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GammaIrradiatedSoftTissueAllograftsareBiomechanicallyEquivalenttoAsepticNon-SterilizedTissuesEgleideY.ElenesM.S.andShawnA.HunterPh.D.AbstractAllogratsaetyiscontingentoneectivesterilizationmethodssuchasgammairra-diation.Howeverrecentclinicalstudieshaveassociatedgammairradiationwithde-creasedgratstrengthandincreasedallogratailureratesdespitedatathatshowsnodeleteriouseectstosottissuebiomechanicsatgammadosesbetween1.46and2.18mRad.Theobjectiveothisstudywastocomparethebiomechanicalpropertiesoan-teriorandposteriortibialistendonsandbone-patellarligament-boneBTBallogratssterilizedwithgammairradiationatadoseo1.7-2.1mRadtoasepticallyprocessednon-irradiatedtendons.Ourhypothesiswasthatgammairradiatedtendonswouldbebiomechanicallyequivalenttoasepticcontrols.Pairsoresh-rozentibialistendonsandbisectedBTBswereeithergammasterilizedorletuntreatedtoserveasasepticallyprocessednon-sterilizedcontrols.Eachgratwascyclicallyloadedintensionor2000cyclesatarateo2Hzallowedtorelaxorfveminutesandthentestedintensiontoailureat100strainrate.GammairradiatedBTBsexhibitedstructuralmaximumloadmaximumdisplacementstinessandmaterialailurestressailurestrainandelasticmoduliandcyclictendonelongationpropertiesthatwerenotsignifcantlydierentromnon-sterilizedcontrols.Gammasterilizedtibialistendonswerenotsignifcantlydierentromasepticcontrolsorthethreestructuralpropertiesandthreeotheourmaterialpropertiesbutdidhavelowercyclicelongationcomparedtocontrols.Thisdi-erencesuggeststhatgamma-treatedtibialistendonsmaybelesssusceptibletolaxitythanasepticgrats.Thisstudyreinorcesthattendonsterilizationviagammairradiationyieldsasaeallogratwithoutcomprisingbiomechanicalunction. ThepurposeofthisstudywastocomparethebiomechanicalpropertiesoftibialistendonsandBTBssterilizedwithgammairradia-tiontoaseptictendons.IntroductionGammairradiationhasanextensivehistoryouseorsterilizingsottissueallograts.Earlyresearchshowingdose-dependentre-ductionsinmusculoskeletaltissuebiomechanicsathighgammadoses3.0mRad1-3haspromptedtissuebankstoemploylowerdosesthatremainextremelyefcientindeactivatingmicroor-ganismswhileminimizingtissuedamage.Recentstudieshaveshownthatlowdosegammairradiationlooselydenedasap-proximately1.5-2.0mRaddoesnotalterthebiomechanicalprop-ertiesobone-patellartendon-boneBTBtibialisandsemiten-dinosustendonallograts4-5.StillclinicalstudiesreportinghigherailureratesinACLreconstructionsusingallogratsespeciallyinyoungerpatients6-8haveimplicatedgammairradiationasaprimarycauseorailurewithoutaullunderstand-ingopotentialailuremechanisms9-10.Thisnegativeperceptionhasspurredincreaseduseoasepticgratstosae-guardbiomechanicalintegritybutitcomesattheriskoimplantinganon-sterilegrat.Furtherresearchisneed-edtosupportgammairradiationuseatappropriatedosesthatdonotaectthegratsbiomechanicalintegrity.StudyObjectiveThepurposeothisstudywastocomparethebiomechanicalpropertiesoanteriorposteriortibialistendonsandBTBssteril-izedwithgammairradiationatadoseo1.7-2.1mRadtoasepti-callyprocessednon-irradiatedtendons.Ourhypothesiswasthatgammairradiatedtendonswouldbebiomechanicallyequivalenttoasepticcontrols.SpecimenPreparationPairedbisectedBTBsromagroupo10donors6maleand4e-malemeanage57.8yearsagerange49-72yearsoldandpairedanteriorandposteriortibialistendonsromadierentgroupo10donors5maleand5emalemeanage65.1yearsagerange40-74yearsoldwereasepticallyrecoveredandprocessedasresh-rozengratspercurrentstandardmanuacturingproceduresthatincludedaproprietarymethodthathasbeenvalidatedtoaSteril-ityAssuranceLevelSALo10-6.Tendonswererandomlyselectedandeithergammairradiatedondryiceata1.7-2.1mRaddoseorletuntreatedtoserveasasepticcontrols.BiomechanicalTestingTissueswerestoredat-65Cuntiltestingatwhichtimetheywerethawedinawaterbathsettophysiologictemperature37C.Allspecimensweretrimmedtoaminimumgagelength-to-widthratioo31andthecross-sectionaldimensionsandini-tialgagelengthsweremeasuredintheunloadedstateusingalasermicrometerandcalipersrespectively.ForBTBsthetibialboneblockswerepottedusingBondobodyllerresinincustommolds.Fortibialistendonstheendswereoldedinsandpapertopreventslippage.BothendsoeachspecimenweresecuredinpneumaticclampsandtestingwasconductedusingamaterialstestingsystemInstronElectroPulsE3000NorwoodMA.Eachtendonwaspreconditionedviacyclictensileloadingrom0-20Nat0.5Hzor10cycles.Thegratswerethensubjectedto2000cy-clesocyclictensileloadingatarateo2Hzwithloadssinusoidallyrampedbetween0Nand200Ninloadcontrol11.Specimenswereunloadedandallowedtorelaxorvemin-utesollowingthecyclicsub-ailuretesting.Lastlythespecimenswereloadedintensiontoailureatadisplacementrateo100initialgagelengthpersecond12-13.Alltestingwasconductedinacustomenvironmentalchamberthatmaintainedphysiologictemperature372CandconstantlymistedthespecimenswithsalinetomaintaintissuehydrationDataAnalysisTotaltendonelongationorthecyclictestwasexpressedasaper-centageanddenedasthestraindierenceollowingcompletionothesub-ailureloading.Structuralandmaterialpropertieswerecalculatedromailureload-displacementcurvesandstress-straincurvesrespectively.Nominalstrainwasdeterminedromtheratioogrip-to-gripdisplacementtotheinitialspecimenlength.Sti-nesswascalculatedastheslopeothelinearportionotheload-displacementcurvestypicallydenedbetween2080otheabsolutepeakorce.Similarlytheelasticmoduluswascalculatedromthestress-straincurvesotheailuretests.Maximumloadmaximumdisplacementailurestressandailurestrainwerealldenedatthebreakingpointontheailuretestcurves.Meanandstandarddeviationwerecalculatedoreachbiomechanicalprop-ertyandastudentt-testwasusedtodetectdierencesbetweengammairradiatedandasepticallypreparedtendonsandallre-portedp-valuesaretwo-tailedwith0.05signicancelevel.GammaIrradiatedSotTissueAllogratsareBiomechanicallyEquivalenttoAsepticNon-SterilizedTissues ResultsGammairradiatedtibialistendonsexhibitedstructuralpropertiesmaximumloadp0.918maximumdisplacementp0.737andstinessp0.053andmaterialpropertiesailurestressp0.996ailurestrainp0.716andelasticmodulusp0.196thatwerenotsignifcantlydierentromasepticcontrols.Tibialistendonshadsignifcantlylowerelongationatersub-ailureload-ingcomparedtoasepticcontrolsp0.026.Twotibialistendonsonepertreatmentailedduringcyclictestingandwereexclud-edromtheailureanalysis.ForgammasterilizedBTBsthestructuralpropertiesmaximumloadp0.473maximumdisplacementp0.911andstinessp0.596andmaterialpropertiesailurestressp0.667ailurestrainp0.478andelasticmodulusp0.275andcyclicelon-gationp0.310werenotsignifcantlydierentromasepticcontrols.GammaIrradiatedSotTissueAllogratsareBiomechanicallyEquivalenttoAsepticNon-SterilizedTissuesConclusionsPatientsaetyisparamountandourresultssupporttheuseogammairradiationatdoseso1.72.1mRadtoprovidesaesottissueallogratsthatmaintainsimilarbiomechanicalpropertiescomparedtonon-irradiatedasepticgrats.Theobservedreduc-tioninirradiatedtibialiselongationatercyclicloadingsuggeststhatthegamma-sterilizedtendonmaybelesssusceptibletoclini-callaxitycomparedtoaseptictibialisgrats. Reerences1.SchwartzHEetal.2006.Theefectogammairradiationonanteriorcruciateligamentallogratbiomechanicalandbiochemicalpropertiesinthecaprinemodelattimezeroandat6monthsatersurgery.TheAmericanJournaloSportsMedicine341747-1755.2.SalehpourAetal.1995.Dose-DependentResponseoGammaIrradiationonMechanicalPropertiesandRelatedBiochemicalCompositionoGoatBone-PatellarTendon-BoneAllograt.JournaloOrthopaedicResearch13898-906.3.FidelerBMetal.1995.GammaIrradiationEfectsonBiomechanicalPropertiesoHumanBone-PatellarTendon-BoneAllograt.TheAmericanJournaloSportsMedicine23643-646.4.BalslyCRetal.2008.Efectolowdoseandmoderatedosegammairradiationonthemechanicalpropertiesoboneandsottissueallograts.CellTissueBanking9289-298.5.GreavesLLHeckerATBrownCHJr.Theefectodonorageandlow-dosegammairradiationontheinitialbiomechanicalpropertiesohumantibialistendonallograts.AmJSportsMed2008Jul3671358-66.6.PallisMSvobodaSJCameronKLOwensBD.SurvivalcomparisonoallogratandautogratanteriorcruciateligamentreconstructionattheUnitedStatesMilitaryAcademy.AmJSportsMed2012Jun4061242-6.7.SpindlerKPHustonLJWrightRWKaedingCCMarxRGAmendolaAetal.Theprognosisandpredictorsosportsunctionandactivityatminimum6yearsateranteriorcruciateligamentreconstructionapopulationcohortstudy.AmJSportsMed2011Feb392348-59.8.KaedingCCArosBPedrozaAPielEAmendolaAAndrishJTetal.AllogratVersusAutogratAnteriorCruciateLigamentReconstructionPredictorsoFailureFromaMOONProspectiveLongitudinalCohort.SportsHealth2011Jan3173-81.9.SunKTianSZhangJXiaCZhangCYuT.AnteriorcruciateligamentreconstructionwithBPTBautogratirradiatedversusnon-irradiatedallogrataprospec-tiverandomizedclinicalstudy.KneeSurgSportsTraumatolArthrosc2009May175464-74.10.RappeMHorodyskiMMeisterKIndelicatoPA.NonirradiatedversusirradiatedAchillesallogratinvivoailurecomparison.AmJSportsMed2007Oct35101653-8.11.HoburgATKeshlaSSchmidtTSmithMGohsUPerkaCetal.Efectoelectronbeamirradiationonbiomechanicalpropertiesopatellartendonallogratsinanteriorcruciateligamentreconstruction.AmJSportsMed2010Jun3861134-40.12.DysonLetal.1999.HamstringTendonGratsorReconstructionotheAnteriorCruciateLigamentBiomechanicalEvaluationotheUseoMultipleStrandsandTensioningTechniques.TheJournaloBoneandJointSurgery81549-57.13.NoyesFRetal.1984.Biomechanicalanalysisohumanligamentgratsusedinknee-ligamentrepairsandreconstructions.TheJournaloBoneandJointSurgery663344-52.CenterforTissueInnovationandResearch2900CollegeDriveKetteringOhio454201-800-684-7783www.communitytissue.orgREV00SM-700-F-10