Publications & Reports

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2008 ORS Poster: Future Young Patient Demand for Primary and Revision Joint Replacement

Researchers from Exponent have developed updated nationwide projections for primary and revision TJR for the young patient population in the U.S. Using the most recent procedure data currently available for the U.S., previous projections were updated and the hypothesis was tested that patients younger than 65y will represent the majority (> 50%) of the anticipated demand for primary and revision TJR in the U.S. between 2010 and 2030. While researchers previously forecast a massive demand for primary hip and knee replacement, the current study underscores the major contribution that young patients are expected to play in the future utilization of primary TJR surgery.

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2008 ORS Poster: In Vivo Oxidation, Oxidation Potential, and Clinical Performance of First and Second-Generation Highly Crosslinked Acetabular Bearings for THA

Highly crosslinked polyethylenes were developed to reduce wear in THA and are thermally processed by remelting or annealing. The main hypothesis was that highly crosslinked polyethylene formulations would have lower oxidation, oxidation potential, and lower head penetration than historical gamma-air and conventional gamma-inert sterilized liners. 109 highly crosslinked (90 - 105 kGy) retrieved components were compared with 48 gamma sterilized (25-40 kGy) controls. Penetration measurements were significantly lower in the highly crosslinked groups. Regional variations in oxidation were observed in all groups except for the remelted and sequentially annealed groups. The results of this retrieval study support the hypothesis that highly crosslinked polyethylene reduces in vivo wear, however the oxidation resistance was formulation-dependent.

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2008 ORS Poster: Immunohistochemical Analysis of Periprosthetic Tissue from THR Revision Surgery

Researchers from Drexel University have developed a comprehensive approach to characterizing the specific and non-specific immune response of retrieved periprosthetic tissue from three cohorts of implant devices. Tissue samples were collected from THA revision surgeries of uncemented polyethylene (PE) hip components. The presence of macrophages, T cells, plasma cells and neutrophils was detected in tissue taken from historical, remelted and highly crosslinked polyethylene implants. These data provide the basis for a better evaluation of THR polyethylene-based inflammatory trends.

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2008 ORS Poster: Polyethylene Particle Load Around Retreived Artificial Discs

The purpose of this study was to compare the polyethylene (PE) wear particle load of periprosthetic tissue from total disc replacement (TDR) with results from total hip replacement (THR) at the time of revision surgeries. PE particles were present in TDR and THR tissues, however the load for TDR implants was greater with pre-1998 TDR polyethylene components as compared the post-1998 polyethylene components. This is the first study to demonstrate a quantitative particle load comparison between TDR and THR periprosthetic tissue.

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2008 ORS Poster: Post Damage in Three Contemporary Designs of Posterior-Stabilized Knee Components

The objective of this study was to study the mechanisms of damage at the post in contemporary PS designs and to compare them with the results of a historical gold standard, the IB/PS II. Evidence of damage, usually scratching or burnishing, to the stabilizing post was noted for all of the contemporary PS TKR replacements regardless of the design, similar to the PS IBII components. The extent of post damage was generally mild, and the post was generally not observed to suffer from severe fatigue wear. Wear performance seemed to be insensitive to different designs in all regions. Condylar and post wear for each design followed the general increasing trend with in vivo time, consistent with a fatigue mechanism, while the backside wear was less sensitive to it.

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2008 ORS Poster: In Vivo Oxidation and Oxidation Potential for Polyethylene in Total Disc Replacement

The aim of this study was to investigate the oxidation potential of polyethylene in total disc replacements in the context of the sterilization environment. The main hypothesis was that the rim region of the polyethylene core would exhibit greater oxidation and oxidation potential than the dome. The data support the hypothesis that, for the two types of historical packaging methods employed by the manufacturer, oxidation and oxidation potential were significantly higher at the rim as opposed to the dome.

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2008 AAOS Poster: In Vivo Oxidation is the Primary Contributor to Delamination in TKA

It remains unclear to what extent in vivo oxidation contributes to fatigue wear in TKA. We studied the oxidation profiles in 70 consecutively traced TKA inserts from one manufacturer. Due to their relatively short shelf lives and the significant regional variations between the surface and backsides, oxidation was inferred to have taken place in vivo, supporting our hypothesis that in vivo oxidation is a contributing factor to delamination in TKA. We found no evidence to suggest that in vivo oxidation is related to pitting. Our data also did not support the hypothesis that resin and conversion techniques substantially influence the resistance of tibial inserts to in vivo oxidation.

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6th Combined ORS Meeting Poster: Validation of Hybrid Model and Ultimate Chain Stretch Criterion for a Second-Generation Highly Crosslinked UHMWPE

An analytical model, known as the Hybrid Model (HM), has been shown to accurately capture the large deformation behavior of highly crosslinked UHMWPE. Previous model validation efforts have been focused on predicting the tensile rupture of highly crosslinked materials under uniaxial and multiaxial loading conditions by using the ultimate chain stretch as the underlying theory for failure in polymers. However, it was unknown whether the HM or the ultimate chain stretch criterion would be applicable to second-generation, highly crosslinked UHMWPEs. Consequently, the purpose of the present study was to validate the HM and ultimate chain stretch criterion for a second-generation highly crosslinked material.

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3rd UHMWPE International Meeting - Polyethylene in Total Joint Replacement Systems: Concerns and Solutions

International experts from Europe, the United States, and Asia converged on Madrid for two days of scientific discourse on UHMWPE on September 14-15, 2007. Topics covered at the meeting included in vivo oxidation, Vitamin E, 2nd-generation highly crosslinked UHMWPE, and wear. Transactions of the meeting are now available for download. Speakers at the meeting have been invited to share their presentations via uhmwpe.org, and are made available below individually with the permission of the authors. It was announced that the 4th UHMWPE International Meeting will be organized by Prof. Luigi Costa in Torino, Italy in September 2009.

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3rd UHMWPE International Meeting Presentation: On the Mechanical Properties of UHMWPE

This seminar reviews the mechanical behavior of conventional and highly crosslinked UHMWPE. Methods to more effectively reduce free radicals without having to remelt the material (e.g, doping with vitamin E) have been explored as a means to maintain crystallinity, while simultaneously maintaining better mechanical properties of crosslinked UHMWPE. The combined effects of radiation-induced crosslinking followed by remelting or annealing on mechanical properties of UHMWPE can be complex. Crosslinked materials are found to be more sensitive to notches under uniaxial tensile loading as compared with non-crosslinked UHMWPE, however little difference was found between remelted and annealed UHMWPE materials.

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