Measurement of femoral torsion: comparison of standard roentgenographic techniques with ultrasound.

Measurement of femoral torsion by ultrasound was compared with measurements by standard roentgenographic techniques in a femoral model and in a clinical study. Magilligan, Ryder-Crane, and fluoroscopic determinations on the femoral model demonstrated acceptable interobserver and intraobserver variance. With high degrees of femoral torsion, ultrasound readings were less accurate and significantly lower than the actual angle of femoral torsion. In the clinical study, ultrasound measurements were compared with Magilligan measurements in 29 hips. Similar to the model, ultrasound readings were lower and discrepancy was greater at higher angles of torsion.