Chronic elbow instability without fractures in adults can be broken down into three types: (1) valgus instability, (2) posterolateral rotator instability, and (3) isolated radial head instability. By far the most common is valgus instability, which usually occurs in throwing athletes as a result of repetitive microtrauma to the anterior band of the medial collateral ligament. Surgical treatment is aimed at reconstruction of the anterior band of the medial collateral ligament. Posterolateral rotatory instability is much less common and is diagnosed by the lateral pivot-shift test of the elbow. It is usually the result of an undiagnosed acute injury to the lateral ulnar collateral ligament. Surgical treatment is aimed at its reconstruction. Isolated radial head subluxation in adults is extremely rare. The essential lesion is a disruption of the annular ligament. Surgical treatment is either radial head resection or reconstruction of the annular ligament.
