Influence of Glenoid Labral Bumper Height and Capsular Volume on Clinical Outcomes After Arthroscopic Bankart Repair as Assessed With Serial CT Arthrogram: Can Anterior-Inferior Volume Fraction Be a Prognostic Factor?

Background: Arthroscopic labral repair combined with capsular plication decreases joint volume and restores glenoid labral bumper height; thus, the procedure helps decrease capsular redundancy. However, the decreased volume and restored glenoid labral bumper height could change over time, which could influence the outcome of the operation. Purpose: To (1) measure glenoid labral bumper height and capsular volume quantitatively in serial computed tomography arthrography (CTA) and evaluate the relationship between bumper height and joint volume and (2) compare the difference in bumper height and joint volume between groups with and without apprehension after arthroscopic Bankart repair. Study Design: Case-control study; Level of evidence, 3. Methods: Patients who had undergone arthroscopic Bankart repair between January 2012 and June 2016, and were assessed by CTA 3 to 6 months and 12 to 18 months after the operation were included. An image reconstruction program (3-dimensional slicer) was used to calculate inferior, anterior-inferior, and posterior-inferior joint volumes; the ratio of the anterior-inferior volume to the inferior volume was defined as the anterior-inferior volume fraction (VFAI). We also measured glenoid labral bumper height at the 5-, 4-, and 3-o'clock positions. Results: A total of 50 patients were enrolled as study participants (mean age, 25.2 +/- 9.29 years). Of these, 10 patients had either redislocation or apprehension, and 40 patients had neither. A significant correlation was observed between 5-o'clock glenoid labral bumper height and VF(AI)on early CTA (3-6 months) and late CTA (12-18 months) (early CTA: Pearson coefficient, -0.335,P= .040; late CTA: Pearson coefficient, -0.468,P= .003). VF(AI)at the early CTA was 42.20 +/- 10.15 in the group with apprehension and 33.49 +/- 9.66 in the group without apprehension; a significant difference was observed. VF(AI)at the late CTA was 45.84 +/- 11.97 in the group with apprehension and 37.65 +/- 9.70 in the group without apprehension and thus showed a significant difference between the 2 groups. However, the 3-, 4-, and 5-o'clock glenoid labral bumper heights on early and late CTAs did not show a statistically significant difference between the 2 groups. Conclusion: Early postoperative VF(AI)is related to postoperative apprehension and redislocation and might be reduced by increasing the 5-o'clock glenoid labral bumper height.