The surgical anatomy of ulnar and median nerve communications in the palmar surface of the hand.

OBJECT: Sensation in the palmar surface of the digits is supplied by the median and ulnar nerves, with the boundary classically being the midline of the ring finger. Overlap and variations of this division exist, and a communicating branch between the ulnar and median nerve could potentially explain further variations in digital sensory innervations. The aim of this study was to examine the origin and distribution of the communicating branch between the ulnar and median nerves and to apply such findings to the risk involved in surgical procedures in the hand.
METHODS: The authors grossly and endoscopically examined 200 formalin-fixed adult human hands obtained in 100 cadavers, and a communicating branch was found to be present in 170 hands (85%). Of the specimens with communicating branches, the authors were able to identify four notable types representing different points of connections of the branches. The most common, Type I (143 hands, 84.1%), featured a communicating branch that originated proximally from the ulnar nerve and proceeded distally to join the median nerve. Type II (12 hands, 7.1%) designated a communicating branch that originated proximally from the median nerve and proceeded distally to join the ulnar nerve. Type III (six hands, 3.5%) designated a communicating branch that traversed perpendicularly between the median and ulnar nerves in such a way that it was not possible to determine which nerve served as the point of origin. Type IV (nine hands, 5.3%) designated a mixed type in which multiple communicating branches existed, arising from both ulnar and median nerves.
CONCLUSIONS: According to the origin and distribution of these branching patterns, the investigators were able to define a risk area in which the communicating branch(es) may be subject to iatrogenic injury during common hand procedures.