Effect of Teres Minor Fatty Infiltration on Rotator Cuff Repair Outcomes

Purpose To observe changes in fatty infiltration (FI) of the teres minor without tear of the teres minor in a postoperative magnetic resonance imaging and to evaluate the influence of FI of the teres minor in the clinical outcomes of rotator cuff repair. Methods Of 816 patients who underwent rotator cuff repair, 51 (6.3%) had FI of the teres minor without tear involvement and 30 cases were available for postoperative magnetic resonance imaging. FI and functional outcome scores were assessed and compared with the control group that had no FI of the teres minor selected by a propensity score matching. Results FI of the teres minor was observed in various degrees (grade 1 in 9, grade 2 in 9, grade 3 in 6, and grade 4 in 6). The degree of FI was not related to the amount of tendon involvement of a rotator cuff tear ( P = .240). All postoperative functional outcome scores (12.6 ± 1.2 months; range, 11-17), including pain visual analog scale, Simple Shoulder Test, and American Shoulder and Elbow Surgeons Score, significantly improved (all P < .001), and there were no significant differences compared with that of the control group. In most of the cases, FI of the teres minor was unchanged ( P = .317). Conclusions FI of the teres minor without tear involvement can be observed in a rotator cuff tear as a possibly incidental finding of unknown clinical significance. Its cause has not been determined, and it appears that FI of the teres minor does not appear to improve, at least at the 1-year follow-up. Nevertheless, the functional outcomes of the repair were successful in our study; therefore, rotator cuff repair can be performed without a great deal of concern in the presence of FI in the teres minor. Level of Evidence Level III, retrospective comparative study.