The impact of subscapularis integrity on functional outcome in reverse total shoulder arthroplasty utilizing a 135˚ stem

Background: Reverse shoulder arthroplasty (RSA) predictably restores overhead function and provides pain relief in patients with glenohumeral arthritis and rotator cuff deficiency. Implant design with an anatomic inclination angle of 135˚ may provide an advantage in the healing rates of subscapularis tendon (SST) repairs. The purpose of this study was to use ultrasound to evaluate the subscapularis repair healing rate, and secondarily, to compare outcomes between healed and non-healed SSTs, in patients undergoing RSA with a 135˚ inclination angle. Methods: A prospectively collected, multicenter shoulder arthroplasty registry was queried to identify patients undergoing RSA with a 135˚ inclination stem with a minimum of 1 year follow-up. Ultrasound analysis was performed at final follow-up to assess subscapularis integrity. Exclusion criteria included RSA for fracture, fracture sequelae or failed prior arthroplasty. Outcome measures included American Shoulder and Elbow Surgeons score (ASES), Western Ontario Osteoarthritis of the Shoulder (WOOS), Single Anatomic Numeric Evaluation (SANE), and Constant scores. Additionally, subscapularis functional assessments included range of motion, belly-press and shirt-tuck tests. Statistical analysis was performed using ANOVA, Chi-square, and student t-tests with SPSS. Results were considered significant at P <.05. Results: Seventy-eight patients meeting the inclusion criteria were identified from the registry, however, only seventy-five patients had ultrasound and healing data. The subscapularis was repaired in 60 patients and healing via ultrasound was noted in 56.7% (34/60). In most cases, a subscapularis peel was performed, with lesser tuberosity osteotomy performed in 9.38% of cases. Patients whose subscapularis was repaired were found to be older (72.2 vs. 64.9, P <.001) and the majority of patients with an unrepaired subscapularis were male (13/15, 86.7% unrepaired vs. 27/60, 45.0% repaired). Both healed and non-healed patient cohorts showed statistical improvement in all pain and functional outcome scores from their baselines. However, there were no significant differences in outcome scores between healed and non-healed SST. With regards to SST repair, only overall WOOS (Δ+15.62, P =.049) and physical component of the WOOS score (Δ+15.97, P =.040) were higher in patients with nonrepaired SST. There was no correlation between the ability to perform a belly-press or shirt-tuck test and subscapularis repair or evidence of radiographic healing. Patients who did not have their subscapularis repaired demonstrated greater passive external rotation at the side from 31° to 51° (P =.044). A significant increase in passive forward flexion was noted in patients with healed subscapularis from 117° to 135° (P =.042). There was no statistical difference in active range of motion between either the repaired/nonrepaired or healed/non-healed cohorts. Conclusion: Our study demonstrates a healing rate of 57% following repair in patients undergoing RSA with a 135˚ angle. Standardized outcome measures overall demonstrated no difference between patients with a healed subscapularis compared to those with a non-healed or unrepaired subscapularis. Level of Evidence: IV, case series, treatment study.