Abstract: Wear of artificial hip joint bearing surfaces using ultra-high molecular weight polyethylene (UHMWPE) as material remains a major factor that affects the long-term performance of replacement joints. The computational wear modeling of hip joint bearings is an effective preclinical evaluation method that complements hip joint simulators for wear testing. The cross-shear effect resulting from multi-directional motion is one of the key factors that affect UHMWPE wear and critical to wear simulation modeling. The existing theoretical method quantifies the wear depth as a function of sliding distance and calculates the cross-shear effect of different angles based on the wear as a metric determined under the 90° cross-shear motion. However, the effect of contact stress variable on wear depth has been neglected. In these cases, a method of considering wear depth as a function of frictional work under the condition of 90° cross-shear motion is proposed. Taking account of the quantitative relationship between the friction coefficients and contact pressures of UHMWPE, the friction coefficients can be calculated and subsequently the frictional work. The method resolves the problem of coupling of sliding distance and contact stress in calculating cross-shear effect on UHMWPE wear. The wear of 36mm diameter cross-linked UHMWPE hip joint is computationally simulated based on the new wear model, and validated against the results of ProSim simulators previously published. The results show that the wear simulation model can be used to calculate volumetric wear rates and linear wear depths, and the effect of varied loading directions of artificial hip joint with marked accuracy. The new wear model has laid a solid foundation for further computational simulation.

Key words: ultra-high molecular weight polyethylene wear, artificial hip joint, crosslink