Teres Minor Hypertrophy is a Common and Negative Predictor of Outcomes after Rotator Cuff Repair

Abstract

Introduction: The teres minor has received increased attention in its role as a rotator cuff muscle, particularly in the setting of large infraspinatus tears. Studies have shown that it plays an important role after total (TSA) and reverse (RSA) shoulder arthroplasty, as well as in maintenance of function in the setting of infraspinatus wasting. In this regard, teres minor hypertrophy has been described as a compensatory change in response to this infraspinatus wasting, and has been suggested that this compensatory hypertrophy may mitigate the loss of infraspinatus function in the patient with a large rotator cuff tear. No study, however, has investigated whether teres minor hypertrophy is a positive or negative predictor on outcomes after rotator cuff repair. The purpose of this study was to determine the prevalence of teres minor hypertrophy in a cohort of patients undergoing rotator cuff repair, and to determine its prognostic effect, if any, on outcomes after surgical intervention. Methods: Over a 3 year period, all rotator cuff repairs performed in a single practice by 3 ASES member surgeons were collected. Inclusion criteria included both preoperative and postoperative validated outcomes measures (minimum 2 year), and preoperative Magnetic Resonance Imaging (MRI) scanning. 144 patients met all criteria. All MRIs were evaluated for rotator cuff tear tendon involvement, tear size, and Goutallier changes of each muscle. In addition, occupational ratios were determined for the supraspinatus, infraspinatus, and teres minor muscles. Patients were divided into 2 groups, based upon whether they had teres minor hypertrophy or not, based on a previously established definition. A 2 way ANOVA was used to determine the effect of teres minor hypertrophy and Goutallier changes on American Shoulder and Elbow Society (ASES) change scores(alpha = 0.05). Results: Teres minor hypertrophy was a relatively common finding in this cohort of rotator cuff patients, with 51% of all shoulders demonstrating hypertrophy. Interestingly, in patients without an infraspinatus tear, teres minor hypertrophy was still present in 19/40 (48%) of patients. Teres minor hypertrophy had a significant, negative effect ASES scores after rotator cuff repair in patients with and without infraspinatus tearing, infraspinatus atrophy, and fatty infiltrative changes(P < .05). In general, the presence of teres minor hypertrophy (Figure Presented) showed 10-15% less improvement (Fig. 1) than when no hypertrophy was present, and this was consistent across all tear sizes, independent of Goutallier changes. Conclusions: Teres minor hypertrophy is a common finding in the setting of rotator cuff tearing, including in the absence of infraspinatus tearing. Contrary to previous publications, the presence of teres minor hypertrophy does not appear to be a compensatory response to infraspinatus tearing nor is it a positive predictor of outcome, at least in the setting of rotator cuff repair.