Radiographic diagnosis of posterior facet talocalcaneal coalition.

Tarsal coalition is a relatively common segmentation abnormality of the hindfoot that can result in foot and ankle pain in both adolescents and adults. The most common types are calcaneonavicular and talocalcaneal. Posterior subtalar facet coalition is less common. We present a 10-year-old boy with a history of chronic left ankle and foot pain. Radiographs demonstrated calcaneal "humpback" sign, representing the posterior subtalar bony coalition, and CT demonstrated in more detail the extent of bony and fibrous coalition. These findings led to surgical intervention.