ABSTRACT
Tarsal coalition is an embryologic failure of segmentation of mesenchymal tissue in the hindfoot and midfoot with secondary failure of formation of the normal hindfoot or midfoot joints. Tarsal coalitions may be solitary, massive or multiple. Solitary coalitions involve a part of two adjacent bones while massive coalitions involve all of two adjacent tarsals. The most common solitary coalitions are talocalcaneal and calcaneonavicular. The exact incidence is unknown, as some individuals are asymptomatic and thus the diagnosis is never made. Bilaterality is present in 50–60 percent of affected individuals. Massive tarsal coalitions frequently involve the talus and the calcaneum and are often associated with fibular hemimelia. A proportion of children with this form of tarsal coalition have ball-and-socket ankle joints. Multiple tarsal coalitions are a part of multiple synostosis syndromes. In a small proportion of these patients significant deformities occur at the hindfoot and midfoot.
