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

Introduction Previous studies show that reverse shoulder arthroplasty (RSA) may improve forward elevation (FE) but external rotation (ER) 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) following RSA with a more lateralized center of rotation . Methods 69 patients (average age 69 years; 44 females, 25 males) with preoperative MRI, 1-year postoperative ROM, 2-year Veteran’s Rand Survey (VR12), American Shoulder and Elbow Surgeons subjective form (ASES), and Single Alpha-Numeric Evaluation (SANE) scores who underwent RSA with a lateralized glenoid component between 2010 and 2014 were identified. Patients with Fuchs stage 3 fatty degeneration were compared to 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, VR12 scores, age, and BMI were not different between groups. There were no differences after one year (follow-up=15±14months) in FE (FE=128 ±29) or ER (33±13) between groups. There were no differences in two-year minimum (follow-up=42.9±17.9 months) ASES 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.