The objective of our study was to determine the mechanical stress conditions under tibiofemoral loading with an overlay of knee\nkinematics in deep flexion on two different mobile bearing designs in comparison to in vivo failure modes. This study investigates\nthe seldombut severe complication of fatigue failure of polyethylene components atmobile bearing total knee arthroplasty designs.\nAssuming a combination of a floor-based lifestyle and tibial malrotation as a possible reason for a higher failure rate in Asian\ncountrieswe developed a simplified finite elementmodel considering a tibiofemoral roll-back angle of 22? and the range of rotational\nmotion of a clinically established floating platform design (e.motion FP) at a knee flexion angle of 120? in order to compare our\nresults to failure modes found in retrieved implants. Compared to the failure mode observed in the clinical retrievals the locations\nof the occurring stress maxima as well as the tensile stress distribution show analogies. Fromour observations, we conclude that the\nnewly introduced finite element model with an overlay of deep knee flexion (lateral roll-back) and considerable internally rotated\ntibia implant positioning is an appropriate analysis for knee design optimizations and a suitable method to predict clinical failure\nmodes.
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