Congenital ball-and-socket anomaly of the ankle.

We present the clinical and radiographic appearance of 11 patients with a ball-and-socket ankle joint with an average follow-up of 13.7 years. Ten patients demonstrated parallel symptoms of the femur-fibula-ulna syndrome (FFU) associated with a mean leg-length discrepancy of 4.3 cm (range, 2-20). In six patients, an annual follow-up of talar development was possible. Radiographically the patients showed an additional tarsal coalition at a mean age of 4.8 years (range, 3.2-5.9). This earlier fusion could be detected by an arthrographic examination. All patients had no clinical complaints except a slight reduction of hindfoot mobility. The ball-and-socket ankle joint is presumably not congenital itself but secondary to congenital conditions in the peritalar region.