Anatomic investigations of nerves at the wrist: I. Orientation of the motor fascicle of the median nerve in the carpal tunnel.

The orientation of the motor fascicle of the median nerve in the carpal tunnel was investigated in dissections of 50 hands. Topographically, the motor branch was located on the radial-volar aspect of the median nerve in 60% of the hands, the central-volar aspect in 22%, and between these two locations in the remaining 18%. In 56% of the hands, the motor branch passed through a separate distinct fascial tunnel before entering the thenar muscles. Awareness of these patterns will facilitate appropriate surgical management of thenar muscle weakness or wasting associated with the carpal tunnel syndrome.