Limb lengthening of a rare case of congenital femoral deficiency with an unstable knee

Abstract

Congenital femoral deficiency (CFD) is a rare birth defect that is characterized by a short femur, associated with hip and knee deformity, deficiency, or instability. Children with severe CFD may need multiple deformity correction or lengthening procedures to reduce axial malalignment and limb length discrepancy (LLD). During limb lengthening, it can occur knee subluxation or dislocation, a severe treatment-related complication. We report a 15-year-old girl with a CFD with a previous episode of posterior subluxation of the knee during a femoral lengthening using a monolateral external fixator. She had a 13 cm LLD and coxa vara; therefore, it was applied a knee spanning Ilizarov fixator with a double osteotomy of the femur for gradual correction. At 11 months following Ilizarov application, a complete correction was achieved, and the circular fixator was removed. Knee joints of patients with CFD show highly variable grades of instability. Adequate surgical techniques, preventive measures, and early detection of signs of subluxation can lead to good functional results. Femur lengthening with a preventive bridging of the knee with an Ilizarov frame is a safe and effective way of treating patients with CFD.