Glenoid Retroversion as a Protective Factor Against Recurrent Anterior Shoulder Instability Following First-Time Traumatic Dislocation. A Retrospective Analysis.

INTRODUCTION: Recurrent anterior shoulder instability is a common complication after first-time traumatic dislocation, particularly in young patients treated conservatively. While established risk factors include age and osseous defects, the influence of glenoid morphology - specifically glenoid version remains incompletely understood. The purpose of this study was to evaluate whether glenoid version is associated with recurrent instability following nonoperative treatment of first-time anterior shoulder dislocation. METHODS: This retrospective study included 72 patients (aged 18-40 years) with first-time traumatic anterior shoulder dislocation treated nonoperatively between 2019 and 2025. Patients were divided into a single-dislocation group and a recurrent-instability group. Glenoid morphologic parameters were assessed on axial MRI images by one blinded investigator. RESULTS: Patients in the single-dislocation group demonstrated greater glenoid retroversion than patients with recurrent instability (-2.2° ± 4.2° vs. -4.4° ± 4.0°; 95% CI, -4.08 to -0.45, p=0.015, d=0.666). No significant differences were observed in glenoid inclination, glenoid dimensions, depth, or height-to-width ratio. Younger age was significantly associated with re-dislocation (28.4 ± 5.3 vs. 25.1 ± 6.2; 95% CI, 0.11 to 6.53, p=0.042, d=0.553). CONCLUSION: In this retrospective cohort of patients without substantial osseous defects, increased glenoid retroversion was associated with a reduced risk of recurrence following first-time traumatic anterior shoulder dislocation managed nonoperatively. No significant associations were observed for other glenoid morphological parameters. LEVEL OF EVIDENCE: Level III, Retrospective cohort study.