Secondary pectoralis major transfer for subscapularis insufficiency after reverse total shoulder arthroplasty: a six-case series stratified by instability versus internal rotation weakness.

BACKGROUND: Subscapularis (SSC) insufficiency after reverse total shoulder arthroplasty (rTSA) may result in recurrent anterior dislocation or persistent internal rotation (IR) weakness, both of which impair function. Secondary pectoralis major (PM) transfer has been proposed as a salvage option, but supporting clinical evidence is limited. METHODS: We retrospectively analyzed six consecutive patients who developed SSC retear following rTSA with concomitant SSC repair between 2020 and 2023. Indications for revision were recurrent anterior dislocation (n = 3) or disabling IR weakness affecting activities of daily living (n = 3). All patients underwent secondary PM transfer; polyethylene insert upsizing was performed selectively in dislocation cases. Clinical outcomes were assessed using the American Shoulder and Elbow Surgeons (ASES), Constant, and Activities of Daily Living involving Internal Rotation (ADLIR) scores, visual analog scale (VAS) for pain, range of motion (ROM), and handheld dynamometer strength. Radiographic evaluation included implant integrity and recurrence of dislocation. RESULTS: At a median follow-up of 30 months (24–36), all patients demonstrated clinical improvement. VAS decreased from 4 (3–6) to 1 (1–2), while ASES, Constant, and ADLIR scores improved. Forward elevation (FE) and IR improved, along with marked gains in FE and IR strength. No recurrent dislocations occurred in the dislocation subgroup, and all patients in the IR-weakness subgroup regained belly-press or lift-off performance. CONCLUSION: Secondary PM transfer represents a reliable revision option for SSC insufficiency after rTSA, effectively restoring anterior stability in dislocation cases and enhancing IR function in patients with weakness. This technique should be considered a valuable salvage option in this difficult clinical context.