In silico total hip replacement wear testing in the framework of ISO 14242-3 accounting for mixed elasto-hydrodynamic lubrication effects

Abstract

Currently, preclinical wear tests for total hip replacements is carried out by using mechanical simulators under a simplified normal gait cycle as recommended by the international guidelines ISO-14242. Nevertheless, the wear tests have a long duration and are expensive so that the aim of this paper was to propose a novel in silico approach for wear calculation in lubricated total hip replacements.The proposed in silico simulation is based on the accurate modelling of the tribological phenomena acting in the joint during certain kinematical and dynamical conditions under non-Newtonian unsteady mixed elasto-hydrodynamic lubrication conditions (MEHL). The analyzed hip joint is modeled as soft polymeric acetabular cup, PE GUR1020 (EtO), against hard metallic CoCrMo femoral head. The calculation of the fluid film pressure field within the joint gap is achieved during the in silico simulations by imposing the ISO 14242-3 kinematics and dynamics, to evaluate the cumulated wear volume over a single gait cycle by using a modified Archard’s model.The main purpose of this study is to propose an in-silico wear calculation approach reproducing the classical in vitro wear testing of total hip replacements accounting for unsteady synovial lubrication effects between the femoral head and the acetabular cup. The predicted wear, extrapolated from a novel proposed approach based on the wear slopes, was compared with the value from in vitro simulations showing a satisfactory agreement, allowing the authors to conclude that the proposed model is suitable to be used as in silico hip joint wear simulator.