Intrinsic muscle advancement to treat chronic palmar instability of the metacarpophalangeal joint of the thumb.

Chronic palmar instability of the metacarpophalangeal joint of the thumb can result in a significant disability. Grasp, particularly pinch, is painful and weak because the thumb goes into hyperextension. Stabilization of the metacarpophalangeal joint can be achieved by distal advancement of the conjoined tendon of the abductor pollicis brevis and lateral fibers of the flexor pollicis brevis.