Prevalence of Rotator Cuff Atrophy and Fatty Infiltration in Patients Undergoing Total Shoulder Arthroplasty

Background Rotator cuff fatty infiltration and atrophy are risk factors for worse outcomes after total shoulder arthroplasty (TSA). The purpose of this study is to evaluate the prevalence of preoperative fatty infiltration and atrophy in TSA patients compared to control patients without glenohumeral osteoarthritis. Methods We retrospectively identified 30 patients undergoing TSA for primary glenohumeral arthritis who had preoperative magnetic resonance imaging. TSA patients were matched by age and sex with control patients without arthritis or full-thickness rotator cuff tears. Blinded observers graded fatty infiltration of the 4 rotator cuff muscles and measured supraspinatus atrophy by the occupation ratio. A multivariate analysis was used to correlate arthritis, age, sex, and body mass index with rotator cuff atrophy and fatty infiltration. Results Goutallier grade ≥ 2 fatty infiltration was seen in at least one muscle for 13/30 (43%) TSA patients and 1/30 (3%) control patients ( P < .01). The average supraspinatus fossa occupation ratio was 0.72 ± 0.24 in the TSA group compared to 0.92 ± 0.23 for controls ( P < .01). Moderate to severe supraspinatus muscle atrophy (occupation ration < 0.6) was observed in 10/30 (33%) TSA patients and 0/30 (0%) controls. Glenohumeral arthritis was an independent predictor of atrophy and fatty infiltration ( P < .01). Age, sex, and body mass index were not significantly correlated with atrophy or fatty infiltration. Conclusion Glenohumeral arthritis is associated with rotator cuff atrophy and fatty infiltration. In the absence of rotator cuff tendon tearing, glenohumeral arthritis may contribute to the pathophysiology of rotator cuff muscle degeneration.