Bipolar Bone Loss in Male Athletes With Traumatic Anterior Shoulder Instability: An Evaluation Using a New Scoring System

BACKGROUND: The combination of a glenoid defect and a Hill-Sachs lesion in a shoulder with anterior instability has recently been termed “bipolar bone loss,” but the prevalence and influence of this condition on postoperative recurrence after arthroscopic Bankart repair are still unclear. PURPOSE: To investigate bipolar bone loss in male athletes using a new scoring system and to evaluate its efficacy by comparing it with the glenoid track concept. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The sizes of both lesions were evaluated retrospectively in 80 male athletes (85 shoulders) using computed tomography. The glenoid defects and the length, width, and depth of the Hill-Sachs lesions were classified into 5 size categories and were allocated scores from “0” for no defect to “4” for the largest defect. Patients were then classified into 5 classes according to the total score for both lesions: class 1, 0-1 point; class 2, 2 points; class 3, 3 points; class 4, 4 points; and class 5, ≥5 points. The prevalence of bipolar bone loss and postoperative recurrence rates for patients with at least 2 years of follow-up were compared among the classes. The recurrence rate for each class was also compared between shoulders with an off-track lesion and shoulders with an on-track lesion as well as among 3 sporting categories: rugby, American football, and other sports. RESULTS: Based on the combination of glenoid defect size and Hill-Sachs lesion length, the postoperative recurrence rate was 0% for shoulders in class 1, 12.5% for class 2, 33.3% for class 3, 28.6% for class 4, and 31.3% for class 5, while the recurrence rates were 0%, 16.7%, 28.6%, 27.3%, and 31.6%, respectively, for the combination of glenoid defect size and Hill-Sachs lesion width and 0%, 8.3%, 26.7%, 28.6%, and 35.3%, respectively, for the combination of glenoid defect size and Hill-Sachs lesion depth. Postoperative recurrence was frequently recognized regardless of the presence of off-track Hill-Sachs lesions. No recurrence was recognized in class 1 shoulders among rugby players, in classes 1 and 2 among American football players, and in classes 1 through 3 among other athletes based on the combination of glenoid defect size and Hill-Sachs lesion size. CONCLUSION: Our scoring system for bipolar bone loss was useful to evaluate the influence on postoperative recurrence in male athletes. The postoperative recurrence rate was influenced by the extent of bipolar bone loss and the sporting category regardless of the presence of off-track lesions.