Changes in the contact area during the bedding-in wear of different sizes of metal on metal hip prostheses.

Abstract

In metal on metal hip prostheses, the contact mechanics can influence the lubrication and wear rate. In particular, during the bedding-in wear, the contact area gradually increases to an optimal value, and the wear rate reduces as the contact stress reduces and the lubrication conditions improve. Geometrical designs that reduce the volume of bedding-in wear as the optimal contact area develops are preferable. The objective of this study was to analyse the wear volume as a function of contact area during the bedding-in period, with the aim of identifying geometrical design configurations that give lower bedding-in wear. As the radial clearance was reduced, the bedding-in wear volume to reach an optimal contact area also reduced. For a fixed radial clearance, increasing the head diameter also reduced the bedding-in wear volume.