Wear Analysis of Extracted Polyethylene Acetabular Cups Using a 3D Optical Scanner

ABSTRACT

Wear analysis of total hip replacements (THRs) is considered one of the most relevant research areas helping to improve the longevity and overall design of THRs. The coordinate machine method (CMM) and Fourier profilometry are the most common methods for measuring THR wear. This article presents optical scanner digitalization as a new method for measuring the wear of polyethylene (PE) acetabular cups. The aim of this article is to explore the potential of this method for the PE wear measurements. Optical scans for the purposes of this study were produced using an ATOS Triple Scan 3D optical scanner. The optical scanner is efficient and it can measure a large number of points for polygonization and for further development of the preworn models. In this study, the scanner first generated point clouds on a sample of 13 retrieved ultra-high-molecular-weight polyethylene (UHMWPE) acetabular cups. Next, volumetric models of the cups were created by polygonizing the point clouds. Reverse engineering was used to develop models of the original acetabular cups using the geometry of the unworn parts of the retrieved cups. A comparison of the two models then showed the total volume of the PE debris. The optical scanning method was validated against the gravimetric method using three new acetabular cups that were worn out on a hip pendulum simulator. Validation shows that the optical scanning method is a valid method for wear analysis of the retrieved UHMWPE acetabular cups.

KEYWORDS:

• Total hip replacement
• polyethylene
• wear measurement
• optical digitalization
• volumetric wear

Acknowledgements

The authors thank A. Přikryl for optical scanning of acetabular cups and V. Trulíková for help with editing the article.

Funding

This research was carried out under the project NETME CENTRE PLUS (LO1202) with financial support from the Ministry of Education, Youth and Sports under the National Sustainability Programme I. This research was also supported by the project “The Influence of Joint Fluid Composition on Formation of Lubricating Film in THA” (NT/14267-3/2013) financed by the Internal Grant Agency of the Ministry of Health of the Czech Republic.