Lubrication mechanisms in metal-on-metal hip joint replacements

The results of a study which adopted the elastohydrodynamic lubrication theory show that the radial clearance between the femoral head and the acetabular socket, and the surface roughness of the metallic surface are very important in determining the magnitude of the minimum lubricating film thickness in metal-on-metal hip joint replacements. Once the radial clearance falls below 50 μm, the ratio of the predicted lubricating film thickness to the combined surface roughness of the metallic bearing surfaces becomes three times larger. Fluid film lubrication can be achieved in metal-on-metal hip joint replacements under simulated walking. Contact mechanics and lubrication mechanisms are very important in the design of such replacements.