[Hyperextension instability of the thumb metacarpophalangeal joint treated by sesamoid arthrodesis].

Summary. Inadequate treatment of hyperextension trauma of the metacarpophalangeal joint of the thumb can cause chronic instability with pain and weakness of pinch. Between January 1995 and December 1998, nine patients (seven posttraumatic and two associated with CMC joint arthrosis) were treated with an arthrodesis of the radial sesamoid. The bones were fused in seven cases by intraosseous sutures and in two cases with small screws. Kirschner wire temporary fixation of the MP joint and cast immobilization for six weeks was our standard procedure. The follow-up time ranged from six to forty-seven months (average 26 months). One patient had screw loosening after a second injury. Another one had pain because of posttraumatic arthrosis in the MP joint. The remaining seven patients reported a significant improvement in their condition, they were satisfied and free of pain. Palmar stability was restored. A little flexion restriction in the MP joint was found. An arthrodesis of the radial sesamoid of the MP joint of the thumb is a simple technique to treat palmar instabilities. This operation should not be performed if additional collateral ligament injury or arthrosis exist.