Pulleys of the tendon sheath of the flexor pollicis longus muscle

Abstract

The fibrous wall of the flexor tendon sheath of the thumb is reinforced by pulleys similar to those in the fingers. As cited in the literature, there are two annular pulleys A 1 and A 2 and one oblique pulley. On the basis of our investigations, this distribution was found only in 10%. In 90%, the proximal (A 1) and the distal pulley (A 2) can be seen. However, between these two annular pulleys a Y-shaped fiber complex can be dissected at the level of the base and the shaft of the proximal phalanx. This complex can be further divided into an annular part (proximal) and an oblique part (distal). The annular part is associated with the tendon insertion of the adductor pollicis muscle. The oblique part arises distal from the annular part from the ulnar side of the tendon sheath, running to the radial side of the proximal phalanx interwoven with the interphalangeal joint capsule and the palmar plate. Some fiber strands continually pass into the cutaneous ligaments of Cleland. Thin accessory pulley fibers were found between the annular pulley A 1 and the annular part of the Y-shaped fiber complex in 9.5% and in 20.6% between the oblique part and the annular pulley A 2.