Purpose: Knowledge of the radiological axes in the normal lower limb is important for correction and reconstruction surgery. Classically, the femorotibial mechanical axis presents a zero angle on the anteroposterior view, with 3° femoral valgus being compensated by an equivalent tibial varus. Reference data have however been established with questionable methodology because they have been obtained with small selected samples.
Material and methods: We obtained teleradiograms of the lower limbs in 100 healthy volunteers free of any disease of the lower limbs and selected randomly among patients undergoing surgery for trauma or degenerative lesions of the upper limb. The following angles were measured by the same senior surgeon: mechanical femorotibial angle, orientation of the femoral condylar complex in relation to the mechanical axis of the femur, angle between the mechanial axis and the anatomic axis of the femur, orientation of the tibial plateaux in relation to the mechanical axis of the tibia.
Results: Sixty-nine men and 31 woman, mean age 39 years (range 17 – 62 years) participated in this study. The mean mechanical femorotibial angle was 179° (SD 3°, median 179°, range 168°–185°). The mean orientation of the femoral condylar complex in relation to the femoral mechanical axis was 91° (SD 2°, median 91°, range 86°–98°); 17 subjects had the classical value of 93°. The mean angle between the mechanical and anatomic axis of the femur was 6° (SD 1°, median 6°, range 3°–9°); 29 subjects had the classical value of 7°. The mean orientation of the tibial plateaux in relation to the mechanical axis of the tibia was 88° (SD 2°, median 88°, range 82°–84°); 14 subjects had the classical value of 87°.
Discussion and conclusion: The values considered to be normal in the literature only included 15–20% of the subjects in this study. Although there could be a theoretical selection bias in this series, it can be assumed that there is a wide dispersion of “normal” values around the means. The pertinence of this dispersion in clinical practice remains to be established. The question of individualising reconstruction or prosthetic procedures is raised.
