ASTM International

Standard Guide for Characterization of Wear from the Articulating Surfaces in Retrieved Metal-on-Metal and other Hard-on-Hard Hip Prostheses
 N F2979

Annotation

This guide specifies a method to measure the in-vivo wear of explanted Metal-on-Metal (MoM) and other "hard" (e.g., ceramic) hip components. The guide covers the measurement of acetabular cups and femoral heads using a dimensional change method and is applicable to all prosthetic hip types, including stemmed (modular) and resurfacing hip systems.

The methods specified in this guide are not applicable for measuring the in-vivo wear from non-articulating surfaces, for example modular connections (at the stem/neck, neck/head or cup liner/shell interface) or at acetabular cup rim.

The parameters (wear depth and volumetric wear) evaluated and reported in this guide are estimated from the assumed as-manufactured shape of the components. The wear volume is calculated using a numerical integration method and the wear depth is the difference between the assumed asmanufactured shape and the measured surface.

This guide covers the measurement of the depth of wear and the volumetric wear using a Coordinate Measuring Machine (CMM) and the depth of wear using an Roundness Machine. Other metrology measurement equipment may be used to measure the wear depth or volume if the resolution and accuracy of the measurements are comparable with the instruments detailed in this standard. The measurement and analysis protocols should be based on those described in this standard.

This guide is applicable to hip joints which are nominally spherical at the time of manufacture. Form deviations resulting from manufacturing or deformation may occur and may necessitate the use of a non-spherical surface to represent the unworn surface of the component. Hip joints designed with asymmetry are considered beyond the scope of this guide, although the principles and techniques may be applicable to the characterization of wear from the articulating surfaces.