Shoulder:Glenohumeral Instability/Posterior Instability
- 1 Bullet Points
- 2 Key words
- 3 History
- 4 Anecdote
- 5 Epidemiology and Mechanism
- 6 Anatomy, Pathoanatomy
- 7 Soft Tissue Lesion
- 8 Bony lesion
- 9 Associated lesions
- 10 Definitions
- 11 Classification of Posterior Shoulder Instability
- 11.1 Group A
- 11.2 Group B
- 11.3 Group C
- 12 Etiology
- 13 Risk Factors
- 14 Evaluation
- 15 Scores
- 16 Imaging
- 17 Treatment
- 17.1 Clinical Practice Guideline
- 17.2 Conservative (Non Operative) Treatment
- 17.3 Surgical (Operative) Treatment
- 17.3.1 Acute dislocation
- 17.3.2 Chronic Instability
- 18.104.22.168 Soft tissue procedure
- 22.214.171.124 Treatment of Anterior Humeral Head Defects
- 126.96.36.199 Humeral Reconstruction with Autograft or Allograft
- 188.8.131.52 Posterior Bone Block
- 184.108.40.206 Glenoid (Scott) osteotomy
- 17.3.3 Locked Dislocations, Static Posterior Dislocation or Glenoid Dysplasia
- 17.3.4 Derotational Osteotomy
- 17.3.5 Shoulder Arthroplasty
- 17.3.6 Arthrodesis
- 18 Postoperative Rehabilitation
- 19 Complications
- Posterior shoulder instability is not as rare as previously thought.
- Diagnosing posterior instability may be difficult because patients often report vague symptoms not linked to a clear history of traumatic shoulder dislocation.
- This condition is consequently often misdiagnosed or patients experience a delay in diagnosis.
- It that encompasses different acute and chronic pathologies involving the labrum, the cartilage, the capsule, bony lesions.
- A tear between the posterior labrum and the glenoid cartilage without complete detachment of the labrum is described as a Kim lesion. It is postulated that this lesion is due to posterior force acting on the posterior-inferior glenohumeral ligament as it attaches to the posterior labrum.
- Numerous classifications exist, none having unanimity.
- Risk factors for recurrent instability are: (1) age below 40 at time of first instability; (2) dislocation during a seizure; (3) a large reverse Malgaigne (Hill-Sachs) lesion; (4) glenoid retroversion, and (5) a high and horizontally oriented acromion in the sagittal plan.
- Hyperlaxity is multidirectional but instability is almost exclusively unidirectional.
- Physical examination comprises the articular range of motion, the rotator cuff, and jerk, Kim and O’Brien tests.
- Three views plain radiographs, including true anteroposterior of the glenohumeral joint, scapular Y (scapular lateral), and Bernageau views are the mainstay of imaging in the setting of shoulder instability.
- An internally rotated humeral head gives a rounded appearance on anteroposterior view, which is called the lightbulb sign.
- In case of a suspicion about posterior dislocation of the shoulder, additional imaging including, depending of the type of instability, magnetic resonance arthrography (MRA) or computed tomography (CT) is required.
- Acute or recurrent posterior dislocations can be treated conservatively, by soft tissue or bony procedures.
- Surgical options include anatomic reconstruction as well as non-anatomic procedures such as subscapularis tendon transfer, allo-/autograft reconstruction, derotation osteotomy or shoulder arthroplasty.
- Treatment of locked dislocation depends on the extent of the articular defect size of the humeral head, duration of the dislocation and patient-specific conditions such as age and activity levels.
Posterior shoulder stabilization; Functional instability; Soft tissue injuries; Locked dislocation; Subluxation; Epidemiology; Labrum; ABC classification; Treatment options; Arthroscopy; McLaughlin procedure; Bone block; Clinical outcomes; Complications.
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Epidemiology and Mechanism
Posterior dislocation of the shoulder accounts for around 20% of all shoulder dislocations, which is much higher than the 4-5% prevalence previously mentioned in the literature. A reason for this large discrepancy is the challenge of clinical diagnosis, since symptoms are often subtle and patients often lack the typical feeling of posterior apprehension in provocative arm positions.
Soft Tissue Lesion
Four different types of labral insertion have been described by Nourissat et al. Type 1, 60% of the cases, correspond to a posterior labrum totally inserted in the glenoid, with direct contact with the cartilage, totally flush. In type 2 (20% of the cases), insertion of the superior segment is medialized. Type 3, 15% of the cases, represents an associated medialization of the superior and medial segment of the posterior labrum. Type 4 is a medialized insertion of the all-posterior labrum.
Consequently, a subchondral cleft (labrum and capsule attached but no tear) may be a normal finding. Surgeons should be aware that while anterior capsule anatomy is quite variable, the posterior capsular insertion tends to be more homogenous in appearance among patients (Figure).
Reverse humeral avulsion of the glenohumeral ligaments (rHAGL)
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Reverse Malgaigne (Hill-Sachs)
This is usually present in patients with chronic locked posterior dislocations or in cases with significant traumatic history (e.g. seizure disorder, electrical injury). Patients with positional posterior instability with ligamentous laxity usually do not present with significant reverse Malgaigne (Hill-Sachs) lesions but may occur occasionally.
Associated intra-articular pathology such as superior labrum anterior posterior (SLAP) lesion, rotator cuff lesions or a paralabral cyst should be also assessed (Figure). Unlike spinoglenoid cysts, posterior or posterior-inferior labral cysts rarely results in impingement of the suprascapular nerve and suprascapular neuropathy.
Dislocation is defined by a complete displacement of the humeral head from its articulation with the glenoid, whereas subluxation represents an incomplete or partial dislocation of the joint. Laxity is a physiologic and an asymptomatic finding, that corresponds to translation of the humeral head in any direction to the glenoid. Hyperlaxity is constitutional, multidirectional, bilateral and also asymptomatic. Hyperlaxity of the shoulder is probably best defined as external rotation elbow at the side equal or greater than 85 degrees (Figure).
This finding is most of the time non-pathological (except in soft tissue pathologies like Ehler-Danlos syndrome), is a risk factor for instability but does not by itself demand treatment. Hyperlaxity is multidirectional but instability is almost exclusively unidirectional (Figure). From an etiological point of view, the posterior dislocation is typically differentiated into acute traumatic dislocation that becomes locked after 6 weeks if neglected, and recurrent instability.
Classification of Posterior Shoulder Instability
Posterior instability includes a wide spectrum of pathological conditions, which are sometimes difficult to classify homogeneously.
Classifications of posterior instability have been confusing and most attempt of classification failed. The ABC classification has the merit to be correlated to the presence or not of lesion(s), indication for surgery and results.
Table 1: The ABC classification of posterior shoulder instability
|Header text||A First time||B Dynamic||C Static|
Group A includes all patients with an acute first-time posterior instability event that can either have occurred in terms of a subluxation without engagement of the humeral head with the posterior glenoid rim (A1) or in terms of a dislocation with temporary or persisting engagement (A2). Distinction of this group and the two subtypes is possible by a combination of taking the patient’s history and imaging studies, both applicable even in the acute and painful setting.
A1: Acute posterior subluxation
Group B includes all patients with recurrent dynamic posterior instability events that occur during motion either in form of a functional instability (B1) or a structural instability (B2).
B1: Functional dynamic posterior instability
In many cases, the instability is voluntary but positional that is, the patient’s shoulder is dislocated/subluxed in the position of forward flexion, pronation, and internal rotation but relocates with the arm brought into abduction and extension. A voluntary dislocation is associated to a normal laxity or hyperlaxity. In voluntary dislocation, an aberrant muscle activation pattern is observed, the patient is able to demonstrate the phenomena and to repeat it with (Video), often, an amused mimic. There is no imaging finding.
B2: Structural dynamic posterior instability
The B2 includes unstable painful shoulder, involuntary and reproducible dislocators.
Unstable Painful Shoulder
This condition (micro-instability) is characterized by pain that appears without trauma, without macro-instability (subluxation or dislocation) in a patient that usually does not suffer from hyperlaxity.
Diagnosis is difficult and should not be confused with posterior static subluxation (B0 glenoid according to Walch) that belong to the type C2. Images are often relevant with 52% of reverse Bankart, glenoid or humeral cartilage lesions (28% and 8%, respectively) reported (Video).
This type of instability is associated with a clear first traumatic episode. The patient is able to reproduce the painful subluxation/dislocation if not locked. A radiological substrate is found.
Reproducible (B2) are voluntary dislocators (B1) that become involuntary after decompensation by a trauma or after losing control of stability. If asked, the patient can reproduce the movement even if the excessive glenohumeral translation leads to symptoms which are sudden, painful and disagreeable (Video). A radiological substrate can be found.
C1: Constitutional static posterior instability
Glenoid dysplasia is an idiopathic and congenital glenoid retroversion of dysplastic origin. In these conditions the humeral head remain posteriorly subluxated (Walch C glenoid). The retroversion is above 25 degrees, the subluxation above 80%. The posterior rim appears rounded (lazy J). There is moreover a deficient glenoid neck, a hypoplasia of the posteroinferior glenoid, minimal osteophytes, and a preserved joint space in comparison to osteoarthritis.
C2: Acquired static posterior instability
This group includes static posterior subluxation, locked dislocation, sequelae of brachial plexus birth palsy,…
Static Posterior Subluxation
The finding of static posterior subluxation of the humeral head before the development of posterior bone erosion of the glenoid in young men with radiographic findings of primary osteoarthritis has been described as arthrogenic (pre-osteoarthritic) posterior subluxation of the humeral head, or Walch B0 glenoid. This condition could be initially dynamic, eventually evolving into a static condition and may lead to posterior erosion of the glenoid, taking place once there is asymmetrically increased posterior glenohumeral contact forces and possibly associated with increased glenoid retroversion (Figure 9).
Sequelae of brachial plexus birth palsy
Obstetric brachial plexus palsy (OBPP) frequently leads to secondary glenohumeral dysplasia (Video).
Injuries typically occur:
- As a consequence of a contact sport or motor vehicle accident. Patients will classically sustain a posteriorly directed force when participating in activities that place their extremity in the at-risk position of anterior forward flexion, adduction, and internal rotation (football players and weightlifters performing bench press or pushups). Interestingly, contact with anterior trauma to an abducted and externally rotated shoulder might also be responsible for posterior dislocations.
- After a violent fall.
- After seizures, electric shocks or alcohol intoxication because of uncoordinated muscle contraction (the internal rotator muscles of the shoulder contract with greater force than the external rotators, which causes the humeral head to move superiorly and posteriorly). Anterior dislocation is, however, more frequent in case of seizure.
Risk factors for recurrent instability are:
- Age below 40 at time of first instability. Age is considered an important factor for possible associated lesions. Often, younger patients do not have associated lesions (i.e. rotator cuff), unlike older patients, and consequently, the treatment algorithm for these patients is different. Furthermore, a locked dislocation in an older patient may have different surgical solutions.
- Dislocation during a seizure or electric shock.
- A large reverse Malgaigne (Hill-Sachs) lesion.
- Glenoid retroversion. Please also refer to “Anatomy, Pathoanatomy” section.
- A high and horizontally oriented acromion in the sagittal plan. Please also refer to “Anatomy, Pathoanatomy” section.
A thorough history taking is imperative for making an accurate diagnosis of posterior shoulder instability. A detailed description of the offending activity, the position of the arm, and how force was applied may lead the clinician to an accurate diagnosis (please also refer to Etiology section).
In acute or subacute situations, patients report pain with active motion and particularly limited external rotation of the arm. It may mimic a frozen shoulder on examination, especially in cases with an unreduced dislocation.
In recurrent situations, symptoms that are commonly reported are muscle weakness and fatigue, pain, or mechanical symptoms such as clicking or popping. Symptoms intensify with the arm in 90 degrees of forward flexion, adduction, and internal rotation. Rarely do patients report clear sensations of instability or posterior shoulder pain associated with the feeling of a dead arm.
A detailed physical examination of the shoulder will assist the clinician in accurate diagnosis of posterior instability.
Examination should begin with inspection, looking for any asymmetry or atrophy of the musculature. Scapular winging also needs to be assessed while the patient is performing active range of motion as it is a sign of posterior dislocation (Video 5).
Cooper first reported the signs of posterior shoulder dislocation as the appearance of posterior fullness on the affected side.
Range of Motion
Shoulder passive and active range of motion should be assessed and compared with the contralateral shoulder. A loss of external rotation must be excluded.
The jerk test (posterior stress test) has been considered to be highly sensitive for posterior instability. This test is performed by stabilizing the scapula with one hand, while the other hand holds the elbow with the arm in 90 degrees of abduction and internal rotation (Figure 12). A firm axial compression force is applied on the glenohumeral joint. The arm is horizontally adducted while maintaining the firm axial load. This will cause a posterior translation of the humeral head and as the arm is brought into extension a painful clunk may be appreciated as the humerus reduces and is indicative of a posterior labral tear.
SLAP Lesion Test
A further test for posterior instability is the so-called Kim test, which is a modification of the jerk test.
The patient is supine with the arm abducted at 120 degrees. The examiner takes the patient's wrist with one hand and the elbow flexed at 90 degrees in the other. The shoulder is brought into external rotation. The patient is then asked to flex his elbow against resistance (Figure 13). A positive examination is represented by either pain, a clunk, or a click and indicates either the presence of a superior labral tear from anterior to posterior (SLAP) lesion or a posterior instability.
The test is performed with the patient in a sitting position and their arm in 90 degrees of abduction. The examiner holds the elbow and lateral aspect of the proximal arm and applies a strong axial load in line with the scapula. While maintaining the axial load, the arm of the patient is elevated 45 degrees diagonally upward and a posterior force is applied to the proximal arm. The test is positive if the patient complains of pain during this maneuver.
The jerk and the Kim tests are important and help deciding between nonoperative and operative treatment. The combination of a painful jerk and Kim tests has been shown to be 97% sensitive for the detection of a posteroinferior labral lesion. Patients with a painful jerk or Kim test have approximately 85% chance of not improving with rehabilitation and arthroscopic treatment with capsuloplasty is recommended.
Active Compression Test (better known as O’Brien’s test)
It is an active elevation against resistance, with the patient standing, shoulder flexed at 90 degrees and adducted at 15 degrees, elbow extended (Figure 14). The test is considered positive if there is pain in pronation but not in supination. This is the most sensitive (47% to 78%), but the least specific (11% to 73%) test. When testing negative, a superior labral tear from anterior to posterior (SLAP) lesion is very unlikely.
Assessment of generalized ligamentous laxity should be performed as this can predispose patients to instability events. The Beighton score is used to assess generalized ligamentous laxity, which has been shown to correlate with shoulder instability. The 5 included criteria are: (1) hyperextension of the elbow beyond 10 degrees; (2) hyperextension of the knees beyond 10 degrees; (3) forward flexion of the trunk, with knees straight, so that palms rest easily on the floor; (4) passive dorsiflexion of the little finger beyond 90 degrees; and (5) passive apposition of the thumbs to the flexor aspects of the forearm. This system is based on a 9-point scale and a higher score (>4) indicates general hyperlaxity (although an external rotation elbow at the side equal or greater than 85 degrees indicates shoulder hyperlaxity (Video 6)).
The diagnosis of this injury is often missed at initial examination, despite highly suggestive injury circumstances, notable clinical signs and radiographic evidence.
The views that should be included in the workup are a true anteroposterior view (grashey view), internal and external rotation view, a scapular Y view, and a Bernageau view. Posterior dislocation is missed initially on posteroanterior radiographs in 50% of cases, as the humeral head appears to be almost normally aligned with the glenoid.
On anteroposterior view, an overlap of the head in relationship to the glenoid can be observed (trough line sign, loss of the normal half-moon overlap sign, Figure 15). Moreover, an internally rotated humeral head gives a rounded appearance, which is called the lightbulb sign. Furthermore, the rim sign is defined as the space between the anterior glenoid rim and the humeral head being > 6 mm indicating a widened glenohumeral space (Figure 16).
Scapular Y View (Neer)
The scapular Y view can demonstrate a posterior translation of the humeral head (Figure 18).
As a Bernageau view is difficult to obtain in acute cases because of severe pain, Velpeau axillary views is an alternative (Figure 19).
Bernageau view is the best to demonstrate posterior glenoid rim deficiency posterior subluxation and associated bone loss.
Magnetic Resonance Arthrogram (MRA)
Contrast enhancement during magnetic resonance arthrogram (MRA) is of great value and will increase the sensitivity of magnetic resonance imaging (MRI) in identifying a soft tissue injury (cartilage, rotator cuff, labral tears (Figure), a patulous capsule (Figure), reverse humeral avulsion of the glenohumeral ligaments (rHAGL, Figure), associated findings such as paralabral cysts) (Figure).
Computed Tomography (CT) Scan
Computed tomography (CT) scans also help the physicians to analyze the bony morphology of the shoulder joint. Before operative management, it is effectively imperative to assess for abnormalities in glenoid version (mean, 4.9 degrees in normal shoulders) according to the Friedman technique, posterior glenoid rim fractures or bone loss, and reverse Malgaigne (Hill-Sachs) lesions. These factors help determining the treatment strategies.
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.
Conservative (Non Operative) Treatment
As an initial treatment, for all acute posterior dislocations, acute reduction and immobilization should be attempted. Most acute dislocations have a chance to reduce with closed manipulation. The reduction maneuvers must be done gently and carefully. In order to reduce the humeral head into the glenoid fossa, forward pressure on the humeral head must be applied with the arm in the flexed, adducted and internally rotated position. After reduction, an immobilization is required during 6 to 8 weeks in neutral or 20 degrees of external rotation, depending on the stability.
Patients with A1-C1 type of instability tend to have a more favorable result with conservative measures. Voluntary posterior dislocators should not be operated on. Management begins with activity modification to prevent further injury, medications as needed and physiotherapy.
Physical therapy is focused on strengthening of the subscapularis that will maintain the humeral head anteriorly, posterior deltoid, and the periscapular stabilizers through resisted external rotation exercises. The aim is to improve the neuromuscular control of the shoulder joint and to regain dynamic muscular stability.
Isokinetic muscle performance testing can assess muscle strength and neuromuscular control ability using time to peak torque and acceleration time in patients with traumatic shoulder instability. The injured shoulder usually shows delayed neuromuscular control in rotations. This information helps clinicians and therapists to implement exercises that aim to restore neuromuscular control in patients' rehabilitation.
Functional shoulder instability is caused by underactivity of rotator cuff and periscapular muscles, which leads to subluxation or dislocation during shoulder movement. The goal is thus to stimulate underactive muscles in patients with functional instability during shoulder movement in order to re-establish glenohumeral stability and to decrease pain. This can be performed by different modalities such as transcutaneous electrical nerve stimulation (TENS), Berlin shoulder pacemaker,...
Shoulder braces or posture correctors and supports that can center the arm in the socket through improved proprioception and reafferentation. Depending of their design, they can provide secure stability during movement. This type of support could help athletes to return to sport.
Surgical (Operative) Treatment
Open reduction and surgical stabilization
Open reduction is indicated in dislocations in which closed reduction cannot or should not be achieved. Several conditions are contraindications (i.e. if fracture dislocation). Reverse Malgaigne (Hill-Sachs) lesions > 25% of the humeral head articular surface in size are often unstable after closed reduction and they also require surgical intervention. Open reduction and surgical stabilization are indicated in such cases with defects 25% to 45% of the humeral head articular surface.
The deltopectoral approach is used to reconstruct the humeral head bony defect by the transfer of the subscapularis tendon with transosseous sutures described by McLaughlin or by suture anchors described by Spencer and Brems. The posterior subdeltoid approach can also be used and this approach lets the surgeon to fill the defect with autograft and perform a Bankart type capsulorrhaphy. If the injury is < 3 weeks old, disimpaction and bone grafting of the defect can be performed. For any glenoid bone loss, an iliac crest bone graft can be used as a block and both approaches can be preferred.
Arthroscopic reduction and surgical stabilization
Arthroscopic treatment of a humeral head fracture.
Patients who have undergone at least 6 months of conservative treatment and still experience symptoms are candidates for surgical management. Surgical treatment can be considered for the patient with a symptomatic posterior labral tear, unilateral posterior instability with a patulous or incompetent posterior capsule, or in select multidirectional instability patients with predominantly posterior symptoms. Nevertheless, if conservative measures fail then operative management should be considered in those with identifiable pathology. Surgery is required in cases of persistent shoulder pain in chronic instability, in patients with a locked neglected chronic dislocation, or in patients with associated lesions developing a dysfunctional shoulder. There are 2 broad categories of surgical management that focus on either the soft tissue or bony anatomy.
Soft tissue procedure
Labral Repair and Capsular Shift
In patients with purely soft tissue injuries and no associated bone loss or fracture, then posterior capsulorraphy (i.e., capsular shift) and labral repair are the treatments of choice. The use of arthroscopy in these cases has greatly surpassed that of open procedures primarily due to the less-invasive nature of the procedure, improved shoulder mechanics postoperatively, decreased scarring, and the ability to address concomitant lesions including posterior humeral avulsions of the glenohumeral ligament. It may reveal subtle lesions such a small crack or fissuring within the posterior labrum (hidden lesion or “Kim lesion”) (Video).
An arthroscopic labral repair is most commonly performed using suture anchor fixation. This often requires the use of 3 to 4 portals to allow for proper anchor positioning and shuttling of sutures. The standard posterior, anterior, and anterosuperior portals are initially created for visualization. In patients in whom the position of the posterior portal is not optimal for working and for achieving angle for glenoid rim access, a 7 o’clock portal or posteroinferior portal is placed under spinal needle localization. This portal has been found to be a safe distance from the axillary and suprascapular nerves. Once all portals have been created the labrum can be prepared through both the posterior and anterior portals. The posterior labrum is then mobilized off the glenoid neck using an elevator or arthroscopic scissor. It should be completely elevated from the glenoid to allow for superior translocation and preparation of the glenoid neck. The rim and neck of the glenoid are debrided with a shaver or a rasp. Repair of the labrum should begin at the most inferior extent of the tear. The anchor is placed slightly superior to allow for a superior shift of the tissue. Anchors should be spaced 3–5 mm apart to avoid fragmentation of the posterior glenoid bone. In patients with a patulous capsule an arthroscopic capsular shift may be performed in conjunction with a labral repair and consists of tightening any redundant posterior capsular tissue. Usually approximately 1 cm of capsule is plicated to the labrum. The exact amount of capsular plication must be individualized to the patients symptoms and over laxity as seen arthroscopically. This should begin at the 6 o’clock position and work in the direction of the 12 o’clock position (Figure).
In some cases, the labrum may be intact and the pathology may be related only to a capsular detensioning. In these cases, the capsular tissue may be lightly abraded with a rasp or with a shaver and capsular retensioning is carried out using the labrum like an anchor. Frequently, a combined labral repair and capsular shift are performed simultaneously and fixated with a suture anchor. In patients with chondral damage leaving exposed glenoid bone, the anchors may be placed slightly further onto the glenoid face to advance the labrum over the chondral defect providing a soft tissue inter-position while repairing the labrum.
Rotator Interval Closure
Treatment of Anterior Humeral Head Defects
Reverse Malgaigne (Hill–Sachs) Rempissage
In some cases of posterior instability, a large reverse Malgaigne (Hill-Sachs) lesion may be encountered. If involving more than 20% of the articular surface, a reverse Malgaigne (Hill-Sachs) remplissage may be considered to enhance stability of the joint. The rotator interval is resected to improve visualization of the anterior aspect of the subscapularis tendon (Video 10). The bone bed is therefore prepared as performed during subscapularis tendon repair (Video 11). Anchor(s) is(are) inserted, the sutures are passed through the subscapularis tendon and tied to fill the bone defect (Video 12).
McLaughlin Procedure (Open Transfer of the Subscapularis Tendon)
One of the earliest described techniques involves transferring the tenotomized subscapularis tendon to the humeral defect (from 25% to 45% of the humeral head articular surface) and is known as the McLaughlin procedure. Hawkins et al reported that if the period of delay is > 6 months, the articular cartilage of humeral head gets non-viable; therefore, the McLaughlin procedure should not be preferred.
Arthroscopic McLaughlin Procedure
Osteotomy of the Lesser Tuberosity With the Attached Subscapularis (Hughes and Neer method)
Several authors modified McLaughlin’s method and described osteotomizing the lesser tuberosity with the attached subscapularis tendon and fixing it to the defective area. The modified McLaughlin method provides additional bony support for the defective area and is preferred for patients when the injury is older than three weeks. Depending on the importance of the bone loss, simultaneous iliac crest autograft, dry morselized allograft, fresh-frozen femoral head bone allograft can be perform.
The surgery is performed in a beach chair position. The deltopectoral approach is used. First, the biceps tendon is identified as a landmark for the bicipital groove. The lower edge of the subscapularis tendon is detected in order to mark lesser tuberosity. Osteotomy of the lesser tuberosity is performed from lateral to medial, starting from the bicipital groove to the defect of the humeral head. The lesser tuberosity with the attached subscapularis tendon is elevated in order to demonstrate the head and the glenoid. Reduction is performed and when achieved, the lesser tuberosity with the attached subscapularis tendon is fixed into the humeral head defect using ether screws, anchors or sutures. Reported results are usually excellent.
Humeral Reconstruction with Autograft or Allograft
Bone grafting is an unavoidable procedure in insufficient bone reserve to reconstruct the anatomical sphericity and preserve the stability of the reconstructed humeral head after locked posterior shoulder dislocations. Allo- and autografting are both described in the literature. Some authors advocated the use of allografts in obtaining the anatomical sphericity of humeral head rather than preferring non-anatomical techniques by using osteochondral allografts from fresh-frozen femoral heads. Especially in the case of larger defects of up to 50% and young patients with viable humeral bone reserve, fixation of the allografts in defective areas with partially threaded cancellous screws yielded excellent results. In case of bilateral posterior humeral head dislocations, harvesting osteochondral autograft from the side that will undergo hemiarthroplasty and using this graft on the contralateral side is also described in the literature by several authors. Allo- and autograft reconstructions have a good long-term follow-up.
Posterior Bone Block
Patients with glenoid dysplasia (retroversion >15 degrees) as well as patients with posterior glenoid defects are at increased risk for failure with soft tissue procedures due to altered underlying bony support. Numerous techniques have been reported to reconstruct the posterior glenoid, including iliac crest bone block (Figure), distal tibial allograft, glenoid allograft, pedunculated acromial graft, and distal clavicular autograft.
Bone Block through Posterior Approach (Open or Arthroscopy)
The standard open technique using iliac crest bone graft has been first described by Hindenach. While promising clinical results have been reported, the procedure is technically demanding, with complication rates up to 36%, including residual instability, osteolysis of the graft, persistant pain and development of osteoarthritis. Careful attention must be paid to the positioning of the bone block posteriorly. A biomechanical study showed that a posterior bone block may overconstrain the posterior shoulder and not adequately address inferior instability compared to arthroscopic repair techniques.
The posterior bone block procedure can be performed via the same approach or arthroscopically and is accomplished by fixating bone graft to the posterior glenoid rim to recreate the normal contour of the glenoid surface (Video 14). Osseous procedures have fallen out of favor as first line treatment options and are typically reserved for those who fail a soft tissue procedure or have significant bone loss or deficiency.
Arthroscopic Posterior Bone Block through Rotator Interval Approach
Following induction of anesthesia the patient is placed in the lateral decubitus position with a warming blanket applied. An iliac crest bone autograft is harvested prior to arthroscopy. A bicortical 25 mm long, 15 mm large and 10 mm thick bone graft is obtained from the ipsilateral iliac crest. Alternatively, the use of acromial spine autograft has been described. The side without cortex is the one which will be secured against the glenoid. Two 3.2 mm holes are drilled through the graft (Video). The size of the graft is 25 mm long, 15 mm large and about 10 mm thick. Three sutures are placed, one in each hole, and a third passing through both holes to the posterior side of the graft. One suture is placed in each hole of the graft and are tied so that there are sutures at the leading and trailing ends of the graft. These sutures will be used to shuttle the graft into the glenohumeral joint. Additionally, a third suture is passed through the two holes and exits the posterior aspect of the graft. This suture is helpful in maintaining orientation of the graft during shuttline. Attention is turned to the arthroscopic procedure. The arm is placed in balanced suspension with 20° to 30° of abduction and 20° of forward flexion. Standard three portal access to the glenohumeral joint is established including posterior, anterior, and anterosuperolateral portals. A 7 mm cannula is placed into the latter portal. A standard diagnostic arthroscopy using a 30° arthroscope is performed and the glenohumeral joint is then viewed through the anterosuperolateral portal. Quadrant landmarks of the glenoid at 3, 6, 9 and 12 o’clock are marked with an electrocautery, which is important to help correctly place the bone graft later in the procedure. The anterior - posterior glenoid width measured as the anterior - to - posterior distance between 7:30 and 4:30 on the glenoid face is determined with a calibrated probe. Viewing from a posterior portal, a shaver or electrocautery introduced from the anterosuperolateral portal are used to create a window in rotator interval to allow passage of the bone graft. Care is taken to preserve the medial sling of the biceps during this step. The arthroscope is returned to the anterosuperolateral portal for visualization of the posterior capsulolabral structures. The posteroinferior labrum is resected off the posterior glenoid neck from 6 to 10 o’clock for a right shoulder using a motorized shaver in the posterior soft point portal. After resecting the posterior inferior labrum, the posterior glenoid is prepared to be flat. The space between the posterior labrum and the posterior glenoid margin is enlarged to receive the bone graft. Traction maneuvers with the shaver lift the fibers of the infraspinatus obliquely away from the glenoid allowing excellent visualization of the posteroinferior glenoid. Occasionally, a 70° arthroscope is necessary to adequately visualize this area. The capsule is released from the glenoid until the infraspinatus fibers can be seen and so that the open space between the glenoid and the capsule is sufficient to allow the introduction of a 10 mm thick bone graft. The posterior glenoid neck is decorticated with a shaver or burr to create a flat surface suitable to graft incorporation. Particular attention is paid during this procedure to prevent suprascapular nerve injury by avoiding working greater than 14 mm medial to the glenoid. The knowledge of the precise length of the burr can help the surgeon to avoid technical errors. A spinal needle is inserted at 7 o’clock to determine the proper angle of approach for a posterolateral working portal. The skin incision for the anterior portal is enlarged to accommodate passage the bone graft. Via the anterior portal, the graft is passed through the rotator interval in an anterior to posterior direction. This is achieved by means of utilizing the previous sutures in a shuttling technique (Movie). The leading suture of the graft is delivered into the glenohumeral joint through the anterior portal and retrieved out the posterior portal. Pulling this suture shuttles the graft into the joint. Additionally, a Kocher clamp is used to grasp the graft and assist in delivering the graft. Once the graft lies inside of the joint, alternating tension on the three sutures orients the graft. Graspers can also be used to manipulate the graft into the interval between the posteroinferior glenoid and the capsule. The graft is placed at the posteroinferior aspect of the glenoid (between 6 and 9 o’clock for a right shoulder and between 3 and 6 o’clock for a left shoulder), the cancellous side facing the posterior glenoid. This “free hand” step is the most challenging part of the procedure. In our experience when the graft is introduced in the fossa between the glenoid and the capsule, it become sufficiently stable which the need to hold it in place. Once the bone graft lies flush to the glenoid or slightly overhanging out the glenoid, a spinal needle is used to obtain an angle of approach directly perpendicular to the prepared holes and parallel to the glenoid surface. One or two small punctures are usually necessary to address both tunnels. Then a small 4.5 mm cannula is used to place two 1.2 mm K-wires, one in each hole, and a 3.2 mm cannulated drill is used to overdrill the K-wires through the graft and glenoid. Before removing the drill, particular care is paid to maintaining the K-wires in place. The posterior to anterior K-wires be bicortical but care must be taken to avoid excessive penetration which could injury the anterior neurovascular structures or lung. The length of the screws is determined adding the thickness of the graft and the diameter of the glenoid. Two 4.5 mm cannulated screws are then passed over the K-wires with enough compression to secure the graft (Movie). Once the graft is appropriately placed with strong fixation, both K-wires are removed. If the bone graft is prominent, a burr is used to create a smooth congruent arch with the glenoid. Two to three double-loaded anchors are then inserted through the posterior portal along the posterior glenoid rim starting from inferior to superior. The sutures are passed antegrade or retrograde through the capsule without major capsular shift or plication as the bone graft mainly achieves the stability. This procedure closes the capsule to the native glenoid and thus renders the bone block extracapsular (Movie). This step is necessary to protect the humeral articular cartilage from a direct contact with the bone graft. After portal closure, a sterile bulky dressing is applied and postoperative radiographs are obtained. This technique provides excellent visualization of the glenohumeral joint and is accomplished with less damage to the rotator cuff and posterior deltoid compared to traditional open approaches. The results are generally good.
Glenoid (Scott) osteotomy
In rare circumstances, patients with increased glenoid retroversion may require correction with a posterior glenoid osteotomy. Scott osteotomy (posterior opening wedge osteotomy) is typically considered in patients with more than 25 degrees of retroversion. This is typically considered only in revision settings. Graichen et al. reported good or excellent results in 81% of 32 patients undergoing posterior glenoid osteotomy, with the best results in patients with atraumatic instability. However, 25% of patients developed postoperative osteoarthritis, highlighting that this procedure should be only considered in select circumstances.
A posterior opening wedge osteotomy is performed through a posterior approach with the incision typically located in the posterior axillary fold. An osteotomy is completed at the posteromedial neck of the glenoid leaving the anterior cortex intact for stability. A wedge of bone graft (either autograft or allograft) in then inserted to provide the predetermined amount of correction. The graft is then secured with either screws or plate and screws. Press fit grafting techniques have also been described.
Locked Dislocations, Static Posterior Dislocation or Glenoid Dysplasia
Figure: mettre reverse AWA
Derotational osteotomy of the humerus has been suggested as a procedure for younger patients with significant humeral head depression. The necessary criteria are a healthy articular cartilage, a humeral head defect involving < 40% of the articular surface, and a patient who is able to participate in an active rehabilitation programme. This technique is a viable option for younger age groups since it can facilitate rehabilitation by providing immediate stability.
Arthroplasty is a viable option in patients with a large humeral head defect and less bone reserve after locked posterior dislocation of the shoulder. If the defect is larger than 45% to 50% of the articular surface and if the glenoid cavity is intact in a chronic dislocation aged > 6 months, hemiarthroplasty is recommended. When concomitant glenoid damage or significant glenoid arthritis is present, total shoulder arthroplasty should be preferred. Reverse shoulder arthroplasty compared to anatomic has the advantage to solve the problem of instability at the same time.
Rare case of glenoid dysplasia can beneficiate from glenohumeral arthrodesis. Please refer to Glenohumeral Arthritis/ Arthrodesis section.
Postoperatively patients are placed into a neutral rotation splint, position that decreases stress on the posterior capsule (Figure 30). Immobilization is carried out for 6 to 8 weeks after surgery. Passive range of motion and active assist range of motion can then begin under the supervision of a physical therapist. Physiotherapy is focused on strengthening of the subscapularis that will maintain the humeral head anteriorly, posterior deltoid, and the periscapular stabilizers through resisted external rotation exercises. The aim is to improve the neuromuscular control of the shoulder joint and to regain dynamic muscular stability. Strengthening typically begins during the third postoperative month. Return to sports should be decided on a case-by-case basis but usually return is restricted until 6 months out from surgery.
Complications are specific to patient subsets and the technique of stabilization used. Chronic shoulder pain, allograft collapse, avascular necrosis, non-union, stiffness, omarthrosis and recurrent instability can be seen. Patients with recalcitrant epileptic seizures are more prone to redislocation.
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