[A case of bilateral isolated talonavicular synostosis in childhood--observations of tarsal joint function and functional adaptation of the proximal ankle joint].

A rare case of bilateral isolated coalition of the talonavicular joint with ball and socket ankle joint is presented. Range of motion of the subtalar joint and hindfoot mobility were measured intraoperatively. The following conclusions may be drawn on development and function of the ankle joint complex: Isolated talonavicular synostosis in the growing foot results in marked impairment of subtalar range of motion. The development of a ball and socket ankle joint may be caused thereby, if tarsal hypomobility becomes effective at an early stage of growth.