Publications & Reports

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ORS 2013 Poster - Oxidative and Wear Properties of Sequentially Annealed Highly Crosslinked Polyethylene Used In TKA

The consecutive series of total knee replacements investigated the clinical revision reasons, damage mechanisms, and oxidative behavior of second generation highly crosslinked polyethylene. Second generation HXLPEs had similar properties to conventional gamma inert controls.

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ORS 2012 Poster - Impact of Large Diameter and Ceramic Femoral Heads on HXLPE Wear

The purpose of this multicenter retrieval study was to assess the wear behavior of HXLPEs in the context of polyethylene formulation, head size, and head bearing surface. Researchers from Drexel University evaluated whether (1) large diameter (32+ mm) heads would exhibit greater wear than smaller heads (28 mm or less); and (2) if ceramic bearing surfaces would decrease the wear of HXLPE liners.

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ORS 2012 Poster - Material Performance of 1st and 2nd Generation HXLPEs for THA

The purpose of this multicenter retrieval study was to assess the oxidative stability, mechanical behavior, wear and reasons for revision of 2nd generation HXLPEs and compare them to our ongoing retrieval collection of 1st generation annealed and remelted HXLPEs. Researchers hypothesized the sequentially annealed components would exhibit wear rates similar to 1st generation HXLPEs. It was also hypothesized that 2nd generation HXLPEs would be more oxidatively stable than 1st generation HXLPEs.

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ORS 2012 Poster - Material and Clinical Performance of Remelted HXLPE in TKA

Knowledge regarding the in vivo damage mechanisms and oxidative stability of remelted HXLPEs in the knee remains incomplete. Researchers from Drexel University hypothesized that due to the reduced free radicals, remelted HXLPE tibial inserts would have lower oxidation levels than gamma inert-sterilized controls.

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Latest Lessons Learned from Retrieval Analyses from UHMWPE and Alternative Bearing Total Disc Replacements

This review addresses the following four main questions: 1) What are the latest lessons learned from polyethylene in large joints and how are they relevant to current total disc replacements (TDRs)? 2) What are the latest lessons learned regarding adverse local tissue reactions from metal-on-metal, CoCr bearings in large joints and how are they relevant to current TDRs? 3) What advancements have been made in understanding the in vivo performance of alternative biomaterials, such as stainless steel and polycarbonate urethane, for TDRs in the past five years? 4) How has retrieval analysis of all these various artificial disc bearing technologies advanced the state of the art in preclinical testing of TDRs? The study of explanted artificial discs and their associated tissues can help inform bearing selection as well as the design of future generations of disc arthroplasty. 

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5th UHMWPE International Meeting Presentation: Oxidation Initiated by Cyclic Loading in the Presence of Lipids

By coupling the adverse effects of thermal aging with mechanical stress and lipid initiated oxidation, researchers from MGH in Boston sought to investigate if either irradiated and melted PE or vitamin E stabilized PE was prone to environmental stress cracking (ESC). The researchers hypothesized that the active protection of vitamin E was necessary to protect highly crosslinked PEs under such unfavorable conditions. Oxidation initiated by cyclic loading and by the presence of an unstable lipid can cause a loss of stability, even in materials containing no residual free radicals such as CISM-100. The active protection granted by antioxidants such as vitamin E may be necessary to combat oxidation in the long term in vivo.

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5th UHMWPE International Meeting Presentation: UHMWPE/Multiwall Carbon Nanotubes Composites

The aim of this work is to enhance the antioxidant capacity of carbon nanotubes and their ability to act as free radical scavengers in UHMWPE. EPR spectroscopy reveals that the presence of CNT has a significant influence in radical formation during the radiation treatment, being this effect more pronounced in the case of the allyl radical. CNTs reduced the oxidation index when the irradiated nanocomposite was subjected to accelerated aging. Both outcomes point out the capability of the nanotubes to act as free radical scavengers when the nanocomposite is irradiated.

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5th UHMWPE International Meeting Presentation: Evaluation of Oxidation in Virgin UHMWPE Knee Components after Retrieval and Shelf Aging

The primary purpose of this study was to determine if retrieved, virgin UHMWPE knee components are susceptible to either in-vivo or ex-vivo oxidation. Additional goals in this study included evaluations of (a) the distributions and qualitative amounts of lipids within the retrieved components, and (b) the relationship between the peak-height and peak-area oxidation indices. Esterified fatty acids (EFAs) were found at all of the surfaces examined with concentrations and penetration depths that appeared to be related to both mechanical loading and the exposure to synovial fluid. Evaluation of hexane extraction for both 16 and 32 hours demonstrated that all of the extractable species were successfully removed after 16 hours of extraction.

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5th UHMWPE International Meeting Presentation: Relationship Between in Vivo Stresses and Oxidation of UHMWPE

The aim of this study is to demonstrate that stress induced by the in vivo joint forces on EtO sterilised UHMWPE components is responsible of an increased oxidation of the material. The experimental data collected in this study indicate that, as expected, there is a correlation between the observed global wear and in vivo time, although anatomic conditions, patient activity and retrieval motivations could seriously affect the reproducibility of the phenomenon in such a differentiated sample outline.

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5th UHMWPE International Meeting Presentation: Impact of Aging Environment on the Oxidation of Vitamin E Blended UHMWPE

Researchers have investigated a new Vitamin E blended, highly crosslinked UHMWPE material in both standard accelerated environments, and in an accelerated bovine synovial fluid (BSF) environment at 60 °C under 5 atm O2. Aging results for Vitamin E blended UHMWPE (“VE-PE”) have shown improved stability compared to earlier generation materials. BSF provides an interesting aggressive accelerated aging environment that creates a different oxidation profile in conventional materials as compared to the standard aging environments. In BSF, conventional material oxidized over time mainly in the bulk rather than at the surface.
 

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