Bony Lesion Severity in First-Time Posterior Shoulder Dislocation: The Role of Glenoid and Acromial Morphology

Background: The influence of acromial morphology on the severity of glenoid bone loss (GBL) and reverse Hill-Sachs lesions (rHSL) in patients with first-time traumatic posterior shoulder dislocations (PSD) remains unclear. Purpose/Hypothesis: The purpose of this study was to assess the relationship between glenoid and acromial morphology and the severity of bone lesions, posterior GBL, and rHSL, in patients with first-time posterior PSD. It was hypothesized that specific morphological parameters, including glenoid offset and depth, as well as posterior acromial height, correlate with the extent of GBL and rHSL. Study Design: Cross-sectional study; Level of evidence, 3. Methods: In this monocentric, retrospective study, 24 patients with first-time PSD treated at a level 1 trauma center between 2011 and 2020 were analyzed. Scapular and humeral morphology was assessed using computed tomography and magnetic resonance imaging. Key parameters included measurements of glenoid and humeral morphology and acromial position. The correlation between anatomic measurements was evaluated using Pearson and Spearman correlation coefficients. Statistical significance was set at P < .05. Results: A GBL was present in 66.7% of patients with 20.8% showing a GBL >10%, while 95.8% demonstrated an rHSL. Smaller glenoid offset correlated with a deeper rHSL ( r = −0.455; P = .03). Higher acromial position (posterior acromial height) correlated with larger GBL ( r = 0.611; P = .01). A deeper glenoid correlated with a larger rHSL surface area ( r = 0.624; P = .001). Reduced total acromial coverage showed a moderate negative correlation with GBL ( r = −0.520; P = .04), while posterior acromial coverage did not correlate significantly with GBL. Conclusion: A posterior GBL and an rHSL can often be detected after an initial traumatic PSD. A higher positioned acromion and reduced total acromial coverage were found to correlate with larger posterior GBL, while a deeper glenoid and smaller glenoid offset correlated with larger and deeper rHSL.