Effect of Muscle Quality on Operative and Nonoperative Treatment of Rotator Cuff Tears

BACKGROUND: Rotator cuff muscle atrophy and fatty infiltration are predictors of negative outcomes after rotator cuff repair. However, the impact of muscle degeneration on nonsurgical treatment is unknown. HYPOTHESIS: Rotator cuff muscle atrophy and fatty infiltration will reduce the outcomes of operative repair while having a minimal effect on nonsurgical treatment. Additionally, in the setting of atrophy and fatty infiltration, surgical and nonsurgical treatment will produce equivalent outcomes. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: Patients undergoing operative and nonoperative treatment of full-thickness rotator cuff tears were prospectively enrolled into a nonrandomized cohort study. Muscle quality was assessed on magnetic resonance imaging by use of the supraspinatus tangent sign, Warner atrophy, and Goutallier fatty infiltration classifications. Grading was performed by 2 independent observers who were blinded to patient treatment and outcomes. Normalized Western Ontario Rotator Cuff (WORC) index was the primary patient-reported outcome. Multivariate linear regression analysis was used to determine the impact of muscle quality on treatment outcomes. RESULTS: The cohort consisted of 157 patients, 89 (57%) surgical and 68 (43%) nonsurgical, with a mean follow-up of 2.4 years (range, 1-5 years). Tangent sign had the best inter- and intrarater reliability, with kappa statistics of 0.81 and 0.86, respectively. Reliability for Warner atrophy was 0.69 to 0.76 and for Goutallier classification was 0.54 to 0.64. Overall, improvement in WORC scores was higher in the surgical group than the nonsurgical group (39.3 vs 21.2; P < .001). A positive tangent sign was the only independent predictor (P < .01) of worse outcomes in the surgical group, accounting for an estimated 22-point lower improvement in WORC scores. CONCLUSION: A positive tangent sign was predictive of worse operative outcomes, resulting in equivalent improvements between surgical and nonsurgical treatment. The tangent sign is a reliable, prognostic indicator that clinicians can use when counseling patients on the optimal treatment of rotator cuff tears.