Analysis of Crosslinked and Conventional Polyethylene Explants

Collaborative Analysis of UHMWPE Explants: Conventional UHMWPE With No Radiation and Marathon

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.

Study Overview

• Status: Unknown
• Conditions: Osteoarthritis
• Intervention / Treatment: Device: Total hip arthroplasty

Detailed Description

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.

• Study Type: Observational
• Enrollment (Anticipated): 60

Contacts and Locations

Study Locations

• United States
  • Massachusetts
    • Boston, Massachusetts, United States, 02114
      • Orthopaedic Biomechanics and Biomaterials Laboratory at Massachusetts General Hospital
  • Virginia
    • Alexandria, Virginia, United States, 22306
      • Anderson Orthopaedic Research Institute

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

• Sampling Method: Non-Probability Sample

Study Population

Crosslinked and conventional polyethylene liners terminally sterilized without gamma-irradiation will be used for this study. Specimens will be selected from the implant retrieval collection maintained by the Anderson Orthopaedic Research Institute.

Description

Inclusion Criteria:

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

Exclusion Criteria:

• Liners terminally sterilized with gamma-irradiation

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Crosslinked polyethylene liners; Polyethylene liners from joint replacements that were crosslinked and heat treated to eliminate free radicals.	Device: Total hip arthroplasty; Replacement of a patient's native hip with an artificial implant featuring a metal-on-polyethylene articulation; Other Names: DePuy Marathon crosslinked polyethylene; DePuy Enduron conventional polyethylene
Conventional polyethylene liners; Polyethylene liners from joint replacements that manufactured from conventional UHMWPE and terminally sterilized by methods that did not involve gamma-irradiation.	Device: Total hip arthroplasty; Replacement of a patient's native hip with an artificial implant featuring a metal-on-polyethylene articulation; Other Names: DePuy Marathon crosslinked polyethylene; DePuy Enduron conventional polyethylene

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Oxidation levels	Polyethylene oxidation levels will be quantified as a function of depth away from the articular and rim surfaces using Fourier Transform Infrared Spectroscopy (FTIR). Pre and post-hexane and nitric oxide (NO) exposed post-hexane thin sections will be analyzed.	At an average of 5 years in vivo

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Absorbed lipids	Absorbed lipids will be evaluated by determining the level of carbonyls before and after hexane extraction using Fourier Transform Infrared Spectroscopy (FTIR).	At an average of 5 years in vivo
Crosslink density	Crosslink density will be evaluated using the gravimetric method on thin sections (~300μm) cut co-planar to the articular surfaces.	At an average of 5 years in vivo
Differential Scanning Calorimeter (DSC)	Differential Scanning Calorimeter (DSC) will be used to determine the 1st and 2nd heats, and 1st cool crystallinity, peak melting/crystallization points.	At an average of 5 years in vivo
Hydroperoxides	Hydroperoxides will be evaluated with FTIR by NO treatment after hexane extraction.	At an average of 5 years in vivo
Vinyl end-groups	Vinyl end-groups will be evaluated with FTIR after hexane extraction to quantify chain scission.	At an average of 5 years in vivo
Trans vinylene (TVI) unsaturations	Trans vinylene (TVI) unsaturations will be evaluated with FTIR after hexane extraction to determine radiation history and dose.	At an average of 5 years in vivo
Crystallinity	Infra-red crystallinity will be evaluated with FTIR after hexane extraction.	At an average of 5 years in vivo
Gel content	To quantify the extent of chain scission, gel content will be evaluated by measuring the non-extractable portion of the molecules using thin sections cut co-planar to the articular surfaces with a microtome and extracting the polyethylene chains from these sections in hot xylene.	At an average of 5 years in vivo

Collaborators and Investigators

• Sponsor: Anderson Orthopaedic Research Institute
• Collaborators: DePuy Orthopaedics; Orthopaedic Biomechanics and Biomaterials Laboratory at Massachusetts General Hospital
• Investigators: Study Director: Robert H Hopper, Jr., PhD, Anderson Orthopaedic Research Institute

Publications and helpful links

General Publications

• Malchau H, Bragdon CR, Muratoglu OK. The stepwise introduction of innovation into orthopedic surgery: the next level of dilemmas. J Arthroplasty. 2011 Sep;26(6):825-31. doi: 10.1016/j.arth.2010.08.007. Epub 2010 Oct 2.
• Engh CA Jr, Stepniewski AS, Ginn SD, Beykirch SE, Sychterz-Terefenko CJ, Hopper RH Jr, Engh CA. A randomized prospective evaluation of outcomes after total hip arthroplasty using cross-linked marathon and non-cross-linked Enduron polyethylene liners. J Arthroplasty. 2006 Sep;21(6 Suppl 2):17-25. doi: 10.1016/j.arth.2006.05.002.
• Muratoglu OK, Wannomae KK, Rowell SL, Micheli BR, Malchau H. Ex vivo stability loss of irradiated and melted ultra-high molecular weight polyethylene. J Bone Joint Surg Am. 2010 Dec 1;92(17):2809-16. doi: 10.2106/JBJS.I.01017.
• Bargmann LS, Bargmann BC, Collier JP, Currier BH, Mayor MB. Current sterilization and packaging methods for polyethylene. Clin Orthop Relat Res. 1999 Dec;(369):49-58. doi: 10.1097/00003086-199912000-00006.
• Currier BH, Van Citters DW, Currier JH, Collier JP. In vivo oxidation in remelted highly cross-linked retrievals. J Bone Joint Surg Am. 2010 Oct 20;92(14):2409-18. doi: 10.2106/JBJS.I.01006.
• Currier BH, Currier JH, Mayor MB, Lyford KA, Collier JP, Van Citters DW. Evaluation of oxidation and fatigue damage of retrieved crossfire polyethylene acetabular cups. J Bone Joint Surg Am. 2007 Sep;89(9):2023-9. doi: 10.2106/JBJS.F.00336.

Helpful Links

• Website for the Anderson Orthopaedic Research Institute

Study record dates

Study Major Dates

• Study Start: December 1, 2011
• Primary Completion (Anticipated): December 1, 2017
• Study Completion (Anticipated): December 1, 2017

Study Registration Dates

• First Submitted: November 28, 2011
• First Submitted That Met QC Criteria: November 30, 2011
• First Posted (Estimate): December 2, 2011

Study Record Updates

• Last Update Posted (Estimate): January 24, 2017
• Last Update Submitted That Met QC Criteria: January 23, 2017
• Last Verified: January 1, 2017

More Information

Terms related to this study

• Keywords: Outcome; Hip replacement; Oxidation; Crosslinked and conventional polyethylene; Crosslink density
• Additional Relevant MeSH Terms: Joint Diseases; Musculoskeletal Diseases; Rheumatic Diseases; Arthritis; Osteoarthritis
• Other Study ID Numbers: AORI2011-0101; MGH Agreement No: A208947 (Other Grant/Funding Number: DePuy Orthopaedics, Inc.)