Fig. 4

Schematic diagram showing the MCT angle, FTA, and M–L femoral location. MCT angle under non-WB conditions in the tibial coordinate system was defined as the angle between the tangential line of an articular surface in MCT and the z-axis of the tibial coordinate system. As the assessment plane, the coronal plane passing the tibial coordinate system origin point was used. MCT angle under WB conditions in the world coordinate system was defined as the angle between the tangential line of an articular surface in the MCT and the z-axis of the world coordinate system. As the assessment plane, the coronal plane passing the middle section between the anterior- and posterior-most points of the medial compartment in the world coordinate system was used. In terms of FTA, the anatomic longitudinal axes were defined as a regression line obtained from approximating distances from these 10 centroids in the femur and 12 centroids in the tibia by the least squares method, respectively. FTA was assessed as the angle between the anatomic longitudinal axes of the femur and tibia in the coronal plane of the femoral coordinate system. Regarding M–L femoral location, the M–L location of the femur relative to the tibia was defined as the location of the origin point of the femoral coordinate system, and was assessed in the coronal plane of the tibial coordinate system