Critical Value of Anterior Glenoid Bone Loss That Leads to Recurrent Glenohumeral Instability After Arthroscopic Bankart Repair

Background: Generally, a glenoid bone loss greater than 20% to 25% is considered critical for poor surgical outcomes after a soft tissue repair. However, recent studies have suggested that the critical value should be lower. Purpose: To determine the critical value of anterior glenoid bone loss that led to surgical failure in patients with anterior shoulder instability. Study Design: Case-control study; Level of evidence, 3. Methods: The study included 169 patients with anterior glenoid erosion. The percentage of glenoid erosion was calculated as the ratio of the glenoid loss width and the glenoid width to the diameter of the outer-fitting circle based on the inferior portion of the glenoid contour. The critical value of the glenoid bone loss was analyzed by means of receiver operating characteristic (ROC) curve analysis. Patients were divided into 2 groups based on the amount of glenoid bone loss: group A (less than the critical value) and group B (more than the critical value). Patients evaluated their shoulder function as a percentage of their preinjury level using the Single Assessment Numeric Evaluation (SANE) score, and postoperative clinical outcomes were assessed with the American Shoulder and Elbow Surgeons (ASES) score and Rowe score. Surgical failure was defined as the need for revision surgery or the presence of subjective symptoms of instability. Results: The optimal critical value of glenoid bone loss was 17.3% (area under the curve = 0.82; 95% confidence interval, 0.73-0.91; P < .001; sensitivity 75%; specificity 86.6%). Group A and B contained 134 and 35 patients, respectively. Shoulder functional scores were significantly lower in group B than in group A (P < .001). Five patients (3.7%) in group A and 15 (42.9%) in group B had surgical failure (P < .001). The SANE score was significantly lower in group B (83.8 +/- 12.1) than in group A (92.9 +/- 4.7, P = .001). Conclusion: An anterior glenoid bone loss of 17.3% or more with respect to the longest anteroposterior glenoid width should be considered as the critical amount of bone loss that may result in recurrent glenohumeral instability after arthroscopic Bankart repair.