The median nerve consistently drives flexion of the distal phalanx of the ring and little fingers: Interest in finger flexion reconstruction by nerve transfers.

Abstract

Surgeons believe that in high ulnar nerve lesion distal interphalangeal joint (DIP) flexion of the ring and little finger is abolished. In this article, we present the results of a study on innervation of the flexor digitorum profundus of the ring and little fingers in five patients with high ulnar nerve injury and in 19 patients with a brachial plexus, posterior cord, or radial nerve injury. Patients with ulnar nerve lesion were assessed clinically and during surgery for ulnar nerve repair we confirmed complete lesion of the ulnar nerve in all cases. In the remaining 19 patients, during surgery, either the median nerve (MN) or the anterior interosseous nerve (AIN) was stimulated electrically and DIP flexion of the ring and little fingers evaluated. All patients with high ulnar nerve lesions had active DIP flexion of the ring and little fingers. Strength scored M4 in the ring and M3-M4 in the little finger. Electrical stimulation of either the MN or AIN produced DIP flexion of the ring and little fingers. Contrary to common knowledge, we identified preserved flexion of the distal phalanx of the ring and little fingers in high ulnar nerve lesions. On the basis of these observations, nerve transfers to the AIN may provide flexion of all fingers.