Congenital coxa vara: computed tomographic analysis of femoral retroversion and the triangular metaphyseal fragment

Three patients with congenital coxa vara studied with two- and three-dimensional computed tomographic (2DCT and 3DCT) methods are reported. In all cases, the femoral retroversion was documented and subsequently corrected by proximal femoral osteotomy. In two patients with isolated coxa vara, the physeal-femoral neck angle was decreased as seen in slipped capital femoral epiphysis in adolescents. Our studies suggest that the triangular metaphyseal fragment reflects a Salter-Harris type II separation pattern through the defective femoral neck. The epiphysis and attached triangular fragment slip from the normal superoanterior portion of the neck in an inferior-posterior direction. The treating surgeon should be aware of the often marked femoral retroversion component present in severe congenital coxa vara. This knowledge allows surgical planning for corrective osteotomies that will better normalize hip mechanics. A combination of marked valgus and flexion with internal rotation of the distal fragment are required to fully correct the deformity.