Latissimus Dorsi and Teres major tendon transfer increases internal rotation torque following lateralized reverse shoulder arthroplasty with subscapularis insufficiency

Introduction Limitation of active Internal Rotation (IR) following Reverse Shoulder Arthroplasty (RSA) in patients with massive Rotator Cuff Tears (mRCTs) with subscapularis insufficiency remains a challenge. Recently, RSA with Latissimus dorsi and Teres major (LDTM) transfer in patients with limited active IR has been demonstrated as a reliable treatment option. The purpose of this study was to biomechanically compare the IR torque following LDTM transfer with RSA in mRCT with subscapularis insufficiency to RSA without tendon transfer. Methods Eight cadaveric shoulders were tested (mean age: 64.5 ± 1.9 years) using a custom shoulder testing system that permits loading conditions of mRCT with subscapularis insufficiency. Two conditions were tested and compared. The first condition was RSA alone and the second condition was RSA with LDTM transfer. RSA with a medialized glenoid and lateralized humerus design was used for all specimens. The specimens were tested at 0°, 20° and 40° abduction at three different muscle loads: baseline, double, and triple, while the Teres minor and deltoid loads were kept constant. IR torque was measured with a torque wrench at 0°, 20°, and 40° abduction and 60° and 45° IR positions. Force required for anterior dislocation was measured at 20° abduction and 10° IR position. Results RSA with LDTM transfer had significantly higher IR torque at all abductions and muscle loading compared with RSA without transfer (average at all positions; RSA without transfer: 0.80 ± 0.02 Nm, LDTM transfer for all loads: 1.43 ± 0.10 Nm). RSA with LDTM transfer (91.4 ± 3.9 N) needed higher force for anterior dislocation compared to RSA alone (89.4 ± 4.1 N), but there was no significant difference. Conclusion LDTM transfer with RSA increases IR torque compared to RSA without tendon transfer in a cadaveric model. LDTM transfer with RSA may be a reliable treatment option for patients with mRCT and subscapularis insufficiency who are expected to have limited active IR following RSA.