Hypoplasia of the fibula.

Fibular hypoplasia occurs in differing degrees of severity with fibular hemimelia as its most severe form. Normally the distal epiphyseal plate of the fibula is at the same level as the distal end of the distal tibial epiphysis, whereas the tip of the proximal fibular epiphysis is level with the proximal tibial epiphyseal plate. Varying degrees of shortening of the fibula in relation to the tibia were found in 14 children, 6 of them boys. Shortening at the distal end of the tibia leads to instability of the ankle. Shortening at the proximal end of the fibula leads to hypoplasia of the lateral tibial plateau and valgus deformity of the knee. Syme type ankle disarticulation became necessary in five cases of fibular hemimelia because of leg length discrepancies or ankle instability.