The A3 pulley

The tendon-pulley geometry and gliding resistance with and without the A3 p ulley 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 betwee n 0 degrees and 120 degrees before and after A3 pulley resection. The glidi ng resistance of the flexor digitorum profundus tendon under the A2 pulley was also measured at varying tendon-pulley angles. With the A3 pulley remov ed, the tendon-pulley angle significantly increased compared with the A3 in tact state. The gliding resistance between tendon and pulley quadratically increased as the tendon-pulley angle increase from 0 degrees to 60 degrees. These results indicate that the A3 pulley might serve to reduce tendon-pul ley gliding resistance by reducing the tendon-pulley angle during finger fl exion. (J Hand Surg 2000;25A:270-276. Copyright (C) 2000 by the American So ciety for Surgery of the Hand.).