Wedge-shaped distal tibial epiphysis in the pathogenesis of equinovalgus deformity of the foot and ankle in tibial lengthening for fibular hemimelia

Fibular hemimelia is associated with an equinovalgus deformity of the foot and ankle and different degrees of wedging of the distal tibial epiphysis. This deformity is often a major problem during lengthening of the shortened tibia. To determine the significance of the wedge-shaped distal tibial epiphysis in the pathogenesis of the equinovalgus deformity of the foot and ankle during and after lengthening, we reviewed 20 patients who had undergone tibial lengthening by either the Wagner or the Ilizarov technique. The mean duration of followup after removal of the fixator was 5.2 years (range, 2.3-9.7 years). Three types of wedge-shaped distal tibial epiphyses were identified. A mildly wedged (type I) epiphysis was found in seven patients, a moderately wedged (type II) epiphysis was found in seven patients, and a severely wedged (type III) epiphysis, in six patients. Premature fusion of the lateral part of the distal tibial physis and growth retardation of the tibia were common after lengthening in patients with the type II or type III epiphysis. After lengthening, all patients with a type II or type III epiphysis had a recurrence or aggravation of foot deformities that existed before lengthening. This usually necessitated various secondary operative procedures to obtain a plantigrade foot. We believe that after lengthening, one should anticipate varying degrees of mild growth retardation and minimal foot deformity in patients with type I epiphysis, worsened asymmetric growth retardation and progressive foot deformity in patients with type II epiphysis, and severe growth retardation and severe foot deformity in patients with type III epiphysis.