TARSAL COALITION - A BLINDED COMPARISON OF MRI AND CT

Objective. To determine how well MRI can detect tarsal coalition compa red with CT, the cur: rent imaging standard. Materials and methods, Co ronal and axial CT and MRI were performed within 3 weeks of each other on 40 feet in 20 consecutive patients referred with symptoms of possi ble tarsal coalition. Scans;were read independently in blinded fashion by different imagers, Coalitions were either complete (osseous) or in complete (non-osseous). Results were compared with available surgical data and clinical follow-up. Results. Both modalities prospectively id entified 15 coalitions (9 patients) and each missed 1 calcaneonavicula r coalition. Twenty-three of the remaining 24 feet were negative for c oalition on both CT and MRI, An atypical incomplete talocalcaneal coal ition seen on CT was not identified prospectively on MRI. Conclusion. MRI is very good for detecting tarsal coalition and has a high rate of agreement with CT, the imaging ''gold standard.'' When clinical suspi cion for coalition is high, CT remains a more cost-effective diagnosti c modality. If other causes for ankle pain are also entertained, MRI c an be performed and provide nearly equivalent diagnostic accuracy for detecting tarsal coalition.