The Isolated Motor Branch of the Ulnar Nerve Injury During Open Carpal Tunnel Release.

A 76-year-old woman underwent open carpal tunnel release (OCTR). She had sudden sharp shooting pain in her hand, in the mid-palmar area, during the operation. She was then unable to abduct or adduct her thumb and fingers after surgery. She had no sensation impairment of the ulnar digit. The nerve conduction study confirmed a complete transection of the motor branch of the ulnar nerve (MUN). The MUN was repaired, and the patient recovered her intrinsic hand muscle function two years after the operation. The mechanism of injury, related anatomy and potentially dangerous area, clinical findings, management, and prevention are discussed.