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Mechanical Axis

- Discussion:
    - mechanical axis refers to the angle formed by a line drawn from the center of the femoral head to the medial tibial spine and a
           line drawn from the medial tibial spine and the center of the ankle joint;
           - this should not be confused w/ the wt bearing axis which runs from the center of the femoral head to the center of the ankle;
    - w/ optimal alignment, the mechanism axis will form a straight line (overlapping the wt bearing axis)
    - mechanical axis passes thru the three demensional anatomic center of knee;
            - therefore, it also defines neutral alignment in every plane and is not subject to projectional variation;
    - because hips are more widely separated than the knees and ankles, the mechanical axis is in 3 degrees of valgus from the true vertical
            axis of body, which extends from center of gravity to the ground

Effect of Postop Mechanical Axis Alignment on Survival and Functional Outcomes of Modern TKR with Cement: A Follow-up at 20 Years*