Musculoskeletal ImagingOsteochondritis
inflammation involving both bone and
cartilage.
Osteochondritis dissecans
results from fragmentation and sometimes the separation of a portion of the joint surface. Although genetic factors or growth disturbances may possibly cause some cases of osteochondritis dissecans, in most patients the initiating event is an osteochondral
fracture resulting from a shearing, rotational or tangential impaction force. The femoral condyles, especially the medial condyle, are the most common site of involvement, although the patella, talar dome, capitulum of the elbow, and various other sites may also be affected. The involvement of nonweightbearing surfaces is noteworthy. Although routine radiography is generally adequate in the detection of osteochondral lesions (
Fig.1), purely chondral lesions require
arthrography,
CT arthrography, MR imaging or arthroscopy for accurate diagnosis. Fluoroscopy is especially valuable in evaluating osteochondral fractures of the talar dome. Radiographically osteochondritis dissecans of the femoral condyle may be difficult to distinguish from
Ahlbacks disease (spontaneous
osteonecrosis of the knee), and osteochondritic disease of the patella may be difficult to differentiate from
chondromalacia patellae, dorsal defect of the patella, and osteochondral fractures resulting from direct injury or recurrent dislocation. Osteochondritis dissecans of the elbow is differentiated from
Panners disease in that the former occurs in adolescents and adults after ossification of the capitulum has been completed whereas Panner's disease occurs in preadolescent children, almost always boys.
Syphilitic osteochondritis
is a very early manifestation of
congenital syphilis; the sites of endochondral
ossification are affected in multiple locations. Broad horizontal metaphyseal bands with celery stalk appearance may be evident radiographically. In addition, erosions on the medial surface of the tibial shaft at its proximal end, termed
Wimbergers sign, may be present.
DR/RB