Congenital Coxa Vara

Coxa vara deformity can be a congenital condition noted at birth, a progressive developmental disorder, or a disorder acquired as a result of trauma, Legg-Calve-Perthes (LCP) disease, slipped capital femoral epiphysis (SCFE), or metabolic or neoplastic conditions.¹,²,³,⁴ The congenital form is believed to result from a limb bud abnormality or another intrauterine process. It is often associated with other limb deficiencies, such as proximal femoral focal deficiency or fibular hemimelia. Congenital coxa vara has an incidence of approximately 1 in 25 000. It affects males and females equally, with no predilection for the right or left side, and occurs bilaterally in 30% to 50% of patients. Most patients first have painless waddling or a Trendelenburg gait between 2 and 6 years of age; a decrease in hip abduction and a limb length discrepancy, if the condition is unilateral, may also be present.²

IMAGING

Given the typical age at which coxa vara is diagnosed, plain radiographs are usually sufficient for the initial evaluation. A standing anteroposterior (AP) pelvic radiograph with the hips internally rotated to 15° helps to maximize the ability to obtain an accurate assessment of the neck-shaft angle and the Hilgenreiner epiphyseal angle (Figure 10.1A). A frog-lateral view further aids in the assessment of dysmorphic proximal femur changes (Figure 10.1B). Owing to the association with other congenital anomalies, additional screening radiographs should be considered to assess for other areas of dysplasia.

FIGURE 10.1. A-B, Preoperative standing anteroposterior (AP) pelvis with hips internally rotated and frog-lateral view of bilateral hips. Hilgenreiner epiphyseal angle is demonstrated on the AP view. The inferior neck “Fairbanks fragment” is visible on the right hip.

INDICATIONS

On plain radiographs, an inverted Y pattern may be seen at the proximal femoral physis, with a resulting fragment at the inferior neck, which is sometimes referred to as the Fairbanks fragment.¹ A neck-shaft angle of less than 90° is considered to be an indication for corrective osteotomy. The Hilgenreiner angle is subtended between the Hilgenreiner line on the AP pelvic radiograph and a line drawn through the proximal femoral physis. A child with a limp and a Hilgenreiner angle (Figure 10.1A) greater than 60°, or 45° to 60° with documented progression of varus deformity, should undergo surgical treatment.²

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