The oblique pulley is the central and most important pulley of the thumb flexor sheath, running obliquely across the proximal phalanx of the thumb from the ulnar base to the radial mid-shaft. It is the only true annular pulley of the thumb (A2 equivalent) and is the critical structure preventing bowstringing of the flexor pollicis longus during IP joint flexion. The thumb pulley system has three pulleys: A1 at the MCP, the oblique pulley at the proximal phalanx, and A2 at the IP joint level.
Prevents FPL bowstringing during IP joint flexion, maintaining close apposition of the tendon to the phalanx throughout the range of motion, essential for efficient thumb pinch and grip strength.
The thumb oblique pulley is the critical pulley to preserve during thumb flexor tendon repair and reconstruction. Unlike the finger flexor system where A2 and A4 are critical, in the thumb the oblique pulley is the key pulley and must be preserved or reconstructed during zone 2 thumb flexor tendon surgery. Pulley reconstruction with a tendon graft looped around the proximal phalanx restores thumb FPL mechanics when the oblique pulley is destroyed by laceration or infection.
Zone 2 thumb FPL lacerations in the fibro-osseous sheath may damage the oblique pulley; reconstructing both the FPL tendon and the oblique pulley using a tendon graft around the proximal phalanx restores mechanical efficiency and prevents FPL bowstringing during rehabilitation.
