Reverse End-to-Side Triceps to Axillary Nerve Transfer for Treatment of Axillary Nerve Palsy After Reverse Total Shoulder Arthroplasty.

Nerve injuries are uncommon, yet significant complications following reverse total shoulder arthroplasty (rTSA), with the axillary nerve being most frequently injured. We report a case of a 67-year-old female who developed persistent motor dysfunction and decreased sensation in the axillary distribution following rTSA for a comminuted proximal humerus fracture. Electrodiagnostic studies confirmed right axillary nerve injury with reduced motor unit recruitment. After no improvement in deltoid function at three months following rTSA, we discussed treatment options for the patient, who opted for surgical intervention. Based on intraoperative findings, we performed a reverse end-to-side triceps-to-axillary nerve transfer. Postoperative evaluations over a four-year follow-up revealed substantial improvements in range of motion, strength, and patient-reported outcomes. Ultrasound and magnetic resonance imaging studies obtained at four years post-op demonstrated mild deltoid atrophy and fatty infiltration, despite the excellent clinical result. The triceps-to-axillary nerve transfer has potential as a viable intervention for non-recovering axillary nerve injuries after rTSA.