No difference in in vivo polyethylene wear particles between oxidized zirconium and cobalt-chromium femoral component in total knee arthroplasty

Purpose Polyethylene wear particle generation is one of the most important factors affecting mid-to long-term results of total knee arthroplasties. Oxidized zirconium was introduced as a material for femoral components to reduce polyethylene wear generation. However, an in vivo advantage of oxidized zirconium on polyethylene wear particle generation is still controversial. The purpose of this study was to compare in vivo polyethylene wear particles between oxidized zirconium total knee prosthesis and conventional cobalt-chromium (Co-Cr) total knee prosthesis. Methods Synovial fluid was obtained from the knees of 6 patients with oxidized zirconium total knee prosthesis and from 6 patients with conventional cobalt-chromium (Co-Cr) total knee prosthesis 12 months after the operation. Polyethylene particles were isolated and examined using a scanning electron microscope and image analyser. Results Total number of particles in each knee was 3.3 +/- 1.3 9 10(7) in the case of oxidized zirconium (mean +/- SD) and 3.4 +/- 1.2 x 10(7) in that of Co-Cr (n.s.). The particle size (equivalent circle diameter) was 0.8 +/- 0.3 mu m in the case of oxidized zirconium and 0.6 +/- 0.1 mu m in that of Co-Cr (n.s.). The particle shape (aspect ratio) was 1.4 +/- 0.0 in the case of oxidized zirconium and 1.4 +/- 0.0 in that of metal Co-Cr (n.s). Conclusions Although newly introduced oxidized zirconium femoral component did not reduce the in vivo polyethylene wear particles in early clinical stage, there was no adverse effect of newly introduced material. At this moment, there is no need to abandon oxidized zirconium femoral component. However, further follow-up of polyethylene wear particle generation should be performed to confirm the advantage of the oxidized zirconium femoral component.