Publications & Reports

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Mechanical Properties, Oxidation, and Clinical Performance of Retrieved Highly Crosslinked Crossfire Liners after Intermediate-Term Implantation

Researchers from Drexel University have evaluated 60 Crossfire liners implanted after an average of 2.9 years (range: 0.01 – 8.0 years) for reasons unrelated to wear or mechanical performance of the polyethylene. Elevated oxidation was measured on the rim that correlated with implantation time. Rim surface damage, however, was observed in only 3/60 (5%) cases. Retrieval analysis of the three rim-damaged liners did not reveal an association between surface damage and the reasons for revision.

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PhD Dissertation: Static and Cyclic Behavior of Crosslinked UHMWPE in the Presence of Mild Stress Risers

This Ph.D. Dissertation by Michael Sobieraj from the Case Western Reserve University describes the static and fatigue behavior of annealed and remelted highly crosslinked UHMWPE under smooth and notched conditions. Crosslinked formulations of GUR 1050 were investigated. Monotonic stress-strain behavior in the presence of a notch was examined using a custom developed video based system, under physiologically relevant conditions. The fatigue behavior was also investigated using a total life approach to fatigue.

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2009 ORS Poster: Evaluation of Sub-Micron PE Wear Debris by Enhanced Polarized Light Microscopy

Major limiting factors for polarized imaging (and most optical systems) of wear debris is a lack of automation for capturing entire tissue sections in both brightfield and polarized modes, and the diffraction (Rayleigh) limit which limits imaging of small particles (e.g. <1 μm). The purpose of this study was to adapt a new elliptically polarized light imaging system (EPLIS) to in situ analysis of PE particles. The EPLIS system uses novel 3-D deconvolution to achieve “superresolution” allowing particles smaller than 1 μm to be analyzed. Validation of particles sizes was made by comparing with environmental scanning electron microscope (ESEM) images of the same particles.

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2009 ORS Poster: Histomorphologic Characteristics of Periprosthetic Tissue from Crosslinked PE Hip Implants

The objective of this study was to evaluate the histomorphologic changes of periprosthetic tissue in relationship to areas of the tissue with PE wear debris. To accomplish this objective, a duel image analysis was done on H&E stained sections to determine histomorphologic changes and inflammation by brightfield microscopy, and to evaluate PE debris size and distribution by polarized light microscopy. The hypothesis was that the size and volume of wear debris, and thus the histomorphologic changes in the tissue, would be more extensive for patients with historical gamma-air sterilized PE components as compared to the newer gamma-inert sterilized, highly crosslinked PE components.

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2009 ORS Poster: Correlation Between In Vivo Oxidation and Mechanical Behavior of UHMWPE

The objective of this study was to employ ASTM techniques to examine the correlation between in vivo oxidation levels and mechanical properties at the articular surface of retrieved contemporary acetabular liners and tibial inserts. The influence of oxidation and mechanical properties on wear performance and surface damage was also explored.

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2009 AAOS Scientific Exhibit: Revisiting The Long-Term Clinical Performance of Poly II

Carbon fiber reinforced ultra-high molecular weight polyethylene (Poly II) was clinically introduced in the 1970s, but catastrophic short-term outcomes were reported in case studies. The aim of this study was to revisit the clinical, surface damage, and oxidative performance of Poly II tibial inserts. Researchers found that the long-term clinical survivability and material performance of Poly II tibial bearings of both CR and PS designs was comparable to historical polyethylene.

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Vitamin E-Blended UHMWPE Resin Announcement

Ticona has announced the commercial release of GUR 1020-E and GUR 1050-E UHMWPE resin materials. These new resin grades are blended with 1,000 ppm alpha-tocopherol. Ticona has also released technical specifications for these new resin materials.

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2009 ORS Podium Presentation: First-Generation Highly Crosslinked Polyethylenes in THA

In this study, we evaluated the clinical outcomes, as well as the material performance of contemporary HXLPEs formulations. We hypothesized that HXLPE would exhibit lower incidence of loosening and polyethylene wear as reasons for revision, and low femoral penetration rates. Furthermore, in vivo oxidation, if any, was hypothesized to not have clinical consequences for patients implanted with HXLPE acetabular liners.

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2009 ORS Poster: A Standardized Method For Extraction of Lipids and Measuring Oxidation with Retrieved UHMWPE

The objective of the present study was to develop a standard extraction method of polyethylene sections for further FTIR analysis. In addition, we examined the validity of the height ratio method for characterizing oxidation in polyethylene retrievals. Finally, the effects of different reagents and extraction conditions on polyethylene physical and chemical properties were also investigated.

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Hybrid Model for UHMWPE Now Available as Freeware Download

The hybrid model is a material model that was developed for ultra-high molecular weight polyethylene (UHMWPE) used in total joint replacements. Information about the development and use of the Hybrid model has appeared in the open literature. Exponent has released a free LS-DYNA3D user subroutine for the Hybrid Model on their website under a General Public License. This user subroutine is made available free of charge on the Exponent website for use by the orthopedic research community.

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