Topographical characterisation of artificial femoral heads—a Benchmarking study

The main functional demands on artificial joints are that they last more than 20 years. This means optimising the friction coefficient to minimise forces transmitted to the surrounding bone and the wear of the contacting surfaces. Surface roughness has an important influence on friction and wear. Traditionally, the 2D Ra-parameter has been the preferred way to characterise the joint's topography. Today ongoing development of 3D techniques are available for the research, and the aim of the present paper is to highlight the importance and possibilities using high-resolution 3D atomic force microscope ( AFM) and the optical phase-shifting interferometer for texture characterisation of eight commercially available femoral heads. The results show a significant variation of topography and surface-lay for the different femoral heads in the study. The variation and difference between heads were further underlined by the use of different characterisation techniques and measuring strategy. Results highlight the importance of the selection of measurement strategy, parameters, instrumentation, and scale of measurement in order properly to characterise the femoral heads in this study.