Risk Factors for Treatment Failure following Traumatic Anterior Shoulder Instability

Anterior shoulder instability, characterized by recurrent dislocations, subluxations, or a subjective sense of instability, can markedly affect daily life, sports participation, and work activities. Accounting for approximately 97% of all shoulder dislocations, it has an incidence of 23.9 per 100,000 person-years. Because treatment outcomes vary widely, selecting the most appropriate approach requires identifying patient-specific risk factors associated with poor outcomes. This thesis aims to optimize the management of anterior shoulder instability by comparing treatment strategies and identifying predictive risk factors to better guide clinical decision-making. Chapter I introduces shoulder instability, covering anatomy, associated injuries, treatment options, known risk factors, outcome measures, and patient selection considerations. Chapter II provides a historical overview of shoulder dislocation management, from ancient reduction techniques to modern surgical practices. Chapter III presents a systematic review and meta-analysis comparing recurrence after operative versus non-operative treatment in first-time dislocators, and between first-time and recurrent dislocators after surgery. Operative treatment after a first-time dislocation showed a markedly lower recurrence (10% vs 55%) than non-operative care. Recurrence was also lower in first-time compared to recurrent dislocations (11% vs 17%), although evidence for the latter was low due to retrospective data. Chapter IV retrospectively compares patient-reported outcomes (WOSI, OSIS) following primary open Latarjet versus arthroscopic Bankart repair (ABR) in subcritical (10–20%) glenoid bone loss. Scores were not significantly different overall, though the sports/work domain favored Latarjet. Recurrence was higher after ABR, while revision was higher after Latarjet. Limitations included small sample size, uneven distribution between hospitals, and shorter follow-up for Latarjet. Chapter V systematically reviews reasons why patients do not return to sport after Latarjet or ABR. Among 3545 patients from 63 studies, 70% did not return for reasons unrelated to shoulder function—such as fear of reinjury or lifestyle change—emphasizing the need to distinguish between physical and psychological limitations. Heterogeneity and vague definitions limited comparability across studies. Chapter VI analyzes 29 studies (4578 patients) to identify risk factors for recurrence after ABR. Significant predictors included younger age (≤30 years), competitive sports, Hill-Sachs and off-track lesions, glenoid bone loss, ALPSA lesion, >1 preoperative dislocation, surgical delay >6 months, and higher ISIS scores. Male sex, dominant arm, hyperlaxity, or sport type were not significant. Heterogeneity and retrospective design limited conclusions, but the study provides a comprehensive overview to support clinical counseling. Chapter VII develops a machine learning model using pooled data (5591 patients, 14 studies) to predict recurrence after ABR. Only 797 patients met uniform variable criteria, resulting in modest predictive accuracy (AUC 0.54–0.57). The study highlights the need for standardized definitions, consistent variable reporting, and global collaboration to enable robust predictive modeling. Chapter VIII explores prognostic factors for return to (pre-injury) sport after Latarjet. Return rates were high (RTS 97%, RTPS 81%). Lower education predicted no RTS, while a bony Bankart favored successful RTPS, underscoring the importance of socioeconomic and structural factors. Chapter IX assesses return to active duty in military personnel after ABR and Latarjet. After an average 63-month follow-up, 76% (ABR) and 85% (Latarjet) returned to duty. Although no predictors for failure were found, work limitations significantly decreased, especially for tasks above shoulder height. Chapter X discusses the implications of early surgical intervention, variability in study design, and inconsistent outcome definitions that impede data comparability. It advocates for prospective, standardized data collection, improved outcome reporting, and international data sharing to enhance prediction models and clinical decision-making.