Magnetic resonance imaging of the collateral ligaments of the thumb.

Injury to the ulnar collateral ligament of the metacarpal phalangeal joint of the thumb can usually be diagnosed on the basis of a combination of history, radiographic examination, and clinical stress testing of the joint when appropriate. Occasionally, when the patient is seen late and the diagnosis is doubtful, stress evaluation may be ill-advised because a nondisplaced ligament may be displaced in the process. We had recent experience with three patients in whom the use of magnetic resonance imaging was helpful in diagnosing a displaced ulnar collateral ligament in two cases, and an intraligamentous injury in the other. These studies were conducted at no charge to the patient as part of institutional investigational research. The current cost of this technology is prohibitive for routine use; however, when it becomes less expensive, it may be helpful as a diagnostic tool.