专业英语 Unit 21教案学习资料

UnitTwentyOneOSTEOMYELITISAcuteosteomyelitisoccursmorefrequentlyinthemandiblethaninthemaxilla.Itstartswithaninfectionofthecancellousormedullaryportionofthebone,whichusuallyentersbywayofawoundoranopeningthroughthecorticalplateofbone(forexample,thealveolarsocket),admittinganinfectionintothecentralstructure.Thisinfectionmayenterasaresultofaperiapicalorpericoronalinfectionpriortoanysurgicalintervention,oritmaybeintroducedthroughaneedlepuncture,particularlyifpressuremethodshavebeenemployedorinterosseousanesthesiahasbeenamethodemployed.Theinfectionmaybelocalized,oritmaydiffusethroughtheentiremedullarystructureofthemandibleormaxilla,anditmaybeprecededbyanacuteinfection.Itcanbeprecededbysepticcellulitis,oritcanfollowwhatwasapparentlyasimpleextractionofaninfectedtooth.Theonsetofanosteomyelitisisevidentlyassociatedwiththelackofresistanceofanindividualpatienttotheparticularorganismsthatinvadetheosseousstructure.Priortotheadventofchemotherapeuticandantibioticagents,osteomyeliticinfectionwasnotuncommon.Itmostfrequentlyfollowedaninvasionthroughathirdmolarwound.Sincetheemploymentofantibiotictherapyatthefirstsignofsepticpostoperativesequelae,osteomyelitisisrarelyseen.Oninfrequentoccasions,however,thisdiseasestilloccurs,andtheuseofantibioticshasbutlittleimpedingeffectonitsprogress.Symptomsincludeadeeppersistingpain,occasionallyaccompaniedbyintermittentparesthesiaofthelip.Anedemaoftheoverlyingsofttissuesandanaccompanyingperiostitisisusuallypresent.Thepatientmayultimatelyexperiencemalaiseandanelevationintemperature.Theconditionmaypersisttoastateatwhichtheinfectionbreaksthroughthecorticalboneandinvadesthesofttissues,andindurationfollowedbyabscessformationbecomesevident.Sincewidevariationsinradiographicevidenceorclinicalsymptomsoccur,earlydiagnosissometimesisdifficult.Theosteomyeliticprocessoriginateswithinthecancellousstructureofthebone,anddestructionofthecancellousstructureoccurswithmuchlessresistancethanthatofthecorticalbone.Thecorticalboneisdense,andthedestructiveprocessmayprogressbeforeitcanberevealedintheradiographbecauseofthesuperimpositionofthedensercorticalbone.Inthemoreaggressiveorrampanttypes,destructionmayoccurrapidlyandthecorticalbonemaybeinvadedsothatradiographicevidencebecomesvisibleatanearlydate.Thisdestructiveprocesshasnodefinitepattern.Aradiolucentareaseenintheradiograph.isoftendescribedashavingawormyappearance.Intheinvasiveorrampantnonlocalizedtype,allteethinthesectionofthemandibleormaxillamaybecomemobileortender,andpusmaybeobservedaroundthenecksoftheteethandinterproximalspaces.Multipleperforatingsinusesmaybedrainingpusintotheoralvestibuleorburrowingintotheoverlyingmusculatureandformingabscesses,which,ifnotincisedanddrained,willspontaneouslyrupturetothesurface.Ifthislatterconditionispermitted,anugly,indentedscarresults.Treatment.Theearlieradiagnosiscanbemadeanddefinitivetreatmentstarted,thegreateristheopportunityofimpedingtheprogressoftheinfection.Evenbeforepurulentmaterialcanbeobtainedforculture,itisadvisabletobeginadministeringanantibioticinhighdoses.Ofcoursethismaymakeitdifficulttoobtainaculturewhensuppurationbegins,buttimeistheimportantfactor,andtheearlierantibiotictherapycanbestarted,thebetteristhechanceoftherapeuticcontrol.Assoonasitispossibletoobtainaculture,"theantibioticthatthelaboratoryfindstobemostefficaciousmaybegiven.Edemaandindurationshouldbeobservedcloselyforthefirstindicationoffluctuancesothatattheearliestpossiblemomentaliberalincisioncanbemadedowntothebonysurfacefortheearlyevacuationofpus,therebypreventingthepusfromelevatingtheperiosteum.Ifindurationextendsbeyondthelimitoftheincisionaftertheprimarydrainage,theincisionshouldimmediatelybeextended.Thedestructivenessofosteomyelitisiscausedbythepressureandlysisofsuppurativematerialinaconfinedspace.Astaphylococcusisusuallythecause.Ifthebacteriaarekilledortheantibioticstopstheirgrowth,resolutionoftheinfectionoccurswithouttheneedforsurgerybeyondtheextractionoftheoffendingtooth(iftheinfectionisodontogenicinorigin).Ifthebacteriaareresistanttoantibiotics(forexample,a"hospitalstaphylococcus")orifamassivecollectionofpushasformedbeforeeffectiveantibiotictherapycanbeinstituted,thenportionsofthebonebecomedevitalizedbecausetheirbloodsupplyhasbeencutoffbythrombosisofthevessels.Theislandofdeadbonethusformedbecomesaconvenientplaceforprecipitationoftheionizedcalciumthathasbeenmobilizedbythesurroundingosteolyticprocessandthereforethissequestrumappearsasaradiopaqueshadowontheradiograph.Naturetendstoexpelthesequestrum,althoughoccasionallyasmallsequestrumislysedduringlong,effectiveantibiotictherapy.Thepatternfortreatment,then,is(l)effectiveantibiotictherapy,(2)drainageofpurulentmaterialifandwhenpusformsinspiteofantibiotictherapy,(3)aperiodofsupportivetherapyduringwhichthedrainageareaiskeptopenbydressingsandtheantibiotictherapyiscontinued,and(4)sequestrectomy.Thesequestrumshouldnotberemovedtooearly.Itshouldbeclearlyoutlinedontheradiograph.Iftheinfectionhasbeencontrolled,thesequestrumisliftedgentlyoutofitssofttissuebed,orinvolucrum.Thisbedisnotcuretted.Occasionallytheoverhangingmarginsofcorticalbonearerongueredbacktocorticalbonethatrestsonintactmedullarybone.Thisiscalledsaucerization.Thetreatmentpatterncanbeinterruptedatanyofthefourstagesifnormalhealingoccurs.Theantibioticshouldbecontinuedforaminimumof4to6weeksafterdrainagehasceased.Ifclinicalandradiographicevidenceoframpantinvasionofthemedullarystructureoftheboneisfoundandtheinfectiousprocesshasnotperforatedthecorticalplate,holesmaybedrilledthroughtheinferiorborderofthemandibletopermitdrainageofthecancellousstructure.Thislatterprocedureiscontroversialanddependsonthejudgmentanddiscretionofthesurgeon,whowillhavetoevaluatethecaseaccordingtoitsbehaviorpattern.Decorticationhasbeenemployedwithsatisfactoryresults.Intraoraldecorticationwithimmediatesofttissueclosurefollowedbypressurebandagesplacesvasculartissueincontactwiththedecorticatedmedullarybonethathasbeendeprivedofitsphysiologicalbloodsupply.Inreestablishinganavailablebloodsupply,antibiotictherapymaybeexpectedtobeofgreatervalue.Hjorting-Hansenhasdescribedindetaildecorticationofthemandibleinthetreatmentofosteomyelitis.Thedecisionwhethertoextractexcessivelymobileteethinthesegmentofthejawwheresuppurationisvisiblearoundthegingivaisanotherpointofcontroversyandonethatrequiresthekeenestdiscretionandjudgment.SomeofthemostspectecularsuppurativeandrampantcasescanApparentlyreachacrisis;atwhichpointsymptomswillsubsideandregenerationbeginwithouttheextractionofmobileteeth.Theoffendingtooth,ofcourse,isusuallyextracted.Drainageincisionsforosteomyelitishaveatendencytoproliferatelargeamountsofgranulationtissue,whichwillexpelartificialdrainsfromthewounds.Unlessretainedwithmattresssuturesoverthedressings,drainagegauzethatispackedintothewoundmaybecomeextruded.Suturingofthedrainagematerialmaybenecessarytomaintainitspositionsothatthewoundremainssaucerized.Thisprocedurepertainstobothintraoralandextraoralwounddressings.Theretentionofdressingsthatmaintainsaucerizationofthewoundforintervalsof5to7dayswithoutreplacementisrecommendedunlessclinicalsymptomsindicateintervention.TopazianandGoldberghaveauthoredanindepthtextonmanagementoforalan