No abstract

The aim of this study was to assess the anatomical variations, especially the anomalous muscles passing through Guyon's canal and the fibrous arch forming the piso-hamate hiatus, which may play a role in ulnar tunnel syndrome. We have also focused on the relation of these structures with specific concern to the ulnar nerve. Nineteen embalmed cadavers (37 hands and forearms) were dissected. A fibrous arch extending between the pisiform and the hook of the hamate was observed in 21 hands. In majority of the cases flexor digiti minimi muscle was found to originate only from this arch. An anomalous muscle was disclosed in six hands with four of them passing through the piso-hamate hiatus with the deep branch of the ulnar nerve. In two of four cases, the superficial branch of the ulnar nerve was also accompanying the deep branch of the ulnar nerve beneath the anomalous muscle and through the piso-hamate hiatus. Because these anomalous muscles were generally found to course through the piso-hamate hiatus with the branches of the ulnar nerve, we conclude that the distal portion of the Guyon's canal has a relatively higher risk for ulnar nerve entrapment. We believe that surgeons operating on this region should take into account these various anatomic structures.

The superficial palmar communicating branch between the ulnar and median nerves, the ramus communicans (RC), has been investigated by anatomical dissections in 30 hands of 15 cadavers in the Turkish population. A communicating branch between the ulnar and median nerves was found in 18 hands (60%). It was classified into 4 types: Type 1-RC emerging from the ulnar 4th common digital nerve (CDN) and uniting with the median 3rd CDN, Type 2-RC emerging from the median 3rd CDN and uniting with the ulnar 4th CDN, Type 3-RC extending horizontally between the 3rd and 4th CDN, Type 4-a plexiform RC formed by multiple twigs. Twelve hands (40%) showed the Type 1 arrangement, one was Type 2 (3.3%), two were Type 3 (6.7%) and three (10%) were Type 4, based on the classification devised by Meals and Shaner ([1983] J Hand Surg Am 8:411-414) and modified by Bas and Kleinert ([1999] J Hand Surg Am 24:1171-1184). Knowledge of the anatomical characteristics of this branch is important for surgical interventions, especially in carpal tunnel release operations.

During dissection of the right forearm of a 27-year-old female cadaver, variations in the form and insertion of the palmaris longus muscle were observed. The tendon of the palmaris longus muscle, which demonstrated a centrally placed belly, split into two tendons: one inserted into the palmar aponeurosis and the other into the proximal part of the flexor retinaculum. Additionally, we found an accessory muscle extending between the flexor retinaculum and the tendon of the abductor digiti minimi muscle. This accessory muscle was located deep to the ulnar artery but superficial to the superficial and deep branches of the ulnar nerve at the wrist. Finally, an aberrant branch of the ulnar nerve was identified in the forearm; it traveled distally alongside the ulnar artery and in the palm demonstrated communications with common palmar digital nerves from the ulnar and the median nerves. No variations were observed in the contralateral upper limb.

Rectus capitis posterior muscles are located in the suboccipital triangle and function in extension and lateral rotation of the head and neck. There are two of these muscles on each side: the rectus capitis posterior major and the rectus capitis posterior minor. This study describes the presence of a third suboccipital muscle in a 55-year-old cadaver. In addition to highlighting the possible relationship between these muscles and cervicogenic headaches or balance in an individual, we also relate this observation to similar musculature in the cat that have been shown to effect crucial functions.