Fig. 3. Preoperative determination of primary femoral axis. (A) Surfaces of each distal femoral condyle were marked from the distal portion in order to recess to posterior end of posterior condyles. (B) The best-fit sphere from each condyle was made from registered points, and putative positioning of sphere's center was equidistant from pre-arthritic articular surface. (C) Cylindrical axis was made by connecting the centers of two spheres.