Publications & Reports

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Validation of Wear Simulation Methods

In this doctoral dissertation, O. Calonius evaluates a range of wear simulation methods for UHMWPE used in joint replacements. Click here to view the abstract page. The entire dissertation is published as an issue of Acta Polytechnica Scandanavica, but the first chapter and overview of wear particle analysis and slide track analysis can be downloaded as a separate pdf here.

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Prediction of Multiaxial Mechanical Behavior for Conventional and Highly Crosslinked UHMWPE

This study compares the predictive capability of the new Hybrid constitutive model with the J2-plasticity model for four conventional and highly crosslinked UHMWPE materials during multiaxial loading. The Hybrid model outperforms the J2-plasticity model both for combined uniaxial tension and compression predictions and for simulating multiaxial large deformation mechanical behavior produced by the small punch test.

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Multiaxial Fatigue Behavior of Crosslinked UHMWPE

The goal of this study was to evaluate the suitability of the small punch test for conducting miniature-specimen, cyclic loading experiments of conventional and highly crosslinked UHMWPE. Fatigue failures were consistently produced according to a power law relationship in the low cycle regime, corresponding to failures below 10,000 cycles.

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Taguchi Analysis of Accelerated Aging Conditions for UHMWPE

Using a Taguchi approach, this study documents the effects of heating rate, sample preparation, humidity, test temperature, and the irradiation-aging time interval on the effects of oxidation in UHMWPE after accelerated aging in an oxygen bomb. Accelerated aging results are compared with data collected from samples naturally aged for 3 and 5 years.

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Interaction of Oxidation and Crosslinking

The interaction between oxidation and crosslinking in gamma-irradiated ultrahigh molecular weight polyethylene with or without artificial aging was evaluated in this study. The results suggest that the storage environments and durations prior to irradiation and prior to artificial aging must be taken into account in attempting to duplicate the oxidation-crosslinking profiles that occur with actual implants in clinical use.

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Effect of Natural and Accelerated Aging on Inert-Packaged UHMWPE

Researchers from Queen's University at Belfast have investigated the effect of shelf storage for 3 years on inert-packaged UHMWPE after gamma irradiation. Gamma-irradiation of vacuum packaged UHMWPE promotes a degree of cross-linking and seems to reduce the susceptibility of gamma-irradiated UHMWPE to oxidative degradation upon removal from its vacuum packaging.

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Implant Wear in Total Joint Replacement

The American Academy of Orthopedic Surgeons (AAOS) has published a book reviewing the clinical, biological, design, and material factors influencing wear in total joint replacements. Edited by T.M. Wright and S. Goodman, Implant Wear was based on a symposium convened by the AAOS and the National Institutes of Health in October 2000. All 25 chapters of the book can be downloaded from the AAOS website in pdf format.

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Thermomechanical Behavior of Crosslinked UHMWPE

Three series of uniaxial tension and compression tests were conducted on two conventional and two highly crosslinked UHMWPEs. The data collected in this study will be used to develop constitutive models based on the physics of polymer systems for predicting the thermomechanical behavior of conventional and crosslinked UHMWPE used in total joint replacements.

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Deconvolution of Surface Topology in Crosslinked Acetabular Inserts

Quantitative analysis of surface morphology is crucial for the comprehensive evaluation of wear surfaces for crosslinked UHMWPE acetabular inserts after short-term implantation, when machining marks may be partially worn away or plastically deformed in vivo. The goal of this study was to provide a unified conceptual framework for discriminating between waviness and roughness of the articulating surface for machined orthopedic components.

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Effect of Resin, Processing, and Radiation Environment on Mechanical Degradation

The resin and processing route have been identified as potential variables influencing the mechanical behavior, and hence the clinical performance, of UHMWPE orthopaedic components. In this study, a series of accelerated aging experiments were conducted to systematically examine the influence of resin (GUR or 1900), processing method (bulk compression molding or extrusion), and sterilization method (none, in air, or in nitrogen) on the mechanical behavior of UHMWPE.

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