The utilization of reverse total shoulder arthroplasty (RTSA) has continued to increase as its clinical indications expand. The optimization of the rotator cuff function in the setting of RTSA is poorly understood and poor outcomes are associated with lack of external and internal rotation function. The purpose of this study is to evaluate the role of implant parameters on rotator cuff tendon excursion and moment arms in the setting of RTSA.
Using a cadaveric based model, a custom designed modular RTSA system was implanted that allowed for incremental changes to glenoid and humeral lateralization. Using a shoulder simulator and optical tracking, rotator cuff tendon excursion and moment arms were calculated at various arm positions and implant configurations.
Increased glenoid and humeral lateralization yielded overall increased tendon excursion. Despite lack of statistical significance, there was a trend towards increased rotator cuff moment arms as glenoid and humeral lateralization increased.