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      Charnley wear model for validation of hip simulators' ball diameter versus polytetrafluoroethylene and polyethylene wear

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          Abstract

          Wear rates of polytetrafluoroethylene (PTFE) and polyethylene cups were compared in 9-channel and 12-channel simulators, using serum lubrication and gravimetric techniques for wear assessment. Cobalt-chromium (CoCr) and alumina ceramic femoral heads in 22-42 mm diameter range were used to validate simulator wear rates against clinical data. This was also the first study of three femoral head sizes evaluated concurrently in a simulator (with three replicate specimens) and also the first report in which any wear experiments were repeated. Fluid absorption artefacts were within ± 1 per cent of wear magnitude for PTFE and ± 8 per cent for polyethylene and were corrected for. Wear rates were linear as a function of test duration. Precision within each set of three cups was within ±6 per cent. The wear rates from experiments repeated over 15 months were reproducible to within ± 24 per cent. However, the magnitudes of the simulator wear rates were not clinically accurate, the PTFE wear rates (2843 mm 3/10 6cycles; 22 mm diameter) were over three times higher than in vivo, the polyethylene 30 to 50 per cent on the low side (23 mm 3/10 6cycles; 22 mm diameter). Volumetric wear rate increased with respect to size of femoral head and a linearly increasing relationship of 7-8 per cent/mm was evident with respect to femoral head diameter for both PTFE and polyethylene. These data compared well with the clinical data.

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          Most cited references26

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          Effect of femoral head size on wear of the polyethylene acetabular component.

          A technique was developed to determine the wear of the acetabular component of a total hip replacement by examination of standardized initial and follow-up radiographs. Three hundred and eighty-five hips were followed for at least 9.5 years after replacement. The least amount and rate of linear wear were associated with use of a femoral head that had a diameter of twenty-eight millimeters (p less than 0.001). The greatest amount and mean rate of linear wear occurred with twenty-two-millimeter components, but these differences were not statistically significant. The greatest volumetric wear and mean rate rate of volumetric wear were seen with thirty-two-millimeter components (p less than 0.001). A wider radiolucent line in acetabular Zone 1 was associated with use of the thirty-two-millimeter head. The amounts of resorption of the proximal part of the femoral neck and of lysis of the proximal part of the femur both correlated positively with the extent of linear and volumetric wear; this suggests an association between the amount of debris from wear and these changes in the femoral neck and proximal part of the femur.
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            Isolation of predominantly submicron-sized UHMWPE wear particles from periprosthetic tissues.

            A method of tissue digestion using sodium hydroxide was applied to the isolation and recovery of ultra-high-molecular-weight polyethylene (UHMWPE) particles from tissues around failed total hip replacements. Density gradient ultracentrifugation of the digested tissues was performed to separate the UHMWPE from cell debris and other particulates. Fourier transform infrared spectroscopy and differential scanning calorimetry (DSC) verified that the recovered particles were UHMWPE. When viewed by scanning electron microscopy, individual particles were clearly observed and were either rounded or elongated. The majority were submicron in size. The application of this method to the study of particles from periprosthetic tissues may elucidate aspects of biomaterial particle size and shape that are important to the biologic response to, and clinical outcome of, total joint replacement.
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              Friction and wear properties of polymer, metal, and ceramic prosthetic joint materials evaluated on a multichannel screening device.

              A 12-channel wear screening device was used to compare the wear properties of a variety of prosthetic joint materials. Two types of tests were run: (1) Ultrahigh molecular weight (UHMW) polyethylene bearing against metal or ceramic counterfaces and (2) various polymers bearing against 316 stainless steel as a standard counterface. Wear was quantified by weighing the polymer specimens, with presoaking and control-soak specimens used to minimize the error due to fluid absorption. The specimens were lubricated with bovine blood serum. Friction and polyethylene wear was very low with each of the metals (316 stainless steel, cobalt-chrome alloy, multiphase alloy, and titanium 6-4 alloy) such that the differences in wear rate would not be significant in terms of choosing a material for clinical application. However, titanium 6-4 alloy was found to be especially susceptible to abrasive wear by particles of acrylic cement. Nitrided titanium 6-4 counterfaces were impervious to acrylic abrasion. Polyethylene wear against highly polished, fully dense ceramics (Sialon, Alumina, Macor, and pyrolytic graphite) was as low as that with the metal counterfaces. Wear increased slightly with increasing ceramic surface roughness. The coefficient of friction of polyethylene against pyrolytic graphite was two to three times higher than with the metals or other ceramics. All of the alternate polymers underwent more wear than UHMW polyethylene. Teflon and polyester, two polymers that have proven unsuccessful in prior clinical use, had wear rates 1,600 and 830 times greater than polyethylene, respectively, an indication that the laboratory wear test provided a quantitative prediction of the behavior of the materials in vivo. However, it was difficult to assess the clinical significance of the less extreme wear rates since the ability of the tissues encapsulating a prosthesis to accomodate wear debris is not known on a quantitative basis.
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                Author and article information

                Journal
                Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
                Proc Inst Mech Eng H
                SAGE Publications
                0954-4119
                2041-3033
                January 01 1997
                December 28 2005
                January 01 1997
                : 211
                : 1
                : 25-36
                Affiliations
                [1 ]Loma Linda University Medical Center Howard and Irene Peterson Tribology Laboratory Loma Linda, California, United States of America
                [2 ]Loma Linda University Medical Center Department of Orthopedics Loma Linda, California, United States of America
                Article
                10.1243/0954411971534656
                ae1a9d91-4307-4976-b67b-1d4d7f241857
                © 1997

                http://journals.sagepub.com/page/policies/text-and-data-mining-license

                History

                Biochemistry,Animal science & Zoology
                Biochemistry, Animal science & Zoology

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