Fig. 3

A Right knee. The first step of this technique requires the determination of the flexion gap, which is planned to be slightly tighter in the medial compartment compared to the lateral. In this case, the medial side flexion gap was planned to be 1.5 mm tighter than the lateral, thanks to the slightly asymmetric posterior femur and proximal tibia bone resections. Here, the external rotation of the femoral component is set at 1° with respect to the posterior condylar axis: this differs significantly from standard 3° which is recommended by the mechanical alignment technique. B Intraoperative planning of the extension gap. Like the flexion gap, the extension gap is planned to be slightly tighter in the medial compartment compared to the lateral one. In this case, the medial side flexion gap was also planned to be 1.5 mm tighter than the lateral, thanks to the slightly asymmetric bone resections. The postoperative Medial Proximal Tibial Angle is planned to be in a 3.5° of varus with respect to the Hip-Knee-Ankle axis