Analysis of Crosslinked and Conventional Polyethylene Explants

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

UNKNOWN

Total Enrollment

60 participants

Study Classification

OBSERVATIONAL

Study Start Date

2011-12-31

Study Completion Date

2017-12-31

Brief Summary

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This retrospective study will investigate the changes that occur in ultrahigh molecular weight polyethylene (UHMWPE) implants that have been retrieved from joint replacement patients. Analysis techniques will include Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeter (DSC) and crosslink density measurements. Crosslink density measurements will be evaluated as a function of distance away from the articular surface and the rim of the implant. Gel and hydroperoxide contents will also be evaluated. The objective is to characterize the in vivo and ex vivo changes that occur with cross-linked and conventional polyethylene bearings sterilized by methods that do not involve radiation. The investigators hypothesize that polyethylene absorbs lipids in vivo but experiences negligible oxidation or reductions in polymer crosslinking until it is explanted and stored at room temperature with access to ambient air.

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Detailed Description

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For many years, gamma-irradiation in air was a common method for the terminal sterilization of ultrahigh molecular weight polyethylene (UHMWPE) materials used for joint replacement. A serendipitous byproduct of sterilization with gamma-irradiation was polymer crosslinking that tended to improve the wear performance of the polyethylene. During the 1990s, however, the orthopaedic community became aware that gamma-irradiation created free radicals within polyethylene, rendering the material susceptible to oxidative degradation. In view of this potentially deleterious effect, terminal sterilization methods using chemical surface treatments were developed to avoid free radical formation. To induce polyethylene crosslinking without residual free radicals, manufacturers also developed methods to crosslink the polyethylene followed by heat treatments to eliminate free radicals. These crosslinked materials were introduce during the latter part of the 1990s and clinical outcome studies among hip replacement patients have demonstrated substantially reduced wear at early follow-up intervals based on radiographic measurements. However, the long-term performance of crosslinked polyethylene is unknown and some investigators have expressed concerns related to in vivo degradation. Additionally, some crosslinked UHMWPE components have shown high levels of oxidation and chain scission after removal from patients and storage in air. Among these implants, it is unknown whether the oxidation and chain scission occurred during implantation or after the polyethylene was removed from the patient.

This study will characterize the material properties of polyethylene liners retrieved from hip replacement patients. The study population will include crosslinked and conventional UHMWPE liners that were terminally sterilized without the use of radiation. To quantify the potential effects of different storage methods, liners that were vacuum packed and frozen after retrieval and others that were stored at room temperature with access to ambient light and air following explantation will be included in the study population. Analysis techniques will include Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimeter (DSC) and crosslink density measurements. Crosslink density measurements will be evaluated as a function of distance away from the articular surface and the rim of the implant. Gel and hydroperoxide contents will also be evaluated. The goal of the analysis is to better understand the changes in polyethylene material properties that occur in vivo and ex vivo.

Conditions

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Osteoarthritis

Study Design

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Observational Model Type

COHORT

Study Time Perspective

RETROSPECTIVE

Study Groups

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Crosslinked polyethylene liners

Polyethylene liners from joint replacements that were crosslinked and heat treated to eliminate free radicals.

Total hip arthroplasty

Intervention Type DEVICE

Replacement of a patient's native hip with an artificial implant featuring a metal-on-polyethylene articulation

Conventional polyethylene liners

Polyethylene liners from joint replacements that manufactured from conventional UHMWPE and terminally sterilized by methods that did not involve gamma-irradiation.

Total hip arthroplasty

Intervention Type DEVICE

Replacement of a patient's native hip with an artificial implant featuring a metal-on-polyethylene articulation

Interventions

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Total hip arthroplasty

Replacement of a patient's native hip with an artificial implant featuring a metal-on-polyethylene articulation

Intervention Type DEVICE

Other Intervention Names

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DePuy Marathon crosslinked polyethylene DePuy Enduron conventional polyethylene

Eligibility Criteria

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Inclusion Criteria

* Retrieved total hip arthroplasty liners maintained by the Anderson Orthopaedic Research Institute
* Crosslinked or conventional liners terminally sterilized without gamma-irradiation