交联超高分子量聚乙烯人工髋关节磨损仿真模拟

人工髋关节超高分子量聚乙烯（UHMWPE）关节面磨损仍是影响置换关节远期寿命的主要因素，其仿真建模是对关节模拟机磨损测试手段的重要补充，也是实现置换关节临床前性能评估的有效方法。由多向运动产生的交叉剪切效应是影响UHMWPE磨损的主要原因之一，也是仿真建模的关键。现有理论方法将磨损深度确定为滑动距离的函数，并将90°交叉剪切运动条件下的磨损作为度量基准计算不同角度下的交叉剪切效应，但尚未考虑接触应力变量对磨损深度的影响。针对以上问题，提出了在垂直交叉剪切运动条件下将磨损深度表示为摩擦功函数的方法。该方法利用UHMWPE摩擦因数与接触压力的定量关系计算摩擦因数并确定摩擦功，解决了UHMWPE磨损交叉剪切效应中滑动距离与接触应力的耦合问题。基于磨损仿真新模型研究了36 mm直径的交联UHMWPE髋关节，并与已有ProSim模拟机试验结果进行了验证。结果显示该仿真模型可准确计算体积磨损和线性磨损等磨损量以及髋关节载荷方向改变对磨损的影响。磨损新模型为进一步仿真模拟奠定了有效基础。

Computational Wear Simulation on Cross-linked Ultra-high Molecular Weight Polyethylene Artificial Hip Joints

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.