Introduction:The sensory communication between the median and ulnar nerves in the palm contributes to digital sensation in a majority of patients. The communication is at risk in open and endoscopic carpal tunnel release. To better understand the anatomy of theis communication an anatomical study was performed.

Methods:Fifty cadaver hands were dissected.The palmar fascia was removed and the transverse carpal ligament was opened. Communicating branches between the median and ulnar sensory nerve were carefully dissected and photographed. The branch if present was photographed and its branch points were measured (longitudinal distance from the distal wrist crease). The fibers were then followed to judge the direction of the fibers.

Results:A communicating branch was noted in in 37 of 50 hands dissected (74%). In 34 (68%)specimens the connecting branch ran from the ulnar to the median nerve contributing to the common digital nerve to the 3rd and 4th fingers. In 3 specimens the nerve ran from the median to the ulnar nerve contributing to the common digital nerve to the 4th and 5th fingers. The mean distance of the ulnar anastamosis of the communicating branch from the distal palmar crease was 32 mm (range 17-45mm, S.D. 7.5.). The mean distance of the median anastamosis was 39 (range 30-55mm, S.D. 7.3). In 9 specimens(18%) the takeoff of the communicating branch was within 2.5 cm of the distal wrist crease.

Discussion: The communicating branch is seen in a majority of patients and contains sensory fibers. The communication falls within 2.5 cm of the distal wrist crease in a significant number of patients where it may be at risk during routine carpal tunnel release. A knowledge of the anatomy of this branch is important when doing carpal tunnel or Guyon.s canal releases in the palm