Extensor mechanism laxity at the metacarpophalangeal joint as identified by a new provocative test: predisposition to dislocation.

A tendon subluxation test was performed on the unaffected side in 13 patients with traumatic extensor tendon dislocation of the middle finger and on both middle fingers in 800 healthy controls to identify extensor mechanism laxity at the metacarpophalangeal joint. Ten of the 13 patients with dislocation had laxity of middle finger extensor tendon, compared with 174 of the 800 (22%) controls. The difference in these rates of extensor tendon laxity is significant (P<0.0001), and suggests that extensor mechanism laxity at the metacarpophalangeal joint may predispose to traumatic extensor tendon dislocation.