The A3 pulley

The tendon-pulley geometry and gliding resistance with and without the A3 pulley were compared in 6 fresh human cadaver fingers. We measured the x- ray images of the distal A2 pulley-tendon angle and proximal A4 pulley-tendon angle with varying degrees of proximal interphalangeal joint flexion between 0° and 120°before and after A3 pulley resection. The gliding resistance of the flexor digitorum profundus tendon under the A2 pulley was also measured at varying tendon-pulley angles. With the A3 pulley removed, the tendon- pulley angle significantly increased compared with the A3 intact state. The gliding resistance between tendon and pulley quadratically increased as the tendon-pulley angle increase from 0°to 60°. These results indicate that the A3 pulley might serve to reduce tendon-pulley gliding resistance by reducing the tendon-pulley angle during finger flexion. (C) 2000 by the American Society for Surgery of the Hand.