[Myositis ossificans circumscripta: the contribution of imaging]

Illustrate the specific and nonspecific aspects of myositis ossificans circumscripta (MOC) in standard imaging, cross-sectional imaging (sonography, CT, and MRI), and bone scintigraphy.

Eight patients presenting with MOC (three men and five women) were explored using standard radiography (eight cases), sonography (seven cases), scintigraphy (four cases), CT (six cases), and MRI (four cases).

Standard x-rays and sonography of the soft tissue showed a well-defined mass containing calcifications in 75% of the cases. The CT scan diagnosed MOC in four cases, showing calcified masses separated from the adjacent bone by a clear radiotransparent border or afferent peripheral tumoral calcifications highly suggestive of MOC. MRI was nonspecific. Bone scintigraphy showed hyperfixation in the four cases imaged.

Standard x-rays were useful to demonstrate the calcifications of MOC and to identify their relation with the subjacent bone. Sonography and bone scintigraphy were interesting in monitoring the lesion's maturation. In addition to early detection of calcifications, CT can precisely localize the lesion before surgical ablation. MRI is a very sensitive technique in detecting small lesions at an early stage, but it is nonspecific and does not remove the necessity of biopsy to eliminate the possibility of a malignant disease.