[Deviations in the axes of the lower extremities]

Deviations in the axes can be physiological or pathological. During growth, the axes of the lower extremities undergo significant changes. The femoral neck-shaft-angle decreases from 150 degrees on average at birth to 120 degrees on average at the end of growth. The lower leg is bowed in a varus direction at birth. After a child begins to walk, the knee axis deviates to a slight valgus. This goes back to normal before the age of ten. Pathologic deviations of the axis are rare. They occur in congenital deformations, after trauma or infection, or as a result of metabolic diseases. In association with coxa vara pseudarthrosis of the femoral neck usually develops. Therefore this deformation has to be treated. Correction is best made with a Y-shaped osteotomy according to Pauwels. At the lower leg, a deviation of 15 degrees from the normal axis is usually an indication for operative treatment. In children and adolescents, corrections are best made with (monolateral) external fixators. They allow early weight bearing, which is especially desirable in bilateral corrections.