Polyvinyl Siloxane Molds for Nondestructive Surface Feature Metrology of Failed Joint Prostheses

Abstract

A nondestructive polyvinyl siloxane (PVS) impression protocol was developed for studying the surface features on joint prostheses with modular junctions after they have been removed from patients. Analysis of the failed joint prostheses reveals that modular junctions consisting of bore-cone tapers can be the site of in vivo fretting and crevice corrosion. While cone taper surfaces are readily analyzed by non-contact profilometric techniques, bore taper surfaces are inaccessible for direct observation. An indirect repeatable method to analyze these inaccessible surfaces was developed, incorporating a commonly used dental impression polymer to achieve a high-detail negative of the bore taper suitable for profilometric measurements. Compared to the actual bore surface, light-viscosity PVS adequately replicated surface features for statistically similar measurements of metrological mean roughness parameters (Sa, Sq), peak-to-valley height parameters (Sz), shape parameters (Ssk, Sku), and spatial parameters (Sm). Surface features as fine as 2.6 μm in size were reproduced, indicating that this technique is applicable to failure analysis studies involving abrasive wear, adhesive wear, and corrosion pits. This indirect and nondestructive method of surface damage analysis can be broadly applied in many industries requiring analysis of inaccessible surfaces, such as machined bores, inner surfaces of pipes, and large parts incompatible with laboratory metrology equipment.