Ulnar nerve cutaneous distribution in the palm: Application to surgery of the hand

The ulnar nerve (UN) was classically described as supplying most of the intrinsic muscles of the hand, and the cutaneous innervation of the ulnar one and half digits, by dividing into superficial sensory and deep motor branches in Guyon's canal. Variations of this pattern have been reported in the literature. This study investigated the cutaneous distribution of the UN in the palm following the dissection of 144 cadaveric hands. The UN was examined and the distances from branching points of the superficial branch to the proximal edge of the pisiform were measured. The UN bifurcated (80.4%) into one deep trunk and one superficial trunk, which further divided distally into the proper digital (PDN) and common digital (CDN) nerves or trifurcated (19.6%) into one deep trunk, a PDN and a CDN in Guyon's canal. It received fibers from the median nerve in four cases and from the dorsal branch of the UN in six cases. A classification scheme based on the nerves contributing to the sensory innervation of the ulnar side of the palm was suggested. Understanding the cutaneous distribution of the UN in the palm and appreciating possible communicating branches can help clinicians to assess hand pathologies better and avoid injuries during surgical interventions.