RESTORATION OF FUNCTION OF THE THUMB FLEXOR APPARATUS REQUIRES REPAIROF THE OBLIQUE AND ONE ADJACENT FLEXOR TENDON PULLEY

Damage to the pulleys of the thumb flexor apparatus may cause bow-stri nging of the tendon and affect muscle function, An experiment using th e hands and distal forearms of cadavers was designed to determine whic h damaged pulleys increase excursion length of the flexor tendon with constant tendon and resisting loads. Each specimen was mounted to a lo ading frame with a dead weight pinned to the tip of the thumb. The thu mb flexor tendon was clamped to an actuator that applied a fixed load and measured excursion of the tendon. Ranges of motion of the thumb jo int were also measured. The thumb flexor apparatus of each specimen wa s tested intact first, with the hand in flexed, neutral, and extended positions; then it was tested with progressive sectioning of pulleys f rom proximal to distal in one group and from distal to proximal in a s econd group. The length of excursion increased significantly with all pulleys cut but there was no effect on overall range of motion of the thumb. With proximal to distal sectioning, no change in tendon excursi on occurred when the flexor retinaculum and the first annular pulleys were cut, until the oblique pulley was sectioned, leaving only the sec ond annular pulley intact (range, 1.17-1.31 times that of intact excur sion, dependent on position of the hand), With distal to proximal sect ioning, tendon excursion was not affected when the second annular and oblique pulleys were cut but did increase when the first annular pulle y was sectioned, leaving only the flexor retinaculum intact (range, 1. 28-1.36 times that of intact excursion). Dependent on the location of damage, therefore, an intact oblique or first annular pulley can maint ain normal excursion of the tendon.