MR Findings of the Osteofibrous Dysplasia

OBJECTIVE: The aim of this study was to describe MR findings of osteofibrous dysplasia. MATERIALS AND METHODS: MR images of 24 pathologically proven osteofibrous dysplasia cases were retrospectively analyzed for a signal intensity of the lesion, presence of intralesional fat signal, internal hypointense band, multilocular appearance, cortical expansion, intramedullary extension, cystic area, cortical breakage and extraosseous extension, abnormal signal from the adjacent bone marrow and soft tissue and patterns of contrast enhancement. RESULTS: All cases of osteofibrous dysplasia exhibited intermediate signal intensity on T1-weighted images. On T2-weighted images, 20 and 4 cases exhibited heterogeneously intermediate and high signal intensity, respectively. Intralesional fat was identified in 12% of the cases. Internal low-signal bands and multilocular appearance were observed in 91%. Cortical expansion was present in 58%. Intramedullary extension was present in all cases, and an entire intramedullary replacement was observed in 33%. Cortical breakage (n = 3) and extraosseous mass formation (n = 1) were observed in cases with pathologic fractures only. A cystic area was observed in one case. Among 21 cases without a pathologic fracture, abnormal signal intensity in the surrounding bone marrow and adjacent soft tissue was observed in 43% and 48%, respectively. All cases exhibited diffuse contrast enhancement. CONCLUSION: Osteofibrous dysplasia exhibited diverse imaging features ranging from lesions confined to the cortex to more aggressive lesions with complete intramedullary involvement or perilesional marrow edema.