Femoral anteversion: Assessment based on function axes

This study describes a clinically oriented anatomical assessment of anteversion on 32 cadavers ranging from 61 to 89 years. The method used a three-dimensional reference system based on functional axes of the femur. Each soft tissue-free femur was mounted on an osteometric table and aligned to its functional axes. The long axes were defined as passing from the centre of the femoral head to the femoral attachment of the posterior cruciate ligament (PCL). A line that ran through the PCL attachment (equal distal origin of this system) and was parallel to a transepicondylar line served as a transverse axis. Anteversion of the femur was defined as an angle formed to the transverse axis by a line running through the centre of the femoral head through the midpoint of the narrowest segment of the femoral neck. The measurement mean for anteversion among these specimens was 7.4° with a range from −10.8° (retroversion) to 22.1°. There was no statistical difference in mean values (p<0.05) between sexes or between right and left sides of the group; however there were large variations for anteversions when each side in the same individual was compared (although there was no dominant side). Retroversions were observed in four of 32 femurs (12.5%). No correlation was found between the anteversion in these femurs and rotational geometry at the knee. We compared our data with those obtained by conventional techniques, by which anteversion for each femur was measured after the bone had been placed on a flat surface. The anteversion so defined was 13.1°, i.e., an average of 5.7° more external rotation induced by condylar disproportion. Such data indicate the influence of condylar disproportion on the measurement of anteversion and reveal the potential errors in measurements of anteversion that may be imposed by variations in condylar dimensions. The measurement method may be applied to computer tomographic radiographs of femora in vivo.