In dysgenesis of the proximal part of the femur there are three distinct groups: congenital short femur with coxa vara, congenital bowed femur with coxa vara, and congenital coxa vara.
Congenital shortening of the femur and congenital bowing of the femur are unique deformities and their classification as congenital aberrations seems obvious. The deformity of congenital coxa vara, however, is less distinctive and its differential diagnosis is therefore more difficult.
In congenital shortening of the femur with coxa vara there is severe shortening, and the most essential step in treatment is the fitting of a suitable prosthesis; surgical intervention, therefore, should be restricted to procedures which facilitate the use of a prosthetic device. Syme amputation has proved to be the most useful in this respect.
In congenital bowed femur with coxa vara, the shortening is less severe, but still marked. Either a prosthetic device or elevated shoe will be necessary. The coxa vara does not usually progress to a marked degree, and the indications for subtrochanteric osteotomy are as yet poorly defined. Because of the concomitant dysplasia of the hip, osteotomy may be contra-indicated.
In the treatment of congenital coxa vara there are three aims: (1) correction of deformity, (2) promotion of ossification of the cartilaginous neck, and (3) prevention of recurrence. In the majority of these children, the varus is rapidly progressive, and there is a wide and vertically oriented linear defect in the neck for which early radical osteotomy with bone transfixation of the femoral neck is indicated. In the minority of patients who have mild deformity or in whom the varus does not progress significantly, the indications for osteotomy are essentially functional and the procedure may be safely delayed for several years. In this mild form, correction does not have to be as radical as in the cases with severe and progressive varus.