Tarsal coalition.

Tarsal coalition is a bridging between the tarsal bones of the foot. The bridge may be composed of bone, cartilage, fibrous tissue, or a combination of these. When symptomatic, patients usually present with hindfoot pain and frequent sprains as children, adolescents, or young adults. The classical appearance is a rigid flatfoot with heel valgus and abduction of the forefoot. Flexible cavus feet have been reported. The incidence in the general population is less than 1%, and the most common types are talocalcaneal and calcaneonavicular coalitions. The cause is attributed to failure of segmentation and differentiation of the primitive mesenchyme. Calcaneonavicular coalitions can be diagnosed with an oblique radiograph of the hindfoot. Most talocalcaneal coalitions require computerized tomography for diagnostic confirmation. Magnetic resonance Imaging may be useful for cartilaginous and fibrous coalitions. Casting is the usual initial treatment for the symptomatic individual. With treatment failure, in the absence of degenerative changes, resection of the coalition can be performed with good results. Isolated subtalar fusion may be performed for failed talocalcaneal resections. Failed subtalar fusions and failed calcaneonavicular resection may be treated with triple arthrodesis.