一种使用非球面髋臼的金属-金属髋关节假体的时变弹流润滑分析

目的 金属－金属人工髋关节的高效润滑特性只需在主承载区上有适宜的匹配性，其优点是增加边缘区间隙。通过改变假体表面的曲率半径，得到变化的间隙。Alpharabola就是这种表面的具体结构之一。本文的研究目的是观察采用Alpharabola杯的新型假体在实际步态条件下的弹性流体动力润滑（EHL）性能。方法 建立新型髋关节假体的EHL模型，根据ISO规定的动载运动条件来表示人体步态。利用多重网格技术，求解球坐标系下的雷诺方程、膜厚方程和载荷平衡方程以获得完整数值解。结果 在一个收敛步态周期中，分析润滑膜轮廓和压力分布详细变化。观察参数?对中心膜厚、最小膜厚和中心压力的准稳态和非稳态解的影响，并比较相同?下非稳态解和准稳态解。在非稳态条件和准稳态条件下，比较Alpharabola髋关节假体和球形髋关节假体润滑性能。结论 结果发现，在实际步态条件下，挤压膜效应和非球形髋臼表面能显著提高润滑性能，即估计的润滑膜厚增加且最大流体压力减少。这说明金属－金属Alpharabola髋关节假体比球形髋关节假体能显著地增强流体润滑。关键词：非稳态弹性流体动力润滑；金属－金属髋关节假体；非球形支承表面；Alpharabola髋臼表面

Transient Elastohydrodynamic Lubrication Analysis of a Novel Metal-on-Metal Hip Prosthesis With an Aspherical Acetabular Bearing Surface

Objective The effective lubrication performance of the metal-on-metal hip implants only requires the optimum conformity within the main loaded area, while it is advantageous to increase the clearance in the equatorial region. Such a varying clearance can be achieved by changing the radius of the curvature of the surfaces of the components. Alpharabola is one specific example of such surfaces. The aim of this study was to investigate the EHL performance of a novel prosthesis employing Alpharabola cup under realistic walking conditions. Method A transient elastohydrodynamic lubrication model was created for this novel hip prosthesis. A normal walking gait was represented by the ISO specified dynamic operation conditions. Complete numerical solutions were obtained by solving the Reynolds equation in spherical coordinates, the film thickness equation and the load balance equations using Multi-grid technologies. Results Detailed variations in film profile and pressure distribution during one convergent walking cycle were analyzed. The effect of parameter ? on quasi-static and transient solutions of the central and minimum film thicknesses and maximum pressures was investigated. The transient and quasi-static solutions for the same parameter ? were compared. The lubrication performance of Alpharabola hip prostheses and that of a spherical hip prosthesis were compared under both transient and quasi-static conditions. Conclusion It was found that both the squeeze film action and the non-spherical acetabular surface can significantly improve lubrication performance under realistic walking conditions, in increasing the predicted lubricant film thickness and decreasing the maximum hydrodynamic pressure. The metal-on-metal Alpharabola hip prosthesis was shown to benefit from fluid film lubrication significantly more than spherical hip prostheses.