Computational Wear Simulation Of Ultra-high Molecular Weight Polyethylene Artificial Hip Joint

Metal-ultra-high-molecular-weight polyethylene(UHMWPE)hip joint with low friction and wear characteristics is the most widely used clinical hip prosthesis at present.However,UHMWPE wear can lead to periprosthetic osteolysis and aseptic loosening.The bearing wear is the main reason for the long-term failure of total hip replacement.Contact area,contact stress and cross shear are the main factors that affecting UHMWPE wear.Traditional UHMWPE hip implants often use large-diameter head design to improve joint stability and range of motion and reduce the risk of dislocation.But studies have shown that it accelerates wear rates due to the increased contact area of the bearing surface.The development of cross-linking technology has significantly reduced the wear rate of UHMWPE.But the effect of structural parameters of the cross-linked UHMWPE hip implant on UHMWPE liner wear behavior is not yet clear,and the wear performance needs to be further studied.Clinical research and wear testing are currently the main methods to study the wear performance of UHMWPE hip joints.But they are not suitable for extensive and long-term parametric studies on hip implants because of timeconsuming process and high economic cost.Computational simulation provides a low-cost and high-efficiency solution,which compensate the above-mentioned wear performance testing methods and contributes to the study of the wear mechanism of UHMWPE.This paper mainly includes the establishment,verification and application of the UHMWPE wear simulation model as follows:In this paper,the finite element contact mechanics model of metal-crosslinked UHMWPE hip implant is established using 3D modeling software Solidworks,finite element preprocessing and analysis software Hyper Mesh and Abaqus.Based on Fortran language,the UHMWPE hip wear simulation process is established.The theoretical UHMWPE wear model is verified against the results of the hip joint simulator wear test previously published.In this paper,based on the established UHMWPE hip wear simulation model,the influence of three geometric parameters including head size,UHMWPE cup thickness and bearing surface clearance on the wear of UHMWPE was studied respectively under standard gait conditions during the application phase of the computational wear simulation model.And a 20-year long-term equivalent wear prediction is carried out by the multi-layer node update method.The results show that for hip implants with head diamters of 28 mm,36 mm and 44 mm,the increase of head diameter leads to an increase in the contact area,and the wear volume of the cross-linked UHMWPE bearing surface increases significantly.It indicates cross-linking has not completely eliminated the adverse effects of large-head design.For implants with UHMWPE cup thicknesses of 4 mm,6 mm and 10 mm,cup thickness mainly affects the contact stress rather than contact area.Therefore,wear volume and wear depth did not change significantly,while creep volume and creep depth increased significantly with the increase of cup thickness.For the implants with bearing surface clearances of 0.5 mm and 0.1 mm,increasing the bearing surface clearance results in a decrease in contact area and an increase in contact stress,a decrease in wear volume and an increase in wear depth.The long-term volumetric wear rate is significantly increased compared to the corresponding results for 5million gait cycles.The above results show that the wear volume is positively correlated with contact area and negatively with contact stress.Wear depth is positively related to contact stress.Subsequent multi-parameter coupling analysis is required to obtain the optimal solution of geometric parameters combination.The UHMWPE hip wear simulation framework established in this paper can provide theoretical basis and method support for the design and optimization of UHMWPE hip implants.