Femoral anteversion refers to the orientation of the femoral neck in relation to the femoral condyles at the level of the knee. In most cases, the femoral neck is oriented anteriorly as compared to the femoral condyles. In the case of posterior orientation, the term femoral retroversion is also applied.
Actually describing the intrinsic rotation of the femur over its length from the hip to the knee, femoral anteversion may also be more aptly termed femoral antetorsion.
Femoral anteversion averages between 30-40° at birth, and between 8-14° in adults 1, with males having a slightly less femoral anteversion than females 2.
Some authors will distinguish femoral neck version as the angle of the femoral neck relative to the pelvic horizontal (interischial line), with a normal range of 5-25 degrees of anteversion 3 and femoral neck torsion as the angle between the femoral neck and posterior condylar axis of the distal femur, with a normal range of 10-20 degrees of antetorsion 4.
An increased femoral anteversion is often seen in patients with developmental dysplasia of the hip 5. Moreover, it has been shown that abnormal femoral anteversion can contribute to the development of femoroacetabular impingement (FAI); reduced femoral anteversion is associated with cam-type FAI 6.
Femoral anteversion can be determined by measuring the angle formed between the long axis of the femoral neck and a line parallel to the dorsal aspect of the femoral condyles (posterior condylar axis, or PCA) on axial slices at MRI or CT.
Depending on the measuring tools available this can be done either directly by measuring the anteversion angle over two different axial slices at once (one at hip level and one at knee level) or by taking two separate angle measurements using a horizontal line as a static reference on either slice, and subsequently adding or subtracting the resulting angles, depending on their orientation in the same direction (e.g. both measurements clockwise > subtract) or in different directions (e.g. femoral neck measurement counterclockwise and condyle measurement clockwise > add).
Treatment and prognosis
In many patients, there is no need for an individual correction of an abnormal femoral anteversion. In patients with severe femoral anteversion or retroversion, a subtrochanteric rotational osteotomy of the femur may be performed 7.
History and etymology
The concept of femoral anteversion was first described in 1868 by the anatomist Julius Wolff 8.
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