Abstract
Particulate debris created during a fiber-filled PEEK material (MOTISTM) rubbing on a ceramic femoral head in a hip wear simulation study was characterized. The particles were cleaved from the protein lubricant with a double enzymatic protocol and then sized using two different techniques. The sizes obtained were verified using an AFM imaging technique.
Many metal-on-UHMWPE joints ultimately fail due to late aseptic loosening. This occurs due to the particulate debris built up in the periprosthetic area. The body’s natural immunological response leads to bone resorption, the prosthesis becomes loose and severe pain can then necessitate revision. It is therefore important to characterize the wear particles of novel materials in order to understand their biological impact.
Particles were generated in a Durham hip wear simulator from a MOTISTM acetabular cup articulating against a ceramic femoral head for 25 million cycles1. The samples were generated in 500 ml of bovine serum lubricant (17 g/l protein) and a 10 ml sample of this lubricant was analyzed.
A double enzymatic protein cleavage protocol was used as it was shown to be the least harmful to the particles.
A bi-modal distribution of sizes was seen with a large number of particles of 100 nm and a large number at the two micron size range. AFM results verified the size of the particle distribution and also showed that the smaller particles were round to oval and the larger particles were long and thin. No carbon fibers were evident in the AFM images. Although the wear rate over the 25 million cycles1 remained low and linear, the average particle size tended to increase over the 25 million cycles whilst the volume of the particles decreases over the period.
Howling2 studied particle debris from a pin-on-plate carbon fiber reinforce PEEK against ceramic test using a 6M KOH protocol and resin embedded TEM analysis.
This method only allowed around 100 particles to be imaged at a time, no size distribution was given. Ctyotoxicity was also tested using U937 monocytic cells indicating that MOTISTM has no cytotoxic effects such as necrosis.
Correspondence should be addressed to Diane Przepiorski at ISTA, PO Box 6564, Auburn, CA 95604, USA. Phone: +1 916-454-9884; Fax: +1 916-454-9882; E-mail: ista@pacbell.net
References:
1 S.C. Scholes, I. A. Inman, A. Unsworth and E. Jones. ‘Tribological assessment of a flexible carbon-fibre-reinforced poly(ether-ether-ketone) acetabular cup articulating against an alumina femoral head’ Proc. IMechE Vol. 222 Part H: J. Engineering in Medicine. Google Scholar
2 G. I. Howling, et al. ‘Biological response to Wear Generated in Carbon Based composites as potential bearing surfaces for artificial hip joints’ Biomed. Mater. Res. Part B: Appl. Biomater. vol: 67B pp 758–764, (2003), Work Funded by Stryker Orthopaedics. Google Scholar
