The relative incidence of tarsal coalition.

The overall incidence of tarsal coalition in the general population is unknown, but it is far less than 1%. Calcaneonavicular coalition was found to be the most common type (53%), followed by talocalcaneal coalition (37%). The other types appear infrequently. Most calcaneonavicular and talocalcaneal coalitions present as a painful foot of some type. Peroneal spastic flatfoot is a rare finding and occurred in only two of 22 talocalcaneal coalitions in the present study. Talonavicular coalitions were always associated with other congenital foot anomalies and were typically asymptomatic. Age at presentation, sex, and time to diagnosis were not statistically different among patients with coalitions at different locations. It is thought that clinical presentation corresponds to ossification of the coalition, which occurs an average of three to four years later.