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This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Overview¶

• Additional long-term randomized trials comparing beach-chair and lateral decubitus positions are needed to better understand the potential advantages and disadvantages of surgical positioning for posterior shoulder stabilization [1].
• Successful correction of scapular anatomy via osteotomies can improve static subluxation and restore subjective and objective shoulder stability at a minimum of 2 years [2].
• Defined thresholds for clinical significance provide a guideline for interpreting patient outcomes following arthroscopic stabilization, allowing for earlier detection of recurrent posterior instability [3].
• The early and midterm results of arthroscopic stabilization of the shoulder for posterior instability are promising [4].
• Arthroscopic management of posterior-inferior shoulder instability has a successful track record and a minimal complication profile [6].
• A number of procedures have been developed over the past several centuries to address posterior shoulder instability as the pathology has become better understood [7].
• Coracoid morphology differs significantly in patients undergoing posterior shoulder stabilization compared to patients undergoing surgery for anterior instability or a comparison cohort [9].
• Posterior bone block augmentation for recurrent posterior shoulder instability does not reliably yield substantial improvements in patient-reported outcomes [10].
• Complications are frequently observed with posterior bone block augmentation for recurrent posterior shoulder instability [10].
• Arthroscopic stabilization of posterior shoulder instability results in good outcomes with high patient satisfaction [11].
• Arthroscopic stabilization of posterior shoulder instability is associated with low rates of recurrent instability, revisions, and residual pain [11].
• Arthroscopic surgical techniques have facilitated successful management of both recurrent posterior subluxations and frank posterior instability [12].
• There is a high rate of return to sport after arthroscopic posterior shoulder stabilization [15].
• Return to sport after arthroscopic posterior shoulder stabilization occurs ranging from 4.3 to 8.6 months after surgery [15].

Anatomy & Pathophysiology¶

Bony Anatomy¶

• The glenoid is a convex structure of shallow depth shaped like an inverted pear [35].
• The glenoid averages 5° of retroversion in relation to the axis of the scapular body [38].
• The subchondral bone of the glenoid is relatively flat, with articular concavity augmented by cartilage and a circumferential labrum [38].
• The humeral head averages 19° of retroversion and 41° of inclination (neck-shaft angle) [38].
• The humeral head is spherical with a diameter of 37 to 57 mm [35].
• The humeral version averages 29.8 degrees (range, 10 to 55 degrees) [35].
• The head is inclined approximately 130 degrees with respect to the humeral shaft [35].
• The neck-shaft angle measures an average of 135 degrees [36].
• The humeral head is retroverted an average of 30 degrees [36].
• The glenoid cavity is a shallow socket, approximately one third the size of the humeral head [36].
• Patients with constitutional static posterior shoulder instability (Type C1) differ from healthy controls regarding osseous scapular and humeral morphology, scapulothoracic orientation, and shoulder girdle muscle distribution [60].
• The acromion acts as a mechanical buttress to posterior humeral head displacement [57].
• Glenoid as well as acromial malalignment alone is associated with pathological posterior translation of the humeral head across the glenoid upon simulated active elevation [54].
• Glenohumeral contact patterns highly depend on the amount of glenoid retroversion and posterior labral and/or bony glenoid integrity [55].

Soft Tissue Anatomy & Ligaments¶

• The posterior capsule is thin [49].
• The posterior capsule and the buttress provided by the posterior glenoid labrum are the primary static stabilizers to unidirectional posterior translation [49].
• Dynamic posterior stability is conferred by the rotator cuff musculature [49].
• The most consistent finding in patients with recurrent posterior subluxation is a patulous posterior capsule [49].
• The posterior capsule either stretches over time or tears as a result of single event trauma and heals in an elongated position, thereby increasing capsular volume [49].
• Posterior labral tears associated with recurrent posterior subluxation are generally degenerative tears rather than rare capsular and labrum avulsions (reverse Bankart lesions) [49].
• The posterior band of the inferior glenohumeral ligament (IGHL) is a primary static restraint against posterior-inferior translation in internal rotation and adduction [38].
• The posterior band of the IGHL is thinner than the anterior band of the IGHL [62].
• The posterior capsule, particularly the posterior band of the IGHL, is intimately associated with the posterior labrum in creating a compressive force across the glenohumeral joint [62].
• The long head of the biceps has a pertinent biomechanical role in glenohumeral stability regardless of the condition of the superior labrum [58].
• The glenoid labrum provides concavity and up to 50% of marginal glenoid socket depth [38].
• The rotator interval is defined medially by the base of the coracoid, superiorly by the supraspinatus tendon, and inferiorly by the subscapularis tendon [38].
• The rotator interval contains the coracohumeral (CH) ligament, the superior glenohumeral ligament (SGHL), and the intra-articular portion of the long head of the biceps tendon [38].
• The CH ligament restricts external rotation in adduction and is a static restraint to inferior and posterior translation in adduction and external rotation [38].
• The SGHL is a primary static restraint against anterior translation with the arm at the side [38].
• The middle glenohumeral ligament (MGHL) is a primary static restraint against anterior translation with the arm in external rotation and 45° of abduction [38].
• The anterior band of the inferior glenohumeral ligament (AB-IGHL) is a primary static restraint against anterior-inferior dislocation of the glenohumeral joint in 90° of abduction and external rotation [38].
• The subscapular bursa lies between the subscapularis tendon and the neck of the scapula and communicates with the joint cavity between the superior and middle glenohumeral ligaments [39].
• The subscapular bursa is linked to the coracoid process by a suspensory ligament [39].
• In 28% of dissected specimens, the subscapular bursae merged with the subcoracoid bursae, forming a unique wide bursa [39].

Pathophysiology & Biomechanics¶

• The glenohumeral joint relies upon a ‘‘concavity-compression’’ mechanism to remain concentrically reduced [18].
• Glenoid retroversion, glenoid dysplasia, posterior glenoid bone defects, dynamic glenoid malpositioning due to loss of normal scapular mechanics, and loss of normal compressive forces can all contribute to posterior instability [18].
• Posterior translation is highly sensitive to small degrees of posterior glenoid defects or retroversion [18].
• Recurrence of instability after surgery is reliably related to either a failure to address one of the glenohumeral stabilizers at the time of primary stabilization or the development of a new lesion in one of these structures [18].
• Relevant lesions contributing to recurrence include deficiency or malpositioning of the glenoid fossa, tearing or attenuation of the posterior labrum, and laxity within the anterior or posterior capsuloligamentous structures [18].
• Posterior shoulder instability is a dynamic problem that may be caused or aggravated by mechanical factors, many of which mirror problems found in anterior instability [27].
• It is not completely clear what the individual contribution is from each of the different mechanical factors because many of these are also present in asymptomatic patients [27].
• The PPS injury produces alterations in glenohumeral kinematics with implications for glenohumeral joint instability, increased joint loading, and potential joint damage [56].
• Static posterior subluxation is a fixed posterior position of the humeral head on the glenoid fossa on CT or MRI scans with the arm in neutral rotation [47].
• Static posterior subluxation is most frequently but not always associated with congenital dysplasia of the glenoid or with degenerative glenohumeral joint disease [47].
• Static posterior subluxation may be associated with glenoid deformations such as those classified by Walch and co-workers [47].
• Static posterior subluxation may be present without any rotator cuff deficiencies [47].
• Most authors have found static posterior subluxations to be irreversible [47].
• Acquired recurrent posterior subluxation is defined based upon the anatomic lesion, as the etiology is not as crucial to treatment as the underlying pathologic lesion [49].
• Lesions of the capsule, labrum, rotator cuff musculature, and glenoid can contribute to recurrent posterior subluxation [49].
• The most consistent deficiency in acquired recurrent posterior subluxation relates to redundancy of the posterior capsule [49].
• Dysfunction of normal scapulothoracic mechanics can place the glenohumeral joint at risk for recurrent instability [49].
• The serratus anterior muscle plays a key role in scapulothoracic rhythm, and its paralysis results in scapular winging and loss of power in elevation that potentially may influence glenohumeral stability [49].
• In patients with glenohumeral instability and lesser degrees of scapulothoracic dysfunction, it is unclear whether instability is the result of altered scapulothoracic mechanics or the cause of it [49].
• Posterior glenoid rim deficiency is an uncommon cause of acquired posterior subluxation but should be investigated with imaging studies if suspected [49].
• The relation between the degree of posterior glenoid erosion and recurrent posterior subluxation has not been established [49].
• It seems reasonable to assume that a large posterior glenoid defect will compromise the buttress effect of the glenoid to posterior translation [49].
• Microtraumatic posterior shoulder instability is typically caused by repetitive loading of the shoulder in a combination of flexion, adduction, and internal rotation [64].
• The mechanism of injury associated with microtraumatic posterior shoulder instability in baseball players is termed “batter's shoulder” [64].
• Repetitive forces acting on the posterior glenohumeral joint capsulolabral complex and rotator cuff can result in posterior capsulolabral lesions, deformation, and articular surface rotator cuff tears [64].
• Rotator cuff tears are extremely rare in association with posterior glenohumeral dislocation, regardless of patient age [27].
• Only 4 documented cases of rotator cuff tear following posterior shoulder dislocation have been reported in the literature [27].
• The attachment of the teres minor is vulnerable and may become either partially or completely avulsed in posterior dislocations [27].
• Delayed diagnosis is common in posterior glenohumeral dislocations [20].
• Reduction was achieved via open means in the majority of shoulders with posterior glenohumeral dislocation [20].
• Recognition of a posterior dislocation may be impaired by the lack of a striking deformity and the fact that the shoulder is held in the traditional sling position of adduction and internal rotation [24].
• Classic features of a posterior dislocation include limited external rotation (often to <0 degrees), limited elevation (often to <90 degrees), posterior prominence and rounding of the shoulder, flattening of the anterior aspect of the shoulder, and prominence of the coracoid process [24].
• With the passage of time, the posterior rim of the glenoid can further impact the fracture of the humeral head and produce a deep hatchet-like defect or a V-shaped compression fracture, which engages the head even more securely [24].
• Patients with old, unreduced posterior dislocations of the shoulder can have 30 to 40 degrees of glenohumeral abduction and some humeral rotation as a result of enlargement of the groove [24].
• Long-standing disuse of the muscles about the shoulder leads to atrophy, which accentuates the flattening of the anterior portion of the shoulder, the prominence of the coracoid, and the fullness of the posterior portion of the shoulder [24].
• The injury may be misdiagnosed as a frozen shoulder for which vigorous therapy may be mistakenly instituted in an attempt to restore range of motion [24].
• Electoshock, seizures, or a fall on the flexed and adducted arm are commonly associated with posterior dislocation [24].
• Female patients were significantly more likely to have posterior shoulder instability compared to male patients [13].
• At a minimum of 2 years, successful correction of scapular anatomy can improve static subluxation and restore subjective and objective shoulder stability [2].

Classification¶

• The ABC classification distinguishes three groups of posterior shoulder instability based on the nature of pathology: first-time, dynamic, or static [19].
• The ABC classification includes two different subtypes for each of the three main groups based on pathomechanical causes [19].
• The ABC classification aims to facilitate diagnosis and assist the treatment decision-making process for posterior shoulder instability [19].
• Clinical-entity coding of the 100 most cited articles on posterior shoulder instability indicates that chronic or recurrent instability dominates the literature, comprising 65% of cases [34].
• Locked posterior dislocations comprised a larger share of the top-cited literature set than acute traumatic posterior dislocations [34].
• Locked posterior dislocation is characterized by distinct bony pathology, including reverse Hill-Sachs lesions, delayed recognition, and uniquely defined operative decision-making [34].

Clinical Presentation¶

History and Mechanism¶

• The history should define the mechanism of injury, including the position of the arm, the amount of force applied, and the point of force application [24].
• Injury with the arm in extension, abduction, and external rotation favors anterior dislocation [24].
• In a posterior traumatic dislocation, the patient may report a direct blow with the arm in forward elevation, adduction, and internal rotation [48].
• If the instability is recurrent, the history defines the initial injury, the position or action that results in instability, how long the shoulder stays out, whether radiographs are available with the shoulder out of joint, and what means have been necessary to reduce the shoulder [24].
• The history also solicits evidence of neurologic or rotator cuff problems after previous episodes of shoulder instability [24].
• Previous treatment of the recurrent instability, as well as the effectiveness of this treatment, should be documented [24].
• Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays [5].
• Bilateral posterior shoulder dislocations with reverse Hill-Sachs lesions are uncommon and prone to misdiagnosis [59].

Physical Examination: Inspection and Deformity¶

• Recognition of a posterior dislocation may be impaired by the lack of a striking deformity of the shoulder and by the fact that the shoulder is held in the traditional sling position of adduction and internal rotation [24].
• Classic features of a posterior dislocation include limited external rotation of the shoulder, often to less than 0 degrees [24].
• Classic features of a posterior dislocation include limited elevation of the arm, often to less than 90 degrees [24].
• Classic features of a posterior dislocation include posterior prominence and rounding of the shoulder in comparison to the normal side [24].
• Classic features of a posterior dislocation include flattening of the anterior aspect of the shoulder [24].
• Classic features of a posterior dislocation include prominence of the coracoid process on the dislocated side [24].
• Asymmetry of the shoulder contours can often best be visualized by viewing the shoulders from above while standing behind the patient [24].
• With long-standing disuse of the muscles about the shoulder, atrophy will be present, which accentuates the flattening of the anterior portion of the shoulder, the prominence of the coracoid, and the fullness of the posterior portion of the shoulder [24].
• The examination of the shoulder typically shows an inability to externally rotate the shoulder because of a mechanical block [25].
• The examination of the shoulder typically shows limited flexion and abduction [25].
• The dislocated arm is locked in internal rotation because the humeral head is fixed on the posterior glenoid rim [25].
• Abduction and forward elevation may be preserved up to 80 degrees or more in posterior dislocation [25].

Physical Examination: Motion and Diagnosis¶

• Motion is limited because the head of the humerus is fixed on the posterior glenoid rim by muscle forces, or the head might actually be impaled on the glenoid rim [24].
• In the interval before the diagnosis of posterior dislocation of the shoulder is made, the injury may be misdiagnosed as a frozen shoulder for which vigorous therapy may be mistakenly instituted in an attempt to restore range of motion [24].
• Hill and McLaughlin reported that in their series the average time from injury to diagnosis was 8 months [24].
• Initial examination should include a complete neurovascular examination to document any neurologic or vascular deficits [50].
• Documentation of active and passive ROM of the shoulder for internal and external rotation as well as forward flexion and abduction is important [50].
• Marked loss of motion is seen with persistent dislocations and rotator cuff lesions [50].
• The evaluation of the shoulder with a recent dislocation event can be challenging due to pain, but substantial motion loss mandates orthogonal radiographic imaging [50].
• Rotator cuff testing is an essential part of the shoulder instability examination particularly in patients over the age of 40 years as the incidence of rotator cuff lesions increases [50].
• The belly press or bear hug test is the most effective test to evaluate the function of the subscapularis in the acutely injured patient [50].
• Testing of resisted shoulder abduction in the first 30 degrees of shoulder flexion with the arm internally rotated is effective for evaluating the supraspinatus [50].
• Evaluation of the infraspinatus is performed by applying resisted external rotation with the elbow flexed to 90 degrees [50].
• The most common complaint of shoulder instability is pain coupled with restricted shoulder motion [50].
• Patients with anterior shoulder instability will experience symptoms of apprehension with shoulder abduction and external rotation, and also can experience symptoms of pain and instability with placement of the arm in an overhead position [50].
• The load and shift test is used to evaluate anterior and posterior GH laxity and is performed while the patient is in a seated or supine position with the humeral head centered in the glenoid fossa and translated [48].
• Generalized joint laxity should also be assessed using the Beighton score (0–9 point scale) [48].

Imaging and Classification¶

• In patients with suspected posterior glenohumeral instability, imaging of the affected shoulder can show abnormalities of the bone, labrum, and joint capsule [29].
• The ABC classification distinguishes three groups of posterior shoulder instability based on the nature of pathology (first-time, dynamic, or static) and two different subtypes based on the pathomechanical causes [19].
• This classification aims to facilitate diagnosis and assist the treatment decision-making process [19].

Investigations¶

Imaging Modalities and Technique¶

• At least two X-ray views should be obtained: an anteroposterior in the plane of the glenoid and an axillary projection with the arm in abduction to show the relationship of the humeral head to the glenoid [43].
• The purpose of imaging of the shoulder is to help establish the diagnosis, determine the severity of the pathoanatomy, assist in surgical planning, and enable the surgeon to illustrate the condition of the shoulder to the patient [23].
• Unless a specific research protocol is in place, the temptation to “overimage” should be resisted, obtaining only the scans or reconstructions that are necessary for the care of the patient [23].
• Standardized plain films are almost always sufficient to garner the information needed, and there is information that can be gathered from properly taken plain films that cannot be obtained from CT scans [23].
• The first key radiographic view is the anteroposterior (AP) in the plane of the scapula taken so that the x-ray beam passes through the glenohumeral joint [23].
• The second key radiographic view is the axillary view taken with the arm in the functional position of elevation in the plane of the scapula and oriented so that both the spinoglenoid notch and the scapular neck are visible [23].
• The axillary view is referred to as the “truth view” because it demonstrates the glenohumeral relationships in the functional position of elevation [23].
• CT scans have the disadvantage of being taken with the arm in the adducted position, whereas the axillary truth view is taken with the arm in elevation [23].
• The degree of posterior subluxation can be measured as (1) the position of the center of the humeral head in relation to the plane of the scapula, (2) the position of the center of the humeral head in relation to the glenoid face, or (3) the point of contact of the humeral articular surface on the glenoid articular surface [23].
• The point of contact of the humeral articular surface on the glenoid articular surface reflects the degree of centering of the net humeral joint reaction force on the glenoid [23].
• Malcentering of the joint reaction force leads to posterior instability, posterior glenoid wear, and “rocking horse” loosening of prosthetic glenoid components [23].
• Magnetic resonance imaging (MRI) is useful to identify osteonecrosis of the humeral head, or a bone tumour [43].
• MRI can identify labral tears and rotator cuff tears, although the accuracy for these is enhanced by combining the scan with arthrography [43].
• Computed tomography (CT) is helpful for planning fracture surgery and shoulder joint replacement [43].
• Ultrasound is a simple and accurate test for identifying rotator cuff tears and calcific tendinitis [43].
• Ultrasound can be useful in guiding injections or barbotage (aspirating calcific deposits in the rotator cuff) [43].
• Arthroscopy is useful for diagnosing and treating subacromial impingement, intra-articular lesions, detachment of the glenoid labrum and rotator cuff tears [43].
• A robust approach to imaging the shoulder needs to recognize that the shoulder is a three-dimensional structure that cannot be represented by a single planar view [45].
• Critical relationships—such as the degree of centering of the humeral head—change with the position of the arm [45].
• Shoulder pathology may be found in a large number of different bones and soft tissues [45].
• Overlying and superimposed structures as well as metallic implants may complicate imaging the structures of interest [45].

Diagnostic Findings and Clinical Correlation¶

• Coracoid morphology differs significantly in patients undergoing posterior shoulder stabilization when compared to patients undergoing surgery for anterior instability or a comparison cohort [9].
• Regardless of the radiologist interpretation of MRA, patients with symptomatic posterior shoulder instability do benefit from arthroscopic stabilization surgery [21].
• Overall, reduction was achieved via open means in the majority of shoulders, and delayed diagnosis is common in posterior glenohumeral dislocations [20].

Treatment¶

Arthroscopic Stabilization¶

• Early and midterm results of arthroscopic stabilization for posterior shoulder instability are promising [4].
• Arthroscopic stabilization of posterior shoulder instability results in good outcomes with high patient satisfaction and low rates of recurrent instability, revisions, and residual pain [11].
• Arthroscopic management of posterior-inferior shoulder instability has a successful track record and minimal complication profile [6].
• Patients with symptomatic posterior shoulder instability benefit from arthroscopic stabilization surgery regardless of the radiologist interpretation of the magnetic resonance arthrogram [21].
• There is a high rate of return to sport after arthroscopic posterior shoulder stabilization, ranging from 4.3 to 8.6 months after surgery [15].
• The thresholds defined in a 2025 study provide a guideline for interpreting patient outcomes following arthroscopic stabilization for posterior shoulder instability, allowing for earlier detection of recurrent posterior instability [3].

Bone Block Augmentation¶

• The iliac posterior shoulder bone-block is effective in managing instances of involuntary posterior shoulder instability, showing satisfactory results in terms of non-recurrence, pain relief, and function recovery [8].
• Posterior bone block augmentation for recurrent posterior shoulder instability does not reliably yield substantial improvements in patient-reported outcomes, and complications are frequently observed [10].
• There is a moderate rate of recurrence following posterior bone block for posterior shoulder instability [14].
• Both glenoid osteotomy and bone block procedures can successfully address symptomatic posterior shoulder instability [30].
• An isolated reverse Bankart repair with a glenoid defect ≥20% is not sufficient to restore glenohumeral stability in a cadaveric model [31].
• In a group of 75 patients who underwent arthroscopic capsulolabral repair with a minimum follow-up of 24 months, a bone defect of 11% increased the risk of failure by 10.4 times, while a 15% defect increased it by 24.4 times [31].
• Posterior bone block techniques restore the glenoid surface and glenohumeral biomechanics, reducing posterior and posteroinferior translation of the humeral head [31].
• Indications for a posterior bone block include recurrent posttraumatic posterior instability, the presence of humeral and/or glenoid defects, and demonstrable non-voluntary instability with glenoid dysplasia or hypermobility [31].
• A glenoid defect ≥20% is proposed as a cut-off for posterior bone block techniques [31].

Open Surgical Techniques¶

• The modified McLaughlin surgical procedure involves a deltopectoral incision, osteotomy of the small tubercle medial to the biceps groove, and repair of the subscapularis tendon [66].
• In the modified McLaughlin procedure, the bone graft is sized to be at least 10 mm deep and 20 mm long to cover the humeral head defect [66].
• The duration of dislocation is the most important prognostic factor in chronic locked posterior shoulder dislocations treated with the modified McLaughlin surgical procedure [66].

Patient Positioning¶

• In a 2025 study on arthroscopic shoulder instability surgery in patients under 25 years of age, patients were positioned in lateral decubitus with 20° supination and upper limb in double traction [63].
• In a 2025 multicentre study on chronic locked posterior shoulder dislocations, operations were performed with the patient in the beach chair position [66].

Non-Operative Management¶

• NHL team physicians strongly favor nonoperative management in-season for initial posterior instability events of the shoulder [61].

Diagnostic and Prognostic Context¶

• Advances in understanding posterior glenohumeral anatomy and biomechanics have helped guide clinical decision making, including delineation of surgical indications and contraindications, nonsurgical treatment solutions, and appropriate stabilization and bone augmentation techniques [17].

Complications¶

Recurrence and Instability¶

• The high rate of persistent instability should be considered when making treatment decisions regarding glenoid osteotomy [72].
• Recurrence of instability after surgery is reliably related to either a failure to address one of the glenohumeral stabilizers at the time of the primary stabilization or the development of a new lesion in one of these structures [18].
• The most relevant lesions contributing to recurrence include deficiency or malpositioning of the glenoid fossa, tearing or attenuation of the posterior labrum, and laxity within the anterior or posterior capsuloligamentous structures [18].
• In a systematic review of the modified McLaughlin procedure for locked posterior dislocation, two episodes of recurrent instability occurred in two separate patients with epileptic seizures and moderate joint stiffness, representing 2.1% of the cohort [68].
• No episodes of recurrent dislocation were noted in any of the included studies for the modified McLaughlin procedure [68].
• In a minimum 10-year follow-up study of arthroscopic capsulolabral repair, 17.6% of shoulders required additional surgery, either for recurrent instability or progression of arthritis [52].

Surgical and Hardware Complications¶

• Posterior bone block augmentation for recurrent posterior shoulder instability is associated with complications that are frequently observed [10].
• In a systematic review of the modified McLaughlin procedure, postoperative complications occurred in one patient (1.0% of the cohort), specifically one episode of screw migration which was treated with operative removal [68].
• No episodes of humeral head necrosis or infection were documented in any study included in the systematic review of the modified McLaughlin procedure [68].
• Graft non-union with bent or broken screws is a potential complication of glenoid bone augmentation [65].
• Osteolysis or reabsorption of the proximal part of the grafts with prominent hardware is a potential complication of glenoid bone augmentation [65].
• In a review of 21 patients treated with posterior bone block, 4 showed osteoarthritis (19%) and 1 had bone graft lysis on postoperative X-rays [65].
• In a series of 8 patients who underwent posterior deltoid detachment and posterior bone block, 5 patients still referred pain at the latest follow-up [65].

Neurovascular and Soft Tissue¶

• Musculocutaneous, axillary, and suprascapular nerves are the surrounding structures at risk during glenoid bone augmentation [65].

Functional and Long-Term Outcomes¶

• Decreased range of motion is a potential complication of glenoid bone augmentation [65].
• Long-term degenerative changes and osteoarthritis are potential complications of glenoid bone augmentation [65].
• In a series of 8 patients treated with posterior bone block, competition players returned to their previous sport to a lower level, while occasional leisure players did not [65].

Recovery¶

• Arthroscopic stabilization of posterior shoulder instability resulted in good outcomes with high patient satisfaction and low rates of recurrent instability, revisions, and residual pain [11].
• Systematic review demonstrated high rates of return to sport and relatively high rates of return to preinjury level of sport among all athletes who underwent surgical treatment for posterior shoulder instability [32].
• Arthroscopic posterior Bankart repair for traumatic posterior shoulder instability in collision sports athletes resulted in a low recurrence rate, high return-to-play rate, and clinically meaningful improvement [69].
• Participants with microtraumatic posterior shoulder instability demonstrated significant improvements in patient-reported outcome measures and high rates of return to sport following a 24-week conservative rehabilitation program [28].
• The thresholds defined in the study can provide a guideline for interpreting patient outcomes following arthroscopic stabilization for posterior shoulder instability, allowing for earlier detection of recurrent posterior instability [3].

Key Evidence¶

• [L4] Additional long-term randomized trials comparing these positions are needed to better understand the potential advantages and disadvantages of surgical positioning for posterior shoulder stabilization. [1] (10.1177/2325967118822452)
• [L4] At a minimum of 2 years successful correction of scapular anatomy can improve static subluxation and restore subjective and objective shoulder stability. [2] (10.1016/j.jseint.2025.06.018)
• [L4] The thresholds defined in this study can provide a guideline for interpreting patient outcomes following arthroscopic stabilization for posterior shoulder instability, allowing for earlier detection of recurrent posterior instability. [3] (10.1016/j.jseint.2025.08.006)
• [L1] The early and midterm results of arthroscopic stabilization of the shoulder for posterior instability are promising. [4] (10.1016/j.arthro.2014.11.009)
• [L5] Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays. [5] (10.5435/00124635-200608000-00004)
• [L4] Arthroscopic management of posterior-inferior shoulder instability has a successful track record and minimal complication profile. [6] (10.1016/j.arthro.2018.06.057)
• [L5] Over the past several centuries, a number of procedures have been developed to address posterior shoulder instability, particularly as this pathology has become better understood. [7] (10.1016/j.jses.2019.08.008)
• [L4] The iliac posterior shoulder bone-block is effective in managing instances of involuntary posterior shoulder instability, showing satisfactory results in terms of non-recurrence, pain relief, and function recovery. [8] (10.1016/j.otsr.2008.09.008)
• [L3] Coracoid morphology differs significantly in patients undergoing posterior shoulder stabilization when compared to patients undergoing surgery for anterior instability or a comparison cohort. [9] (10.1177/03635465261421534)
• [L1] Posterior bone block augmentation for recurrent posterior shoulder instability does not reliably yield substantial improvements in patient-reported outcomes, and complications are frequently observed. [10] (10.1016/j.arthro.2021.07.018)
• [L4] Arthroscopic stabilization of posterior shoulder instability resulted in good outcomes with high patient satisfaction and low rates of recurrent instability, revisions, and residual pain. [11] (10.1016/j.jse.2024.04.006)
• [L5] The article outlines the evolution of diagnostic acumen and treatment algorithms for posterior shoulder instability, emphasizing that arthroscopic surgical techniques have facilitated successful management of both recurrent posterior subluxations and frank posterior instability. [12] (10.1016/j.csm.2008.06.001)
• [L4] Overall, male patients were significantly more likely to have anterior shoulder instability, while female patients were significantly more likely to have posterior shoulder instability. [13] (10.1177/23259671211006437)
• [L4] There is a moderate rate of recurrence following posterior bone block for posterior shoulder instability. [14] (10.1016/j.jse.2021.06.013)
• [L4] There is a high rate of return to sport after arthroscopic posterior shoulder stabilization, ranging from 4.3 to 8.6 months after surgery. [15] (10.1016/j.asmr.2020.08.007)
• [L5] Advances in understanding posterior glenohumeral anatomy and biomechanics have improved comprehension of this challenging disorder and helped guide clinical decision making, including delineation of surgical indications and contraindications, nonsurgical treatment solutions, and appropriate stabilization and bone augmentation techniques. [17] (10.5435/jaaos-d-15-00631)
• [L4] [18] (10.1016/j.jse.2012.11.019)
• [L5] [19] (10.1530/eor-24-0025)
• [L4] Overall, reduction was achieved via open means in the majority of shoulders, and delayed diagnosis is common. [20] (10.1302/0301-620x.101b1.bjj-2018-0984.r1)
• [L3] Regardless of the radiologist interpretation of MRA, patients with symptomatic posterior shoulder instability do benefit from arthroscopic stabilization surgery. [21] (10.1016/j.xrrt.2026.100675)
• [L4] [25] (10.1016/j.arthro.2011.06.015)
• [L4] [27] (10.1007/s00167-010-1293-z)
• [L4] Participants with microtraumatic posterior shoulder instability demonstrated significant improvements in patient-reported outcome measures and high rates of return to sport following a 24-week conservative rehabilitation program. [28] (10.1016/j.jseint.2024.09.016)
• [L5] In patients with suspected posterior glenohumeral instability, imaging of the affected shoulder can show abnormalities of the bone, labrum, and joint capsule. [29] (10.2214/ajr.07.3849)
• [L1] Both glenoid osteotomy and bone block procedures can successfully address symptomatic posterior shoulder instability. [30] (10.1016/j.xrrt.2025.03.004)
• [L5] [31] (10.1530/eor-22-0009)
• [L4] The systematic review demonstrated high rates of return to sport and relatively high rates of return to preinjury level of sport among all athletes who underwent surgical treatment for posterior shoulder instability. [32] (10.1016/j.jseint.2020.08.002)
• [L5] [34] (10.1016/j.xrrt.2026.100710)
• [L4] [52] (10.1177/23259671241312651)
• [L5] Glenoid as well as acromial malalignment alone is associated with pathological posterior translation of the humeral head across the glenoid upon simulated active elevation. [54] (10.1177/03635465251411312)
• [L5] Glenohumeral contact patterns highly depend on the amount of glenoid retroversion and posterior labral and/or bony glenoid integrity. [55] (10.1177/03635465251365497)
• [L5] The PPS injury produces alterations in GH kinematics with implications for GH joint instability, increased GH joint loading, and potential joint damage. [56] (10.1016/j.jse.2024.12.023)
• [L5] The acromion acts as a mechanical buttress to posterior humeral head displacement. [57] (10.1016/j.jse.2024.09.047)
• [L5] The long head of the biceps has a pertinent biomechanical role in glenohumeral stability regardless of the condition of the superior labrum. [58] (10.1016/j.arthro.2025.05.022)
• [L4] Bilateral posterior shoulder dislocations with reverse Hill-Sachs lesions are uncommon and prone to misdiagnosis; early recognition and tailored treatment strategies are essential for satisfactory functional outcomes. [59] (10.1186/s12891-026-09537-y)
• [L3] Patients with C1 shoulders differ from healthy controls regarding osseous scapular and humeral morphology, scapulothoracic orientation, and shoulder girdle muscle distribution. [60] (10.1177/03635465241233706)
• [L4] NHL team physicians strongly favor nonoperative management in-season for initial posterior instability events of the shoulder. [61] (10.1177/23259671261440208)
• [L5] [62] (10.5435/jaaos-d-19-00535)
• [L4] [63] (10.1186/s13018-025-05546-0)
• [L4] [64] (10.1016/j.jisako.2025.101015)
• [L5] [65] (10.1136/jisakos-2019-000413)
• [L4] [66] (10.1186/s12891-025-08886-4)
• [L4] [68] (10.1016/j.xrrt.2023.08.007)
• [L4] Arthroscopic posterior Bankart repair for traumatic posterior shoulder instability in collision sports athletes resulted in a low recurrence rate, high return-to-play rate, and clinically meaningful improvement. [69] (10.1016/j.asmr.2025.101264)
• [L4] However, the high rate of persistent instability should be considered when making treatment decisions. [72] (10.1177/17585732211056053)

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