MOMENT ARMS OF THE DIGITAL FLEXOR TENDONS AT THE WRIST - ROLE OF DIFFERENTIAL LOADING IN STABILITY OF CARPAL-TUNNEL TENDONS

When a flexor digitorum superficialis tendon crossing a flexed or exte nded wrist has a load applied to it in excess of that applied to adjac ent tendons, that tendon may translate across the carpal tunnel. In 6 cadaver specimens, each of the 9 carpal tunnel tendons was loaded with a baseline tension of 85 g and the moment arms of the flexor pollicis longus and the 4 flexor digitorum superficialis tendons were determin ed. Applying a higher 540-g load to individual flexor digitorum superf icialis tendons and the flexor pollicis longus while loading the remai ning tendons with the baseline 85-g tension significantly changed the moment arms from those measured under baseline load. The results demon strated that tendons with applied differential loads in the carpal tun nel shift their positions, as revealed by their changing moment arms. (J Hand Surg 1998;23A:998-1003. Copyright (C) 1998 by the American Soc iety for Surgery of the Hand.).