Rev. bras. ortop. vol.50 número3

w w w . r b o . o r g . b r

Original

Article

Comparative

radiographic

analysis

on

the

anatomical

axis

in

knee

osteoarthritis

cases:

inter

and

intraobserver

evaluation

夽

Luiz

Felipe

Matos

_,

_Marcos

_Giordano

_,

_Gustavo

_Novaes

_Cardoso

_,

Rafael

Baptista

Farias

_,

_Rodrigo

_Pires

_e

_Albuquerque

a_{HospitalFederaldoAndaraí,RiodeJaneiro,RJ,Brazil}

b_{HospitaldaForc¸aAéreadoGaleão,RiodeJaneiro,RJ,Brazil}

c_{KneeSurgeryService,InstitutoNacionaldeTraumatologiaeOrtopedia(INTO),RiodeJaneiro,RJ,Brazil}

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Articlehistory:

Received12May2014 Accepted1July2014 Availableonline28May2015

Keywords:

Osteoarthritis/radiography Knee

Lowerextremity

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Objective:Tomakeacomparativeinterandintraobserveranalysisonmeasurementsofthe anatomicalaxisbetweenpanoramicradiographsofthelowerlimbsinanteroposterior(AP) viewwithbipedalweight-bearing,onshortfilm.

Methods:Anaccuracystudycomparingradiographicmeasurementson47kneesofpatients attendingthekneesurgeryoutpatientclinicduetoosteoarthritis.Theradiographic evalua-tionusedwasasstandardizedforthetotalkneearthroplastyprogram,includingpanoramic APviewsofthelowerlimbsandshortradiographsofthekneesinAPandlateralviews,all withbipedalweight-bearing.Followingthis,theanatomicalaxisofthelowerlimbsorthe femorotibialanglewasmeasuredbyfiveindependentexaminersonthepanoramicand shortAPradiographs;threeoftheexaminerswereconsideredtobemoreexperiencedand two,lessexperienced.Allthemeasurementsweremadeagainbythesameexaminersafter anintervalofnotlessthan15days.Thestatisticalanalysiswasperformedusingthe intr-aclasscorrelationcoefficient,inordertoevaluatetheinterandintraobserverconcordance oftheanatomicalaxismeasurements.

Results:Fromthestatisticalanalysis,itwasobservedthattherewasstronglysignificant concordance betweenthe anatomicalaxis measurements onthe panoramic andshort radiographs,forallthefiveexaminersandforbothmeasurements.

Conclusions: Undertheconditionsstudied,shortradiographswereequivalenttopanoramic radiographsforevaluatingtheanatomicalaxisofthelowerlimbsinpatientswithadvanced osteoarthritis.Themeasurementsusedalsoshowedhighratesofinterandintraobserver concordanceandreproducibility.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

夽

WorkdevelopedintheDepartmentofOrthopedicsandTraumatologyandtheDepartmentofRadiologyoftheHospitaldaForc¸aAérea doGaleão,RiodeJaneiro,RJ,Brazil.

∗

Correspondingauthor.

E-mail:rodalbuquerque19@gmail.com(R.P.eAlbuquerque). http://dx.doi.org/10.1016/j.rboe.2015.05.003

joelho.

Avaliac¸ão

inter

e

intraobservadores

Palavras-chave:

Osteoartrite/radiografia Joelho

Extremidadeinferior

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o

Objetivo: Fazeraanálisecomparativaintereintraobservadordamedidadoeixoanatômico entreasradiografiaspanorâmica,dosmembrosinferiores(MMII)comraioanteroposterior (AP)eapoiobipodálicoeAPcomcargabipodalemfilmecurto.

Métodos: Foifeitoestudodeacuráciaquecomparoumedidasradiográficasem47joelhosde pacientesdoambulatóriodecirurgiadojoelho,porosteoartrite(OA).Aavaliac¸ãoradiográfica usadafoiapadronizadaparaaprogramac¸ãodeATJ,incluindoasincidênciaspanorâmicados MMIIemAPeasradiografiascurtasdosjoelhosemAPeperfil,todascomapoiobipodálico. Emseguida,asradiografiaspanorâmicasecurtasemAPtiveramoseixosanatômicosdos MMIIouângulofemorotibial(AFT)medidosporcincoexaminadoresindependentes,dos quaistrêseramconsideradosmaisexperientesedoismenosexperientes.Todasasmedidas foramrefeitaspelosmesmosexaminadoresemumintervalonãomenordoque15dias.A análiseestatísticafoifeitacomousodocoeficientedecorrelac¸ãointraclasses(ICC_)para avaliaraconcordâncianamedidadoeixoanatômicointereintraobservadores.

Resultados:Apósanáliseestatísticaobservou-seforteconcordânciasignificativaentreoeixo anatômicomedidonasradiografiaspanorâmicaecurtaparatodososcincoexaminadores eparaambasasmedidas.

Conclusões: Nascondic¸ões estudadasa radiografia curtaequipara-se à panorâmicana avaliac¸ãodoeixoanatômicodosMMIIempacientescomOAavanc¸ada.Amensurac¸ãousada tambémmostraaltataxadeconcordânciaereprodutibilidadeintereintraobsevadores.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Todososdireitosreservados.

Introduction

The alignment of the lower limbs, evaluated according to their anatomicaland mechanical axes,isconsidered to be a fundamental element in the genesis and progression of degenerativejointdiseaseorosteoarthritis(OA)oftheknee.1–6

Valgusorvarusdeformitiesofthekneearerelatedtotherisk thatthelateralandmedialcompartments,respectively,may beaffected.2,3,5,6_{Knowledgeofthisalignmentalsobecomes}

essentialforadequatetherapeuticplanningforpatientswith kneeOA,especiallyforthosewhoareawaitingosteotomyor arthroplasty,aswellasfortheirpostoperativefollow-up.3,7–10

Although clinical assessment is correct and necessary, radiographicexaminationisafundamentaltoolfor preopera-tiveplanning.3,7–10_{Panoramicradiographyofthelowerlimbs}

inAPviewwithweightborneeitherononefootoron two feetisconsideredtobethegoldstandardandiswidely recom-mendedinthesesituations.1–4,7–13_{However,shortradiographs}

ofthekneesremainessentialforbetterunderstanding, stag-ingandclassificationofdegenerativedisease,inAPandlateral views,alsowithweight-bearing.2,5,6,14–18_{Therearelogistic}

dif-ficultiesinproducingpanoramicradiographs,whichmaybeof dubiousqualitywhenperformed.Thehipsoranklesareoften omitted,whichmaybebecauseofpoorpositioningbetween theapparatusandthepatient,inadequatepenetrationofone oftheextremitiesorincompatibilitybetweenthesizesofthe filmandpatient. Moreover,panoramicradiography exposes patientstogreaterquantitiesofionizingradiationandleads toadditionalcosts.5,6,15_{Inthislight,weconceptualizedastudy}

with the following objectives:to evaluate the reliability of

measurementsofthefemorotibialangle(FTA)onshort radio-graphsincomparisonwiththevaluesfoundonpanoramic radiographs ofthe lower limbs; and toevaluatethe repro-ducibilityofinterobserverandintraobservermeasurements.

Materials

and

methods

Anaccuracystudy wasconductedtocompareradiographic measurementson50knees,fromthefirstpatientswho pre-sentedatthekneesurgeryoutpatientclinicofourinstitution withanindicationfortotalkneearthroplasty(TKA)because ofOA:KellgrenandLawrence19_{3or4andAhlbäck}20_3–5,as

assessedbytheseniorresearcher(MNG).Theonlyexclusion criterionwasaradiographicexaminationofinadequate qual-ity,andthreekneeswerethuseliminatedfromthisstudy.The radiographic evaluationusedwas theonestandardizedfor schedulingTKA,includingpanoramicradiographsofthelower limbsinAPview(longradiographs)andshortradiographsof thekneesinAPinlateralviews,allwithweightborneontwo feet.

Theradiographicexaminationswereperformedinthe radi-ology sectorofourservice usingthe PrestigeSI apparatus. The equipment wasoperated bya singleradiology techni-cian,withouttheaidofradioscopy.Carewastakentoensure that the knees were extendedtotheir maximum and that thepatients’patellaewerefacingforwards.Thefilmsforthe panoramicradiographsallmeasured130cm×35cm(Kodak®) and the films for the short radiographs, 24cm×30cm (Kodak®_{). Following this,the anatomical axesofthe lower}

Fig.1–Panoramicradiographofthelowerlimb.

fiveindependentexaminers.Twoofthese(MNGandRPA)were consideredtobemoreexperiencedandhadbeentitular mem-bersoftheBrazilianSocietyofOrthopedicsandTraumatology (SBOT)formorethan5years;one(LFM)wasconsideredtohave intermediate-levelexperienceandhadbeenatitularmember oftheSBOTforlessthan1year,andwasdoingspecialization traininginkneetraining;andtwo(GNCandRBF)were consid-eredtobelessexperiencedandwerestudyinginthethirdyear ofmedicalresidencyinorthopedicsandtraumatology.Allof themeasurementsweremadeagainbythesameexaminers afteranintervalofnotlessthan15days.

The anatomical axis was evaluated on the panoramic radiographsbymeansoflinestracedoutalongthelongaxes ofthefemurandtibia(Fig.1).Themeasurementtechniquefor theshortradiographswasassuggestedbyKhanetal.,6_based

onthepreviousstudiesofHsuetal.11_{andKrausetal.}5_Apoint

wasdefinedonthefemuratthecenteroftheintercondylar space,andanotherone10cmproximally,atthemidpointof thedistancebetweenthetwoexternalcortexes.The measure-mentonthetibiastartedfromapointmarkedatthecenter ofthe tibialeminences,withasecondpoint marked10cm distally,atthemidpointofthedistancebetweenthetwo exter-nalcortexes.Linesjoiningthefemoralandtibialpointswere tracedoutandtheirintersectioncorrespondedtothe anatom-icalaxisorfemorotibialangle(FTA)(Fig.2).

Twenty-sevenpatientswereevaluated,ofwhom24were women(88.9%)and3weremen(11.1%),withameanageof73 yearsand4months(range:from48yearsand5monthsto88 yearsand2months)(Table1).

InrelationtothestagingoftheOA,30knees(63.8%)were classifiedasKellgrenandLawrence19_gradeIII _{and17(36.2%)as} gradeIV_{.AccordingtotheAhlbäckclassification,}20_asmodified byKeyesetal.,21_{fivekneesweregrade}III _{(10.6%),30grade}IV (63.9%)and12gradeV _{(25.5%)(Table1).}

Fig.2–ShortradiographofthekneeinAPview,with weight-bearingontwofeetandusingthetechniqueofFTA measurement.

Inthestatisticalmethodology,theinterandintraobserver concordanceregardingthemeasurementsoftheanatomical axiswereevaluatedusingtheintraclasscorrelationcoefficient (ICC).22_{Thecriterionadoptedfordeterminingsignificancewas}

thelevel of1%.TheanalysiswasprocessedusingtheSPSS statisticalpackage,version13.0.

ItisknownthattheclosertheICCistoone,thestronger (ormoreperfect)theconcordanceisbetweentheobservers.In thiscase,thetechniquesweresimilarfromanumerical (quan-titative)pointofview.Ontheotherhand,theclosertozerothe ICCis,thegreaterthediscordancewillbe,meaningthatthe valuescannotbereproducedandthedifferencesobservedare notrandom.

Through several studies and simulations,it canbe said that:

ICC≤ 0.20–noconcordance; 0.20<ICC≤ 0.40–weakconcordance; 0.40<ICC≤ 0.60–moderateconcordance; 0.60<ICC≤0.80–strong(good)concordance; ICC>0.80–verystrong(excellent)concordance.

Results

Patientnumber Age(years) Rightknee Rightknee Leftknee Leftknee Ahlbäck KellgrenandLawrence Ahlbäck KellgrenandLawrence

1 68.7 4 3

2 67.8 4 3 4 3

3 88.2 5 4 5 4

4 76.4 4 3 5 4

5 61.4 3 3 3 3

6 71.1 4 4

7 82.2 5 4

8 74.2 4 3 5 4

9 74 4 3 4 3

10 72 4 4 4 3

11 65 3 3 4 3

12 74.6 4 4 4 3

13 69.7 4 3 4 3

14 76.9 5 4

15 83.2 5 4

16 74.1 4 3 4 3

17 75.6 4 4 4 3

18 60.7 3 3 3 3

19 71.8 4 3 4 3

20 83.7 5 4 5 4

21 69 4 3 4 3

22 74.3 4 4 5 4

23 85 5 4 5 4

24 72.7 4 3 4 3

25 48.4 4 3 4 3

26 66 4 3

27 85.2 4 3

Source:hospitalfiles,2013.

radiographs,itwas7.7◦_{.Inthefinalmeasurements,themean}

FTA on the short radiographs was 7.5◦ _{and on the long}

radiographs,7.6◦_{.Consideringeachexaminerseparately,the}

anatomicalaxismeasurementvariedbyamaximumof13◦

betweenthelongandshortradiographsandbyamaximum

of6◦ _{betweentheinitialandfinalmeasurements.Fromthe}

statisticalanalysis,itwasobservedthattherewasstrongly sig-nificantconcordance(ICC>0.88,asaminimum)betweenthe evaluationsusingshortandpanoramicradiographs(p<0.001),

Table2–Concordancebetweenradiographs:short versuspanoramic.

Observer ICC 95%CI pValue

Measurement1 RBF 0.885 0.804–0.934 <0.001 GNC 0.915 0.853–0.952 <0.001 MNG 0.941 0.897–0.967 <0.001 LFM 0.914 0.851–0.951 <0.001 RPA 0.945 0.903–0.969 <0.001 Measurement2 RBF 0.928 0.874–0.959 <0.001 GNC 0.944 0.902–0.968 <0.001 MNG 0.953 0.918–0.974 <0.001 LFM 0.916 0.854–0.952 <0.001 RPA 0.945 0.903–0.969 <0.001

Source:hospitalfiles,2013.

ICC,intraclasscorrelationcoefficient;95%CI,95%confidence inter-valforICC.

forallthefiveobserversandforbothofthemeasurements (Table2).

Itwasalsoobservedthattherewasstronglysignificant con-cordance(ICC>0.97,asaminimum)betweenmeasurements 1and2(p<0.001),forallthefiveobserversandforbothtypes ofradiograph(Table3).

Finally,itwasobservedthattherewasstronglysignificant concordance(ICC>0.96,asaminimum)betweenallpairsof observers (p<0.001),forbothtypesofradiographandusing measurements1and2(Tables4and5).

Table3–Intraobserverconcordance:measurement1 (initial)versusmeasurement2(final).

Radiograph Observer ICC 95%CI pValue

Short RBF 0.989 0.980–0.994 <0.001 GNC 0.986 0.975–0.992 <0.001 MNG 0.996 0.992–0.998 <0.001 LFM 0.989 0.980–0.994 <0.001 RPA 0.998 0.997–0.999 <0.001 Panoramic RBF 0.977 0.959–0.987 <0.001 GNC 0.988 0.979–0.994 <0.001 MNG 0.997 0.995–0.999 <0.001 LFM 0.986 0.975–0.992 <0.001 RPA 0.998 0.997–0.999 <0.001

Source:hospitalfiles,2013.

Table4–Interobserverconcordanceformeasurement1(initial).

Radiograph Observer1vs.observer2 ICC 95%CI pValue

Short RBF GNC 0.984 0.972–0.991 <0.001

RBF MNG 0.987 0.977–0.993 <0.001

RBF LFM 0.977 0.959–0.987 <0.001

RBF RPA 0.979 0.963–0.988 <0.001

GNC MNG 0.982 0.968–0.990 <0.001

GNC LFM 0.973 0.952–0.985 <0.001

GNC RPA 0.976 0.957–0.986 <0.001

MNG LFM 0.972 0.951–0.984 <0.001

MNG RPA 0.993 0.988–0.996 <0.001

LFM RPA 0.968 0.943–0.982 <0.001

Panoramic RBF GNC 0.981 0.966–0.989 <0.001

RBF MNG 0.978 0.960–0.987 <0.001

RBF LFM 0.977 0.960–0.987 <0.001

RBF RPA 0.981 0.966–0.989 <0.001

GNC MNG 0.989 0.980–0.994 <0.001

GNC LFM 0.981 0.967–0.989 <0.001

GNC RPA 0.990 0.982–0.994 <0.001

MNG LFM 0.980 0.964–0.989 <0.001

MNG RPA 0.997 0.994–0.998 <0.001

LFM RPA 0.981 0.967–0.989 <0.001

Source:hospitalfiles,2013.

ICC,intraclasscorrelationcoefficient;95%CI,95%confidenceintervalforICC.

Discussion

Theappropriateradiographicmethodforevaluatingpatients withkneeOAisstillamatterofdebate.5,6,9,13–16,18_Panoramic

radiography is traditionally recommended whenthere is a need to assess the lower-limb alignment.1–4,7–13 _Moreland

etal.7_{statedthatitwasessentialformeasuringtheaxial}

align-mentofthelowerlimbs.However,itisdifficulttoperform,

oftenpresentsdeficientquality, exposespatientstogreater amountsofionizingradiationandismoreexpensive.5,6,15

Krausetal.5_{comparedkneealignmentsusingpanoramic}

radiographsonthelower limbsinAPviewandusingshort radiographsinaflexedpositioninposteroanterior(PA)view, andalsocomparedthesewithclinicalmeasurements.They observed that the results from clinical measurements and from short radiographs correlated well with those from panoramicradiographs.Theythereforeconcludedthatthese

Table5–Interobserverconcordanceformeasurement2(final).

Radiograph Observer1vs.observer2 ICC 95%CI pValue

Short RBF GNC 0.989 0.980–0.994 <0.001

RBF MNG 0.990 0.981–0.994 <0.001

RBF LFM 0.980 0.964–0.989 <0.001

RBF RPA 0.982 0.968–0.990 <0.001

GNC MNG 0.990 0.982–0.994 <0.001

GNC LFM 0.987 0.977–0.993 <0.001

GNC RPA 0.983 0.969–0.990 <0.001

MNG LFM 0.982 0.968–0.990 <0.001

MNG RPA 0.992 0.986–0.995 <0.001

LFM RPA 0.970 0.947–0.983 <0.001

Panoramic RBF GNC 0.993 0.988–0.996 <0.001

RBF MNG 0.990 0.982–0.994 <0.001

RBF LFM 0.983 0.970–0.991 <0.001

RBF RPA 0.991 0.984–0.995 <0.001

GNC MNG 0.991 0.983–0.995 <0.001

GNC LFM 0.980 0.964–0.989 <0.001

GNC RPA 0.992 0.985–0.995 <0.001

MNG LFM 0.977 0.959–0.987 <0.001

MNG RPA 0.997 0.994–0.998 <0.001

LFM RPA 0.980 0.964–0.989 <0.001

Source:hospitalfiles,2013.

panoramic radiographs were unavailable.5 _{McGrory et al.}15

were unableto demonstrateany advantageforlong radio-graphsovershortradiographsforpreoperativeplanning.

Furthermore,inageneralmanner,shortradiographson thekneesareindispensableatanyphaseofdegenerativejoint disease.2,5,6,14–18 _{Therefore,if shortradiographscanprovide}

reliableinformationon alignments,panoramic radiographs becomeunnecessary.Thiswasourmotivationforthepresent study.

From a methodological point of view,we attempted as muchaspossibletoreproducethesituationencounteredby orthopedistsintheirdailyclinicalpractice.Thepatients’ posi-tioningwasnotcheckedusingradioscopybeforeproducing theradiographs,giventhatthisisaresourcesfoundinveryfew centersinBrazil.Thepatientsweresimplyinstructedtokeep theirkneesextendedasmuchaspossible,withthepatellae orthogonaltotheX-raytube,soastominimizethepossibility ofrotationaldeviation.

Moreland et al.7 _{postulated that rotation of the lower}

limbsaffectstheapparentalignment.Inkneeswithpoor flex-ion,externalrotationsimulatesanincreaseinvarus,while internal rotation accentuates valgus. This emphasizes the importanceofproperlydirectingthepatellaeforwards,soas toattenuatethisproblem.7_{Similarresultswerepresentedby}

Brouweretal.,13_{whorecommendedthatfluoroscopyshould}

onlybeusedonkneeswithcontractureswhenflexed. Specognaetal.9_{demonstratedthatradiographsproduced}

withweight-bearingononefootwerenotsuperiortothose withweight-bearingonbothfeet,inevaluationson40patients withkneeOAinassociationwithvarusdeformity.Theyeven recommended that weight-bearing on both feet should be used routinely in preoperative assessments.Based on this finding,wealsochosetouseradiographswithweight-bearing onbothfeet.

Withregardtotheresults,it wasobservedthattheFTA measurementson the shortradiographsusing the method described here were concordant with those obtained from longradiographs.Inrelationtothestrengthofconcordance, itwasnoticedthattherewasanimprovementwhenthe mea-surementsweremadeforthesecondtime,probablybecause ofgreater familiaritywith the method presented. Another importantfindingwasthatbetterresultswereobtainedbythe moreexperiencedexaminers inbothmeasurements. How-ever,eventhemeasurementsmadebythelessexperienced examinerspresentedahighconcordanceindex.

Khan et al.6 _{were able to demonstrate an association}

betweentheevolutionofthekneeOAandtheangular devi-ations measuredon shortradiographsusing the technique describedinthepresentstudy.However,theydidnotventure toindicatethisradiographictechniquealoneforpreoperative planningofosteotomy.6

Regarding the interobserver evaluation, it was again observedthatforbothmeasurements,therewasgreater con-cordance(i.e.greaterICC)betweenthetwoexaminerswith greaterexperience.However,independentofthelevelof expe-rience,therewashighconcordancebetweenallthepairsof examiners.

Finally,theintraobserverconcordancepresentedthesame behavior as seen in the preceding evaluation, with high

relationobtainedamongthosewithgreatestexperience. Thus, the resultsfrom the present study demonstrated that themethod proposedformeasuringthe FTA onshort radiographswasreliableandreproducible,independentofthe experienceoftheexaminingphysician.Othercorrelated eval-uationswouldservetostrengthenthedataseeninthepresent studyandwouldopenuptheprospectofsimplifying evalua-tionsontheangulardeviationsofthelowerlimbsinpatients withkneeOA.

Conclusions

Under the conditionsofthis study,shortradiographs were equaltopanoramicradiographsforevaluatingthe anatomi-calaxisofthelowerlimbsinpatientswithadvancedOA.The measurementusedalsoshowedhighinterandintraobserver concordanceandreproducibility.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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