gms | German Medical Science

Objectives/Interrogation: Osteochondritis dissecans (OCD) of the elbow is a localized injury of the articular cartilage and subchondral bone that is commonly seen in the young athlete. Mechanical factors seem to play an important role. The etiology of OCD lesions remains unclear. The aim was to address the course of pathologic progression.

Methods: The subjects were twelve elbows in 12 patients (average age, 13 years) with osteochondritis dissecans of the humeral capitellum. During osteochondral autograft, cylinder osteochondral plugs were taken from the center of the osteochondritis dissecans lesion and examined with light microscopy.

Results and Conclusions: The specimens were grossly divided into 3 parts: Articular fragment, intermittent part and basal bone. The intermittent part including a partial cleft consisted of fibrocartilage and connected the articular fragment with the basal bone. In the basal bone, there were no findings of osteonecrosis and active bone formation was found. The superficial area of the articular fragment consisted of articular cartilage and the deep area consisted of three components: (1) calcified cartilage, (2) viable bone, and (3) necrotic bone. The deep area of articular fragment consisted of calcified cartilage without bone in eight patients (average age, 12.8 years), although it had viable subchondral bone in two (average age, 12.5 years) and necrotic bone in two (average age, 15 years).

Discussion: Fibrocartilage in the intermittent part seemed to be reparative tissue to connect the articular fragment to basal bone. Basal bone was normal, suggesting that primary separation occurred just beneath the articular fragment. The radiographic images OCD showed delayed calcification and bone formation in the affected subchondral bone. These delayed ossification was observed in the articular fragment: cartilage calcification in eight, viable bone in two and necrotic bone in two. These findings suggest the following course of pathologic progression of OCD: (1) primary separation occurs horizontally under the deep cartilage and is followed by fibrocartilaginous repair, (2) Calcification occurs horizontally in the deep cartilage to be replaced by bone, however repetitive microtrauma causes bone replacement difficult, (3) Subchondral bone is formed by enchondral ossification, (4) Osteonecrosis occurr due to additional injury.