Selective restoration of motor function in the ulnar nerve by transfer of the anterior interosseous nerve - An anatomical feasibility study

Background: Proximal ulnar-nerve lesions have an unfavorable prognosis. The goal of the present study was to evaluate the feasibility of selective res toration of motor function of the ulnar nerve by the transfer of the anteri or interosseous nerve or one of its branches to the motor branch of the uln ar nerve. Methods: Ten cadaveric arms were used in the present study. The ulnar nerve and its motor and sensory branches as well as the anterior interosseous ne rve and its branches were dissected. The widths of the motor branch of the ulnar nerve and the anterior interosseous nerve and its motor branches as w ell as the relevant distances from the points of divergence were measured. The axons were counted, and the distances from the end of the main anterior interosseous nerve, its motor branches, and the motor branch of the ulnar nerve to the level of the dorsal sensory branch of the ulnar nerve were mea sured. Results: Our results indicate that the length, width, and number of axons o f the branch of the anterior interosseous nerve to the pronator quadratus m ake it suitable for transfer to the motor branch of the ulnar nerve. The us e of the main anterior interosseous nerve or its motor branches to the flex or pollicis longus and the flexor digitorum profundus is less feasible beca use of the need to graft a long segment and the longer distance from the le vel of transfer to the motor end points. Conclusions: The findings of the present study confirm the feasibility of m otor-nerve transfer for reconstruction after an injury of the ulnar nerve. Nerve-grafting would be needed for injuries distal to the level of the dors al sensory branch of the ulnar nerve.