Nerve Grafting for Isolated Injury to the Intrinsic Motor Branch of the Ulnar Nerve due to a Stab Injury: A Case Report

Isolated injury to the deep motor branch of the ulnar nerve caused by stabbing is sporadic, with only one reported case in the English-language literature. We report one such case treated successfully using nerve grafting. A 33-year-old patient had sustained a stab wound to the right hypothenar eminence and showed a claw hand deformity. Needle electromyography study revealed denervation potentials with no voluntary motor unit action potentials (MUAPs) in the first dorsal interosseous (FDI) muscles. Nerve exploration revealed a neuroma-in-continuity in the intrinsic motor branch of the ulnar nerve. Intraoperative nerve stimulation confirmed the absence of compound muscle action potentials in the FDI. The damaged scarred nerve was resected, and the 15-mm defects were reconstructed with cable autografting. Two years and 5 months after the surgery, voluntary MUAPs were observed in the FDI. The pinch strengths recovered. Laceration of the deep branch of the ulnar nerve caused by stabbing can sometimes remain hidden as the hand sensation remains intact. Pre- and intraoperative electrophysiological examination is essential to assess the severity of the injured nerve and determine an appropriate surgical option. Even nerve grafting can facilitate satisfactory results as target intrinsic muscles are quite close to the repair site.