Anatomical variations as potential risk factors for ulnar tunnel syndrome: A cadaveric study

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.

Ulnar Nerve Compression in the Proximal Forearm By An Intraneural Arteriovenous Malformation

“…The etiology of ulnar nerve compression at the proximal forearm includes compression, traction and repeated irritation, lipoma, vascular anomalies, bone fractures, ulnar artery disease, anomalous tendon and muscles, and trauma related to an occupation (3)(4)(5)(6)(7).…”

Ulnar Nerve Compression at Guyon's Canal by an Arteriovenous Malformation

“…Fibro-osseous space known as Guyon's canal at the wrist is rare site of ulnar nerve compression 3,8) . The etiology of ulnar nerve compression at the wrist includes ganglion, lipoma, vascular anomalies, carpal bone fractures, ulnar artery disease, anomalous tendon and muscles, and trauma related to an occupation [1][2][3][4][5]7) . Among them, ganglion is the most common cause 3,5,7,11) .…”

“…Subsequently, knowledge of distal ulnar nerve is important. At Guyon's canal, ulnar nerve divides into a superficial sensory branch and a deep motor branch 2,3) . Superficial sensory branch supplies to the skin of the hypothenar eminence and the surface of the fifth digit and medial region of the fourth digit.…”

“…Guyon's canal, a fibro-osseous space within the proximal part of the hypothenar eminence between pisiform and hook of the hamate, was first described by Felix Guyon in 1861 1,2,4) . It is covered proximally by the palmar carpal ligament and distally by the fibrous arch of the short palmar muscles 4) .…”

“…It is covered proximally by the palmar carpal ligament and distally by the fibrous arch of the short palmar muscles 4) . In Guyon's canal, ulnar nerve is vulnerable to external compression and patient's clinical presentation is different according to the lesion involvement site [1][2][3]4,11) . Numerous lesions have been reported in the literature as causes of ulnar nerve compression at Guyon's canal but vascular lesion is rarely described in the literature 4,5,7) .…”