A talocalcaneal coalition is an abnormal bridge across the subtalar joint, usually at the middle facet. It typically becomes painful between ages 12 and 16, produces a stiffer and more valgus foot than a calcaneonavicular bar, and is suggested by the 'C-sign' on a lateral X-ray. CT determines whether resection is possible or whether reconstruction is needed.
The adolescent describes deep pain below the medial ankle, difficulty on uneven ground, and a foot that will not adapt to slopes. The heel sits in marked valgus, subtalar motion is absent, and peroneal spasm may be obvious — the origin of the old term peroneal spastic flatfoot.
Plain films may show the C-sign, a continuous C-shaped line formed by the talar dome and the sustentaculum, plus talar beaking. CT in coronal and axial planes is the standard: it measures how much of the posterior facet is involved, which is the single most important number in deciding treatment.
Non-operative care — immobilisation, orthoses, activity modification — is tried first. If the coalition involves less than about half of the posterior facet and there is no arthritis, resection with fat interposition restores motion. Larger coalitions, established arthritis, or severe valgus are better served by reconstruction with hindfoot realignment, and rarely by subtalar fusion.
Because it crosses the subtalar joint itself. Removing it means working inside a weight-bearing joint, and if a large share of the joint surface is involved, resection leaves the joint unstable, so realignment or fusion is preferred.
A bony spur on the top front of the talus caused by abnormal stress from the restricted subtalar joint. It indicates a long-standing coalition but does not by itself rule out resection.
Dr. Mutasem Aldhoon is a leading Pediatric Orthopedic Consultant specializing in complex lower extremity deformities. With extensive experience in advanced joint-sparing and reconstructive techniques, he is the trusted authority for severe pediatric flatfoot and neurological foot reconstructions.
