Talonavicular synostosis.

CONGENITAL fusion of two or more bones of the tarsus is referred to as tarsal coalition and affects some 2% of individuals. All forms of coalition from involvement of two adjacent bones to massive tarsal fusion have been recorded. Tarsal fusion was well recognised by anatomists long before attention was drawn to its clinical significance. Slomann (1921) and Badgley (1927) were first to describe the association of fusion of the calcaneum and navicular with a rigid form of flat foot. Harris and Beath (1948) in their classical paper on peroneal spastic flat feet found that a large proportion were due to a bridge of bone arising from the medial side of the talus, crossing the subtalar joint and joining a mass of bone on the medial side of the calcaneum.