Infraspinatus or teres minor fatty infiltration does not influence patient outcomes after reverse shoulder arthroplasty with a lateralized glenoid

BACKGROUND: Previous studies show that reverse shoulder arthroplasty (RSA) may improve forward elevation (FE) but external rotation may remain impaired with substantial teres minor fatty infiltration. The purpose of this study was to examine the influence of fatty infiltration on postoperative range of motion (ROM) and patient-reported outcomes (PROs) after RSA with a more lateralized center of rotation. METHODS: About 69 patients (average age 69 years; 44 women, 25 men) with preoperative MRI, 1-year postoperative ROM, 2-year Veteran’s Rand Survey, American Shoulder and Elbow Surgeons subjective form, and Single Alpha-Numeric Evaluation scores who underwent RSA with a lateralized glenoid component between 2010 and 2014 were identified. Patients with Fuchs stage 3 fatty degeneration were compared with patients with Fuchs stage ≤ 2 using a one-way ANOVA. RESULTS: Eleven patients had Fuchs stage 3 in the teres minor and 28 with stage 3 in the infraspinatus. Charlson comorbidity indices, Veteran’s Rand Survey scores, age, and BMI were not different between groups. There were no differences after one year (follow-up = 15 ± 14 months) in FE (FE = 128 ± 29) or external rotation (33 ± 13) between groups. There were no differences in two-year minimum (follow-up = 42.9 ± 17.9 months) American Shoulder and Elbow Surgeons scores between degenerated teres minor (76.4 ± 20) or infraspinatus (69.1 ± 24) groups. CONCLUSION: This is the first study to assess the influence of teres minor and infraspinatus fatty infiltration on the postoperative ROM and PROs with a more lateralized glenoid RSA implant. Our results show that in a more lateralized RSA, neither teres minor nor infraspinatus fatty infiltration appear to negatively influence ROM or PROs.