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    Effects of Patient and Surgical Alignment Variables on Kinematics in TKR Simulation Under Force-Control

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    Simulation of total knee replacement(TKR) is typically achieved by integrating sliding/rolling motions and loads between the implant's articulating surfaces during an activity cycle such as walking. Clinically, however, important variations in implant alignment and duty occur due to variability in patient anatomy/arthritic deformity, compounded by choices or errors in surgical installation. This study investigated the effects of the activity cycle severity, frontal plane alignment, relative femoral/tibial component rotational position, and the tightness of the posterior cruciate ligament (PCL). Seven different (four fixedbearing and three mobile-bearing) cruciate-retaining TKRs with different inherent constraints were tested on a force-control knee simulator. As well as the ISO standard wave forms for walking, an Enhanced Duty Cycle was used. The resulting anterior-posterior displacements and axial rotations were increased with the Enhanced Duty Cycle. Changing the line of action of the compressive force in the frontal plane (varus valgus over/under-correction) did not appreciably change the kinematics. Rotating the tibial component shifted the rotational curves in the same direction as the misalignment. The PCL tightness produced the most noticeable effect on kinematics; a tight PCL reduced both displacements and rotations, and a loose PCL did the opposite.


    knee simulator, knee kinematics, mobile bearing knee, knee surgical technique, TKR wear

    Author Information:

    Haider, H
    Associate Professor, University of Nebraska Medical Center, Omaha, NE

    Walker, P
    Research Professor, New York University Medical Center and Hospital for Joint Diseases, New York, NY

    DesJardins, J
    Research Associate, Clemson University, Clemson, South Carolina

    Blunn, G
    Professor, Centre for Biomedical Engineering, Royal Free and University College Medical School, Stanmore,

    Committee/Subcommittee: F04.93

    DOI: 10.1520/STP40880S