AJSM Webinar Series: Posterior Shoulder Instability: Understanding the Dark Side of the Shoulder-Nonoperative Treatment of Isolated Posterior Glenohumeral Instability in an Active Military Population

Nonoperative Treatment of Isolated Posterior Glenohumeral Instability in an Active Military Population

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This study investigates risk factors and outcomes associated with nonoperative treatment of isolated posterior glenohumeral (shoulder) instability in an active military population. Posterior shoulder instability, often resulting from repetitive microtrauma common in activities like pushups and pressing movements, is increasingly recognized in young, active individuals. Despite its prevalence, data on factors predicting failure of nonoperative management and the progression of related bone loss are limited.<br /><br />A retrospective review analyzed 90 military patients aged 18-40, diagnosed via MRI with isolated posterior labral tears and treated nonoperatively for at least six months. Failure of nonoperative treatment was defined as requiring surgical stabilization or medical separation from duty. Morphologic features such as posterior glenoid bone loss (pGBL), glenoid retroversion, posterior acromial height (PAH), posterior acromial coverage (PAC), and posterior humeral head subluxation were measured and correlated with outcomes.<br /><br />Findings revealed a 47% failure rate of nonoperative management, with failed cases showing significantly greater posterior humeral head subluxation and morphologic differences—higher PAH, less PAC, greater glenoid retroversion, and higher pGBL. Repeat MRIs (~1 year later) in 17 patients demonstrated a statistically significant progression of pGBL, suggesting that prolonged nonoperative management is associated with worsening glenoid bone loss.<br /><br />These results highlight that certain morphologic features—particularly increased PAH, decreased PAC, greater posterior humeral head subluxation, and glenoid retroversion—are predictive of nonoperative treatment failure. The progression of pGBL with nonoperative care may impair shoulder stability further and jeopardize future surgical outcomes.<br /><br />The study suggests that while nonoperative management is common, it may incur a high failure rate, especially in patients with specific anatomic risk factors. This advocates for careful assessment of glenohumeral morphology during initial evaluation and may justify earlier surgical intervention in high-risk individuals to prevent progression of bone loss and instability. Limitations include its retrospective design, military-specific population limiting generalizability, and small sample size for serial imaging. Further prospective research is needed to refine optimal management pathways for posterior shoulder instability.

Keywords

posterior shoulder instability

nonoperative treatment

military population

posterior glenoid bone loss

glenoid retroversion

posterior acromial height

posterior acromial coverage

posterior humeral head subluxation

treatment failure predictors

shoulder stability