Summary

This study presents a novel method of measuring labral size that may help predict failure of shoulder stabilization surgery.

Abstract

Introduction

Anatomic variations in capsule and labrum morphology may predispose patients to recurrent shoulder instability after surgery but specific risk factors are unknown. The aim of this study was to identify demographic risk factors and develop

Method

to measure capsule and labral volume on MRI to predict surgical failure after primary Bankart repair. We hypothesized that the number of dislocations prior to surgery, smaller labral volume, and larger capsular volume are risk factors for failure of stabilization surgery.

Methods

A retrospective case-control study was conducted on 289 patients undergoing primary aterior arthroscopic shoulder stabilization. Surgical failure was defined as a recurrent dislocation event. Cases were compared 1:2 to matched controls. Pre-operative arthrograms were analyzed by two trained reviewers employing the Vitrea software measuring labrum and capsular volume within a three-dimensional model, with data analyzed via Fisher exact and student t testing. Labral size was also qualitatively measured on axial images in the posterior-inferior quadrant. A “small” labrum was defined as less than the width of the anterior band of the inferior glenohumeral ligament.

Results

Of 109 identified patients, 36 (12%) patients experienced a redislocation event at average follow-up of 30.3 months. There was no difference between groups with regard to age (p = 0.99), sex (p = 1.00), contact sports (p = 0.79), overhead athletics (p = 0.19), or throwers (p = 0.34), and number of repair anchors used (p = 0.95). The average number of preoperative dislocations was significantly higher in the failure group (3.13 vs. 1.91, p < 0.05). Odds ratios for failure were 2.4 after 2+ dislocations, 2.9 after 4+, and 8.1 after 6+ dislocations . The percentage of patients with a diffusely small labral morphology was significantly higher in the failure group (40.5% vs. 16.9%, p = 0.01).

Conclusion

An increased number of recurrent dislocations prior to primary Bankart repair increased the risk of recurrent instability after surgery. The odds ratio for failure also increased with increasing number of prior dislocations. The presence of small labrum morphology is also a significant risk factor for recurrent instability. This study presents a novel method of measuring labral and capsule volume.