[Posterolateral rotatory instability of the elbow--a case report and anatomical study of the lateral collateral ligament].

A 20-year-old woman was referred to our clinic complaining of recurrent subluxation of her right elbow. A posterolateral rotatory instability test revealed that she had insufficiency of the lateral collateral ligament. She was surgically treated; the ligament was reconstructed by using the palmaris longus tendon. A year after operation, she had no pain in her elbow, and regained full range of elbow motion. The function of the lateral collateral ligament is often overlooked. We, therefore, dissected 24 elbow joints and studied anatomically in order to confirm the origin and insertion of the lateral collateral ligament. The ligament originates from the lateral epicondyle, and runs distally in fan shape. It further inserts partly to the annular ligament and partly to the supinator crest. After complete sectioning of the ligament, the forearm was fixed in supination, then flexed with valgus moment. This maneuver elicited subluxation of the radio-humeral joint, which was similar to what we observed in the clinical case. From these observations, we have concluded that the ligament is important for stability of elbow joint as well as the medial collateral ligament.