*4.3.2 Wear against CFR-PEEK*

Besides UHMWPE, the ZrN multilayer coating also articulates against carbon-fiberreinforced poly-ether-ether-ketone (CFR-PEEK) components from a rotating hinged total knee prosthesis used in complex revision cases (EnduRo, Aesculap AG, Tuttlingen, Germany). The selection of CFR-PEEK as an articulation surface was selected, as it showed superior wear factors compared with polyethylene [67, 68] and favorable creep behavior. In an in vitro wear study, the ZrN multilayer coating was able to reduce the amount of CFR-PEEK wear particles produced from the flanges and flexion axis in comparison to the uncoated CoCrMo version of the implant by more than 90% [53]. A study on retrievals with an in vivo service between 12 and 60 months has confirmed the wear patterns on the CFR-PEEK components seen during the in vitro wear simulation test [69].
