Publications & Reports

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4th UHMWPE International Meeting Presentation: Lanthanides as Stabilizers for UHMWPE

Researchers from Rush University Medical Center have successfully tested europium (Eu), a representative element from the lanthanide group, as a stabilizer to reduce oxidation of UHMWPE while preserving mechanical integrity. In this study, they hypothesized that the addition of Eu(II), would prevent oxidation of molded polyethylene components. Doping with europium-stearate was shown once more to reduce oxidation and prevent the mechanical degradation that has been observed in conventional polyethylene

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4th UHMWPE International Meeting Presentation: Influence of PE Structure on the Reactivity of Free Radicals

Researchers from the University of Torino have investigated the influence of polyethylene morphology on the evolution of the radiation-induced oxidation process. Researchers also attempted to determine in which phase the radicals produced by irradiation remain. E-beam was used for irradiation, being a fast method to produce radicals. The macroradicals detected after the irradiation process at room temperature, both with e-beam and gamma-rays, are those in the crystalline/all-trans phases. The migration rate of the macro-alkyl radicals from the crystalline/all-trans phase to the amorphous one defined the oxidation level and the time to reach the maximum of oxidation during the post-irradiation period.

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4th UHMWPE International Meeting Poster: Effect of the Consolidation Process on Properties of UHMWPE

In this study the influence of compression molding and ram extrusion on structural parameters and micro-mechanical properties of non-crosslinked, orthopaedic grade GUR 1050 UHMWPE was investigated. Lamellar thickness distribution (LTD) provided insight into the manufacturing and consolidation process of UHMWPE. The consolidation process resulted in different oxidative degradation states within the same material.

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4th UHMWPE International Meeting Presentation: The Biological Response to Nanometer-Sized Particles

This invited lecture by Prof. Joanne Tipper summarizes recent research at the University of Leeds on the biological response to nanometer-sized wear particles. Nanoscale particles are too small to be taken up by macrophages by the active process of phagocytosis and will be more likely to be taken up by non-active processes such as macropinocytosis. Consequently it was expected that nanoparticles would not stimulate an inflammatory cytokine response from macrophages. Contrary to expectation, nanometre-sized particles were found to have the potential to provoke inflammatory cytokine release from macrophages. There was a lower particle size limit, with the 20 nm FluoSpheres showing the lowest activity.

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4th UHMWPE International Meeting Presentation: Should Crosslinked UHMWPE be used in TKA?

This invited lecture by Dr. Anuj Bellare covers the risks and benefits of crosslinked UHMWPE for total knee joint applications. Wear resistance, oxidation resistance, and mechanical behavior are three major factors influencing the clinical performance of UHMWPE in the knee. Concerns have been raised about decreased mechanical properties of 1st-generation crosslinked UHMWPE. Stabilized XPEs that avoid thermal treatment but preserve oxidation resistance may be preferable for TKA.

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4th UHMWPE International Meeting Presentation: Oxidation and Stabilisation of Polyethylene

This invited lecture by Prof. Norman Billingham reviews the chemical reactions associated with oxidation of polyethylene and methods for stabilization. Polyethylene gets its mechanical properties from the combination of long chain length and semi-crystalline morphology. Chemically insignificant amounts of oxidative degradation affect mechanical properties profoundly by cleaving the important "tie molecules." Antioxidants are added to essentially all PE products to inhibit oxidation during processing and end use. Most commercial antioxidants would be excluded from use in medical devices due to potential migration and toxicity. Vitamin E has potential for medical applications.

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4th UHMWPE International Meeting Presentation: Vitamin E Stabilization of Radiation Cross‐linked UHMWPE by Diffusion

This invited lecture by Dr. Ebru Oral covers post‐irradiation diffusion stabilization of UHMWPE to avoid the hindrance of vitamin E in cross‐linking UHMWPE. Diffusion was achieved by using high temperature doping followed by high temperature homogenization without dimensional stability changes and with fine control of the amount of antioxidant. Vitamin E‐diffused, irradiated UHMWPE showed lower wear compared to conventional UHMWPE and fatigue resistance higher than irradiated and melted UHMWPE. Vitamin E does not appear to have detrimental effects on peri‐prosthetic tissue in animal studies.

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Oxidation of Electron-Beam Irradiated UHMWPE Stabilized With Vitamin E

In the present work, medical grade UHMWPE was blended with 1.1, 2.3 and 11 mmol/l of vitamin E and consolidated by compression moulding. Small blocks of reference and of vitamin E-blended UHMWPE were then electron-beam irradiated at 30, 60 and 90 kGy, both in vacuum and in air. The reaction between vitamin E and macro-alkyl radicals or unlikely with peroxy radicals has been demonstrated and a correlation between the decrease of macroradicals and the stabilization effect of vitamin E has been shown.

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Alternative Bearing Surface Usage in Total Hip Arthroplasty in the United States

The specific indications for the use of alternative bearings remain controversial. The purpose of this study was to characterize the epidemiology of bearing surface utilization in total hip arthroplasty in the United States with respect to patient, hospital, geographic, and payer characteristics. The most commonly reported bearing was metal-on-polyethylene (51%) followed by metal-on-metal (35%) and ceramic-on-ceramic (14%). The usage of total hip arthroplasty bearings varies considerably by patient characteristics, hospital type, and geographic location throughout the United States. Despite uncertain advantages in older patients, hard-on-hard bearings are commonly used in patients over the age of sixty-five years.

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2009 Society for Biomaterials Tutorial: Advances in UHMWPE

This SFB tutorial reviews historical, conventional and highly crosslinked polyethylene used in total hip and knee replacement. We begin with an overview of the basic science concepts and terminology related to polyethylene and the two main thermal processing techniques with 1st generation materials, which involve either annealing or remelting the polymer after irradiative crosslinking. The second part of the review is a summary of key findings and concepts from the peer-reviewed literature on the subject of vitamin E stabilization of UHMWPE. 2nd generation highly crosslinked UHWMPE and future directions in UHMWPE research are also briefly reviewed.

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