AJSM Webinar Series: Posterior Shoulder Instability: Understanding the Dark Side of the Shoulder (Recording)-AJSM Webinar Series: Posterior Shoulder Instability: Understanding the Dark Side of the Shoulder (Recording)

Video Transcription

Video Summary

The AJSM and AOSSM webinar "Posterior Shoulder Instability: Understanding the Dark Side of the Shoulder" featured expert panelists discussing clinical, surgical, and biomechanical insights into posterior shoulder instability (PSI), a condition often under-recognized compared to anterior instability but prevalent in young, active populations such as military and athletes.<br /><br />Key learning points included understanding anatomy, biomechanics, diagnostic challenges, and treatment outcomes. Posterior labral tears commonly present with pain rather than overt instability, requiring keen clinical suspicion. Epidemiologic data highlighted a notable incidence of PSI particularly among military cadets and collision sport athletes, with a significant proportion managed non-operatively or surgically.<br /><br />Non-operative management success is variable, with approximately half of patients progressing to surgery within years. Predictors of non-operative treatment failure include clinical signs of instability, increased humeral retroversion, posterior humeral head subluxation, glenoid dysplasia, and specific acromial morphologies. Progression of posterior glenoid bone loss was noted in patients treated non-operatively, underscoring concerns about delaying surgery.<br /><br />Long-term surgical outcomes from arthroscopic posterior labral repair are generally favorable, with most patients showing sustained improvement over 10-15 years. Failure rates vary by sport, with higher recurrence in female underhand pitchers and adolescent athletes. Surgical decision-making incorporates bone loss assessment wherein small to moderate posterior glenoid bone loss often responds to labral repair alone, whereas substantial defects (above 20-25%) may require bone block augmentation, respecting the unique trapezoidal morphology of the posterior glenoid.<br /><br />Biomechanical studies clarified that posterior bone loss affects shoulder stability differently than anterior defects, necessitating tailored reconstruction strategies. The novel "reverse glenoid track" and related concepts help define critical lesion sizes and guide management. Treatment of reverse Hill-Sachs lesions remains challenging, with procedures like the McLaughlin transfer used selectively.<br /><br />Management of PSI involves addressing capsulolabral pathology, optimizing scapular and rotator cuff function, and individualized surgical approaches, especially in throwers and patients with glenoid dysplasia. Multidisciplinary expertise and ongoing research continue to refine diagnosis and treatment to improve patient outcomes in this complex condition.

Keywords

Posterior Shoulder Instability

PSI

Posterior labral tears

Non-operative management

Arthroscopic posterior labral repair

Posterior glenoid bone loss

Reverse glenoid track

Biomechanical insights

Military and athletes

Surgical outcomes