Anatomy of the flexor tendon sheath and pulleys of the thumb.

Studies of the pulley systems of the flexor tendon of the thumb demonstrate one oblique and two annular pulleys. Significant decrease in angular motion of the distal joint resulted when both the proximal annular pulley and the oblique pulley were removed, but isolated loss of either did not affect the motion appreciably. If the oblique pulley was intact, then loss of the distal annular pulley did not result in significant loss of motion.