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1、应变理论在骨折愈合中的临床应用一点粗浅的了解2011-03-30n骨折愈合的分型n应变的概念n基于Perren应变理论的一些AO理念n附：微动促进骨折愈合的一项研究要点nFracture healing can be divided into two types:nprimaryordirecthealingbyinternalremodeling;nsecondaryorindirecthealingbycallusformationn骨折愈合分为2种类型n通过内塑形的一期或直一期或直接愈合接愈合n通过骨痂形成的二期或二期或间接愈合间接愈合直接愈合noccursonlywithabsolut
2、estabilityandisabiologicalprocessofosteonalboneremodelingn仅发生在绝对稳定绝对稳定固定时，它是骨单位重建的生物过程n绝对稳定使骨折部位的修复组织在生理负荷下的应变完全消除n将应变减少到临界值以下可以减少骨痂形成的刺激，使骨折的愈合没有出现肉眼可见的骨痂间接愈合noccurswithrelativestability(flexiblefixationmethods).Itisverysimilartotheprocessofembryologicalbonedevelopmentandincludesbothintramembraneou
3、sandendochondralboneformation.Indiaphysealfractures,itischaracterizedbytheformationofcallus.n发生于相对稳定固定时（弹性固定方法），包括膜内成骨和软骨成骨n除了加压技术外，所有的固定方法均可视为弹性固定，提供相对稳定性。n其特点是骨痂形成骨痂形成nBonehealingcanbedividedintofourstages:ninflammation;nsoftcallusformation;nhardcallusformation;nremodeling.n骨折间接愈合的四个阶段n炎性期n软骨痂形成期n
4、硬骨痂形成期n重塑形期nInterfragmentarymovementstimulatestheformationofacallusandaccelerateshealingn骨痂形成需要一定程度的力学刺激n骨折块之间的相对活动可刺激骨痂的形成，加速骨折的愈合PerrensstraintheorynThemannerinwhichmechanicalfactorsinfluencefracturehealingisexplainedbyPerrensstraintheory.nPerrenSM,CordeyJ(1980)Theconceptofinterfragmentarystrain.B
5、erlinHeidelbergNewYork:Springer-Verlag.nPerren应变理论解释了机械力学因素对于骨折愈合的影响Perrens strain theory Perren应变理论nMotionatthefractureresultsindeformationproducingstraininthegranulationtissueatthefracturesite.n骨折端的活动引起的形变会在骨折端肉芽组织中产生应变Strain-应变nStrainisthedeformationofamaterialwhenagivenforceisapplied.nNormalstra
6、inisthechangeinlength(l)incomparisontooriginallength(l)whenagivenloadisapplied.Thus,ithasnodimensionsandisoftenexpressedasapercentage.n在应力作用下，材料在单位长度内发生的形变n对材料施加应力后其长度发生的变化n没有单位，通常用百分比表示n=（L-L。）/L。n=L/Ln组织在功能正常状态下可耐受的变形程度有很大的变化范围n完整骨骼的正常应变程度为2%（骨折发生前）n肉芽组织的应变能力为100%n在早期，当骨痂主要成分为软组织时，骨折端耐受畸形或组织应变的强度要
7、大于后期的骨性骨痂nTheamountofdeformationthatatissuecantolerateandstillfunctionvariesgreatly.Intactbonehasanormalstraintoleranceof2%(beforeitfractures),whereasgranulationtissuehasastraintoleranceof100%.nBonybridgingbetweenthedistalandproximalcalluscanonlyoccurwhenlocalstrain(ie,deformation)islessthantheformi
8、ngwovenbonecantolerate.nThus,hardcalluswillnotbridgeafracturegapwhenthemovementbetweenthefractureendsistoogreatnThus,overloadingofthefracturewithtoomuchinterfragmentarymovementlaterinthehealingprocessisnotwelltoleratedn只有当局部的应变小于编织骨所能耐受的程度，远近端的骨痂才能发生骨性连接n因此，当骨折端的活动过大时，硬骨痂无法桥接骨折端n在骨折愈合的后期，过度的负荷使骨折块发生
9、过多的活动不利于骨折的愈合nCallusformationwillnottakeplacewhenthestrainistoolownAlow-strainenvironmentwillbeproducedifthefixationdeviceistoostiff,orifthefracturegapistoowide.Delayedhealingandnonunionwillresultn但是，当应变过小时骨痂无法形成n当固定装置过于坚硬或骨折间隙过宽时，会产生低应变的环境，此时可发生骨折不愈合或延迟愈合根据Perrensstraintheorynthestrainisthehigherth
10、esmallerthegapis.nThesamedeformingforceproducesmorestrainatthesiteofasimplefracturethanatthatofamultifragmentaryfracture.n骨折间隙越小，应变越大n相同的应力作用于简单骨折和粉碎骨折，其中简单骨折产生的应变较大nMultifragmentaryfracturestoleratemoremotionbetweenthetwomainfragmentsbecausetheoverallmovementissharedbyseveralfractureplanes,whichred
11、ucesthetissuestrainordeformationatthefracturegap.n粉碎骨折可耐受两个主要骨折块之间有更大范围的活动n因为其总的活动被不同的骨折平面所分担，因此减少了骨折间隙中组织的应变nAperfectlyreducedsimplefracture(smallgap)stabilizedundercompression(absolutestabilityandlowstrain)healswithoutexternalcallus(directhealing).n简单骨折（间隙小）解剖复位加压固定（绝对稳定，低应变）后，骨折发生无外骨痂的愈合（直接愈合）nAs
12、implefracture(smallgap)fixedwithabridgingplate(relativestability)isexposedtomovement(highstrain).Fracturehealingisdelayedorwillnotoccuratalln简单骨折（间隙小）用桥接钢板（相对稳定）固定后，骨折端的活动导致高应变，骨折愈合延迟甚至不愈合nTodaythereisclinicalexperienceandexperimentalproofthatflexiblefixationcanstimulatecallusformation,therebyaccele
13、ratingfracturehealing.nThiscanbeobservedindiaphysealfracturessplintedbyintramedullarynails,externalfixators,orbridgingplatesn已有临床和实验室证据表明弹性固定可刺激骨痂的形成，从而促进骨折的愈合n骨干骨折后，使用随内钉、外固定架、桥接钢板固定可观察到这一现象nInacomplexfracture(largegap)fixedwithabridgingplate(relativestability)thestrainwillbelowinspiteofmovement,an
14、dfracturehealingwilloccurwithcallusformation(indirectbonehealing).n复杂骨折（间隙大）用桥接钢板（相对稳定）固定后，骨折端虽有活动，但应变低，骨折发生有骨痂形成的愈合（间接愈合）外部机械刺激对应用弹性外固定固定的骨干截骨模型愈合作用的研究BackgroundnItisgenerallyacceptedthatsmallinterfragmentarymovements(IFMs)yieldbetterbonehealingresultsthanlargerIFMs(1mm).nHowever,theoptimalsizeofIF
15、Mwithinthel-mmrangeremainsundetermined.ObjectivenThepurposeofthisstudywastoinvestigatetheeffectofanexternallyappliedmechanicalstimulusonfracturehealingunderflexiblefixation.DesignnStimulationoffracturehealingundervariousconditionsofinterfragmentarymovementinaninvivofracturemodelon41sheepMethodsnStan
16、dardizedtransverseosteotomyof3mmgapsizeintheleftovinetibiawasfixedwithanunilateralexternalfixator.nToperformcontrolledaxialmicromovement,acustom-designedstimulationmodulewasappliedtothefixatorrods(Fig.1).Themodulewaselectromechanicallydrivenandcontrolledbyamicroprocessor.MethodsnThesheepweredividedi
17、ntofourIFMgroupsof0.0,0.2,0.4and0.8mmnandstimulatedwiththisamplitude（振幅）for1200cyclesperdayat1Hz.nExternaldynamizationbegan12dayspost-op.MethodsnAfterahealingperiodof6weeks,nbonemineraldensitynandbiomechanicalstabilitynwereevaluatedtodeterminethequalityofhealing.ResultsnTheamountofcallusformationinc
18、reasedsignificantlywithincreasingIFM(PO.O5).ResultsnHowever,highestbiomechanicalstabilityofthehealedboneandmineraldensityofthegaptissuewasachievedwithanIFMsof0.4mm.althoughthedifferenceswerenotsignificant.ConclusionsnTheseresultssuggestthattheoptimalinterfragmentarymovementforaccelerationofdelayedfracturehealingisintherangeof0.5mm
