp AH, Brox JI. Capsular lesions with glenohumeral ligament injuries in patients with primary shoulder dislocation: magnetic resonance imaging and magnetic resonance arthrography evaluation. Scandinavian journal of medicine & science in sports 2011;21:e291-7.</ref><ref name=":5" />

The plastic deformation of these structures becomes progressively worse with subsequent episodes.The plastic deformation of these structures becomes progressively worse with subsequent episodes. In addition to progressive soft tissue injury, recurrent dislocations induce bony lesions, which may involve the glenoid (bony Bankart), the posterolateral humeral head (Malgaine), or both. Severity of apprehension, quantified as the moment at which it appears during the course of abduction and external rotation, seems to be correlated to the extent of bone loss. Capsular redundancy has also been recognized as a risk factor for ongoing apprehension after surgical stabilization and Ropars et al. found a significantly decreased apprehension in patients with associated capsulorraphy to Latarjet procedures, compared with patients with Latarjet and no capsular reconstruction.<ref name=":12">Ropars M, Cretual A, Kaila R, Bonan I, Herve A, Thomazeau H. Diagnosis and treatment of anteroinferior capsular redundancy associated with anterior shoulder instability using an open Latarjet procedure and capsulorrhaphy. Knee Surg Sports Traumatol Arthrosc 2016;24:3756-64.</ref>

However, these changes may be very subtle and therefore not detectable on standard clinical magnetic resonance imaging in neutral position. This has been described by Patte et al. in non-operated patients and popularized under the name of "unstable painful shoulder".<ref name=":11" /><ref name=":10" />

This micro-motion may yet still be present after surgical stabilization. Shoulder stabilization may thus only prevent new episodes of dislocation, rather than actually truly stabilizing the shoulder.<ref>Singer GC, Kirkland PM, Emery RJ. Coracoid transposition for recurrent anterior instability of the shoulder. A 20-year follow-up study. J Bone Joint Surg Br 1995;77:73-6.</ref><ref>Lädermann A, Tirefort J, Zanchi D, Haller S, Charbonnier C, Cunningham G. Shoulder Apprehension: a Multifactorial Approach. EFORT Open Rev. 2018 24;3(10):550-557</ref>

A study described glenohumeral translation in patients with traumatic anteroinferior instability and subsequently analyzed the effect of glenohumeral stabilization on this translation. For all movements, the authors recorded humeral head position of the contralateral and ipsilateral shoulders in relation to the glenoid center pre- and 1 year post-operatively. They observed an anterior translation of the humeral head (Figure), especially during flexion and abduction movements (p < .05 and p < .05, respectively). One year after surgery, all patients had a clinically stable shoulder and none presented with a new episode of dislocation or subluxation.

However, anterior translation of the humeral head was not significantly reduced and remained close to preoperative values confirming that shoulder stabilization does not stabilize the shoulder but uniquely prevents further dislocation. These findings have several important implications. First, it may explain residual pain, apprehension, and impossibility to return to sport at the same level as reported in other studies. Second, persistent abnormal motion between the glenoid and the humeral head might be the underlying cause of dislocation arthropathy that is observed with a prevalence of 36%. Repeated sliding of the humeral head against the glenoid associated with degenerative changes of cartilage properties and decreased biological healing potential related to aging, could lead to a vicious circle of extensive cartilage damage.<ref name=":19" />
[[File:1562542595262-lg.jpg|center|thumb|600x600px|(A) Abduction simulation obtained from shoulder’s CT reconstruction and optical motion capture, (B) and (C) show a zoom in the shoulder (front and top views). In image (C), we clearly observe an anterior translation (arrow) of the humeral head center (pink sphere) with respect to the glenoid center (white sphere). Note that the clavicle is not shown for clarity. Reproduced from Lädermann et al., with permission.]]
 

==Scores==

===Single Assessment Numeric Evaluation (SANE)-instability score===
A modified Single Assessment Numeric Evaluation (SANE) score specific to shoulder instability, the SANE-instability score, has been developed.<ref name=":0">Lädermann A, Denard PJ, Collin P, Mohamed Ibrahim M, Bothorel H, Chiu JC. Single Assessment Numeric Evaluation for instability as an alternative to the Rowe score. J Shoulder Elbow Surg. 2020;S1058-2746(20)30686-8</ref> The SANE-instability score (100 points) is assessed with a single question: “What is the overall percent value of your shoulder if a completely stable shoulder represents 100%?” A high correlation between the Rowe and SANE-instability scores for shoulder instability has been found before and after treatment, as well as for different patient age groups and treatment types. This score is easy to collect and use because it can be collected in the office or remotely, thereby saving considerable time and potentially improving compliance.<ref name=":0" />

===Rowe===
The 1978 Rowe score is calculated with the 3 following items: stability (50 points), motion (20 points), and function (30 points).<ref>Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end-result study. J Bone Joint Surg Am. 1978; 60: 1-16</ref>

===Walch-Duplay===
This subsection does not exist. You can ask for it to be created, but consider checking the search results below to see whether the topic is already covered.

===WOSI===
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===ISIS===
Boileau et al. proposed a simple 10-point scale scoring system (instability severity index score (ISIS)) based on factors derived from a pre-operative questionnaire, physical examination, and anteroposterior radiographs to determine the risk of treatment failure following isolated arthroscopic Bankart repair (Table). In this model an ISIS of 3 or less was associated with a 5% rate of recurrence, an ISIS of 4 to 6 was associated with a 10% rate of recurrence, and an ISIS over 6 was associated with a 70% rate of recurrence. Although it has imperfections, this score, validated since, has merit to easily remind the clinician of factors that are important to consider when evaluating a patient.<ref name=":8" /><ref>Rouleau DM, Hebert-Davies J, Djahangiri A, Godbout V, Pelet S, Balg F. Validation of the instability shoulder index score in a multicenter reliability study in 114 consecutive cases. Am J Sports Med 2013;41:278-82.</ref>

'''''Table: The instability severity index score is based on a pre-operative questionnaire, clinical examination, and radiographs.'''''
[[File:1562543299662-lg.jpg|center|thumb|899x899px|Figure. 12 * AP, anteroposterior]]
 

==Essential Radiology==
Radiographic evaluation is based on whether the dislocation is acute or chronic.

===Acute Dislocation===
Three views plain radiographs, including true anteroposterior of the glenohumeral joint, scapular Y (scapular lateral), and Velpeau axillary views are the mainstay of imaging in the setting of traumatic anterior instability.<ref>Bloom MH, Obata WG. Diagnosis of posterior dislocation of the shoulder with use of Velpeau axillary and angle-up roentgenographic views. J Bone Joint Surg Am 1967;49:943-9.</ref>

The latter view is crucial to obtain, as the two first alone do not allowed to exclude a dislocation. The goal is to confirm the direction of dislocation and to evaluate associated lesions. One reduced, further imaging studies in the setting of an associated fracture (computed tomography (CT)), suspicion of rotator cuff injury (ultrasonography or magnetic resonance imaging (MRI)), or vascular impairment (injected CT) may be warranted.

===Preoperative Planning in Case of Recurrent Dislocation===
The first step is to analyze, if available, plan radiographs with the shoulder out of joint to confirm the direction of instability. Plain radiographs including anteroposterior in neutral, internal and external rotations, scapular Y and Bernageau views are then obtained.<ref>Bernageau J, Patte D, Debeyre J, Ferrane J. [Value of the glenoid profile in recurrent luxations of the shoulder]. Rev Chir Orthop Reparatrice Appar Mot 1976;62:142–7.</ref>

Bone loss, static instability, post-dislocation arthropathy, and coracoid non-union (if a Latarjet or a Bristow procedures are planned) have to be estimated. Magnetic resonance imaging (MRI) arthrogram is useful to assess for soft tissue such as an anterior labral tear (Figure). 
[[File:1562543301909-lg.jpg|center|thumb|600x600px|Coronal T1 SPIR magnetic resonance imaging (MRI) of a right shoulder showing disruption of the anteroinferior glenoid labrum. B]]
Associated intra-articular pathology such as SLAP, HAGL, and rotator cuff lesions or a paralabral cyst are also assessed (Figure).

The evaluation is completed by a 3D computed tomography arthrogram in the setting of recurrent instability in which there is primary concern for bone loss. The extent of both glenoid bone loss and Hill-Sachs lesions are best assessed by computed tomography scan and are used to determine the need for a bony procedure as opposed to arthroscopic Bankart repair (Figures).
[[File:1562543901744-lg.jpg|center|thumb|600x600px|A) Sagittal view of a CT arthrogram of a left shoulder demonstrates a significant Bankart fracture that produces an “inverted-pear” glenoid. B) Plain anteroposterior radiograph reveals an anteroinferior glenohumeral dislocation with an “engaged” Malgaigne (Hill-Sachs) lesion of the humerus.]]
 
[[File:1562544592047-lg.jpg|center|thumb|600x600px|Axial computed tomography (CT) arthrogram view showing a large Malgaigne lesion.]]
 

==Treatments==
The degree, nature and combination of injuries induced by traumatic glenohumeral instability are highly variable. Damage to the bony and soft tissue stabilizers of the shoulder, as well as neurologic impairment, must be detected and analyzed in order to provide the patient with the most adequate treatment option. This new knowledge should be applied to rehabilitation therapy and surgical stabilization techniques. As the current stabilization techniques do not seem to prevent residual glenohumeral micro-motion, it remains to be determined which factors help to minimize this phenomenon, whether it is, the increase in the anteroposterior diameter of the glenoid with a bone graft, the sling effect provided by the conjoined tendon or the long head of the biceps, the capsulorraphy, the repaired labrum or the remplissage.<ref>Lädermann A, Bohm E, Tay E, Scheibel M. Bone-mediated anteroinferior glenohumeral instability : Current concepts. Der Orthopade 2018.</ref><ref name=":13">Collin P, Lädermann A. Dynamic Anterior Stabilization Using the Long Head of the Biceps for Anteroinferior Glenohumeral Instability. Arthrosc Tech 2018;7:e39-e44.</ref><ref>Young AA, Maia R, Berhouet J, Walch G. Open Latarjet procedure for management of bone loss in anterior instability of the glenohumeral joint. J Shoulder Elbow Surg 2011;20:S61-9.</ref><ref name=":12" />

===Methods of Reduction===
Around 400 BC, Hippocrates, the father of Western medicine, introduced the traction method to reduce the shoulder. The patient lay supine whilst the physician standing on the patient's affected side held the arm and applied traction. The stockinged foot of the physician placed in the axilla served as counter traction. This technique was detailed in the Hippocratic Corpus, and as it remained the primary medical text for centuries so did the method. Similar technique of reduction was re-introduced in the 1870 as a painless technique by Theodor Kocher, but is now obsolete because of the likelihood of serious complications.<ref>Kocher E. Eine neue Reductionsmethode für Schulterverrenkung. Berlin Klin 1870;7:101-5.</ref>

===Conservative (Nonoperative) Treatment===
Heading towards a better understanding of the complex and multifactorial origins of glenohumeral instability and apprehension, postoperative management may in turn also be improved, notably in challenging cases of patients with persistent apprehension, despite a clinically stable shoulder. Knowing that shoulder apprehension could be the result of ongoing cerebral abnormalities or residual micro-motion may avoid costly series of onerous investigations, useless physiotherapy sessions or even re-operations. Furthermore, this perspective offers a new angle of a therapeutic approach that differs from conventional manual rehabilitation methods centered on the glenohumeral joint itself. If persistent apprehension or micro-motion is detected, growing research evidence supports the use of a multidisciplinary approach including:

1) A "reafferentation" (reconveying and connecting the neurological peripheral input to the cortex)89 of the shoulder particularly focused on proprioceptive work,69 which has been proved to lead to superior neuromuscular control than strengthening alone.<ref>Horvat JC. [Reconstruction of the spinal cord and its motor connections using embryonal nervous tissue transplantation and peripheral nerve autotransplantation. A study in the adult rat]. Neurochirurgie 1991;37:303-11.</ref><ref>Salles JI, Velasques B, Cossich V, Nicoliche E, Ribeiro P, Amaral MV, Motta G. Strength training and shoulder proprioception. J Athl Train 2015;50:277-80.</ref><ref name=":18" />

2) A biofeedback therapy where the patient directly visualizes his abnormal response to a negative stimulus on fMRI or electroencephalogram, and can thereby actively correct it. This treatment modality has already shown to improve shoulder control and performance in various settings.<ref>deCharms RC, Maeda F, Glover GH, Ludlow D, Pauly JM, Soneji D, Gabrieli JD, Mackey SC. Control over brain activation and pain learned by using real-time functional MRI. Proceedings of the National Academy of Sciences of the United States of America 2005;102:18626-31.</ref><ref>Antunes A, Carnide F, Matias R. Real-time kinematic biofeedback improves scapulothoracic control and performance during scapular-focused exercises: A single-blind randomized controlled laboratory study. Hum Mov Sci 2016;48:44-53.</ref><ref>Huang HY, Lin JJ, Guo YL, Wang WT, Chen YJ. EMG biofeedback effectiveness to alter muscle activity pattern and scapular kinematics in subjects with and without shoulder impingement. J Electromyogr Kinesiol 2013;23:267-74.</ref>

3) A cognitive behavioral approach to decondition this pathological residual apprehension by making them realize residual apprehension does not necessarily lead to recurrent instability with gradual exposition that has already shown successful results in the treatment of kinesiophobia,94-96 a condition based on a re-injury fear-avoidance model initially described in low-back pain,97 further popularized in sports medicine98 and various upper limb conditions.<ref>Das De S, Vranceanu AM, Ring DC. Contribution of kinesophobia and catastrophic thinking to upper-extremity-specific disability. J Bone Joint Surg Am 2013;95:76-81.</ref>

4) Electric stimulation of hypoactive rotator cuff and periscapular muscles.<ref>Moroder P, Minkus M, Bohm E, Danzinger V, Gerhardt C, Scheibel M. Use of shoulder pacemaker for treatment of functional shoulder instability: Proof of concept. Obere Extrem 2017;12:103-8.</ref>

===Treatment of Acute First Traumatic Dislocations===
The first step, whenever possible, is to obtain a complete set of radiographs before attempting a reduction. This will allow an assessment of the type of dislocation and associated bone injuries. Attempting to reduce a fracture dislocation can have troublesome clinical and legal consequences (Figure).
[[File:1562546209492-lg.jpg|center|thumb|600x600px|A) An anteroposterior plain radiograph of a left shoulder shows an anterior dislocation with a nondisplaced humeral neck fracture on the prereduction radiographs. B) Radiographs after attempting a closed reduction without adequate muscle relaxation reveal displacement of the fracture with the humeral head remaining anteriorly.]]
Exceptions are an impossibility to have reasonably fast access to radiology or a patient with neurological impairment. Because of the possible association of nerve injuries and, to a lesser extent, vascular injuries (Figure), an essential part of the physical examination is an assessment of the neurovascular status of the upper extremity before reduction.<ref>de Laat EA, Visser CP, Coene LN, Pahlplatz PV, Tavy DL. Nerve lesions in primary shoulder dislocations and humeral neck fractures. A prospective clinical and EMG study. J Bone Joint Surg Br 1994;76:381-3.</ref><ref>Brown FW, Navigato WJ. Rupture of the axillary artery and brachial plexus palsy associated with anterior dislocation of the shoulder. Report of a case with successful vascular repair. Clin Orthop Relat Res 1968;60:195-9.</ref>
[[File:1562529745788-lg.jpg|center|thumb|600x600px|A) A 54-year-old patient sustained a fracture dislocation of the right shoulder. At clinical examination, no peripheral pulse was palpated. B) During open reduction, the axillary artery (white arrows) was found kinked around the fractured humeral head.]]
They are numerus appropriate methods of reduction that have been described. The second step is to use the technique of closed reduction which is mastered by the doctor who will perform the maneuver. The glenohumeral joint should be reduced as gently and expeditiously as possible. In the case of fracture dislocation, the reduction is best performed under general anesthesia to have adequate muscle relaxation. After reducing the dislocation, plain radiographs are obtained to verify the adequacy of the reduction.

Results concerning conservative treatment are still debatable. A stable shoulder is obtained at ten years in only half of patients with conservative treatment.<ref name=":7" />

However, recurrence rate is highly dependent on age and activity of the patient; studies have reported a 72% to 95% recurrence in patients under 20 years of age, and 70% to 82% recurrence between the ages of 20 and 30 years, and only 30% in those over 30 years of age.<ref>te Slaa RL, Brand R, Marti RK. A prospective arthroscopic study of acute first-time anterior shoulder dislocation in the young: a five-year follow-up study. J Shoulder Elbow Surg 2003;12:529-34.</ref><ref name=":6" /><ref>Robinson CM, Howes J, Murdoch H, Will E, Graham C. Functional outcome and risk of recurrent instability after primary traumatic anterior shoulder dislocation in young patients. J Bone Joint Surg Am 2006;88:2326-36.</ref>

Many patients above the age of 30 would consequently undergo unnecessary surgery if proposed after the first dislocation. Conservative treatment after the first traumatic anterior dislocation may be thus recommended for patients who are not actively engaged in sports, above the age of 30 years old, with a low functional demand, with an associated humeral fracture, or for the athlete with an in-season shoulder dislocation. For the latter situation, athletes are allowed to attempt to return to competition provided there is enough time left in the season to permit adequate rehabilitation with progression to sport-specific drills.

Rehabilitation, including return of range of motion and strengthening of dynamic stabilizers may facilitate return to sport within several weeks. Motion-limiting braces that prevent extreme shoulder abduction, extension, and external rotation are often prescribed as it may reduce the risk of recurrence. However, such braces are not well-tolerated in patients who must complete certain overhead tasks such as throwing. Moreover, a second in-season shoulder dislocation should lead to removal from sport and proceeding with stabilization so as to avoid further glenohumeral damage.

A number of studies have compared nonoperative treatment and arthroscopic stabilization. Overall, these studies report a sevenfold reduction in the risk of recurrent instability after arthroscopic stabilization, when compared with nonoperative treatment for the first-time dislocator.<ref>Murray IR, Ahmed I, White NJ, Robinson CM. Traumatic anterior shoulder instability in the athlete. Scandinavian journal of medicine & science in sports 2013;23:387-405.</ref>

A Cochrane review concluded that early surgical intervention is warranted in young adults aged less than 30 years engaged in highly demanding physical activities.<ref>Handoll HH, Almaiyah MA, Rangan A. Surgical versus non-surgical treatment for acute anterior shoulder dislocation. The Cochrane database of systematic reviews 2004:CD004325</ref>

Consequently, for patients who are actively engaging in a collision or contact or overhead sport, who risk their life in case a new dislocation (e.g. firemen, proponents of extreme sports like base jumping, and climbing), with associated static anterior subluxation, an interposed tissue or a nonconcentric reduction, or patients with rotator cuff avulsion, conservative measures are usually inadequate and prompt surgery is indicated.

===Surgical (Operative) Treatment===
Recurrent dislocation is not trivial. Each episode creates new lesions and increases the risk of developing dislocation arthropathy. The concept of early operative surgical management of the first-time dislocator has consequently been introduced to address the high recurrence rate in the young athletic population. Surgery should be proposed, as having the ultimate aim to achieve a pain-free stable shoulder while preserving range of motion. The surgical approach is based on the extent of bone loss and patient-specific risk factors for recurrence.

====Soft tissue procedures====
=====Bankart and Associate Repairs=====
The aim of a Bankart repair is to restore anatomy by reattaching the labrum to the glenoid (Figure) and tighten the inferior glenohumeral ligament by shifting from inferior to superior. Several technical factors are also important to success. It is important to place anchors at the margin of the articular surface (as opposed to the glenoid neck) to allow recreation of the labral bumper. The surgeon must be sure to obtain a proper inferior to superior shift of the capsule (Neer’s modification). Although this surgery can be performed in an open manner, the advantage of an arthroscopic approach is that it preserves the subscapularis and allows assessment of associated pathology. The literature demonstrates that patients with low risk of recurrence will benefit from either an anatomic open or arthroscopic repair with an acceptable rate of recurrence.<ref>Harris JD, Gupta AK, Mall NA, Abrams GD, McCormick FM, Cole BJ, Bach BR Jr, Romeo AA, Verma NN. Long-term outcomes after Bankart shoulder stabilization. Arthroscopy 2013;29:920-33.</ref>
[[File:1562546210935-lg.jpg|center|thumb|600x600px|Illustration of a Bankart repair (sagittal view of a right shoulder). Courtesy of Gilles Walch.]]

HAGL (Humeral Avulsion of the Glenohumeral Ligaments) lesions are uncommon causes of anterior instability. There are 3 variants of HAGL lesions: 1. Avulsion from bone 2. Capsular split 3. Combined bone avulsion and capsular split. These lesions can be addressed by repair or more easily by a Latarjet.

=====Remplissage=====
Remplissage has been described by Connoly and may be used as an adjunct to arthroscopic Bankart repair in the setting a of large Malgaigne (Hill-Sachs) lesion with glenoid bone loss of <25%.<ref>Connoly J. Humeral head defects associated with shoulder dislocations. American Academy of Orthopaedic Surgeons Instructional course lectures: Mosby; 1972:42-54.</ref>

This technique consists of a posterior capsulodesis and infraspinatus tenodesis that fills the Malgaigne lesion. The purpose is to render the Malgaigne lesion extra-capsular, avoiding its engagement. Wolf et al. and Boileau et al. presented encouraging mid- to long-term results of arthroscopic remplissage and concomitant anterior Bankart repair.<ref name=":20">Boileau P, O'Shea K, Vargas P, Pinedo M, Old J, Zumstein M. Anatomical and functional results after arthroscopic Hill-Sachs remplissage. J Bone Joint Surg Am 2012;94:618-26.</ref><ref name=":21">Wolf EM, Arianjam A. Hill-Sachs remplissage, an arthroscopic solution for the engaging Hill-Sachs lesion: 2- to 10-year follow-up and incidence of recurrence. J Shoulder Elbow Surg 2014;23:814-20.</ref>

Surgical Technique
The arthroscope can typically remain in the posterior portal because the 70 degrees angle enhances appropriate visualization. Depending on patient anatomy, the arthroscope can be switched to the anterolateral portal to obtain another view of the defect. A spinal needle is centered over the Malgaigne (Hill-Sachs) lesion, and an accessory posterolateral portal is created 2 fingerbreadths lateral to the posterior viewing portal to allow orthogonal insertion of suture anchors. The use of a cannula is optional. A shaver is used to abrade the Malgaigne (Hill-Sachs) lesion. Two anchors are inserted in the valley of the defect adjacent to the articular margin, 1 superior and 1 inferior. If used, the cannula is at this point retracted into the subdeltoid space. A curved penetrating grasper is used to retrieve the inferior anchor suture, followed by a straight penetrating grasper for the superior anchor suture. The humeral head is reduced, and the inferior sutures are tied in mattress fashion in the subdeltoid space, followed by the superior sutures, to complete the remplissage.

=====Subscapularis Tendon Augmentation or Capsular Reconstruction=====
When traditional arthroscopic Bankart repair is not possible due to severe capsulolabral deficiency, different types of open or arthroscopic subscapularis tendon augmentation or capsular reconstruction have been described.<ref name=":27">Denard PJ, Narbona P, Lädermann A, Burkhart SS. Bankart augmentation for capsulolabral deficiency using a split subscapularis tendon flap. Arthroscopy 2011;27:1135-41.</ref><ref>Maiotti M, Massoni C, Russo R, Schroter S, Zanini A, Bianchedi D. Arthroscopic Subscapularis Augmentation of Bankart Repair in Chronic Anterior Shoulder Instability With Bone Loss Less Than 25% and Capsular Deficiency: Clinical Multicenter Study. Arthroscopy 2016.</ref><ref>Maiotti M, Russo R, Zanini A, Schroter S, Massoni C, Bianchedi D. Arthroscopic Bankart repair and subscapularis augmentation: an alternative technique treating anterior shoulder instability with bone loss. J Shoulder Elbow Surg 2016;25:898-906.</ref><ref>Russo R, Della Rotonda G, Cautiero F, Ciccarelli M, Maiotti M, Massoni C, Di Pietto F, Zappia M. Arthroscopic Bankart repair asciated with subscapularis augmentation (ASA) versus open Latarjet to treat recurrent anterior shoulder instability with moderate glenoid bone loss: clinical comparison of two series. Musculoskelet Surg 2016.</ref>

[[File:1562546211256-lg.jpg|center|thumb|609x609px|Bankart augmentation with split subscapularis tendon transfer. (A) A flap of the posterior portion of the superior half of the subscapularis tendon is created. (B) The subscapularis flap is mobilized in a trapdoor fashion such that the capsular surface of the subscapularis tendon is reflected from medial to lateral as a separate lamina while the outer surface is left unaltered. Note, arrows in (A) and (B) point to the free margin of the subscapularis tendon flap. (C) The subscapularis flap undergoes tenodesis to the anterior glenoid suture anchors to augment capsulolabral deficiency. Reproduced from Denard et al.,<ref name=":27" /> with permission.|alt=]]

Surgical technique
A standard diagnostic arthroscopy is performed with a 30 degrees arthroscope, viewing through a posterior portal with a pump maintaining pressure of 50 mm Hg. The labrum is inspected in its entirety. An anterior portal is established just above the lateral half of the subscapularis and medial to the sling of the biceps, by use of an 18-gauge spinal needle with an outside-in technique. An anterosuperolateral portal is similarly established off the anterolateral border of the acromion. This portal should be placed so that it provides a 45 degrees angle of approach to the superior glenoid. The arthroscope is placed in the anterosuperolateral portal, and the anterior labrum is more thoroughly inspected. The remaining capsulolabral sleeve is dissected from the glenoid neck with an arthroscopic elevator until the subscapularis muscle is visible deep to the cleft. A 2- to 3-mm strip of articular cartilage is removed along the glenoid rim with a ring curette, creating an enhanced bone bed for capsulolabral repair. A capsulolabral repair is performed inferiorly with whatever good tissue remains. An anteroinferior anchor is placed. After placement of this anchor, if there is insufficient capsulolabral tissue to create the desired “bumper” along the anterior glenoid rim, the surgeon must consider various reconstructive options, including a split subscapularis tendon flap.

=====Augmentation With Split Subscapularis Flap=====
To augment the capsulolabral deficiency, a flap of the posterior portion of the superior half of the subscapularis tendon is mobilized and undergoes tenodesis to the anterior glenoid. This flap is created in a “trapdoor” fashion such that the capsular surface of the subscapularis tendon is reflected from medial to lateral as a separate lamina while the outer surface in left unaltered. By use of arthroscopic scissors introduced through the anterior portal, a longitudinal incision through one-half the thickness of the subscapularis is created in the superior half of the tendon (Figure).
[[File:1562547676763-lg.jpg|center|thumb|600x600px|Left shoulder, anterosuperolateral viewing portal, showing creation of a split subscapularis flap to augment a Bankart repair in the setting of capsulolabral deficiency. The flap is created with arthroscopic scissors introduced through an anterior portal. Suture is also seen from an inferior Bankart repair (arrow). (SSc, subscapularis tendon.). Reproduced from Denard et al.<ref name=":27" />, with permission.]]

Care is taken not to violate the full thickness of the subscapularis. The subscapularis flap dissection progresses from medial to lateral until the leading medial edge of the flap is mobile enough to reach the anterior glenoid. After mobilization of the subscapularis tendon flap, additional suture anchors are placed on the previously prepared glenoid strip at the 3-o'clock and 4-o'clock positions. Sutures from the anchor are passed through the subscapularis flap and tied as described previously. This completes the augmentation with a split subscapularis tendon flap (Figure).

[[File:1562547677981-lg.jpg|center|thumb|1071x1071px|Left shoulder, anterosuperolateral viewing portal, showing completed arthroscopic Bankart repair augmented with a split subscapularis flap in the setting of capsulolabral deficiency. (A) Completed repair showing restoration of anterior soft tissue by use of the split subscapularis tendon (SSc) flap. (B) The split between the subscapularis (arrow) is visualized anterior to the flap that has undergone tenodesis. (G, glenoid; H, humeral head.). Reproduced from Denard et al.,<ref name=":27" /> with permission.]]

Postoperatively, the patient's extremity is placed in a sling for 6 weeks. At the end of six weeks, stretching exercises are commenced with full forward flexion allowed and external rotation to half that of the contralateral shoulder. The goal is to achieve half the external rotation of the normal side at three months postoperatively. Strengthening is delayed until four months postoperatively because this is usually a last-resort salvage procedure. Return to full activities is delayed until one year postoperatively.

=====Dynamic Anterior Stabilization (DAS)=====
[[File:1562547970547-lg.mp4|center|thumb|600x600px|Video]]

Dynamic anterior stabilization transfers the long head of the biceps to the anterior glenoid margin, thereby creating a “sling effect” (Figure).
[[File:1562547677283-lg.jpg|center|thumb|700x700px|(A) Native shoulder. (B) Latarjet procedure. The coracoid graft including the conjoint tendon is secured to the anterior glenoid by means of two 4.5-mm screws. (C) Dynamic anterior stabilization. The long head of the biceps is transferred to the anterior glenoid margin. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]
 The dynamic anterior stabilization technique provides decreased anterior glenohumeral translation in cases of Bankart lesions with limited anterior bone loss (<20%)<ref>Mehl J, Otto A, Imhoff FB, Murphy M, Dyrna F, Obopilwe E, Cote M, Lädermann A, Collin P, Beitzel K, Mazzocca AD. Dynamic Anterior Shoulder Stabilization With the Long Head of the Biceps Tendon: A Biomechanical Study. Am J Sports Med. 2019 May;47(6):1441-1450.</ref>

In comparison with isolated Bankart repair, it is able to stop the anterior translation less anterior and therefore reduces the risk of a conflict between the humeral head and the anterior margin of the glenoid. It is also easier and safer than arthroscopic Latarjet. Moreover, it does not require screws nor traction of the coracoid process, and should consequently reduce the risks of neurologic damage. Furthermore, the procedure can be performed with only 3 small incisions (Video), as it does not require coracoid transfer, which eliminates risks of nerve dissection, graft overhang and cortical resorption, hence reducing the probability for dislocation arthroplasty. Lastly, the pectoralis minor remains intact, which would avoid scapular dyskinesis. The potential drawbacks of the dynamic anterior stabilization are that it relies on the long head of biceps tendon, which has smaller diameter than the conjoint tendon and could therefore have a weaker “sling effect” than that of the standard Latarjet. Also, there are, like in the Latarjet procedure, the risks of biceps pain, and secondary iatrogenic factors. Furthermore, in cases with larger bone defects (≥ 20 %) there is a relevant posterior and inferior shift of the humeral head in relation to the glenoid, when the arm is brought in the ABER position.(reference to be completed) Indications and limitations are yet to be defined. MRI scans showed that the transposed long head of the biceps successfully healed to the glenoid rim and remained intact at the 6- and 12-month follow-ups in patients who underwent dynamic anterior stabilization for the treatment of chronic anteroinferior glenohumeral instability with bipolar and/or SLAP II lesions with limited (<13.5%) to subcritical (13.5%—25%) glenoid bone loss.<ref name=":28">de Campos Azevedo C, Ângelo AC. All-Suture Anchor Dynamic Anterior Stabilization Produced Successful Healing of the Biceps Tendon: A Report of 3 Cases. JBJS Case Connect . 2021:17;11(1)</ref> However, it is recommended that future studies are carried out with a more long-term follow-up.

Preoperative Patient Positioning
The operation, illustrated in the video, is performed in the semi-beach chair position under general anesthesia with an interscalene block. An examination under anesthesia is performed before prepping and draping the arm.

Initial Exposure and Portal Placement
An intra-articular approach is used through a standard posterior portal (soft spot), a standard diagnostic arthroscopy is performed with a 30-degree arthroscope and a pump maintaining pressure at 60 mm Hg. Antero-lateral and anterior portals are then established by an outside-in technique using a spinal needle as a guide. The rotator interval is opened, and the internal structures (glenoid defects, humeral defects, etc.) are further assessed with a probe.

Anterior Glenoid Preparation
From a lateral viewing portal, the labrum, if necessary, is detached from the glenoid, and a suture is passed around the labrum and pulled through the posterior portal to increase access for preparation of the anterior glenoid (Figure). The glenoid neck is cleaned from soft tissues at around 3 o’clock with a burr.

[[File:1562549774413-lg.jpg|center|thumb|600x600px|Intra-articular view of a right shoulder, anterolateral viewing portal. A suture is passed around the detached labrum and pulled through the posterior portal to increase access for preparation of the anterior glenoid. ∗ indicates the labrum, the black arrows the access to the glenoid neck, and HH the humeral head. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

Addressing the Long Head of Biceps and Subscapularis Split
The long head of biceps is then tenotomized and the biciptal groove is opened laterally and distally to avoid detaching the subscapularis (Figure).
[[File:1562549775232-lg.jpg|center|thumb|600x600px|Retrocoracoid space of a right shoulder, anterolateral viewing portal. After LHB tenotomy, the bicipital sheath (black arrows) is opened laterally and the LHB (∗) is found. (CT, conjoint tendon; LHB, long head of the biceps.). Reproduced from Collin et al.,<ref name=":13" /> with permission.]]
The biceps is then exteriorized, and secured 20 mm from the proximal tendon. From a lateral viewing portal the subscapularis is exposed on three sides, together with the lateral margin of the conjoint tendon. Three options exist to create a split in the middle of the subscapularis above the junction of the superior two-thirds used in the standard Latarjet procedure: From a lateral viewing portal, either a switching stick (Wissinger Rod) can be passed across the glenohumeral joint through a posterior approach at the level of the inferior glenoid (Figure), an outside-in approach can be used or simply by passing through the subscapularis muscle with a suture passer, by grabbing the sutures that secure the biceps and pulling the biceps through the tendon.

[[File:1562549776269-lg.jpg|center|thumb|600x600px|Intraoperative view of a right shoulder with passage of the switching stick (∗) across the glenohumeral joint at the level of the inferior glenoid to the subscapularis. (HH, humeral head). Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

The switching stick is now found in the retrocoracoid space and maintained lateral to the conjoint tendon to avoid damaging the nerve plexus. The probe is then introduced through the anterior portal to complete the split.

Long Head of Biceps Tenodesis to Anterior Glenoid
A drill is then used to prepare a hole at 3 o'clock from anterior to posterior within the neck of the glenoid, 2.0 cm deep, depending on the length of the interference screw. The LHB tendon is then passed through the subscapularis split into the pre-drilled hole, to establish the “sling effect”, and fixed using a tenodesis screw (Figure).

[[File:1562549775588-lg.jpg|center|thumb|600x600px|Intraoperative view of a right shoulder through the subscapularis split, anterolateral viewing portal. The long head of the biceps tendon (black arrow) is fixed using a tenodesis screw (∗) to establish the “sling effect”. Reproduced from Collin et al.<ref name=":13" />, with permission.]]

Alternatively, the biceps may be managed without exteriorization, as shown in the linked video.[https://www.vumedi.com/video/all-suture-anchor-double-double-pulley-dynamic-anterior-stabilization/] When choosing this technical variant, two all-suture anchors (double loaded with sutures) must me placed on the glenoid rim and each of the respective eight suture limbs must be passed through the biceps before the tenotomy is completed; a double-pulley technique is used to shuttle the biceps through the subscapularis tendon split to the anteroinferior glenoid; the biceps is fixed to the glenoid with a total of four knots (Figure).

[[File:Figure 4 jpeg.jpg|none|thumb|959x959px|Representation of the posterior portal arthroscopic view of the trans-subscapular transposition of the long head of the biceps using the double double-pulley on a right shoulder in the beach chair position. A) Two knots of the double double-pulley are tied after all suture limbs were passed through the long head of the biceps (LHB) tendon; B) the remaining 4 opposing suture limbs are pulled and the LHB tendon reaches the anteroinferior glenoid rim after passing through the subscapularis tendon (SC) split; C) the dashed line represents the final course of the LHB tendon through and anteriorly to the subscapularis tendon. The opposing 4 suture limbs will each be used to obtain an additional 2 knots to reinforce the fixation of the LHB to the glenoid rim. Reproduced from de Campos Azevedo and Ângelo<ref name=":28" />, with permission.]]

Labral Repair
With the arthroscope through the posterior portal, a standard Bankart repair is performed using 2-3 suture anchors. The anchors are placed on the glenoid rim at 3, 4, and 5 o’clock to enable the retention of the capsulo-ligamentous structures and to re-establish the labral damper effect (Video and Figure).
[[File:1562549775598-lg.jpg|center|thumb|600x600px|Intra-articular view through the posterior portal. Associated capsulolabral repair using 2 to 3 anchors recreates normal articular concavity (bumper effect). The anchors are placed on the glenoid rim between 3 and 6 o'clock, depending on the lesion. ∗ indicates the labrum. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

Postoperative Rehabilitation
Patients are instructed to wear a simple sling for 10 days encouraging rest and reducing the risk of post-operative hematoma formation. Rehabilitation with self-mobilization in elevation and external rotation is allowed from day 0. At 10 days, activities of daily living are allowed and self-mobilization in elevation and external rotation continued. Return to low-risk sports (eg, jogging, cycling, and swimming) is allowed at 6 weeks, and high-risk (throwing and collision) sports at 3 months only after satisfactory clinical and radiographic evaluations confirm satisfactory healing of the coracoid graft. Initially, no physiotherapy is recommended.

====Bony procedures====
In the setting of glenoid bone loss ≥20% of the glenoid diameter an arthroscopic Bankart repair has an unacceptably high rate of recurrence. Burkhart and DeBeer reported a 4% recurrence rate for arthroscopic Bankart repair when glenoid bone loss was <25%. However, with glenoid bone loss ≥25%, the recurrence rate was 67% with an arthroscopic approach. They subsequently recommended a bony procedure procedure in the population with substantial glenoid bone loss.<ref name=":4" />

Treatment is based on patient factors and associated pathology as previously discussed. In general, for patients under the age of 30, primary stabilization following a first traumatic anterior instability episode is offered. Such patients are counseled on the natural history or anterior instability and the potential for subsequent injury. For the majority of patients over the age of 30, nonoperative treatment is advised with standard sling immobilization for three weeks followed by progressive strengthening and return to activities. For such patients with persistent weakness or recurrent instability a magnetic resonance imaging (MRI) or MRI arthrogram is obtained to evaluate for an associated rotator cuff tear and stabilization is performed.

In consideration of the current literature, the following indications for osseous reconstruction procedures of the glenoid concavity can be recommended: - Substantial erosion-type defects (type IIIb), which constitute the instability-associated main pathology. - Chronic fragment-type defects (type II), where the glenoid area and concavity cannot be reconstructed by mobilization and refixation of the fragment. - In the rare patient with an acute, non-reconstructible, multifragmented glenoid fracture (type Ic). - In cases of revision surgery, e.g. after failed soft-tissue stabilization, a glenoid augmentation procedure is recommended also for smaller bony defects (type IIIa).

=====Open Latarjet=====
In 1954, Latarjet reported a coracoid transfer procedure in which the inferior aspect of the coracoid was secured to the anterior glenoid. The excellent stability of this procedure is obtained by a triple effect first proposed by Patte:<ref>Patte D, Debeyre J. Luxations récidivantes de l’épaule. Tech Chir Orthop Paris: Encycl Med Chir 1980:44–52.</ref>

1) the sling effect of the conjoint tendon when the arm is abducted and externally rotated, 2), the ‘‘bony effect’’ that increases or restore the glenoid anteroposterior diameter (Figure), and 3) the retensionning of inferior capsule to the stump of coracoacromial ligament, rending the coracoid extra-articular.
{| class="wikitable"
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![[File:1562549774884-lg.jpg|center|thumb|412x412px]]A
![[File:1562549775216-lg.jpg|center|thumb|300x300px]]B
!
|}
''Illustration of the three effects A) the sling effect, B) the bony effect and C) the retensioning of the capsule. Courtesy of Gilles Walch.'' 

When the arm is at an end-range position, the sling effect contributes 76-77% at different loads and the capsule the remaining 23-24% to the stabilization of the humeral head. At the mid-range position of the arm, the sling effect facilitates 51-62% and the bone block 38-49% of the stability. The sling effect, therefore, seems to constitute the number one stabilizing mechanism of the Latarjet procedure at both, the mid- and end-range of motion. The internal-external range of motion is thereby not significantly impaired.<ref>Yamamoto N, Muraki T, An KN, Sperling JW, Cofield RH, Itoi E, Walch G, Steinmann SP. The stabilizing mechanism of the Latarjet procedure: a cadaveric study. J Bone Joint Surg Am 2013;95:1390-7.</ref>

The Latarjet procedure is associated with a very low recurrence rate even in the setting of substantial glenoid bone loss and has become the gold standard of treatment in such settings. In addition, this non-anatomic method of anterior glenohumeral stabilization has progressively expanded and is actually the primary technique of choice for many European surgeons, as it prevents recurrent anterior instability in approximately 95 to 99% of cases. This procedure is also favored by some as a first choice in many contact athletes.<ref>Joshi MA, Young AA, Balestro JC, Walch G. The Latarjet-Patte procedure for recurrent anterior shoulder instability in contact athletes. Clinics in sports medicine 2013;32:731-9.</ref>

[[File:1562549775732-lg.jpg|center|thumb|600x600px|Illustration of a partial remodelling after an anteroposterior 2.5 cm tricortical iliac crest bone block. Antero-posterior (A) and Neer (B) view of a right shoulder after iliac crest bone block. Observe on 3 years computer tomography (CT) scan follow-up, the anteroposterior diameter of the glenoid remains supraphysiologic, explaining the efficiency of this open procedure.]]
Surgical technique (Video)
[[File:1563403564475-lg.mp4|center|thumb|300x300px|Video]]

Patient preparation
The patient is positioned in a classical, 40 degrees, beach chair position, preferably under a combination of general anesthesia and locoregional interscalene block to maximize the patient and the surgeon’s comfort. A single prophylactic antibiotic dose is highly recommended, as infectious complications are not uncommon in the proximity of the axilla. The upper limb is draped freely to allow manipulation of the shoulder and placed on an arm board. The operative site, including the sternoclavicular joint medially, is covered with iodine incise drape.

Incision
The incision is performed under the tip of the coracoid process extending 4 to 5 cm distally.
[[File:Gfaddw .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The tip of the coracoid process is palpated, and the incision is performed under the tip of the coracoid process extending 4 to 5 cm distally.]]
The dissection begins at the level of the Mohrenheim fossa, a triangular region just inferior to the clavicle, between the deltoid and pectoralis major muscles which do not contain neurovascular structures. The deltopectoral interval is then opened bluntly with two Richardson retractors, letting the cephalic vein medially.
[[File:Figure 2da a.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The dissection begins at the level of the Mohrenheim fossa, a triangular region just inferior to the clavicle, between the deltoid and pectoralis major muscles, which do not contain neurovascular structures. The deltopectoral interval is then opened bluntly with two Richardson retractors.]]
The Gelpi retractor is placed deep in the approach, while the cephalic vein is retracted laterally. The whole coracoid process with the insertion of pectoralis minor, coracoacromial ligament, and the conjoined tendon (CT) is exposed by placing the Hohmann retractor on its tip.
[[File:Figure 3d a aw.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The whole coracoid process with the insertion of pectoralis minor, coracoacromial, and the CT is exposed by placing the Hohmann retractor on its tip.]]
The pectoralis minor is released from the coracoid process with electrocautery while the arm is internally rotated and adducted.
[[File:Figure 4d ada .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Pectoralis minor (blue arrow) is released from the coracoid process (CP) while the arm is in adduction and internal rotation. CT – conjoined tendon.]]
The upper limb is abducted and fully externally rotated to improve the coracoacromial ligament visualization, which is then released approximately 1.5 cm laterally from its attachment.
[[File:Figure 5da ada .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The coracoacromial ligament (white arrow) is released 1.5 cm laterally from its attachment on the coracoid process (CP). The arm is abducted and externally rotated for 90° to improve its visualization. CT – conjoined tendon.]]
Coracoid graft harvest and preparation
A 90° angled saw blade is used to perform a coracoid process osteotomy at its base as far back as possible but still just anterior to the coracoclavicular ligament, starting superomedialy and proceeding inferolateraly.
[[File:Figure 64v q.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. A 90° angled saw blade is used for coracoid osteotomy, which is performed at the base of the coracoid process (CP) as far back as possible, however still in front of the coracoclavicular ligaments. CT – conjoined tendon.]]
When the coracoid process gets loose, a chisel is meticulously used to complete the osteotomy.
[[File:Figure 7dqwq qd.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The coracoid osteotomy is meticulously finished with a chisel. CP – coracoid process. ]]
The coracoid process is rotated for 180° while being held with a grasper. It is attentively released until the muscle belly is uncovered in order to be easily and safely manipulated. The coracoid process should not be placed outside the surgical field to avoid tension in musculocutaneous nerve neuropraxia. Its undersurface is flattened and slightly decorticated with a saw blade to create a healthy bleeding surface that will precisely conform to the later prepared anterior glenoid.
[[File:Figure 8q q .png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The undersurface of the coracoid process (CP) is flattened and slightly decorticated with a saw blade to create a healthy bleeding surface that will precisely conform to the later prepared anterior glenoid.]]
The two 4 mm holes for screw fixation are drilled equally distant from the base and the tip, 1 cm apart and 8-9 mm laterally from the insertion of the coracoacromial.
[[File:Figure 9das as.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. Two 4 mm holes for screw fixation are predrilled perpendicularly and centrally in the coracoid graft, 1 cm apart, and 8-9 mm laterally from the insertion of the coracoacromial. ]]
It is essential that the holes are drilled perpendicularly to the surface and centrally to the graft. There are two options for labral fixation, either by transosseous coracoid fixation or by fixation with anchors at the later medial coracoid-glenoid edge. If the surgeon chooses the transosseous coracoid fixation, two holes for later labral fixation are predrilled with a K-wire on the lateral coracoid process bony rim where the coracoacromial inserts, but so that they are placed bellow it and do not pass it. A non-resorbable suture is shuttled through each of them. The coracoid process is retracted medially with the pectoralis major muscle.

Glenoid exposure and preparation
The arm is placed in abduction and external rotation and the subscapularis split between the upper 2/3 and lower 1/3 of the subscapularis is performed by sharply introducing horizontally placed scissors towards the anterior glenoid neck.
[[File:Figure 10Ada s.png|none|thumb|Left upper extremity of a patient placed in a semi beach-chair position. The arm is placed in abduction and external rotation. ]]
[[File:Figure 10Bdaads a.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The subscapularis split between the upper 2/3 and lower 1/3 of the subscapularis (SSc) is performed by sharply introducing horizontally placed scissors through the subscapularis muscle towards the anterior glenoid neck. Then they are rotated for 90°.]]
Then, they are rotated for 90°. Their blades are extended to widen the split, while a Hohmann retractor is placed between the blades on the medial side of anterior glenoid neck. The division is additionally increased with a No. 15 blade.
[[File:Figure 11A.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position.The blades of the scissors are extended to widen the split, while a Hohmann retractor is placed between the blades on the medial side of the AGN. AGN – anterior glenoid neck.]]
[[File:Figure 11B.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The split is additionally increased with a No. 15 blade. SSc - Subscapularis, * - anterior capsule.]]
The superior and inferior parts of the subscapularis are held apart by two Gelpi retractors, one placed superficially and one deeper, while a Hohmann retractor is placed on the inferior aspect of the glenoid neck. The glenohumeral joint's exact location is exposed by reducing the anteriorly dislocated humeral head, and a vertical incision is performed.
[[File:Figure 12.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The exact location of the glenohumeral joint is exposed by reducing the anteriorly dislocated humeral head, and a vertical incision is performed in an inferior to a superior direction to protect the axillary nerve. * – anterior capsule.]]
A Trillat instrument is introduced in the joint to slightly posteriorly subluxate the humeral head to get a better view of the anterior labrum, and a wide glenoid retractor is exchanged with the Hohmann retractor on the medial side of the anterior glenoid to improve the visualization of the anterior glenoid. The labrum is horizontally released at the level of 3 o'clock position, and the release is extended inferiorly until the 5 o'clock position. Two non-resorbable sutures are passed through the superior and inferior half of the released labrum for later labral reconstruction.
[[File:Figure 13.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The labrum is horizontally released at the level of 3 o'clock position, and the release is extended inferiorly until the 5 o'clock position. A resorbable suture is passed through the superior half of the released labrum (white arrow). Afterward, another suture is passed through the inferior half of the released labrum for later labral reconstruction. ]]
A curved osteotome is used to slightly decorticate the anterior glenoid neck from 3 o'clock to 5 o'clock position to a healthy and bleeding flat bone bed.
[[File:Figure 14.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. A curved osteotome is used to lightly decorticate the AGN from 3 to 5 o'clock position to a healthy and bleeding flat bone bed. AGN – anterior glenoid neck.]]
The inferior hole aimed less than 10° away from the glenoid articular surface is predrilled with a 2.75 mm cannulated drill in the anterior glenoid neck, located 8-9 mm from the anterior glenoid.
[[File:Figure 15.png|none|thumb|Left shoulder of a patient placed in a semi beach-chair position. The inferior pilot hole aimed less than 10° away from the glenoid articular surface is drilled first with a K-wire and then with a 2.75 mm cannulated drill in the AGN, located 8 mm from the anterior glenoid. AGN – anterior glenoid neck. G – glenoid.]]
When drilling, it is important to stay as parallel as possible to the glenoid surface, as an angle exceeding ten degrees in the axial plane puts the suprascapular nerve at high risk of lesion at its course on the posterior glenoid rim (Figure).<ref name=":23">Lädermann A, Denard PJ, Burkhart SS. Injury of the suprascapular nerve during Latarjet procedure: an anatomic study. Arthroscopy 2012;28:316-21.</ref>[[File:1562551669419-lg.jpg|center|thumb|591x591px|A) The suprascapular nerve passes through the scapular notch beneath the transverse scapular ligament to enter the supraspinatus fossa and provide motor innervation to the supraspinatus muscle. The nerve then courses distally around the base of the scapular spine (spinoglenoid notch) to enter the infraspinatus fossa and provide motor innervation to the infraspinatus muscle. B) The infraspinatus branches of the suprascapular nerve are at risk during screw placement for Latarjet reconstruction. Reproduced from Lädermann et al., with permission.]]

Coracoid Positioning and Fixation

The coracoid process is retrieved and the two sutures that were previously placed through the labrum are inserted through the two predrilled graft holes if the transosseous labral fixation is underway. The coracoid process is placed at the prepared anterior glenoid neck surface. A K-wire is passed through the lower predrilled coracoid and glenoid hole to position the coracoid process on the anterior glenoid neck. The screw length is measured, and the screw is introduced for preliminary fixation (Fig 16 and Video 1). A thin Darrach retractor is used to place the superior part of the coracoid process flush with the glenoid face. Afterward, the superior hole is drilled with a 2.75 mm cannulated drill in the anterior glenoid neck, the length is measured, and the screw is introduced but not fully tightened (Fig 17 and Video 1). The anterior labrum is fixed on the coracoid process by tightening the knots of the sutures passing through the labrum. (Fig 18 and Video 1) Then the coracoid is fully fixed by completely tightening the two partially threaded 4.0 mm cancellous screws. This accomplishes an excellent compression between the coracoid process and the anterior glenoid neck due to the lag-by-design technique. If, however, the surgeon an anchor technique, around two anchors are placed at the medial coracoid-glenoid edge, and fixation of the labrum is performed.

The coracoid bone block is now removed from its protective location behind the autostatic retractor. Usually, a 28-30 mm inferior screw is used. The graft is positioned on the prepared anteroinferior glenoid quadrant in such a way that its lateral border is perfectly flush with the glenoid. The superior hole is then drilled and measured with precision to avoid any screw protrusion. Another 4.5 mm self-tapping standard cortical screw is chosen accordingly. The capsule and the labrum are reinserted between the glenoid and the graft according to Luc Favard’s technique in order to decrease the risk of dislocation arthropathy (Video). The sutures are tighten with the arm positioned in full external rotation elbow at the side, elevation, with the assistant pushing the humeral head posteriorly in order to reduce the shoulder. Both screws are finally tightened using a ‘‘2-finger’’ technique.

[[File:1562551689499-lg.mp4|center|thumb|600x600px|Video]]
[[File:1562551676712-lg.mp4|center|thumb|600x600px|Video]]
[[File:1562551685548-lg.mp4|center|thumb|600x600px|Video]]
[[File:1562551686995-lg.mp4|center|thumb|600x600px|Video]]

Capsulo-labral reconstruction
Finally, the anterior capsule is reconstructed by the imbrication of the coracoacromial ligament with a resorbable suture. While the operated arm is held in external rotation to avoid the postoperative rotational deficit, the humeral head is reduced posteriorly in the center of the glenoid during adduction, slight anterior forward flexion, and a posterior level push. (Figure and Video). Only then, an adequate capsular tension is expected. The wound is copiously irrigated.

Closure
The Trillat retractor is removed. The tendinous part of the subscapularis muscle lateral to the conjoint tendon is closed side to side with a non-resorbable suture, while making sure not to puncture the anterior ascending branch of the circumflex artery. The wound is closed and a drain is typically not used, unless excessive bleeding is noted.

=====Arthroscopic Latarjet=====
Surgical Technique
Operations are performed in the usual semi-beach chair position under general anesthesia with an interscalenic block or catheter. Arthroscopic Latarjet are carried out using a total of 5 portals (posterior, anterolateral, anterior, suicide, and superior to access the superior coracoid (Figure 34).
[[File:1562552295999-lg.jpg|center|thumb|600x600px|A) Anterior view, B) posterior view. The modified 5 portals are used for the arthroscopic Latarjet. AL anterolateral, A anterior, S superior, Su suicide portal, P posterior portal. Reproduced from Cunningham et al., with permission.]]
 Intra-articular approach is carried out through the standard “soft spot” posterior portal. The rotator interval is opened, and the internal structures (glenoid defects, humeral defects, HAGL, etc.) are further assessed with the probe. To provide a healthy bed for graft healing, the glenoid neck is abraded between 2 and 5 o’clock with a burr. A release of the subscapularis on 270 degrees and of the lateral side of conjoint tendon are then performed. The two subscapularis nerves and the axillary nerve are only located and not dissected as this may lead to neurological lesions. From a lateral viewing portal, a switching stick is inserted through the posterior approach, passed across the glenohumeral joint at the level of the glenoid defect and then advanced through subscapularis to establish the level of split. From the suicide portal, a modified cannulated subscapularis splitter is advanced on the switching stick to facilitate the split.

The probe is then introduced through the anterior portal to complete the split. The latter is thus done before coracoid osteotomy consequently protecting the plexus. At this point, with the scope in the anterior portal, the coracoid is prepared and then osteotomized with osteotome rather than a burr, in order to keep maximum graft length. The graft is extracted through the suicide portal and prepared outside, as inside debridement and trimming might be less accurate and puts the plexus at risk. The coracoid is then secured on the coracoid positioning cannula and positioned on the glenoid neck flush with the glenoid border. Two long K-wires are inserted through the coracoid positioning cannula, and the glenoid is drilled with a 3.2-mm drill bit. The length of the definitive screw is directly read from the depth gauge on the drill. The fixation is obtained with two 4.5-mm cannulated malleolar screws (Figure).

[[File:1562552292659-lg.jpg|center|thumb|600x600px|A) arthroscopic view and B) postoperative anteroposterior x-ray of a left Latarjet procedure. * indicates the graft fixed on the anterior glenoid. Reproduced from Lädermann et al., with permission.]]

=====Open Bristow=====
Independently of Latarjet, Helfet reported in 1958 a slightly different procedure named after his master, Bristow, where the coracoid with conjoined tendon attached was pressed against the anterior glenoid by suturing it to a slit in the subscapularis tendon instead of a screw.<ref name=":2" />

Despite the frequent synonymous labeling as “Bristow-Latarjet” coracoid transfer, the techniques remain distinct and non-equivalent reconstructive procedures. When differentiating between the coracoid transfer techniques, the stabilizing effect by the Bristow technique is inferior to that of the Latarjet procedure in cases of substantial glenoid bone loss due to the difference in coracoid graft size but also due to the direction of the conjoint tendon (Figure).<ref>Giles JW, Degen RM, Johnson JA, Athwal GS. The Bristow and Latarjet procedures: why these techniques should not be considered synonymous. J Bone Joint Surg Am 2014;96:1340-8.</ref>

[[File:1562552295240-lg.jpg|center|thumb|600x600px|Direction of the conjoint tendon in A) Latarjet and B) Bristow procedure (courtesy of George Athwal). Note that the conjoint tendon (blue arrow) during Latarjet has to go around the inferior subscapularis (dark blue). Contrarily, the conjoint tendon exits directly through the split during Bristow procedure. * indicates the origin of the conjoint tendon. Reproduced from Lädermann et al., with permission.]]

Surgical technique
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=====Arthroscopic Bristow=====
[[File:1562553238652-lg.mp4|center|thumb|600x600px|Video]]

Coracoid Preparation, Drilling, and Osteotomy
The arthroscope is initially maintained in the posterior viewing portal. By use of electrocautery through the anterolateral portal, the rotator interval is opened and the subscapularis is followed medially to the coracoid. During this time, the arm should be internally rotated to relax the subscapularis. The coracoid is dissected and the coracoacromial ligament is released. The anterior portal is established just medial to the coracoid, and the pectoralis minor is released. The undersurface of the coracoid is flattened with a motorized rasp through the anterolateral portal. The coracoid is drilled with a coracoid drill guide, a polydioxanone suture is passed through the bone tunnel, and the coracoid peg button is shuttled in place. Through the anterolateral portal, the coracoid undergoes osteotomy 1.5 to 2.0 cm from its tip.

Glenoid Preparation and Anchor Insertion
The labrum is released from the anterior glenoid neck, and a polydioxanone suture is placed through the labrum at the 5-o'clock position. The anterior glenoid neck is abraded to a flat surface using a motorized rasp and a suture anchor inserted at the 3-o'clock position to be used later for the Bankart repair.

Subscapularis Splitting and Axillary Nerve Protection
By use of switching sticks, the arthroscope is transferred to the northwest portal, the anterior glenoid neck preparation is confirmed, and a short half-pipe cannula is placed through the posterior portal. The glenoid drill guide is inserted over the cannula and placed flush with the glenoid face at the 5-o'clock position. A switching stick retracts the labrum and subscapularis through the west portal, and the glenoid tunnel is drilled from posterior with a 2.8-mm K-wire (the outer sleeve is left in place to facilitate the cortical-button transfer later). The posterior subscapularis spreader replaces the glenoid drill guide and is pushed through the subscapularis muscle along with the 5-o'clock position, at the inferior one-third junction of the subscapularis. An anterior bursectomy is performed through the south portal to identify the “3 sisters” (anterior humeral circumflex vasculature), which are followed to the “2 brothers” (musculocutaneous and axillary nerves). The nerves are carefully protected with a nerve retractor, and the tip of the posterior spreader is slowly opened within the subscapularis muscle. The tendon is split from medial to lateral while the capsule is being preserved, and the anterior subscapularis spreader is inserted through the east portal with its tip medial to the posterior spreader.

Coracoid Transfer and Fixation
By use of a suture retriever through the posterior sleeve, the cortical button and coracoid bone block are transferred through the subscapularis muscle and lie flush with the anterior glenoid neck. This fixation is made using 2 round, 6.5-mm, slightly convex titanium buttons, connecting with a loop of continuous suture, forming 4 parallel strands. The glenoid cortical button is slid over the 4 white suture strands, a sliding-locking Nice knot is tied, and the button is advanced onto the posterior glenoid neck. A specific suture tensioner is used to increase bone compression to 100 N.

Bankart Repair
Using the previously placed glenoid anchor, we complete the labral repair, placing the bone block in an extra-articular position. Additional anchors can be inserted depending on the clinical situation and patient anatomy. The tensioning device is removed posteriorly, and 3 surgeon's knots are tied to complete the coracoid fixation.

=====Eden-Hybinette and Other Free Bone Block Transfers=====
Aiming to reduce donor site morbidity associated with the harvesting of autologous bone blocks, autografts of the iliac crest and distal clavicle and allograft of femoral head and distal tibia have been evaluated (Figure).<ref>Mascarenhas R, Raleigh E, McRae S, Leiter J, Saltzman B, MacDonald PB. Iliac crest allograft glenoid reconstruction for recurrent anterior shoulder instability in athletes: Surgical technique and results. International journal of shoulder surgery 2014;8:127-32.</ref><ref name=":24">Provencher MT, Ghodadra N, LeClere L, Solomon DJ, Romeo AA. Anatomic osteochondral glenoid reconstruction for recurrent glenohumeral instability with glenoid deficiency using a distal tibia allograft. Arthroscopy 2009;25:446-52.</ref><ref>Weng PW, Shen HC, Lee HH, Wu SS, Lee CH. Open reconstruction of large bony glenoid erosion with allogeneic bone graft for recurrent anterior shoulder dislocation. Am J Sports Med 2009;37:1792-7.</ref><ref>Zhao J, Huangfu X, Yang X, Xie G, Xu C. Arthroscopic glenoid bone grafting with nonrigid fixation for anterior shoulder instability: 52 patients with 2- to 5-year follow-up. Am J Sports Med 2014;42:831-9.</ref>

Anatomically, iliac crest bone blocks offer the possibility of a nearly unrestricted graft size, but also the coracoid process was found to be a sufficient graft source to re-establish the anatomy for most glenoid defect cases.<ref>Bueno RS, Ikemoto RY, Nascimento LG, Almeida LH, Strose E, Murachovsky J. Correlation of coracoid thickness and glenoid width: an anatomic morphometric analysis. Am J Sports Med 2012;40:1664-7.</ref>

Provencher et al. described the use of an osteochondral tibia allograft with the advantages of a cartilaginous interface, improved graft availability and an excellent glenoid articular conformity.<ref name=":24" />

Radiologically, successful bony consolidation and a remodeling process of the allografts have been observed, as described for autologous glenoid reconstruction. However, a slightly higher recurrence rates of 0-22% were observed.

[[File:1562555338099-lg.jpg|center|thumb|600x600px|Illustration and arthroscopic intra-operative view of a left anatomic and intra-articular iliac crest bone grafting technique with graft fixation by two bio-compression screws. Reproduced from Lädermann et al., with permission.]]

Surgical Technique
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=====Trillat=====
[[File:Capture d’écran 2020-01-28 à 22.02.11.png|thumb|Native situation]]

[[File:Capture d’écran 2020-01-28 à 22.02.54.png|thumb|Illustration of a shoulder after Trillat procedure]]

[[File:Capture d’écran 2020-01-28 à 22.03.20.png|thumb|Effect of the Trillat procedure with the arm in abduction-external rotation]]

==Rehabilitation==

===Non-Operative Treatment of Acute First Traumatic Dislocations===
Although positioning the arm in external rotation has been recommended, it has now clearly been demonstrated that immobilization of the shoulder in internal rotation after primary, traumatic anterior shoulder dislocation is sufficient.<ref>Vavken P, Sadoghi P, Quidde J, Lucas R, Delaney R, Mueller AM, Rosso C, Valderrabano V. Immobilization in internal or external rotation does not change recurrence rates after traumatic anterior shoulder dislocation. J Shoulder Elbow Surg 2013.</ref><ref>Itoi E, Hatakeyama Y, Sato T, Kido T, Minagawa H, Yamamoto N, Wakabayashi I, Nozaka K. Immobilization in external rotation after shoulder dislocation reduces the risk of recurrence. A randomized controlled trial. J Bone Joint Surg Am 2007;89:2124-31.</ref><ref>Braun C, McRobert CJ. Conservative management following closed reduction of traumatic anterior dislocation of the shoulder. Cochrane Database Syst Rev. 2019 May 10;5:CD004962.</ref>

There is conflicting evidence regarding the length of immobilization required after dislocation but three weeks is typically recommended, followed by physical therapy for strengthening of the rotator cuff and scapular stabilizers. Range of motion of the elbow, wrist, and hand are permitted immediately. Then, closed-chain exercises facilitate rotator cuff function to enhance joint stability and stimulate muscular coactivation and proprioception.<ref>Jaggi A, Lambert S. Rehabilitation for shoulder instability. Br J Sports Med 2010;44:333-40.</ref>

For throwing athletes, a program is initiated and advanced, beginning at three months. A full return to sports is typically permitted at five to six months.

===Rehabilitation Protocol After Bankart and Remplissage Stabilization===
The shoulder is immobilized for four weeks using a sling. Passive and assisted-active exercises are then initiated for forward flexion and external rotation. After six weeks, patients begin strengthening exercises of the rotator cuff and scapular stabilizers. For patients with a remplissage strengthening is delayed until twelve weeks postoperative. Patients are permitted to practice noncontact sports as soon as they recover their range of motion. Full return to throwing or contact sports is usually allowed after six months according to each individual’s functional recovery.

===Rehabilitation Protocol After Dynamic Anterior Stabilization===
Patients are instructed to wear a simple sling for 10 days encouraging rest and reducing the risk of post-operative hematoma formation. Rehabilitation with self-mobilization in elevation and external rotation is allowed from day 0. At 10 days, activities of daily living are allowed and self-mobilization in elevation and external rotation continued. Return to low-risk sports (eg, jogging, cycling, and swimming) is allowed at 6 weeks, and high-risk (throwing and collision) sports at 3 months. Initially, no physiotherapy is recommended.<ref name=":13" />

===Rehabilitation Protocol After Latarjet Reconstruction===
The shoulder is immobilized for ten days using a sling. The patient is asked to stretch in flexion and external rotation at least five times per day. No physical therapy is prescribed. The patient is not allowed to carry with his operated arm or to flex the elbow against resistance during the first six weeks. Activities of daily living are encouraged as comfort permits. At six weeks, non-contact sports are allowed. Return to contact sports is usually possible after three months assuming confirmation of bony union of the coracoid graft.

==Results and Complications==

===Soft tissue procedures (Bankart, Remplissage)===
Arthroscopic Bankart stabilization with use of suture anchors offers the advantage of being minimally invasive, allows assessment of associated pathology, and allows the surgeon to restore anatomy while reattaching the labral lesion and retensionning the glenohumeral ligament. While the short-term outcome of Bankart has been excellent, mid-term reported results show higher rates of recurrent of instability. According to the meta-analysis by Hobby et al., recurrence (dislocation and subluxation) after arthroscopic Bankart repair with suture anchors varies between 0 to 29.6%, with a mean of 8.9%.<ref>Hobby J, Griffin D, Dunbar M, Boileau P. Is arthroscopic surgery for stabilisation of chronic shoulder instability as effective as open surgery? A systematic review and meta-analysis of 62 studies including 3044 arthroscopic operations. J Bone Joint Surg Br 2007;89:1188-96.</ref>

This rate of course varies with patient factors, particularly the amount of bony deficiency. Preoperatively, pitfalls are consequently to underestimate risk factors for recurrence for this surgery. In adolescent contact athletes undergoing arthroscopic labral repair, the overall recurrence rate is 51%. Rugby players who undergo primary arthroscopic shoulder stabilization aged <16 years have 2.2 times the risk of developing a further instability episode when compared to athletes aged ≥16 years at the time of index surgery, with a recurrence rate of 93%.<ref>Torrance E, Clarke CJ, Monga P, Funk L, Walton MJ. Recurrence After Arthroscopic Labral Repair for Traumatic Anterior Instability in Adolescent Rugby and Contact Athletes. Am J Sports Med 2018;46:2969-74.</ref>

Bankart repair combined with Malgaigne (Hill-Sachs) remplissage for large defects of the posterosuperior aspect of the humeral head may be an elegant approach in case of isolated humeral defect. Reported results are promising with a high rate of healing of the posterior aspect of the capsule and the infraspinatus tendon into the humeral defect, and a moderate loss of external rotation with the arm at the side. Moreover, most patients were able to return to sport including those involving overhead activities, around 70% at the same level.<ref name=":20" /><ref name=":21" />

The Malgaigne remplissage is believed to be a posterior capsulotenodesis that acts as a checkrein diminishing anterior humeral head translation and reducing the risk of postoperative redislocation. However, some authors have observed that according to the location of the impaction fracture, the procedure actually corresponds to a capsulomyodesis including the teres minor muscle, rather than a capsolutenodesis as classically described (Figure).
[[File:1562556949052-lg.jpg|center|thumb|600x600px|Posterior view of a right shoulder specimen after rotator cuff repair and Malgaigne (Hill-Sachs) remplissage (three lower knots). Note the proximity of the superior knot to the infraspinatus muscle (black arrow). The two inferior knots perforate the teres minor muscle (white arrow) realizing a capsulomyodesis.]]
 Concerns about remplissage may include the potential muscle lesion to the external rotators, increased cost, and increased difficulty and operative time. Yet, beyond a slight loss in postoperative external rotation, there is no documented additional complication to remplissage.

===Open Bone Block Procedures===
Open anatomical bone grafting procedures show very good clinical mid- to long-term results. With this procedure return to sports activities is possible for at least 83% of patients regardless of the size of glenoid defect. In a study of 107 patients, Lädermann et al. reported a mean postoperative Walch-Duplay score of 93, good or excellent results in 97% of cases, and 95% of patients very satisfied or satisfied with their outcome.<ref name=":14" />

However, complications exist both in the short- and long-term. A systematic review of 30 studies with a total of 1658 coracoid transfers, also including more recent surgeries with shorter follow-up periods, reported a low recurrence rate of 6.0%. The arthropathy rates is also reduced to 17-36% compared to the original procedures. A systematic review of 30 studies, comprising a total of 1658 open coracoid transfers, recorded graft non-union or postoperative graft migration (10.1%), hardware complications (6.5%), instability (6.0%), graft osteolysis (1.6%), infection (1.5%), nerve palsy (1.2%), intraoperative fractures (1.1%) and hematoma (0.7%) with a revision surgery conducted in 4.9% of the cases. Hardware problems were identified as the most frequent reason for revision surgery. In addition to failure of stabilization, hardware or graft malpositioning and respective screw breakage, loosening or migration is attended with a high risk for soft tissue as well as articular surface damage.<ref name=":22">Butt U, Charalambous CP. Arthroscopic coracoid transfer in the treatment of recurrent shoulder instability: a systematic review of early results. Arthroscopy 2013;29:774-9.</ref>

Regarding the postoperative muscle function, a significant strength deficit of the internal and external rotators was observed in comparison to the contralateral, unaffected shoulder.<ref>Caubere A, Lami D, Boileau P, Parratte S, Ollivier M, Argenson JN. Is the subscapularis normal after the open Latarjet procedure? An isokinetic and magnetic resonance imaging evaluation. J Shoulder Elbow Surg 2017;26:1775-81.</ref>

Risk of neurological impairment of the musculocutaneous nerve can be reduced by gently manipulating the coracoid process during preparation and avoiding an excessive medial dissection.<ref>Clavert P, Lutz JC, Wolfram-Gabel R, Kempf JF, Kahn JL. Relationships of the musculocutaneous nerve and the coracobrachialis during coracoid abutment procedure (Latarjet procedure). Surgical and radiologic anatomy : SRA 2009;31:49-53.</ref>

The suprascapular nerve is at risk posteriorly during screw insertion and can be protected by parallel placement of the screws within 10 degrees of the glenoid surface in the axial plane (Figures).<ref name=":23" />
[[File:1562556944819-lg.jpg|center|thumb|500x500px|The infraspinatus branches of the suprascapular nerve are at risk during screw placement for Latarjet reconstruction when a divergence of more than 10 degrees between the screws and the glenoid surface in the axial plane is noted. Photograph showing intimate proximity between screws placed for Latarjet procedure and suprascapular nerve. Reproduced from Lädermann et al., with permission.]]
[[File:1562556938948-lg.jpg|center|thumb|459x459px|Schema of screw and spinoglenoid notch orientation. (A) Axial view. The medial-to-lateral orientation was recorded by measuring the angle of the screws (α 1 angle) and of the spinoglenoid notch wire (β1 angle) relative to the glenoid plane. (B) Sagittal view. The superior-to-inferior orientation was determined by measuring the angle of the screws (α2 angle) and the spinoglenoid notch (β2 angle) perpendicular to the glenoid. (CG, coracoid graft; G, glenoid; HH, humeral head; SN, suprascapular nerve.). Reproduced from Lädermann et al., with permission.]]
[[File:1562556945397-lg.jpg|center|thumb|600x600px|Axial (A) and anteroposterior (B) plain radiographs of a left shoulder. The two screws diverge from the plane of the glenoid, pointing in direction of the spinoglenoid notch. A magnification (C) of the axial view demonstrates poor contact (white arrow) between the glenoid and the graft (delimited by red dotted line). Parallel screws would have led to better contact and a lower risk of suprascapular nerve injury]]
 

===Arthroscopic Bone Block Procedures===
Similarly, very good short-term results are achieved after arthroscopic glenoid rim reconstruction without events of postoperative redislocation and the advantage of subscapularis muscle preservation.<ref name=":25">Anderl W, Pauzenberger L, Laky B, Kriegleder B, Heuberer PR. Arthroscopic Implant-Free Bone Grafting for Shoulder Instability With Glenoid Bone Loss: Clinical and Radiological Outcome at a Minimum 2-Year Follow-up. Am J Sports Med 2016;44:1137-45.</ref><ref name=":26">Kraus N, Amphansap T, Gerhardt C, Scheibel M. Arthroscopic anatomic glenoid reconstruction using an autologous iliac crest bone grafting technique. J Shoulder Elbow Surg 2014;23:1700-8.</ref>

At present, however, merely short-term results of the arthroscopic techniques are published and only by the pioneers of these techniques. Following the arthroscopic coracoid transfer techniques, recurrence rates of 0-2% were observed after short- to mid-term follow-up investigations.<ref>Boileau P, Thélu CÉ, Mercier N, Ohl X, Houghton-Clemmey R, Carles M, Trojani C. Arthroscopic Bristow-Latarjet combined with bankart repair restores shoulder stability in patients with glenoid bone loss. Clin Orthop Relat Res 2014;472:2413-24.</ref><ref>Dumont GD, Fogerty S, Rosso C, Lafosse L. The arthroscopic latarjet procedure for anterior shoulder instability: 5-year minimum follow-up. Am J Sports Med 2014;42:2560-6.</ref><ref>Zhu YM, Jiang C, Song G, Lu Y, Li F. Arthroscopic Latarjet Procedure With Anterior Capsular Reconstruction: Clinical Outcome and Radiologic Evaluation With a Minimum 2-Year Follow-Up. Arthroscopy 2017.</ref>

The arthroscopic approach is, however, quite challenging and requires a lengthy learning curve. When directly comparing the arthroscopic and open techniques, a similar functional outcome and patient satisfaction were achieved, but screw placement inaccuracy, persistent apprehension, recurrence rate and complications were higher for the arthroscopic approach.<ref>Cunningham G, Benchouk S, Kherad O, Lädermann A. Comparison of arthroscopic and open Latarjet with a learning curve analysis. Knee Surg Sports Traumatol Arthrosc 2016;24:540-5.</ref>

A slightly reduced percentage of graft non-union or postoperative graft migration (8.1%), hardware problems (2.3%), instability (1.7%) and nerve injury (0.6%) was recorded, while the rate of osteolysis (4.1%) increased. Conversion to an open approach had to be conducted in 3.5% of the surgeries. However, a smaller number of cases conducted by fewer surgeons is available for evaluation of the arthroscopic approach. Larger case numbers by different surgeons and long-term results are therefore required to validate these first positive outcomes.<ref name=":22" />

===Remodeling of the Graft With Bone Block Procedure===
Regardless of the bone grafting technique employed, whether an implant-free or screw-based fixation method, a remodeling process according to Wolff’s law is observed with successful reconstruction of the anatomical pear-shaped glenoid configuration. Approximately 60% of the entire coracoid graft has been observed to undergo osteolysis. The superficial part of the proximal coracoid is predominantly affected, while the deep portion of the distal coracoid aspect showed the least osteolysis and best osseous union.<ref>Di Giacomo G, Costantini A, de Gasperis N, De Vita A, Lin BK, Francone M, Rojas Beccaglia MA, Mastantuono M. Coracoid graft osteolysis after the Latarjet procedure for anteroinferior shoulder instability: a computed tomography scan study of twenty-six patients. J Shoulder Elbow Surg 2011;20:989-95.</ref>

For the free bone grafting procedures, a partial extra-articular resorption of the initially oversized glenoid reconstruction may lead to restoration of the anatomic glenoid configuration over time in terms of a remodeling process (Figure).<ref>Moroder P, Hirzinger C, Lederer S, Matis N, Hitzl W, Tauber M, Resch H, Auffarth A. Restoration of anterior glenoid bone defects in posttraumatic recurrent anterior shoulder instability using the J-bone graft shows anatomic graft remodeling. Am J Sports Med 2012;40:1544-50.</ref><ref name=":26" />
[[File:1562557690817-lg.jpg|center|thumb|600x600px|Three-dimensional computer tomography reconstruction displaying an erosion-type defect (type III) before surgery (Figure 45 a), immediately after reconstruction using a free iliac crest autograft (Figure 45 b) and one year postoperatively (Figure 45 c) after completion of the remodeling with restoration of the anatomical glenoid configuration. Reproduced from Lädermann et al., with permission.]]
===Complication due to harvesting process of the iliac crest===
In comparison to the coracoid transfer procedure, free bone grafting techniques offer the advantage with potentially less severe complications. Complications of autologous bone grafting are predominantly associated with the harvesting process of the iliac crest bone block including pain, hypoesthesia and hematoma observed in 0-13% of the patients. Attempting to reduce donor site morbidity, current studies are evaluating the use of allogeneic bone material as an alternative to autografts. Further complications reported after open autologous iliac crest bone grafting comprise hardware failure (0-4%), shoulder hematoma (0-4%), subscapularis insufficiency (0-3%), graft fracture (0-2%), infection (0-2%) and adhesive capsulitis (0-2%).<ref>Auffarth A, Schauer J, Matis N, Kofler B, Hitzl W, Resch H. The J-bone graft for anatomical glenoid reconstruction in recurrent posttraumatic anterior shoulder dislocation. Am J Sports Med 2008;36:638-47.</ref><ref>Deml C, Kaiser P, van Leeuwen WF, Zitterl M, Euler SA. The J-Shaped Bone Graft for Anatomic Glenoid Reconstruction: A 10-Year Clinical Follow-up and Computed Tomography-Osteoabsorptiometry Study. Am J Sports Med 2016;44:2778-83.</ref><ref>Scheibel M, Nikulka C, Dick A, Schroeder RJ, Gerber Popp A, Haas NP. Autogenous bone grafting for chronic anteroinferior glenoid defects via a complete subscapularis tenotomy approach. Arch Orthop Trauma Surg 2008;128:1317-25.</ref><ref>Steffen V, Hertel R. Rim reconstruction with autogenous iliac crest for anterior glenoid deficiency: forty-three instability cases followed for 5-19 years. J Shoulder Elbow Surg 2013;22:550-9.</ref><ref>Warner JJ, Gill TJ, O'Hollerhan J D, Pathare N, Millett PJ. Anatomical glenoid reconstruction for recurrent anterior glenohumeral instability with glenoid deficiency using an autogenous tricortical iliac crest bone graft. Am J Sports Med 2006;34:205-12.</ref>

An investigation of 6449 patients reported an overall donor site morbidity rate of 19.4% after iliac crest bone harvesting including infections, chronic pain, fractures and nerve injuries at the harvesting site.<ref>Dimitriou R, Mataliotakis GI, Angoules AG, Kanakaris NK, Giannoudis PV. Complications following autologous bone graft harvesting from the iliac crest and using the RIA: a systematic review. Injury 2011;42 Suppl 2:S3-15.</ref>

The currently published studies evaluating arthroscopic autologous iliac crest bone grafting reported a singular case of donor site morbidity and one case of graft fracture in the 30 patients treated.<ref name=":25" /><ref name=":26" />

===Dislocation arthropathy===
Another complication is the development of dislocation arthropathy with a rate similar to other type of procedures (Figure).<ref>Hovelius LK, Sandstrom BC, Rosmark DL, Saebo M, Sundgren KH, Malmqvist BG. Long-term results with the Bankart and Bristow-Latarjet procedures: recurrent shoulder instability and arthropathy. J Shoulder Elbow Surg 2001;10:445-52.</ref>
[[File:1562557685456-lg.jpg|center|thumb|300x300px|Illustration of the three stage of dislocation arthropathy according to Samilson. Courtesy of Gilles Walch.]]
Even if the development of dislocation arthropathy is concerning (around 30%) (Figure), it is rather associated with the disease rather than to the surgery itself.
[[File:1562557685288-lg.jpg|center|thumb|600x600px|A) Anteroposterior plain radiographs of a left shoulder in a 32 year-old woman presenting with recurrent dislocations. Dislocation arthropathy Samilson B is obvious. B) CT scan of the same shoulder demonstrates significant glenoid and humeral bone loss.]]
While the precise cause is unknown, surgery in patients older than 40 years of age, a prolonged period between the initial dislocation and surgery and a lateral overhang of the transferred coracoid process in relation to the glenoid rim have been identified as risk factors. Contrarily, hyperlaxity was observed to be a protective factor against development of a dislocation arthropathy, which may be explained by the lower glenohumeral contact pressures.<ref name=":14" />

===Pull-out===
Anchor (Bankart repair) or screw (Latarjet, Bristow, free graft transfer) pull-out may happen (Figure).
[[File:1562557690266-lg.jpg|center|thumb|600x600px|A) Radiographs of a left shoulder ten days after a Latarjet reconstruction. The patient has been allowed to remove sling but not to do sport. B) The patient ignored the recommendation and was immediately jogging. He returned five hours after the last examination. Controlled radiographs revealed pullout of the graft due to contraction of the short head of the biceps on the coracoid graft.]]
 

==What would Codman have thought about this?==
The role of the supraspinatus in dislocation...

CHAPTER IX
THE ROLE OF THE SUPRASPINATUS IN DISLOCATIONS AND FRACTURES OF THE SHOULDER JOINT

THIS chapter does not aim to be an exhaustive treatise on fractures and dislocations of the shoulder, although a very large number of articles have been studied in order to compile it. During the summer of 1928, Dr. T. W. Stevenson reviewed the literature for me, with especial effort to find to what extent the bursa and the short rotators had been referred to. At about the same time, I took advantage of the service of the Library Bureau of the American College of Surgeons, with the request that they find for me all the references they could concerning rupture of the supraspinatus tendon. After a careful search they were unable to find any articles whatever which were devoted to the subject, although occasionally they found references to rupture or avulsion of the tendons in cases of dislocation on which operations had been done.
So far as I know there is no record in the literature of what I call the "Pivotal- Paradox," described on page 43. I, myself, did not understand this paradox when I started to write the book, and only gradually puzzled out its meaning and significance. Certainly none of the authors, who have written on dislocations and fractures in this region, seem aware of the facts that in complete elevation of the arm almost no rotation can occur and that the extent of rotation diminishes as the arm is elevated. The lack of this knowledge of normal functions seems to me to render most of the previous explanations of the mechanism of dislocations and fractures in this region nearly worthless, for several important deductions can be made by the use of these facts. I have consequently eliminated much that I had previously written about the opinions of authorities.
In complete elevation there is only one possible geometric relation of the two units, i.e., the head of the humerus and its tuberosities, with the scapula and its processes. No matter in what degree of rotation you start to raise your arm and no matter in what plane you raise it, the capacity for rotation will be less and less as the arm ascends until, in complete elevation, tuberosities and processes will be locked in a fixed position. In this fixed position the articular head of the humerus will be shown by X-ray in the antero-posterior view, to face nearly outward, and in the lateral view to face somewhat forward, i.e., it actually faces obliquely outward and forward, exactly reversed from its anatomic position. The axis of the condyles of the lower end of the humerus becomes antero-posterior, with the internal condyle pointing forward. The humerus has rotated inward 90° and has become inverted. You may say that the angle between the shaft and the axis of the neck gained 45° by inversion and then 45° by external rotation, or you may say, if you please, it first gained 45° by internal rotation and then another 45° by inversion. Do not proceed with this chapter until you are sure that you have understood this paragraph, even if it is necessary for you to take a humerus in your hand.
The reader must bear in mind that this pivotal position may be assumed by extension of the scapula on the humerus as well as by extension of the humerus on the scapula. For instance, the arm may be in this position when a boxer delivers a telling punch, "putting his body into it." However, the true pivotal position implies that the clavicle is elevated and carried backward to its extreme limit when the arm is elevated to its extreme degree. In other words, the scapula and humerus may move into their share of the pivotal position without the clavicle rising (subordinate pivotal positions), but the arm, to attain complete elevation and the true pivotal position, must be raised to the side of the head.
The scapulo-humeral joint will lock in different positions according to the degree of rotation of the humerus, in a very queer way. (See Figs. 25 and 26.) There can be very little scapulo-humeral abduction with the humerus in full internal rotation; i.e., when the forearm is behind the back, even if clavicle is raised. Starting with your clavicle held down, try elevation of your arm in either internal or external rotation, and then compare the extent of motion when you start with it raised. You will see why authors have differed so much in their estimates of the degree of motion possible in the scapulohumeral joint. To get the maximum you must perform elevation in internal rotation in the sagittal plane or external rotation in the coronal plane; you cannot interchange. These motions cannot be estimated by putting the scapula of a cadaver in a vise, because in life they vary with the relative positions of humerus, scapula and clavicle.
It is as if the secondary humeral joint, limited by the acromion and coracoid, were built with two long sloping sides meeting at an angle above the head, so that when the arm is raised in any plane it eventually comes to rest in the trough formed at the angle of the coronal and sagittal planes and cannot rotate any more. Nature's command is: "Make any combination of elevation and rotation within this enclosure which you wish, but if you exceed these normal limits, you may dislocate or fracture your humerus."

A logical conclusion from these facts is that in whatever way a forward or lateral fall occurs, no strain will come on the scapulohumeral structures until they assume this locked position in complete elevation, provided rotation of the humerus is unhindered as the arm is being elevated. In other words, when the arm is being elevated in mid-rotation in the sagittal plane and arrives at a little above a horizontal position, if inward rotation be prevented, some structure must give, provided the fall continues in this plane. This is exactly reversed in the case of falls in the coronal plane, for when outward rotation is prevented, some break in bone or soft parts must occur. The latter example is the usual one in dislocation and fracture of the head of the humerus.
Let us imagine the same forces applied in another way, i.e., by leverage on the arm when the body is in a fixed position, for mechanically it is the same problem whether the falling patient exerts force on the outstretched arm, or the fixed patient has the same force applied to the arm. Let us imagine the arm thrust into a pipe and force applied to that pipe as in the following diagrams, by lifting its free end up from the plane of the paper- (Fig. 53.)
In making an effort to remember the combinations of rotation and elevation of the arm which may or may not be made, a simple formula is this: evolution has fitted the human animal to fall directly forward on his face with his arm and forearm in almost any position in relation to his body, but, once he has fallen, his arm and forearm cannot be brought much behind the plane of his body in the position in which he lies on his face on the ground, without in some way raising his body.
We may learn a good deal about the shoulder joint from watching the maneuvers of a wrestler endeavoring to turn his opponent from a face-downward position. These maneuvers are essentially the same as those represented in the diagrams above, that is, they depend on getting the flexed forearm in such a position that a little more leverage would break or dislocate the humerus, unless the prone wrestler does permit his body to be raised. Of all the possible positions in which his forearm and arm can be pulled backward, that in which the arm lies at the side will show the greatest backward mobility, i.e., "dorsal flexion."
In lateral falls, when the abducted arm is held behind the plane of the body, the same dislocating or breaking strains that the wrestler endeavors to secure may be produced, the force being supplied by gravity. Moreover, falls will be more violent and sudden, and perhaps catch the muscles when relaxed, instead of having the opposing muscles offer resistance by the voluntary tension which the prone wrestler can assume.

FIGURE 53. LEVERAGES CAUSING ANTERIOR AND POSTERIOR DISLOCATIONS
In interpreting this plate the reader must imagine the arm thrust into a pipe, and he must suppose that the patient's body remains in ironlike rigidity while the outer end of the pipe is raised directly upward from the plane of the paper. Provided the body remained rigid and the tube were raised in this manner, a dislocation of the head of the humerus or fracture must occur. Typical backward or subacromial dislocation would occur in Figures 2, 6 and 7, while subcoracoid dislocation would occur in the other positions.

As in simple frontal falls, so in simple dorsal falls no dislocation of the shoulder will occur, if the arms are free, for we may lie on our backs with our arms in any position anterior to the coronal plane of the body. Even when the dorsal fall occurs with the forearm behind the back or behind the head, dislocation is unlikely.
Thus we reach the conclusion that only headlong, lateral, or semi-lateral, sudden falls can produce the forced elevation combined with prevention of rotation which is necessary to cause anterior luxation of the shoulder joint.
It is possible to conjecture, from a more detailed study of the questions just considered, which forms of dislocation, or varied locations of the lines of fracture, will occur in the shoulder if the lines of force are known. For instance, it is safe to say that only the results of forces applied as in Cuts 2, 6 and 7, in Fig. 53, may result in subacromial dislocation, while all of the others produce subglenoid dislocation.
To express the writer's belief in another way: anterior dislocations of the humeral head occur after the arm has reached the fixed "pivotal position," or more often by prevention of rotation when the arm is at least above the level of the shoulder and the extent of possible rotation therefore greatly diminished; subacromial displacements occur when the arm is below the level of the shoulder and is rotated internally.
This belief is founded not only on the facts already mentioned, but on two others. The first is the remarkable ability of the arm to rotate quickly. Any one who has done any wrestling will remember how elusive were his opponent's arms, unless his elbows were bent, and how easily they slipped out of his grasp as he endeavored to obtain a "shoulder lock." The second is the utter unreliability of the histories given by patients of falls "on the shoulder." The reader is again referred to p. 10. Patients with these injuries almost always say that they struck their shoulders and do not realize that they fell with their arms elevated, i.e., raised to fend off the ground. The inertia of the body is so great as compared to that of the arm, that even in a sudden fall the arm may be thrust forward or outward before the body reaches the ground. A man must already be hugging something, as a football, under his arm in order to fall on his shoulder.
The fact that the arm rotates readily in a safe direction as it is instinctively raised (i.e., raised in relation to the scapula, although pointing downward) during a fall, means that subconsciously the arm will usually reach the relatively safe pivotal position. Meantime the palm meets the ground and the force becomes disseminated to the various ligaments, muscles and bones of hand, wrist, elbow, shoulder and back, each in turn breaking the fall until the final bony lock in the pivotal position brings the stress to a limit. Even then the pec-toralis, the teres major and latissimus, and finally the clavicle, may still further disseminate the stresses. But notice that in this elevated position the lines of force of these muscles converge toward the glenoid, so that they are not, in this position, functioning as rotators as they do when the arm is at the side. The higher the axis of the humerus the more their power is exerted toward the face of the glenoid in their effort to avert the leverage of the shaft from gaining a fulcrum on the acromial edge. However, while they are in use in fending off the ground, the pectoralis and latissimus are acting also as strong internal rotators. This is the period of danger (Fig. 55), for the pivotal position, once reached, means safety, unless the downward factor in the fall is great. When the arm is in the pivotal position, the broad tendon of the latissimus actually covers the unprotected axillary portion of the capsule and tends to prevent the head from dislocating, although the pull of this muscle is in the main downward. In this position the long head of the triceps, the teres major and the latissimus actually form a support for the lower half of the capsule.

FIGURE 54. ACTION OF PECTORALIS MAJOR IN DISLOCATION
This diagram pertains to the discussion of whether the pectoralis major and latissimus dorsi should be regarded as furnishing a fulcrum in case of fracture of the upper end of the humerus. The contention is made that the pull of these muscles not only does not act as a fulcrum, but to some extent relieves the strain on the surgical neck, by pulling the tuberosities away from the true fulcrum which is the acromion. If these muscles acted as a fulcrum, the power would be applied on the glenoid and would immediately rotate the whole scapula, so that the acromion would become a fulcrum. The writer holds that in such accidents there can be no disruptive force in the region of the head of the humerus unless the acromion does act as a fulcrum.
The diagram further illustrates the fact that the power of the supraspinatus is applied in such a manner as to restrain dislocation, but that in forced elevation of the arm the upper edge of the glenoid acts as a wedge driven in between two points of application of strain. This idea is amplified in Plate IX.

Many authors have contended that besides the obvious bony fulcrums which occur, there may be others momentarily maintained by contracted muscles, which may lead to fracture or dislocation. Perhaps this is true, but I have been able to work out few such mechanical positions. For instance, the lever formed by the humerus when the arm is in the anatomic position, the pectoralis and latis-simus contracted, and outward force applied at the elbow, may be considered either to have its fulcrum on the glenoid or to apply power there, with the pectoralis, etc., as a fulcrum. The latter might be the proper way to consider the problem if fracture occurred in the long arm of the lever, distal to these muscular attachments. It seems more logical to me to regard the applications of muscle pulls as forces acting on the obvious bony fulcrums. However, there can be no doubt that when these muscles are contracted they would tend to prevent outward rotation of the humerus.

FIGURE 55. TRAJECTORY OF CENTER OF GRAVITY
The center of gravity of a person in falling necessarily always has a trajectory formed by the momentum with which he falls forward, combined with that with which he falls downward, and that which is exerted in relation to the median plane. The writer contends that in most instances, dislocations and fractures in the region of the upper end of the humerus take place when the trajectory meets the ground at or posterior to the point of impaction of the elbow, and also internal to this point. If the trajectory came far anterior to the point of the elbow, the arm would be folded to the side, or if it came far posterior to the point of the elbow, the arm would extend harmlessly beside the head. If it came near the median plane or to the opposite side of it, the arm would slip outward into the hammock position. It therefore seems highly probable that most of these fractures happen when the arm is internally rotated by the pectoralis, etc., and the fall is of such a sudden and violent character that the humerus does not have time to rotate.
If the vertical factor in the trajectory were great so that the patient was falling nearly straight, head downward, fracture or dislocation in the pivotal position would occur. The writer believes that in every case there is acromio-humeral contact, and therefore always a subordinate pivotal position (see Fig. 25).

I am not in sympathy with the view of those authors who hold that the contracted pectoralis and latissimus act as a fulcrum to promote dislocation or fracture of the head of the humerus. I think the reverse is true, so far as their adductor action is concerned, for I am convinced that this action merely tends to prevent dislocation, since the force is applied to the long arm of the lever distal to the true fulcrum which is the acromion.
Lack of space prevents elaboration of the following additional reasons which support this conviction.

The directions of the majority of the fibers of the pectoralis
major suggest that -their contraction would bring the head toward
the glenoid from the very start of elevation, i.e., they would directly
oppose dislocation.
In other words, the lower fibers of the pectoralis are inserted higher on the humerus than the upper fibers; thus all fibers of the muscle tend to pull in a line away from the acromion as a fulcrum while the arm is being raised.
The combined power of the adductors would not be enough to break the humerus, if both ends of the latter were fixed. Therefore, their power would not be enough to act as a fulcrum for a fracture in the short arm of the lever, although it might be sufficient in the long arm.
Even if the power on the long arm of the lever'acting through the muscles as a fulcrum, became applied to the glenoid and to the supraspinatus and other opposing muscles, the result would merely tip the scapula so as to apply the acromion as a fulcrum.
Until the acromion became a fulcrum no disruptive force could take place between the scapula and humerus.
If the humerus touched the acromion at all and the pectoralis, etc., applied their power exactly opposite this point, the leverage exerted on the glenoid would not be changed in any way; nor would it be changed much if the point of application were moved a little away from the neutral point on the long arm of the lever. However, that slight change would diminish rather than enhance the tendency to dislocation.
The X-ray shows close apposition of acromion and humerus, when the arms are akimbo, in the salute position and in complete elevation.
The acromion is always the fulcrum, although in the above positions different parts of the acromial edge come in contact with different parts of the circumference of the humeral head. (Fig. 25.)
Although I believe that the pull of the pectoralis and latissimus actually help to prevent dislocation by their action as adductors, I am strongly of the opinion that as internal rotators they actually help to promote dislocation. The reasons may be briefly stated a& follows: On account of the position of insertions of their tendons, to be adductors, they first have to be internal rotators. As adductors they do their best to fend off the ground until the last possible moment when the acromion has begun to be a fulcrum. Meanwhile, as internal rotators, they are drawing the arm into a subordinate pivotal position and thus prevent external rotation, which is the only method of escape for the arm if it must rise in the coronal plane. Thus we can conceive of their having power enough to keep the humerus internally rotated until it is too late for it to turn, although we cannot conceive of their being able to act as direct adductors strongly enough to withstand the falling weight of the body. If, in any case, they instinctively relax in time for rotation to occur, the arm will rise to the side of the head and no harm will have been done. Occasionally, however, the relaxation is too late, or vice versa, the violence is too sudden, and the arm will be caught in internal rotation in or near the coronal plane. It will then be too late for the adductors to relax in order to let rotation occur and thus permit the arm to ascend by the head.
The nearer the bent arm, in internal rotation, lies to the sagittal plane the safer it will be; the nearer the externally rotated arm lies to the coronal plane the safer it will be and vice versa. As a matter of fact, in healthy youth it is astounding how rapidly this instinctive rotation will occur. The football player may be hurled headlong by impact with other players in such a way that his body may be twisting laterally as it falls, yet his outstretched arms fend off the ground just long enough to prevent his breaking his neck, and in spite of the sudden, twisting violence, rotation at the last moment usually avoids dislocation of the shoulder.
Yet occasionally the resultant of all the forces of the fall makes the trajectory of the center of gravity strike posterior to the point of the elbow and to its inner side, while the humerus is internally rotated, and anterior dislocation will occur.
If the reader wishes to go into this in more detail he may force his mind to project a combination of Figures 26 and 55. It is difficult enough to visualize the normal workings of the shoulder joint, but it is still more difficult to foretell the results, on this beautifully adjusted apparatus, of a fall downstairs. Yet I think these general principles usually apply.
On the supposition that our conclusion that the humerus must obtain a fulcrum on the acromion in order to exert a disruptive force to produce dislocation is correct, let us consider what occurs in the inner unit of the shoulder, Figure 8, Chapter I.
The fulcrum on the edge of the acromion obtains its skeletal support, whatever the position of the arm, directly through the clavicle to the sternum. As has been said, not only is upward dislocation of the acromio-clavicular joint prevented by the fact that the clavicular portion of it is superior, but by the strong coraco-clavicular ligaments. Thus the clavicle in any position furnishes a strong radius through which the pressure on the fulcrum is firmly sustained. Moreover, the S shape of the clavicle has been shown to not only withstand great pressure in a line between its two ends, but to have great elasticity when the pressure is released.
I wish to accent again three characteristics of the scapulohumeral joint.

The capsule is necessarily loose.
The upper half is muscular and strong; the lower half is fibrous and weak.
Since the humerus can rotate many degrees (probably 100+) without moving the scapula, any one of the short rotators may receive the chief burden of the strain according to the degree of rotation when the acromion becomes the fulcrum. The following remarks will be based on the supposition that the supraspinatus is uppermost, as in Fig. 9, but would apply equally well when any of the other rotators were directly opposed to the force moving the elbow.
As the elbow rises upward not only is the supraspinatus contracted but the upper edge of the glenoid becomes a wedge in the reentrant angle, between the articular cartilage and inner surface of the supraspinatus. This accounts for the frequency with which fracture of the tuberosity accompanies dislocation. In most cases not only the facet on the tuberosity for the supraspinatus will be carried away, but also a concavo-convex piece of bone comprised of the greater tuberosity and part of the lesser, and extending down to the point where the humerus touches the acromion, and including even the bicipital groove as a whole with its tendon intact. (See Plate IX.)
If the force goes no further we shall have a false dislocation, for the lower part of the capsule being loose and there being no support above, the head will glide over the lower edge of the glenoid and fall into the lower part of the capsule, stretching it downward. Correspondingly, the dislocation will be at once reduced as the arm falls to the side, for it will not be pushed through a hole in the capsule and thus have an impediment to easy reduction.

PLATE IX. FRATURES OF THE TUBEROSITY AND FALSE DISLOCATION
The mechanism of fracture of the greater tuberosity and its relation to false and true dislocations.
a. The pivotal position.
6. When leverage is exerted against the acromion as a fulcrum, the biceps tendon guides the upper edge of the glenoid to enter the sulcus as a wedge, thus tending to chip off the tuberosities. This wedge is not a point but the curved edge of the fibrocartilage backed by the rim of the glenoid.
c. The inferior extremity of the fragment is therefore at the point of impaction of the acromion. The biceps tendon, tuberosity and subacromial bursa remain in their normal relations. A false dislocation of the head may then occur without rupturing the lower part of the capsule because tension is relieved by the rent in the upper portion. The lower part of the capsule, which is normally capacious, will be merely carried beneath the glenoid, as the arm descends.
d. The same lesion with the muscles depicted. A portion of the subscapularis still remains attached to the lesser tuberosity, but most of the greater tuberosity, and part of the lesser, remain in Continuity with the fragment.
e-f. Schematic drawings to illustrate the difference between a false and a true dislocation. False dislocation must necessarily be accompanied by rupture of the upper portion of the capsule, together with fracture of the greater tuberosity or rupture of the tendons. There is no structure except possibly the biceps tendon likely to interfere with its replacement, but in a case of true dislocation where the lower part of the capsule alone gives way, the sides of the capsular rent would tend to become tight around the neck of the bone, when efforts are made at reduction. In the worst cases where the two forms are combined an operation is required.
It seems as if some cases must occur in which the biceps tendon would be freed because the line of fracture might extend down the groove and the tendon would thus be separated from the greater tuberosity, and lie between the fragments. I think it usually remains in contact with both fragments if it is not evulsed from the glenoid by the same violence, in which case it retracts into the groove.

This I believe to be the mechanism in most cases of fracture of the tuberosity, whether the accompanying dislocation is recognized or not. On the other hand, both the bone and the supraspinatus attachment may hold in whole or in part, and be stretched down over the glenoid, until the lower portion of the capsule is tensed and torn and permits the head to slip through it and remain subglenoid, with the torn capsule tense on each side of the surgical neck. This will be the ordinary uncomplicated true dislocation.
Violent falls may produce a combination, first wedging off the tuberosity and then driving the head through the lower capsule.
Other variations may be:
1. Instead of the whole tuberosity being wedged off, the supraspinatus may tear away only the facet of insertion.
2. Evulsion of the supraspinatus at the blue line may occur.
3. Rupture of the supraspinatus may take place just above the palisades.
4. Very rarely a lip may be pried away from the lower edge of the glenoid instead of having the capsular attachment give way. I suspect that this is more apt to occur when the forearm is very much rotated internally and the arm is akimbo.
5. Rupture of the long head of the biceps may accompany true or false dislocation, or any of the above variations.
In general, in types 1, 2 and 3, we may expect additional tearing either toward the side of the infraspinatus or toward the side of the subscapularis, according to the degree of rotation of the humerus on the scapula at the time of the fall.
These are the very obvious lesions which may occur, but I believe the most common complication to be the " rim rents " described in Chapter V, which occur not only with dislocation, but in many cases where these structures are just able to resist dislocation, although the synovia becomes separated from the articular margin and a few inner fibers of the tendon are torn.
Another factor which may resist dislocation remains to be considered—the atmospheric pressure which holds the bursal surfaces together. In the typical false dislocation with fracture of the tuberosity, I do not believe that the relations of roof and floor of the bursa are destroyed. Until air is let into the bursa the surfaces tend to remain in contact. Many a time I have demonstrated this on the operating table. The same is true of the joint. To test in actual pounds the degree of pull required to separate these surfaces remains for some future observer. I feel confident that many pounds of direct pull would be required in the living to separate either bursa or joint to any great extent unless fluid is present. Even when the bursa is opened one cannot pull the joint surfaces apart without undue force unless the supraspinatus is torn, when they fall apart as soon as the air enters. The surface area of the bursa and that of the joint must be very nearly the same, roughly two inches in diameter, each. In X-ray tests one must remember that the cartilages do not show and that the presence of fluid permits separation.
A thorough understanding of what has been said in the preceding pages of this chapter is so important that a summary seems necessary at this point.
1. In spite of the usual histories which patients give of striking on the shoulder, the cause of dislocations or fractures is rarely, if ever, direct, but is usually a backward or downward (i.e., backward and downward in relation to the body as the patient falls) force, acting in the pivotal position, or in a subordinated pivotal position, through the humerus as a lever, with the acromion as a fulcrum, and the weight represented below by the lower portion of the capsule supported by the triceps, latissimus and teres major, and above by the resistance of the supra- and infra-spinatus, the long head of the biceps, and the atmospheric pressure in joint and bursa.
2. During a fall, unless the elbow is maintained in flexion, rotation of the humerus readily occurs; but since no lateral motion at the elbow is possible, fixation of a flexed forearm in a given position may greatly alter the direction of force applied at the shoulder, so that dislocation might occur at a point in elevation short of the pivotal position, but usually above the horizontal. For example, a lateral fall in the coronal plane when the humerus is held in internal or mid-rotation, in such a manner that external rotation is prevented (as by contraction of the pectoralis major), or a somewhat headlong fall in the sagittal plane while internal rotation of the forearm is prevented, might result in fracture or dislocation.
3. It is very unlikely that forward dislocation ever takes place unless the fall is at least somewhat headlong, i.e., one in which the elbow strikes a point anterior to the trajectory of the center of gravity.
4. In most instances subglenoid dislocation must be at first momentarily erect. The descent of the arm into the sling position, in which we usually find it, will be in internal rotation with the head of the humerus still displaced below and anterior to the glenoid, with the subscapularis relaxed and the other short rotators stretched over the glenoid. The long head of the triceps will be between the teres major below and the minor above, and the articular surface of the humerus will face backward on the origin of the long head of the triceps.
5. It seems probable that backward or subacromial dislocation never takes place from forces operating on the arm when it is being elevated, but must occur below the horizontal when the humerus is only abducted to a sufficient degree to permit the flexed forearm to be forced backward behind the body in internal rotation. Vice versa, anterior dislocation usually occurs only when the arm is above the horizontal, although theoretically, if the elbow were at the side and the humerus were rotated outward by the flexed forearm, anterior dislocation might occur from a sudden lateral fall which forced the forearm in external rotation behind the body. This would be a very unnatural way to fall, however.
If we accept the above explanation of the mechanics of dislocation, we may proceed to speculate on the reasons why fracture instead of dislocation often occurs from exactly similar falls. Age seems to be the determining factor, but this factor may be subdivided into two secondary ones, i.e., the relative tensile strength of the structures at different ages, and the relative mobility of the bones in youth and in age.
Assuming stress in the pivotal position:
In early youth the humerus ascends high under the acromion, and as the epiphyseal line is relatively the weakest point, epiphyseal separation will probably occur.
As a rule, in youth and manhood after union of the epiphyses, tendon and muscle and bone are strong relatively to the lower portion of the capsule, so that dislocation will take place. If any fracture occurs it will usually be at the greater tuberosity. Occasionally it will occur at the surgical neck.
In old age the trabecular structure about the base of the tuberosities will be weak; therefore, comminuted fracture will readily occur. If the bone holds, dislocation will usually be accompanied by rupture of the supraspinatus, for the muscles and tendons will be weak and cannot disseminate the force.
The second factor, i.e., the extent to which the head of the humerus may pass beneath the acromion, is also important in determining the seats of fracture in youth and in age.
In childhood the tip of the acromion is soft and cartilaginous, and thus the stress on the bony portion of -the acromion would be met at about the epiphyseal line, although the head of the bone passes far beneath the cartilaginous acromion.

FIGURE 56. EPIPHYSES OF A CHILD'S SHOULDER BONES
Outline drawing from X-ray of child with both arms elevated. By use of a dotted line the figure on the left is made to appear as an anterior view while that on the right appears as a posterior. At this age the tip of the acromion is pure cartilage and does not appear in the film. Notice that the head of the humerus passes beneath the acromion just far enough so that the bony portion of the acromion would gain a point of impact very close to the epiphyseal line. The cartilaginous tip would bend and the breaking force would occur at the epiphyseal junction.
This figure also shows that the line of epiphyseal union of the coracoid is at its base. I have never recognized a separation of this epiphysis. My work has been such that I have seen comparatively few injured children, but I think that it is quite possible that this lesion does occur, and may be detected by characteristic symptoms. It is certainly one of those conditions which we should expect on purely mechanical grounds.

In youth the tuberosity also passes far beneath the acromial edge, and this will bring the fulcrum to bear low down on the surgical neck, just above the attachment of the powerful pectoralis major. Usually dislocation will occur with or without fracture of the tuberosity. Occasionally the surgical neck will give way at the fulcrum.
In the stiff, aged joint, the tuberosity will barely pass beneath the acromion, and impact of the latter will come at the point just below the tuberosities, where the cancellated bone is weak, so that comminuted, intracapsular fracture will usually occur.
It is likely that there may be some changes in the exact lines of these comminuted fractures according to the degree of rotation which the humerus attains at the time of fracture. That is, the acromion will be applied at quite different points on the tuberosity in external and in internal rotation.
Other factors may be important also. For instance, the rapidity of the application of force; the degrees of contraction of the various muscles; congenital or habitual variations in the structure or position of the bones and of other tissues; the weight of the body; many minor circumstances or unusual combinations of any of the above factors. However, the point I wish to make is that the pivotal position is to the human arm in its varied activities as his earth is to the fox. The elusive arm must be driven to its pivotal position to be caught, or tricked by preventing rotation on the way. With continued effort we may always dig the fox out, and with continued backward force we may always break or dislocate the head of the humerus,, although the human arm is as clever in evasive rotation as the fox is in doubling.
There are many other points on which a consideration of the "Pivotal Paradox" is enlightening and which are worthy of study, for a thorough understanding of the mechanics of dislocations must be of help in their diagnosis and treatment. However, it will require many studies by many people before practical experience will cease to be our guide. Whether the deductions I have made above prove to be right or wrong, the following practical facts support them and are confirmed by all writers and by each surgeon in his own experience.
The causes of anterior dislocations are usually headlong or lateral falls with the arms thrust forward to fend off the ground.
The same kinds of falls may also produce the following lesions of the upper end of the humerus:

(1) Separation of the humeral epiphysis.
(2) Fracture of the surgical neck.
(3) Fracture of the tuberosities.
(4) Fracture of the anatomic neck.
(5) Comminuted fractures in which the typical form consists of four fragments; i.e., the two tuberosities, the anatomic head, and the shaft. (See Fig. 60.)

Any of these forms may be complicated by concomitant dislocation of the articular head, whether or not it remains attached to the shaft.
The fractures will be discussed in the next chapter and dislocations in the remainder of this one. However, the two subjects are inseparable and one should realize that both fracture and dislocation occur in many cases which are classed as either lesion. I am inclined to think that a combination is the rule, especially in cases of fracture of the tuberosities, and that many supposedly simple fractures are accompanied by false dislocation of the head which immediately becomes spontaneously reduced. Previous dislocation is evident in cases of complete separation at the anatomic neck in which the head remains displaced, but unless the latter is completely separated, it will be dragged back by the tuberosities, which are rarely dislocated because they are sucked back by the bursa and almost invariably remain attached to the short rotators. In other words, these tendons may rupture without the occurrence of any bone lesion, but if one does occur, the tendons remain attached to the fragment. Only small crumbs of the tuberosities ever become really free even in the most comminuted fractures.
The number of shoulder injuries compared to the total number of industrial accidents reported in Massachusetts during eight years is shown in tabular form. This table is not perfectly accurate, so far as the figures on dislocations and fractures are concerned, because it was not arranged for the particular purpose for which I am using it. For instance, all fractures of the clavicle and all fractures of the humerus are included because no distinctions had been made as to the part of the bone injured. It is probable, therefore, that the number of dislocations is fairly exact, but that the number of fractures of the upper end of the humerus is considerably less than the figure given, and probably in every year less than the number of dislocations. Probably many of the cases which were classed as fractures also had dislocations and vice versa. Although there is a striking tendency toward uniformity of the numbers through the different years, the proportion of dislocations to fractures varies somewhat for the above reasons. It is fairly safe to say, however, that about one-fifth of all shoulder injuries occurring in industry are fractures or dislocations of the upper end of the humerus. It is likely that if we could get similar statistics from the population not engaged in industry, fractures would be more common than dislocations, because fractures in this region usually occur in elderly people. Unfortunately, there can as yet be no statistics to determine how often the supraspinatus is injured as a complication of these so-called major (?) injuries, nor what proportion it forms of the other injuries which are unclassified. I believe that it costs our community more than all the other lesions together, not only because it is so common as the major lesion in fractures and dislocations, but because there are many unrecognized minor cases.

The shoulder is the most frequently dislocated joint in the body. This fact is quite properly generally ascribed to its relative instability. Dislocation of the humerus occurred 108 times in 528 cases of dislocation reported by Eliason, and it has been stated by various authors that forty to sixty per cent of all dislocations are of the shoulder. Many shoulders are probably dislocated and immediately reduced by the patient or his companions as they lift him after a fall, without knowledge that dislocation has occurred.
Dislocations of the head of the humerus have been classified in several ways, although for practical purposes only two classes are of importance, i.e., the forward or subcoracoid, and the backward or subacromial forms. As the latter are rare, "dislocation of the shoulder" usually refers to the former.

The first four varieties in the table are essentially the same. If the tear of the capsule and stretching of the muscle bellies away from their beds-are extensive, the dislocated head can be moved easily from a subglenoid to a subcoracoid or to even a subclavicular position. As has been shown, the erect subglenoid position probably occurs in every case momentarily, as the patient falls with the upraised arm, although depression and internal rotation at once ensue from muscular contraction, causing the arm to assume the position at the side in which we usually find it. Very rarely does the erect phase last long enough to be classified!
Subspinous is merely an extreme degree of subacromial dislocation. It occurs when the infraspinatus has been badly torn from its bed so that a large space under the spine of the scapula accommodates the displaced head. Upward dislocation implies an accompanying fracture of the acromion and is nothing more than a curiosity in extremely severe accidents. I have never seen it.

DIAGNOSIS OF ANTERIOR DISLOCATION

In simple subcoracoid dislocation of the humerus, the well-known signs are as follows:

History of a trauma to the shoulder in which something was felt to give way and a severe, acute, nauseating pain was experienced.
Active and passive movements are limited and painful.
The forearm is held flexed and internally rotated.
The elbow is away from the side and cannot be completely adducted, thus causing the long axis of the shaft to incline upward and inward.
Patient stands inclined to the affected side so as to bring the axis of the humerus to a vertical position.
Measuring from the acromion to external epicondyle, the upper arm appears lengthened.
The anterior axillary fold (on the affected side) is lower.
The shoulder is flattened.
The acromial process is prominent.
The head is palpable under the coracoid.
A soft crepitus can be elicited while manipulating the shoulder.
In other words, the facts to be learned from the history, inspection, palpation, motions and mensuration, plus the aid of the X-ray, will usually make the diagnosis beyond doubt. In fact, the diagnosis is generally so obvious that we must be on our guard not to overlook concomitant injuries and complications. While examining the patient one should take especial note of the circulation of the arm, and of the sensitivity of the skin over the arm and shoulder. The power of the deltoid, rhomboids, clavicular part of the pectoralis major, supraspinatus and infraspinatus, etc., should be carefully noted with a view to detecting paralysis. When the case is typical, the eleven signs are exceedingly plain, but this does not mean that when they are absent there is no dislocation.

It is very important for the reader to understand that all of the above signs, except the first and the last, fail when the articular head has been replaced on the tuberosity, which has itself been displaced into the glenoid. At this point the reader should refer to the history of Case 71, page 288, and study the accompanying diagrams. Our mistakes in diagnosis will occur in these cases where the head of the humerus can hardly be said to be out of place, but is certainly not in place, for the short rotators with the evulsed facets lie between it and the glenoid. (Fig. 58 and Case 115, p. 389.)
The second symptom was absent in Case 115 because the nerves were paralyzed or so retracted as not to be influenced when the arm was moved. The replacement of the head to nearly its normal position had completely removed the third to tenth symptoms and even the eleventh symptom, in this particular case, was absent or very difficult to detect.
Of course, such cases of pseudo-reduction are not common, but they occur now and then, so that we must never fail to bear in mind that cases of dislocation which are not quite satisfactory may become extremely unsatisfactory, if the supraspinatus or other short rotators are torn, or have dragged the facets toward the glenoid.
Treatment. The main therapeutic principles are: reduction, fixation and gradual return to function.
Reduction in most cases can be obtained by the Kocher or by the Astley Cooper traction methods. These procedures are too well known to describe in this text. The Kocher method is most generally used because much less force needs to be exerted, and hence less trauma should occur during the reduction. However, as Kocher himself said in his original article, it does not always work and it is sometimes necessary to use the Astley Cooper method.
Much has been said concerning the optimum position in which to maintain reduction. This would seem to suggest that the ideal position had not been found. Some modern authors, notably Stevens, are of the opinion that the arm should be put up in abduction and external rotation.
A simple way of obtaining abduction and external rotation is to put the patient in recumbency, and fasten the hand to the head of the bed. A suitable ambulatory splint can be used, or both methods in conjunction. A splint maintaining abduction and external rotation is cumbersome, and attracts a great deal of attention. The ordinary airplane splint abducts, but internally rotates the arm. Abduction and external rotation put the patient in the position of a traffic officer stopping a line of cars. The writer does not advocate this abduction treatment, and prefers not to fix the arm at all.
The advocates for maintaining the arm in the sling position after reduction, contend that the torn capsule heals better because it is relaxed. This seems reasonable, unless the rent is longitudinal, in which case its edges would be approximated better in abduction. It has never been determined positively whether rents in the capsule are usually longitudinal or transverse. Some writers claim that the capsule is torn from the forward edge of the glenoid, and my opinion is that this is the usual condition, for this only means the tearing of the pillars which form the opening of the bursa subscapularis. More observations of cases where death has occurred from the same accident as that which dislocated the limb are much needed. If we knew in general how the capsule is usually torn, the answer to the question of whether to maintain adduction or abduction would be much more plain.
The writer believes that at present there is too great a tendency to confine the arm after reduction. It would seem more logical to let the patient use his arm a little—even to urge him to do so, in order that debris and blood clot may work out of the joint capsule into the areolar tissue, where they would be readily absorbed. If the capsule were emptied of the blood clot, it would seem that it would be more likely to have its edges fuse together again without leaving any distortion or undue irregularity. On the other hand, I believe that motion should not be forced for fear of tearing edges which are beginning to unite. For those who think this policy too radical, it would be safer to treat most cases in the sling position than in the abducted one, unless the surgeon were very well versed in the study of the shoulder joint. I think stooping exercises should be begun at once and continued daily in any case. We should use fixation only for comfort, and this means very little, for one may be sure that if there is severe pain after reduction some complication exists.

Prognosis. It would seem an easy thing to make a prognosis in cases of dislocation, but as will be seen shortly, complications are frequent, often unrecognized, and greatly modify the period of disability. A fair prognosis in uncomplicated cases would seem to be a return to normal function in from four to eight weeks. However, complications are, I am sure, more frequent than is generally realized.

FIGURE 57
X-rays of the case alluded to in the text in which the articular head had become displaced beneath the deltoid and was excised through a sabre-cut incision. This patient recovered with a useful arm, and was able to play excellent golf for many years afterwards. Undoubtedly fracture and dislocation occurred at the same time, and the head was left behind in the erect phase of dislocation, when the arm came to the side. The articular surface remained in nearly the position which it occupies in normal elevation. It seems possible that if this fact is recognized in similar cases, reduction might be accomplished by again placing the shaft in elevation, opposing the raw surface of the articular head to that of the tuberosity, and holding them together while the arm is brought to the side in the coronal plane.
Figure a, before operation.
Figure b, a few months after operation. The acromion, which had been sawed across for the sabre-cut incision, has been wired about two steel pegs.
Figure c, taken nineteen years later, when the patient was eighty. There had been no trouble from the wire or pegs in the intervening years. At this time motion in the joint still persisted, but "was very limited in degree. However, it was sufficient to permit a slight amount of abduction and rotation, which permitted him to use his arm freely for ordinary purposes. Although this operation was successful in restoring a fair degree of usefulness, if I were obliged to operate again for such a condition I should not remove the articular head, and would endeavor to reconstruct a normal joint, perhaps employing Dr. Nicola's suggestion of anchoring the articular head by means of the biceps tendon. Before incising, I should hyperelevate the arm in internal rotation in order to appose the fractured surfaces.

Gubler, in a study of insurance records of 252 workmen's compensation cases, states that recovery occurred in 94.1% of the cases after an average of thirty-eight days of treatment. Another investigator, Kuttner, reports a far different experience. He was able to trace fifty-four uncomplicated cases from among 168 treated during the previous five years. Only seven (13%) had regained full use of the limb without loss of strength or motion. In fourteen (26%) the range of motion was complete, but the strength was reduced one-half or more. The remaining thirty-two (61%) had some loss of motion, which in twenty-six amounted to inability to raise the elbow laterally above the level of the shoulder. He states that all of these cases were uncomplicated (which we doubt), and had been treated in the hospital by immobilization for a week, followed by massage and mechanotherapy for two to three months. Goebel reports similar unfavorable results on twenty-four patients. Twelve had full function, but subjective complaints. Twelve had limitation of motion. Lexer reports forty cases; ten with complete restoration, fifteen with some limitation, fifteen with pain and loss of strength.
These reports are self-explanatory, and coincide with my observation of results obtained in general hospitals. The conclusion is that most of these patients received other injuries at the time of the accident or during treatment. I believe that uncomplicated cases tend to recover in about four weeks, unless interfered with by injudicious treatment, such as prolonged fixation.

Complications. Injuries to other structures about the joint are common and students should be most thoroughly warned of this fact. It is not so much that these complicating lesions are difficult to detect at the time of the first treatment, but that they are not suspected. It is a fact that these complicating lesions do often exist and do maintain disability and pain long after the joint itself has returned to normal, yet there is no organized effort of our profession to correct this condition. Industrial cases may be labelled malingerers, psychoneurotics, hysterics, or cases of traumatic neuroses, because of this prolonged disability with few detected physical signs. The five common complications of dislocation are the following:

Fracture of tuberosities.
Avulsion of the facets, or rupture of the tendons.
Fracture of the glenoid rim of the scapula.
Injury to the brachial plexus.
Rupture of the axillary artery or of other vessels.
Fracture of the greater tuberosity has hitherto been thought to be by far the most common injury accompanying dislocation. Graessner found the greater tuberosity broken twenty-four times in forty-eight dislocations, but in many of them the fragment was only a small scale of bone, indicating an avulsion of the tendon. Delbet found it in twenty-two out of one hundred and ten cases. Dollinger in five out of thirty-nine. Goebel twenty in forty-three cases. Schlaepfer found it eight times in one hundred and twenty cases, or 7.4%. Gubler reports it in eighteen out of two hundred and fifty-two cases, or 7.1%. Gubler also reports ten cases of other bone injury, and ten of nerve injury in his series. In my opinion, many of the cases where only a small facet is torn away should be classed with supraspinatus injuries rather than with fractures of the tuberosity, because they result in free communication between the joint and the bursa.
The bone injuries are generally easy to diagnose if looked for. The typical signs of fracture, especially ecchymosis down the arm along the biceps, are usually present and the X-ray is of great assistance. The real difficulty is too great a tendency to treat the major abnormality, the dislocation, and to overlook very important, but less obvious, injuries. Sometimes failure to recognize complications is due to careless X-ray examination, but more often to the inexperience of the doctor who first treats the patient. Rupture or avulsion of tendons attached to the tuberosities should be suspected when the films are negative.
The injuries to nerves and arteries will be considered in Chapter XI.

REFERENCES OF AUTHORITIES TO THE ROLE OF THE SUPEASPINATUS
IN DISLOCATION

Little is to be found in the literature to confirm my beliefs or to explain why the short rotators come to be so frequently injured. Only a few writers have realized the frequency of such injuries, and I do not think that any" of them have appreciated the significance of the fact that the bursa and joint are thus put into communication.
Stimson says that the supraspinatus is sometimes, probably often, torn from its attachment to the humerus, and the same is true in less degree of the infraspinatus, and occasionally even of the teres minor. He states also that avulsion of the tuberosities may take the place of laceration of the tendons. Preston says that injury to the capsule is not infrequently accompanied by injury to the tendons which overlie and reinforce it, and when the violence producing the luxation is great, there may be a destruction of tendon continuity.
Stevens gives an excellent description of shoulder dislocation with especial reference to the short rotators. According to him, an anterior dislocation is an impossibility without putting a strain upon the tendons of the supraspinatus, infraspinatus and teres minor. With the humeral head in subcoracoid dislocation, the distance from origin to insertion of the supraspinatus is greatly increased, and in addition the tendon is angled over the rim of the empty glenoid. Similarly the posterior rotators are pulled over the posterior rim of the glenoid, and are almost always injured. "We may," he says, "assume that in every case of dislocation of the humerus, and especially in anterior dislocation, there is an injury to the tendon of the supraspinatus, and that often it is ruptured."
Very few other authors even allude to this tendon.
The following cases as well as the above quotations from the literature support the assertion that the facet of the supraspinatus may be torn off in dislocation.

CASE REPORTS

No. 12. Mr. A. F. K. Age 45. Massachusetts General Hospital No. 174082 W. S., Jan. 23, 1911.
A subcoracoid dislocation of four months' duration. Open reduction of dislocation. Supraspinatus was found retracted with facet of insertion. Heavy silk sutures to unite it with tuberosity. Feb. 24; 1912: An excellent functional result, but scar is ugly.

No. 22. Mr. J. H. D. Age 69. Massachusetts General Hospital No. 182238, April 22, 1912.
Five weeks ago fell, injuring right shoulder. Reduced by M.D. Went back to work. One week ago dislocated it again when drunk. I made an unsuccessful attempt at reduction in the Accident Room, and then carried the patient under ether to the operating room, and through the usual incision for the bursa I opened directly into the joint. A defect corresponding to the facet of the supraspinatus was found, the supraspinatus being retracted under the acromion. There was no piece of loose bone corresponding to the defect, although the whole joint was carefully searched. It must therefore be assumed that the loose piece had been absorbed. The dislocation was reduced, supraspinatus reinforced with silk and the wound closed. Two years later he wrote me: " I can do quite a lot with it, only when I reach overhead it gives way and causes some pain."

No. 71. Mrs. E. C. Age 68. On June 10, 1921, fell downstairs, broke left wrist and dislocated left shoulder. Ether was given by the local doctor, and he supposed he had reduced the dislocation. She consulted me on August 9, 1921, and after taking X-rays, I reported to the physician who had sent her to me that I thought that the shoulder joint had been reduced. The accompanying X-ray seemed to me to show that the bone was in place. I know now that this appearance is deceptive. In such cases as this, the tuberosity has been retracted into the glenoid and the head of the humerus rides on it. Therefore, there is not very much change of contour in the position of the shoulder, because the total amount of bony substance between the tip of the shoulder and the glenoid is the same, although the position of the tuberosity is reversed and lies in the glenoid. The following is an account of the operation which I did on April 5, 1922, nearly a year after the injury.
Sabre-cut incision. Prominent anterior mass proved to be head of humerus minus the tuberosity. The tuberosity had been retracted by the posterior short rotators and lay partly in the glenoid cavity and partly overlapping its posterior margin. The biceps tendon was displaced so as to lie between the head of the bone and the glenoid. It was excised. The retracted tuberosity was also excised. The synovial and tendinous capsule of the joint was completely gone, except at the anterior edge, namely, the portion formed by the subscapularis tendon. A good, practical result was obtained, i.e., a movable, painless, weak shoulder, lacking power in abduction, but more useful than a painful joint.

It is my belief that in most of these cases of dislocation where the X-ray shows a portion of the tuberosity to be absent, careful pictures will show its presence in the glenoid or just below the glenoid. The capsule forms a pouch below the glenoid and this pouch catches the smaller fragments if they have become loose. The cases are deceptive because a reasonable amount of motion may be found within the first few weeks and the position of the head is so nearly normal that it is not realized that the head does not actually touch the glenoid.

FIGURE 58. THE USUAL CAUSE OF FAILURE TO REDUCE A DISLOCATION
Mrs. E. C.— X-ray (a) before the local doctor attempted reduction. The fragments of tuberosities may be seen external to the lower edge of the glenoid. The head of the bone is displaced far beneath the coracoid process; the form of dislocation might be classified as subclavicular. It is probable that in this case there was both a true and a false dislocation. After reduction (b) the tuberosities seem to be absent, though indications of their fragments are shown near the lower edge of the glenoid. I have operated upon a number of other similar cases (e.g., Nos. 5 and 92), so that I have formed the opinion that when the X-ray after reduction shows the absence of the tuberosity, radical operation is indicated, even if the X-ray does not demonstrate the fragments. It is my belief that this form of displacement accounts for the great majority of instances, which the authors quoted in this chapter speak of, as unsatisfactory results.

Case 115, to be reported later, was also an illustration of this condition. Two of the most alert industrial surgeons whom I know were fooled by the superficial appearance in this case, and I, myself, did not recognize it on my first visit. Even Stevens, whom I regard as having been particularly well informed about conditions in the shoulder, shows in his illustration, "Fig. 4," what I believe to be a case of this kind. He speaks of the fragments as having disappeared behind the head of the humerus. In cases showing X-rays similar to this, I would recommend exploration through the routine incision of the bursa. If it is obvious that the fragment has retracted into the glenoid, I recommend enlarging the incision to a "sabre-cut," and making an attempt to suture the structures in their normal position.
Before leaving the subject of anterior dislocation, I should like to italicize the following paragraph:
I believe that after the reduction of every case of dislocation of the humerus, the patient should be allowed to recover from the anaesthetic and be urged to move his arm freely, before any bandaging is applied. All motions may be safely performed except abduction in external rotation, and even this may be done with due care and using extension at the same time. If we find paralysis of any of the muscles, areas of skin anaesthesia, undue axillary swelling, gritting sensation in the joint, or a tendency for the joint to slip out of place, the patient should be at once hospitalized and consultation obtained.

(The author here advises the reader to study the next chapter on fractures and then to return to the remainder of this chapter, which discusses some of the more unusual forms of dislocation.)

FIGURE 58
(c) Explanation. Erect dislocation, as usual, preceded the subcoracoid position. The fragments of tuberosity, still held together by the musculo-tendinous cuff, slipped down on the glenoid, while the head was dislocated below and the arm fell to the side. Reduction was attempted and seemed successful, but the head of the humerus merely became superimposed on the fragments so that it seemed that the dislocation had been reduced, and the contour of the swollen shoulder became nearly normal. The biceps tendon was carried with the fragments on to the glenoid. In Case 115 there was scarcely any fracture except at the facets of insertion; the whole musculo-tendinous cuff had dropped back on the glenoid. In most cases the retracted tuberosities are held on the glenoid by the short rotators, as this man holds his hat on the further side of the tree. The biceps tendon may (Case 115) or may not (Case 71) be torn in such cases.

Subacromial dislocation is rare. I can only recall one case in private practice. This was in a young man who was a personal friend. It is twenty years since I reduced his dislocation, immediately after the accident, and the shoulder has given him no trouble since. Probably most of these subacromial or subspinous cases run as smooth a course, but occasionally, as in the following instance, one proves to need operation.

No. 33. Mrs. C. B. Age 38. Massachusetts General Hospital No. 184814 W. S., Sept. 7, 1912.
A case of recurrent subspinous dislocation which had remained unreduced for three months. "Sabre-cut" incision, the joint carefully inspected and cleaned of old granulations and detritus. None of the short rotators had been ruptured. Dislocation reduced and acromion wired in place. April 17, 1914, she writes, "I am thankful to say my shoulder is all right. It does not seem to be as strong as the other one, otherwise it is fine."

This is the type of case in which the "sabre-cut" incision is particularly applicable, in fact, it is almost indispensable if one wishes to obtain a satisfactory cleaning out of the glenoid. In all these operations for old dislocations I have found the glenoid to be filled with old granulations and detritus. Satisfactory reduction could not have been done without thorough cleaning of the cartilaginous surface.
The second case is an illustration of what I believe to be the usual mechanism of subacromial dislocation. She gave the history that seven years previously the first dislocation had occurred, during a convulsion while she was in labor. Six months later she dislocated it again while " closing a door behind her." The last time it was dislocated by "turning quickly around in her chair."
In the case first mentioned, the young man sustained his injury while being thrown from a sitting posture on a toboggan which had struck a rock. He was thrown in the air—presumably still holding the railing of the toboggan. This might produce the same effect of internally rotating the arm, as in closing a door behind the back.

OLD DISLOCATIONS

Speed considers a dislocation as old and irreducible after three months. The obstacles to reduction are the same as for a simple dislocation plus such secondary changes as:

Cicatricial contraction from healing scars in the capsule and adhesions to surrounding structures.
Displaced bone fragments, osteophytic outgrowths, callus, etc.
Muscles shortened and atrophied.
Synovial space obliterated
One can readily understand the difficulty of reducing an old dislocation if he will study the specimens to be seen in anatomic museums. The remarkable attempts of nature to derive some utility from a dislocated shoulder joint make reduction most difficult. At the point where the humeral head lies against the scapula, a tremendous bony proliferation takes place, and inevitably ankylosis or pseudoarthrosis results. The glenoid becomes atrophied and filled with fibrous tissue.
The varying combinations of pain, deformity, and limitation of motion which these patients present have incited surgeons to attempt relief. Every surgeon of large experience htts probably made a few attempts to help such patients, but before long finds that they form a class of cases in which he can be generous to his younger colleagues, who also in time learn by experience. As a matter of fact, these are serious cases and demand expert care, although this is not attainable at present, for there are no such experts, so far as I am aware.
There are five general lines of treatment from which we may choose.

(1) To leave nature to do the best she can.
(2) To attempt bloodless reduction under an anaesthetic.
(3) To attempt open reduction.
(4) To resect the head of the humerus.
(5) To perform arthrodesis.

Andrews concluded that an attempt at reduction by manipulation is extremely dangerous. In his words, "The bloodless method has a gory trail of accidents." He finds fifty cases of hemorrhage, mostly fatal, up to 1905. An interesting one was reported by J. C. Warren, in whose case a large aneurysmal tumor arose after attempts at reduction. The subclavian was tied and recovery ensued.
If a new joint can be produced at all, it should be possible to do it by the "sabre-cut" incision, for all the structures of the joint are readily visible and accessible. I have encountered two chief difficulties. One has been the fusion of the retracted tendons and tuberosities with the glenoid alluded to in Case No. 71. If many months have passed, there is little left of the cartilaginous surface of the glenoid when the debris has been removed from it. However, this is not the chief obstacle—the real one being the absence of any synovial membrane to prevent adhesions of the cartilaginous head in its new bed. If the cartilaginous head is not too badly destroyed and seems likely to function, I should advise completing the attempt to make a new joint, but if the head has been eroded and there is no synovia left to surround it, adhesions will surely take place, and almost no motion will be secured. An irritable, painful joint with only a few degrees of mobility will result. In such a case, I think that one should deliberately perform excision or arthrodesis. The method of arthroplasty recently suggested by Dr. Laurence Jones of Kansas City offers a most hopeful solution of this problem.

RECURRENT OR HABITUAL DISLOCATION OF THE SHOULDER JOINT

Recurrent dislocation is not a common lesion, but it has interested a large number of investigators. Speed says that this lesion is peculiar to athletes and epileptics. This is more than a witticism, but not entirely true. Almost every author has put forward a somewhat different theory as to the cause of recurrent dislocation, and Speed has gathered together the most important ones. They are:

Defect in the head of the humerus acquired at first dislocation, or perhaps congenital.
Defect in the glenoid—acquired fracture of the edge, or congenital shallowness.
Rupture of the insertions of the external rotators of the head of the humerus.
Avulsion of tuberosities with or without rupture of the rotators.
Detachment of capsule from anterior lip of glenoid.
Enlarged joint from relaxed capsule following tears which have been given insufficient time for strong cicatrization, or repeated stretching without tears.
A seventh theory may be added. Since the shoulder joint is not a real joint, and is dependent for its integrity on a very complicated neuro-muscular cooperation, the essential feature in some of these interesting cases may be a failure of this cooperation. Reference to Plate I will show how easily incoordinated pulls from two opposing muscles might result in instability of the head on its fulcrum. Rupture or stretching of the tendon of the latissimus might thus make the joint unstable in the pivotal position. Certainly from an X-ray point of view the bony structures in most of these cases are normal.
The slight support furnished the joint by the bony structures has been considered, and it would seem more reasonable to suspect a defect in the major supporting structures, the muscles and their tendons, than in the bony structure. The importance of the supra-spinatus and of the other short rotators has been emphasized, and it has been noted with what frequency their continuity is broken in ordinary dislocations. More authors have found occasion to mention lesions of the short rotators and tuberosities in recurrent dislocations than in simple dislocations, because the majority of the former cases are treated surgically, so that more opportunity is afforded for observation.
Considerable evidence is given in favor of each of the causes listed by Speed and probably any one of them could well account for a recurrent dislocation. Hildebrand found two cases of fracture of the anterior rim of the glenoid with laceration of the capsule, in which he obtained good results by reshaping and deepening the glenoid. In an X-ray study of twenty-one cases in Hildebrand's clinic in Berlin, Pilz found definite bony defects in the humeral head in fifteen, de Fourmestraux found a deformity of the head in four out of eighty cases. Henderson reported no bone injury found by X-ray in many cases. We have seen several cases in which no abnormality could be found with careful X-ray examination.
According to Stevens recurrent dislocations at the shoulder joint are always due to more or less tearing of the supraspinatus, infraspinatus, teres minor, and more rarely of the subscapularis, and their subsequent repair by scar tissue in a position of stretch. No definite cases to prove this were given.
Thomas concludes that habitual dislocation is due to a traumatic, cicatricial, anterior, hernial pouch of the capsule. The most constant lesion which he found was a tear in the anterior and lower part of the capsule. In an experimental luxation of the shoulder on a cadaver, he placed the head in complete subcoracoid dislocation, and found the supraspinatus, infraspinatus and teres minor not torn or greatly stretched. However, any assumption that such lesions do not occur in the living is unwarranted, for the conditions are so different. In such experiments lax atonic tissues replace the living contractile muscles, and the force is gradually and gently applied as compared to the sudden smashing force acting in the living. A force suddenly applied against active muscles would have much greater rupturing power than a much greater force evenly applied against dead muscles.
One of the earliest mentions of the role of the supraspinatus was by Duchenne, who wrote: "Recurrent dislocation cannot occur with a normal supraspinatus." Yet I do not entirely agree with this great authority, for in none of my cases of habitual dislocation have I demonstrated such a rupture, and in two I actually did demonstrate that there was no rupture. Furthermore, I have never seen habitual dislocation complicate a case of ruptured supraspinatus.
Speed states that the head of the humerus twists out of the glenoid through the inferior portion of the capsule, and he believes that to permit this dislocation there must be a great strain on the supraspinatus tendon, or even a tear in it.
It is in the treatment of these recurrent cases that the greatest variations of opinion are to be found. Almost every author has contributed a different technique. The surprising thing is that so many varied methods should produce such uniformly excellent results as are claimed for them, yet the number of methods suggests that none is highly successful. The essential points of some of these methods of treatment will be briefly given with their results, when obtainable. Many of the reports are based upon too few cases followed for too brief a period. It is noticeable that few authors have reported later series in a second paper, and this suggests that the late results and greater experience have not supported them in their early statements.

Treatment.

Two general principles of treatment have been applied to habitual dislocation. They are:

Prevention—control primary dislocation, and allow healing of capsule.
Reconstruction.
A. Suspending head of humerus from above.
B. Support from below.
1. Reefing.
2. Bone operation on glenoid.
C. Combinations of above.
D. Use of the long head of the biceps as a round ligament.
A shearing-off of the attachment of the capsule to the fibrocartilage of the glenoid is described by Bankart as the cause of recurrent dislocation. The defect is permanent and his operation aims to repair the rent. His incision runs from above the clavicle downward and outward over the coracoid for about five inches. The deltoid and pectoralis major are separated, not cut, and the coracoid divided and driven downward with the muscles attached. The subscapularis tendon is divided and the capsule sutured to the glenoidal labium. The subscapularis and coracoid are sutured in place. Four weeks of rest is followed by active and passive motion. Four successful cases are reported.
Carrell, who gives the above classification of treatment, uses an ingenious combination of A. and B. An anterior incision exposes the long head of the biceps. The tendon is sectioned at its lowest level, and reflected from its sheath to where it emerges from the capsule. The distal end of the muscle is attached to the short head. To the free tendon is attached a piece of fascia about six inches long. A posterior incision running down four inches from the acromion separates the deltoid and exposes the teres minor. The fascia is passed under the neck, weaving in and out of the capsule. It emerges just above the teres minor and is passed through a drill hole in the acromion. The arm is immobilized at the side and motion begun in three weeks. Good results are reported in four cases. One wonders whether the posterior incision can be made without injury to the circumflex nerve. Recently Fowler has suggested a modification of this suspension operation. The biceps tendon is not interfered with, but a strip of fascia lata is passed through the capsule below the neck and anchored, both on the acromion and on the coracoid.
A bone transplant was placed by Eden under the raised periosteum of the neck of the scapula so that one-half to one centimeter stuck out in front of the joint. He also reefed the capsule and kept the arm abducted for three weeks.
Henderson's tenosuspension operation has been popular in America, but as seen by the discussion following Fowler's paper, it cannot be a thoroughly satisfactory procedure. Keller uses a crucial plication of the capsule through a posterior incision. Loeffler places a band of fascia from the greater tuberosity of the humerus to the acromion. Mandl used Finsterer's operation with success. The head of the humerus is held back by a band on the anterior surface of the joint, taking the place of the normal joint capsule. The band is composed of "part of the coraco-brachialis and part of the biceps." Oudard divides the subscapularis and overlaps it so as to shorten it about three centimeters. The tip of the coracoid is cut and a bone graft three to four centimeters long is inserted between base and tip. The coracoid may be slit and one-half slid down so as to lengthen the coracoid three centimeters. Nine cases were treated successfully. Six additional cases are reported. Perkins devised an operation in 1906 for suture of the torn capsule and reports good results. A restraining ligament was made by Plummer and Potts using a fascial strip from the greater tuberosity to the acromion. They report two cases with good results. Nine cases of recurring dislocation were treated in a year by Riviere, who pleated the capsule by placing interrupted sutures through the subscapu-laris. Landes uses a fascia lata cord or several silk sutures and suspends the head of the humerus by passing this cord through a drill hole and slinging it over the clavicle just lateral to the coracoid. Selig, who considers atrophy or rupture of the external rotators the main cause of habitual dislocation, makes an incision through the supraspinatus fossa, separates the trapezius fibers, and shortens the supraspinatus tendon by plication.
It is Sever's belief that the subscapularis and supraspinatus prevent dislocation when the arm is elevated by opposing the pectoralis major, which adducts and draws the humerus forward, and pulls the upper part of the humerus inward and downward. He says that in all operations for recurrence, the good comes from cutting the pectoralis major and shortening the subscapularis. No results are stated. He notes that repair of the infraspinatus and supraspinatus can also be done at the same time. Other authors, notably Allis, have also held similar views.
The operation advocated by Speed is done through an incision just below the coracoid and extending down four inches. The pectoralis major is divided one and one-half inches from its insertion into the humerus, and the axillary structures put aside. The edge of the glenoid is next palpated, after which, a drill hole one inch deep is made diagonally into the neck of the scapula. A bone transplant from the tibia is driven in with three-fourths inch projecting. This is supposed to prevent the head of the humerus from slipping out forward into anterior dislocation, at the same time not interfering with the normal range of motion.
A heavy silk ligature reenforces the anterior part of the capsule in the operation of Spitzy. A curved incision exposes the deltoid insertion, which is cut and retracted. A heavy silk ligature is passed around the surgical neck and tied in front. The ends are left long so that they can pass upward anterior to the capsule, and be tied over the coracoid. The capsule is then folded over the ligature and sewed, thus shortening the capsule. The deltoid is re-attached, and after a rest period of four weeks exercise is begun.
Thomas was an exponent of the capsule pleating operation. He used a posterior axillary incision, and took a reef in the capsule. He claimed exceedingly good results, as do the others. He performed capsulorrhaphy on eighteen epileptics suffering from recurrent dislocation. Twelve cases were successful, for a time at least. A capsule pleat and fascial transplant across the front of the joint is performed by Valtancoli, who reports eighty-six per cent cures.
It would seem that a patient stands some chance of cure by any of these methods. Therefore, it would be to the patient's advantage to choose the simplest, since his chances of recovery are as good as if he had the most complicated one. It is interesting to speculate why such a diversity of treatments should produce so uniform a result. It may be explained by the temporary or permanent limitation of joint function consequent to the operation. Some of the above procedures have as an object the limitation of motion, and all of them probably do limit motion. The trauma of the instrumentation, the bleeding and exudate, and the placing of sutures result in the formation of scar tissue. In addition the arm is immobilized for a time. Fixation and a sensitive scar produce pain on motion, and a certain mental impression which results in a patient's using his arm in a very gingerly way for a long time. Actual limitation or voluntary limitation are important reasons why the arm is not soon again moved into extreme elevation. It is highly probable that the late results of all these methods would not be entirely satisfactory.
Some authors have advocated and devised external apparatus to check abduction within a safe limit. These hobbles are a nuisance and offer no cure, but do prevent dislocation. The lesion is annoying and causes so much disability that many of these cases beg for operation. The treatment should be suited to the type of lesion and to the habits of the individual patient. Bony defects should be repaired or modified by plastic methods. Nicola's operation seems to be applicable, whatever the cause.
The writer has on two occasions done negative exploratory operations for this condition by opening the bursa but without entering the joint. The following case may be of interest to those who believe that deformities of the head of the bone may be the cause of recurrent dislocation, for in this patient a thorough exploration was done.

Case No. 24. Mr. K. N. Age 26. Massachusetts General Hospital No. 182833 E. S., May 22, 1912.

A large, powerful young man. First injury six months before while wrestling. Repeated dislocations after slight muscular efforts since then. "Sabre-cut" incision, supraspinatus divided and joint explored. The capsule was found to be torn, especially the portions at the lower and inner edge of the glenoid. A sort of hernia of the synovial membrane existed, which evidently made a pouch for the head when dislocated. A plastic repair was done on this part of the capsule. Part of the articular surface was missing, as if it had been broken off and absorbed. The patient was seen by me about a year after the operation, and at that time had a perfect result. I have not been able to trace him since.

This particular condition of axillary tearing of the capsule has been described by Thomas of Philadelphia, and considered by him to be the most common lesion in shoulder injuries. I have little doubt that it is a factor common to all recurrent dislocations. One cannot imagine dislocations occurring without a tear of the capsule of the joint. In all these cases the pillars of capsule which bound the opening of the bursa subscapularis must be more or less torn to enable the head of the humerus to lie in the subcoracoid position.
I have seen numerous cases of habitual dislocation, but owing to my lack of faith in any particular technique I have done few operations. I have been content to teach the patient about the mechanism of dislocation and explain to him that he cannot dislocate his arm without combining rotation and abduction. He may abduct the arm as much as he is able to do so in internal rotation in the coronal plane with impunity. These cases are usually in young men, and as has been said before, in athletes or in epileptics. Athletes may avoid dislocation by giving up those forms of athletics which tend to produce it. I have known two young men, who were my personal friends, both of whom were subject to this annoying difficulty. Both patients eventually outgrew it or changed their habits so that it did not occur. One of them, for instance, had to give up boxing because the arm would at times dislocate if he gave a forward blow. In doing this, the relation of scapula and humerus are practically the same as when they are in the pivotal position. He was a skillful athlete at other forms of amusement. It seems to me that for this type of patient it is better to change habits than to submit to operation.
In the cases of epileptics, it is imperative that the patient should wear an apparatus which prevents the combination of external rotation and abduction or should be operated upon. It has not been my fortune to have the care of any such cases. Should I be compelled to operate for this condition, I should at present choose the operation of Nicola. I here reprint some remarks made by Dr. Nicola at the discussion of Dr. Fowler's paper.
"For three years I have been using my own operation, which does not utilize any foreign material. It is done through one incision, the convalescence is short, and so far as I know there have been no recurrences on operations done by me as well as by about thirty other operators. It seems to me that it is getting more and more difficult for the student of orthopedics to decide which type of operation to use. In the end the operation that will become most popular is the one that is very simple to perform and can be done most frequently on almost any type of dislocation, no matter what the pathologic changes are (bony defects, muscle tears or capsular tears) ; and, finally, it is a matter of convalescence. In the operation which I have been doing, the line of incision begins just above the coracoid process and extends down and out in the line of the fibers of the deltoid. In my original description I stated that this should come between the pectoralis major and the deltoid, but I find that it is easy to approach it merely by going through the lines of the fibers of the deltoid. Before cutting the tendon, one should be sure to put transfixion sutures in both ends because frequently the arm may extend and the lower segment of the biceps tendon will slip behind the pectoralis and cause great anxiety. After the tendon is divided, a hole is drilled through the head of the humerus. I usually go anywhere along the bicipital groove and point the drill so that it comes out at the upper end of the angle of the head. The tendon is passed through the head and is sutured on itself, so that there is no muscle loss and the tendon has a tendency to restrict the movement and, therefore, keeps the head in the glenoid cavity. Some of the men have used this operation for fracture of the surgical neclc of the humerus when there has been downward displacement of the head into the axilla, and there they replace the head in position and drill a hole so that they maintain the head in position."
This operation appeals to me as more likely to fulfill the conditions required than any of the others. Fowler's operation also seems to me a rational procedure, but not so simple as Nicola's.
Extract from a personal letter from Dr. Nicola, June 6, 1930: "The cases reported in the reprint which you received, together with the rest, have been followed over a period of two years. The boxer has been back in the ring and has won two semifinal contests with no recurrence of dislocation. Case No. 3, which was an epileptic, was killed in an auto accident eight months after the operation. Through friendship with the coroner, I was able to examine the tendon of the long head of the biceps with special reference to the point which you made in your letter. I found that instead of thinning out of the long head of the biceps which extended to the glenoid cavity, the tendon above the humerus was thickened about the size of the little finger."
Extract from personal letter from Dr. Nicola, June 6, 1932: "I have personally done twenty-four of these operations with one hundred per cent cures. I have not heard of any recurrences from the various men who are associated with me at the Hospital for the Ruptured and Crippled. I hope that you will soon find an opportunity to operate upon such a case and to convince yourself that this operation is very simple to perform. I am now doing it through a two and one-half inch incision taken just below the clavicle on the inner side of the coracoid process and extending downward through the fibers of the deltoid muscle. The hole through the head of the humerus is made with a one-fourth inch gauge, instead of a drill. This facilitates matters considerably."
This operation I am sure could be readily done through my routine bursal incision which separates the deltoid fibers directly over the bicipital groove.

INFANTILE DISLOCATION OF THE SHOULDER

Lesions of the bursa or of the supraspinatus tendon in childhood apparently do not occur, at least they have never fallen within my experience. However, a not very infrequent lesion in childhood, namely, birth palsy complicated by dislocation of the shoulder, sometimes causes confusion in the diagnosis of shoulder lesions in later years. We see the shoulder deformed from a lesion which occurred at or soon after birth.
There has been much discussion as to whether the term congenital dislocation of the shoulder joint should ever be used. It seems very probable that a large number of so-called congenital subluxations, if not a majority of the published cases, were instances of obstetric palsy in which the dislocation remained after the paralysis had recovered. Infantile dislocation may be discussed under three headings, according to whether it existed before birth, occurred at birth or resulted soon after from paralysis caused at birth.

(1) Abnormality of development—true congenital dislocation. The existence of such a clinical entity has been questioned, but it has been established without any doubt, although it must be very rare. R. W. Smith of Dublin, in 1839, was the first to bring this condition before the profession. He published an account of three cases in the Dublin Journal of that year. Two of these were males, age 20. The dislocation was subcoracoid. The muscles about the shoulder were wasted. One patient had club foot. The third case was an insane woman, age 29, in whom the condition was bilateral.
At post-mortem examination there were facets just under the cora-coid, with a displacement of the capsule anteriorly to enclose the joint. The head of the humerus was flattened, and the acromion and coracoid elongated and hooked downward. In all the cases abduction was limited. Eleven years later Smith published two additional cases. In 1841 Guerin presented two cases and demonstrated a symmelian foetus which showed this abnormality on both sides. Since these reports, numerous cases have appeared in the literature. Grieg analyzed the cases of fifty-eight authors in the Edinburgh Medical Journal of 1923. He makes the following statement. "So far I have only found twelve cases reported to date in which evidence brought before the profession fails to justify any other conclusion than that they are cases of true primary congenital dislocation of the shoulder."

(2) Dislocation produced by obstetric manipulation or during birth. This group is open to criticism because proof of its existence is not satisfactory. T. T. Thomas was firmly of the opinion that traumatic dislocation not only occurs, but is the primary factor with regard to paralysis. He believed that paralysis is secondary to a rent in the capsule due to a traumatic dislocation. Taylor, writing in 1921, states that neither he nor any of three obstetricians of a large Lying-in Hospital had ever seen a case of Erb's palsy in which the subluxation preceded paralysis. In 1866 Loignan wrote a thesis for a Paris doctorate on the subject. He found that he could not dislocate the shoulder by manipulation. The constant lesion which occurred, if sufficient force were used, was a fracture of the humeral shaft through the soft bone under the epiphysis. Other investigators, notably Sever, have been unable to produce traumatic dislocation or rupture of the capsule by manipulation in infant cadavers. The writer feels that dislocation occurring at birth is so rare as to be negligible in diagnosis.

(3) Acquired subluxation due to injury of the plexus. Obstetric paralysis was first described by Smellie in 1768. He thought the condition was due to prolonged pressure on the arm while the child was in the pelvis. It was brought before the profession, however, by Duchenne, who in 1872 described four cases in infants and believed it to be due to pressure on the nerve trunks. Erb described the palsy in adults in 1874. Since that time it has been known as Erb-Duchenne paralysis. Erb believed it to be due to pressure on the fifth cervical root, known as Erb's point. Fieux opposed this view and adopted the theory that traction is responsible. He demonstrated on infant cadavers the fact that when the head is forcibly drawn away from the shoulder, the fifth cervical root is torn just proximal to its junction with the sixth nerve. With more force, the latter nerve may also be torn. Only the muscles of the upper arm are paralyzed. The palsy is usually flaccid.
Infants with Erb's palsy present a typical history and appearance. There is usually a difficult birth where traction on the head has been made under ether relaxation. The arm hangs limp and vertically at the side, the elbow is extended and the forearm pro-nated. There is inability to abduct, elevate, outwardly rotate, or supinate. There is extreme internal rotation so that the palm often faces outward. After a short time, there is wasting from disuse, and flattening of the shoulder soon appears. Passive motions' are free at first, but the healthy muscles soon contract and produce limitation of motion—notably of external rotation. The muscles paralyzed are the deltoid, supra- and infra-spinatus, teres minor, biceps, brachialis and brachioradialis. There is no sensory disturbance.
Clark, Taylor and Prout estimated one case of palsy in 2,000 births. Most cases of birth palsy show some luxation of the head of the humerus. Fairbanks saw twenty-eight subluxations in thirty-seven cases of palsy, or seventy-six per cent; Thomas reported nine in twelve. Taylor has reported sixty-eight cases, forty-six of which showed subluxation. He has never seen the condition in patients less than six weeks old. Of those patients who had palsy, who were more than six weeks old, seventy-seven per cent showed subluxation. In 109 X-ray studies reported by Sever in 1916, sixty-four or fifty-nine per cent showed subluxation. The ages in this series varied from one day to eighteen years.
It should be noted that this form of dislocation is posterior, while the first two forms are anterior or inferior.

Mechanism of Posterior Subluxation. The appearance of the arm soon undergoes a change from the flaccid condition which follows the immediate injury for a few weeks after birth. The upper arm is brought forward and adducted by contraction of the well muscles. The elbow is usually a little flexed, the pronated forearm passing downward and inward across the front of the body. Abduction is checked before the arm comes to a right angle. Backward motion is usually impossible and external rotation is markedly limited. With the elbow at the side, it is often impossible to rotate the humerus out sufficiently to bring the forearm into the forward plane. The bones of the affected side—the humerus, scapula and clavicle—are smaller than those on the opposite side. This is an important point in the diagnosis of late cases. The front of the shoulder is flattened, while there is a fullness behind, below the acromion, due to the head of the humerus. The muscles which tend to prevent posterior dislocation are the teres minor, supraspinatus, infraspinatus, and posterior part of the deltoid. The pectoralis major, the teres major and latissimus dorsi are rarely even partially paralyzed and rotate the humerus strongly inward. The subscapularis acts as a powerful internal rotator. These muscles become contracted while the paralyzed ones are stretched. The teres major and latissimus dorsi exert traction downward and posteriorly. The anterior portion of the capsule becomes shortened secondarily. Since the arm is held in an internally rotated position, there is a constant jstrain on the neck of the humerus, tending to twist it backward. In the plastic young bone, this twisting occurs and the plane of the head of the bone to the shaft may be changed ten or fifteen degrees. The dislocation is not truly posterior—it is rather a rotation of the head than a dislocation, so that the articular portion is rotated backward and the side of the head lies on the glenoid without having escaped from its capsule.
During the first year nothing can be seen in the way of bony deformity in the X-ray, except possibly a slight posterior subluxation and relatively small size of the head compared to that of the other side. As the child grows older, the subluxation increases. There is increased outward displacement and elevation of the scapula. The acromion and coracoid become hooked downward in front of the head of the humerus. The clavicle is shortened and its curves are more marked than in the normal. The coracoid process is usually elongated. The glenoid becomes shallow. These changes of the bones occur while the paralysis exists, and even if the paralysis clears up, they persist.

Treatment. In early cases the arm may be held in abduction, elevation, external rotation and supination by a light wire splint. Sever, however, prefers to let the child use the hand and arm freely with the risk of contractures. Passive motion and massage are carried out at frequent intervals. Operation is deferred until the child is three or four years of age. Once contractures have developed, it is best to cut the contracted muscles. Manipulation is of little value because of the tendency to recurrence, unless the paralyzed muscles have regained their tone. Sever has described his operation at length in a paper read before the Section on Orthopedic Surgery of the American Medical Association, 1925. He cuts the pectoralis and subscapularis tendons and removes one-half inch to three-quarters inch of the tip of the coracoid with its muscle attachments. If necessary he removes the hooked acromion to allow reduction. The arm is put up in a light splint in abduction, elevation, external rotation and supination. Muscle reeducation by active and passive motion is begun after eight to ten days. The splint is worn night and day for three months, but is removed daily for exercises.

Prognosis. This depends largely on the recovery of the paralyzed muscles in early cases. If the child is seen early, contractures and subluxation may be minimized by passive motion until the nerves have regenerated. In late cases, however, where contractures have developed and there is no tendency of the nerves to regenerate, operation has to be resorted to and gives a good, hut not brilliant, functional result. Sever records partial recovery in 297 of 394 cases which were operated upon. After operation there is great difficulty in inwardly rotating the arm. He states that this may be eventually overcome, however.
I have had very little personal experience in these cases, but the following case taught me such an important lesson that an account of it is presented in the hope that it may stimulate some one to follow up a series of such cases in which operations had been done in childhood.

CASE 70.
A strong boy, age 14, was referred to me for trouble with his shoulder, with the story that he had had difficulty since he was a baby, and that while he was a very strong, active boy otherwise, he was greatly handicapped by his shrunken, weak, deformed right arm. The diagnosis in the case puzzled me a good deal at first, for there was no paralysis, and the X-ray simply showed a rather small and deformed humeral head and glenoid cavity. In spite of this, by palpation, it was easy to feel that the head of the humerus was posterior to the glenoid under the acromion. Both the coracoid and the acromion were hooked down in an unnatural manner, which was easy to understand when one recognized the true character of the lesion, for the acromion process had nothing beneath it and was not performing its normal function. All parts of the shoulder, including the bones, were smaller than those of the opposite side. There was practically no motion in the scapulo-humeral joint and the arm was held in internal rotation. An extraordinary amount of compensatory mobility had developed in the motion of the scapula on the chest wall— not only in flexion and extension, but in abduction and adduction.
It was clearly a case of birth palsy in which the bones had remained out of place after the muscular paralyses had recovered, and therefore the patient now only suffered from the consequence of the luxation.
I operated on June 16, 1921, through a "sabre-cut" incision, and to my surprise, found that the cartilaginous surfaces of the glenoid and of the head of the humerus had remained in nearly a normal condition, although they had been separated for so many years. The capsule was stretched and distorted, but not disrupted. The cartilaginous surface of the glenoid was rather puckered and the articular head of the humerus was small and rather misshapen, although less so than one would think from the appearance in the X-ray, which of course showed the surface of the bony centers of the epiphysis and not the cartilage. The contraction of the subscapularis and pectoralis major was so great that I had to divide their tendons in order to get the head of the bone in place. The coracoid process was so deformed that I had to excise about two-thirds of it subperiosteal^ in order to reduce the humerus. The "sabre-cut" incision, of course, mobilized the acromion. After reducing the head of the bone, I was able to put four silk sutures "a-distance" to reunite the cut ends of the subscapularis. I did not attempt to correct the torsion of the neck, although it caused some eversion of the arm when the head of the bone was in place. The whole wound was sutured, and the patient was put up in plaster in semi-abduction and semi-external rotation.
It was most remarkable to watch the boy's convalescence. There was a good surgical recovery, but the miraculous part was to see the promptness with which the bones and muscles tended to grow into normal condition. Within six months he had nearly normal use of his shoulder, and the condition of the muscles had greatly improved.
As the patient lived in another city I lost track of him about six months after the operation and did not see him again for ten years, when I looked him up in preparation for this book. It is fortunate that I did so, for the lesson which I learned was important and may be of help to others.
During the ten years that had passed, the boy had become a man of twenty-four, whose occupation was in moving buildings. He did much of the manual labor himself. When he came into my office he looked strong and vigorous, and I had to ask him which shoulder was the bad one. Then my disappointment came.
A skillfully made movable pad inside his coat concealed the small size of his right shoulder. His vigorous handshake and well-developed forearm gave no hint of the practically ankylosed joint which was displayed when he removed his clothes. On closer examination I found both coracoid and acromion clutching down on the head of the bone like crooked fingers grasping it and holding it fixed. It appeared as if the acromion process had bent downward from the point where I had divided it and had become fixed in this position.
After a time the explanation occurred to me. At fourteen, the acromion and coracoid are cartilaginous epiphyses, for they have not yet ossified. After my operation, although the head of the humerus was in place, it was small and underdeveloped because of imperfect function for fourteen years. Consequently the cartilaginous acromion and coracoid became bent down over it, grasped it, and then, at about twenty, turned to bone and held it fixed. I did not at the time of the operation realize that the greater part of the acromion does not unite with the spinous process until about twenty. I think now that if I had insisted that this boy should have slept with his arm elevated until he was twenty, and had kept up appropriate exercises, he might have obtained a more perfect shoulder. It is not a great hardship to form the habit of sleeping with the arm in the hammock position. Many people do this by preference. He had been able to hold his arm in this position when I last saw him six months after the operation. Later the strength of the divided internal rotators returned and tended to rotate the arm to its old position, and also to resist elevation in external rotation. The head of the bone being small, the cartilaginous acromion slowly yielded to fit over its convexity. I think that it is highly probable that if the late results of other operations which have been done for these cases were critically examined, the same disappointing condition might be found in later years. Operations should not be undertaken on these cases unless the parents are warned that the patient should be under the surgeon's care until his epiphyses are united; i.e., when the patient is about twenty. I am inclined to think that nature's results at the end of ten years would compare very favorably with those of surgeons.

ACROMIO-CLAVICULAR DISLOCATION

A brief consideration of lesions of the acromio-clavicular joint seems advisable, although strictly speaking, neither the subacromial bursa nor the supraspinatus tendon are involved. One must remember that the coraco-acromial ligament intervenes between these structures. When this joint is dislocated the coraco-acromial ligament goes intact with the scapula. In severe cases the coraco-clavicular ligaments (conoid and trapezoid) are torn.
Mechanism. The acromio-clavicular joint, itself, is weak, but the conjunction of the two bones derives its strength from the conoid and trapezoid ligaments which are attached to the coracoid process of the scapula. Upward dislocation of the clavicle is favored by the upward and outward slope of the joint. The clavicular facet looks downward, outward, and backward. Dislocation is almost always caused by direct violence. A blow on the back of the acromion or a fall on the tip of the shoulder drives the acromion downward, inward, and forward, and the clavicle with the coracoid process as a fulcrum is torn away.
Dislocation is classed as complete or incomplete according to whether or not the facets clear each other. The ligaments of the joint itself are more or less torn, even in incomplete dislocation, but the conoid and trapezoid ligaments are usually torn in complete dislocation.
Diagnosis. The diagnosis is to be made from the history of trauma, pain and disability. The outer end of the clavicle is prominent and movable, and can be readily reduced, but reduction is hard to maintain if the coraco-clavicular ligaments are ruptured.
Treatment. Upward, outward, and backward traction on the scapula is indicated and can be applied by various braces or by recumbency. The most favored method is the clavicular cross. A T-shaped splint is applied to the back, and the shoulders strapped to the cross arms.
Open reduction and fixation are occasionally necessary. Several operations have been devised, most of them using fascial strips. Representative among these may be cited Bunnell's ingenious method. He threads a cord of fascia through holes in the acromion and clavicle, and places a loop under the coracoid process.
Prognosis. If the reduction can be maintained, the chances are good that a patient will regain function in the course of several months, but soreness and some pain may persist for years. Arthritic changes may take place. I personally have never found it necessary to operate on acromio-clavicular dislocation, but in extreme cases I should recommend Bunnell's operation.

ACROMIO-CLAVICULAR ARTHRITIS

In contrast to the mechanism of the scapulo-humeral articulation, that of the acromio-clavicular joint is typical of the kind in which arthritis is prone to occur. It is a hinge joint with a very limited degree of motion. For its size, when in action, it carries an immense burden of weight. For instance, as one pushes open a heavy door, this little joint has to bear the equivalent weight of almost the^ whole power exerted. The same is true of the joint on the sternal end of the clavicle, but that joint has a much larger surface area. In laboring men who carry or lift heavy burdens, spurring from arthritis of the acromio-clavicular joint is so common as to form almost as normal a tissue as the great calluses in their hands. In many of the older individuals, the rims of new-formed bone actually fuse, so that the joint becomes obliterated. These changes may progress with very little pain and discomfort to the individual, or they may be accompanied by the usual signs of arthritis, which occasionally are so severe that they incapacitate the patient.
The acromio-clavicular joint holds an exposed position on the shoulder, and falling objects not infrequently strike the joint directly—perhaps breaking some of the small bony lips, causing hemorrhage about or in the joint. Such cases may be laid up for months on account of the local tenderness when they attempt to use the arm. I find it very difficult, in giving an opinion on compensation cases, to state when such individuals should be expected to return to work. The X-ray appearance is far from being a criterion. A man may have a very ragged and hypertrophied-looking joint and yet be conscious of no symptoms. Another man with barely perceptible changes may have much local tenderness. On the whole, it is surprising how well these laboring men are able to bear acromioclavicular arthritis. The diagnosis of these lesions rests entirely on the readily ascertained facts of localized swelling and tenderness, supported by the X-ray evidence of lipping of the joint. Confusion in diagnosis only arises when one allows one's self to center his attention on this joint and to ignore other really more important lesions. Never forget that this condition may attract your attention too readily, and by its presence conceal a lesion of the supraspinatus which is far more serious. Acromio-clavicular arthritis must be judged by the degree of symptoms, not by its X-ray appearance, for often there is much lipping of the edges of these joints and yet no symptoms at all.
Treatment. As a rule, these cases respond well to rest. A few weeks' confinement of the arm in a sling soon after a bruise on one of these joints is all that should be attempted. I am convinced that complete fixation of this joint is unfortunate. I do think that rest is very important in acute stages. Patients who have had prolonged symptoms have usually had either prolonged energetic treatment or prolonged fixation.
In a few subacute and prolonged cases, I have cut into the joint with the same idea that one has in cases of periostitis, where one incises to cause relief of tension. As a rule, however, I believe that simple rest is the only form of treatment which is important. The usual physiotherapy methods may be of some use, but my personal experience with them has been little.
Remember that the acromio-clavicular joint is not in immediate anatomic relation with the subacromial bursa. The coraco-acromial ligament intervenes. Therefore, acromio-clavicular arthritis does not prevent rotation or abduction in the scapulo-humeral joint, except in extreme positions. If these motions are not present, do not blame the acromio-clavicular joint entirely, even if it is swollen and tender.
Arthritic changes in this joint commonly occur after luxation or subluxation, and soreness may continue many months and sometimes a few years after such accidents. Men who do their own work generally continue at it in spite of this protracted soreness, but employees are apt to find their shoulders too sore to permit labor, if their compensation is paid. Thus this little lesion may be the cause of their never working again, for it is a commonplace that a year of loafing is a serious matter for an elderly laborer. Surgical obliteration of the joint should be considered, in some cases at least, as a mental stimulant. It is not an important joint.

BIBLIOGRAPHY

BANKART, A. S. B. Recurrent or habitual dislocation of the shoulder joint.
Brit. M. J. 1923. 2. 1182-1133. BUNNELL, S. Fascial graft for dislocation of acromio-clavicular joint.
Surg. Gyn. and Obst. 1928. 46. 563-564. CARRELL, W. B. Habitual dislocation of the shoulder.
J. A. M. A. 1927. 89. 948-952. DELBET, P. Des luxations anciennes et irreductibles de l'epaule.
Arch. Gen. de Med. 1893. ser. 7. vol. 81. 19-39. DOLI.INGER, J. Die Veralteten traumatischen Verrenkungen der Schulter; des
Ellenbogens und der Hufte.
Ergebnisse der Chir. und Orthop. 1911. 3. 83-194. DOI.LINGER, J. Das anatomische Hinderniss der Reposition bei veralteten sub-
coracoidealen Schulterverrenkungen und meine Methode zur blutigen Reposition dieser Verrenkung.
Deut. Zeit. fur Chir. 1902-03. 66. 819-335. DUCHENNE, G. B. Physiologie des mouvements.
Paris. J.-B. Bailliere et Fils. 1867. pp. 7-17. EDEN, R. T. Habitual dislocation of shoulder.
Zentralbl. f. Chir. 1920. 47. 1002. ELIASON, E. T. Nelson's System of Surg. vol. 3. p. 292-293. FIEUX, see Bibl., Chap. XI. FINSTERER, H. Zur Frage nach der zweckmassigsten Behandlung der habituellen
Schulter luxation.
Wien. Med. Woch. 1924. 74. 1232-1237. FOURMESTRAUX, J. DE. Les luxations recidivantes de l'epaule; pathogenie; traite-
ment.
Arch. Med.-Chir. de Province. 1920. 10. 18-26. FOWLER, E. B. A new operation for recurrent dislocation of the shoulder.
J. A. M. A. 1932. 98. 476-478. GERSTER, A. G. Subcoracoid dislocation of the humerus; paralysis of the serratus
magnus; arthrotomy.
Med. News, Phila. 1884. 44. 423. GOEBEL, W. Zur Prognose der traumatischen Schultergelenksluxation.
Zeit. fur Artzl. Fortbildung. 1909. 6. 347-855. GRASSNER, R. Die Briiche des grossen Oberarmhockers.
Veroff. aus dem Gebiete des Milit.-Sanitat. 1906. 85. 180-198. GRATZ AND ROBINSON. Am. J. Surg. XV. 1932. 71. January. GUBLER, H. Zur Prognose der Schultergelenksluxationem.
Schweiz. Med. Woch. 1922. 52. 960-964.
Abst. J. A. M. A. 1922. 79. 1964. HENDERSON, M. S. "Tenosuspension" for habitual dislocation of the shoulder.
Surg. Gyn. and Obst. 1926. 43. 18-25. HILDEBRAND. Zur operativen Behandlung der habituellen Schulterluxation.
Arch, fur Klin. Chir. 1902. 66. 360-364.
KELLER, W. L. Treatment of chronic recurrent dislocation of the shoulder by
crucial capsular plication.
Ann. Surg. 1925. 81. 143-148. KOCHER, THEODORE. Eine neue Reductionsmethode fiir Schulterverrenkung.
Berl. Klin. Wchnschr. 1870. 7. 101-105.
Bull. Soc. Med. de la Suisse Rom. Lausanne. 1873. 7. 819-330. 3 pi. KUTTNER. Zur Prognose der traumatischen Luxation.
Zentralbl. fur Chir. 1908. 35. Beilage p. 155-157. LANDES, T. L. Recurring dislocation of the shoulder joint.
Brit. Med. J. 1921. 2. 321-822.
LEXER, K. Nachuntersuchungen von traumatischern Schultergelenksluxation. Beitr. zur Klin. Chir. 1910. 70. 221-235.
LOEFFLER, F. Die Behandlung der habituellen Schulterluxation durch Bildung
eines extraartikularen Hemmungsbandes.
Zbl. fur Chir. 1920. 47. 324-326. MANDL, F. Bemerkungen zur Operation der habituellen Schulterluxation.
Deut. Zeitschr. fur Chir. 1925. 191. 108-120. NICOLA, T. Recurrent anterior dislocation of the shoulder; a new operation.
J. Bone and Joint Surg. 1929. 11. 128-182.
NICOLA, T. Recurrent dislocation of the shoulder; its treatment by transplantation of the long head of the biceps. Amer. J. Surg. 1929. 6. 815.
NICOLA, T. Operation for relief of recurrent dislocation with presentation of
patients.
Amer. J. Surg. 1931. 11. 119-121. OUDARD. La luxation recidivante de F6paule (varied ante>o-interne).
J. de Chir. 1924. 23. 13-25.
Abst. J. A. M. A. 1924. 82. 1004. OUDAFD. La luxation recidivante de l'6paule (variete ante>o-interne).
Presse Med. 1928. 86. 201-202. PERKINS, G. Discussion on the painful shoulder.
Proc. Roy. Soc. Med. (Sect. Orthop.) 1929. 22. 20-80. PERTHES. Munch. Med. Woch. 1905. H, 10. s. 481. PERTHES, G. Results of surgerv in habitual dislocation of humerus.
Dtsch. Ztschr. f. Chir. 192*5. 194. 1-24. Also J. A. M. A. 1926. 86. 589.
PILZ, W. Zur RHntgenuntersuchung der habituellen Schulterverrenkung. Arch, fur Klin. Chir. 1925. 135. 1-22. Abst. J. A. M. A. 1925. 85. 75. Also Zbl. Chir. Soc. 22, s. 1390. 1928.
PLUMMER, W. W. & POTTS, F. N. Two cases of recurrent anterior dislocation of the shoulder. J. Bone and Joint Surg. 1925. 7. 190-198.
PRESTON, M. E. Fractures and dislocations. C. V. Mosby Co., St. Louis. 1915. p. 11-108.
RIVIERE, G. Capsulorrhapie de l'articulation de l'£paule pour luxation recidivante. Lvon Chir. 1918. 15. 437-439. Abst. J. A. M. A. 1919. 72. 612.
SCHI.AEPFER, K. Uncomplicated dislocations of the shoulder; their rational treatment and late results. Amer. J. Med. Sc. 1924. 167. 244-255.
SELIO, R. Die bei der habituellen Schulterluxation gebrauchlichen Operations methoden von anatomischen Grundsatzen aus betrachtet. Was leistet der Musculus supraspinatus. Deut. Zeit. fur Chir. 1915. 132. 581-588.
SEVER, J. W. The rational treatment of fractures of the upper end of the humerus. Report of end results. J. A. M. A. 1923. 80. 1603-1608.
SEVER, J. W. Recurrent dislocation of the shoulder joint. Mechanical consideration of its treatment. J. A. M. A. 1921. 925-927.
SINZ, P. Inaugural-Dissertation. Erlangen. 1982.
SPEED, K. Recurrent anterior dislocation at the shoulder. Operative cure by bone graft. Surg. Gyn. and Obst. 1927. 44. 468-477.
SPEED, K. Fractures and dislocations.
Lea and Febiger, Phila. 1916. p. 857-440.
SPITZY, H. Stabilization of the shoulder joint for habitual dislocation.
Surg. Gyn. and Obst. 1928. 46. 256-257. STEVENS, J. H. The action of the short rotators on the normal abduction of the
arm, with a consideration of their action in some cases of subacromial bursitis
and allied conditions.
Amer. J. Med. Sc. 1909. 138. 870-884. STEVENS, J. H. Dislocation of the shoulder.
Ann. Surg. 1926. 83. 84-103. STEVENS, J. H. Fractures of the upper end of the humerus.
Ann. Surg. 1919. 69. 147-160. STIMSON, L. A. Fractures and dislocations.
Lea and Febiger, Phila. 1917. TAYLOR, R. T. Fracture dislocation of the shoulder. Arch. Surg. 1928. 17. 475-483. THOMAS, T. T. Habitual or recurrent dislocation of the shoulder. Etiology and
pathology.
Amer. J. Med. Sc. 1909. 137. 229-246.
J. A. M. A. 85. No. 16, s. 1202. 1925. TREVES, F. Surgical applied anatomy.
Lea and Febiger, Phila. 5th ed. VALTANCOLI, G. Sulla lussazione abituale di spalla.
Chir. d. Organi di Movimento. 1924. 9. 131-140. WARREN, J. C. Am. J. Med. Sci. 1846. XI. WILSON, P. D. & COCHRANE, W. A. Fractures and dislocations.
Lippincott & Co. 1925. p. 59-153.

NOTE—Sinz (1932) gives a very extensive Bibliography. He recommends a bone transplant to the glenoid (after Perthes or Eden) but apparently was unaware of the work of Nicola.

==References==
<references />

File:Figure 15.png

2021-08-05T15:56:45Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The inferior pilot hole aimed less than 10° away from the glenoid articular surface is drilled first with a K-wire and then with a 2.75 mm cannulated drill in the AGN, located 8 mm from the anterior glenoid. AGN – anterior glenoid neck. G – glenoid.

File:Figure 14.png

2021-08-05T15:56:09Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. A curved osteotome is used to lightly decorticate the AGN from 3 to 5 o'clock position to a healthy and bleeding flat bone bed. AGN – anterior glenoid neck.

File:Figure 13.png

2021-08-05T15:55:30Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The labrum is horizontally released at the level of 3 o'clock position, and the release is extended inferiorly until the 5 o'clock position. A resorbable suture is passed through the superior half of the released labrum (white arrow). Afterward, another suture is passed through the inferior half of the released labrum for later labral reconstruction.

File:Figure 12.png

2021-08-05T15:54:36Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The exact location of the glenohumeral joint is exposed by reducing the anteriorly dislocated humeral head, and a vertical incision is performed in an inferior to a superior direction to protect the axillary nerve. * – anterior capsule.

File:Figure 11B.png

2021-08-05T15:53:32Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The split is additionally increased with a No. 15 blade. AGN – anterior glenoid neck. SSc - Subscapularis, * - anterior capsule.

File:Figure 11A.png

2021-08-05T15:52:09Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. a) The blades of the scissors are extended to widen the split, while a Hohmann retractor is placed between the blades on the medial side of the AGN.

File:Figure 10Bdaads a.png

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Marko.nabergoj:

Left upper extremity of a patient placed in a semi beach-chair position. The arm is placed in abduction and external rotation.

File:Figure 10Ada s.png

2021-08-05T15:49:54Z

Marko.nabergoj:

Left upper extremity of a patient placed in a semi beach-chair position. The arm is placed in abduction and external rotation.

File:Figure 9das as.png

2021-08-05T15:47:40Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. Two 4 mm holes for screw fixation are predrilled perpendicularly and centrally in the coracoid graft, 1 cm apart, and 8-9 mm laterally from the insertion of the coracoacromial.

File:Figure 8q q .png

2021-08-05T15:46:54Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The undersurface of the coracoid process (CP) is flattened and slightly decorticated with a saw blade to create a healthy bleeding surface that will precisely conform to the later prepared anterior glenoid.

File:Figure 7dqwq qd.png

2021-08-05T15:46:17Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The coracoid osteotomy is meticulously finished with a chisel. CP – coracoid process.

File:Figure 64v q.png

2021-08-05T15:45:35Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. A 90° angled saw blade is used for coracoid osteotomy, which is performed at the base of the coracoid process (CP) as far back as possible, however still in front of the coracoclavicular ligaments. CT – conjoined tendon.

File:Figure 5da ada .png

2021-08-05T15:44:46Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The coracoacromial ligament (white arrow) is released 1.5 cm laterally from its attachment on the coracoid process (CP). The arm is abducted and externally rotated for 90° to improve its visualization. CT – conjoined tendon.

File:Figure 4d ada .png

2021-08-05T15:44:03Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. Pectoralis minor (blue arrow) is released from the coracoid process (CP) while the arm is in adduction and internal rotation. CT – conjoined tendon.

File:Figure 3d a aw.png

2021-08-05T15:43:26Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The whole coracoid process with the insertion of pectoralis minor, coracoacromial, and the CT is exposed by placing the Hohmann retractor on its tip.

File:Figure 2da a.png

2021-08-05T15:42:41Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The dissection begins at the level of the Mohrenheim fossa, a triangular region just inferior to the clavicle, between the deltoid and pectoralis major muscles, which do not contain neurovascular structures. The deltopectoral interval is then opened bluntly with two Richardson retractors.

File:Gfaddw .png

2021-08-05T15:39:08Z

Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The tip of the coracoid process is palpated, and the incision is performed under the tip of the coracoid process extending 4 to 5 cm distally.

Anteroinferior Glenohumeral Instability

2021-08-05T15:31:27Z

Marko.nabergoj: Text - Latarjet

==Bullet points==

*One of most common shoulder injuries, 1.7% annual rate in general population.

*High recurrence rate that correlates with age at dislocation, up to 80-90% in teenagers (90% chance for recurrence in age <20).

*The stability of the glenohumeral joint depends on soft tissue stabilizers, bone morphology and dynamic stabilizers such as the rotator cuff and long head of the biceps tendon.

*Osseous lesions, either humeral or glenoid, are identified in 95.0%. The risk of failure of arthroscopic treatment is higher if not addressed. A glenoid bony defect of >20-25% is considered "critical" and is biomechanically highly unstable and require bony procedure to restore bone loss (Latarjet, Bristow, other sources of autograft or allograft).

*A Malgaigne (Hill Sachs) defect is a chondral impaction injury in the posterosuperior humeral head secondary to contact with the glenoid rim. It is present in 80% of traumatic dislocations and 25% of traumatic subluxations.

*Axillary nerve injury is most often a transient neurapraxia of the axillary nerve and is present in up to 5% of patients.

*Incidence of associated rotator cuff tears increase with age of 40 (30% at 40, 80% at 60).

*Static glenohumeral stabilizers are the bone, the ligaments, the capsule, the labrum, and the negative pressure. The dynamic ones are the rotator cuff and long head of biceps tendon.

*The labrum contributes to 50% of additional glenoid depth.

*Anterior static shoulder stability with arm in 90 degrees of abduction and external rotation is provided by the anterior band of inferior glenohumeral ligament (main restraint).

*The middle glenohumeral ligament provides static restraint with arm in 45 degrees of abduction and external rotation.

*The superior glenohumeral ligament provides static restraint with arm at the side.

*The physical examination demonstrates instability if the apprehension test is positive, multidirectional hyperlaxity when the external rotation at side is equal or above 85 degrees, and a pathological laxity of the inferior glenohumeral ligament if the hyperabduction test is positive.

*Three views plain radiographs, including true anteroposterior of the glenohumeral joint, scapular Y (scapular lateral), and Velpeau axillary views are the mainstay of imaging in the setting of acute traumatic anterior instability. Plain radiographs including anteroposterior in neutral, internal and external rotations, scapular Y and Bernageau views are obtained for recurrent instability. Magnetic resonance imaging (MRI) arthrogram is useful to assess for labral or rotator cuff tears, computed tomography (CT) for bone loss assessment.

*Conservative treatment after the first traumatic anterior dislocation is recommended for patients who are not actively engaged in sports, above the age of 30 years old, with a low functional demand, with an associated humeral fracture, or for the athlete with an in-season shoulder dislocation.

*Rehabilitation consist of strengthening of dynamic stabilizers (rotator cuff and periscapular musculature), exercises for proprioception and other specific treatments if apprehension persists.

*Surgical treatment included Bankart repair, capsular plication +/- soft tissue procedures (such as remplissage or dynamic anterior stabilization (DAS) if < 20% bone loss.

*If bone loss ≥ 20%, bone reconstruction with Latarjet, Bristow or free bone block transfers such as Eden-Hybinette is recommended.

==Key words==
Anterior glenohumeral instability; anatomy; humerus; scapula; ligaments; shoulder dislocation; subluxation; reduction; bone loss; Malgaigne; Hill-Sachs; Bankart; capsular shift; remplissage; dynamic anterior stabilization (DAS); Latarjet; Bristow; free bone block transfer; Eden-Hybinette; complication; recurrences; therapeutic implications.

==History==
The first recorded depictions of shoulder reduction are ancient.<ref>Iqbal S, Jacobs U, Akhtar A, Macfarlane RJ, Waseem M. A history of shoulder surgery. Open Orthop J 2013;7:305-9.</ref>

Egyptian hieroglyphs dated 3000 years earlier, pictorially depict a leverage method of shoulder manipulation. They have been followed by the Greeks and Romans. Around 400 BC, Hippocrates, the father of Western medicine, introduced the traction method to reduce the shoulder.
<ref>Hussein MK. Kocher's method is 3,000 years old. J Bone Joint Surg Br 1968;50:669-71.</ref><ref>Celsus A. De Medicina.</ref><ref>Hippocrates. Corpus Hippocraticum—De articulis.</ref>

In 1855, Malgaigne was the first one to describe the humeral bone loss also called Hill-Sachs lesion.<ref>Malgaigne J. Traité des fractures et des luxations. Paris: J.-B. Baillière; 1855.</ref>

In the 1890s, the understanding of the unstable shoulder was elucidated by the work of two French researchers, Broca and Hartman who introduced the concept of capsulolabral damage following dislocations as possible cause of recurrent instability. Notably, most of the findings considered current hallmarks of shoulder instability, including Bankart lesion, bony Bankart, Kim lesion, as well as anterior and posterior labral periosteal sleeve avulsions and glenoid avulsions of glenohumeral ligaments, were described in their papers decades before the eponymous figures to whom they are now commonly assigned depicted them.<ref>Broca A, Hartmann H. Contribution à l'étude des luxations de l'épaule (luxations anciennes et luxations récidivantes). Bull Soc Anat 1890;4:416-23.</ref>

In 1906, Perthes in Germany and a few years later, Bankart in the UK ascertained that the detachment of the labrum caused instability of the shoulder and emphasized reattachment of the labrum to stabilize the joint.<ref>Perthes G. Ueber Operationen beihabitueller Schulterluxation. Dtsch Z Chir 1906;85:199–227.</ref><ref>Bankart AS. Recurrent or Habitual Dislocation of the Shoulder-Joint. British medical journal 1923;2:1132-3.</ref>

Current free bone grafting techniques are based on the initial descriptions by Eden in 1918 and Hybinette in 1932 using autologous iliac crest.<ref>Eden R. Zur Operation der habituellen Schulterluxation unter Mitteilung eines neuen Verfahrens bei Abriss am inneren Pfannenrande. Dsch Z Chir 1918;144:269.</ref><ref>Hybinette S. De la transplantation d’un fragment osseux pour remédier aux luxations récidivantes de l’épaule. Acta Chir Scand 1932:411-45.</ref>

Due to donor site morbidity with autologous iliac crest bone grafting techniques, different auto- and allogeneic bone materials have been evaluated as alternatives. Open and arthroscopic approaches using distal clavicle, femoral head, distal tibial allografts or coracoid process are currently used. The first coracoid process transplant was probably realized by the German surgeon Noeske in 1921.<ref>Anonymous. Zentralbl Chir 1924;43:2402.</ref>

Nowadays, two most popular bony procedures included the Latarjet and its variant, the Bristow.<ref name=":1">Latarjet M. Treatment of recurrent dislocation of the shoulder. Lyon Chir 1954;49:994-7.</ref><ref name=":2">Helfet AJ. Coracoid transplantation for recurring dislocation of the shoulder. J Bone Joint Surg Br 1958;40-B:198-202.</ref>

==Anecdote==
(unpublished data, courtesy of Gilles Walch) At the beginning of the 1950s, Albert Trillat, the head of the orthopedic surgical clinic at the Edouard Herriot Hospital in Lyon (France) and also the promoter of the "no-touch technique", reported combination of an anterior labro-ligamentous complex reinsertion when feasible with a reduction of a so-called coraco-glenoid outlet by means of a coracoid osteoclasy and nail fixation (Figures).<ref>Trillat A. Traitement de la luxation récidivante de l'épaule. Considérations techniques. Lyon Chir 1954:986-93.</ref>
[[File:1562526202257-lg.jpg|thumb|500x500px|Postoperative anteroposterior X-ray of a right Trillat.|alt=|left]]
[[File:1562526204072-lg.jpg|alt=|none|thumb|500x500px|The illustrations demonstrate the effect of the procedure that reduce the coraco-glenoid outlet and lower the subscapularis. Courtesy of Gilles Walch.]]
Another surgeon, Michel Latarjet, who was mainly active in the field of thoracic surgery, visited Dr. Trillat to learn the aforementioned technique. When Latarjet supposedly tried to reproduce the Trillat procedure, he carried an involuntary complete coracoid osteotomy. Thenceforth, not knowing what to do with the bony fragment, he fixed it to the anterior glenoid through the subscapularis using a screw. From this mishap was born the operation which now bears his name.<ref name=":1" />

==Anatomical Considerations==
The glenohumeral joint has six degrees of freedom with minimal bony constraint that provides a large functional range of motion. It thus renders this diarthrodial joint particularly vulnerable to instability. The glenohumeral joint is stabilized by dynamic and static structures. The dynamic stabilizers include the rotator cuff, the long head of the biceps, and the deltoid. The static stabilizers of the joint include the capsule, the glenohumeral ligaments, the labrum, the negative pressure within the joint capsule, and the bony congruity of the joint. The superior glenohumeral ligament functions primarily to resist inferior translation and external rotation of the humeral head in the adducted arm. The middle glenohumeral ligament functions primarily to resist external rotation from 0 degree to 90 degrees and provides anterior stability to the moderately abducted shoulder. The inferior glenohumeral ligament is composed of two bands; anterior and posterior, and the intervening capsule. The primary function of the anterior band of the inferior glenohumeral ligament is to resist anteroinferior translation.<ref name=":3">Burkart AC, Debski RE. Anatomy and function of the glenohumeral ligaments in anterior shoulder instability. Clin Orthop Relat Res 2002:32-9.</ref>

==Prevalence==
The glenohumeral joint is the most commonly dislocated large joint of the body, affecting approximately 1.7% of the general population.<ref>Romeo AA, Cohen BS, Carreira DS. Traumatic anterior shoulder instability. Orthop Clin North Am 2001;32:399-409.</ref>

In greater than 90% of cases, the instability is anterior, has a traumatic origin, and occurs in young athletes involved in contact sports.<ref>Goss TP. Anterior glenohumeral instability. Orthopedics 1988;11:87-95.</ref><ref>Owens BD, Agel J, Mountcastle SB, Cameron KL, Nelson BJ. Incidence of glenohumeral instability in collegiate athletics. Am J Sports Med 2009;37:1750-4.</ref>

Ongoing sports participation in this population is associated with a high recurrence rate.<ref>Owens BD, Dickens JF, Kilcoyne KG, Rue JP. Management of mid-season traumatic anterior shoulder instability in athletes. J Am Acad Orthop Surg 2012;20:518-26.</ref>

==Pathoanatomy and biomechanics==
Anterior shoulder instability usually occurs with an anteriorly directed force applied to an abducted and externally rotated arm, or from a direct blow. During an anterior dislocation, many of the passive and active stabilizers may be damaged. The glenoid labrum, the glenohumeral ligaments, and the glenohumeral joint capsule, representing the soft tissue passive stabilizers will be injured; an avulsion of the anterior labrum, the classic Bankart lesion (Figure) or its variations (glenolabral articular disruption (GLAD), Perthes, anterior labroligamentous periosteal sleeve avulsion (ALPSA)) is almost invariably present,11,22,23 although it does not produce instability in isolation.<ref>Bankart AS. Recurrent or Habitual Dislocation of the Shoulder-Joint. British medical journal 1923;2:1132-3.</ref><ref>Neviaser TJ. The anterior labroligamentous periosteal sleeve avulsion lesion: a cause of anterior instability of the shoulder. Arthroscopy 1993;9:17-21.</ref><ref>Neviaser TJ. The GLAD lesion: another cause of anterior shoulder pain. Arthroscopy 1993;9:22-3.</ref><ref>Speer KP, Deng X, Borrero S, Torzilli PA, Altchek DA, Warren RF. Biomechanical evaluation of a simulated Bankart lesion. J Bone Joint Surg Am 1994;76:1819-26.</ref>
[[File:1562526629855-lg.jpg|thumb|600x600px|A) Coronal T2 MRI views of a right shoulder. The white arrow points a Bankart lesion. B) Arthroscopic view of the same lesion from a posterior portal.|alt=]]
The anteroinferior glenohumeral ligaments and the capsule can be detached from the glenoid rim, and a plastic deformation of the glenohumeral ligaments or an HAGL lesion (Figure) are other common features.<ref>Wolf EM, Cheng JC, Dickson K. Humeral avulsion of glenohumeral ligaments as a cause of anterior shoulder instability. Arthroscopy 1995;11:600-7.</ref>
[[File:1562526631138-lg.jpg|thumb|761x761px|Coronal T2 MRI views of a right shoulder. The white arrow points a HAGL lesion. A retensioning of the inferior glenohumeral ligament (capsular shift according to Neer) will be inefficient.|alt=]]
The plastic deformation of these structures becomes progressively more severe with subsequent episodes.<ref>Bigliani LU, Pollock RG, Soslowsky LJ, Flatow EL, Pawluk RJ, Mow VC. Tensile properties of the inferior glenohumeral ligament. J Orthop Res 1992;10:187-97.</ref><ref>Habermeyer P, Gleyze P, Rickert M. Evolution of lesions of the labrum-ligament complex in posttraumatic anterior shoulder instability: a prospective study. J Shoulder Elbow Surg 1999;8:66-74.</ref><ref>Urayama M, Itoi E, Sashi R, Minagawa H, Sato K. Capsular elongation in shoulders with recurrent anterior dislocation. Quantitative assessment with magnetic resonance arthrography. Am J Sports Med 2003;31:64-7.</ref>

The middle glenohumeral ligament functions to limit both anterior and posterior translations of the arm at 45 degrees of abduction and 45 degrees of external rotation whereas the inferior glenohumeral ligament resists translation of the arm in greater degrees of abduction.<ref name=":3" />

In addition to progressive soft tissue injury, recurrent dislocations can facilitate bony injury. Bony lesions are frequent in recurrent cases and may include defects of the glenoid (bony Bankart or beveling of the anterior glenoid resulting in loss of glenoid concavity), impaction of the posterolateral humeral head (Malgaigne lesion), or even coracoid or proximal humerus fractures (Figure).<ref>Griffith JF, Antonio GE, Yung PS, Wong EM, Yu AB, Ahuja AT, Chan KM. Prevalence, pattern, and spectrum of glenoid bone loss in anterior shoulder dislocation: CT analysis of 218 patients. AJR American journal of roentgenology 2008;190:1247-54.</ref><ref>Buscayret F, Edwards TB, Szabo I, Adeleine P, Coudane H, Walch G. Glenohumeral arthrosis in anterior instability before and after surgical treatment: incidence and contributing factors. Am J Sports Med 2004;32:1165-72.</ref><ref>Edwards TB, Boulahia A, Walch G. Radiographic analysis of bone defects in chronic anterior shoulder instability. Arthroscopy 2003;19:732-9.</ref>
[[File:1562527520975-lg.jpg|thumb|600x600px|A) Sagittal view of a CT arthrogram of a left shoulder demonstrates a significant Bankart fracture (white arrow) that produces an “inverted-pear” glenoid. B) Plain anteroposterior radiograph reveals an anteroinferior glenohumeral dislocation with an “engaged” Malgaigne (Hill-Sachs) lesion of the humerus.|alt=]]
Given that the average glenoid diameter is about 24 mm, a 6 mm-wide or larger fragment of the glenoid will typically equate to a 25% or more of the articular surface and is considered a large bony fragment.<ref name=":4">Burkhart SS, De Beer JF. Traumatic glenohumeral bone defects and their relationship to failure of arthroscopic Bankart repairs: significance of the inverted-pear glenoid and the humeral engaging Hill-Sachs lesion. Arthroscopy 2000;16:677-94.</ref><ref>Burkhart SS, Debeer JF, Tehrany AM, Parten PM. Quantifying glenoid bone loss arthroscopically in shoulder instability. Arthroscopy 2002;18:488-91.</ref>

Such significant glenoid bone loss can be viewed arthroscopically as an inverted pear configuration. All Malgaigne lesions are by definition engaging lesions (since it has engaged at least once). Thus, the notion of “engaging” versus “non-engaging” can lead to significant confusion. Some have proposed that the important lesions are those that engage in the 90-90 position.

Finally, the active restraint, mainly a lesion of the rotator cuff above the age of 40, will complete this complex situation.<ref name=":5">Antonio GE, Griffith JF, Yu AB, Yung PS, Chan KM, Ahuja AT. First-time shoulder dislocation: High prevalence of labral injury and age-related differences revealed by MR arthrography. JMRI 2007;26:983-91.</ref><ref>Itoi E, Tabata S. Rotator cuff tears in anterior dislocation of the shoulder. Int orthop 1992;16:240-4.</ref>

The glenohumeral joint is stabilized by a so-called “concavity compression” principle with the rotator cuff pulling the humeral head into the glenoid concavity and therefore ensuring stability through counteracting decentering translational forces.<ref>Lazarus MD, Sidles JA, Harryman DT, 2nd, Matsen FA, 3rd. Effect of a chondral-labral defect on glenoid concavity and glenohumeral stability. A cadaveric model. J Bone Joint Surg Am 1996;78:94-102.</ref><ref>Matsen FA, 3rd, Harryman DT, 2nd, Sidles JA. Mechanics of glenohumeral instability. Clinics in sports medicine 1991;10:783-8.</ref><ref>Yamamoto A, Takagishi K, Osawa T, Yanagawa T, Nakajima D, Shitara H, Kobayashi T. Prevalence and risk factors of a rotator cuff tear in the general population. J Shoulder Elbow Surg 2010;19:116-20.</ref>

==Natural History and Risk Factors of Dislocation or Recurrences==
To understand the natural history of instability and its importance for the appropriate management of this pathology, the following questions should be answered: What happens in the shoulder after the first dislocation? Which structures suffer damage? Who are the patients at higher risk of recurrence? How does the disease evolve without treatment? Will surgical treatment avoid future negative outcomes and prevent degenerative joint disease? Who should we treat and when?<ref>Carpinteiro EP, Barros AA. Natural History of Anterior Shoulder Instability. Open Orthop J. 2017 Aug 31;11:909-918.</ref>

80% of anterior-inferior dislocations occur in young patients. Recurrent instability is common and multiple dislocations are the rule. Instability is influenced by a large number of variables, including age of onset, activity profile, number of episodes,delay between first episode and surgical treatment. The different risks factors are:

-Young males (up to 100% of recurrence),<ref name=":6">Postacchini F, Gumina S, Cinotti G. Anterior shoulder dislocation in adolescents. J Shoulder Elbow Surg 2000;9:470-4.</ref><ref name=":7">Hovelius L, Augustini BG, Fredin H, Johansson O, Norlin R, Thorling J. Primary anterior dislocation of the shoulder in young patients. A ten-year prospective study. J Bone Joint Surg Am 1996;78:1677-84.</ref>

-Practice of contact sports, forced overhead activity,

-Sport practice at a competitive level,<ref name=":8">Balg F, Boileau P. The instability severity index score. A simple pre-operative score to select patients for arthroscopic or open shoulder stabilisation. J Bone Joint Surg Br 2007;89:1470-7.</ref>

-Bony impairment,

-Concomitant hyperlaxity.<ref>Habermeyer P, Jung D, Ebert T. [Treatment strategy in first traumatic anterior dislocation of the shoulder. Plea for a multi-stage concept of preventive initial management]. Der Unfallchirurg 1998;101:328-41.</ref>

==Classification==
Instability can be classified as primary or recurrent. The latter can be further classified as dislocation, subluxation, apprehension, or an unstable painful shoulder. In frank dislocation, the articular surfaced of the joint are completely separated. Subluxation is defined as symptomatic translation of the humeral head on the glenoid without complete separation of the articular surfaces. Apprehension is classically defined by fear of imminent dislocation in the 90-90 position. This could correspond to an instability phenomena or a persistent fear after a successful glenohumeral stabilization (please refer to Apprehension chapter).<ref name=":9">Haller S, Cunningham G, Laedermann A, Hofmeister J, Van De Ville D, Lovblad KO, Hoffmeyer P. Shoulder apprehension impacts large-scale functional brain networks. AJNR American journal of neuroradiology 2014;35:691-7.</ref>

The unstable painful shoulder presents as pain only (as opposed to a sense of instability) during an apprehension maneuver at clinical examination.<ref name=":10">Boileau P, Zumstein M, Balg F, Penington S, Bicknell RT. The unstable painful shoulder (UPS) as a cause of pain from unrecognized anteroinferior instability in the young athlete. J Shoulder Elbow Surg 2011;20:98-106.</ref><ref name=":11">Patte D, Bernageau J, Rodineau J, Gardes JC. [Unstable painful shoulders (author's transl)]. Rev Chir Orthop Reparatrice Appar Mot 1980;66:157-65.</ref>

The majority of these patients has a history of trauma, but simply do not report a clear history of trauma. Careful preoperative and/or arthroscopic examination will show that the majority of these patients also has evidence of instability (i.e. labral tear, glenoid fracture, or Malgaigne (Hill-Sachs) lesion)

Five types of traumatic anterior dislocation have been described. The subcoracoid dislocation has an antero-inferior direction and is the most common. Other types, including subglenoid, subclavicular, retroperitoneal, and intrathoracic are rare and usually associated with severe trauma.<ref>Patel MR, Pardee ML, Singerman RC. Intrathoracic Dislocation of the Head of the Humerus. J Bone Joint Surg Am 1963;45:1712-4.</ref><ref>Wirth MA, Jensen KL, Agarwal A, Curtis RJ, Rockwood CA, Jr. Fracture-dislocation of the proximal part of the humerus with retroperitoneal displacement of the humeral head. A case report. J Bone Joint Surg Am 1997;79:763-6.</ref>

Osseous defects of the anterior glenoid rim can be classified into three types according to their pathomorphology. In particular, acute (type I) and chronic glenoid rim defects (type II and III) are differentiated, which are provoked either by an acute glenoid fracture or recurrent shoulder dislocations with subsequent erosion of the glenoid rim. Type I lesions are further divided into bony Bankart lesions (type Ia), solitary glenoid rim fractures (type Ib) and multifragmented glenoid rim fractures (type Ic). In most cases, type I glenoid defects can sufficiently be reconstructed by mobilization and anatomical refixation of the fragment.

In cases of complex multifragmented glenoid rim fractures (type Ic), however, it may be necessary to resect the fragments and augment the glenoid defect. Type II defects include chronic fragment-type of lesions that are characterized by an extra-anatomically consolidated or pseudarthrotic fragment of insufficient dimensions for a defect reconstruction due to resorption processes. A bony glenoid augmentation may be indicated, depending on the dimensions of the glenoid defect and the remaining fragment. Erosion-type of defects (type III) are predominantly observed in patients with recurrent anterior shoulder dislocations. These usually develop on the basis of a glenoid fracture with subsequent resorption of the fragment, or as a result of chronic abrasion of the anterior glenoid rim. If the bone loss adopts substantial dimensions, mere soft-tissue stabilization procedures are not sufficient in re-establishing stability.

==Clinical Presentation and Essential Physical Examination==
The history should document age, hand dominance, occupation, participation in sporting activities, initial mechanism of the injury, the position of the arm (extension, abduction, and external rotation favors anterior dislocation), how long the shoulder stays out, the method of reduction, the number of recurrences (frank dislocation vs subluxation), and the effectiveness of a previous nonoperative or operative treatment. The diagnosis of recurrent traumatic anterior glenohumeral instability is usually made easily on the basis of the history, radiographs, and a positive apprehension sign. However, when collision athletes are seen, care should be taken because they may not experience clear dislocation or subluxation and only complain of pain or weakness.

A comprehensive physical examination is essential. The aim is to define the direction of instability, the presence of an associated pathologic hyperlaxity, and to exclude neurological and rotator cuff impairment. Passive and active glenohumeral range of motion should be assessed. Rotator cuff examination includes strength tests such as belly-press, bear hug, Jobe tests and strength in external rotation against resistance (please refer to Rotator Cuff Pathology/Rotator cuff complete lesion). Tests for anterior and superior labral lesions are not systematically performed as they have a poor sensitivity and specificity.<ref>Cook C, Beaty S, Kissenberth MJ, Siffri P, Pill SG, Hawkins RJ. Diagnostic accuracy of five orthopedic clinical tests for diagnosis of superior labrum anterior posterior (SLAP) lesions. J Shoulder Elbow Surg 2012;21:13-22.</ref>

The neurovascular status of the upper extremity is assessed, particularly with regard to the axillary nerve since there is a high incidence of injury to this nerve with traumatic instability (Figure).
[[File:1562529745788-lg.jpg|thumb|600x600px|A) A 54-year-old patient sustained a fracture dislocation of the right shoulder. At clinical examination, no peripheral pulse was palpated. B) During open reduction, the axillary artery (white arrows) was found kinked around the fractured humeral head.|alt=|border]]
Laxity is a normal, physiologic and asymptomatic finding, that corresponds to translation of the humeral head in any direction to the glenoid.<ref>Gerber C, Terrier F, Ganz R. The Trillat procedure for recurrent anterior instability of the shoulder. J Bone Joint Surg Br 1988;70:130-4.</ref>

Laxity is assessed with the sulcus sign, anterior-posterior drawer, hyperabduction tests, and external rotation elbow at side. The two former tests are only qualitative and are not routinely performed by the authors. Hyperlaxity is constitutional, multidirectional, bilateral and asymptomatic. Hyperlaxity of the shoulder is probably best defined as external rotation elbow at the side equal or greater than 85 degrees.<ref>Walch G, Agostini JY, Levigne C, Nove-Josserand L. [Recurrent anterior and multidirectional instability of the shoulder]. Rev Chir Orthop Reparatrice Appar Mot 1995;81:682-90.</ref>

This non-pathological finding is a risk factor for instability but does not by itself demand treatment unless there is clear pathological laxity. Pathological laxity of the inferior glenohumeral ligament is observed when passive abduction in neutral rotation in the glenohumeral joint is above 105 degrees, there is apprehension above 90 degrees of abduction, or if a difference of more than 20 degrees between the two shoulders is noted.<ref>Gagey OJ, Gagey N. The hyperabduction test. J Bone Joint Surg Br 2001;83:69-74.</ref><ref name="HoveliusRahme2016Primary">Hovelius L, Rahme H. Primary anterior dislocation of the shoulder: long-term prognosis at the age of 40 years or younger. Knee Surg Sports Traumatol Arthrosc 2016;24:330-42.</ref>

For apprehension the patient is initially invited to demonstrate his or her functional problem to the examiner (no-touch examination). This examination alone, coupled with a good history, often provides the information needed. However, if the direction of the instability remains unclear, the apprehension (crank) test, an abducted and externally rotated position suggestive of anterior instability is performed. Fear of dislocation or a feeling of anterior pain is considered positive for damage to the anterior capsulolabral complex, which should be relieved with posterior translation of the humerus (relocation maneuver). To summarize, the physical examination demonstrates instability if the apprehension test is positive, multidirectional hyperlaxity when the external rotation at side is equal or above 85 degrees, and a pathological laxity of the inferior glenohumeral ligament if the hyperabduction test is positive.

==Apprehension==
Apprehension can be difficult to diagnose pre- or post-operatively, as it seems more complex than a pure mechanical problem of the shoulder. Although clinical definition seems to be well established, its underlying pathologic mechanism remains unclear. This may explain the wide reported range (3% to 51%) of patients with ongoing apprehension or who will avoid any shoulder movement after an open or arthroscopic stabilization, despite a clinically stable joint.<ref name="HoveliusRahme2016Primary" /><ref>Hovelius L, Vikerfors O, Olofsson A, Svensson O, Rahme H. Bristow-Latarjet and Bankart: a comparative study of shoulder stabilization in 185 shoulders during a seventeen-year follow-up. J Shoulder Elbow Surg 2011;20:1095-101.</ref><ref name=":14">Lädermann A, Lubbeke A, Stern R, Cunningham G, Bellotti V, Gazielly DF. Risk factors for dislocation arthropathy after Latarjet procedure: a long-term study. International orthopaedics 2013;37:1093-8.</ref>

Failure to recognize and adequately address this issue may result in poor outcome and lead to unnecessary surgery or even revision. Furthermore, identifying this condition may allow establishing adequately targeted rehabilitation programs.

===Definition===
An important aspect to incorporate in dislocation management is apprehension, defined as anxiety and motor resistance in patients with a history of anterior glenohumeral instability. Clinically, apprehension sign is defined as fear of imminent dislocation when placing the arm in abduction and external rotation, and should be distinct from mere pain which can be related to inflammation, stiffness and other shoulder pathologies.<ref>Jobe FW, Kvitne RS, Giangarra CE. Shoulder pain in the overhand or throwing athlete. The relationship of anterior instability and rotator cuff impingement. Orthop Rev 1989;18:963-75.</ref><ref>Rowe CR, Zarins B. Recurrent transient subluxation of the shoulder. The Journal of bone and joint surgery American volume 1981;63:863-72.</ref>

Proprioception, as defined by Charles Scott Sherrington, is the sense of the relative position of neighboring parts of the body and strength of effort being employed during movement.<ref>Sherrington C. The Integrative Action of the Nervous System. New York: Charles Scribner's Sons; 1906.</ref>

It is distinct from exteroception, by which one perceives the outside world, and interoception, by which one perceives pain, hunger, or the movement of internal organs. The brain integrates information from proprioception and from the vestibular system into its overall sense of body position, movement, and acceleration. Kinesthesia refers either to the brain's integration of proprioceptive or vestibular inputs.

===“Localization” of Apprehension===
The pathogenesis of apprehension is not fully understood. Theoretically, apprehension could be related to:

1) Brain changes induced by dislocations<ref name=":9" /><ref>Cunningham G, Zanchi D, Emmert K, Kopel R, Van De Ville D, Lädermann A, Haller S, Hoffmeyer P. Neural Correlates of Clinical Scores in Patients with Anterior Shoulder Apprehension. Medicine and science in sports and exercise 2015;47:2612-20.</ref><ref name=":15">Zanchi D, Cunningham G, Lädermann A, Ozturk M, Hoffmeyer P, Haller S. Structural white matter and functional connectivity alterations in patients with shoulder apprehension. Sci Rep 2017;7:42327.</ref><ref name=":16">Zanchi D, Cunningham G, Lädermann A, Ozturk M, Hoffmeyer P, Haller S. Brain activity in the right-frontal pole and lateral occipital cortex predicts successful post-operatory outcome after surgery for anterior glenoumeral instability. Sci Rep 2017;7:498.</ref>

2) Peripheral neuromuscular lesions consecutive to dislocation affecting proprioception<ref name=":17">Atef A, El-Tantawy A, Gad H, Hefeda M. Prevalence of associated injuries after anterior shoulder dislocation: a prospective study. International orthopaedics 2015.</ref>

3) Persistent mechanical instability consisting in micro-motion<ref name=":19">Lädermann A, Denard PJ, Tirefort J, Kolo FC, Chagué S, Cunningham G, Charbonnier C. Does surgery for instability of the shoulder truly stabilize the glenohumeral joint?: A prospective comparative cohort study. Medicine (Baltimore) 2016;95:e4369.</ref>
[[File:1562540576908-lg.jpg|center|thumb|600x600px|Apprehension may be related to (A) central nervous system sequelae, (B) peripheral neurological, muscular or capsular/ligamentous lesions consecutively to dislocation, or (C) mechanical instability as micromovements. Reproduced from Lädermann et al., with permission.]]

====Brain====
Fear, anxiety and anticipation of situations that could lead to a dislocation are essential cognitive processes in shoulder apprehension. Functional magnetic resonance imaging (fMRI) measures brain activity by detecting changes associated with blood flow.<ref>Logothetis NK, Pauls J, Augath M, Trinath T, Oeltermann A. Neurophysiological investigation of the basis of the fMRI signal. Nature 2001;412:150-7.</ref>

When exploring neuronal connections and cerebral changes induced by shoulder dislocation, research revealed that several cerebral areas are modified, representing the different aspects of shoulder apprehension. Specific reorganizations are found in apprehension-related functional connectivity of the primary sensory-motor areas (motor resistance), dorsolateral prefrontal cortex (cognitive control of motor behavior), and the dorsal anterior cingulate cortex/dorsomedial prefrontal cortex and anterior insula (anxiety and emotional regulation) (Figure).<ref name=":9" />
[[File:1562542592373-lg.gif|center|thumb|450x450px|Patients vs control participants had a significantly (P < .05 corrected) higher task-correlated functional connectivity in two almost mirror symmetric components. Reproduced from Haller et al., with permission.]]
 Those regions are involved in the cognitive control of motor behavior. Hence, there is motor control anticipation and muscular resistance (protective reflex mechanism), in order to avoid shoulder movement that could lead to dislocation.<ref>Cieslik EC, Zilles K, Caspers S, et al. Is there "one" DLPFC in cognitive action control? Evidence for heterogeneity from co-activation-based parcellation. Cereb Cortex 2013;23:2677-89.</ref>

Fractional anisotropy, representing white matter integrity, is increased in the left internal capsule and partially in the thalamus in patients compared to healthy controls. Fractional anisotropy correlated positively with pain visual analog scale (VAS) scores (p < .05) and negatively with simple shoulder test (SST) scores (p < .05).<ref name=":15" />

This suggests an abnormal increased axonal integrity and therefore pathological structural plasticity due to the over-connection of white matter fibers in the motor pathway. These structural alterations affect several dimensions of shoulder apprehension as pain perception and performance in daily life.

Shoulder stabilization could allow the brain to partially “recover”. Patients with shoulder apprehension underwent clinical and functional magnetic resonance imaging (fMRI) examination before and one year after shoulder stabilization surgery. Clinical examination showed a significant improvement in postoperative shoulder function compared with preoperative. Coherently, results showed decreased activation in the left pre-motor cortex postoperatively, demonstrating that stabilization surgery induced improvements both at the physical and at the brain level, one year postoperatively (Figure 9). Most interestingly, right–frontal pole and right-occipital cortex activity is associated with good outcome in shoulder performance.<ref name=":16" />
[[File:1562542592786-lg.gif|center|thumb|400x400px|Task related General Linear Model (GLM) shows higher activation in baseline vs. follow-up for apprehension videos vs. control videos, representing partial brain healing. Reproduced from Zanchi et al., with permission.]]

====Peripheral Neuromuscular Lesion====
During a traumatic dislocation, there are a disruption of the shoulder tendinomuscular (in 10% of cases) and peripheral nerve lesions (in 14% of cases).<ref>Robinson CM, Shur N, Sharpe T, Ray A, Murray IR. Injuries associated with traumatic anterior glenohumeral dislocations. J Bone Joint Surg Am 2012;94:18-26.</ref>

However, this does not account for subclinical neurologic damage that may be much more preponderant. Capsuligamentous structures surrounding the glenohumeral joint are richly innervated with proprioceptors and therefore play an important sensorimotor role in addition to their primary mechanical stabilizising function. Thus, when considering the extensive and frequent damage to these structures after shoulder dislocation (Figure), there is bound to be an important loss in glenohumeral proprioception.<ref name=":5" /><ref name=":17" />

The latter plays a significant role in stabilization of a normal healthy shoulder and after any shoulder injury by contributing to motor control.<ref name=":18">Fyhr C, Gustavsson L, Wassinger C, Sole G. The effects of shoulder injury on kinaesthesia: a systematic review and meta-analysis. Man Ther 2015;20:28-37.</ref>
[[File:1562542594443-lg.jpg|center|thumb|600x600px|Arthroscopic view of a left shoulder through a posterior portal. This patient has sustained more than 50 subluxations. The axillary nerve is clearly identifiable (white asterisk). There is no more capsule or inferior glenohumeral ligament, and the subscapularis muscle is hardly recognizable. Reproduced from Lädermann A, Benchouk S, Denard P. Traumatic Anterior Shoulder Instability: General concepts & proper management. In: Park J, ed. Sports Injuries to the Shoulder and Elbow. Berlin Heidelberg: Springer-Verlag; 2015, with permission.]]
Surgical stabilization has been shown to help proper healing of these structures and thus restoring proprioception of the glenohumeral joint.<ref>Myers JB, Lephart SM. Sensorimotor deficits contributing to glenohumeral instability. Clin Orthop Relat Res 2002:98-104.</ref>

====Glenohumeral Joint====
The third etiologic factor for apprehension is persistent micro-motion in the glenohumeral joint despite a clinically stable shoulder, satisfactory radiographic results, and no new episode of subluxation or dislocation. Shoulder dislocation causes damage to the capsuloligamentous complex in 52% of the cases, and the glenoid labrum in 73% of the cases.<ref>Liavaag S, Stiris MG, Svenningsen S, Enger M, Pripp AH, Brox JI. Capsular lesions with glenohumeral ligament injuries in patients with primary shoulder dislocation: magnetic resonance imaging and magnetic resonance arthrography evaluation. Scandinavian journal of medicine & science in sports 2011;21:e291-7.</ref><ref name=":5" />

The plastic deformation of these structures becomes progressively worse with subsequent episodes.The plastic deformation of these structures becomes progressively worse with subsequent episodes. In addition to progressive soft tissue injury, recurrent dislocations induce bony lesions, which may involve the glenoid (bony Bankart), the posterolateral humeral head (Malgaine), or both. Severity of apprehension, quantified as the moment at which it appears during the course of abduction and external rotation, seems to be correlated to the extent of bone loss. Capsular redundancy has also been recognized as a risk factor for ongoing apprehension after surgical stabilization and Ropars et al. found a significantly decreased apprehension in patients with associated capsulorraphy to Latarjet procedures, compared with patients with Latarjet and no capsular reconstruction.<ref name=":12">Ropars M, Cretual A, Kaila R, Bonan I, Herve A, Thomazeau H. Diagnosis and treatment of anteroinferior capsular redundancy associated with anterior shoulder instability using an open Latarjet procedure and capsulorrhaphy. Knee Surg Sports Traumatol Arthrosc 2016;24:3756-64.</ref>

However, these changes may be very subtle and therefore not detectable on standard clinical magnetic resonance imaging in neutral position. This has been described by Patte et al. in non-operated patients and popularized under the name of "unstable painful shoulder".<ref name=":11" /><ref name=":10" />

This micro-motion may yet still be present after surgical stabilization. Shoulder stabilization may thus only prevent new episodes of dislocation, rather than actually truly stabilizing the shoulder.<ref>Singer GC, Kirkland PM, Emery RJ. Coracoid transposition for recurrent anterior instability of the shoulder. A 20-year follow-up study. J Bone Joint Surg Br 1995;77:73-6.</ref><ref>Lädermann A, Tirefort J, Zanchi D, Haller S, Charbonnier C, Cunningham G. Shoulder Apprehension: a Multifactorial Approach. EFORT Open Rev. 2018 24;3(10):550-557</ref>

A study described glenohumeral translation in patients with traumatic anteroinferior instability and subsequently analyzed the effect of glenohumeral stabilization on this translation. For all movements, the authors recorded humeral head position of the contralateral and ipsilateral shoulders in relation to the glenoid center pre- and 1 year post-operatively. They observed an anterior translation of the humeral head (Figure), especially during flexion and abduction movements (p < .05 and p < .05, respectively). One year after surgery, all patients had a clinically stable shoulder and none presented with a new episode of dislocation or subluxation.

However, anterior translation of the humeral head was not significantly reduced and remained close to preoperative values confirming that shoulder stabilization does not stabilize the shoulder but uniquely prevents further dislocation. These findings have several important implications. First, it may explain residual pain, apprehension, and impossibility to return to sport at the same level as reported in other studies. Second, persistent abnormal motion between the glenoid and the humeral head might be the underlying cause of dislocation arthropathy that is observed with a prevalence of 36%. Repeated sliding of the humeral head against the glenoid associated with degenerative changes of cartilage properties and decreased biological healing potential related to aging, could lead to a vicious circle of extensive cartilage damage.<ref name=":19" />
[[File:1562542595262-lg.jpg|center|thumb|600x600px|(A) Abduction simulation obtained from shoulder’s CT reconstruction and optical motion capture, (B) and (C) show a zoom in the shoulder (front and top views). In image (C), we clearly observe an anterior translation (arrow) of the humeral head center (pink sphere) with respect to the glenoid center (white sphere). Note that the clavicle is not shown for clarity. Reproduced from Lädermann et al., with permission.]]
 

==Scores==

===Single Assessment Numeric Evaluation (SANE)-instability score===
A modified Single Assessment Numeric Evaluation (SANE) score specific to shoulder instability, the SANE-instability score, has been developed.<ref name=":0">Lädermann A, Denard PJ, Collin P, Mohamed Ibrahim M, Bothorel H, Chiu JC. Single Assessment Numeric Evaluation for instability as an alternative to the Rowe score. J Shoulder Elbow Surg. 2020;S1058-2746(20)30686-8</ref> The SANE-instability score (100 points) is assessed with a single question: “What is the overall percent value of your shoulder if a completely stable shoulder represents 100%?” A high correlation between the Rowe and SANE-instability scores for shoulder instability has been found before and after treatment, as well as for different patient age groups and treatment types. This score is easy to collect and use because it can be collected in the office or remotely, thereby saving considerable time and potentially improving compliance.<ref name=":0" />

===Rowe===
The 1978 Rowe score is calculated with the 3 following items: stability (50 points), motion (20 points), and function (30 points).<ref>Rowe CR, Patel D, Southmayd WW. The Bankart procedure: a long-term end-result study. J Bone Joint Surg Am. 1978; 60: 1-16</ref>

===Walch-Duplay===
This subsection does not exist. You can ask for it to be created, but consider checking the search results below to see whether the topic is already covered.

===WOSI===
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===ISIS===
Boileau et al. proposed a simple 10-point scale scoring system (instability severity index score (ISIS)) based on factors derived from a pre-operative questionnaire, physical examination, and anteroposterior radiographs to determine the risk of treatment failure following isolated arthroscopic Bankart repair (Table). In this model an ISIS of 3 or less was associated with a 5% rate of recurrence, an ISIS of 4 to 6 was associated with a 10% rate of recurrence, and an ISIS over 6 was associated with a 70% rate of recurrence. Although it has imperfections, this score, validated since, has merit to easily remind the clinician of factors that are important to consider when evaluating a patient.<ref name=":8" /><ref>Rouleau DM, Hebert-Davies J, Djahangiri A, Godbout V, Pelet S, Balg F. Validation of the instability shoulder index score in a multicenter reliability study in 114 consecutive cases. Am J Sports Med 2013;41:278-82.</ref>

'''''Table: The instability severity index score is based on a pre-operative questionnaire, clinical examination, and radiographs.'''''
[[File:1562543299662-lg.jpg|center|thumb|899x899px|Figure. 12 * AP, anteroposterior]]
 

==Essential Radiology==
Radiographic evaluation is based on whether the dislocation is acute or chronic.

===Acute Dislocation===
Three views plain radiographs, including true anteroposterior of the glenohumeral joint, scapular Y (scapular lateral), and Velpeau axillary views are the mainstay of imaging in the setting of traumatic anterior instability.<ref>Bloom MH, Obata WG. Diagnosis of posterior dislocation of the shoulder with use of Velpeau axillary and angle-up roentgenographic views. J Bone Joint Surg Am 1967;49:943-9.</ref>

The latter view is crucial to obtain, as the two first alone do not allowed to exclude a dislocation. The goal is to confirm the direction of dislocation and to evaluate associated lesions. One reduced, further imaging studies in the setting of an associated fracture (computed tomography (CT)), suspicion of rotator cuff injury (ultrasonography or magnetic resonance imaging (MRI)), or vascular impairment (injected CT) may be warranted.

===Preoperative Planning in Case of Recurrent Dislocation===
The first step is to analyze, if available, plan radiographs with the shoulder out of joint to confirm the direction of instability. Plain radiographs including anteroposterior in neutral, internal and external rotations, scapular Y and Bernageau views are then obtained.<ref>Bernageau J, Patte D, Debeyre J, Ferrane J. [Value of the glenoid profile in recurrent luxations of the shoulder]. Rev Chir Orthop Reparatrice Appar Mot 1976;62:142–7.</ref>

Bone loss, static instability, post-dislocation arthropathy, and coracoid non-union (if a Latarjet or a Bristow procedures are planned) have to be estimated. Magnetic resonance imaging (MRI) arthrogram is useful to assess for soft tissue such as an anterior labral tear (Figure). 
[[File:1562543301909-lg.jpg|center|thumb|600x600px|Coronal T1 SPIR magnetic resonance imaging (MRI) of a right shoulder showing disruption of the anteroinferior glenoid labrum. B]]
Associated intra-articular pathology such as SLAP, HAGL, and rotator cuff lesions or a paralabral cyst are also assessed (Figure).

The evaluation is completed by a 3D computed tomography arthrogram in the setting of recurrent instability in which there is primary concern for bone loss. The extent of both glenoid bone loss and Hill-Sachs lesions are best assessed by computed tomography scan and are used to determine the need for a bony procedure as opposed to arthroscopic Bankart repair (Figures).
[[File:1562543901744-lg.jpg|center|thumb|600x600px|A) Sagittal view of a CT arthrogram of a left shoulder demonstrates a significant Bankart fracture that produces an “inverted-pear” glenoid. B) Plain anteroposterior radiograph reveals an anteroinferior glenohumeral dislocation with an “engaged” Malgaigne (Hill-Sachs) lesion of the humerus.]]
 
[[File:1562544592047-lg.jpg|center|thumb|600x600px|Axial computed tomography (CT) arthrogram view showing a large Malgaigne lesion.]]
 

==Treatments==
The degree, nature and combination of injuries induced by traumatic glenohumeral instability are highly variable. Damage to the bony and soft tissue stabilizers of the shoulder, as well as neurologic impairment, must be detected and analyzed in order to provide the patient with the most adequate treatment option. This new knowledge should be applied to rehabilitation therapy and surgical stabilization techniques. As the current stabilization techniques do not seem to prevent residual glenohumeral micro-motion, it remains to be determined which factors help to minimize this phenomenon, whether it is, the increase in the anteroposterior diameter of the glenoid with a bone graft, the sling effect provided by the conjoined tendon or the long head of the biceps, the capsulorraphy, the repaired labrum or the remplissage.<ref>Lädermann A, Bohm E, Tay E, Scheibel M. Bone-mediated anteroinferior glenohumeral instability : Current concepts. Der Orthopade 2018.</ref><ref name=":13">Collin P, Lädermann A. Dynamic Anterior Stabilization Using the Long Head of the Biceps for Anteroinferior Glenohumeral Instability. Arthrosc Tech 2018;7:e39-e44.</ref><ref>Young AA, Maia R, Berhouet J, Walch G. Open Latarjet procedure for management of bone loss in anterior instability of the glenohumeral joint. J Shoulder Elbow Surg 2011;20:S61-9.</ref><ref name=":12" />

===Methods of Reduction===
Around 400 BC, Hippocrates, the father of Western medicine, introduced the traction method to reduce the shoulder. The patient lay supine whilst the physician standing on the patient's affected side held the arm and applied traction. The stockinged foot of the physician placed in the axilla served as counter traction. This technique was detailed in the Hippocratic Corpus, and as it remained the primary medical text for centuries so did the method. Similar technique of reduction was re-introduced in the 1870 as a painless technique by Theodor Kocher, but is now obsolete because of the likelihood of serious complications.<ref>Kocher E. Eine neue Reductionsmethode für Schulterverrenkung. Berlin Klin 1870;7:101-5.</ref>

===Conservative (Nonoperative) Treatment===
Heading towards a better understanding of the complex and multifactorial origins of glenohumeral instability and apprehension, postoperative management may in turn also be improved, notably in challenging cases of patients with persistent apprehension, despite a clinically stable shoulder. Knowing that shoulder apprehension could be the result of ongoing cerebral abnormalities or residual micro-motion may avoid costly series of onerous investigations, useless physiotherapy sessions or even re-operations. Furthermore, this perspective offers a new angle of a therapeutic approach that differs from conventional manual rehabilitation methods centered on the glenohumeral joint itself. If persistent apprehension or micro-motion is detected, growing research evidence supports the use of a multidisciplinary approach including:

1) A "reafferentation" (reconveying and connecting the neurological peripheral input to the cortex)89 of the shoulder particularly focused on proprioceptive work,69 which has been proved to lead to superior neuromuscular control than strengthening alone.<ref>Horvat JC. [Reconstruction of the spinal cord and its motor connections using embryonal nervous tissue transplantation and peripheral nerve autotransplantation. A study in the adult rat]. Neurochirurgie 1991;37:303-11.</ref><ref>Salles JI, Velasques B, Cossich V, Nicoliche E, Ribeiro P, Amaral MV, Motta G. Strength training and shoulder proprioception. J Athl Train 2015;50:277-80.</ref><ref name=":18" />

2) A biofeedback therapy where the patient directly visualizes his abnormal response to a negative stimulus on fMRI or electroencephalogram, and can thereby actively correct it. This treatment modality has already shown to improve shoulder control and performance in various settings.<ref>deCharms RC, Maeda F, Glover GH, Ludlow D, Pauly JM, Soneji D, Gabrieli JD, Mackey SC. Control over brain activation and pain learned by using real-time functional MRI. Proceedings of the National Academy of Sciences of the United States of America 2005;102:18626-31.</ref><ref>Antunes A, Carnide F, Matias R. Real-time kinematic biofeedback improves scapulothoracic control and performance during scapular-focused exercises: A single-blind randomized controlled laboratory study. Hum Mov Sci 2016;48:44-53.</ref><ref>Huang HY, Lin JJ, Guo YL, Wang WT, Chen YJ. EMG biofeedback effectiveness to alter muscle activity pattern and scapular kinematics in subjects with and without shoulder impingement. J Electromyogr Kinesiol 2013;23:267-74.</ref>

3) A cognitive behavioral approach to decondition this pathological residual apprehension by making them realize residual apprehension does not necessarily lead to recurrent instability with gradual exposition that has already shown successful results in the treatment of kinesiophobia,94-96 a condition based on a re-injury fear-avoidance model initially described in low-back pain,97 further popularized in sports medicine98 and various upper limb conditions.<ref>Das De S, Vranceanu AM, Ring DC. Contribution of kinesophobia and catastrophic thinking to upper-extremity-specific disability. J Bone Joint Surg Am 2013;95:76-81.</ref>

4) Electric stimulation of hypoactive rotator cuff and periscapular muscles.<ref>Moroder P, Minkus M, Bohm E, Danzinger V, Gerhardt C, Scheibel M. Use of shoulder pacemaker for treatment of functional shoulder instability: Proof of concept. Obere Extrem 2017;12:103-8.</ref>

===Treatment of Acute First Traumatic Dislocations===
The first step, whenever possible, is to obtain a complete set of radiographs before attempting a reduction. This will allow an assessment of the type of dislocation and associated bone injuries. Attempting to reduce a fracture dislocation can have troublesome clinical and legal consequences (Figure).
[[File:1562546209492-lg.jpg|center|thumb|600x600px|A) An anteroposterior plain radiograph of a left shoulder shows an anterior dislocation with a nondisplaced humeral neck fracture on the prereduction radiographs. B) Radiographs after attempting a closed reduction without adequate muscle relaxation reveal displacement of the fracture with the humeral head remaining anteriorly.]]
Exceptions are an impossibility to have reasonably fast access to radiology or a patient with neurological impairment. Because of the possible association of nerve injuries and, to a lesser extent, vascular injuries (Figure), an essential part of the physical examination is an assessment of the neurovascular status of the upper extremity before reduction.<ref>de Laat EA, Visser CP, Coene LN, Pahlplatz PV, Tavy DL. Nerve lesions in primary shoulder dislocations and humeral neck fractures. A prospective clinical and EMG study. J Bone Joint Surg Br 1994;76:381-3.</ref><ref>Brown FW, Navigato WJ. Rupture of the axillary artery and brachial plexus palsy associated with anterior dislocation of the shoulder. Report of a case with successful vascular repair. Clin Orthop Relat Res 1968;60:195-9.</ref>
[[File:1562529745788-lg.jpg|center|thumb|600x600px|A) A 54-year-old patient sustained a fracture dislocation of the right shoulder. At clinical examination, no peripheral pulse was palpated. B) During open reduction, the axillary artery (white arrows) was found kinked around the fractured humeral head.]]
They are numerus appropriate methods of reduction that have been described. The second step is to use the technique of closed reduction which is mastered by the doctor who will perform the maneuver. The glenohumeral joint should be reduced as gently and expeditiously as possible. In the case of fracture dislocation, the reduction is best performed under general anesthesia to have adequate muscle relaxation. After reducing the dislocation, plain radiographs are obtained to verify the adequacy of the reduction.

Results concerning conservative treatment are still debatable. A stable shoulder is obtained at ten years in only half of patients with conservative treatment.<ref name=":7" />

However, recurrence rate is highly dependent on age and activity of the patient; studies have reported a 72% to 95% recurrence in patients under 20 years of age, and 70% to 82% recurrence between the ages of 20 and 30 years, and only 30% in those over 30 years of age.<ref>te Slaa RL, Brand R, Marti RK. A prospective arthroscopic study of acute first-time anterior shoulder dislocation in the young: a five-year follow-up study. J Shoulder Elbow Surg 2003;12:529-34.</ref><ref name=":6" /><ref>Robinson CM, Howes J, Murdoch H, Will E, Graham C. Functional outcome and risk of recurrent instability after primary traumatic anterior shoulder dislocation in young patients. J Bone Joint Surg Am 2006;88:2326-36.</ref>

Many patients above the age of 30 would consequently undergo unnecessary surgery if proposed after the first dislocation. Conservative treatment after the first traumatic anterior dislocation may be thus recommended for patients who are not actively engaged in sports, above the age of 30 years old, with a low functional demand, with an associated humeral fracture, or for the athlete with an in-season shoulder dislocation. For the latter situation, athletes are allowed to attempt to return to competition provided there is enough time left in the season to permit adequate rehabilitation with progression to sport-specific drills.

Rehabilitation, including return of range of motion and strengthening of dynamic stabilizers may facilitate return to sport within several weeks. Motion-limiting braces that prevent extreme shoulder abduction, extension, and external rotation are often prescribed as it may reduce the risk of recurrence. However, such braces are not well-tolerated in patients who must complete certain overhead tasks such as throwing. Moreover, a second in-season shoulder dislocation should lead to removal from sport and proceeding with stabilization so as to avoid further glenohumeral damage.

A number of studies have compared nonoperative treatment and arthroscopic stabilization. Overall, these studies report a sevenfold reduction in the risk of recurrent instability after arthroscopic stabilization, when compared with nonoperative treatment for the first-time dislocator.<ref>Murray IR, Ahmed I, White NJ, Robinson CM. Traumatic anterior shoulder instability in the athlete. Scandinavian journal of medicine & science in sports 2013;23:387-405.</ref>

A Cochrane review concluded that early surgical intervention is warranted in young adults aged less than 30 years engaged in highly demanding physical activities.<ref>Handoll HH, Almaiyah MA, Rangan A. Surgical versus non-surgical treatment for acute anterior shoulder dislocation. The Cochrane database of systematic reviews 2004:CD004325</ref>

Consequently, for patients who are actively engaging in a collision or contact or overhead sport, who risk their life in case a new dislocation (e.g. firemen, proponents of extreme sports like base jumping, and climbing), with associated static anterior subluxation, an interposed tissue or a nonconcentric reduction, or patients with rotator cuff avulsion, conservative measures are usually inadequate and prompt surgery is indicated.

===Surgical (Operative) Treatment===
Recurrent dislocation is not trivial. Each episode creates new lesions and increases the risk of developing dislocation arthropathy. The concept of early operative surgical management of the first-time dislocator has consequently been introduced to address the high recurrence rate in the young athletic population. Surgery should be proposed, as having the ultimate aim to achieve a pain-free stable shoulder while preserving range of motion. The surgical approach is based on the extent of bone loss and patient-specific risk factors for recurrence.

====Soft tissue procedures====
=====Bankart and Associate Repairs=====
The aim of a Bankart repair is to restore anatomy by reattaching the labrum to the glenoid (Figure) and tighten the inferior glenohumeral ligament by shifting from inferior to superior. Several technical factors are also important to success. It is important to place anchors at the margin of the articular surface (as opposed to the glenoid neck) to allow recreation of the labral bumper. The surgeon must be sure to obtain a proper inferior to superior shift of the capsule (Neer’s modification). Although this surgery can be performed in an open manner, the advantage of an arthroscopic approach is that it preserves the subscapularis and allows assessment of associated pathology. The literature demonstrates that patients with low risk of recurrence will benefit from either an anatomic open or arthroscopic repair with an acceptable rate of recurrence.<ref>Harris JD, Gupta AK, Mall NA, Abrams GD, McCormick FM, Cole BJ, Bach BR Jr, Romeo AA, Verma NN. Long-term outcomes after Bankart shoulder stabilization. Arthroscopy 2013;29:920-33.</ref>
[[File:1562546210935-lg.jpg|center|thumb|600x600px|Illustration of a Bankart repair (sagittal view of a right shoulder). Courtesy of Gilles Walch.]]

HAGL (Humeral Avulsion of the Glenohumeral Ligaments) lesions are uncommon causes of anterior instability. There are 3 variants of HAGL lesions: 1. Avulsion from bone 2. Capsular split 3. Combined bone avulsion and capsular split. These lesions can be addressed by repair or more easily by a Latarjet.

=====Remplissage=====
Remplissage has been described by Connoly and may be used as an adjunct to arthroscopic Bankart repair in the setting a of large Malgaigne (Hill-Sachs) lesion with glenoid bone loss of <25%.<ref>Connoly J. Humeral head defects associated with shoulder dislocations. American Academy of Orthopaedic Surgeons Instructional course lectures: Mosby; 1972:42-54.</ref>

This technique consists of a posterior capsulodesis and infraspinatus tenodesis that fills the Malgaigne lesion. The purpose is to render the Malgaigne lesion extra-capsular, avoiding its engagement. Wolf et al. and Boileau et al. presented encouraging mid- to long-term results of arthroscopic remplissage and concomitant anterior Bankart repair.<ref name=":20">Boileau P, O'Shea K, Vargas P, Pinedo M, Old J, Zumstein M. Anatomical and functional results after arthroscopic Hill-Sachs remplissage. J Bone Joint Surg Am 2012;94:618-26.</ref><ref name=":21">Wolf EM, Arianjam A. Hill-Sachs remplissage, an arthroscopic solution for the engaging Hill-Sachs lesion: 2- to 10-year follow-up and incidence of recurrence. J Shoulder Elbow Surg 2014;23:814-20.</ref>

Surgical Technique
The arthroscope can typically remain in the posterior portal because the 70 degrees angle enhances appropriate visualization. Depending on patient anatomy, the arthroscope can be switched to the anterolateral portal to obtain another view of the defect. A spinal needle is centered over the Malgaigne (Hill-Sachs) lesion, and an accessory posterolateral portal is created 2 fingerbreadths lateral to the posterior viewing portal to allow orthogonal insertion of suture anchors. The use of a cannula is optional. A shaver is used to abrade the Malgaigne (Hill-Sachs) lesion. Two anchors are inserted in the valley of the defect adjacent to the articular margin, 1 superior and 1 inferior. If used, the cannula is at this point retracted into the subdeltoid space. A curved penetrating grasper is used to retrieve the inferior anchor suture, followed by a straight penetrating grasper for the superior anchor suture. The humeral head is reduced, and the inferior sutures are tied in mattress fashion in the subdeltoid space, followed by the superior sutures, to complete the remplissage.

=====Subscapularis Tendon Augmentation or Capsular Reconstruction=====
When traditional arthroscopic Bankart repair is not possible due to severe capsulolabral deficiency, different types of open or arthroscopic subscapularis tendon augmentation or capsular reconstruction have been described.<ref name=":27">Denard PJ, Narbona P, Lädermann A, Burkhart SS. Bankart augmentation for capsulolabral deficiency using a split subscapularis tendon flap. Arthroscopy 2011;27:1135-41.</ref><ref>Maiotti M, Massoni C, Russo R, Schroter S, Zanini A, Bianchedi D. Arthroscopic Subscapularis Augmentation of Bankart Repair in Chronic Anterior Shoulder Instability With Bone Loss Less Than 25% and Capsular Deficiency: Clinical Multicenter Study. Arthroscopy 2016.</ref><ref>Maiotti M, Russo R, Zanini A, Schroter S, Massoni C, Bianchedi D. Arthroscopic Bankart repair and subscapularis augmentation: an alternative technique treating anterior shoulder instability with bone loss. J Shoulder Elbow Surg 2016;25:898-906.</ref><ref>Russo R, Della Rotonda G, Cautiero F, Ciccarelli M, Maiotti M, Massoni C, Di Pietto F, Zappia M. Arthroscopic Bankart repair asciated with subscapularis augmentation (ASA) versus open Latarjet to treat recurrent anterior shoulder instability with moderate glenoid bone loss: clinical comparison of two series. Musculoskelet Surg 2016.</ref>

[[File:1562546211256-lg.jpg|center|thumb|609x609px|Bankart augmentation with split subscapularis tendon transfer. (A) A flap of the posterior portion of the superior half of the subscapularis tendon is created. (B) The subscapularis flap is mobilized in a trapdoor fashion such that the capsular surface of the subscapularis tendon is reflected from medial to lateral as a separate lamina while the outer surface is left unaltered. Note, arrows in (A) and (B) point to the free margin of the subscapularis tendon flap. (C) The subscapularis flap undergoes tenodesis to the anterior glenoid suture anchors to augment capsulolabral deficiency. Reproduced from Denard et al.,<ref name=":27" /> with permission.|alt=]]

Surgical technique
A standard diagnostic arthroscopy is performed with a 30 degrees arthroscope, viewing through a posterior portal with a pump maintaining pressure of 50 mm Hg. The labrum is inspected in its entirety. An anterior portal is established just above the lateral half of the subscapularis and medial to the sling of the biceps, by use of an 18-gauge spinal needle with an outside-in technique. An anterosuperolateral portal is similarly established off the anterolateral border of the acromion. This portal should be placed so that it provides a 45 degrees angle of approach to the superior glenoid. The arthroscope is placed in the anterosuperolateral portal, and the anterior labrum is more thoroughly inspected. The remaining capsulolabral sleeve is dissected from the glenoid neck with an arthroscopic elevator until the subscapularis muscle is visible deep to the cleft. A 2- to 3-mm strip of articular cartilage is removed along the glenoid rim with a ring curette, creating an enhanced bone bed for capsulolabral repair. A capsulolabral repair is performed inferiorly with whatever good tissue remains. An anteroinferior anchor is placed. After placement of this anchor, if there is insufficient capsulolabral tissue to create the desired “bumper” along the anterior glenoid rim, the surgeon must consider various reconstructive options, including a split subscapularis tendon flap.

=====Augmentation With Split Subscapularis Flap=====
To augment the capsulolabral deficiency, a flap of the posterior portion of the superior half of the subscapularis tendon is mobilized and undergoes tenodesis to the anterior glenoid. This flap is created in a “trapdoor” fashion such that the capsular surface of the subscapularis tendon is reflected from medial to lateral as a separate lamina while the outer surface in left unaltered. By use of arthroscopic scissors introduced through the anterior portal, a longitudinal incision through one-half the thickness of the subscapularis is created in the superior half of the tendon (Figure).
[[File:1562547676763-lg.jpg|center|thumb|600x600px|Left shoulder, anterosuperolateral viewing portal, showing creation of a split subscapularis flap to augment a Bankart repair in the setting of capsulolabral deficiency. The flap is created with arthroscopic scissors introduced through an anterior portal. Suture is also seen from an inferior Bankart repair (arrow). (SSc, subscapularis tendon.). Reproduced from Denard et al.<ref name=":27" />, with permission.]]

Care is taken not to violate the full thickness of the subscapularis. The subscapularis flap dissection progresses from medial to lateral until the leading medial edge of the flap is mobile enough to reach the anterior glenoid. After mobilization of the subscapularis tendon flap, additional suture anchors are placed on the previously prepared glenoid strip at the 3-o'clock and 4-o'clock positions. Sutures from the anchor are passed through the subscapularis flap and tied as described previously. This completes the augmentation with a split subscapularis tendon flap (Figure).

[[File:1562547677981-lg.jpg|center|thumb|1071x1071px|Left shoulder, anterosuperolateral viewing portal, showing completed arthroscopic Bankart repair augmented with a split subscapularis flap in the setting of capsulolabral deficiency. (A) Completed repair showing restoration of anterior soft tissue by use of the split subscapularis tendon (SSc) flap. (B) The split between the subscapularis (arrow) is visualized anterior to the flap that has undergone tenodesis. (G, glenoid; H, humeral head.). Reproduced from Denard et al.,<ref name=":27" /> with permission.]]

Postoperatively, the patient's extremity is placed in a sling for 6 weeks. At the end of six weeks, stretching exercises are commenced with full forward flexion allowed and external rotation to half that of the contralateral shoulder. The goal is to achieve half the external rotation of the normal side at three months postoperatively. Strengthening is delayed until four months postoperatively because this is usually a last-resort salvage procedure. Return to full activities is delayed until one year postoperatively.

=====Dynamic Anterior Stabilization (DAS)=====
[[File:1562547970547-lg.mp4|center|thumb|600x600px|Video]]

Dynamic anterior stabilization transfers the long head of the biceps to the anterior glenoid margin, thereby creating a “sling effect” (Figure).
[[File:1562547677283-lg.jpg|center|thumb|700x700px|(A) Native shoulder. (B) Latarjet procedure. The coracoid graft including the conjoint tendon is secured to the anterior glenoid by means of two 4.5-mm screws. (C) Dynamic anterior stabilization. The long head of the biceps is transferred to the anterior glenoid margin. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]
 The dynamic anterior stabilization technique provides decreased anterior glenohumeral translation in cases of Bankart lesions with limited anterior bone loss (<20%)<ref>Mehl J, Otto A, Imhoff FB, Murphy M, Dyrna F, Obopilwe E, Cote M, Lädermann A, Collin P, Beitzel K, Mazzocca AD. Dynamic Anterior Shoulder Stabilization With the Long Head of the Biceps Tendon: A Biomechanical Study. Am J Sports Med. 2019 May;47(6):1441-1450.</ref>

In comparison with isolated Bankart repair, it is able to stop the anterior translation less anterior and therefore reduces the risk of a conflict between the humeral head and the anterior margin of the glenoid. It is also easier and safer than arthroscopic Latarjet. Moreover, it does not require screws nor traction of the coracoid process, and should consequently reduce the risks of neurologic damage. Furthermore, the procedure can be performed with only 3 small incisions (Video), as it does not require coracoid transfer, which eliminates risks of nerve dissection, graft overhang and cortical resorption, hence reducing the probability for dislocation arthroplasty. Lastly, the pectoralis minor remains intact, which would avoid scapular dyskinesis. The potential drawbacks of the dynamic anterior stabilization are that it relies on the long head of biceps tendon, which has smaller diameter than the conjoint tendon and could therefore have a weaker “sling effect” than that of the standard Latarjet. Also, there are, like in the Latarjet procedure, the risks of biceps pain, and secondary iatrogenic factors. Furthermore, in cases with larger bone defects (≥ 20 %) there is a relevant posterior and inferior shift of the humeral head in relation to the glenoid, when the arm is brought in the ABER position.(reference to be completed) Indications and limitations are yet to be defined. MRI scans showed that the transposed long head of the biceps successfully healed to the glenoid rim and remained intact at the 6- and 12-month follow-ups in patients who underwent dynamic anterior stabilization for the treatment of chronic anteroinferior glenohumeral instability with bipolar and/or SLAP II lesions with limited (<13.5%) to subcritical (13.5%—25%) glenoid bone loss.<ref name=":28">de Campos Azevedo C, Ângelo AC. All-Suture Anchor Dynamic Anterior Stabilization Produced Successful Healing of the Biceps Tendon: A Report of 3 Cases. JBJS Case Connect . 2021:17;11(1)</ref> However, it is recommended that future studies are carried out with a more long-term follow-up.

Preoperative Patient Positioning
The operation, illustrated in the video, is performed in the semi-beach chair position under general anesthesia with an interscalene block. An examination under anesthesia is performed before prepping and draping the arm.

Initial Exposure and Portal Placement
An intra-articular approach is used through a standard posterior portal (soft spot), a standard diagnostic arthroscopy is performed with a 30-degree arthroscope and a pump maintaining pressure at 60 mm Hg. Antero-lateral and anterior portals are then established by an outside-in technique using a spinal needle as a guide. The rotator interval is opened, and the internal structures (glenoid defects, humeral defects, etc.) are further assessed with a probe.

Anterior Glenoid Preparation
From a lateral viewing portal, the labrum, if necessary, is detached from the glenoid, and a suture is passed around the labrum and pulled through the posterior portal to increase access for preparation of the anterior glenoid (Figure). The glenoid neck is cleaned from soft tissues at around 3 o’clock with a burr.

[[File:1562549774413-lg.jpg|center|thumb|600x600px|Intra-articular view of a right shoulder, anterolateral viewing portal. A suture is passed around the detached labrum and pulled through the posterior portal to increase access for preparation of the anterior glenoid. ∗ indicates the labrum, the black arrows the access to the glenoid neck, and HH the humeral head. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

Addressing the Long Head of Biceps and Subscapularis Split
The long head of biceps is then tenotomized and the biciptal groove is opened laterally and distally to avoid detaching the subscapularis (Figure).
[[File:1562549775232-lg.jpg|center|thumb|600x600px|Retrocoracoid space of a right shoulder, anterolateral viewing portal. After LHB tenotomy, the bicipital sheath (black arrows) is opened laterally and the LHB (∗) is found. (CT, conjoint tendon; LHB, long head of the biceps.). Reproduced from Collin et al.,<ref name=":13" /> with permission.]]
The biceps is then exteriorized, and secured 20 mm from the proximal tendon. From a lateral viewing portal the subscapularis is exposed on three sides, together with the lateral margin of the conjoint tendon. Three options exist to create a split in the middle of the subscapularis above the junction of the superior two-thirds used in the standard Latarjet procedure: From a lateral viewing portal, either a switching stick (Wissinger Rod) can be passed across the glenohumeral joint through a posterior approach at the level of the inferior glenoid (Figure), an outside-in approach can be used or simply by passing through the subscapularis muscle with a suture passer, by grabbing the sutures that secure the biceps and pulling the biceps through the tendon.

[[File:1562549776269-lg.jpg|center|thumb|600x600px|Intraoperative view of a right shoulder with passage of the switching stick (∗) across the glenohumeral joint at the level of the inferior glenoid to the subscapularis. (HH, humeral head). Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

The switching stick is now found in the retrocoracoid space and maintained lateral to the conjoint tendon to avoid damaging the nerve plexus. The probe is then introduced through the anterior portal to complete the split.

Long Head of Biceps Tenodesis to Anterior Glenoid
A drill is then used to prepare a hole at 3 o'clock from anterior to posterior within the neck of the glenoid, 2.0 cm deep, depending on the length of the interference screw. The LHB tendon is then passed through the subscapularis split into the pre-drilled hole, to establish the “sling effect”, and fixed using a tenodesis screw (Figure).

[[File:1562549775588-lg.jpg|center|thumb|600x600px|Intraoperative view of a right shoulder through the subscapularis split, anterolateral viewing portal. The long head of the biceps tendon (black arrow) is fixed using a tenodesis screw (∗) to establish the “sling effect”. Reproduced from Collin et al.<ref name=":13" />, with permission.]]

Alternatively, the biceps may be managed without exteriorization, as shown in the linked video.[https://www.vumedi.com/video/all-suture-anchor-double-double-pulley-dynamic-anterior-stabilization/] When choosing this technical variant, two all-suture anchors (double loaded with sutures) must me placed on the glenoid rim and each of the respective eight suture limbs must be passed through the biceps before the tenotomy is completed; a double-pulley technique is used to shuttle the biceps through the subscapularis tendon split to the anteroinferior glenoid; the biceps is fixed to the glenoid with a total of four knots (Figure).

[[File:Figure 4 jpeg.jpg|none|thumb|959x959px|Representation of the posterior portal arthroscopic view of the trans-subscapular transposition of the long head of the biceps using the double double-pulley on a right shoulder in the beach chair position. A) Two knots of the double double-pulley are tied after all suture limbs were passed through the long head of the biceps (LHB) tendon; B) the remaining 4 opposing suture limbs are pulled and the LHB tendon reaches the anteroinferior glenoid rim after passing through the subscapularis tendon (SC) split; C) the dashed line represents the final course of the LHB tendon through and anteriorly to the subscapularis tendon. The opposing 4 suture limbs will each be used to obtain an additional 2 knots to reinforce the fixation of the LHB to the glenoid rim. Reproduced from de Campos Azevedo and Ângelo<ref name=":28" />, with permission.]]

Labral Repair
With the arthroscope through the posterior portal, a standard Bankart repair is performed using 2-3 suture anchors. The anchors are placed on the glenoid rim at 3, 4, and 5 o’clock to enable the retention of the capsulo-ligamentous structures and to re-establish the labral damper effect (Video and Figure).
[[File:1562549775598-lg.jpg|center|thumb|600x600px|Intra-articular view through the posterior portal. Associated capsulolabral repair using 2 to 3 anchors recreates normal articular concavity (bumper effect). The anchors are placed on the glenoid rim between 3 and 6 o'clock, depending on the lesion. ∗ indicates the labrum. Reproduced from Collin et al.,<ref name=":13" /> with permission.]]

Postoperative Rehabilitation
Patients are instructed to wear a simple sling for 10 days encouraging rest and reducing the risk of post-operative hematoma formation. Rehabilitation with self-mobilization in elevation and external rotation is allowed from day 0. At 10 days, activities of daily living are allowed and self-mobilization in elevation and external rotation continued. Return to low-risk sports (eg, jogging, cycling, and swimming) is allowed at 6 weeks, and high-risk (throwing and collision) sports at 3 months only after satisfactory clinical and radiographic evaluations confirm satisfactory healing of the coracoid graft. Initially, no physiotherapy is recommended.

====Bony procedures====
In the setting of glenoid bone loss ≥20% of the glenoid diameter an arthroscopic Bankart repair has an unacceptably high rate of recurrence. Burkhart and DeBeer reported a 4% recurrence rate for arthroscopic Bankart repair when glenoid bone loss was <25%. However, with glenoid bone loss ≥25%, the recurrence rate was 67% with an arthroscopic approach. They subsequently recommended a bony procedure procedure in the population with substantial glenoid bone loss.<ref name=":4" />

Treatment is based on patient factors and associated pathology as previously discussed. In general, for patients under the age of 30, primary stabilization following a first traumatic anterior instability episode is offered. Such patients are counseled on the natural history or anterior instability and the potential for subsequent injury. For the majority of patients over the age of 30, nonoperative treatment is advised with standard sling immobilization for three weeks followed by progressive strengthening and return to activities. For such patients with persistent weakness or recurrent instability a magnetic resonance imaging (MRI) or MRI arthrogram is obtained to evaluate for an associated rotator cuff tear and stabilization is performed.

In consideration of the current literature, the following indications for osseous reconstruction procedures of the glenoid concavity can be recommended: - Substantial erosion-type defects (type IIIb), which constitute the instability-associated main pathology. - Chronic fragment-type defects (type II), where the glenoid area and concavity cannot be reconstructed by mobilization and refixation of the fragment. - In the rare patient with an acute, non-reconstructible, multifragmented glenoid fracture (type Ic). - In cases of revision surgery, e.g. after failed soft-tissue stabilization, a glenoid augmentation procedure is recommended also for smaller bony defects (type IIIa).

=====Open Latarjet=====
In 1954, Latarjet reported a coracoid transfer procedure in which the inferior aspect of the coracoid was secured to the anterior glenoid. The excellent stability of this procedure is obtained by a triple effect first proposed by Patte:<ref>Patte D, Debeyre J. Luxations récidivantes de l’épaule. Tech Chir Orthop Paris: Encycl Med Chir 1980:44–52.</ref>

1) the sling effect of the conjoint tendon when the arm is abducted and externally rotated, 2), the ‘‘bony effect’’ that increases or restore the glenoid anteroposterior diameter (Figure), and 3) the retensionning of inferior capsule to the stump of coracoacromial ligament, rending the coracoid extra-articular.
{| class="wikitable"
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![[File:1562549774884-lg.jpg|center|thumb|412x412px]]A
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''Illustration of the three effects A) the sling effect, B) the bony effect and C) the retensioning of the capsule. Courtesy of Gilles Walch.'' 

When the arm is at an end-range position, the sling effect contributes 76-77% at different loads and the capsule the remaining 23-24% to the stabilization of the humeral head. At the mid-range position of the arm, the sling effect facilitates 51-62% and the bone block 38-49% of the stability. The sling effect, therefore, seems to constitute the number one stabilizing mechanism of the Latarjet procedure at both, the mid- and end-range of motion. The internal-external range of motion is thereby not significantly impaired.<ref>Yamamoto N, Muraki T, An KN, Sperling JW, Cofield RH, Itoi E, Walch G, Steinmann SP. The stabilizing mechanism of the Latarjet procedure: a cadaveric study. J Bone Joint Surg Am 2013;95:1390-7.</ref>

The Latarjet procedure is associated with a very low recurrence rate even in the setting of substantial glenoid bone loss and has become the gold standard of treatment in such settings. In addition, this non-anatomic method of anterior glenohumeral stabilization has progressively expanded and is actually the primary technique of choice for many European surgeons, as it prevents recurrent anterior instability in approximately 95 to 99% of cases. This procedure is also favored by some as a first choice in many contact athletes.<ref>Joshi MA, Young AA, Balestro JC, Walch G. The Latarjet-Patte procedure for recurrent anterior shoulder instability in contact athletes. Clinics in sports medicine 2013;32:731-9.</ref>

[[File:1562549775732-lg.jpg|center|thumb|600x600px|Illustration of a partial remodelling after an anteroposterior 2.5 cm tricortical iliac crest bone block. Antero-posterior (A) and Neer (B) view of a right shoulder after iliac crest bone block. Observe on 3 years computer tomography (CT) scan follow-up, the anteroposterior diameter of the glenoid remains supraphysiologic, explaining the efficiency of this open procedure.]]
Surgical technique (Video)
[[File:1563403564475-lg.mp4|center|thumb|300x300px|Video]]

Patient preparation
The patient is positioned in a classical, 40 degrees, beach chair position, preferably under a combination of general anesthesia and locoregional interscalene block to maximize the patient and the surgeon’s comfort. A single prophylactic antibiotic dose is highly recommended, as infectious complications are not uncommon in the proximity of the axilla. The upper limb is draped freely to allow manipulation of the shoulder and placed on an arm board. The operative site, including the sternoclavicular joint medially, is covered with iodine incise drape.

Incision
The incision is performed under the tip of the coracoid process extending 4 to 5 cm distally.

The dissection begins at the level of the Mohrenheim fossa, a triangular region just inferior to the clavicle, between the deltoid and pectoralis major muscles which do not contain neurovascular structures. The deltopectoral interval is then opened bluntly with two Richardson retractors, letting the cephalic vein medially (Fig 2 and Video 1). The Gelpi retractor is placed deep in the approach, while the cephalic vein is retracted laterally. The whole coracoid process with the insertion of pectoralis minor, coracoacromial ligament, and the conjoined tendon (CT) is exposed by placing the Hohmann retractor on its tip (Fig 3 and Video 1). The pectoralis minor is released from the coracoid process with electrocautery while the arm is internally rotated and adducted (Fig 4 and Video 1). The upper limb is abducted and fully externally rotated to improve the coracoacromial ligament visualization, which is then released approximately 1.5 cm laterally from its attachment (Fig 5 and Video 1).

Coracoid graft harvest and preparation
A 90° angled saw blade is used to perform a coracoid process osteotomy at its base as far back as possible but still just anterior to the coracoclavicular ligament, starting superomedialy and proceeding inferolateraly (Fig 6 and Video 1). When the coracoid process gets loose, a chisel is meticulously used to complete the osteotomy (Fig 7 and Video 1). The coracoid process is rotated for 180° while being held with a grasper. It is attentively released until the muscle belly is uncovered in order to be easily and safely manipulated. The coracoid process should not be placed outside the surgical field to avoid tension in musculocutaneous nerve neuropraxia. Its undersurface is flattened and slightly decorticated with a saw blade to create a healthy bleeding surface that will precisely conform to the later prepared anterior glenoid (Fig 8 and Video 1). The two 4 mm holes for screw fixation are drilled equally distant from the base and the tip, 1 cm apart and 8-9 mm laterally from the insertion of the coracoacromial (Fig 9 and Video 1). It is essential that the holes are drilled perpendicularly to the surface and centrally to the graft. There are two options for labral fixation, either by transosseous coracoid fixation or by fixation with anchors at the later medial coracoid-glenoid edge. If the surgeon chooses the transosseous coracoid fixation, two holes for later labral fixation are predrilled with a K-wire on the lateral coracoid process bony rim where the coracoacromial inserts, but so that they are placed bellow it and do not pass it. A non-resorbable suture is shuttled through each of them. The coracoid process is retracted medially with the pectoralis major muscle.

Glenoid preparation
At this stage, the anteroinferior quadrant of the glenoid should be perfectly exposed for preparation. The anterior glenoid surface is prepared with an osteotome to obtain a spongious bed for the graft.

A 3.2 mm drill is used to first drill the inferior hole in the glenoid. The hole should be at the 5 o’clock position, 7 mm medially to the joint. When drilling, it is important to stay as parallel as possible to the glenoid surface, as an angle exceeding ten degrees in the axial plane puts the suprascapular nerve at high risk of lesion at its course on the posterior glenoid rim (Figure).<ref name=":23">Lädermann A, Denard PJ, Burkhart SS. Injury of the suprascapular nerve during Latarjet procedure: an anatomic study. Arthroscopy 2012;28:316-21.</ref>[[File:1562551669419-lg.jpg|center|thumb|591x591px|A) The suprascapular nerve passes through the scapular notch beneath the transverse scapular ligament to enter the supraspinatus fossa and provide motor innervation to the supraspinatus muscle. The nerve then courses distally around the base of the scapular spine (spinoglenoid notch) to enter the infraspinatus fossa and provide motor innervation to the infraspinatus muscle. B) The infraspinatus branches of the suprascapular nerve are at risk during screw placement for Latarjet reconstruction. Reproduced from Lädermann et al., with permission.]]

Coracoid Positioning and Fixation
The coracoid bone block is now removed from its protective location behind the autostatic retractor. Usually, a 28-30 mm inferior screw is used. The graft is positioned on the prepared anteroinferior glenoid quadrant in such a way that its lateral border is perfectly flush with the glenoid. The superior hole is then drilled and measured with precision to avoid any screw protrusion. Another 4.5 mm self-tapping standard cortical screw is chosen accordingly. The capsule and the labrum are reinserted between the glenoid and the graft according to Luc Favard’s technique in order to decrease the risk of dislocation arthropathy (Video). The sutures are tighten with the arm positioned in full external rotation elbow at the side, elevation, with the assistant pushing the humeral head posteriorly in order to reduce the shoulder. Both screws are finally tightened using a ‘‘2-finger’’ technique.

[[File:1562551689499-lg.mp4|center|thumb|600x600px|Video]]
[[File:1562551676712-lg.mp4|center|thumb|600x600px|Video]]
[[File:1562551685548-lg.mp4|center|thumb|600x600px|Video]]
[[File:1562551686995-lg.mp4|center|thumb|600x600px|Video]]

Capsulo-labral reconstruction
Finally, the anterior capsule is reconstructed by the imbrication of the coracoacromial ligament with a resorbable suture. While the operated arm is held in external rotation to avoid the postoperative rotational deficit, the humeral head is reduced posteriorly in the center of the glenoid during adduction, slight anterior forward flexion, and a posterior level push. (Figure and Video). Only then, an adequate capsular tension is expected. The wound is copiously irrigated.

Closure
The Trillat retractor is removed. The tendinous part of the subscapularis muscle lateral to the conjoint tendon is closed side to side with a non-resorbable suture, while making sure not to puncture the anterior ascending branch of the circumflex artery. The wound is closed and a drain is typically not used, unless excessive bleeding is noted.

=====Arthroscopic Latarjet=====
Surgical Technique
Operations are performed in the usual semi-beach chair position under general anesthesia with an interscalenic block or catheter. Arthroscopic Latarjet are carried out using a total of 5 portals (posterior, anterolateral, anterior, suicide, and superior to access the superior coracoid (Figure 34).
[[File:1562552295999-lg.jpg|center|thumb|600x600px|A) Anterior view, B) posterior view. The modified 5 portals are used for the arthroscopic Latarjet. AL anterolateral, A anterior, S superior, Su suicide portal, P posterior portal. Reproduced from Cunningham et al., with permission.]]
 Intra-articular approach is carried out through the standard “soft spot” posterior portal. The rotator interval is opened, and the internal structures (glenoid defects, humeral defects, HAGL, etc.) are further assessed with the probe. To provide a healthy bed for graft healing, the glenoid neck is abraded between 2 and 5 o’clock with a burr. A release of the subscapularis on 270 degrees and of the lateral side of conjoint tendon are then performed. The two subscapularis nerves and the axillary nerve are only located and not dissected as this may lead to neurological lesions. From a lateral viewing portal, a switching stick is inserted through the posterior approach, passed across the glenohumeral joint at the level of the glenoid defect and then advanced through subscapularis to establish the level of split. From the suicide portal, a modified cannulated subscapularis splitter is advanced on the switching stick to facilitate the split.

The probe is then introduced through the anterior portal to complete the split. The latter is thus done before coracoid osteotomy consequently protecting the plexus. At this point, with the scope in the anterior portal, the coracoid is prepared and then osteotomized with osteotome rather than a burr, in order to keep maximum graft length. The graft is extracted through the suicide portal and prepared outside, as inside debridement and trimming might be less accurate and puts the plexus at risk. The coracoid is then secured on the coracoid positioning cannula and positioned on the glenoid neck flush with the glenoid border. Two long K-wires are inserted through the coracoid positioning cannula, and the glenoid is drilled with a 3.2-mm drill bit. The length of the definitive screw is directly read from the depth gauge on the drill. The fixation is obtained with two 4.5-mm cannulated malleolar screws (Figure).

[[File:1562552292659-lg.jpg|center|thumb|600x600px|A) arthroscopic view and B) postoperative anteroposterior x-ray of a left Latarjet procedure. * indicates the graft fixed on the anterior glenoid. Reproduced from Lädermann et al., with permission.]]

=====Open Bristow=====
Independently of Latarjet, Helfet reported in 1958 a slightly different procedure named after his master, Bristow, where the coracoid with conjoined tendon attached was pressed against the anterior glenoid by suturing it to a slit in the subscapularis tendon instead of a screw.<ref name=":2" />

Despite the frequent synonymous labeling as “Bristow-Latarjet” coracoid transfer, the techniques remain distinct and non-equivalent reconstructive procedures. When differentiating between the coracoid transfer techniques, the stabilizing effect by the Bristow technique is inferior to that of the Latarjet procedure in cases of substantial glenoid bone loss due to the difference in coracoid graft size but also due to the direction of the conjoint tendon (Figure).<ref>Giles JW, Degen RM, Johnson JA, Athwal GS. The Bristow and Latarjet procedures: why these techniques should not be considered synonymous. J Bone Joint Surg Am 2014;96:1340-8.</ref>

[[File:1562552295240-lg.jpg|center|thumb|600x600px|Direction of the conjoint tendon in A) Latarjet and B) Bristow procedure (courtesy of George Athwal). Note that the conjoint tendon (blue arrow) during Latarjet has to go around the inferior subscapularis (dark blue). Contrarily, the conjoint tendon exits directly through the split during Bristow procedure. * indicates the origin of the conjoint tendon. Reproduced from Lädermann et al., with permission.]]

Surgical technique
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=====Arthroscopic Bristow=====
[[File:1562553238652-lg.mp4|center|thumb|600x600px|Video]]

Coracoid Preparation, Drilling, and Osteotomy
The arthroscope is initially maintained in the posterior viewing portal. By use of electrocautery through the anterolateral portal, the rotator interval is opened and the subscapularis is followed medially to the coracoid. During this time, the arm should be internally rotated to relax the subscapularis. The coracoid is dissected and the coracoacromial ligament is released. The anterior portal is established just medial to the coracoid, and the pectoralis minor is released. The undersurface of the coracoid is flattened with a motorized rasp through the anterolateral portal. The coracoid is drilled with a coracoid drill guide, a polydioxanone suture is passed through the bone tunnel, and the coracoid peg button is shuttled in place. Through the anterolateral portal, the coracoid undergoes osteotomy 1.5 to 2.0 cm from its tip.

Glenoid Preparation and Anchor Insertion
The labrum is released from the anterior glenoid neck, and a polydioxanone suture is placed through the labrum at the 5-o'clock position. The anterior glenoid neck is abraded to a flat surface using a motorized rasp and a suture anchor inserted at the 3-o'clock position to be used later for the Bankart repair.

Subscapularis Splitting and Axillary Nerve Protection
By use of switching sticks, the arthroscope is transferred to the northwest portal, the anterior glenoid neck preparation is confirmed, and a short half-pipe cannula is placed through the posterior portal. The glenoid drill guide is inserted over the cannula and placed flush with the glenoid face at the 5-o'clock position. A switching stick retracts the labrum and subscapularis through the west portal, and the glenoid tunnel is drilled from posterior with a 2.8-mm K-wire (the outer sleeve is left in place to facilitate the cortical-button transfer later). The posterior subscapularis spreader replaces the glenoid drill guide and is pushed through the subscapularis muscle along with the 5-o'clock position, at the inferior one-third junction of the subscapularis. An anterior bursectomy is performed through the south portal to identify the “3 sisters” (anterior humeral circumflex vasculature), which are followed to the “2 brothers” (musculocutaneous and axillary nerves). The nerves are carefully protected with a nerve retractor, and the tip of the posterior spreader is slowly opened within the subscapularis muscle. The tendon is split from medial to lateral while the capsule is being preserved, and the anterior subscapularis spreader is inserted through the east portal with its tip medial to the posterior spreader.

Coracoid Transfer and Fixation
By use of a suture retriever through the posterior sleeve, the cortical button and coracoid bone block are transferred through the subscapularis muscle and lie flush with the anterior glenoid neck. This fixation is made using 2 round, 6.5-mm, slightly convex titanium buttons, connecting with a loop of continuous suture, forming 4 parallel strands. The glenoid cortical button is slid over the 4 white suture strands, a sliding-locking Nice knot is tied, and the button is advanced onto the posterior glenoid neck. A specific suture tensioner is used to increase bone compression to 100 N.

Bankart Repair
Using the previously placed glenoid anchor, we complete the labral repair, placing the bone block in an extra-articular position. Additional anchors can be inserted depending on the clinical situation and patient anatomy. The tensioning device is removed posteriorly, and 3 surgeon's knots are tied to complete the coracoid fixation.

=====Eden-Hybinette and Other Free Bone Block Transfers=====
Aiming to reduce donor site morbidity associated with the harvesting of autologous bone blocks, autografts of the iliac crest and distal clavicle and allograft of femoral head and distal tibia have been evaluated (Figure).<ref>Mascarenhas R, Raleigh E, McRae S, Leiter J, Saltzman B, MacDonald PB. Iliac crest allograft glenoid reconstruction for recurrent anterior shoulder instability in athletes: Surgical technique and results. International journal of shoulder surgery 2014;8:127-32.</ref><ref name=":24">Provencher MT, Ghodadra N, LeClere L, Solomon DJ, Romeo AA. Anatomic osteochondral glenoid reconstruction for recurrent glenohumeral instability with glenoid deficiency using a distal tibia allograft. Arthroscopy 2009;25:446-52.</ref><ref>Weng PW, Shen HC, Lee HH, Wu SS, Lee CH. Open reconstruction of large bony glenoid erosion with allogeneic bone graft for recurrent anterior shoulder dislocation. Am J Sports Med 2009;37:1792-7.</ref><ref>Zhao J, Huangfu X, Yang X, Xie G, Xu C. Arthroscopic glenoid bone grafting with nonrigid fixation for anterior shoulder instability: 52 patients with 2- to 5-year follow-up. Am J Sports Med 2014;42:831-9.</ref>

Anatomically, iliac crest bone blocks offer the possibility of a nearly unrestricted graft size, but also the coracoid process was found to be a sufficient graft source to re-establish the anatomy for most glenoid defect cases.<ref>Bueno RS, Ikemoto RY, Nascimento LG, Almeida LH, Strose E, Murachovsky J. Correlation of coracoid thickness and glenoid width: an anatomic morphometric analysis. Am J Sports Med 2012;40:1664-7.</ref>

Provencher et al. described the use of an osteochondral tibia allograft with the advantages of a cartilaginous interface, improved graft availability and an excellent glenoid articular conformity.<ref name=":24" />

Radiologically, successful bony consolidation and a remodeling process of the allografts have been observed, as described for autologous glenoid reconstruction. However, a slightly higher recurrence rates of 0-22% were observed.

[[File:1562555338099-lg.jpg|center|thumb|600x600px|Illustration and arthroscopic intra-operative view of a left anatomic and intra-articular iliac crest bone grafting technique with graft fixation by two bio-compression screws. Reproduced from Lädermann et al., with permission.]]

Surgical Technique
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=====Trillat=====
[[File:Capture d’écran 2020-01-28 à 22.02.11.png|thumb|Native situation]]

[[File:Capture d’écran 2020-01-28 à 22.02.54.png|thumb|Illustration of a shoulder after Trillat procedure]]

[[File:Capture d’écran 2020-01-28 à 22.03.20.png|thumb|Effect of the Trillat procedure with the arm in abduction-external rotation]]

==Rehabilitation==

===Non-Operative Treatment of Acute First Traumatic Dislocations===
Although positioning the arm in external rotation has been recommended, it has now clearly been demonstrated that immobilization of the shoulder in internal rotation after primary, traumatic anterior shoulder dislocation is sufficient.<ref>Vavken P, Sadoghi P, Quidde J, Lucas R, Delaney R, Mueller AM, Rosso C, Valderrabano V. Immobilization in internal or external rotation does not change recurrence rates after traumatic anterior shoulder dislocation. J Shoulder Elbow Surg 2013.</ref><ref>Itoi E, Hatakeyama Y, Sato T, Kido T, Minagawa H, Yamamoto N, Wakabayashi I, Nozaka K. Immobilization in external rotation after shoulder dislocation reduces the risk of recurrence. A randomized controlled trial. J Bone Joint Surg Am 2007;89:2124-31.</ref><ref>Braun C, McRobert CJ. Conservative management following closed reduction of traumatic anterior dislocation of the shoulder. Cochrane Database Syst Rev. 2019 May 10;5:CD004962.</ref>

There is conflicting evidence regarding the length of immobilization required after dislocation but three weeks is typically recommended, followed by physical therapy for strengthening of the rotator cuff and scapular stabilizers. Range of motion of the elbow, wrist, and hand are permitted immediately. Then, closed-chain exercises facilitate rotator cuff function to enhance joint stability and stimulate muscular coactivation and proprioception.<ref>Jaggi A, Lambert S. Rehabilitation for shoulder instability. Br J Sports Med 2010;44:333-40.</ref>

For throwing athletes, a program is initiated and advanced, beginning at three months. A full return to sports is typically permitted at five to six months.

===Rehabilitation Protocol After Bankart and Remplissage Stabilization===
The shoulder is immobilized for four weeks using a sling. Passive and assisted-active exercises are then initiated for forward flexion and external rotation. After six weeks, patients begin strengthening exercises of the rotator cuff and scapular stabilizers. For patients with a remplissage strengthening is delayed until twelve weeks postoperative. Patients are permitted to practice noncontact sports as soon as they recover their range of motion. Full return to throwing or contact sports is usually allowed after six months according to each individual’s functional recovery.

===Rehabilitation Protocol After Dynamic Anterior Stabilization===
Patients are instructed to wear a simple sling for 10 days encouraging rest and reducing the risk of post-operative hematoma formation. Rehabilitation with self-mobilization in elevation and external rotation is allowed from day 0. At 10 days, activities of daily living are allowed and self-mobilization in elevation and external rotation continued. Return to low-risk sports (eg, jogging, cycling, and swimming) is allowed at 6 weeks, and high-risk (throwing and collision) sports at 3 months. Initially, no physiotherapy is recommended.<ref name=":13" />

===Rehabilitation Protocol After Latarjet Reconstruction===
The shoulder is immobilized for ten days using a sling. The patient is asked to stretch in flexion and external rotation at least five times per day. No physical therapy is prescribed. The patient is not allowed to carry with his operated arm or to flex the elbow against resistance during the first six weeks. Activities of daily living are encouraged as comfort permits. At six weeks, non-contact sports are allowed. Return to contact sports is usually possible after three months assuming confirmation of bony union of the coracoid graft.

==Results and Complications==

===Soft tissue procedures (Bankart, Remplissage)===
Arthroscopic Bankart stabilization with use of suture anchors offers the advantage of being minimally invasive, allows assessment of associated pathology, and allows the surgeon to restore anatomy while reattaching the labral lesion and retensionning the glenohumeral ligament. While the short-term outcome of Bankart has been excellent, mid-term reported results show higher rates of recurrent of instability. According to the meta-analysis by Hobby et al., recurrence (dislocation and subluxation) after arthroscopic Bankart repair with suture anchors varies between 0 to 29.6%, with a mean of 8.9%.<ref>Hobby J, Griffin D, Dunbar M, Boileau P. Is arthroscopic surgery for stabilisation of chronic shoulder instability as effective as open surgery? A systematic review and meta-analysis of 62 studies including 3044 arthroscopic operations. J Bone Joint Surg Br 2007;89:1188-96.</ref>

This rate of course varies with patient factors, particularly the amount of bony deficiency. Preoperatively, pitfalls are consequently to underestimate risk factors for recurrence for this surgery. In adolescent contact athletes undergoing arthroscopic labral repair, the overall recurrence rate is 51%. Rugby players who undergo primary arthroscopic shoulder stabilization aged <16 years have 2.2 times the risk of developing a further instability episode when compared to athletes aged ≥16 years at the time of index surgery, with a recurrence rate of 93%.<ref>Torrance E, Clarke CJ, Monga P, Funk L, Walton MJ. Recurrence After Arthroscopic Labral Repair for Traumatic Anterior Instability in Adolescent Rugby and Contact Athletes. Am J Sports Med 2018;46:2969-74.</ref>

Bankart repair combined with Malgaigne (Hill-Sachs) remplissage for large defects of the posterosuperior aspect of the humeral head may be an elegant approach in case of isolated humeral defect. Reported results are promising with a high rate of healing of the posterior aspect of the capsule and the infraspinatus tendon into the humeral defect, and a moderate loss of external rotation with the arm at the side. Moreover, most patients were able to return to sport including those involving overhead activities, around 70% at the same level.<ref name=":20" /><ref name=":21" />

The Malgaigne remplissage is believed to be a posterior capsulotenodesis that acts as a checkrein diminishing anterior humeral head translation and reducing the risk of postoperative redislocation. However, some authors have observed that according to the location of the impaction fracture, the procedure actually corresponds to a capsulomyodesis including the teres minor muscle, rather than a capsolutenodesis as classically described (Figure).
[[File:1562556949052-lg.jpg|center|thumb|600x600px|Posterior view of a right shoulder specimen after rotator cuff repair and Malgaigne (Hill-Sachs) remplissage (three lower knots). Note the proximity of the superior knot to the infraspinatus muscle (black arrow). The two inferior knots perforate the teres minor muscle (white arrow) realizing a capsulomyodesis.]]
 Concerns about remplissage may include the potential muscle lesion to the external rotators, increased cost, and increased difficulty and operative time. Yet, beyond a slight loss in postoperative external rotation, there is no documented additional complication to remplissage.

===Open Bone Block Procedures===
Open anatomical bone grafting procedures show very good clinical mid- to long-term results. With this procedure return to sports activities is possible for at least 83% of patients regardless of the size of glenoid defect. In a study of 107 patients, Lädermann et al. reported a mean postoperative Walch-Duplay score of 93, good or excellent results in 97% of cases, and 95% of patients very satisfied or satisfied with their outcome.<ref name=":14" />

However, complications exist both in the short- and long-term. A systematic review of 30 studies with a total of 1658 coracoid transfers, also including more recent surgeries with shorter follow-up periods, reported a low recurrence rate of 6.0%. The arthropathy rates is also reduced to 17-36% compared to the original procedures. A systematic review of 30 studies, comprising a total of 1658 open coracoid transfers, recorded graft non-union or postoperative graft migration (10.1%), hardware complications (6.5%), instability (6.0%), graft osteolysis (1.6%), infection (1.5%), nerve palsy (1.2%), intraoperative fractures (1.1%) and hematoma (0.7%) with a revision surgery conducted in 4.9% of the cases. Hardware problems were identified as the most frequent reason for revision surgery. In addition to failure of stabilization, hardware or graft malpositioning and respective screw breakage, loosening or migration is attended with a high risk for soft tissue as well as articular surface damage.<ref name=":22">Butt U, Charalambous CP. Arthroscopic coracoid transfer in the treatment of recurrent shoulder instability: a systematic review of early results. Arthroscopy 2013;29:774-9.</ref>

Regarding the postoperative muscle function, a significant strength deficit of the internal and external rotators was observed in comparison to the contralateral, unaffected shoulder.<ref>Caubere A, Lami D, Boileau P, Parratte S, Ollivier M, Argenson JN. Is the subscapularis normal after the open Latarjet procedure? An isokinetic and magnetic resonance imaging evaluation. J Shoulder Elbow Surg 2017;26:1775-81.</ref>

Risk of neurological impairment of the musculocutaneous nerve can be reduced by gently manipulating the coracoid process during preparation and avoiding an excessive medial dissection.<ref>Clavert P, Lutz JC, Wolfram-Gabel R, Kempf JF, Kahn JL. Relationships of the musculocutaneous nerve and the coracobrachialis during coracoid abutment procedure (Latarjet procedure). Surgical and radiologic anatomy : SRA 2009;31:49-53.</ref>

The suprascapular nerve is at risk posteriorly during screw insertion and can be protected by parallel placement of the screws within 10 degrees of the glenoid surface in the axial plane (Figures).<ref name=":23" />
[[File:1562556944819-lg.jpg|center|thumb|500x500px|The infraspinatus branches of the suprascapular nerve are at risk during screw placement for Latarjet reconstruction when a divergence of more than 10 degrees between the screws and the glenoid surface in the axial plane is noted. Photograph showing intimate proximity between screws placed for Latarjet procedure and suprascapular nerve. Reproduced from Lädermann et al., with permission.]]
[[File:1562556938948-lg.jpg|center|thumb|459x459px|Schema of screw and spinoglenoid notch orientation. (A) Axial view. The medial-to-lateral orientation was recorded by measuring the angle of the screws (α 1 angle) and of the spinoglenoid notch wire (β1 angle) relative to the glenoid plane. (B) Sagittal view. The superior-to-inferior orientation was determined by measuring the angle of the screws (α2 angle) and the spinoglenoid notch (β2 angle) perpendicular to the glenoid. (CG, coracoid graft; G, glenoid; HH, humeral head; SN, suprascapular nerve.). Reproduced from Lädermann et al., with permission.]]
[[File:1562556945397-lg.jpg|center|thumb|600x600px|Axial (A) and anteroposterior (B) plain radiographs of a left shoulder. The two screws diverge from the plane of the glenoid, pointing in direction of the spinoglenoid notch. A magnification (C) of the axial view demonstrates poor contact (white arrow) between the glenoid and the graft (delimited by red dotted line). Parallel screws would have led to better contact and a lower risk of suprascapular nerve injury]]
 

===Arthroscopic Bone Block Procedures===
Similarly, very good short-term results are achieved after arthroscopic glenoid rim reconstruction without events of postoperative redislocation and the advantage of subscapularis muscle preservation.<ref name=":25">Anderl W, Pauzenberger L, Laky B, Kriegleder B, Heuberer PR. Arthroscopic Implant-Free Bone Grafting for Shoulder Instability With Glenoid Bone Loss: Clinical and Radiological Outcome at a Minimum 2-Year Follow-up. Am J Sports Med 2016;44:1137-45.</ref><ref name=":26">Kraus N, Amphansap T, Gerhardt C, Scheibel M. Arthroscopic anatomic glenoid reconstruction using an autologous iliac crest bone grafting technique. J Shoulder Elbow Surg 2014;23:1700-8.</ref>

At present, however, merely short-term results of the arthroscopic techniques are published and only by the pioneers of these techniques. Following the arthroscopic coracoid transfer techniques, recurrence rates of 0-2% were observed after short- to mid-term follow-up investigations.<ref>Boileau P, Thélu CÉ, Mercier N, Ohl X, Houghton-Clemmey R, Carles M, Trojani C. Arthroscopic Bristow-Latarjet combined with bankart repair restores shoulder stability in patients with glenoid bone loss. Clin Orthop Relat Res 2014;472:2413-24.</ref><ref>Dumont GD, Fogerty S, Rosso C, Lafosse L. The arthroscopic latarjet procedure for anterior shoulder instability: 5-year minimum follow-up. Am J Sports Med 2014;42:2560-6.</ref><ref>Zhu YM, Jiang C, Song G, Lu Y, Li F. Arthroscopic Latarjet Procedure With Anterior Capsular Reconstruction: Clinical Outcome and Radiologic Evaluation With a Minimum 2-Year Follow-Up. Arthroscopy 2017.</ref>

The arthroscopic approach is, however, quite challenging and requires a lengthy learning curve. When directly comparing the arthroscopic and open techniques, a similar functional outcome and patient satisfaction were achieved, but screw placement inaccuracy, persistent apprehension, recurrence rate and complications were higher for the arthroscopic approach.<ref>Cunningham G, Benchouk S, Kherad O, Lädermann A. Comparison of arthroscopic and open Latarjet with a learning curve analysis. Knee Surg Sports Traumatol Arthrosc 2016;24:540-5.</ref>

A slightly reduced percentage of graft non-union or postoperative graft migration (8.1%), hardware problems (2.3%), instability (1.7%) and nerve injury (0.6%) was recorded, while the rate of osteolysis (4.1%) increased. Conversion to an open approach had to be conducted in 3.5% of the surgeries. However, a smaller number of cases conducted by fewer surgeons is available for evaluation of the arthroscopic approach. Larger case numbers by different surgeons and long-term results are therefore required to validate these first positive outcomes.<ref name=":22" />

===Remodeling of the Graft With Bone Block Procedure===
Regardless of the bone grafting technique employed, whether an implant-free or screw-based fixation method, a remodeling process according to Wolff’s law is observed with successful reconstruction of the anatomical pear-shaped glenoid configuration. Approximately 60% of the entire coracoid graft has been observed to undergo osteolysis. The superficial part of the proximal coracoid is predominantly affected, while the deep portion of the distal coracoid aspect showed the least osteolysis and best osseous union.<ref>Di Giacomo G, Costantini A, de Gasperis N, De Vita A, Lin BK, Francone M, Rojas Beccaglia MA, Mastantuono M. Coracoid graft osteolysis after the Latarjet procedure for anteroinferior shoulder instability: a computed tomography scan study of twenty-six patients. J Shoulder Elbow Surg 2011;20:989-95.</ref>

For the free bone grafting procedures, a partial extra-articular resorption of the initially oversized glenoid reconstruction may lead to restoration of the anatomic glenoid configuration over time in terms of a remodeling process (Figure).<ref>Moroder P, Hirzinger C, Lederer S, Matis N, Hitzl W, Tauber M, Resch H, Auffarth A. Restoration of anterior glenoid bone defects in posttraumatic recurrent anterior shoulder instability using the J-bone graft shows anatomic graft remodeling. Am J Sports Med 2012;40:1544-50.</ref><ref name=":26" />
[[File:1562557690817-lg.jpg|center|thumb|600x600px|Three-dimensional computer tomography reconstruction displaying an erosion-type defect (type III) before surgery (Figure 45 a), immediately after reconstruction using a free iliac crest autograft (Figure 45 b) and one year postoperatively (Figure 45 c) after completion of the remodeling with restoration of the anatomical glenoid configuration. Reproduced from Lädermann et al., with permission.]]
===Complication due to harvesting process of the iliac crest===
In comparison to the coracoid transfer procedure, free bone grafting techniques offer the advantage with potentially less severe complications. Complications of autologous bone grafting are predominantly associated with the harvesting process of the iliac crest bone block including pain, hypoesthesia and hematoma observed in 0-13% of the patients. Attempting to reduce donor site morbidity, current studies are evaluating the use of allogeneic bone material as an alternative to autografts. Further complications reported after open autologous iliac crest bone grafting comprise hardware failure (0-4%), shoulder hematoma (0-4%), subscapularis insufficiency (0-3%), graft fracture (0-2%), infection (0-2%) and adhesive capsulitis (0-2%).<ref>Auffarth A, Schauer J, Matis N, Kofler B, Hitzl W, Resch H. The J-bone graft for anatomical glenoid reconstruction in recurrent posttraumatic anterior shoulder dislocation. Am J Sports Med 2008;36:638-47.</ref><ref>Deml C, Kaiser P, van Leeuwen WF, Zitterl M, Euler SA. The J-Shaped Bone Graft for Anatomic Glenoid Reconstruction: A 10-Year Clinical Follow-up and Computed Tomography-Osteoabsorptiometry Study. Am J Sports Med 2016;44:2778-83.</ref><ref>Scheibel M, Nikulka C, Dick A, Schroeder RJ, Gerber Popp A, Haas NP. Autogenous bone grafting for chronic anteroinferior glenoid defects via a complete subscapularis tenotomy approach. Arch Orthop Trauma Surg 2008;128:1317-25.</ref><ref>Steffen V, Hertel R. Rim reconstruction with autogenous iliac crest for anterior glenoid deficiency: forty-three instability cases followed for 5-19 years. J Shoulder Elbow Surg 2013;22:550-9.</ref><ref>Warner JJ, Gill TJ, O'Hollerhan J D, Pathare N, Millett PJ. Anatomical glenoid reconstruction for recurrent anterior glenohumeral instability with glenoid deficiency using an autogenous tricortical iliac crest bone graft. Am J Sports Med 2006;34:205-12.</ref>

An investigation of 6449 patients reported an overall donor site morbidity rate of 19.4% after iliac crest bone harvesting including infections, chronic pain, fractures and nerve injuries at the harvesting site.<ref>Dimitriou R, Mataliotakis GI, Angoules AG, Kanakaris NK, Giannoudis PV. Complications following autologous bone graft harvesting from the iliac crest and using the RIA: a systematic review. Injury 2011;42 Suppl 2:S3-15.</ref>

The currently published studies evaluating arthroscopic autologous iliac crest bone grafting reported a singular case of donor site morbidity and one case of graft fracture in the 30 patients treated.<ref name=":25" /><ref name=":26" />

===Dislocation arthropathy===
Another complication is the development of dislocation arthropathy with a rate similar to other type of procedures (Figure).<ref>Hovelius LK, Sandstrom BC, Rosmark DL, Saebo M, Sundgren KH, Malmqvist BG. Long-term results with the Bankart and Bristow-Latarjet procedures: recurrent shoulder instability and arthropathy. J Shoulder Elbow Surg 2001;10:445-52.</ref>
[[File:1562557685456-lg.jpg|center|thumb|300x300px|Illustration of the three stage of dislocation arthropathy according to Samilson. Courtesy of Gilles Walch.]]
Even if the development of dislocation arthropathy is concerning (around 30%) (Figure), it is rather associated with the disease rather than to the surgery itself.
[[File:1562557685288-lg.jpg|center|thumb|600x600px|A) Anteroposterior plain radiographs of a left shoulder in a 32 year-old woman presenting with recurrent dislocations. Dislocation arthropathy Samilson B is obvious. B) CT scan of the same shoulder demonstrates significant glenoid and humeral bone loss.]]
While the precise cause is unknown, surgery in patients older than 40 years of age, a prolonged period between the initial dislocation and surgery and a lateral overhang of the transferred coracoid process in relation to the glenoid rim have been identified as risk factors. Contrarily, hyperlaxity was observed to be a protective factor against development of a dislocation arthropathy, which may be explained by the lower glenohumeral contact pressures.<ref name=":14" />

===Pull-out===
Anchor (Bankart repair) or screw (Latarjet, Bristow, free graft transfer) pull-out may happen (Figure).
[[File:1562557690266-lg.jpg|center|thumb|600x600px|A) Radiographs of a left shoulder ten days after a Latarjet reconstruction. The patient has been allowed to remove sling but not to do sport. B) The patient ignored the recommendation and was immediately jogging. He returned five hours after the last examination. Controlled radiographs revealed pullout of the graft due to contraction of the short head of the biceps on the coracoid graft.]]
 

==What would Codman have thought about this?==
The role of the supraspinatus in dislocation...

CHAPTER IX
THE ROLE OF THE SUPRASPINATUS IN DISLOCATIONS AND FRACTURES OF THE SHOULDER JOINT

THIS chapter does not aim to be an exhaustive treatise on fractures and dislocations of the shoulder, although a very large number of articles have been studied in order to compile it. During the summer of 1928, Dr. T. W. Stevenson reviewed the literature for me, with especial effort to find to what extent the bursa and the short rotators had been referred to. At about the same time, I took advantage of the service of the Library Bureau of the American College of Surgeons, with the request that they find for me all the references they could concerning rupture of the supraspinatus tendon. After a careful search they were unable to find any articles whatever which were devoted to the subject, although occasionally they found references to rupture or avulsion of the tendons in cases of dislocation on which operations had been done.
So far as I know there is no record in the literature of what I call the "Pivotal- Paradox," described on page 43. I, myself, did not understand this paradox when I started to write the book, and only gradually puzzled out its meaning and significance. Certainly none of the authors, who have written on dislocations and fractures in this region, seem aware of the facts that in complete elevation of the arm almost no rotation can occur and that the extent of rotation diminishes as the arm is elevated. The lack of this knowledge of normal functions seems to me to render most of the previous explanations of the mechanism of dislocations and fractures in this region nearly worthless, for several important deductions can be made by the use of these facts. I have consequently eliminated much that I had previously written about the opinions of authorities.
In complete elevation there is only one possible geometric relation of the two units, i.e., the head of the humerus and its tuberosities, with the scapula and its processes. No matter in what degree of rotation you start to raise your arm and no matter in what plane you raise it, the capacity for rotation will be less and less as the arm ascends until, in complete elevation, tuberosities and processes will be locked in a fixed position. In this fixed position the articular head of the humerus will be shown by X-ray in the antero-posterior view, to face nearly outward, and in the lateral view to face somewhat forward, i.e., it actually faces obliquely outward and forward, exactly reversed from its anatomic position. The axis of the condyles of the lower end of the humerus becomes antero-posterior, with the internal condyle pointing forward. The humerus has rotated inward 90° and has become inverted. You may say that the angle between the shaft and the axis of the neck gained 45° by inversion and then 45° by external rotation, or you may say, if you please, it first gained 45° by internal rotation and then another 45° by inversion. Do not proceed with this chapter until you are sure that you have understood this paragraph, even if it is necessary for you to take a humerus in your hand.
The reader must bear in mind that this pivotal position may be assumed by extension of the scapula on the humerus as well as by extension of the humerus on the scapula. For instance, the arm may be in this position when a boxer delivers a telling punch, "putting his body into it." However, the true pivotal position implies that the clavicle is elevated and carried backward to its extreme limit when the arm is elevated to its extreme degree. In other words, the scapula and humerus may move into their share of the pivotal position without the clavicle rising (subordinate pivotal positions), but the arm, to attain complete elevation and the true pivotal position, must be raised to the side of the head.
The scapulo-humeral joint will lock in different positions according to the degree of rotation of the humerus, in a very queer way. (See Figs. 25 and 26.) There can be very little scapulo-humeral abduction with the humerus in full internal rotation; i.e., when the forearm is behind the back, even if clavicle is raised. Starting with your clavicle held down, try elevation of your arm in either internal or external rotation, and then compare the extent of motion when you start with it raised. You will see why authors have differed so much in their estimates of the degree of motion possible in the scapulohumeral joint. To get the maximum you must perform elevation in internal rotation in the sagittal plane or external rotation in the coronal plane; you cannot interchange. These motions cannot be estimated by putting the scapula of a cadaver in a vise, because in life they vary with the relative positions of humerus, scapula and clavicle.
It is as if the secondary humeral joint, limited by the acromion and coracoid, were built with two long sloping sides meeting at an angle above the head, so that when the arm is raised in any plane it eventually comes to rest in the trough formed at the angle of the coronal and sagittal planes and cannot rotate any more. Nature's command is: "Make any combination of elevation and rotation within this enclosure which you wish, but if you exceed these normal limits, you may dislocate or fracture your humerus."

A logical conclusion from these facts is that in whatever way a forward or lateral fall occurs, no strain will come on the scapulohumeral structures until they assume this locked position in complete elevation, provided rotation of the humerus is unhindered as the arm is being elevated. In other words, when the arm is being elevated in mid-rotation in the sagittal plane and arrives at a little above a horizontal position, if inward rotation be prevented, some structure must give, provided the fall continues in this plane. This is exactly reversed in the case of falls in the coronal plane, for when outward rotation is prevented, some break in bone or soft parts must occur. The latter example is the usual one in dislocation and fracture of the head of the humerus.
Let us imagine the same forces applied in another way, i.e., by leverage on the arm when the body is in a fixed position, for mechanically it is the same problem whether the falling patient exerts force on the outstretched arm, or the fixed patient has the same force applied to the arm. Let us imagine the arm thrust into a pipe and force applied to that pipe as in the following diagrams, by lifting its free end up from the plane of the paper- (Fig. 53.)
In making an effort to remember the combinations of rotation and elevation of the arm which may or may not be made, a simple formula is this: evolution has fitted the human animal to fall directly forward on his face with his arm and forearm in almost any position in relation to his body, but, once he has fallen, his arm and forearm cannot be brought much behind the plane of his body in the position in which he lies on his face on the ground, without in some way raising his body.
We may learn a good deal about the shoulder joint from watching the maneuvers of a wrestler endeavoring to turn his opponent from a face-downward position. These maneuvers are essentially the same as those represented in the diagrams above, that is, they depend on getting the flexed forearm in such a position that a little more leverage would break or dislocate the humerus, unless the prone wrestler does permit his body to be raised. Of all the possible positions in which his forearm and arm can be pulled backward, that in which the arm lies at the side will show the greatest backward mobility, i.e., "dorsal flexion."
In lateral falls, when the abducted arm is held behind the plane of the body, the same dislocating or breaking strains that the wrestler endeavors to secure may be produced, the force being supplied by gravity. Moreover, falls will be more violent and sudden, and perhaps catch the muscles when relaxed, instead of having the opposing muscles offer resistance by the voluntary tension which the prone wrestler can assume.

FIGURE 53. LEVERAGES CAUSING ANTERIOR AND POSTERIOR DISLOCATIONS
In interpreting this plate the reader must imagine the arm thrust into a pipe, and he must suppose that the patient's body remains in ironlike rigidity while the outer end of the pipe is raised directly upward from the plane of the paper. Provided the body remained rigid and the tube were raised in this manner, a dislocation of the head of the humerus or fracture must occur. Typical backward or subacromial dislocation would occur in Figures 2, 6 and 7, while subcoracoid dislocation would occur in the other positions.

As in simple frontal falls, so in simple dorsal falls no dislocation of the shoulder will occur, if the arms are free, for we may lie on our backs with our arms in any position anterior to the coronal plane of the body. Even when the dorsal fall occurs with the forearm behind the back or behind the head, dislocation is unlikely.
Thus we reach the conclusion that only headlong, lateral, or semi-lateral, sudden falls can produce the forced elevation combined with prevention of rotation which is necessary to cause anterior luxation of the shoulder joint.
It is possible to conjecture, from a more detailed study of the questions just considered, which forms of dislocation, or varied locations of the lines of fracture, will occur in the shoulder if the lines of force are known. For instance, it is safe to say that only the results of forces applied as in Cuts 2, 6 and 7, in Fig. 53, may result in subacromial dislocation, while all of the others produce subglenoid dislocation.
To express the writer's belief in another way: anterior dislocations of the humeral head occur after the arm has reached the fixed "pivotal position," or more often by prevention of rotation when the arm is at least above the level of the shoulder and the extent of possible rotation therefore greatly diminished; subacromial displacements occur when the arm is below the level of the shoulder and is rotated internally.
This belief is founded not only on the facts already mentioned, but on two others. The first is the remarkable ability of the arm to rotate quickly. Any one who has done any wrestling will remember how elusive were his opponent's arms, unless his elbows were bent, and how easily they slipped out of his grasp as he endeavored to obtain a "shoulder lock." The second is the utter unreliability of the histories given by patients of falls "on the shoulder." The reader is again referred to p. 10. Patients with these injuries almost always say that they struck their shoulders and do not realize that they fell with their arms elevated, i.e., raised to fend off the ground. The inertia of the body is so great as compared to that of the arm, that even in a sudden fall the arm may be thrust forward or outward before the body reaches the ground. A man must already be hugging something, as a football, under his arm in order to fall on his shoulder.
The fact that the arm rotates readily in a safe direction as it is instinctively raised (i.e., raised in relation to the scapula, although pointing downward) during a fall, means that subconsciously the arm will usually reach the relatively safe pivotal position. Meantime the palm meets the ground and the force becomes disseminated to the various ligaments, muscles and bones of hand, wrist, elbow, shoulder and back, each in turn breaking the fall until the final bony lock in the pivotal position brings the stress to a limit. Even then the pec-toralis, the teres major and latissimus, and finally the clavicle, may still further disseminate the stresses. But notice that in this elevated position the lines of force of these muscles converge toward the glenoid, so that they are not, in this position, functioning as rotators as they do when the arm is at the side. The higher the axis of the humerus the more their power is exerted toward the face of the glenoid in their effort to avert the leverage of the shaft from gaining a fulcrum on the acromial edge. However, while they are in use in fending off the ground, the pectoralis and latissimus are acting also as strong internal rotators. This is the period of danger (Fig. 55), for the pivotal position, once reached, means safety, unless the downward factor in the fall is great. When the arm is in the pivotal position, the broad tendon of the latissimus actually covers the unprotected axillary portion of the capsule and tends to prevent the head from dislocating, although the pull of this muscle is in the main downward. In this position the long head of the triceps, the teres major and the latissimus actually form a support for the lower half of the capsule.

FIGURE 54. ACTION OF PECTORALIS MAJOR IN DISLOCATION
This diagram pertains to the discussion of whether the pectoralis major and latissimus dorsi should be regarded as furnishing a fulcrum in case of fracture of the upper end of the humerus. The contention is made that the pull of these muscles not only does not act as a fulcrum, but to some extent relieves the strain on the surgical neck, by pulling the tuberosities away from the true fulcrum which is the acromion. If these muscles acted as a fulcrum, the power would be applied on the glenoid and would immediately rotate the whole scapula, so that the acromion would become a fulcrum. The writer holds that in such accidents there can be no disruptive force in the region of the head of the humerus unless the acromion does act as a fulcrum.
The diagram further illustrates the fact that the power of the supraspinatus is applied in such a manner as to restrain dislocation, but that in forced elevation of the arm the upper edge of the glenoid acts as a wedge driven in between two points of application of strain. This idea is amplified in Plate IX.

Many authors have contended that besides the obvious bony fulcrums which occur, there may be others momentarily maintained by contracted muscles, which may lead to fracture or dislocation. Perhaps this is true, but I have been able to work out few such mechanical positions. For instance, the lever formed by the humerus when the arm is in the anatomic position, the pectoralis and latis-simus contracted, and outward force applied at the elbow, may be considered either to have its fulcrum on the glenoid or to apply power there, with the pectoralis, etc., as a fulcrum. The latter might be the proper way to consider the problem if fracture occurred in the long arm of the lever, distal to these muscular attachments. It seems more logical to me to regard the applications of muscle pulls as forces acting on the obvious bony fulcrums. However, there can be no doubt that when these muscles are contracted they would tend to prevent outward rotation of the humerus.

FIGURE 55. TRAJECTORY OF CENTER OF GRAVITY
The center of gravity of a person in falling necessarily always has a trajectory formed by the momentum with which he falls forward, combined with that with which he falls downward, and that which is exerted in relation to the median plane. The writer contends that in most instances, dislocations and fractures in the region of the upper end of the humerus take place when the trajectory meets the ground at or posterior to the point of impaction of the elbow, and also internal to this point. If the trajectory came far anterior to the point of the elbow, the arm would be folded to the side, or if it came far posterior to the point of the elbow, the arm would extend harmlessly beside the head. If it came near the median plane or to the opposite side of it, the arm would slip outward into the hammock position. It therefore seems highly probable that most of these fractures happen when the arm is internally rotated by the pectoralis, etc., and the fall is of such a sudden and violent character that the humerus does not have time to rotate.
If the vertical factor in the trajectory were great so that the patient was falling nearly straight, head downward, fracture or dislocation in the pivotal position would occur. The writer believes that in every case there is acromio-humeral contact, and therefore always a subordinate pivotal position (see Fig. 25).

I am not in sympathy with the view of those authors who hold that the contracted pectoralis and latissimus act as a fulcrum to promote dislocation or fracture of the head of the humerus. I think the reverse is true, so far as their adductor action is concerned, for I am convinced that this action merely tends to prevent dislocation, since the force is applied to the long arm of the lever distal to the true fulcrum which is the acromion.
Lack of space prevents elaboration of the following additional reasons which support this conviction.

The directions of the majority of the fibers of the pectoralis
major suggest that -their contraction would bring the head toward
the glenoid from the very start of elevation, i.e., they would directly
oppose dislocation.
In other words, the lower fibers of the pectoralis are inserted higher on the humerus than the upper fibers; thus all fibers of the muscle tend to pull in a line away from the acromion as a fulcrum while the arm is being raised.
The combined power of the adductors would not be enough to break the humerus, if both ends of the latter were fixed. Therefore, their power would not be enough to act as a fulcrum for a fracture in the short arm of the lever, although it might be sufficient in the long arm.
Even if the power on the long arm of the lever'acting through the muscles as a fulcrum, became applied to the glenoid and to the supraspinatus and other opposing muscles, the result would merely tip the scapula so as to apply the acromion as a fulcrum.
Until the acromion became a fulcrum no disruptive force could take place between the scapula and humerus.
If the humerus touched the acromion at all and the pectoralis, etc., applied their power exactly opposite this point, the leverage exerted on the glenoid would not be changed in any way; nor would it be changed much if the point of application were moved a little away from the neutral point on the long arm of the lever. However, that slight change would diminish rather than enhance the tendency to dislocation.
The X-ray shows close apposition of acromion and humerus, when the arms are akimbo, in the salute position and in complete elevation.
The acromion is always the fulcrum, although in the above positions different parts of the acromial edge come in contact with different parts of the circumference of the humeral head. (Fig. 25.)
Although I believe that the pull of the pectoralis and latissimus actually help to prevent dislocation by their action as adductors, I am strongly of the opinion that as internal rotators they actually help to promote dislocation. The reasons may be briefly stated a& follows: On account of the position of insertions of their tendons, to be adductors, they first have to be internal rotators. As adductors they do their best to fend off the ground until the last possible moment when the acromion has begun to be a fulcrum. Meanwhile, as internal rotators, they are drawing the arm into a subordinate pivotal position and thus prevent external rotation, which is the only method of escape for the arm if it must rise in the coronal plane. Thus we can conceive of their having power enough to keep the humerus internally rotated until it is too late for it to turn, although we cannot conceive of their being able to act as direct adductors strongly enough to withstand the falling weight of the body. If, in any case, they instinctively relax in time for rotation to occur, the arm will rise to the side of the head and no harm will have been done. Occasionally, however, the relaxation is too late, or vice versa, the violence is too sudden, and the arm will be caught in internal rotation in or near the coronal plane. It will then be too late for the adductors to relax in order to let rotation occur and thus permit the arm to ascend by the head.
The nearer the bent arm, in internal rotation, lies to the sagittal plane the safer it will be; the nearer the externally rotated arm lies to the coronal plane the safer it will be and vice versa. As a matter of fact, in healthy youth it is astounding how rapidly this instinctive rotation will occur. The football player may be hurled headlong by impact with other players in such a way that his body may be twisting laterally as it falls, yet his outstretched arms fend off the ground just long enough to prevent his breaking his neck, and in spite of the sudden, twisting violence, rotation at the last moment usually avoids dislocation of the shoulder.
Yet occasionally the resultant of all the forces of the fall makes the trajectory of the center of gravity strike posterior to the point of the elbow and to its inner side, while the humerus is internally rotated, and anterior dislocation will occur.
If the reader wishes to go into this in more detail he may force his mind to project a combination of Figures 26 and 55. It is difficult enough to visualize the normal workings of the shoulder joint, but it is still more difficult to foretell the results, on this beautifully adjusted apparatus, of a fall downstairs. Yet I think these general principles usually apply.
On the supposition that our conclusion that the humerus must obtain a fulcrum on the acromion in order to exert a disruptive force to produce dislocation is correct, let us consider what occurs in the inner unit of the shoulder, Figure 8, Chapter I.
The fulcrum on the edge of the acromion obtains its skeletal support, whatever the position of the arm, directly through the clavicle to the sternum. As has been said, not only is upward dislocation of the acromio-clavicular joint prevented by the fact that the clavicular portion of it is superior, but by the strong coraco-clavicular ligaments. Thus the clavicle in any position furnishes a strong radius through which the pressure on the fulcrum is firmly sustained. Moreover, the S shape of the clavicle has been shown to not only withstand great pressure in a line between its two ends, but to have great elasticity when the pressure is released.
I wish to accent again three characteristics of the scapulohumeral joint.

The capsule is necessarily loose.
The upper half is muscular and strong; the lower half is fibrous and weak.
Since the humerus can rotate many degrees (probably 100+) without moving the scapula, any one of the short rotators may receive the chief burden of the strain according to the degree of rotation when the acromion becomes the fulcrum. The following remarks will be based on the supposition that the supraspinatus is uppermost, as in Fig. 9, but would apply equally well when any of the other rotators were directly opposed to the force moving the elbow.
As the elbow rises upward not only is the supraspinatus contracted but the upper edge of the glenoid becomes a wedge in the reentrant angle, between the articular cartilage and inner surface of the supraspinatus. This accounts for the frequency with which fracture of the tuberosity accompanies dislocation. In most cases not only the facet on the tuberosity for the supraspinatus will be carried away, but also a concavo-convex piece of bone comprised of the greater tuberosity and part of the lesser, and extending down to the point where the humerus touches the acromion, and including even the bicipital groove as a whole with its tendon intact. (See Plate IX.)
If the force goes no further we shall have a false dislocation, for the lower part of the capsule being loose and there being no support above, the head will glide over the lower edge of the glenoid and fall into the lower part of the capsule, stretching it downward. Correspondingly, the dislocation will be at once reduced as the arm falls to the side, for it will not be pushed through a hole in the capsule and thus have an impediment to easy reduction.

PLATE IX. FRATURES OF THE TUBEROSITY AND FALSE DISLOCATION
The mechanism of fracture of the greater tuberosity and its relation to false and true dislocations.
a. The pivotal position.
6. When leverage is exerted against the acromion as a fulcrum, the biceps tendon guides the upper edge of the glenoid to enter the sulcus as a wedge, thus tending to chip off the tuberosities. This wedge is not a point but the curved edge of the fibrocartilage backed by the rim of the glenoid.
c. The inferior extremity of the fragment is therefore at the point of impaction of the acromion. The biceps tendon, tuberosity and subacromial bursa remain in their normal relations. A false dislocation of the head may then occur without rupturing the lower part of the capsule because tension is relieved by the rent in the upper portion. The lower part of the capsule, which is normally capacious, will be merely carried beneath the glenoid, as the arm descends.
d. The same lesion with the muscles depicted. A portion of the subscapularis still remains attached to the lesser tuberosity, but most of the greater tuberosity, and part of the lesser, remain in Continuity with the fragment.
e-f. Schematic drawings to illustrate the difference between a false and a true dislocation. False dislocation must necessarily be accompanied by rupture of the upper portion of the capsule, together with fracture of the greater tuberosity or rupture of the tendons. There is no structure except possibly the biceps tendon likely to interfere with its replacement, but in a case of true dislocation where the lower part of the capsule alone gives way, the sides of the capsular rent would tend to become tight around the neck of the bone, when efforts are made at reduction. In the worst cases where the two forms are combined an operation is required.
It seems as if some cases must occur in which the biceps tendon would be freed because the line of fracture might extend down the groove and the tendon would thus be separated from the greater tuberosity, and lie between the fragments. I think it usually remains in contact with both fragments if it is not evulsed from the glenoid by the same violence, in which case it retracts into the groove.

This I believe to be the mechanism in most cases of fracture of the tuberosity, whether the accompanying dislocation is recognized or not. On the other hand, both the bone and the supraspinatus attachment may hold in whole or in part, and be stretched down over the glenoid, until the lower portion of the capsule is tensed and torn and permits the head to slip through it and remain subglenoid, with the torn capsule tense on each side of the surgical neck. This will be the ordinary uncomplicated true dislocation.
Violent falls may produce a combination, first wedging off the tuberosity and then driving the head through the lower capsule.
Other variations may be:
1. Instead of the whole tuberosity being wedged off, the supraspinatus may tear away only the facet of insertion.
2. Evulsion of the supraspinatus at the blue line may occur.
3. Rupture of the supraspinatus may take place just above the palisades.
4. Very rarely a lip may be pried away from the lower edge of the glenoid instead of having the capsular attachment give way. I suspect that this is more apt to occur when the forearm is very much rotated internally and the arm is akimbo.
5. Rupture of the long head of the biceps may accompany true or false dislocation, or any of the above variations.
In general, in types 1, 2 and 3, we may expect additional tearing either toward the side of the infraspinatus or toward the side of the subscapularis, according to the degree of rotation of the humerus on the scapula at the time of the fall.
These are the very obvious lesions which may occur, but I believe the most common complication to be the " rim rents " described in Chapter V, which occur not only with dislocation, but in many cases where these structures are just able to resist dislocation, although the synovia becomes separated from the articular margin and a few inner fibers of the tendon are torn.
Another factor which may resist dislocation remains to be considered—the atmospheric pressure which holds the bursal surfaces together. In the typical false dislocation with fracture of the tuberosity, I do not believe that the relations of roof and floor of the bursa are destroyed. Until air is let into the bursa the surfaces tend to remain in contact. Many a time I have demonstrated this on the operating table. The same is true of the joint. To test in actual pounds the degree of pull required to separate these surfaces remains for some future observer. I feel confident that many pounds of direct pull would be required in the living to separate either bursa or joint to any great extent unless fluid is present. Even when the bursa is opened one cannot pull the joint surfaces apart without undue force unless the supraspinatus is torn, when they fall apart as soon as the air enters. The surface area of the bursa and that of the joint must be very nearly the same, roughly two inches in diameter, each. In X-ray tests one must remember that the cartilages do not show and that the presence of fluid permits separation.
A thorough understanding of what has been said in the preceding pages of this chapter is so important that a summary seems necessary at this point.
1. In spite of the usual histories which patients give of striking on the shoulder, the cause of dislocations or fractures is rarely, if ever, direct, but is usually a backward or downward (i.e., backward and downward in relation to the body as the patient falls) force, acting in the pivotal position, or in a subordinated pivotal position, through the humerus as a lever, with the acromion as a fulcrum, and the weight represented below by the lower portion of the capsule supported by the triceps, latissimus and teres major, and above by the resistance of the supra- and infra-spinatus, the long head of the biceps, and the atmospheric pressure in joint and bursa.
2. During a fall, unless the elbow is maintained in flexion, rotation of the humerus readily occurs; but since no lateral motion at the elbow is possible, fixation of a flexed forearm in a given position may greatly alter the direction of force applied at the shoulder, so that dislocation might occur at a point in elevation short of the pivotal position, but usually above the horizontal. For example, a lateral fall in the coronal plane when the humerus is held in internal or mid-rotation, in such a manner that external rotation is prevented (as by contraction of the pectoralis major), or a somewhat headlong fall in the sagittal plane while internal rotation of the forearm is prevented, might result in fracture or dislocation.
3. It is very unlikely that forward dislocation ever takes place unless the fall is at least somewhat headlong, i.e., one in which the elbow strikes a point anterior to the trajectory of the center of gravity.
4. In most instances subglenoid dislocation must be at first momentarily erect. The descent of the arm into the sling position, in which we usually find it, will be in internal rotation with the head of the humerus still displaced below and anterior to the glenoid, with the subscapularis relaxed and the other short rotators stretched over the glenoid. The long head of the triceps will be between the teres major below and the minor above, and the articular surface of the humerus will face backward on the origin of the long head of the triceps.
5. It seems probable that backward or subacromial dislocation never takes place from forces operating on the arm when it is being elevated, but must occur below the horizontal when the humerus is only abducted to a sufficient degree to permit the flexed forearm to be forced backward behind the body in internal rotation. Vice versa, anterior dislocation usually occurs only when the arm is above the horizontal, although theoretically, if the elbow were at the side and the humerus were rotated outward by the flexed forearm, anterior dislocation might occur from a sudden lateral fall which forced the forearm in external rotation behind the body. This would be a very unnatural way to fall, however.
If we accept the above explanation of the mechanics of dislocation, we may proceed to speculate on the reasons why fracture instead of dislocation often occurs from exactly similar falls. Age seems to be the determining factor, but this factor may be subdivided into two secondary ones, i.e., the relative tensile strength of the structures at different ages, and the relative mobility of the bones in youth and in age.
Assuming stress in the pivotal position:
In early youth the humerus ascends high under the acromion, and as the epiphyseal line is relatively the weakest point, epiphyseal separation will probably occur.
As a rule, in youth and manhood after union of the epiphyses, tendon and muscle and bone are strong relatively to the lower portion of the capsule, so that dislocation will take place. If any fracture occurs it will usually be at the greater tuberosity. Occasionally it will occur at the surgical neck.
In old age the trabecular structure about the base of the tuberosities will be weak; therefore, comminuted fracture will readily occur. If the bone holds, dislocation will usually be accompanied by rupture of the supraspinatus, for the muscles and tendons will be weak and cannot disseminate the force.
The second factor, i.e., the extent to which the head of the humerus may pass beneath the acromion, is also important in determining the seats of fracture in youth and in age.
In childhood the tip of the acromion is soft and cartilaginous, and thus the stress on the bony portion of -the acromion would be met at about the epiphyseal line, although the head of the bone passes far beneath the cartilaginous acromion.

FIGURE 56. EPIPHYSES OF A CHILD'S SHOULDER BONES
Outline drawing from X-ray of child with both arms elevated. By use of a dotted line the figure on the left is made to appear as an anterior view while that on the right appears as a posterior. At this age the tip of the acromion is pure cartilage and does not appear in the film. Notice that the head of the humerus passes beneath the acromion just far enough so that the bony portion of the acromion would gain a point of impact very close to the epiphyseal line. The cartilaginous tip would bend and the breaking force would occur at the epiphyseal junction.
This figure also shows that the line of epiphyseal union of the coracoid is at its base. I have never recognized a separation of this epiphysis. My work has been such that I have seen comparatively few injured children, but I think that it is quite possible that this lesion does occur, and may be detected by characteristic symptoms. It is certainly one of those conditions which we should expect on purely mechanical grounds.

In youth the tuberosity also passes far beneath the acromial edge, and this will bring the fulcrum to bear low down on the surgical neck, just above the attachment of the powerful pectoralis major. Usually dislocation will occur with or without fracture of the tuberosity. Occasionally the surgical neck will give way at the fulcrum.
In the stiff, aged joint, the tuberosity will barely pass beneath the acromion, and impact of the latter will come at the point just below the tuberosities, where the cancellated bone is weak, so that comminuted, intracapsular fracture will usually occur.
It is likely that there may be some changes in the exact lines of these comminuted fractures according to the degree of rotation which the humerus attains at the time of fracture. That is, the acromion will be applied at quite different points on the tuberosity in external and in internal rotation.
Other factors may be important also. For instance, the rapidity of the application of force; the degrees of contraction of the various muscles; congenital or habitual variations in the structure or position of the bones and of other tissues; the weight of the body; many minor circumstances or unusual combinations of any of the above factors. However, the point I wish to make is that the pivotal position is to the human arm in its varied activities as his earth is to the fox. The elusive arm must be driven to its pivotal position to be caught, or tricked by preventing rotation on the way. With continued effort we may always dig the fox out, and with continued backward force we may always break or dislocate the head of the humerus,, although the human arm is as clever in evasive rotation as the fox is in doubling.
There are many other points on which a consideration of the "Pivotal Paradox" is enlightening and which are worthy of study, for a thorough understanding of the mechanics of dislocations must be of help in their diagnosis and treatment. However, it will require many studies by many people before practical experience will cease to be our guide. Whether the deductions I have made above prove to be right or wrong, the following practical facts support them and are confirmed by all writers and by each surgeon in his own experience.
The causes of anterior dislocations are usually headlong or lateral falls with the arms thrust forward to fend off the ground.
The same kinds of falls may also produce the following lesions of the upper end of the humerus:

(1) Separation of the humeral epiphysis.
(2) Fracture of the surgical neck.
(3) Fracture of the tuberosities.
(4) Fracture of the anatomic neck.
(5) Comminuted fractures in which the typical form consists of four fragments; i.e., the two tuberosities, the anatomic head, and the shaft. (See Fig. 60.)

Any of these forms may be complicated by concomitant dislocation of the articular head, whether or not it remains attached to the shaft.
The fractures will be discussed in the next chapter and dislocations in the remainder of this one. However, the two subjects are inseparable and one should realize that both fracture and dislocation occur in many cases which are classed as either lesion. I am inclined to think that a combination is the rule, especially in cases of fracture of the tuberosities, and that many supposedly simple fractures are accompanied by false dislocation of the head which immediately becomes spontaneously reduced. Previous dislocation is evident in cases of complete separation at the anatomic neck in which the head remains displaced, but unless the latter is completely separated, it will be dragged back by the tuberosities, which are rarely dislocated because they are sucked back by the bursa and almost invariably remain attached to the short rotators. In other words, these tendons may rupture without the occurrence of any bone lesion, but if one does occur, the tendons remain attached to the fragment. Only small crumbs of the tuberosities ever become really free even in the most comminuted fractures.
The number of shoulder injuries compared to the total number of industrial accidents reported in Massachusetts during eight years is shown in tabular form. This table is not perfectly accurate, so far as the figures on dislocations and fractures are concerned, because it was not arranged for the particular purpose for which I am using it. For instance, all fractures of the clavicle and all fractures of the humerus are included because no distinctions had been made as to the part of the bone injured. It is probable, therefore, that the number of dislocations is fairly exact, but that the number of fractures of the upper end of the humerus is considerably less than the figure given, and probably in every year less than the number of dislocations. Probably many of the cases which were classed as fractures also had dislocations and vice versa. Although there is a striking tendency toward uniformity of the numbers through the different years, the proportion of dislocations to fractures varies somewhat for the above reasons. It is fairly safe to say, however, that about one-fifth of all shoulder injuries occurring in industry are fractures or dislocations of the upper end of the humerus. It is likely that if we could get similar statistics from the population not engaged in industry, fractures would be more common than dislocations, because fractures in this region usually occur in elderly people. Unfortunately, there can as yet be no statistics to determine how often the supraspinatus is injured as a complication of these so-called major (?) injuries, nor what proportion it forms of the other injuries which are unclassified. I believe that it costs our community more than all the other lesions together, not only because it is so common as the major lesion in fractures and dislocations, but because there are many unrecognized minor cases.

The shoulder is the most frequently dislocated joint in the body. This fact is quite properly generally ascribed to its relative instability. Dislocation of the humerus occurred 108 times in 528 cases of dislocation reported by Eliason, and it has been stated by various authors that forty to sixty per cent of all dislocations are of the shoulder. Many shoulders are probably dislocated and immediately reduced by the patient or his companions as they lift him after a fall, without knowledge that dislocation has occurred.
Dislocations of the head of the humerus have been classified in several ways, although for practical purposes only two classes are of importance, i.e., the forward or subcoracoid, and the backward or subacromial forms. As the latter are rare, "dislocation of the shoulder" usually refers to the former.

The first four varieties in the table are essentially the same. If the tear of the capsule and stretching of the muscle bellies away from their beds-are extensive, the dislocated head can be moved easily from a subglenoid to a subcoracoid or to even a subclavicular position. As has been shown, the erect subglenoid position probably occurs in every case momentarily, as the patient falls with the upraised arm, although depression and internal rotation at once ensue from muscular contraction, causing the arm to assume the position at the side in which we usually find it. Very rarely does the erect phase last long enough to be classified!
Subspinous is merely an extreme degree of subacromial dislocation. It occurs when the infraspinatus has been badly torn from its bed so that a large space under the spine of the scapula accommodates the displaced head. Upward dislocation implies an accompanying fracture of the acromion and is nothing more than a curiosity in extremely severe accidents. I have never seen it.

DIAGNOSIS OF ANTERIOR DISLOCATION

In simple subcoracoid dislocation of the humerus, the well-known signs are as follows:

History of a trauma to the shoulder in which something was felt to give way and a severe, acute, nauseating pain was experienced.
Active and passive movements are limited and painful.
The forearm is held flexed and internally rotated.
The elbow is away from the side and cannot be completely adducted, thus causing the long axis of the shaft to incline upward and inward.
Patient stands inclined to the affected side so as to bring the axis of the humerus to a vertical position.
Measuring from the acromion to external epicondyle, the upper arm appears lengthened.
The anterior axillary fold (on the affected side) is lower.
The shoulder is flattened.
The acromial process is prominent.
The head is palpable under the coracoid.
A soft crepitus can be elicited while manipulating the shoulder.
In other words, the facts to be learned from the history, inspection, palpation, motions and mensuration, plus the aid of the X-ray, will usually make the diagnosis beyond doubt. In fact, the diagnosis is generally so obvious that we must be on our guard not to overlook concomitant injuries and complications. While examining the patient one should take especial note of the circulation of the arm, and of the sensitivity of the skin over the arm and shoulder. The power of the deltoid, rhomboids, clavicular part of the pectoralis major, supraspinatus and infraspinatus, etc., should be carefully noted with a view to detecting paralysis. When the case is typical, the eleven signs are exceedingly plain, but this does not mean that when they are absent there is no dislocation.

It is very important for the reader to understand that all of the above signs, except the first and the last, fail when the articular head has been replaced on the tuberosity, which has itself been displaced into the glenoid. At this point the reader should refer to the history of Case 71, page 288, and study the accompanying diagrams. Our mistakes in diagnosis will occur in these cases where the head of the humerus can hardly be said to be out of place, but is certainly not in place, for the short rotators with the evulsed facets lie between it and the glenoid. (Fig. 58 and Case 115, p. 389.)
The second symptom was absent in Case 115 because the nerves were paralyzed or so retracted as not to be influenced when the arm was moved. The replacement of the head to nearly its normal position had completely removed the third to tenth symptoms and even the eleventh symptom, in this particular case, was absent or very difficult to detect.
Of course, such cases of pseudo-reduction are not common, but they occur now and then, so that we must never fail to bear in mind that cases of dislocation which are not quite satisfactory may become extremely unsatisfactory, if the supraspinatus or other short rotators are torn, or have dragged the facets toward the glenoid.
Treatment. The main therapeutic principles are: reduction, fixation and gradual return to function.
Reduction in most cases can be obtained by the Kocher or by the Astley Cooper traction methods. These procedures are too well known to describe in this text. The Kocher method is most generally used because much less force needs to be exerted, and hence less trauma should occur during the reduction. However, as Kocher himself said in his original article, it does not always work and it is sometimes necessary to use the Astley Cooper method.
Much has been said concerning the optimum position in which to maintain reduction. This would seem to suggest that the ideal position had not been found. Some modern authors, notably Stevens, are of the opinion that the arm should be put up in abduction and external rotation.
A simple way of obtaining abduction and external rotation is to put the patient in recumbency, and fasten the hand to the head of the bed. A suitable ambulatory splint can be used, or both methods in conjunction. A splint maintaining abduction and external rotation is cumbersome, and attracts a great deal of attention. The ordinary airplane splint abducts, but internally rotates the arm. Abduction and external rotation put the patient in the position of a traffic officer stopping a line of cars. The writer does not advocate this abduction treatment, and prefers not to fix the arm at all.
The advocates for maintaining the arm in the sling position after reduction, contend that the torn capsule heals better because it is relaxed. This seems reasonable, unless the rent is longitudinal, in which case its edges would be approximated better in abduction. It has never been determined positively whether rents in the capsule are usually longitudinal or transverse. Some writers claim that the capsule is torn from the forward edge of the glenoid, and my opinion is that this is the usual condition, for this only means the tearing of the pillars which form the opening of the bursa subscapularis. More observations of cases where death has occurred from the same accident as that which dislocated the limb are much needed. If we knew in general how the capsule is usually torn, the answer to the question of whether to maintain adduction or abduction would be much more plain.
The writer believes that at present there is too great a tendency to confine the arm after reduction. It would seem more logical to let the patient use his arm a little—even to urge him to do so, in order that debris and blood clot may work out of the joint capsule into the areolar tissue, where they would be readily absorbed. If the capsule were emptied of the blood clot, it would seem that it would be more likely to have its edges fuse together again without leaving any distortion or undue irregularity. On the other hand, I believe that motion should not be forced for fear of tearing edges which are beginning to unite. For those who think this policy too radical, it would be safer to treat most cases in the sling position than in the abducted one, unless the surgeon were very well versed in the study of the shoulder joint. I think stooping exercises should be begun at once and continued daily in any case. We should use fixation only for comfort, and this means very little, for one may be sure that if there is severe pain after reduction some complication exists.

Prognosis. It would seem an easy thing to make a prognosis in cases of dislocation, but as will be seen shortly, complications are frequent, often unrecognized, and greatly modify the period of disability. A fair prognosis in uncomplicated cases would seem to be a return to normal function in from four to eight weeks. However, complications are, I am sure, more frequent than is generally realized.

FIGURE 57
X-rays of the case alluded to in the text in which the articular head had become displaced beneath the deltoid and was excised through a sabre-cut incision. This patient recovered with a useful arm, and was able to play excellent golf for many years afterwards. Undoubtedly fracture and dislocation occurred at the same time, and the head was left behind in the erect phase of dislocation, when the arm came to the side. The articular surface remained in nearly the position which it occupies in normal elevation. It seems possible that if this fact is recognized in similar cases, reduction might be accomplished by again placing the shaft in elevation, opposing the raw surface of the articular head to that of the tuberosity, and holding them together while the arm is brought to the side in the coronal plane.
Figure a, before operation.
Figure b, a few months after operation. The acromion, which had been sawed across for the sabre-cut incision, has been wired about two steel pegs.
Figure c, taken nineteen years later, when the patient was eighty. There had been no trouble from the wire or pegs in the intervening years. At this time motion in the joint still persisted, but "was very limited in degree. However, it was sufficient to permit a slight amount of abduction and rotation, which permitted him to use his arm freely for ordinary purposes. Although this operation was successful in restoring a fair degree of usefulness, if I were obliged to operate again for such a condition I should not remove the articular head, and would endeavor to reconstruct a normal joint, perhaps employing Dr. Nicola's suggestion of anchoring the articular head by means of the biceps tendon. Before incising, I should hyperelevate the arm in internal rotation in order to appose the fractured surfaces.

Gubler, in a study of insurance records of 252 workmen's compensation cases, states that recovery occurred in 94.1% of the cases after an average of thirty-eight days of treatment. Another investigator, Kuttner, reports a far different experience. He was able to trace fifty-four uncomplicated cases from among 168 treated during the previous five years. Only seven (13%) had regained full use of the limb without loss of strength or motion. In fourteen (26%) the range of motion was complete, but the strength was reduced one-half or more. The remaining thirty-two (61%) had some loss of motion, which in twenty-six amounted to inability to raise the elbow laterally above the level of the shoulder. He states that all of these cases were uncomplicated (which we doubt), and had been treated in the hospital by immobilization for a week, followed by massage and mechanotherapy for two to three months. Goebel reports similar unfavorable results on twenty-four patients. Twelve had full function, but subjective complaints. Twelve had limitation of motion. Lexer reports forty cases; ten with complete restoration, fifteen with some limitation, fifteen with pain and loss of strength.
These reports are self-explanatory, and coincide with my observation of results obtained in general hospitals. The conclusion is that most of these patients received other injuries at the time of the accident or during treatment. I believe that uncomplicated cases tend to recover in about four weeks, unless interfered with by injudicious treatment, such as prolonged fixation.

Complications. Injuries to other structures about the joint are common and students should be most thoroughly warned of this fact. It is not so much that these complicating lesions are difficult to detect at the time of the first treatment, but that they are not suspected. It is a fact that these complicating lesions do often exist and do maintain disability and pain long after the joint itself has returned to normal, yet there is no organized effort of our profession to correct this condition. Industrial cases may be labelled malingerers, psychoneurotics, hysterics, or cases of traumatic neuroses, because of this prolonged disability with few detected physical signs. The five common complications of dislocation are the following:

Fracture of tuberosities.
Avulsion of the facets, or rupture of the tendons.
Fracture of the glenoid rim of the scapula.
Injury to the brachial plexus.
Rupture of the axillary artery or of other vessels.
Fracture of the greater tuberosity has hitherto been thought to be by far the most common injury accompanying dislocation. Graessner found the greater tuberosity broken twenty-four times in forty-eight dislocations, but in many of them the fragment was only a small scale of bone, indicating an avulsion of the tendon. Delbet found it in twenty-two out of one hundred and ten cases. Dollinger in five out of thirty-nine. Goebel twenty in forty-three cases. Schlaepfer found it eight times in one hundred and twenty cases, or 7.4%. Gubler reports it in eighteen out of two hundred and fifty-two cases, or 7.1%. Gubler also reports ten cases of other bone injury, and ten of nerve injury in his series. In my opinion, many of the cases where only a small facet is torn away should be classed with supraspinatus injuries rather than with fractures of the tuberosity, because they result in free communication between the joint and the bursa.
The bone injuries are generally easy to diagnose if looked for. The typical signs of fracture, especially ecchymosis down the arm along the biceps, are usually present and the X-ray is of great assistance. The real difficulty is too great a tendency to treat the major abnormality, the dislocation, and to overlook very important, but less obvious, injuries. Sometimes failure to recognize complications is due to careless X-ray examination, but more often to the inexperience of the doctor who first treats the patient. Rupture or avulsion of tendons attached to the tuberosities should be suspected when the films are negative.
The injuries to nerves and arteries will be considered in Chapter XI.

REFERENCES OF AUTHORITIES TO THE ROLE OF THE SUPEASPINATUS
IN DISLOCATION

Little is to be found in the literature to confirm my beliefs or to explain why the short rotators come to be so frequently injured. Only a few writers have realized the frequency of such injuries, and I do not think that any" of them have appreciated the significance of the fact that the bursa and joint are thus put into communication.
Stimson says that the supraspinatus is sometimes, probably often, torn from its attachment to the humerus, and the same is true in less degree of the infraspinatus, and occasionally even of the teres minor. He states also that avulsion of the tuberosities may take the place of laceration of the tendons. Preston says that injury to the capsule is not infrequently accompanied by injury to the tendons which overlie and reinforce it, and when the violence producing the luxation is great, there may be a destruction of tendon continuity.
Stevens gives an excellent description of shoulder dislocation with especial reference to the short rotators. According to him, an anterior dislocation is an impossibility without putting a strain upon the tendons of the supraspinatus, infraspinatus and teres minor. With the humeral head in subcoracoid dislocation, the distance from origin to insertion of the supraspinatus is greatly increased, and in addition the tendon is angled over the rim of the empty glenoid. Similarly the posterior rotators are pulled over the posterior rim of the glenoid, and are almost always injured. "We may," he says, "assume that in every case of dislocation of the humerus, and especially in anterior dislocation, there is an injury to the tendon of the supraspinatus, and that often it is ruptured."
Very few other authors even allude to this tendon.
The following cases as well as the above quotations from the literature support the assertion that the facet of the supraspinatus may be torn off in dislocation.

CASE REPORTS

No. 12. Mr. A. F. K. Age 45. Massachusetts General Hospital No. 174082 W. S., Jan. 23, 1911.
A subcoracoid dislocation of four months' duration. Open reduction of dislocation. Supraspinatus was found retracted with facet of insertion. Heavy silk sutures to unite it with tuberosity. Feb. 24; 1912: An excellent functional result, but scar is ugly.

No. 22. Mr. J. H. D. Age 69. Massachusetts General Hospital No. 182238, April 22, 1912.
Five weeks ago fell, injuring right shoulder. Reduced by M.D. Went back to work. One week ago dislocated it again when drunk. I made an unsuccessful attempt at reduction in the Accident Room, and then carried the patient under ether to the operating room, and through the usual incision for the bursa I opened directly into the joint. A defect corresponding to the facet of the supraspinatus was found, the supraspinatus being retracted under the acromion. There was no piece of loose bone corresponding to the defect, although the whole joint was carefully searched. It must therefore be assumed that the loose piece had been absorbed. The dislocation was reduced, supraspinatus reinforced with silk and the wound closed. Two years later he wrote me: " I can do quite a lot with it, only when I reach overhead it gives way and causes some pain."

No. 71. Mrs. E. C. Age 68. On June 10, 1921, fell downstairs, broke left wrist and dislocated left shoulder. Ether was given by the local doctor, and he supposed he had reduced the dislocation. She consulted me on August 9, 1921, and after taking X-rays, I reported to the physician who had sent her to me that I thought that the shoulder joint had been reduced. The accompanying X-ray seemed to me to show that the bone was in place. I know now that this appearance is deceptive. In such cases as this, the tuberosity has been retracted into the glenoid and the head of the humerus rides on it. Therefore, there is not very much change of contour in the position of the shoulder, because the total amount of bony substance between the tip of the shoulder and the glenoid is the same, although the position of the tuberosity is reversed and lies in the glenoid. The following is an account of the operation which I did on April 5, 1922, nearly a year after the injury.
Sabre-cut incision. Prominent anterior mass proved to be head of humerus minus the tuberosity. The tuberosity had been retracted by the posterior short rotators and lay partly in the glenoid cavity and partly overlapping its posterior margin. The biceps tendon was displaced so as to lie between the head of the bone and the glenoid. It was excised. The retracted tuberosity was also excised. The synovial and tendinous capsule of the joint was completely gone, except at the anterior edge, namely, the portion formed by the subscapularis tendon. A good, practical result was obtained, i.e., a movable, painless, weak shoulder, lacking power in abduction, but more useful than a painful joint.

It is my belief that in most of these cases of dislocation where the X-ray shows a portion of the tuberosity to be absent, careful pictures will show its presence in the glenoid or just below the glenoid. The capsule forms a pouch below the glenoid and this pouch catches the smaller fragments if they have become loose. The cases are deceptive because a reasonable amount of motion may be found within the first few weeks and the position of the head is so nearly normal that it is not realized that the head does not actually touch the glenoid.

FIGURE 58. THE USUAL CAUSE OF FAILURE TO REDUCE A DISLOCATION
Mrs. E. C.— X-ray (a) before the local doctor attempted reduction. The fragments of tuberosities may be seen external to the lower edge of the glenoid. The head of the bone is displaced far beneath the coracoid process; the form of dislocation might be classified as subclavicular. It is probable that in this case there was both a true and a false dislocation. After reduction (b) the tuberosities seem to be absent, though indications of their fragments are shown near the lower edge of the glenoid. I have operated upon a number of other similar cases (e.g., Nos. 5 and 92), so that I have formed the opinion that when the X-ray after reduction shows the absence of the tuberosity, radical operation is indicated, even if the X-ray does not demonstrate the fragments. It is my belief that this form of displacement accounts for the great majority of instances, which the authors quoted in this chapter speak of, as unsatisfactory results.

Case 115, to be reported later, was also an illustration of this condition. Two of the most alert industrial surgeons whom I know were fooled by the superficial appearance in this case, and I, myself, did not recognize it on my first visit. Even Stevens, whom I regard as having been particularly well informed about conditions in the shoulder, shows in his illustration, "Fig. 4," what I believe to be a case of this kind. He speaks of the fragments as having disappeared behind the head of the humerus. In cases showing X-rays similar to this, I would recommend exploration through the routine incision of the bursa. If it is obvious that the fragment has retracted into the glenoid, I recommend enlarging the incision to a "sabre-cut," and making an attempt to suture the structures in their normal position.
Before leaving the subject of anterior dislocation, I should like to italicize the following paragraph:
I believe that after the reduction of every case of dislocation of the humerus, the patient should be allowed to recover from the anaesthetic and be urged to move his arm freely, before any bandaging is applied. All motions may be safely performed except abduction in external rotation, and even this may be done with due care and using extension at the same time. If we find paralysis of any of the muscles, areas of skin anaesthesia, undue axillary swelling, gritting sensation in the joint, or a tendency for the joint to slip out of place, the patient should be at once hospitalized and consultation obtained.

(The author here advises the reader to study the next chapter on fractures and then to return to the remainder of this chapter, which discusses some of the more unusual forms of dislocation.)

FIGURE 58
(c) Explanation. Erect dislocation, as usual, preceded the subcoracoid position. The fragments of tuberosity, still held together by the musculo-tendinous cuff, slipped down on the glenoid, while the head was dislocated below and the arm fell to the side. Reduction was attempted and seemed successful, but the head of the humerus merely became superimposed on the fragments so that it seemed that the dislocation had been reduced, and the contour of the swollen shoulder became nearly normal. The biceps tendon was carried with the fragments on to the glenoid. In Case 115 there was scarcely any fracture except at the facets of insertion; the whole musculo-tendinous cuff had dropped back on the glenoid. In most cases the retracted tuberosities are held on the glenoid by the short rotators, as this man holds his hat on the further side of the tree. The biceps tendon may (Case 115) or may not (Case 71) be torn in such cases.

Subacromial dislocation is rare. I can only recall one case in private practice. This was in a young man who was a personal friend. It is twenty years since I reduced his dislocation, immediately after the accident, and the shoulder has given him no trouble since. Probably most of these subacromial or subspinous cases run as smooth a course, but occasionally, as in the following instance, one proves to need operation.

No. 33. Mrs. C. B. Age 38. Massachusetts General Hospital No. 184814 W. S., Sept. 7, 1912.
A case of recurrent subspinous dislocation which had remained unreduced for three months. "Sabre-cut" incision, the joint carefully inspected and cleaned of old granulations and detritus. None of the short rotators had been ruptured. Dislocation reduced and acromion wired in place. April 17, 1914, she writes, "I am thankful to say my shoulder is all right. It does not seem to be as strong as the other one, otherwise it is fine."

This is the type of case in which the "sabre-cut" incision is particularly applicable, in fact, it is almost indispensable if one wishes to obtain a satisfactory cleaning out of the glenoid. In all these operations for old dislocations I have found the glenoid to be filled with old granulations and detritus. Satisfactory reduction could not have been done without thorough cleaning of the cartilaginous surface.
The second case is an illustration of what I believe to be the usual mechanism of subacromial dislocation. She gave the history that seven years previously the first dislocation had occurred, during a convulsion while she was in labor. Six months later she dislocated it again while " closing a door behind her." The last time it was dislocated by "turning quickly around in her chair."
In the case first mentioned, the young man sustained his injury while being thrown from a sitting posture on a toboggan which had struck a rock. He was thrown in the air—presumably still holding the railing of the toboggan. This might produce the same effect of internally rotating the arm, as in closing a door behind the back.

OLD DISLOCATIONS

Speed considers a dislocation as old and irreducible after three months. The obstacles to reduction are the same as for a simple dislocation plus such secondary changes as:

Cicatricial contraction from healing scars in the capsule and adhesions to surrounding structures.
Displaced bone fragments, osteophytic outgrowths, callus, etc.
Muscles shortened and atrophied.
Synovial space obliterated
One can readily understand the difficulty of reducing an old dislocation if he will study the specimens to be seen in anatomic museums. The remarkable attempts of nature to derive some utility from a dislocated shoulder joint make reduction most difficult. At the point where the humeral head lies against the scapula, a tremendous bony proliferation takes place, and inevitably ankylosis or pseudoarthrosis results. The glenoid becomes atrophied and filled with fibrous tissue.
The varying combinations of pain, deformity, and limitation of motion which these patients present have incited surgeons to attempt relief. Every surgeon of large experience htts probably made a few attempts to help such patients, but before long finds that they form a class of cases in which he can be generous to his younger colleagues, who also in time learn by experience. As a matter of fact, these are serious cases and demand expert care, although this is not attainable at present, for there are no such experts, so far as I am aware.
There are five general lines of treatment from which we may choose.

(1) To leave nature to do the best she can.
(2) To attempt bloodless reduction under an anaesthetic.
(3) To attempt open reduction.
(4) To resect the head of the humerus.
(5) To perform arthrodesis.

Andrews concluded that an attempt at reduction by manipulation is extremely dangerous. In his words, "The bloodless method has a gory trail of accidents." He finds fifty cases of hemorrhage, mostly fatal, up to 1905. An interesting one was reported by J. C. Warren, in whose case a large aneurysmal tumor arose after attempts at reduction. The subclavian was tied and recovery ensued.
If a new joint can be produced at all, it should be possible to do it by the "sabre-cut" incision, for all the structures of the joint are readily visible and accessible. I have encountered two chief difficulties. One has been the fusion of the retracted tendons and tuberosities with the glenoid alluded to in Case No. 71. If many months have passed, there is little left of the cartilaginous surface of the glenoid when the debris has been removed from it. However, this is not the chief obstacle—the real one being the absence of any synovial membrane to prevent adhesions of the cartilaginous head in its new bed. If the cartilaginous head is not too badly destroyed and seems likely to function, I should advise completing the attempt to make a new joint, but if the head has been eroded and there is no synovia left to surround it, adhesions will surely take place, and almost no motion will be secured. An irritable, painful joint with only a few degrees of mobility will result. In such a case, I think that one should deliberately perform excision or arthrodesis. The method of arthroplasty recently suggested by Dr. Laurence Jones of Kansas City offers a most hopeful solution of this problem.

RECURRENT OR HABITUAL DISLOCATION OF THE SHOULDER JOINT

Recurrent dislocation is not a common lesion, but it has interested a large number of investigators. Speed says that this lesion is peculiar to athletes and epileptics. This is more than a witticism, but not entirely true. Almost every author has put forward a somewhat different theory as to the cause of recurrent dislocation, and Speed has gathered together the most important ones. They are:

Defect in the head of the humerus acquired at first dislocation, or perhaps congenital.
Defect in the glenoid—acquired fracture of the edge, or congenital shallowness.
Rupture of the insertions of the external rotators of the head of the humerus.
Avulsion of tuberosities with or without rupture of the rotators.
Detachment of capsule from anterior lip of glenoid.
Enlarged joint from relaxed capsule following tears which have been given insufficient time for strong cicatrization, or repeated stretching without tears.
A seventh theory may be added. Since the shoulder joint is not a real joint, and is dependent for its integrity on a very complicated neuro-muscular cooperation, the essential feature in some of these interesting cases may be a failure of this cooperation. Reference to Plate I will show how easily incoordinated pulls from two opposing muscles might result in instability of the head on its fulcrum. Rupture or stretching of the tendon of the latissimus might thus make the joint unstable in the pivotal position. Certainly from an X-ray point of view the bony structures in most of these cases are normal.
The slight support furnished the joint by the bony structures has been considered, and it would seem more reasonable to suspect a defect in the major supporting structures, the muscles and their tendons, than in the bony structure. The importance of the supra-spinatus and of the other short rotators has been emphasized, and it has been noted with what frequency their continuity is broken in ordinary dislocations. More authors have found occasion to mention lesions of the short rotators and tuberosities in recurrent dislocations than in simple dislocations, because the majority of the former cases are treated surgically, so that more opportunity is afforded for observation.
Considerable evidence is given in favor of each of the causes listed by Speed and probably any one of them could well account for a recurrent dislocation. Hildebrand found two cases of fracture of the anterior rim of the glenoid with laceration of the capsule, in which he obtained good results by reshaping and deepening the glenoid. In an X-ray study of twenty-one cases in Hildebrand's clinic in Berlin, Pilz found definite bony defects in the humeral head in fifteen, de Fourmestraux found a deformity of the head in four out of eighty cases. Henderson reported no bone injury found by X-ray in many cases. We have seen several cases in which no abnormality could be found with careful X-ray examination.
According to Stevens recurrent dislocations at the shoulder joint are always due to more or less tearing of the supraspinatus, infraspinatus, teres minor, and more rarely of the subscapularis, and their subsequent repair by scar tissue in a position of stretch. No definite cases to prove this were given.
Thomas concludes that habitual dislocation is due to a traumatic, cicatricial, anterior, hernial pouch of the capsule. The most constant lesion which he found was a tear in the anterior and lower part of the capsule. In an experimental luxation of the shoulder on a cadaver, he placed the head in complete subcoracoid dislocation, and found the supraspinatus, infraspinatus and teres minor not torn or greatly stretched. However, any assumption that such lesions do not occur in the living is unwarranted, for the conditions are so different. In such experiments lax atonic tissues replace the living contractile muscles, and the force is gradually and gently applied as compared to the sudden smashing force acting in the living. A force suddenly applied against active muscles would have much greater rupturing power than a much greater force evenly applied against dead muscles.
One of the earliest mentions of the role of the supraspinatus was by Duchenne, who wrote: "Recurrent dislocation cannot occur with a normal supraspinatus." Yet I do not entirely agree with this great authority, for in none of my cases of habitual dislocation have I demonstrated such a rupture, and in two I actually did demonstrate that there was no rupture. Furthermore, I have never seen habitual dislocation complicate a case of ruptured supraspinatus.
Speed states that the head of the humerus twists out of the glenoid through the inferior portion of the capsule, and he believes that to permit this dislocation there must be a great strain on the supraspinatus tendon, or even a tear in it.
It is in the treatment of these recurrent cases that the greatest variations of opinion are to be found. Almost every author has contributed a different technique. The surprising thing is that so many varied methods should produce such uniformly excellent results as are claimed for them, yet the number of methods suggests that none is highly successful. The essential points of some of these methods of treatment will be briefly given with their results, when obtainable. Many of the reports are based upon too few cases followed for too brief a period. It is noticeable that few authors have reported later series in a second paper, and this suggests that the late results and greater experience have not supported them in their early statements.

Treatment.

Two general principles of treatment have been applied to habitual dislocation. They are:

Prevention—control primary dislocation, and allow healing of capsule.
Reconstruction.
A. Suspending head of humerus from above.
B. Support from below.
1. Reefing.
2. Bone operation on glenoid.
C. Combinations of above.
D. Use of the long head of the biceps as a round ligament.
A shearing-off of the attachment of the capsule to the fibrocartilage of the glenoid is described by Bankart as the cause of recurrent dislocation. The defect is permanent and his operation aims to repair the rent. His incision runs from above the clavicle downward and outward over the coracoid for about five inches. The deltoid and pectoralis major are separated, not cut, and the coracoid divided and driven downward with the muscles attached. The subscapularis tendon is divided and the capsule sutured to the glenoidal labium. The subscapularis and coracoid are sutured in place. Four weeks of rest is followed by active and passive motion. Four successful cases are reported.
Carrell, who gives the above classification of treatment, uses an ingenious combination of A. and B. An anterior incision exposes the long head of the biceps. The tendon is sectioned at its lowest level, and reflected from its sheath to where it emerges from the capsule. The distal end of the muscle is attached to the short head. To the free tendon is attached a piece of fascia about six inches long. A posterior incision running down four inches from the acromion separates the deltoid and exposes the teres minor. The fascia is passed under the neck, weaving in and out of the capsule. It emerges just above the teres minor and is passed through a drill hole in the acromion. The arm is immobilized at the side and motion begun in three weeks. Good results are reported in four cases. One wonders whether the posterior incision can be made without injury to the circumflex nerve. Recently Fowler has suggested a modification of this suspension operation. The biceps tendon is not interfered with, but a strip of fascia lata is passed through the capsule below the neck and anchored, both on the acromion and on the coracoid.
A bone transplant was placed by Eden under the raised periosteum of the neck of the scapula so that one-half to one centimeter stuck out in front of the joint. He also reefed the capsule and kept the arm abducted for three weeks.
Henderson's tenosuspension operation has been popular in America, but as seen by the discussion following Fowler's paper, it cannot be a thoroughly satisfactory procedure. Keller uses a crucial plication of the capsule through a posterior incision. Loeffler places a band of fascia from the greater tuberosity of the humerus to the acromion. Mandl used Finsterer's operation with success. The head of the humerus is held back by a band on the anterior surface of the joint, taking the place of the normal joint capsule. The band is composed of "part of the coraco-brachialis and part of the biceps." Oudard divides the subscapularis and overlaps it so as to shorten it about three centimeters. The tip of the coracoid is cut and a bone graft three to four centimeters long is inserted between base and tip. The coracoid may be slit and one-half slid down so as to lengthen the coracoid three centimeters. Nine cases were treated successfully. Six additional cases are reported. Perkins devised an operation in 1906 for suture of the torn capsule and reports good results. A restraining ligament was made by Plummer and Potts using a fascial strip from the greater tuberosity to the acromion. They report two cases with good results. Nine cases of recurring dislocation were treated in a year by Riviere, who pleated the capsule by placing interrupted sutures through the subscapu-laris. Landes uses a fascia lata cord or several silk sutures and suspends the head of the humerus by passing this cord through a drill hole and slinging it over the clavicle just lateral to the coracoid. Selig, who considers atrophy or rupture of the external rotators the main cause of habitual dislocation, makes an incision through the supraspinatus fossa, separates the trapezius fibers, and shortens the supraspinatus tendon by plication.
It is Sever's belief that the subscapularis and supraspinatus prevent dislocation when the arm is elevated by opposing the pectoralis major, which adducts and draws the humerus forward, and pulls the upper part of the humerus inward and downward. He says that in all operations for recurrence, the good comes from cutting the pectoralis major and shortening the subscapularis. No results are stated. He notes that repair of the infraspinatus and supraspinatus can also be done at the same time. Other authors, notably Allis, have also held similar views.
The operation advocated by Speed is done through an incision just below the coracoid and extending down four inches. The pectoralis major is divided one and one-half inches from its insertion into the humerus, and the axillary structures put aside. The edge of the glenoid is next palpated, after which, a drill hole one inch deep is made diagonally into the neck of the scapula. A bone transplant from the tibia is driven in with three-fourths inch projecting. This is supposed to prevent the head of the humerus from slipping out forward into anterior dislocation, at the same time not interfering with the normal range of motion.
A heavy silk ligature reenforces the anterior part of the capsule in the operation of Spitzy. A curved incision exposes the deltoid insertion, which is cut and retracted. A heavy silk ligature is passed around the surgical neck and tied in front. The ends are left long so that they can pass upward anterior to the capsule, and be tied over the coracoid. The capsule is then folded over the ligature and sewed, thus shortening the capsule. The deltoid is re-attached, and after a rest period of four weeks exercise is begun.
Thomas was an exponent of the capsule pleating operation. He used a posterior axillary incision, and took a reef in the capsule. He claimed exceedingly good results, as do the others. He performed capsulorrhaphy on eighteen epileptics suffering from recurrent dislocation. Twelve cases were successful, for a time at least. A capsule pleat and fascial transplant across the front of the joint is performed by Valtancoli, who reports eighty-six per cent cures.
It would seem that a patient stands some chance of cure by any of these methods. Therefore, it would be to the patient's advantage to choose the simplest, since his chances of recovery are as good as if he had the most complicated one. It is interesting to speculate why such a diversity of treatments should produce so uniform a result. It may be explained by the temporary or permanent limitation of joint function consequent to the operation. Some of the above procedures have as an object the limitation of motion, and all of them probably do limit motion. The trauma of the instrumentation, the bleeding and exudate, and the placing of sutures result in the formation of scar tissue. In addition the arm is immobilized for a time. Fixation and a sensitive scar produce pain on motion, and a certain mental impression which results in a patient's using his arm in a very gingerly way for a long time. Actual limitation or voluntary limitation are important reasons why the arm is not soon again moved into extreme elevation. It is highly probable that the late results of all these methods would not be entirely satisfactory.
Some authors have advocated and devised external apparatus to check abduction within a safe limit. These hobbles are a nuisance and offer no cure, but do prevent dislocation. The lesion is annoying and causes so much disability that many of these cases beg for operation. The treatment should be suited to the type of lesion and to the habits of the individual patient. Bony defects should be repaired or modified by plastic methods. Nicola's operation seems to be applicable, whatever the cause.
The writer has on two occasions done negative exploratory operations for this condition by opening the bursa but without entering the joint. The following case may be of interest to those who believe that deformities of the head of the bone may be the cause of recurrent dislocation, for in this patient a thorough exploration was done.

Case No. 24. Mr. K. N. Age 26. Massachusetts General Hospital No. 182833 E. S., May 22, 1912.

A large, powerful young man. First injury six months before while wrestling. Repeated dislocations after slight muscular efforts since then. "Sabre-cut" incision, supraspinatus divided and joint explored. The capsule was found to be torn, especially the portions at the lower and inner edge of the glenoid. A sort of hernia of the synovial membrane existed, which evidently made a pouch for the head when dislocated. A plastic repair was done on this part of the capsule. Part of the articular surface was missing, as if it had been broken off and absorbed. The patient was seen by me about a year after the operation, and at that time had a perfect result. I have not been able to trace him since.

This particular condition of axillary tearing of the capsule has been described by Thomas of Philadelphia, and considered by him to be the most common lesion in shoulder injuries. I have little doubt that it is a factor common to all recurrent dislocations. One cannot imagine dislocations occurring without a tear of the capsule of the joint. In all these cases the pillars of capsule which bound the opening of the bursa subscapularis must be more or less torn to enable the head of the humerus to lie in the subcoracoid position.
I have seen numerous cases of habitual dislocation, but owing to my lack of faith in any particular technique I have done few operations. I have been content to teach the patient about the mechanism of dislocation and explain to him that he cannot dislocate his arm without combining rotation and abduction. He may abduct the arm as much as he is able to do so in internal rotation in the coronal plane with impunity. These cases are usually in young men, and as has been said before, in athletes or in epileptics. Athletes may avoid dislocation by giving up those forms of athletics which tend to produce it. I have known two young men, who were my personal friends, both of whom were subject to this annoying difficulty. Both patients eventually outgrew it or changed their habits so that it did not occur. One of them, for instance, had to give up boxing because the arm would at times dislocate if he gave a forward blow. In doing this, the relation of scapula and humerus are practically the same as when they are in the pivotal position. He was a skillful athlete at other forms of amusement. It seems to me that for this type of patient it is better to change habits than to submit to operation.
In the cases of epileptics, it is imperative that the patient should wear an apparatus which prevents the combination of external rotation and abduction or should be operated upon. It has not been my fortune to have the care of any such cases. Should I be compelled to operate for this condition, I should at present choose the operation of Nicola. I here reprint some remarks made by Dr. Nicola at the discussion of Dr. Fowler's paper.
"For three years I have been using my own operation, which does not utilize any foreign material. It is done through one incision, the convalescence is short, and so far as I know there have been no recurrences on operations done by me as well as by about thirty other operators. It seems to me that it is getting more and more difficult for the student of orthopedics to decide which type of operation to use. In the end the operation that will become most popular is the one that is very simple to perform and can be done most frequently on almost any type of dislocation, no matter what the pathologic changes are (bony defects, muscle tears or capsular tears) ; and, finally, it is a matter of convalescence. In the operation which I have been doing, the line of incision begins just above the coracoid process and extends down and out in the line of the fibers of the deltoid. In my original description I stated that this should come between the pectoralis major and the deltoid, but I find that it is easy to approach it merely by going through the lines of the fibers of the deltoid. Before cutting the tendon, one should be sure to put transfixion sutures in both ends because frequently the arm may extend and the lower segment of the biceps tendon will slip behind the pectoralis and cause great anxiety. After the tendon is divided, a hole is drilled through the head of the humerus. I usually go anywhere along the bicipital groove and point the drill so that it comes out at the upper end of the angle of the head. The tendon is passed through the head and is sutured on itself, so that there is no muscle loss and the tendon has a tendency to restrict the movement and, therefore, keeps the head in the glenoid cavity. Some of the men have used this operation for fracture of the surgical neclc of the humerus when there has been downward displacement of the head into the axilla, and there they replace the head in position and drill a hole so that they maintain the head in position."
This operation appeals to me as more likely to fulfill the conditions required than any of the others. Fowler's operation also seems to me a rational procedure, but not so simple as Nicola's.
Extract from a personal letter from Dr. Nicola, June 6, 1930: "The cases reported in the reprint which you received, together with the rest, have been followed over a period of two years. The boxer has been back in the ring and has won two semifinal contests with no recurrence of dislocation. Case No. 3, which was an epileptic, was killed in an auto accident eight months after the operation. Through friendship with the coroner, I was able to examine the tendon of the long head of the biceps with special reference to the point which you made in your letter. I found that instead of thinning out of the long head of the biceps which extended to the glenoid cavity, the tendon above the humerus was thickened about the size of the little finger."
Extract from personal letter from Dr. Nicola, June 6, 1932: "I have personally done twenty-four of these operations with one hundred per cent cures. I have not heard of any recurrences from the various men who are associated with me at the Hospital for the Ruptured and Crippled. I hope that you will soon find an opportunity to operate upon such a case and to convince yourself that this operation is very simple to perform. I am now doing it through a two and one-half inch incision taken just below the clavicle on the inner side of the coracoid process and extending downward through the fibers of the deltoid muscle. The hole through the head of the humerus is made with a one-fourth inch gauge, instead of a drill. This facilitates matters considerably."
This operation I am sure could be readily done through my routine bursal incision which separates the deltoid fibers directly over the bicipital groove.

INFANTILE DISLOCATION OF THE SHOULDER

Lesions of the bursa or of the supraspinatus tendon in childhood apparently do not occur, at least they have never fallen within my experience. However, a not very infrequent lesion in childhood, namely, birth palsy complicated by dislocation of the shoulder, sometimes causes confusion in the diagnosis of shoulder lesions in later years. We see the shoulder deformed from a lesion which occurred at or soon after birth.
There has been much discussion as to whether the term congenital dislocation of the shoulder joint should ever be used. It seems very probable that a large number of so-called congenital subluxations, if not a majority of the published cases, were instances of obstetric palsy in which the dislocation remained after the paralysis had recovered. Infantile dislocation may be discussed under three headings, according to whether it existed before birth, occurred at birth or resulted soon after from paralysis caused at birth.

(1) Abnormality of development—true congenital dislocation. The existence of such a clinical entity has been questioned, but it has been established without any doubt, although it must be very rare. R. W. Smith of Dublin, in 1839, was the first to bring this condition before the profession. He published an account of three cases in the Dublin Journal of that year. Two of these were males, age 20. The dislocation was subcoracoid. The muscles about the shoulder were wasted. One patient had club foot. The third case was an insane woman, age 29, in whom the condition was bilateral.
At post-mortem examination there were facets just under the cora-coid, with a displacement of the capsule anteriorly to enclose the joint. The head of the humerus was flattened, and the acromion and coracoid elongated and hooked downward. In all the cases abduction was limited. Eleven years later Smith published two additional cases. In 1841 Guerin presented two cases and demonstrated a symmelian foetus which showed this abnormality on both sides. Since these reports, numerous cases have appeared in the literature. Grieg analyzed the cases of fifty-eight authors in the Edinburgh Medical Journal of 1923. He makes the following statement. "So far I have only found twelve cases reported to date in which evidence brought before the profession fails to justify any other conclusion than that they are cases of true primary congenital dislocation of the shoulder."

(2) Dislocation produced by obstetric manipulation or during birth. This group is open to criticism because proof of its existence is not satisfactory. T. T. Thomas was firmly of the opinion that traumatic dislocation not only occurs, but is the primary factor with regard to paralysis. He believed that paralysis is secondary to a rent in the capsule due to a traumatic dislocation. Taylor, writing in 1921, states that neither he nor any of three obstetricians of a large Lying-in Hospital had ever seen a case of Erb's palsy in which the subluxation preceded paralysis. In 1866 Loignan wrote a thesis for a Paris doctorate on the subject. He found that he could not dislocate the shoulder by manipulation. The constant lesion which occurred, if sufficient force were used, was a fracture of the humeral shaft through the soft bone under the epiphysis. Other investigators, notably Sever, have been unable to produce traumatic dislocation or rupture of the capsule by manipulation in infant cadavers. The writer feels that dislocation occurring at birth is so rare as to be negligible in diagnosis.

(3) Acquired subluxation due to injury of the plexus. Obstetric paralysis was first described by Smellie in 1768. He thought the condition was due to prolonged pressure on the arm while the child was in the pelvis. It was brought before the profession, however, by Duchenne, who in 1872 described four cases in infants and believed it to be due to pressure on the nerve trunks. Erb described the palsy in adults in 1874. Since that time it has been known as Erb-Duchenne paralysis. Erb believed it to be due to pressure on the fifth cervical root, known as Erb's point. Fieux opposed this view and adopted the theory that traction is responsible. He demonstrated on infant cadavers the fact that when the head is forcibly drawn away from the shoulder, the fifth cervical root is torn just proximal to its junction with the sixth nerve. With more force, the latter nerve may also be torn. Only the muscles of the upper arm are paralyzed. The palsy is usually flaccid.
Infants with Erb's palsy present a typical history and appearance. There is usually a difficult birth where traction on the head has been made under ether relaxation. The arm hangs limp and vertically at the side, the elbow is extended and the forearm pro-nated. There is inability to abduct, elevate, outwardly rotate, or supinate. There is extreme internal rotation so that the palm often faces outward. After a short time, there is wasting from disuse, and flattening of the shoulder soon appears. Passive motions' are free at first, but the healthy muscles soon contract and produce limitation of motion—notably of external rotation. The muscles paralyzed are the deltoid, supra- and infra-spinatus, teres minor, biceps, brachialis and brachioradialis. There is no sensory disturbance.
Clark, Taylor and Prout estimated one case of palsy in 2,000 births. Most cases of birth palsy show some luxation of the head of the humerus. Fairbanks saw twenty-eight subluxations in thirty-seven cases of palsy, or seventy-six per cent; Thomas reported nine in twelve. Taylor has reported sixty-eight cases, forty-six of which showed subluxation. He has never seen the condition in patients less than six weeks old. Of those patients who had palsy, who were more than six weeks old, seventy-seven per cent showed subluxation. In 109 X-ray studies reported by Sever in 1916, sixty-four or fifty-nine per cent showed subluxation. The ages in this series varied from one day to eighteen years.
It should be noted that this form of dislocation is posterior, while the first two forms are anterior or inferior.

Mechanism of Posterior Subluxation. The appearance of the arm soon undergoes a change from the flaccid condition which follows the immediate injury for a few weeks after birth. The upper arm is brought forward and adducted by contraction of the well muscles. The elbow is usually a little flexed, the pronated forearm passing downward and inward across the front of the body. Abduction is checked before the arm comes to a right angle. Backward motion is usually impossible and external rotation is markedly limited. With the elbow at the side, it is often impossible to rotate the humerus out sufficiently to bring the forearm into the forward plane. The bones of the affected side—the humerus, scapula and clavicle—are smaller than those on the opposite side. This is an important point in the diagnosis of late cases. The front of the shoulder is flattened, while there is a fullness behind, below the acromion, due to the head of the humerus. The muscles which tend to prevent posterior dislocation are the teres minor, supraspinatus, infraspinatus, and posterior part of the deltoid. The pectoralis major, the teres major and latissimus dorsi are rarely even partially paralyzed and rotate the humerus strongly inward. The subscapularis acts as a powerful internal rotator. These muscles become contracted while the paralyzed ones are stretched. The teres major and latissimus dorsi exert traction downward and posteriorly. The anterior portion of the capsule becomes shortened secondarily. Since the arm is held in an internally rotated position, there is a constant jstrain on the neck of the humerus, tending to twist it backward. In the plastic young bone, this twisting occurs and the plane of the head of the bone to the shaft may be changed ten or fifteen degrees. The dislocation is not truly posterior—it is rather a rotation of the head than a dislocation, so that the articular portion is rotated backward and the side of the head lies on the glenoid without having escaped from its capsule.
During the first year nothing can be seen in the way of bony deformity in the X-ray, except possibly a slight posterior subluxation and relatively small size of the head compared to that of the other side. As the child grows older, the subluxation increases. There is increased outward displacement and elevation of the scapula. The acromion and coracoid become hooked downward in front of the head of the humerus. The clavicle is shortened and its curves are more marked than in the normal. The coracoid process is usually elongated. The glenoid becomes shallow. These changes of the bones occur while the paralysis exists, and even if the paralysis clears up, they persist.

Treatment. In early cases the arm may be held in abduction, elevation, external rotation and supination by a light wire splint. Sever, however, prefers to let the child use the hand and arm freely with the risk of contractures. Passive motion and massage are carried out at frequent intervals. Operation is deferred until the child is three or four years of age. Once contractures have developed, it is best to cut the contracted muscles. Manipulation is of little value because of the tendency to recurrence, unless the paralyzed muscles have regained their tone. Sever has described his operation at length in a paper read before the Section on Orthopedic Surgery of the American Medical Association, 1925. He cuts the pectoralis and subscapularis tendons and removes one-half inch to three-quarters inch of the tip of the coracoid with its muscle attachments. If necessary he removes the hooked acromion to allow reduction. The arm is put up in a light splint in abduction, elevation, external rotation and supination. Muscle reeducation by active and passive motion is begun after eight to ten days. The splint is worn night and day for three months, but is removed daily for exercises.

Prognosis. This depends largely on the recovery of the paralyzed muscles in early cases. If the child is seen early, contractures and subluxation may be minimized by passive motion until the nerves have regenerated. In late cases, however, where contractures have developed and there is no tendency of the nerves to regenerate, operation has to be resorted to and gives a good, hut not brilliant, functional result. Sever records partial recovery in 297 of 394 cases which were operated upon. After operation there is great difficulty in inwardly rotating the arm. He states that this may be eventually overcome, however.
I have had very little personal experience in these cases, but the following case taught me such an important lesson that an account of it is presented in the hope that it may stimulate some one to follow up a series of such cases in which operations had been done in childhood.

CASE 70.
A strong boy, age 14, was referred to me for trouble with his shoulder, with the story that he had had difficulty since he was a baby, and that while he was a very strong, active boy otherwise, he was greatly handicapped by his shrunken, weak, deformed right arm. The diagnosis in the case puzzled me a good deal at first, for there was no paralysis, and the X-ray simply showed a rather small and deformed humeral head and glenoid cavity. In spite of this, by palpation, it was easy to feel that the head of the humerus was posterior to the glenoid under the acromion. Both the coracoid and the acromion were hooked down in an unnatural manner, which was easy to understand when one recognized the true character of the lesion, for the acromion process had nothing beneath it and was not performing its normal function. All parts of the shoulder, including the bones, were smaller than those of the opposite side. There was practically no motion in the scapulo-humeral joint and the arm was held in internal rotation. An extraordinary amount of compensatory mobility had developed in the motion of the scapula on the chest wall— not only in flexion and extension, but in abduction and adduction.
It was clearly a case of birth palsy in which the bones had remained out of place after the muscular paralyses had recovered, and therefore the patient now only suffered from the consequence of the luxation.
I operated on June 16, 1921, through a "sabre-cut" incision, and to my surprise, found that the cartilaginous surfaces of the glenoid and of the head of the humerus had remained in nearly a normal condition, although they had been separated for so many years. The capsule was stretched and distorted, but not disrupted. The cartilaginous surface of the glenoid was rather puckered and the articular head of the humerus was small and rather misshapen, although less so than one would think from the appearance in the X-ray, which of course showed the surface of the bony centers of the epiphysis and not the cartilage. The contraction of the subscapularis and pectoralis major was so great that I had to divide their tendons in order to get the head of the bone in place. The coracoid process was so deformed that I had to excise about two-thirds of it subperiosteal^ in order to reduce the humerus. The "sabre-cut" incision, of course, mobilized the acromion. After reducing the head of the bone, I was able to put four silk sutures "a-distance" to reunite the cut ends of the subscapularis. I did not attempt to correct the torsion of the neck, although it caused some eversion of the arm when the head of the bone was in place. The whole wound was sutured, and the patient was put up in plaster in semi-abduction and semi-external rotation.
It was most remarkable to watch the boy's convalescence. There was a good surgical recovery, but the miraculous part was to see the promptness with which the bones and muscles tended to grow into normal condition. Within six months he had nearly normal use of his shoulder, and the condition of the muscles had greatly improved.
As the patient lived in another city I lost track of him about six months after the operation and did not see him again for ten years, when I looked him up in preparation for this book. It is fortunate that I did so, for the lesson which I learned was important and may be of help to others.
During the ten years that had passed, the boy had become a man of twenty-four, whose occupation was in moving buildings. He did much of the manual labor himself. When he came into my office he looked strong and vigorous, and I had to ask him which shoulder was the bad one. Then my disappointment came.
A skillfully made movable pad inside his coat concealed the small size of his right shoulder. His vigorous handshake and well-developed forearm gave no hint of the practically ankylosed joint which was displayed when he removed his clothes. On closer examination I found both coracoid and acromion clutching down on the head of the bone like crooked fingers grasping it and holding it fixed. It appeared as if the acromion process had bent downward from the point where I had divided it and had become fixed in this position.
After a time the explanation occurred to me. At fourteen, the acromion and coracoid are cartilaginous epiphyses, for they have not yet ossified. After my operation, although the head of the humerus was in place, it was small and underdeveloped because of imperfect function for fourteen years. Consequently the cartilaginous acromion and coracoid became bent down over it, grasped it, and then, at about twenty, turned to bone and held it fixed. I did not at the time of the operation realize that the greater part of the acromion does not unite with the spinous process until about twenty. I think now that if I had insisted that this boy should have slept with his arm elevated until he was twenty, and had kept up appropriate exercises, he might have obtained a more perfect shoulder. It is not a great hardship to form the habit of sleeping with the arm in the hammock position. Many people do this by preference. He had been able to hold his arm in this position when I last saw him six months after the operation. Later the strength of the divided internal rotators returned and tended to rotate the arm to its old position, and also to resist elevation in external rotation. The head of the bone being small, the cartilaginous acromion slowly yielded to fit over its convexity. I think that it is highly probable that if the late results of other operations which have been done for these cases were critically examined, the same disappointing condition might be found in later years. Operations should not be undertaken on these cases unless the parents are warned that the patient should be under the surgeon's care until his epiphyses are united; i.e., when the patient is about twenty. I am inclined to think that nature's results at the end of ten years would compare very favorably with those of surgeons.

ACROMIO-CLAVICULAR DISLOCATION

A brief consideration of lesions of the acromio-clavicular joint seems advisable, although strictly speaking, neither the subacromial bursa nor the supraspinatus tendon are involved. One must remember that the coraco-acromial ligament intervenes between these structures. When this joint is dislocated the coraco-acromial ligament goes intact with the scapula. In severe cases the coraco-clavicular ligaments (conoid and trapezoid) are torn.
Mechanism. The acromio-clavicular joint, itself, is weak, but the conjunction of the two bones derives its strength from the conoid and trapezoid ligaments which are attached to the coracoid process of the scapula. Upward dislocation of the clavicle is favored by the upward and outward slope of the joint. The clavicular facet looks downward, outward, and backward. Dislocation is almost always caused by direct violence. A blow on the back of the acromion or a fall on the tip of the shoulder drives the acromion downward, inward, and forward, and the clavicle with the coracoid process as a fulcrum is torn away.
Dislocation is classed as complete or incomplete according to whether or not the facets clear each other. The ligaments of the joint itself are more or less torn, even in incomplete dislocation, but the conoid and trapezoid ligaments are usually torn in complete dislocation.
Diagnosis. The diagnosis is to be made from the history of trauma, pain and disability. The outer end of the clavicle is prominent and movable, and can be readily reduced, but reduction is hard to maintain if the coraco-clavicular ligaments are ruptured.
Treatment. Upward, outward, and backward traction on the scapula is indicated and can be applied by various braces or by recumbency. The most favored method is the clavicular cross. A T-shaped splint is applied to the back, and the shoulders strapped to the cross arms.
Open reduction and fixation are occasionally necessary. Several operations have been devised, most of them using fascial strips. Representative among these may be cited Bunnell's ingenious method. He threads a cord of fascia through holes in the acromion and clavicle, and places a loop under the coracoid process.
Prognosis. If the reduction can be maintained, the chances are good that a patient will regain function in the course of several months, but soreness and some pain may persist for years. Arthritic changes may take place. I personally have never found it necessary to operate on acromio-clavicular dislocation, but in extreme cases I should recommend Bunnell's operation.

ACROMIO-CLAVICULAR ARTHRITIS

In contrast to the mechanism of the scapulo-humeral articulation, that of the acromio-clavicular joint is typical of the kind in which arthritis is prone to occur. It is a hinge joint with a very limited degree of motion. For its size, when in action, it carries an immense burden of weight. For instance, as one pushes open a heavy door, this little joint has to bear the equivalent weight of almost the^ whole power exerted. The same is true of the joint on the sternal end of the clavicle, but that joint has a much larger surface area. In laboring men who carry or lift heavy burdens, spurring from arthritis of the acromio-clavicular joint is so common as to form almost as normal a tissue as the great calluses in their hands. In many of the older individuals, the rims of new-formed bone actually fuse, so that the joint becomes obliterated. These changes may progress with very little pain and discomfort to the individual, or they may be accompanied by the usual signs of arthritis, which occasionally are so severe that they incapacitate the patient.
The acromio-clavicular joint holds an exposed position on the shoulder, and falling objects not infrequently strike the joint directly—perhaps breaking some of the small bony lips, causing hemorrhage about or in the joint. Such cases may be laid up for months on account of the local tenderness when they attempt to use the arm. I find it very difficult, in giving an opinion on compensation cases, to state when such individuals should be expected to return to work. The X-ray appearance is far from being a criterion. A man may have a very ragged and hypertrophied-looking joint and yet be conscious of no symptoms. Another man with barely perceptible changes may have much local tenderness. On the whole, it is surprising how well these laboring men are able to bear acromioclavicular arthritis. The diagnosis of these lesions rests entirely on the readily ascertained facts of localized swelling and tenderness, supported by the X-ray evidence of lipping of the joint. Confusion in diagnosis only arises when one allows one's self to center his attention on this joint and to ignore other really more important lesions. Never forget that this condition may attract your attention too readily, and by its presence conceal a lesion of the supraspinatus which is far more serious. Acromio-clavicular arthritis must be judged by the degree of symptoms, not by its X-ray appearance, for often there is much lipping of the edges of these joints and yet no symptoms at all.
Treatment. As a rule, these cases respond well to rest. A few weeks' confinement of the arm in a sling soon after a bruise on one of these joints is all that should be attempted. I am convinced that complete fixation of this joint is unfortunate. I do think that rest is very important in acute stages. Patients who have had prolonged symptoms have usually had either prolonged energetic treatment or prolonged fixation.
In a few subacute and prolonged cases, I have cut into the joint with the same idea that one has in cases of periostitis, where one incises to cause relief of tension. As a rule, however, I believe that simple rest is the only form of treatment which is important. The usual physiotherapy methods may be of some use, but my personal experience with them has been little.
Remember that the acromio-clavicular joint is not in immediate anatomic relation with the subacromial bursa. The coraco-acromial ligament intervenes. Therefore, acromio-clavicular arthritis does not prevent rotation or abduction in the scapulo-humeral joint, except in extreme positions. If these motions are not present, do not blame the acromio-clavicular joint entirely, even if it is swollen and tender.
Arthritic changes in this joint commonly occur after luxation or subluxation, and soreness may continue many months and sometimes a few years after such accidents. Men who do their own work generally continue at it in spite of this protracted soreness, but employees are apt to find their shoulders too sore to permit labor, if their compensation is paid. Thus this little lesion may be the cause of their never working again, for it is a commonplace that a year of loafing is a serious matter for an elderly laborer. Surgical obliteration of the joint should be considered, in some cases at least, as a mental stimulant. It is not an important joint.

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RIVIERE, G. Capsulorrhapie de l'articulation de l'£paule pour luxation recidivante. Lvon Chir. 1918. 15. 437-439. Abst. J. A. M. A. 1919. 72. 612.
SCHI.AEPFER, K. Uncomplicated dislocations of the shoulder; their rational treatment and late results. Amer. J. Med. Sc. 1924. 167. 244-255.
SELIO, R. Die bei der habituellen Schulterluxation gebrauchlichen Operations methoden von anatomischen Grundsatzen aus betrachtet. Was leistet der Musculus supraspinatus. Deut. Zeit. fur Chir. 1915. 132. 581-588.
SEVER, J. W. The rational treatment of fractures of the upper end of the humerus. Report of end results. J. A. M. A. 1923. 80. 1603-1608.
SEVER, J. W. Recurrent dislocation of the shoulder joint. Mechanical consideration of its treatment. J. A. M. A. 1921. 925-927.
SINZ, P. Inaugural-Dissertation. Erlangen. 1982.
SPEED, K. Recurrent anterior dislocation at the shoulder. Operative cure by bone graft. Surg. Gyn. and Obst. 1927. 44. 468-477.
SPEED, K. Fractures and dislocations.
Lea and Febiger, Phila. 1916. p. 857-440.
SPITZY, H. Stabilization of the shoulder joint for habitual dislocation.
Surg. Gyn. and Obst. 1928. 46. 256-257. STEVENS, J. H. The action of the short rotators on the normal abduction of the
arm, with a consideration of their action in some cases of subacromial bursitis
and allied conditions.
Amer. J. Med. Sc. 1909. 138. 870-884. STEVENS, J. H. Dislocation of the shoulder.
Ann. Surg. 1926. 83. 84-103. STEVENS, J. H. Fractures of the upper end of the humerus.
Ann. Surg. 1919. 69. 147-160. STIMSON, L. A. Fractures and dislocations.
Lea and Febiger, Phila. 1917. TAYLOR, R. T. Fracture dislocation of the shoulder. Arch. Surg. 1928. 17. 475-483. THOMAS, T. T. Habitual or recurrent dislocation of the shoulder. Etiology and
pathology.
Amer. J. Med. Sc. 1909. 137. 229-246.
J. A. M. A. 85. No. 16, s. 1202. 1925. TREVES, F. Surgical applied anatomy.
Lea and Febiger, Phila. 5th ed. VALTANCOLI, G. Sulla lussazione abituale di spalla.
Chir. d. Organi di Movimento. 1924. 9. 131-140. WARREN, J. C. Am. J. Med. Sci. 1846. XI. WILSON, P. D. & COCHRANE, W. A. Fractures and dislocations.
Lippincott & Co. 1925. p. 59-153.

NOTE—Sinz (1932) gives a very extensive Bibliography. He recommends a bone transplant to the glenoid (after Perthes or Eden) but apparently was unaware of the work of Nicola.

==References==
<references />

File:Co415.png

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Left shoulder of a patient placed in a semi beach-chair position. The coracoid osteotomy is meticulously finished with a chisel. CP – coracoid process.

File:Co2414.png

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Marko.nabergoj:

Left shoulder of a patient placed in a semi beach-chair position. The coracoid osteotomy is meticulously finished with a chisel. CP – coracoid process.

File:Co2323.png

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File:AC release.png

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File:Pectoralis minor release.png

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File:Hohmann retractor.png

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File:Deltopectoral approach.png

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File:Incision.png

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File:Figure.png

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