Clinical trial NCT01484002: Analysis of Crosslinked and Conventional Polyethylene Explants
Official title: Collaborative Analysis of UHMWPE Explants: Conventional UHMWPE With No Radiation and Marathon
Study type: OBSERVATIONAL
Overall status: UNKNOWN
Conditions: Osteoarthritis
Keywords: Hip replacement
Crosslinked and conventional polyethylene
Oxidation
Crosslink density
Outcome
Lead sponsor: Anderson Orthopaedic Research Institute
Sponsor class: OTHER
Collaborators: name: Orthopaedic Biomechanics and Biomaterials Laboratory at Massachusetts General Hospital
name: DePuy Orthopaedics
First posted: 2011-12-02
Enrollment: 60
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Observational model: COHORT
Time perspective: RETROSPECTIVE
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.

Brief summary: 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.

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.

Eligibility criteria: 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

Primary outcomes:
measure: Oxidation levels
timeFrame: At an average of 5 years in vivo
Secondary outcomes:
measure: Absorbed lipids
timeFrame: At an average of 5 years in vivo
measure: Crosslink density
timeFrame: At an average of 5 years in vivo
measure: Differential Scanning Calorimeter (DSC)
timeFrame: At an average of 5 years in vivo
measure: Hydroperoxides
timeFrame: At an average of 5 years in vivo
measure: Vinyl end-groups
timeFrame: At an average of 5 years in vivo
measure: Trans vinylene (TVI) unsaturations
timeFrame: At an average of 5 years in vivo
measure: Crystallinity
timeFrame: At an average of 5 years in vivo
measure: Gel content
timeFrame: At an average of 5 years in vivo
Other outcomes:
Locations:
city: Boston
country: United States
facility: Orthopaedic Biomechanics and Biomaterials Laboratory at Massachusetts General Hospital
state: Massachusetts
city: Alexandria
country: United States
facility: Anderson Orthopaedic Research Institute
state: Virginia
Study officials:
affiliation: Anderson Orthopaedic Research Institute
name: Robert H Hopper, Jr., PhD
role: STUDY_DIRECTOR
References:
citation: 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.
citation: 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.
citation: 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.
citation: 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.
citation: 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.
citation: 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.