AnapproachtoapatientwithAvascularnecrosisoffemoralheadandmanagementDrSmarajitPatnaik

SeniorConsultantOrthopaedicSurgeon

ApolloHospitals,

Bhubaneswar.

Avascularnecrosis

• (AVN)haslongbeenrecognizedasacomplicationoffemoralneckfractures,theusualexplanationbeingtraumaticdisruptionofthebloodsupplytothefemoralhead.

• Osteonecrosisalsoappearsasadistinctivefeatureinanumberofnon-traumaticdisorders:jointinfection,Perthes’disease,caissondisease,Gaucher’sdisease,systemiclupuserythematosus(SLE),high-dosagecorticosteroidadministrationandalcoholabuse,tomentiononlythemorecommonones.

• Whateverthecause,thecondition,onceestablished,maycometodominatetheclinicalpicture,demandingattentioninitsownright.

Aetiologyandpathogenesis

• Certainsitesarepeculiarlysusceptibletoischaemic necrosisincludingthefemoralhead,

• Thesesubarticular regionslieatthemostdistantpartsofthebone’svascularterritory,andtheyarelargelyenclosedbycartilage,givingrestrictedaccesstolocalbloodvessels.

• Thesubchondral trabeculae arefurthercompromisedinthattheyaresustainedlargelybyasystemofendarterioles withlimitedcollateralconnections.

• Localchangessuchasdecreasedbloodflow,haemorrhage ormarrowswellingcan,therefore,rapidlyspiraltoaviciouscycleofischaemia,reactiveoedema orinflammation,marrowswelling,increasedintraosseous pressureandfurtherischaemia.

• Theprocessdescribedabovecanbeinitiatedinatleastfourdifferentways:

• 1disruptionofthelocalbloodsupply

• 2venousstasisandretrogradearteriolarstoppage

• 3intravascularthrombosis

• 4compressionofcapillariesandsinusoidsbymarrowswelling.

TRAUMATICOSTEONECROSIS

• Intraumaticosteonecrosisthevascularanatomyisparticularlyimportant.• Infracturesanddislocationsofthehip,theretinacular vesselssupplyingthefemoralheadareeasilytorn.If,inaddition,thereisdamagetoorthrombosisoftheligamentum teres,osteonecrosisisinevitable.• Undisplaced fracturesalsosome timesresultinsubchondral necrosis;thismaybeduetothrombosisofintraosseous capillariesorsinusoidalocclusionduetomarrowoedema.• Significantly,inthesecasesitisalwaystheproximalfragmentwhichsuffers.Thisisbecausetheprincipalvesselsenterthebonesneartheirdistalendsandtakeanintraosseous coursefromdistaltoproximal.

NON-TRAUMATICOSTEONECROSISThemechanismsherearemorecomplexandmayinvolveseveralpathwaystointravascularstasisorthrombosis,aswellasextravascularswellingandcapillarycompression.

• Intravascularthrombosis:

Over80%ofcasesareassociatedwithhigh-dosagecorticosteroidmedicationand/oralcoholabuse.Fatembolismplaysapart,givingrisetocapillaryendothelialdamage,plateletaggregationandthrombosis.

Itseemslikelythatcoagulationabnormalitiesofonesortoranotherplayatleastacontributoryroleinsomeofthedisordersassociatedwithnon-traumaticosteonecrosis.

• Extravascularmarrowswelling:

High-dosagecorticosteroidsadministrationandalcoholoverusecausefatcellswellinginthemarrow,Thereisariseinintraosseous pressure.Thisincreaseinmarrowfatvolumeinthefemoralheadisthoughttocausesinusoidalcompression,venousstasisandretrogradeischaemialeadingtotrabecularbonedeath;inotherwords,theestablishmentofacompartmentsyndrome.

Whicheverofthesemechanismsofferstheprimarypathwaytonon-traumaticboneischaemia,itisalmostcertainthatbothintravascularandextravascularfactorscomeintoplayatafairlyearlystageandeachenhancestheeffectoftheother.

Pathologyandnaturalhistory

• Bonecellsdieafter12–48hoursofanoxia,yetfordaysorevenweeksthegrossappearanceoftheaffectedsegmentremainsunaltered.

• Duringthistimethemoststrikinghistologicalchangesareseeninthemarrow:lossoffatcelloutlines,inflammatorycellinfiltration,marrowoedema,theappearanceoftissuehistiocytes,andeventualreplacementofnecroticmarrowbyundifferentiatedmesenchymaltissue.

• Asthenecroticsectorbecomesdemarcated,vasculargranulationtissueadvancesfromthesurvivingtrabeculae andnewboneislaiddownuponthedead;

• Reparativenewboneformationproceedsslowlyandprobablydoesnotadvanceformorethan8–10mmintothenecroticzone.Withtime,structuralfailurebeginstooccurinthemostheavilyloadedpartofthe necroticsegment.Usuallythistakestheformofalineartangentialfractureclosetothearticularsurface,possiblyduetoshearingstress

Clinicalfeatures• Theearlieststageofbonedeathis

asymptomatic;bythetimethepatientpresents,thelesionisusuallyadvanced.Highindexofclinicalsuspicion.

• Historyofsteroidintake,alcoholabuse,SCD.Chemotherapy,radiation.

• Painisacommoncomplaint.Itisfeltinornearajoint,andperhapsonlywithcertainmovements.Painusuallyisradiatingtoipsilateralknee.

• Somepatientscomplainofa‘click’inthejoint, probablyduetosnappingorcatchingofaloosearticular fragment.

• Inthelaterstagesthejointbecomesstiffanddeformed.

• Localtendernessmaybepresentand,

• Movementsmayberestricted;inadvancedcasestheremaybefixeddeformities.Sectoralsign.

Diagnosisoftheunderlyingdisorder

• Inmanycasesofosteonecrosisanunderlyingdisorderwillbeobviousfromthehistory:aknownepisodeoftrauma,anoccupationsuchasdeep-seadiving,afamilybackgroundofGaucher’sdiseaseorsickle-celldisease,corticosteroids,alcoholabuse.• Ideallypatientswithveryearlynon-traumaticosteonecrosis,andchildrenwithearlyPerthes’disease,shouldundergolaboratorytestsforcoagulopathies;• IncasesofsuspectedSLE,antiphospholipid anti-bodiestobemeasured.

Prevention

• Whereriskfactorsforosteonecrosisarerecognized,preventivestepscanbetakenespeciallyinthemanagement ofcorticosteroidmedicationandalcoholabuse.• Anoxiamustbepreventedinpatientswithhaemoglobinopathies.• Decompressionproceduresfordiversandcompressed-airworkersshouldberigorously applied

Earlyevidenceofdisease

RadionuclidestudiesmaybeusedforearlydiagnosisofONFH.Fromallthedifferent radionuclidemodalities,positronemissiontomography(PET)providesareal-timeimageofthebonyphysiology.ItisassumedthatPETscansdetectONevenearlierthanMRIandalsohelppredicttheprogressionofthedisease.

Radiologicalaspectsaccordingtomodality

ImagingXray

• TheearlysignsofischaemiaareconfinedtothebonemarrowandcannotbedetectedbyplainX-rayexamination.

• X-raychanges,whentheyappear(seldombefore3monthsaftertheonsetofischaemia),Anareaofincreasedradiographicdensityappearsinthesubchondralbone;soonafterwards,suitableviewsmayshowathintangentialfracturelinejustbelowthearticularsurface– the‘crescentsign’.

• Inthelatestagesthereisdistortionofthearticularsurfaceandmoreintense‘sclerosis’,nowpartlyduetobonecompressioninacollapsedsegment.Occasionallythenecroticportionseparatesfromtheparentboneasadiscretefragment.

• The‘jointspace’retainsitsnormalwidthbecausethearticularcartilageisnotdestroyeduntilverylate

• Radioscintigraphy:SCD wherea‘cold’areacontrastssignificantlywiththegenerallyhighnuclideuptakeduetoincreasederythroblasticactivity.99mTc-HDPscans(inthebonephase)mayalsoshowa‘cold’area,particularlyifalargesegmentofboneisavascular(e.g.afterfractureofthefemoralneck).Moreoften,however,thepictureisdominatedbyincreasedactivity,reflectinghyperaemiaandnewboneformationintheareaaroundtheinfarct.

• Magneticresonanceimaging:MRIisthemostreliablewayofdiagnosingmarrowchangesandboneischaemiaatacomparativelyearlystage.Thefirstsignisaband-likelow-intensitysignalontheT1weightedspinecho(SE)image(andasimilarbuthigh-intensitysignalontheshort-tauinversionrecovery(STIR)image),correspondingtotheinter- facebetweenischaemicandnormalbone.Thesite andsizeofthedemarcatednecroticzonehavebeenusedtopredicttheprogressofthelesions

• Computedtomography: CTdoesshowtheareaofbonedestructionveryclearlyanditmaybeuseful inplanningsurgery.

MRI

MRIisthegoldstandardindetectingprecollapselesionsanddifferentiating

SteinburgClassification

Treatment

TreatmentoptionsaccordingtoARCOclassification

PRE-COLLAPSEAVN

• Pre-collapseAVNofferstheopportunityforjointpreservationandthenon-surgicalmanagementofAVNforsymptomaticornon-symptomaticpatients.Protectedweight-bearing,bisphosphonates andanti- coagulationforAVNassociatedwithhypercoagulability havebeenreportedwithvariablesuccess.

• Larger areasofAVN locatedintheweight-bearingzonewilltendtoprogressifnottreatedsurgically.Inthesurgicalmanagementofpre-collapseAVNnumerousprocedureshavebeenemployed.ThemajorityarevariationsonthethemeofpercutaneousdecompressionoftheAVNlesionaccompaniedbybonegrafting.

• Contemporarypracticealsooftenincludestheadjuvantuseofpotentialbiologicalagentssuchasconcentratedstemcells,bonemorphogeneticprotein(BMP)andplatelet-richplasma(PRP).

• Therearelimitedavailabledataontheuseofthesebiologicalagentsatthisstageandtheyhavenotbeenassessedinarandomized controltrial

• Vascularisedbonegraftshavebeenusedpreviouslybutarenowemployedlesscommonly.Thesameistrueforfemoralosteotomies.

POST-COLLAPSEAVN

• Thereisageneralconsensusthathippreservationproceduresarenotrecommendedinpost-collapseAVN.• Inthesecasesitismorejudicioustoconsidertotalhiparthroplastybecausetheresultsaremorereliable.However,itshouldbeappreciatedthathigherfailurerates,accountedforbyseveralfactors,areoftenencounteredinjointreplacementforsevereAVNofthefemoralheadcomparedwithTHAforothercausesofosteoarthritis.• Thefactorsthatofteninfluence outcomeareofthosethatweretheunderlyingcauseforAVN(e.g.previousradiotherapytohip/pelvis)andyoungpatientage.

Summaryontreatment

• Weight-bearingmodificationswhichwouldaimtoreducethejointreactiveforcestowardsthefemoralheaddidnotdelaytheprogressionofthediseaseandarethusnottobeconsideredasabeneficial• Statinsreducethebonemarrowadipocytesizeandprotectagainstcorticoid-inducedON.However,thereisnohigh-levelevidencetosupporttheroutineuseofstatinsforhigh-riskpatients.• Regardingenoxaparin,thereisnoevidenceofasuperioroutcomefrompatientsreceivingthismedicationtopreventthrombosisformationfromthosewhodonot.

• Iloprost,aprostaglandinanaloguethatcausesasystemicdilatationandinhibitsplateletaggregationinordertodecreasethebonemarrowoedema,isoftenuseful for treatment.

• Hyperbaricoxygentherapy(HBO)hasbeenpostulatedtoreversecellularischaemia andtodiminishthein"ammatory responseforthesymptomaticearlystage• bisphosphonates exertse!ects onprotectingthefemoralheadmorphology.• Extracorporealshockwavetherapy(ESWT),whichwasinitiallydevelopedforbreakingrenalstones,hasshowntoincreasethedensityofbonearoundthepelvis.

Surgicalprocedures

• Forallotherpre-collapsedlesionsandduetotheyoungageofmostpatients,femoralheadsparingproceduresareemphasized• Theseconservativeproceduresmaybedescribedasfollows:• CD;non-vascularizedbonegrafting;vascularizedbonegrafting;andproximalfemoralosteotomies.• Theevolutionofpracticehasnowadaysintegratedhumanmesenchymalcellsaswellasbonemorphogeneticproteins(BMPs)toenhancetheresultsofsurgery.• Someofthosenewapproachesconsistof:bonegraftenhancedwithmesenchymalcells;bonegraftenhancedwithBMP;anduseofporoustantalum

• TheactualrecommendationsaboutCDarethatitisamorecost-effectivechoicethanobservationalone.Itproducesbestresultsinhipswithoutevidenceofsubchondral collapseanditisthefirst linetreatmentforFicatstagesIandII.• Moreover,thereisnogeneralconsensusconcerningtheuseofnon-vascularizedbonegrafting.Still,someauthorsadvocateitsusewhenthereis<2mmofheaddepressionand<30%ofheadinvolvement.• VascularisedfibulaegraftmightbeasupplementaltechniquefollowingCDfailureandmaybeusedtotreatACROstagesIandIIorACROIIIwithminimalcollapseandsmallsizelesions.Thearticularcollapseshallbe<3mmandtheinvolvementofthefemoralhead shallnotbe>50%

• Varus- andvalgus-producing osteotomieswereaimedtoimprovejointcongruityandtoredistributetheweight-bearingloadacrossthefemoralheadtoalessaffected area.• Theanterolaterallesionsofthefemoralheadneedavalgus-"exionosteotomyinordertotransfertheweightmediallyandposteriorly• Themediallesionswillbetreatedwithavarus osteotomybutthereisthenaneedtopreservethelateralcolumnofthefemoralheadandthepatientshallkeep>30° ofadduction.• Recommendationsforproximalfemoralosteotomyconcernpatientsthatareaged<40years,ACROstageIIandIII,thathaveacombinedKerboulangleof<200°,noacetabularpathologyandanormalhiprangeofmotion.

Novelstrategies

Novel strategiesconcernessentiallymodifications ofCDtechniquesthatincludetheuseofosteo-inductive andosteogenicfactors.Inthatsense,adjunctionofmesenchymalstemcells(MSCs)ortheuseofBMPhasbeenstudied.New implantssuchasporoustitaniumrods,believedtostimulateboneingrowth,havebeendevelopedandimplanted.

Questionandanswers

ItisimportanttounderstandthatOsteonecrosisisbyitselfadifferentialdiagnosisforvariousdisordersnearlyallof whichproducesecondaryosteoarthritis,howeverthedevelopmentofheaddeformityisanearlyfindingwithOsteonecrosiswithcharacteristicprogression.Thedeformitiesarenotcharacteristicandwithdevelopmentofsecondaryosteoarthritisthemovementsarealsolostearly!Soasarulealwaystrytogivethediagnosisasa differentialdiagnosisandbesafe.

Whatisyourdifferentialdiagnosis?

• Typicaldifferentialdiagnosesinclude:• 1.Tuberculosisofhip:(OldcasesofOsteonecrosisonlywithrestrictionofmostmovements)• 2.Transientosteoporosisofhipinfemales.• 3.Primaryosteoarthritisofhip(oncetheosteoarthriticchangesdevelopinOsteonecrosis):deformityofheadandsectoralsignsabsent.• 4.OldPerthes disease,femoralheaddeformityduetoepiphyseal/otherdysplasiawithdevelopmentofsecondaryosteoarthritis.• 5.OldFemoralheadfracturewithsecondaryosteoarthritis.• 6.Monoarticular rheumatoidisassuchrareandifmentionedthenshouldbelastasitisadiagnosisofexclusion!

WhydoyoukeepOsteonecrosisasyourfirstdifferential?• History:• Singlejointinvolvement• Insidiousonset,slowprogression• Characteristic course• No constitutionalsymptoms• Deformities donotmatchwithstagingofTBhip(viz.eveninstageIIIthemovementsarefairlypreserved)• Nohistoryoftrauma

WhichsignshowslossofintegrityoffemoralheadTheintegrityofthefemoralheadallowsdefining pre- versuspost-collapselesionsandiftheintegrityislostduetomechanicalfailurethe‘crescentsign’ willappear

WhodescribedthepredictabilityofnecroticangleThesizeofthelesionalsohelpstopredicttheoutcomeasdescribedbyKerboul, whomeasuredthenecroticanglevalueseenoncoronalandsagittalviews.Inanotherpublication,37hipsweremeasuredanditwasdemonstratedthatallhipswithavalueof240° ormorecollapsed,allhipswithavalue<180° survivedand4/8hipsbetween190 and240degreescollapsed.

Howdoyoudefinefemoralheaddepression

Afemoralheaddepressionisdescribedwhenthereisachangeinthefemoralheadcontourof>2mmwhichmayleadtoaworseprognosis.

AcetabularaffectioninMRIcanwepreserveaprecollapsedheadInaddition,iftheMRIshowsanimplicationoftheacetabularwall,thetreatmentsforfemoralheadsavingshavebeendemonstratedtobeunsuccessful

WhichMRIfindingisassociatedwithworseclinicalprogressionAppearance ofboneoedema onMRIiscorrelatedwithworseningofhippain.