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Table 1 Bony landmarks as reference points for 3D-CT digitizing to define the traditional mechanical axis

From: Intra- and inter‐observer reliability of implant positioning evaluation on a CT-based three‐dimensional postoperative matching system for total knee arthroplasty

Reference point Description
Center of the femoral head Four points were set on the surface of the femoral head (three in the sagittal or coronal plane, and another point in the axial plane). A ball that contacts all four points was automatically created to approximate the femoral head. The center of the ball was defined as the center of the femoral head.
Medial/lateral epicondyle of the femur The tip of the medial/lateral epicondyle was marked on the axial plane, by referring to the coronal plane at the same time.
Proximal/distal center of the tibia Three points were set in the axial plane inside the medullary canal of the tibia at the proximal/distal one-third of the tibia. The center of the circle that contacted all three points was defined as the center of the proximal/distal tibia.