Trigger thumb in adults after hyperextension injury.

Three cases of trigger thumb in adults developing after hyperextension injury are described. The similarity of the mode of injury in the cases and its possible role in the production of initial stenosis in the tendon sheath is discussed. Trauma alone may not cause triggering in the fingers, for there are other important factors such as rheumatoid disease, which with trauma may play a part. Trauma may however be the sole initiating factor in other cases of adult trigger thumbs.