A New Method for Measurement of Femoral Anteversion: A Comparative Study with Other Roentgenographic Methods

Lee, Duk Yong; Chung, Moon Sang; Lee, Sang Hoon; Lee, Choon Ki; Lee, Chong Suh; Lyu, Suk Joo; Huh, Min Gang

Abstract

The authors designed a new biplanar method of measuring femoral anteversion, which may be considered a modified Magilligan's method. In addition to true A-P view, a true lateral view is taken, instead of trans-cervical lateral view in the Magilligan's technique. Acute angles(Î± and r) between the long axis of the femoral shaft and the femoral neck on both the A-P and lateral films are measured. The true angle (r1) of anteversion is calculated by substituting the values of tan(90-Î±) and tan (90-r) for the trigonometric formula tan r1 = tan(90-Î±)/tan(90-r). The measurement by the Magilligan's and the author's methods and the conventional CT method were compared with direct measurement for their accuracy in 20 sdult dried femora. Also correlativity among these three methods were analyzed clinically in 40 femora of 20 children. Following results were obtained, 1. Compared with the direct measurement, the Magilligan's, suthor's methods and CT method deviated an average of + 6.050 degrees, + 3.600 degrees and âˆ’1.150 degrees, respectively, all three being statistically accurate(p>0.05). The values for the latter two were closer to that of direct measurement. However, there was no statistical difference between the two. 2. The Magilligan's method overestimated in 95% and underestimated in 5% of the cases, and there was over-or under- estimation of less than 5 degrees in 20% and less than 10 degrees in 95%. The author's method overestimated in 70% and underestimated in 0% of the cases, and there was over-or under-estimation of less than 5 degrees in 55% and less than 10 degrees in 100%. The CT method overestimsted in 30% and underestimated in 60% of the cases, and there was over-or under-estimation of less than 5 degrees in 95 and less than 10 degrees in 100%. Both Magilligan's and autor's methods tended to overestimate and the CT method tended to underestimate(p<0.05). 3. The correlation coefficients among the Magilligan's and author's methods, the Magilligan's and CT methods, and author's and CT methods were 0.830, 0.592, 0.478 respectively, in clinical aspects. It is concluded that author's new method of biplanar measurement of femoral anteversion is more accurate than the Magilligan's method, while it is not less accurate than the conventional CT method.