Myositis ossificans circumscripta: computed tomographic diagnosis.

Computed tomography was performed in five patients with myositis ossificans circumscripta. In three cases, and possibly four, CT scans obtained during the active stage of the pathologic process demonstrated findings that in general corresponded to the "zone phenomenon" seen on histology, although a distinct peripheral ring of ossification was not always present. In these patients, CT was useful in limiting the differential diagnosis and obviating surgery. In the fifth patient, with long-standing myositis ossificans, CT showed complete ossification indicative of the mature phase of the pathologic process and was helpful in planning surgical resection.