A new method using ultrasound for measuring femoral anteversion (torsion): technique and reliability.

This paper reports details of a new method using medical ultrasound for measuring femoral anteversion (strictly torsion), and a reliability study of the method separately on each of 10 healthy children and 20 adults. The method involves using a static-image B-mode ultrasound scanner to obtain scans at the hips and knees of the lower limbs. A technique using bone-surface contours is reported for defining, on each hip scan, the head-neck line and, on each knee scan, the transcondylar line. By superimposing the transcondylar line on the head-neck line, the angle of femoral anteversion (torsion) was calculated for each limb. In the reliability study, scans were obtained three times at both hips and knees of each subject. The femoral anteversion was measured for each limb. The intra-observer error was within +/- 2.3 degrees (95% confidence limits) between scans, which was not statistically significant for the measured anteversion in each of the right and left femora of children and adults separately. To test the validity of the tracing method used to calculate femoral anteversion, one set of scans from the hip and knee of each subject was measured four times; no significant difference was found between tracings for the measurements of femoral anteversion. The ultrasound method is recommended for clinical use. We consider the static-image B-mode scanner to be the instrument of choice for measuring femoral anteversion in living subjects.