An anatomical study on the Stener-type lesion of the radial collateral ligament of the metacarpophalangeal joint of the thumb.

The Stener-type lesion of the radial collateral ligament is rare. The insertion of the abductor pollicis brevis is believed to preclude its occurrence. The aim of this study was to determine whether this lesion can be induced mechanically. Four specimens were tested in neutral rotation and 20° of supination, in 45° and 30° of flexion, and in the neutral position. The angle of ulnar adduction to form a Stener-type lesion was measured. The lesion occurred only in 45° flexion in all specimens. A lesser angle of flexion decreased the rate of ligament displacement. In the neutral position no ligament displacement was found. A Stener-type lesion of the radial collateral ligament can occur in ulnar adduction and flexion of the metacarpophalangeal joint. Supination of the joint increases the likelihood of ligament displacement. As distal ruptures of the radial collateral ligament are uncommon, a high index of suspicion is required for diagnosis.