Anatomical Study on the Branching Pattern of the Ulnar Nerve in the Wrist and Palm

Abstract

BACKGROUND Ulnar nerve is one of the main nerves in the upper limb. The distal course of the ulnar nerve in particular has many clinical implications. The deep branch of ulnar nerve supplies most of the intrinsic muscles of hand which are concerned with the fine intricate movements of the hand. Due to this reason, the ulnar nerve is also called the "musician's nerve". Ulnar nerve has a relatively superficial course in the lower part of forearm and wrist which makes it easily prone to injuries. It is also very frequently injured in surgical corrections in the carpal tunnel. A better understanding of the distal course of the nerve will help in preventing and effective correction of such injuries. Therefore, an anatomical study on the branching pattern of the ulnar nerve in the wrist and palm will be of great use to the orthopaedic and vascular surgeons. The aim of this study is to find out the terminal branching pattern of ulnar nerve in the wrist and its extent of supply in the hand. METHODS The study was carried out in the Department of Anatomy, Government Medical College, Kottayam by the dissection of 40 upper limb specimens following the routine dissection method. The specimens were obtained after ethical clearance and were embalmed prior to the study. The distal part of ulnar nerve was dissected, its terminal branching pattern and extent of supply in the hand were noted and photographed. RESULTS In 29 specimens (72.5%), the termination of ulnar nerve showed a bifurcation pattern where the main trunk divided into a superficial sensory branch and deep motor branch whereas in 11 specimens (27.5%), the nerve was seen terminating in a trifurcation pattern. In 35 specimens (87.5%), the level of termination of ulnar nerve trunk was within the Guyon's canal. In 5 specimens (12.5%), the nerve terminated at higher level before entering the Guyon's canal. In 28/40 specimens superficial terminal branch divided into medial proper and common digital branches. In 12/40 specimens, the nerve divided into proper, common digital branches and a communicating nerve to digital branch of median nerve. In 37 specimens (92.5%), the deep branch of ulnar nerve supplied the medial two lumbricals. In 1 specimen (2.5%), second, third and fourth lumbricals were supplied by the deep branch of ulnar nerve which is an uncommon finding. In 2 specimens (5%), all the four lumbricals were supplied solely by the deep branch of ulnar nerve which is rarely seen. In the present study, 32 specimens (80%) were seen to be supplied by the deep branch of ulnar nerve. In 8 specimens, the muscle was not supplied by the ulnar nerve. CONCLUSIONS The site, extent of injury, variations and the delay in treatment significantly influences the outcome of ulnar nerve repair. Thus, an adequate knowledge of all possible variations of the ulnar nerve may be important for clinicians and may help to explain uncommon symptoms.