Congenital tarsal coalition: Multimodality evaluation with emphasis on CT and MR imaging

Congenital tarsal coalition is a diagnosis that is often overlooked in youn g patients who first present with foot and ankle pain. Calcaneonavicular an d talocalcaneal coalitions are encountered most frequently; fusion at other sites is much less common. Tarsal coalitions may be osseous, cartilaginous , or fibrous. Calcaneonavicular coalitions are readily detected on oblique radiographs. Radiographic confirmation of talocalcaneal coalition is more d ifficult than for fusion at other locations, although several secondary rad iographic signs may indirectly suggest the diagnosis. Computed tomography ( CT) and magnetic resonance (MR) imaging are invaluable for assessment of ta rsal coalitions because they allow differentiation of osseous from nonosseo us coalitions and because they depict the extent of joint involvement as we ll as secondary degenerative changes, features of vital importance in surgi cal planning. Short-inversion-time inversion recovery MR images may reveal bone marrow edema along the margins of the abnormal articulation, an import ant clue to the diagnosis. Moreover, CT or MR imaging may be required to co nfirm the diagnosis of talocalcaneal coalition when radiographic findings a re equivocal. Because the diagnosis of tarsal coalition is often not entert ained by the clinician ordering a CT or MR imaging examination, multiplanar imaging of the ankle and hindfoot is required.