Ultrasound examination for measurement of femoral anteversion in children.

Femoral anteversion (AV) angles were determined by ultrasound and biplanar radiography in 63 children aged 3-11 years. With the patient supine, knees flexed 90 degrees, and legs kept vertical, only one ultrasound scan of the proximal femur was needed. The anterior tangent of the femoral head and the greater trochanter was used as the reference line. The transducer was tilted until this tangent appeared horizontal on the monitor screen, and the angle of tilt, which represents the AV angle, was measured with an attached clinometer. There was a high correlation between ultrasound and radiographic results (r = 0.71). However, the AV angles appeared an average of 5.5 degrees larger by ultrasound. Thus, a correction factor of 5 degrees should be subtracted from the angle measured by ultrasound to obtain the actual AV angle in children. Because ultrasound does not require ionizing radiation, and because reliable results are obtained, our technique is recommended for screening of children with rotational disorders of the femur.