Reconstructing Pinch Strength after Ulnar Nerve Injury by Transferring the Opponens Pollicis Motor Branch

Abstract

Background: With ulnar nerve injuries, paralysis of the first dorsal interosseous(FDI) and adductor pollicis muscle weakens the patient’s pinch. In the palm, we transferred the opponens pollicis motor branch (Opp) to the deep terminal division of the ulnar nerve (DTDUN) for pinch reconstruction. Methods: Sixteen patients with ulnar nerve injuries around the elbow underwent reconstruction and were followed post-operatively for a minimum of 14 months. Their mean age was 41 years (SD ± 15), and the mean interval between injury and surgery was 134 days (SD ±126, range: 2-390). Pre- and postoperatively grasp, key and subterminal key-pinch strength were measured using dynamometers. Results: Reinnervation of the FDI was observed in 15 of the 16 patients. Mean grasp strength improved from 15.5kg (SD ± 8.5kg) pre-operatively to 24kg (SD ± 10kg) postoperatively, achieving 57% (SD ± 16%) contralateral hand strength. Preoperatively, terminal key pinch averaged 3kg (±1kg), which improved postoperatively to 5.5kg (SD ± 2kg), achieving 71% (±24%) the strength measured contralaterally. Pre- to post-operatively, subterminal key-pinch force increased from zero to 2.4kg (SD ± 1.3kg) achieving 61% (SD ± 27%) that of the unaffected side. Patients who underwent surgery within six months of their injury showed a mean subterminal key pinch strength recovery of 63% (SD ± 27) of the normal side, while those who underwent surgery between seven and 13 months after injury showed a mean subterminal key pinch strength recovery of 51% (SD ± 29). Conclusions: Transferring the Opp to the DTDUN improved pinch and grasp strength without jeopardizing thumb function.