In Silico Mixed Lubrication Model to Evaluate the Radial Clearance Influence on the Tribology of Total Hip Replacement

In biomechanics and biotribology the attention of scientific community is actually paid to the tribological optimization of the design parameters of prosthetic implants, devoted to the substitution of an unhealthy synovial articulation: a tribological characterization of the artificial joint is needed in order to guarantee minimum wear and maximum duration. The aim of this manuscript is to show the results about the development of a tribological model of the artificial hip joint made of Ultra High Molecular Weight PolyEthylene acetabular cup against ceramic femoral head: the model is supplied with the hip loading and relative motion coming from a multibody model developed by the authors in another work and it is used to analyze the response of several tribological quantities with respect to a variation of the implant radial clearance. The algorithm, written in Matlab computational environment, is based on the Reynolds equation adapted to the mixed lubrication mode: the results provided expected trends in terms of fluid/contact pressure, surfaces’ separation, wear penetration depth, etc. which could result in maps able to be used to find an optimal geometrical configuration of the implant dedicated to the framework of the customized subject-specific prostheses.