Subscapularis Repair in Reverse Shoulder Arthroplasty: Does Implant Design Matter?

Reverse total shoulder arthroplasty (rTSA) continues to expand in indications, and modern implant designs have reshaped the biomechanical role of the subscapularis. However, whether subscapularis repair is necessary after rTSA remains controversial, in part, because its contribution to stability and motion is not uniform across implant geometries. This narrative review synthesizes contemporary biomechanical and clinical evidence to define how glenoid and humeral design features including center of rotation, degree of lateralization, neck–shaft angle, and humeral onlay/inlay configuration, modify subscapularis function, repair demands, and postoperative outcomes. Across the literature, medialized constructs demonstrate greater dependence on the subscapularis for anterior stability and internal rotation. In these configurations, successful repair may enhance stability and internal rotation, whereas failed healing can magnify functional deficits and compromise outcomes. In contrast, lateralized designs at the glenoid, humerus, or both improve deltoid wrapping and soft tissue tensioning, increase intrinsic constraint, and expand impingement-free range of motion, thereby reducing the functional necessity of subscapularis repair and maintaining low instability rates even when the tendon is not repaired. Dual lateralization may provide the most robust stability and external rotation, but it can increase anterior soft tissue tension, making selective repair and careful intraoperative tension assessment critical. Overall, implant geometry, not repair status alone, most strongly determines the clinical relevance of the subscapularis after rTSA. These findings support a shift from routine repair toward a design-specific, patient-tailored strategy that integrates implant configuration, tendon quality, soft tissue balance, and functional goals to optimize stability, motion, and long-term success.