Irreducible dislocation of the radial head with undisplaced olecranon fracture in a child: a case report.

Irreducible isolated dislocation of the radial head is a rare injury. In this study, we describe a patient with irreducible dislocation of the radial head associated with an undisplaced fracture of the olecranon. A 6-year-old girl fell down while walking and suffered injury to the posterior aspect of the proximal ulnar shaft with the right elbow in a slightly flexed position. Plain radiographs of the elbow revealed an anterior-medial dislocation of the radial head and an undisplaced fracture of the olecranon. However, the attempted closed reduction was not successful. An open reduction was then performed through a lateral approach. The radial head was found to be protruding through a buttonhole tear of the anterior joint capsule, causing the joint to become interposed between the articular surfaces of the joint, precluding closed reduction. Once the interposed capsule was extricated from the joint, the radial head could be easily reduced. At this point, no tear of the annular ligament was observed. Six months after the surgery, the patient was able to use her elbow fully and without pain. The range of motion was 0-140° for both extension and flexion and 90° for pronation and supination. Plain radiographs revealed a united bone of the olecranon and good reduction of the radial head. The radial head pushed through the tear of the anterior joint capsule. This buttonhole effect on the radial head prevented closed reduction of the radial head.