Surgical anatomy of the dorsal cutaneous branch of the ulnar nerve and its clinical significance in surgery at the ulnar side of the wrist.

The dorsal cutaneous branch of the ulnar nerve can be easily injured during surgery at the ulnar side of the wrist. We sought to identify the surgical anatomy, the pathway around the ulnar styloid process and the safe zone of the dorsal cutaneous branch of the ulnar nerve. In 44 forearm dissections, we found that the dorsal cutaneous branch of the ulnar nerve originated at a median distance of 6.8 cm proximal to the tip of the ulnar styloid. We classified the crossing pattern of the dorsal cutaneous branch of the ulnar nerve at a vertical axis into three types. The most common type featured the dorsal cutaneous branch of the ulnar nerve crossing the vertical axis at a median distance of 10.0 mm distal to the tip of the ulnar styloid. In 14% of specimens, the dorsal cutaneous branch of the ulnar nerve crossed the vertical axis at the level of the tip of the ulnar styloid. By mapping the course of the nerve using a Cartesian coordinate system, it was found that the areas located proximal and palmar to the tip of the ulnar styloid had a very high density of dorsal cutaneous branches of the ulnar nerve. We were unable to establish a safe zone. We recommend identifying the dorsal cutaneous branch of the ulnar nerve in every patient undergoing surgery at the ulnar side of the wrist.