Anatomic investigation of the role of the lumbrical muscles in carpal tunnel syndrome.

This study investigates whether the proximal origins of the lumbrical muscles contribute significantly to the etiology of carpal tunnel syndrome. We explored the carpal canals of 128 hands in patients undergoing carpal tunnel release for carpal tunnel syndrome. The origins of the lumbrical muscles were examined at the time of surgery and their relation to the transverse carpal ligament was recorded in all cases. Also, 40 cadaveric hands were dissected to determine the lumbrical muscle origins. In the hands of patients with idiopathic carpal tunnel syndrome, the lumbrical muscle origins were located significantly more proximal in the canal than were the muscles in the cadaveric hands. Younger patients whose jobs required repetitive hand motions had large lumbrical muscles and origins that were more proximal than the lumbricals found in the hands of fresh cadavers.