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TKR: Rotational Alignment using AP Axis

- Discussion:
    - see rotational alignment in TKR:
    - rotational mal-alignment may lead to patellar malalignment and varus-valgus instability;
    - valgus knee may have a lateral condyle which is deficient posteriorly;
    - therefore, use of the posterior condyles as a reference, may lead to relative internal rotation of the femoral component;
    - AP Axis Method:
          - line drawn perpendicular to the AP axis of femoral trochlea will most often orient the AP cutting guide in 4 deg of external rotation;
          - use a rod placed along the deepest part of the patellar groove and the center of the intercondylar notch for proper orientation;
          - when this method is used in a knee w/ a deficiency of the posterior aspect of the lateral femoral condyle, there may be the perception that the
                   cut will be made in extreme external rotation (as well as under-resection of the lateral femoral condyle);
          - pitfalls:
                   - this method should not be used in revision knees in which the AP landmarks have been destroyed

Femoral Rotational Alignment Based on the Anteroposterior Axis, in Total Knee Arthroplasty in a Valgus Knee. A Technical Note.

Reliability of the anteroposterior axis and the posterior condylar axis for determining rotational alignment of the femoral component in total knee arthroplasty.

Relationship between frontal knee alignment and reference axes in the distal femur.

Rotational alignment in total knee arthroplasty: intraoperative inter- and intraobserver reliability of Whiteside’s line