Conventional instrumentation

Patient specific instrumentation

Lower limb mechanical axis was measured on a bipodal standing leg-length anteroposterior radiograph with the patella oriented straight made three months postoperatively, using Roman software version 1.70 (Oswestry, United Kingdom). Postoperative lower limb mechanical axis was calculated from the HKA (hip-knee-ankle) angle between the femoral and tibial mechanical axes, respectively. An HKA angle greater than 180° was indicative of valgus, whereas values lower than 180° indicated varus.

Also, components position in the coronal plane was measured on both the tibial and femoral sides by the femoral (F) angle between the tangent line of the distal prosthetic condyles and the mechanical axis of the femur, and by the tibial (T) angle between the tangent line of the prosthetic tibial baseplate and the mechanical axis of the tibia. In addition in the sagittal plane, tibial slope (TS) was measured by the angle between the tangent of the tibial baseplate and the posterior cortex of the tibia on a lateral view of the knee made at three-month follow-up.

According to Mercuriali et al.