Meng Q E, Liu F, Fisher J, Jin Z M
Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK.
Proc Inst Mech Eng H. 2011 Jan;225(1):25-37. doi: 10.1243/09544119JEIM795.
Effective lubrication performance of metal-on-metal hip implants only requires 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 using non-spherical bearing surfaces for either acetabular or femoral components. An elastohydrodynamic lubrication model of a novel metal-on-metal hip prosthesis using a non-spherical femoral bearing surface against a spherical cup was solved under loading and motion conditions specified by ISO standard. A full numerical methodology of considering the geometric variation in the rotating non-spherical head in elastohydrodynamic lubrication solution was presented, which is applicable to all non-spherical head designs. The lubrication performance of a hip prosthesis using a specific non-spherical femoral head, Alpharabola, was analysed and compared with those of spherical bearing surfaces and a non-spherical Alpharabola cup investigated in previous studies. The sensitivity of the lubrication performance to the anteversion angle of the Alpharabola head was also investigated. Results showed that the non-spherical head introduced a large squeeze-film action and also led to a large variation in clearance within the loaded area. With the same equatorial clearance, the lubrication performance of the metal-on-metal hip prosthesis using an Alpharabola head was better than that of the conventional spherical bearings but worse than that of the metal-on-metal hip prosthesis using an Alpharabola cup. The reduction in the lubrication performance caused by the initial anteversion angle of the non-spherical head was small, compared with the improvement resulted from the non-spherical geometry.
金属对金属髋关节植入物的有效润滑性能仅要求在主要受力区域内具有最佳贴合度，而增加赤道区域的间隙则是有利的。通过对髋臼或股骨部件使用非球形轴承表面可以实现这种变化的间隙。在ISO标准规定的加载和运动条件下，求解了一种新型金属对金属髋关节假体的弹流润滑模型，该假体使用非球形股骨轴承表面与球形杯相对。提出了一种在弹流润滑求解中考虑旋转非球形头部几何变化的完整数值方法，该方法适用于所有非球形头部设计。分析了使用特定非球形股骨头Alpharabola的髋关节假体的润滑性能，并与先前研究中研究的球形轴承表面和非球形Alpharabola杯的润滑性能进行了比较。还研究了润滑性能对Alpharabola头部前倾角的敏感性。结果表明，非球形头部引入了较大的挤压膜作用，并且还导致加载区域内间隙的较大变化。在相同的赤道间隙下，使用Alpharabola头部的金属对金属髋关节假体的润滑性能优于传统球形轴承，但劣于使用Alpharabola杯的金属对金属髋关节假体。与非球形几何形状带来的改善相比，非球形头部初始前倾角导致的润滑性能下降较小。
