肘关节损伤X线平片阅读技巧.docx

肘关节损伤X线平片阅读技巧.docx

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肘关节损伤X线平片阅读技巧

HowtoreadtheelbowXray

JulietCaldwellMD,NewYork-PresbyterianHospital/WeillCornellMedicalCenter

Fractureslinescanbedifficulttovisualizeafteracuteelbowinjury,particularlyinchildren.Belowareeightsequentialstepstoaidintheradiographicrecognitionofoccultsignsofinjury.

Step1:

hourglasssign

Searchforanadequate"hourglasssign",or"figureofeight"atthedistalhumerus.Ifabsentthestudyisnotatruelateralandinterpretationofsteps2through4islessreliable.

Here'sanexampleofatruelateral;notethesymmetricfigureofeight/hourglasssignatthedistalhumerus;alsonoticetheposteriorfatpad?

（seebelow.）

HereisanimperfectlateralradiographaccompaniedbyanormalAPradiograph;noticehowthefigureofeight/hourglassisasymmetric:

Step2:

anteriorfatpadevaluation

Avisibleanteriorfatpadcanbenormal;itisasmallradiolucentshadowadherenttotheanterioraspectofthedistalhumerus:

Anabnormalanteriorfatpadisdescribedasa"sailsign"becauseitisunusuallyprominentandbowsoutwardtoformatriangularshape.Aftertrauma,bloodcanaccumulateintheintraarticularspaceandpushthefatpadanteriorly;apositivesailsigninthesettingoftraumaisareliableindicationofanintraarticularfracture–evenifnofracturelinecanbeidentified.Anatraumaticsailsignimpliesintraarticularfluidofaninflammatorynature.

Step3:

posteriorfatevaluation

Radiographicvisualizationofaposteriorfatpadisnevernormalandalwayssignifiesfluidintheintraarticularspace.Again,inthesettingoftrauma,thisstronglyimpliesfractureofanarticularsurface.

Hereisaradiographwithbothasailandposteriorfatpadsign:

Step4:

anteriorhumeralline

Thislineshouldintersectthemiddlethirdofthecapitellumonthelateralview.Fracturesusuallyresultindisplacementofthecapitellumposteriorly（versusanteriorly）.Ifthefilmisnotatruelateral,interpretationoftheanteriorhumerallinebecomesfallible.

Thisradiographdepictsanormalanteriorhumeralline:

Step5:

radio-capitellarline

Thislineisdrawnthroughthemiddleoftheradiusposteriorly/rostrallyandshouldbisectthecapitellumonboththelateralandtheAPelbowradiograph.Failuretoalignproperlyindicatesaradialheaddislocationthatrequirespromptreductionifneuro-vascularcompromiseistobeavoided.

Step6:

inspectionoftheradialhead

Carefulinspectionisparamountsincefracturelinesareoftennotvisible;lookforsubtledisruptionsinthecorticalcontour.Examinetheradiographbelow:

Noticehowtheradiusbisectsthecapitellumonthisview;howeverthereisasubtlecorticaldisruption/acuteangulationatthesuperioraspectofthedistalradiusindicatingfracture.

Normalradio-capitellarlines:

Noticethatthisisnotanideallateralmakinginterpretationoftheanteriorhumerallinedifficult;howevertheradiusshouldbisectthecapitellumonallviewsregardlessofadequacy;alsonotetheposteriorfatpad.

Anabnormalradio-capitellarlineisdepictedbelow:

Onbothviewstheradiusfailstobisectthecapitellumindicatinganobviousradialheaddislocation.Alsonotetheanteriorandposteriorfatpads,aswellastheobviousolecranondeformity.AradialheaddislocationwithanolecranonfractureiscalledaMonteggiainjury.

Thisradiographdemonstratesabnormalalignmentoftheanteriorhumerallinestronglysuspiciousforfracture.（Theanteriorhumerallineofatoddler/childmustalsointersectthemiddlethirdofanossifiedcapitellum;alsonotetheposteriorfatpadandsailsign.）

Step7:

distalhumerusexamination

Signsofhumeralfracturearealsocommonlysubtle;breakagemayonlybeevidencedbyanabnormalanteriorhumeralline.Examtheradiographbelow:

Theanteriorhumerallineisperhapsslightlyoffasitseemstointersecttheanteriorthirdofthecapitellum,whiletheradio-capitellarlineisintact.Thereareprominentsailandposteriorfatpadsigns;andoncarefulinspectiononeseesthesubtlecorticaldisruptionalongtheposterioraspectofthedistalhumerus.

Step8:

Lookforobviousfracturelinesandsubtledisruptionsincorticalcontour.

Thisisnotagoodlateralradiographsointerpretationoftheanteriorhumerallineisunreliable.Thereisnoobviousanteriororposteriorfatpad,andtheradio-capitellarlineisintact.Theradialheadanddistalhumerusappearfine,whilethereisanobviousproximalolecranonfracture.

Theanteriorhumerallineisperhapsslightlyoffasitseemstointersecttheanteriorthirdofthecapitellum,whiletheradio-capitellarlineisintact.Thereareprominentsailandposteriorfatpadsigns;andoncarefulinspectiononeseesthesubtlecorticaldisruptionalongtheposterioraspectofthedistalhumerus.