Nerve transfer of the median flexor pollicis brevis branch to the deep branch of the ulnar nerve for ulnar nerve palsy: a cadaveric feasibility study

Abstract

An ulnar nerve (UN) palsy is devastating for hand function, resulting in an intrinsic minus position or claw hand with a loss of pinch grip. Distal nerve transfers facilitate faster reinnervation of hand intrinsic muscles in cases of proximal ulnar nerve lesions. The traditional anterior interosseous nerve (AIN) to UN motor transfer is commonly used, however, this still leads to long reinnervation times for the distal intrinsic muscles, important for the thumb to index pinch grip. This study investigated the feasibility of a more distal nerve transfer, from the median thenar to the deep branch of the UN (DBUN), in six cadaveric hands. A separate branch of the median nerve to the superficial head of flexor pollicis brevis (sFPB) arose distally of the thenar branch from the common digital nerve of the thumb shortly before the bifurcation of the ulnar palmar digital nerve to the thumb in all specimens, with a mean distance to the thenar branch of 8.3 ± 5.3 mm. The sFPB motor branch had a mean length of 11.5 ± 1.5 mm. The mean distance between the division of the dorsal cutaneous branch of the UN, where the AIN to UN motor transfer is usually performed, and the transfer between the sFPB branch to the DBUN was 132 ± 11 mm. A distal nerve transfer between the median innervated motor branch to the sFPB to the DBUN shortens the reinnervation distance for the first dorsal interosseous, the adductor pollicis, and the deep head of the FPB muscles, which is a prerequisite for restoration of the pinch grip.