Wear Of Uhmwpe In Artificial Joints Under Cross-shear Conditions

Ultra high molecular weight polyethylene(UHMWPE)is widely used clinically as artificial joint implants due to its good mechanical properties,abrasion resistance and corrosion resistance.However,some studies have shown that polyethylene wear is one of the main reasons for failure of artificial joint prostheses.Clinically,more than 90% of UHMWPE artificial hip and knee joints can survive normally for 15-20 years,but the wear debris generated by polyethylene wear can cause aseptic loosening and osteolysis,which limits the longer life of joint replacement.In total hip arthroplasty,multidirectional motion or "cross-shear" motion is thought to be a key contributor to the wear rate of UHMWPE.The pin-disk wear test can not only qualitatively study the wear properties of UHMWPE,but also quantitatively simulate the cross-shear effect of UHMWPE wear,providing parameters for computer simulation of polyethylene artificial joint wear.In this study,conventional uncrosslinked UHMWPE and Co Cr Mo alloy disks were used as paired samples.Under the physiological lubricating conditions of calf serum with a volume fraction of 25%,the Rtec pin-on-disc friction and wear tester was used to perform a 90°transverse shear wear test to observe the microstructure of the sample surface and analyze the wear mechanism.The amount of wear of polyethylene was measured by a gravimetric method,and the functional relationship between the amount of wear and the transverse shear variable was determined by a numerical method.The results show that the wear rate of polyethylene pins is greatest at the beginning of a 90°rotation and gradually decreases and tends to remain constant with increasing sliding distance;under the same cycle conditions,the wear rate of polyethylene will increase with the increase of cross shear distance increase,but the increase range is small,and the wear amount has an obvious nonlinear relationship with the sliding distance;After cross shear wear of UHMWPE,particle and strip-shaped wear debris were generated on the surface,and cracks were generated at the same time,mainly in the form of adhesion and fatigue wear.Through the pin-disk wear test,the quantitative analysis and research of UHMWPE cross shear wear under the condition of simulated polyethylene artificial joint motion/load condition are realized.At the same time,the microscopic analysis of the wear surface reveals the generation mechanism of UHMWPE cross shear wear.The modeling research of computer simulation simulation of total joint wear provides theoretical basis and input parameters of wear model.