[Laxity in the metacarpophalangeal joint of the thumb]

Instability in the thumb is one of the most frequent sport injuries following trauma with the finger in abducted position. Investigation of the stability includes pinch-hold test and conventional X-ray examination to visualize bone avulsion fractures. Occasionally radiologic stress test of stability or arthrography should be performed in cases of doubt. Surgical intervention must be performed in all cases with instability or uncertain clinical manifestation. Especially the distal rupture with folding of the ulnar collateral ligament, the Stener lesion, should be detected to avoid healing of the ligament to the first metacarpal bone. Any form of surgical treatment must be immobilized in a cast for 4 to 6 weeks. The tendency is to perform direct suture of capsules and ligaments for the first posttraumatic weeks, tenoplasty operations before 2-3 months and fusion in cases with persistent, chronic instability.