Anatomy of the palmar branch of the ulnar nerve: application to ulnar and median nerve decompressive surgery

Abstract

The palmar cutaneous branch of the ulnar nerve (PCUN) has received little attention in the literature, and to the authors' knowledge, has received no attention in the neurosurgical literature. The present study was performed to help the surgeon minimize postoperative complications of nerve decompression at the wrist. Forty cadaveric upper limbs underwent dissection of the ulnar nerve in the forearm, at the wrist, and in the palm. The PCUN was investigated and when identified, measurements were made and relationships documented between this cutaneous branch and the ulnar artery. The length and width of the PCUN were measured, as was the distance from the medial epicondyle of the humerus to the origin of the PCUN from the ulnar nerve. A PCUN was found on 90% of sides. The origin of the PCUN from the ulnar nerve was found to lay a mean of 14.3 cm distal to the medial epicondyle. The mean length and width of this branch were 13 and 0.08 cm, respectively. In the forearm, the PCUN traveled lateral to the ulnar artery on 75% of sides and on the medial side of this vessel on the remaining sides. The PCUN perforated the fascia of the anterior forearm just proximal to the distal wrist crease. In the palm, the PCUN traveled superficial to the superficial palmar arch on all but 5 sides, where it traveled deep to this vascular structure's distal extent. On 2 sides each, the PCUN communicated with the superficial and deep ulnar nerves. On 2 sides, the PCUN communicated with the palmar cutaneous branch of the median nerve. The majority of the terminal fibers of the PCUN were found on the ulnar side of a hypothetical line drawn longitudinally through the fourth digit and supplied an area roughly 3 × 3 cm over the proximal medial palm. The authors hope that the present data may be useful to the surgeon during decompressive procedures at the wrist, such as carpal tunnel and the Guyon canal. Based on this study, skin incisions of the palm made longitudinally along a line through the middle of the fourth digit would minimize injury to the PCUN.