Analysis of fluid film lubrication in artificial hip joint replacements with surfaces of high elastic modulus

TLDR

Lubrication mechanisms and contact mechanics have been analyzed for hard‑bearing hip replacements, with a reference study on UHMWPE against hard surfaces. The authors aim to analyze the contact mechanics in artificial hip joint replacements. The study shows that radial clearance is the key determinant of lubricating film thickness, that full fluid‑film lubrication can be achieved with appropriate surface finish and clearance, that the contact half‑width correlates closely with film thickness, and that practical manufacturing considerations are also addressed.

Abstract

Lubrication mechanisms and contact mechanics have been analysed for total hip joint replacements made from hard bearing surfaces such as metal-on-metal and ceramic-on-ceramic. A similar analysis for ultra-high molecular weight polyethylene (UHMWPE) against a hard bearing surface has also been carried out and used as a reference. The most important factor influencing the predicted lubricating film thickness has been found to be the radial clearance between the ball and the socket. Full fluid film lubrication may be achieved in these hard/hard bearings provided that the surface finish of the bearing surface and the radial clearance are chosen correctly and maintained. Furthermore, there is a close relation between the predicted contact half width and the predicted lubricating film thickness. Therefore, it is important to analyse the contact mechanics in artificial hip joint replacements. Practical considerations of manufacturing these bearing surfaces have also been discussed.