Proximal anatomic femoral axis

The proximal anatomic femoral axis is a landmark used to assess angular deformities of the femur and provide guidance for corrections. It is determined in the sagittal plane from a mediolateral radiograph of the entire femur. The position is considered acceptable when the medial condyle and the lateral condyle are superimposed.

A first line is drawn between the lesser trochanter and the proximal part of the trochlea of femur. This line divides the femur into 4 identical segments. In the proximal segment, two lines are drawn perpendicular to the diaphysis of the femur. The proximal anatomic femoral axis connects the midpoints of these two lines.

Peterson et al. 2020 proposed an alternative definition of the proximal anatomic femoral axis: to determine it, the length of the femur is measured from the most proximal aspect of the greater trochanter to the intersection of the distal anatomic femoral axis and the cranial cortical of the femur. This length is divided into thirds, and the midpoint of the femoral diaphysis is identified at each third. The proximal anatomic femoral axis is the straight line connecting the midpoints of the diaphysis of the first and second thirds.