Ultra-High Molecular Weight Polyethylene Wear Particle Effects on Bioactivity

Published

September 1, 2003

Author(s)

H. W. Fang, Stephen M. Hsu, J V. Sengers

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) wear particles have been recognized as one of the major causes of aseptic loosening in total joint replacements. Macrophage phagocytosis of wear particles induces human biological/physiological responses which eventually lead to bone resorption and Osteolysis. However, the dependence of these reactions on the size and shape of the particles has not been elucidated and is not understood. The goal of this study is to develop a technique for producing UHMWPE particles with specified sizes and shapes so as to be able to study the effects of different UHMWPE particles on bioactivity. We applied surface texturing techniques to generate UHMWPE particles and air pouch animal tests to study the biological responses induced by UHMWPE particles.The study describes a procedure for generating narrowly distributed UHMWPE particles with controlled size and shape through surface texturing by microfabrication. The textured surface is used to rub against the polymer pins to produce wear particles in water. The surface texture produces narrowly distributed elongated particles or equiaxed particles by design. Experimental results show that the cutting-edge length of the surface features is proportional to the particle length. A larger penetration depth, larger normal load, and smaller sliding speed lead to a smaller aspect ratio of the particle. With this technique, we have been able to generate UHMWPE wear particles with different size and shape within phagocytosable and non-phagocytosbale ranges for biological response studies.A mathematical model to predict the dimensions of generated UHMWPE particles has been developed. A correlation model based on the empirical results is also presented. The models can be used to design the dimensions of the surface textures and the operating conditions of the wear tests for generation of the particle population with specified size and shape.Murine air pouch animal tests have been used to test the biological responses induced by UHMWPE particles. The results indicated elongated particles induced stronger immunological responses than round-like particles. UHMWPE particles that can be phagocytosed by the macrophage cells stimulated a higher bioactivity than the non-phagocytosable particles. This paves the way for future material development and textural designs that can minimize the most toxic wear particle generation, hence prolong the life of othopaedic joint replacements.

Citation

Special Publication (NIST SP) - 1002

Report Number

1002

NIST Pub Series

Special Publication (NIST SP)

Pub Type

NIST Pubs

Keywords

bioactivity, mechanism, modeling, osteolysis, phagocytosis, surface texture, UHMWPE, wear particle

Citation

Fang, H. , Hsu, S. and Sengers, J. (2003), Ultra-High Molecular Weight Polyethylene Wear Particle Effects on Bioactivity, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD (Accessed April 27, 2024)