Prenatal development around the sustentaculum tali and its relation to talocalcaneal coalitions.

Twenty cartilaginous talocalcaneal bridges were found in 16 cases among 142 feet from 119 embryos and fetuses ranging from 7 to 20 weeks. The cartilaginous bridges were mainly located extraarticularly between the posteromedial portion of the sustentaculum tali and the corresponding part of the talus. The incidence of talocalcaneal bridges was high in the prenatal period, especially during the ninth and tenth week; it was much less common in older specimens. This condition is attributed to either failure of or delay in differentiation of mesenchymal tissue into more specialized tissue between the posterior portion of sustentaculum tali and the corresponding part of the talus during the 7 1/2-8 1/2 postovulatory weeks.