Anatomy of flexor pollicis longus vinculum system.

The vinculum breve of the flexor pollicis longus is a strong structure able to supply bony attachment and transmit some flexion force even after a laceration of the tendon at the interphalangeal joint. About 90% of the thumbs studied had a vinculum breve. After laceration of the flexor pollicis longus at the level of the interphalangeal joint, an intact vinculum attached to the proximal end of the tendon can transmit flexion to the joint. An opposed resistance flexion test will differentiate an intact flexor pollicis longus from a lacerated tendon held only by the vinculum. A maximum excursion of 24.5 +/- 8 mm of a lacerated flexor pollicis longus tendon is possible while the vinculum breve remains intact.