Background: Anterosuperior labral variations of the glenohumeral joint have been previously described and are thought to represent normal anatomical variants without any known clinical importance. The goals of this study were to characterize anterosuperior labral anatomical variations and to determine their prevalence and clinical importance.
Methods: A total of 546 patients who had an arthroscopic procedure in the shoulder were prospectively evaluated for variations of the anterosuperior aspect of the labrum. Structural characteristics of the anatomical variants were noted and recorded intraoperatively. The relationships of these anterosuperior labral variations to demographic data, preoperative symptoms, findings on physical examination, and associated intra-articular abnormalities were analyzed statistically and compared with findings in patients with normal anterosuperior labral anatomy.
Results: Three distinct variations of the anterosuperior portion of the labrum were found in seventy-three patients (13.4%): a sublabral foramen only (eighteen patients; 3.3%), a sublabral foramen with a cord-like middle glenohumeral ligament (forty-seven; 8.6%), and an absence of labral tissue at the anterosuperior portion of the labrum with a cord-like middle glenohumeral ligament (eight; 1.5%). In multivariate analysis, the presence of one of these three variations revealed a significant positive association with anterosuperior labral fraying (p = 0.000), an abnormal superior glenohumeral ligament (p = 0.012), and increased passive internal rotation with the arm in 90° of abduction (p = 0.046). These lesions were negatively associated with a painful arc sign and the presence of either a partial or full-thickness supraspinatus tendon tear. Statistical analysis revealed a clinical difference between the cord-like middle glenohumeral ligament variants and the sublabral foramen variant.
Conclusions: Anterosuperior labral variants may influence glenohumeral biomechanics and may predispose the shoulder to other abnormalities. These variants are associated with increased internal rotation, which may predispose the shoulder to lesions of the superior glenohumeral ligament and anterosuperior portion of the labrum. These variations themselves do not appear to contribute to instability.
Level of Evidence: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.