What's the Diagnosis - Case 18

History 13 year old boy with left ankle pain and limp. Notes mild discomfort of the right ankle.

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Findings Both feet demonstrate an elongation of the anterior process of the calcaneus with juxtaposition to the navicular and irregular subchondral surfaces of both bones.

These osseous findings are seen more clearly on the CT exam and on the left a small area of bony bridging is seen. The MR exam demonstrates a prominent edema pattern at the calcaneonaviuclar juxtaposition, irregular subchondral surfaces, and principally intermediate signal, but small areas of bony bridging.

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Diagnosis: Tarsal Coalition Tarsal coalition is an abnormal fusion of the tarsal bones. The fusion is either osseous or non-osseous (fibrous/cartilaginous). Coalitions can be congenital, related to trauma, or secondary to multiple other conditions. Tarsal coalition is one cause of a congenital rigid flatfoot with congenital vertical talus being the other. On imaging, there is bony or fibrocartilaginous tissue fusing the bones with irregular surfaces at the site of the fusion. Edema is elicited secondary to abnormal mechanics and can generate pain. Tarsal coalitions are bilateral 50-60% of the time.

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Postoperative views demonstrate resection of the coalition with anterior and posterior calcaneal osteotomies to restore normal architecture and subsequent mechanics of the foot.

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Resources • Resnick and Kransdorf. Bone and Joint Imaging. 2005.

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emedicine.com

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radiographics.org

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