Femoral anteversion measured by ultrasound and CT: a comparative study.

Both computed tomography (CT) and ultrasonography have been used successfully to estimate the femoral anteversion (AV) angle. In this study, AV angles in 20 human adult femurs were determined by ultrasonography and CT and the measurements compared. On CT the real AV angle was measured as the angle between the head-neck centreline and the posterior condylar plane. In addition, the angle between the anterior head-trochanter (HT) tangent and the posterior condylar plane was determined. The latter angle was also measured by ultrasonography using the tilted transducer technique. The mean interobserver variation in the ultrasound measurements was 1.9 degrees. We found ultrasonography to correlate very well with CT, both when comparing with the HT angle (r = 0.95) and with the AV angle (r = 0.93). The HT angle was on average 4 degrees greater than the AV angle. In this study the accuracy of ultrasonography was +/- 5 degrees and the method is recommended for screening in patients with rotational disorders of the femur.