SYMPOSIA PAPER Published: 01 May 2013

Denatured Protein Deposits Identified on Simulator and Explant Hip Bearings


Simulator and explant studies have noted contamination of protein films on hip bearings. These films have been suggested to play a role in lubrication and wear mechanisms as both (i) a tribolayer and (ii) a confounding contaminant. It has been suggested that these films composed of protein might be responsible for cyclic weight fluctuations (0.2 to 2 mg) that can obscure gravimetric wear measurements. The aim of this work was to study protein films on simulator and explant hip bearings and develop a method for removing these protein films. Four types of bearings from simulators and explants (metal-on-metal [M-M], ceramic-on-ceramic [C-C], metal-on-polyethylene [M-PE], and ceramic-on-polyethylene [C-PE]) were examined for protein films. The topographies of protein films were characterized via interferometry and scanning electron microscopy. C-C bearings were washed with both acid and chemical solutions and M-M bearings were washed only with chemical solution and the topographies were analyzed. All bearing types were contaminated with protein films. The films were characterized as a thin adsorbed monolayer and clustered gelatinous “islands” predominantly located along the edge of the main wear zone. They were confirmed by their characteristic roughness and third-body wear tracks transitioning through the raised islands. Acid wash treatment on ceramics revealed a weight loss of up to 2 mg, whereas the chemical wash treatment yielded a weight loss that was 10 times less. The chemical wash successfully removed 1.8 mg of protein from the M-M simulator bearings. The accumulation of protein varied, with M-M and C-C ≫ M-PE and C-PE. The protein film topography on explanted bearings confirmed that protein films occur in vivo. The weight loss achieved through the wash treatments confirmed the removal of protein layers.

Author Information

Burgett, M.
Donaldson Arthritis Research Foundation, Colton, CA, US
Donaldson, T.
Donaldson Arthritis Research Foundation, Colton, CA, US
Clarke, I., C.
Donaldson Arthritis Research Foundation, Colton, CA, US
Savisaar, C.
CDRH/FDA, Silver Spring, MD, US
Bowsher, J.
CDRH/FDA, Silver Spring, MD, US
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Developed by Committee: F04
Pages: 1–13
DOI: 10.1520/STP156020120047
ISBN-EB: 978-0-8031-7572-3
ISBN-13: 978-0-8031-7546-4