Developmental Coxa Vara
Coxa vara is defined as any decreases in the femoral neck-shaft angle below the normal.
The term developmental coxa vara was first used by Hoffa in 1905 and later by Duncan.
Developmental coxa vara is a term reserved for coxa vara of the femur in early childhood with classical radiographic changes and no other skeletal manifestations or obvious underlying causes.
It is a developmental abnormality characterized by a primary cartilaginous defect in the femoral neck with an abnormal decrease in the femoral neck-shaft angle, shortening of the femoral neck, relative overgrowth of the greater trochanter, and shortening of the affected lower limb.
The exact cause of developmental coxa vara remains unknown.
The most widely accepted theory is that the deformity in the proximal femur results from a primary defect in endochondral ossification of the medial part of the femoral neck.
This results in the dystrophic bone along the medial inferior aspect of the femoral neck, which fatigues with weight-bearing, leading to the development of progressive varus deformity.
Another hypothesis is varus deformity is caused by excessive intrauterine pressure on the developing fetal hip, resulting in a depression in the neck of the femur.
Boys and girls are equally affected and the ratio of unilateral to bilateral cases is 1:2.
The deformity usually presents after the walking age and before 6 years of age.
Clinically, the child presents with a painless limp owing to a combination of true Trendelenburg gait and relatively minor limb length inequality in unilateral cases.
Easy fatigability or aching pain around the gluteal muscles may be a complaint. In children with bilateral involvement, the usual complaint is of a waddling gait, with or without fatigue or muscular pain.
On examination, the range of motion of the hip is reduced in all planes of motion, with limitation of abduction and internal rotation being the greatest.
The Trendelenburg test is positive. Shortening is present in unilateral cases but seldom exceeds 3 cm at skeletal maturity, even in untreated patients.
Evidence of a generalized skeletal dysplasia should be sought, especially if the family history is positive for similar deformity or short stature, the affected patient is short-statured, or there is bilateral involvement.
The diagnosis of developmental coxa vara is confirmed with a plain anteroposterior radiograph of the affected hip.
Plain anteroposterior radiographs demonstrate a decreased neck-shaft angle of the affected hip, a widened radiolucent line corresponding to the proximal femoral physis, and inverted “V”.
No treated is indicated in children with minimal symptoms, mild deformity, and mild impairment of function. These children should have a periodic radiographic assessment to assess for progressive deformity until skeletal maturity.
The presence of symptoms and the extent of proximal femoral deformity are the primary determinants of the need for surgical correction of the deformity.
Proximal femur valgus osteotomy is indicated in appropriate cases.
The long term consequences in untreated cases with severe proximal femoral deformity are the development of a stress-fracture related non-union of the femoral neck, the early arthritis of the hip, early degeneration of the spine, and limb length discrepancy.