Transverse divergent dislocation of the elbow.

A girl 6 years 5 months old sustained a rare transverse (mediolateral) divergent dislocation of the elbow and was treated by closed reduction. The arm was immobilized in a cast. Followup was 7 years 5 months. Five years after injury, the patient had recurrent popping on the lateral aspect of the injured elbow during active flexion from complete extension and tenderness on the anterior aspect of the radiohumeral joint. To determine the exact anatomic relation of the proximal radius and ulna to each other and to the distal humerus after transverse dislocation, a skeleton of the elbow was assembled in the dislocated position, and multiple radiographs and photographs were taken and compared with the radiographs of the patient's injured elbow. This showed that the ulna was displaced posteromedially, with the coronoid process impinged against the distal and medial portions of the trochlea, and that the radial head was displaced lateral to the capitellum, anterior and distal to the lateral epicondyle. The distal end of the humerus was caught by the radius and the ulna and was rotated anteriorly and laterally, primarily by the displaced coronoid process. Because of this rotation of the humerus, the lateral radiograph of the elbow gave the impression that the head of the radius was displaced posteriorly.