Imaging description

In adults the most frequent site for the SAPHO syndrome is the sternoclavicular region (Figure 94.1). About 65–90% of patients show involvement of the sternoclavicular region. With time all the components of the anterior chest wall can become involved particularly the sternoclavicular, upper costosternal, costochondral, and manubriosternal junctions. Radiographically the most common feature is hyperostosis, characterized by chronic periosteal reaction and cortical thickening leading to bone hypertrophy (Figure 94.1). This may be associated with enthesopathy leading to ligamentous ossification, bony bridging, and joint ankylosis. Soft tissue edema and thickening may be seen adjacent to the involved bones and joint. When the disease is advanced these changes are readily identified by radiography, but early changes of sternoclavicular hyperostosis require the use of CT for a definitive diagnosis. CT and MRI may be required for detecting serious complications of sternoclavicular hyperostosis resulting from bony overgrowth which can lead to subclavian vein obstruction and superior vena cava syndrome.

On rare occasions extra-axial SAPHO can occur in the long bones (Figure 94.2), pelvis, scapula, and tarsal bones.

Bone scintigraphy is a sensitive technique for detecting SAPHO lesions throughout the skeleton in early stages of the disease (Figure 94.1 and Figure 94.2 A). The bull horn sign in the upper anterior chest wall is diagnostic of SAPHO.

Magnetic resonance imaging demonstrates the changes due to arthritis and the bone marrow edema. MRI can also be useful in the follow-up of patients to determine active from chronic inactive lesions.