MR imaging and CT in the assessment of osseous abnormalities of the ankle and foot

Delineation of coexistent bony and soft tissue abnormalities is paramount when one is dealing with pathologic conditions in the ankle and foot. Advanced cross-sectional techniques, including CT and MR imaging, are often superior to conventional radiography in the assessment of clinical conditions involving small ossicles such as the os trigonum syndrome, fractured or necrotic sesamoids, and symptomatic accessory tarsal navicular bone. Because of the limitations of CT in assessing soft tissue abnormalities and the limitation of MR imaging in assessing bony pathology, the two modalities often can provide information, that is valuable for a complete diagnostic understanding. Presently, when cost containment must be addressed, clinicians and radiologists must understand the distinct yet complementary roles that CT and MR imaging play in the diagnosis of osseous abnormalities of the ankle and foot. CT provides a detailed road map of the bony anatomy, that can be crucial when surgical planning is contemplated. Also, subtle cortical disruption, fragmentation, and bone density changes can be easily assessed based on CT images. Conversely, MR imaging provides superb characterization of bone marrow edema, ensuing avascular necrosis, and the associated soft tissue abnormalities often seen in these painful disorders.