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TECHNICAL BRIEFS

# Bio-Ferrography to Capture and Separate Polyethylene Wear Debris from Hip Simulator Fluid and Compared with Conventional Filter Method

[+] Author and Article Information
Donna M. Meyer1

Tribology and Fluid Mechanics Laboratory Department of Mechanical Engineering and Applied Mechanics University of Rhode Island Kingston, RI 02881dmmeyer@egr.uri.edu

Adam Tillinghast, Nevan C. Hanumara, Ana Franco

Tribology and Fluid Mechanics Laboratory Department of Mechanical Engineering and Applied Mechanics University of Rhode Island Kingston, RI 02881

1

Corresponding author.

J. Tribol 128(2), 436-441 (Nov 04, 2005) (6 pages) doi:10.1115/1.2162554 History: Received May 07, 2004; Revised November 04, 2005

## Abstract

This paper describes an experimental method, bio-ferrography, to separate ultrahigh molecular weight polyethylene (UHMWPE) wear debris, generated in hip simulators, from bovine serum lubricating fluid. A total of 54 experiments were performed in which an enzyme digestion “cocktail” was developed and used to clean the bovine serum samples of extraneous sugars, proteins, and lipids that interfere with the UHMWPE particle separation. Erbium chloride was used to marginally magnetize particles in the fluid prior to passing through the ferrographic device. The particles were captured and separated from the fluid by traversing the treated serum across a magnetic gap of a bio-ferrograph. Morphology of the captured and separated wear debris was compared with particles from samples of fluid filtered through a paper sieve arrangement with pores of $0.05micrometers$ in diameter. The UHMWPE wear debris collected using the described experimental method, were found to be between 0.1 and $20micrometers$ in diameter with spherical and pill-shaped particles. The filtered UHMWPE particles were in the same size range as the debris separated using bio-ferrography. To show that the experimental method captured UHMWPE particles, the spectra of the chemical composition of UHMWPE from an acetabular cup insert of a hip implant and of UHMWPE particles separated using bio-ferrography were compared and found to be the same. To further demonstrate that polyethylene could be captured and separated through the experimental method, manufactured polyethylene microspheres in the diameter range of $3–45micrometers$, were captured and separated using the bio-ferrographic process.

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## Figures

Figure 1

Conventional UHMWPE-on-CoCr total hip replacement (image created by A. Tillinghast)

Figure 2

Cross-sectional view of deposition cassette on magnetic gap

Figure 3

Scanning electron microscope (SEM) images of UHMWPE Wear Particulates Captured using bio-ferrography. Agglomerated and separated, spherical and pill-shaped, UHMWPE debris

Figure 4

(a) 1to2μm spherical UHMWPE particles surrounded by sub-micron pill-shaped UHMWPE particles. (b) Large fibril mass surrounded by spherical UHMWPE particles in the size range of 0.1–2μm

Figure 5

Spectra generated in the SEM of the elemental analysis of a piece of UHMWPE cut from the lining of a hip prosthesis compared with UHMWPE wear particle captured using bio-ferrography

Figure 6

SEM images of spherical UHMWPE wear particulates on 0.05μm filter paper captured using conventional filter method, approximately 0.5–3μm in diameter on filter paper

Figure 7

SEM images of manufactured polyethylene microspheres (approx. 1–50μm in diameter) captured using bio-ferrography

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