Early and subsequent radiographic changes during the occurrence of osteochondritis dissecans of the elbow.

Background: Little is known about the radiographic changes before and after osteochondritis dissecans (OCD) occurrence. The aim was to clarify the earliest and subsequent radiographic changes. Methods: Among 120 patients with capitellar OCD, we selected the patients who had consecutive radiographs of the elbow before and after OCD occurrence. We retrospectively clarified the earliest and subsequent changes. Results: Four (3%) boys met the criteria. All four had been in baseball team and had medial elbow pain with medial epicondylar apophysitis. They had no lateral elbow pain or abnormal findings of the capitellum. After the mean of 3.5 months from initial presentation, OCD silently occurred in the capitellum at the mean age of 11.4 years. The earliest detectable radiographic change was subtle rarefaction at the ossifying subchondral bone surface in the lateral aspect of the capitellum; however, it was too subtle and limited to be recognizable as OCD. These features gradually became more evident and expanded, eventually leading to flattening and depression of the subchondral bone surface, accompanied by subchondral bone cysts surrounded by sclerotic bone. The capitellar lesions were diagnosed as early OCD. Discussion: This is the first report to show the radiographic changes before and after OCD occurrence. The earliest change was subtle rarefaction. Repetitive forces on the preadolescent capitellum may cause stress injury at the secondary physis followed by rarefaction of the ossifying subchondral bone. Micromovements of the overlying cartilage would allow the side-by-side concurrence of subchondral bone cysts, resulting in subchondral depression, eventually leading to recognizable early OCD.