Anatomic femoral axis

The anatomical femoral axis is a landmark used to assess angular deformities of the femur and provide guidance for corrections.

In the frontal plane, the anatomical femoral axis is determined from a ventrodorsal radiograph of the hips. The dog is positioned dorsal recumbency, pelvic limbs extended caudally, femurs parallel to each other. Positioning is considered satisfactory if :

• the pelvis is symmetrical (iliums and obturator foramina are symmetrical)

• the femur cortex pass through the middle of the sesamoid bones of the gastrocnemius muscle

• the patellas are centred on the trochlea of femur.

Two lines, perpendicular to the diaphysis of the femur, are drawn at the proximal third and at half the length of the femur. The anatomical femoral axis is the axis connecting the midpoints of these lines.

In the sagittal plane, the anatomical femoral axis is determined from a medio-lateral radiograph of the entire femur. Positioning is considered satisfactory if the medial condyle and the lateral condyle are superimposed.

Two lines, perpendicular to the femoral shaft, are drawn at the proximal third and half-way along the femur. The anatomical femoral axis is the axis connecting the midpoints of these lines.

Another way of describing the anatomical femoral axis in the sagittal plane is to break it down into a proximal anatomic femoral axis and a distal anatomic femoral axis.