Electrodiagnostic and Clinical Outcomes after Supercharged Anterior Interosseous Nerve Transfer in Advanced Cubital Tunnel Syndrome.

Abstract

Background: In patients with advanced cubital tunnel syndrome (CuTS), conventional surgical outcomes are often suboptimal due to the long distance required for nerve regeneration. The supercharged end-to-side anterior interosseous nerve to ulnar motor nerve transfer (referred to as SETS transfer) has been proposed to enhance reinnervation and accelerate recovery. This study aimed to evaluate the electrodiagnostic and clinical outcomes of SETS transfer in patients with advanced CuTS and to determine the time course of functional recovery.

Methods: This prospective study included 11 patients with severe, non-traumatic CuTS (modified McGowan grade IIB or III) who underwent ulnar nerve decompression, subcutaneous anterior transposition, and SETS transfer. Electrodiagnostic studies were performed preoperatively and at 3, 6, and 12 months postoperatively, assessing compound muscle action potentials (CMAPs) of the abductor digiti minimi (ADM) and first dorsal interosseous muscles, sensory nerve action potentials (SNAPs) of the ulnar and dorsal ulnar cutaneous (DUC) nerves, and detection of nascent motor unit action potentials (MUAPs). Grip and key-pinch strength and Disabilities of the Arm, Shoulder, and Hand (DASH) scores were assessed preoperatively and at 12 months.

Results: The CMAP amplitude of the ADM significantly improved at the 12-month follow-up compared to the preoperative assessment (p = 0.004). Postoperative nascent MUAPs were observed in 8 patients, all of which appeared within 6 months. In contrast, among patients with no preoperative SNAP who had a postoperative response, most recorded their first SNAP at 12 months after surgery (5 of 6 for ulnar SNAP and 5 of 7 for DUC SNAP). Key-pinch strength and DASH scores improved significantly (p = 0.014 and p = 0.003, respectively), while grip strength showed no significant change (p = 0.142).

Conclusions: SETS transfer may promote early reinnervation and improve intrinsic muscle function in patients with severe CuTS. Serial electrodiagnostic studies suggest that SETS transfer may contribute to motor recovery within the first 6 months postoperatively.