Evaluation of tarsal coalition by computed tomography.

Three cases of talocalcaneal and two calcaneonavicular tarsal coalitions were evaluated with plain radiography and computed tomography (CT). Four of five of the patients' plain films were read as normal. Two of three patients had a Harris view performed for the talocalcaneal middle facet coalitions. One was read as negative, the second as positive after five attempts at obtaining the correct angle. In addition, two of three patients with talocalcaneal middle facet coalition had conventional tomography. One was read as positive, the other as negative. Arthrography was done in one case of calcaneonavicular coalition and was suspicious for the coalition. CT was diagnostic in all five cases. It provided an accurate depiction of the coalition site. In addition, the width of the bony bar at the coalition site could be determined to help plan surgical treatment. In patients presenting with painful feet, in whom tarsal coalition is suspected, plain radiographs should be the initial screening procedure. If secondary signs are present, CT is recommended as the best imaging modality to investigate further for tarsal coalition. Also, if plain films are normal but the index of suspicion is high, CT is thought to be the next most valuable test for diagnosing tarsal coalition.