Reverse End-to-Side Abductor Digiti Minimi-to-Recurrent Motor Branch Nerve Transfer for Severe Carpal Tunnel...

Severe carpal tunnel syndrome (CTS) with advanced thenar denervation has limited reconstructive options, and reliable reinnervation remains challenging. Reverse end-to-side (RETS) nerve transfers have been described in other contexts but to our knowledge, have not been applied clinically to compressive median neuropathy at the wrist. Here, we present three patients, ages 59, 68, and 72 years, with severe CTS, visible thenar atrophy, and electrodiagnostic evidence of profound median motor axon loss who underwent carpal tunnel release with abductor digiti minimi (ADM)-to-recurrent motor branch (RMB) RETS transfer. All procedures were performed using a standardized microsurgical technique. Follow-up was 10 months (Case 1), 24 months (Case 2), and 8 months (Case 3). Postoperatively, each patient demonstrated early return of visible thenar contraction between 6 weeks and 4 months, with final abductor pollicis brevis (APB) strength of 4 to 4+. Sensory recovery improved across all cases, with two-point discrimination normalizing to 5-8 mm. Follow-up electrodiagnostic studies in two patients showed markedly greater APB compound muscle action potential (CMAP) amplitudes when stimulating through the ulnar nerve than through the median nerve, consistent with donor-derived reinnervation through the transfer. Patient-reported outcome measurement information system (PROMIS) upper extremity (UE) and physical function (PF) scores improved by 9-22 points. Although these early results suggest the potential for donor-derived reinnervation in severe CTS, the findings are preliminary and should be interpreted with caution. Larger prospective studies will be necessary to determine the true functional benefit, appropriate patient selection criteria, and comparative effectiveness of this technique.