Anatomical variations of Guyon's canal contents: a case report and incidence in South Australian population

Abstract

Ulnar nerve compression has been reported in association with variations in the contents of Guyon’s canal, such as the presence of accessory muscles. In the current case study we report on two variations found concurrently in the same hand. Firstly, the presence of an accessory head of the abductor digiti minimi that originated principally from the tendon of palmaris longus in the lower third of the forearm, descended superficial to the ulnar nerve and artery in Guyon’s canal, and joined three other heads of the same muscle in the hypothenar eminence. Secondly, the ulnar nerve within the canal showed trifurcation into superficial, deep and muscular branches. A study of 120 hands from cadavers of South Australian population revealed the presence of an accessory head of the abductor digiti minimi that occupied Guyon’s canal in 2.5% of the cases, a much lower incidence than previously reported in other populations. Trifurcation of the ulnar nerve seen here was also noted in the left hand of the same cadaver, but without any accessory muscles in Guyon’s canal. Knowledge of such variations is relevant to hand surgery.