Validity and reliability of measuring femoral anteversion and neck-shaft angle in patients with cerebral palsy

Abstract

Background: Increased femoral anteversion and coxa valga are common in patients with cerebral palsy. The purpose of the present study was to determine the validity and reliability of the methods that are commonly used to measure the proximal femoral geometry in patients with cerebral palsy.

Methods: Thirty-six consecutive patients (mean age, eleven years; range, five to twenty years) with cerebral palsy were enrolled in the present study. The validity and the interobserver reliability of the physical examinations performed by three examiners were determined by comparing the results of a trochanteric prominence angle test, hip internal rotation measurements, and hip external rotation measurements (all with the patient in the prone position) with the amount of femoral anteversion on two-dimensional computed tomography. Validity and intraobserver and interobserver reliability were assessed by comparing the neck-shaft angle on the anteroposterior internal rotation radiograph of the hips with that on the multiplanar reformatted computed tomographic image.

Results: The trochanteric prominence angle test showed excellent concurrent validity (R = 0.862, p < 0.001) and reliability (intraclass correlation coefficient, 0.809). Hip internal rotation also showed good concurrent validity (R = 0.787, p < 0.001) and excellent reliability (intraclass correlation coefficient, 0.889), whereas hip external rotation appeared to be unsuitable for predicting femoral anteversion. The neck-shaft angle on the anteroposterior internal rotation radiograph of the hips showed excellent concurrent validity (R = 0.892, p < 0.001) and reliability (intraclass correlation coefficient, 0.912).

Conclusions: A physical examination for determining femoral anteversion and the neck-shaft angle as measured on the internal rotation radiograph of the hips appear to be clinically relevant methods for evaluating the proximal femoral geometry and version in patients with cerebral palsy. Computed tomographic examination can probably be replaced by physical examination and an anteroposterior internal rotation radiograph of the hips for patients with stable hips who are able to walk.