Coupling mechanism of bioinspired artificial composite synovial fluid on tribological behavior of artificial joints

The changes in the components of the synovial fluid in the human body have an important influence on the tribological behavior of artificial joints. Based on the component concentration of the synovial fluid after arthroplasty, the "hard-soft" joint pair materials composed of cobalt-chrome-molybdenum (CoCrMo) and high crosslinked polyethylene (XLPE) are used as the research object. The composite synovial fluid with different concentrations of albumin (Alb), γ-globulin (γ-Glo), hyaluronic acid (HA), and phospholipids (PLs) are prepared. Based on studying the influence mechanism of single component concentration change on the tribological properties of joint pair materials, the friction and wear behavior of joint pair materials under different composite synovial fluids are systematically explored. The coupling mechanism among the components is clarified, and the wear mechanism of the joint pair materials under different composite synovial fluids is revealed. In addition, the results of 2 million in vitro simulated wear experiments of CoCrMo-XLPE artificial joint in the composite synovial fluid are further studied. Further, it validates the influence of the composition concentration of the composite synovial fluid on the friction and wear properties of artificial joints under actual working conditions. The results show that the four main components in the composite synovial fluid have a great influence on the friction and wear properties of the "hard-soft" joint pair materials. When the concentration of PLs increases from 0.00 mg/mL to 0.45 mg/mL, the wear rate decreases by 69.6% and the coefficient of friction (COF) decreases by 63.3%. The coupling mechanism between PLs, HA, and protein significantly affects the adsorption of the membrane and affects the tribological behavior of the artificial joint. In addition, the simulated wear results of artificial joints in composite synovial fluid are consistent with those of friction and wear tester. It shows that the concentration of each component in the composite synovial fluid significantly affects the lubrication of the artificial joint, and the influence degree becomes more obvious during long-term service. To sum up, this study can provide the theoretical basis for the study of the composite synovial fluid and the improvement of lubrication performance of artificial joints and is of great significance for prolonging the service life of artificial joints.