Investigation into the effect of a sandwich acetabular cup upon lubricant film thickness in metal-on-metal total hip replacements

The development of a large lubricant film thickness generally depends upon the large elastic deformations of the bearing surfaces from the elastohydrodynamic lubrication (EHL) point of view. The deformation of the bearing surfaces of total hip joint replacements can be influenced by the material properties as well as the structural supports. A conceptual sandwich cup, which consists of a hemispherical metallic bearing shell bonded to a polyethylene backing, together with a solid metallic femoral head was considered in an EHL analysis for quasi-static conditions of load and speed to investigate the effect of the sandwich cup upon lubricant film mickness in total hip replacements. It was found that a reduction in the cup wall thickness of the metallic shell and an increase in the polyethylene thickness resulted in an increase in the predicted lubricant film thickness and a decrease in the hydrodynamic pressure. A general relationship was found between the film thickness and the metallic inlay thickness. JET149