A neural loop of the deep motor branch of the ulnar nerve: an anatomic study.

A motor neural loop of the deep branch of the ulnar nerve was encountered on three occasions during neurolysis of the ulnar nerve through Guyon's canal. An anatomic study of the course of the deep motor branch of the ulnar nerve at the wrist was done to define the incidence of this neural loop. Seventy-seven cadaveric upper extremities were examined and seven (9%) cases of a neural loop were encountered. One of these cases was bilateral. This variation should be considered when there is an atypical clinical presentation after penetrating injuries or compression neuropathy of the ulnar nerve at the wrist. In addition, care must be taken not to injure this branch during decompression of Guyon's canal or excision of an ununited of the hook of the hamate.