Imaging Studies
Anteroposterior (with elbow at 45° of flexion) magnetic resonance imaging (MRI)/lateral radiography
Plain radiography should be the primary imaging study obtained in all cases of humeral capitellum osteochondritis dissecans. Initially, radiographs appear without abnormalities. Early in the course of progression of humeral capitellum osteochondritis dissecans, changes are confined to the humeral capitellum. Changes may include patchy rarefaction consisting of a sclerotic rim of subchondral bone adjacent to the articular surface, irregular ossification, and/or a bony defect adjacent to the articular surface. Lateral radiographs may show flattening of the capitellum.
With the further passage of time, the radiographic appearance is based on whether separation of osteochondral fragments occurs. Without separation, the central sclerotic fragment becomes less distinctive, the rarefaction area ossifies, and the lesion slowly heals. However, with separation, loose bodies may be visualized within the joint. Note that only 30% of loose bodies are usually observed on plain radiography.
In the late stages of humeral capitellum osteochondritis dissecans, one is likely to see radial head enlargement, premature distal humeral physeal arrest, and degenerative changes leading to incongruity between the articulation of the radial head and the humeral capitellum.
Computed tomography (CT) scanning
CT scanning helps to determine changes in bony anatomy. Specifically, an island of subchondral bone demarcated by a rarefied zone should be observed.
MRI
MRI, specifically T1-weighted images showing low-signal changes at the surface of the capitellum, can be useful for early detection of humeral capitellum osteochondritis dissecans. MRI also assists in determining the size and extent of the lesion and the vascular supply to the area. On T2-weighted images, unstable lesions (those with loose fragments) are noted to have pockets of high signal (fluid) surrounding the displaced fragments.
Contrast arthrography
Contrast arthrography provides additional information about the size and extent of the lesion. It can help in assessing loose fragments and in assessing any other articular abnormalities.
Ultrasonography
Ultrasonography shows localized capitellar bony flattening, which is useful in early detection. [21] Nondisplaced fragments appear as double high–echogenic areas in the capitellar subchondral bone. Displaced free bone is detected as highly echogenic fragments overlying intact subchondral bone.
Procedures
Arthroscopy
Arthroscopy can be used as a diagnostic tool, although its lack of sensitivity for early lesions predisposes to a high rate of false-negative results.
