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Polyaryl-ether-ether-ketone (PEEK) and its composites provide good mechanical properties coupled with exceptionally good chemical resistance, a combination that is particularly attractive in trauma and orthopaedic applications. In considering the benefits of using carbon-fiber reinforced PEEK, especially in arthroplasty, the biological response of two different varieties of PEEK compared to ultra-high-molecular-weight-polyethylene (UHMWPE) particles was performed in vivo. MATERIAL AND METHODS: For the particle generation blocks made of UHMWPE (GUR 1020) and two different groups of prototypes were machined from PEEK (PEEK-Optima LT1, Invibio Ltd. Thornton-Cleveleys, UK) with a carbon-fiber reinforcement of 30% pitch fibers (PITCH) blended with PEEK-Optima (CFR-PEEK LT1 CP 30) and containing 30% polyacrylonitrile (PAN) based carbon fibers (CFR-PEEK LT1 CA 30), packed under nitrogen atmosphere and sterilized by ?-irradiation (30±2 kGy). The polymer particles were generated using a cryo-pulverization process using liquid nitrogen until the desired particle size and distribution was reached. The mean particle size was 0.79µm for UHMWPE, 1.22µm for PITCH and 1.39µm for PAN particles. The particles were suspended in a phosphate buffered saline solution (particle concentration 0.995~1.02mg/ml), sterilized by GAMMA irradiation and were analysed for cytotoxity and endotoxin concentration. 32 female Balb/c mice were randomly assigned to one of four treatment groups (according to the national guidelines of animal protection laws): control (n=8); CFR-PEEK pitch particles (n=8); CFR-PEEK PAN (n=8) and UHMWPE particles (n=8). 50 µl of the particle suspension were then injected into the murine left knee under sterile conditions. The leukocyte–endothelial cell interactions and the synovial microcirculation were performed by intravital fluorescence microscopy one week after particle injection to assess the inflammatory reaction (defined by measuring the rolling fraction of leukocytes, the adhaerent cells and the functional capillary density (FCD)) against the particles. Data analysis was performed using a computer-assisted microcirculation analysis system (Cap-Image). For the statistical analysis we used the Kruskal-Wallis analysis for differences within the groups, followed by an all pairwise multiple comparison procedure with a Bonferoni correction. The level of significance was set at p<0.05. RESULTS: The fraction of the rolling leukocytes, adherent cells and FCD was significantly (p<0.05) increased in all biomaterials. No significant difference was seen between UHMWPE, PITCH and PAN in these parameters. DISCUSSION: Our data suggest that carbon-fiber reinforced PEEK is comparable to UHMWPE in its inflammatory response. For this reason and due to its mechanical properties, CFR-PEEK is an attractive alternative biomaterial, even for the use in arthroplasty. |
