Effect of Glenoid Concavity Restoration on Surgical Failure after Arthroscopic Bony Bankart Repair

Background: This study aimed to evaluate the degree of glenoid concavity restoration and its effect on surgical failure after arthroscopic bony Bankart repair for recurrent anterior shoulder instability with a bony Bankart lesion. Methods: Forty-one patients who underwent arthroscopic bony Bankart repair for recurrent anterior shoulder instability with a bony Bankart lesion were retrospectively evaluated. All patients underwent 3-dimensional computed tomography (3D-CT) preoperatively to evaluate the glenoid concavity using the bony shoulder stability ratio (BSSR). Bony fragments were incorporated to the anterior glenoid during arthroscopic stabilization procedure. All patients were reevaluated by 3D-CT at postoperative 1 year to assess the changes in the BSSR and the final glenoid bone defect size after bony Bankart repair. Clinical outcomes including surgical failure were evaluated at least 2 years after surgery. Results: The BSSR significantly increased after surgery (26.0% ± 14.0% preoperatively and 35.5% ± 13.2% postoperatively, p < 0.001). Preoperative glenoid bone defect size was 16.2% ± 8.1%, and bony Bankart fragment size was 11.3% ± 7.2%. Four patients (9.8%) had recurrent instability requiring revision surgery. In patients with surgical failure, the BSSR was not improved after surgery (18.2% ± 13.3% preoperatively and 23.1% ± 17.3% postoperatively, p = 0.24). In contrast, patients without surgical failure showed significantly improved BSSR after surgery (26.9% ± 14.0% preoperatively and 36.9% ± 12.2% postoperatively, p < 0.001). No significant differences were found in the final glenoid bone defect size (6.6% ± 5.9% in patients with surgical failure vs. 6.2% ± 5.7% in patients without surgical failure, p = 0.92) and bony Bankart fragment nonunion rate (0% in patients with surgical failure vs. 5.4% in patients without surgical failure, p = 0.99) between patients with and without surgical failure. Conclusions: Glenoid concavity, as represented by the BSSR, improved after arthroscopic bony Bankart repair, and satisfactory restoration of the glenoid concavity led to successful clinical outcomes without surgical failure. The BSSR could be considered an important factor for predicting clinical outcomes after arthroscopic bony Bankart repair. However, further research including more contributing factors is needed to better analyze the impact of the BSSR on clinical outcomes.