A-CLASS®
Highly Cross-Linked Polyethylene
• Highlycross-linkedpolyethylenereferstoUHMWPEexposedtoradiationdosesinexcessof4MRad1(A-CLASS®Poly=7.5MRad)
• Increasingcross-linking=increasingwearresistance+decreasingmechanicalproperties
• Balanced processing of A-CLASS® polyethylene drastically reduces wear while maintaining good mechanical properties
A-CLASS® Highly Cross-Linked Poly vs. Conventional Poly
• Wearinducedosteolysishasbeenrecognizedasanimportantclinicalissuewithconventionalpoly2
• Highlycross-linkedpolyethylenewasintroducedinthemid1990’stoimprovethebearingwearcharacteristicsofTHAandallowforlargerheads
• Wright testing shows a 92% or greater wear reduction for A-CLASS® polyethylene vs Wright conventional polyethylene3
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02.557.510Radiation Dose (MRad)
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Cross-Linking Process• Wright’sA-CLASS®PolyisIrradiatedwith7.5MRads
• Higherradiationdose=morecross-linking,slightlybetterwearresistance,andweakermechanicalproperties
• Wrighthasfoundanoptimumbalanceofenhancedwearpropertieswhilemaintainingimportantmechanicalpropertiesofthematerial
Product X-Link Dose1
A-CLASS®(Wright) 7.5MRad
Marathon®(DePuy) 5MRad
Longevity®(Zimmer) 10MRad
Crossfire®(Stryker) 10.5MRad
Durasul®(Zimmer) 9.5MRad
X3®(Stryker) 9MRad
E1®(Biomet) 10MRad
Heat Treatment• Wrighthasdevelopedaproprietarythermalremeltingcyclethatremovesfreeradicals
• Remeltinghasbeenshowntoeliminatemorefreeradicalsthanbelow-meltprocedures5
• Thisprocesshasbeenshowntoimprovetheoxidativestabilityofthematerial6
- Validatedinnaturalagingstudy:Nodetectableoxidationafterweartestingto5Mcandaginginairfor3years!
- Validatedinacceleratedagingstudy:Nodetectableoxidation!
• Wright remelting cycle eliminates need for anti-oxidant doping (i.e. Vitamin E)
Product HeatTreatment1
A-CLASS®(Wright) Remelted
Marathon®(DePuy) Remelted
Longevity®(Zimmer) Remelted
Crossfire®(Stryker) BelowMelt
Durasul®(Zimmer) Remelted
X3®(Stryker) BelowMelt
E1®(Biomet) BelowMelt*
Final Sterilization• Allpolyethylenelinersrequirepost-processingsterilization
• Mostcommonsterilizationmethods
-Ethyleneoxide(EtO)
•Doesn’taddfreeradicals7
-Gasplasma
•Doesn’taddfreeradicals8
-Gammaradiation
•Adds free radicals9
• Sterilizationwithoutradiationenhancesshortandlong-termoxidativeresistanceinsimulatorstudy10andinshelfagingstudy11
Product Final Sterilization1
A-CLASS®(Wright) ETO
Marathon®(DePuy) GasPlasma
Longevity®(Zimmer) GasPlasma
Crossfire®(Stryker) 3MRadgamma-N2
Durasul®(Zimmer) ETO
X3®(Stryker) GasPlasma
E1®(Biomet) Gamma
Poly Material Selection• WrightusescompressionmoldedGUR1020UHMWPE
• GUR1020hasahigherimpactstrength,tensilestrength,andyieldstrengththanGUR10504
Product Material1
A-CLASS®(Wright) GUR1020
Marathon®(DePuy) GUR1050
Longevity®(Zimmer) GUR1050
Crossfire®(Stryker) GUR1050
Durasul®(Zimmer) GUR1050
X3®(Stryker) GUR1020
E1®(Biomet) GUR1050
*Heated during diffusion of Vitamin E.
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References1. StephenKurtz,PhD,UHMWPEBiomaterialsHandbook,SecondEdition:UltraHighMolecularWeightPolyethyleneinTotalJointReplacementand
MedicalDevices(SanDiego:ElsevierAcademicPress,2009),p55.
2. BonoJV,SanfordL,ToussaintJT.Severepolyethylenewearintotalhiparthroplasty.ObservationsfromretrievedAMLPLUShipimplantswithanACSpolyethyleneliner.J Arthroplasty.Apr1994;9(2):119-125.
3. DataonfileatWright.
4. “StandardSpecificationforUltra-High-MolecularWeightPolyethylenePowderandFabricatedFormforSurgicalImplants”.ASTMInternational,2007.F648-07.
5. StephenKurtz,PhD,TheUHMWPEHandbook:Ultra-HighMolecularWeightPolyethyleneinTotalJointReplacement(SanDiego:ElsevierAcademicPress,2004),p112.
6. DataonfileatWright.
7. StephenKurtz,PhD,TheUHMWPEHandbook:Ultra-HighMolecularWeightPolyethyleneinTotalJointReplacement(SanDiego:ElsevierAcademicPress,2004),p45.
8. StephenKurtz,PhD,TheUHMWPEHandbook:Ultra-HighMolecularWeightPolyethyleneinTotalJointReplacement(SanDiego:ElsevierAcademicPress,2004),p46.
9. StephenKurtz,PhD,TheUHMWPEHandbook:Ultra-HighMolecularWeightPolyethyleneinTotalJointReplacement(SanDiego:ElsevierAcademicPress,2004),p44.
10. McKellopH,ShenFW,LuB,CampbellP,SaloveyR.Effectofsterilizationmethodandothermodificationsonthewearresistanceofacetabularcupsmadeofultra-highmolecularweightpolyethylene.Ahip-simulatorstudy.J Bone Joint Surg Am.Dec2000;82-A(12):1708-1725.
11. WillieBM,AshrafiS,AlajbegovicS,BurnettT,BloebaumRD.Quantifyingtheeffectofresintypeandsterilizationmethodonthedegradationofultrahighmolecularweightpolyethyleneafter4yearsofreal-timeshelfaging.J Biomed Mater Res A.Jun12004;69(3):477-489.