PE–UHMW人工颈椎间盘体内与体外工况摩擦学对比

Tribological Comparison of PE–UHMW Artificial Cervical Intervertebral Disc under In Vivo and In Vitro Conditions

为探究“金属–超高分子量聚乙烯”颈椎间盘假体在体内(头部前–后屈伸运动)和体外ISO 18192–1(2014)工况下的摩擦学性能。采用Hamrock&Dowson最小膜厚公式,进行润滑对比分析。基于“Archard双因素磨损方程”定量预测PE–UHMW假体的磨粒与黏着磨损情况。结果表明,不同工况下膜厚比λ值始终低于1,说明主要润滑类型为边界润滑,表面微凸体直接接触不可避免。根据500万循环PE–UHMW假体的磨损体积变化趋势,可知体内磨损率比体外磨损率小一个数量级,并在100万循环(Mc)后趋于稳定。三种工况下,ISO标准条件体外工况的体积磨损率最高,为0.822 mm3/Mc;三种工况相对应的质量磨损率分别为ISO标准条件0.768 mg/Mc、ISO替代条件0.607 mg/Mc和体内工况0.025 mg/Mc。后续,还需要进行深入的实验对比研究,系统化地探究不同头部运动类型对体内磨损的影响规律。

The tribological properties of metal and ultra-high molecular weight polyethylene(PE–UHMW)based cervical intervertebral disc prosthesis(TDA)were investigated under in vivo(head flexion-extension movement)and in vitro[ISO 18192–1(2014)]conditions.Analytical lubrication regime analysis was conducted by adopting Hamrock&Dowson minimum film thickness equation.Numerical wear simulation was performed using the cross-shear dependent Archard wear equation.Abrasion and adhesion wear of PE–UHMW TDA was then quantitatively predicted for five million cycles.The results show that membrane thickness percentageλvalue is always below unity,disregard the different working conditions.This may indicate that boundary lubrication is dominate and surface asperities contact is likely.According to the volumetric change of PE–UHMW TDA,the in vivo wear rate was one order of magnitude lower than that of in vitro,and volumetric loss ratio tended to be stable after 1 million cycles.Among the adopted three testing conditions,ISO-standard condition results in the highest volume wear rate of 0.822 mm3/million cycles.Meanwhile,the gravimetric wear loss of ISO-standard,ISO-alternative and head flexion-extension are 0.768,0.607,0.025 mg/million cycles,respectively.In the future,it is necessary to carry out in-depth experimental comparative study,and to systematically study the influence of different head movement types on the in vivo wear of PE–UHMW TDA.