Reference point | Description |
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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. |