A new method for measurement of femoral anteversion. A comparative study with other radiographic methods.

A new biplanar method of measuring femoral anteversion, which may be considered a modified Magilligan's method, is described. In addition to the true antero-posterior radiograph, a true translateral radiograph is taken, instead of a transcervical lateral radiograph as in the Magilligan method. The acute angles (alpha and gamma) between the long axes of the shaft and neck of the femur on both the antero-lateral and lateral radiographs are measured. The angle (gamma') of anteversion is obtained by the trigonometric formula; tan gamma' = tan/tan alpha. The femoral anteversion in 20 adult dried femora and 40 femora in 20 children was measured by the Magilligan method, the authors' method and the conventional CT method. Compared with direct measurement in the dried femora, it was found that both the Magilligan and the authors' methods tended to overestimate and the CT method tended to underestimate (p < 0.05) the anteversion. In children's femora, a similar trend was observed among the three methods and the measurements by each method differed significantly from the other (p < 0.05). We feed that our method of biplanar measurement of femoral anteversion is more accurate, although probably marginally, than the conventional Magilligan method. It also has some relative advantages in clinical application in that positioning is easier, rotation is better controlled, and less time is consumed.