STP1531

    In Vitro Knee Wear, Kinematics, and Particle Morphology Among Different Bearing Geometries in a Mobile Bearing Knee System

    Published: Feb 2011


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    Abstract

    Excellent clinical long term results were reported from individual clinical centers for both of the two fundamental design principles—fixed and mobile bearing knee designs. Several pre-clinical studies are dealing with a direct comparison between fixed and mobile bearing knee replacements, but to our knowledge there is no published data comparing the in vitro wear and kinematic behaviour of mobile bearing designs with floating, rotating and posterior stabilized gliding surfaces. The objective of our study was to evaluate the influence of the tibio-femoral bearing type on abrasive wear, tibio-femoral kinematics and particle release for a mobile bearing knee system with three different design alternatives. Wear simulator testing on 12 e.motion® TKA devices (Aesculap, Germany) was performed according to ISO 14243-1. The knee replacements were tested for 5 million cycles on a customized 4 station knee wear simulator (Endolab, Germany) in the bearing configurations floating platform (FP), ultra-concruent rotating platform (UC) and posterior stabilized (PS). The amount of wear in the polyethylene gliding surfaces was estimated to 4.4 ± 0.9 mg/million cycles (FP design) to 2.3 ± 0.1 mg/million cycles (UC) and 5.2 ± 1.0 mg/million cycles (PS). The amplitudes of A/P displacement during 5 million cycles showed a mean value of 3.7 ± 0.33 mm (FP design), 2.3 ± 0.14 mm (UC) and 2.9 ± 0.26 mm (PS). For the I/E rotation angle, the amplitudes of the recorded mean values were 6.3° ± 0.82° (FP design), 3.7 ± 0.41° (UC) and 4.9° ± 0.48° (PS). The polyethylene particle release (mean size and morphology) is comparable for the mobile bearing articulations FP, UC, and PS. The present study demonstrates the influence of different mobile bearing types on abrasive wear, tibiofemoral kinematics, and particle release under elimination of bearing material influences.

    Keywords:

    total knee arthroplasty, in vitro knee wear, mobile bearing design, influence of bearing geometries


    Author Information:

    Grupp, T. M.
    Aesculap AG Research and Development, Tuttlingen,

    Ludwig Maximilian University Clinic for Orthopaedic Surgery, Munich,

    Miehlke, R. K.
    Knee Division, The Rhine-Main Centre for Joint Diseases, Wiesbaden,

    Knee Division, The Muensterland Centre for Joint Diseases, Muenster,

    Hintner, M.
    Endolab Mechanical Engineering GmbH, Thansau,

    Schwiesau, J.
    Aesculap AG Research and Development, Tuttlingen,

    Kaddick, C.
    Endolab Mechanical Engineering GmbH, Thansau,


    Paper ID: STP153120120016

    Committee/Subcommittee: F04.22

    DOI: 10.1520/STP153120120016


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