A reference method for the evaluation of femoral head joint center location technique based on external markers

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To cite this version :

Hélène PILLET, Morgan SANGEUX, Jérôme HAUSSELLE, Rami EL RACHKIDI, Wafa SKALLI

-A reference method for the evaluation of femoral head joint center location technique based on

external markers - Gait and Posture - Vol. 39, p.655-658 - 2014

Any correspondence concerning this service should be sent to the repository

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A

reference

method

for

the

evaluation

of

femoral

head

joint

center

location

technique

based

on

external

markers

He´le`ne

Pillet

a,

*

,

Morgan

Sangeux

b,c,d

,

Je´roˆme

Hausselle

a

,

Rami

El

Rachkidi

a

,

Wafa

Skalli

a

a_Arts_et_Metiers_ParisTech,_LBM,₁₅₁_bd_de_l’hopital,₇₅₀₁₃_Paris,_France b

RoyalChildren’sHospital,Melbourne,Australia

c

UniversityofMelbourne,SchoolofEngineering,Australia

d

MurdochChildrenResearchInstitute,Melbourne,Australia

1. Introduction

Anaccuratemethodofjointcenterlocalizationisessentialfor kinematic and kineticcalculations in movementanalysis [1].To estimatethelocationofthehipjointcenter(HJC),previousstudies haveusedpredictive[2,3],functional[4,5]ormedicalimagebased

[6–9] methods. Predictive and functional methods offer easy integration into existing clinical assessment but their accuracy needs to be established before implementation. Medical image basedtechniquesmayprovideaccurate3Dpositionofjointcenters inthecoordinatesystemoftheimagingdevice.Tobeuseful,these coordinatesneedtoberegisteredtothepelviscoordinatesystem deﬁnedformovement analysisfromexternalskinmarkers. This criticalstepraisestwoissues.First,whenexternalmarkerswere notavailableonthemedicalimages,researchershavetoassumethat externalmarkerswereexactlypositionedoverbonylandmarksthat canbelocalizedonthemedicalimages.Anydiscrepancybetween externalmarkerspositionsandbonylandmarksaffectstheaccuracy of theHJCscoordinatesinthe pelviccoordinatesystem.Second, whenexternalmarkerswereavailableonthemedicalimages,the subjects’postureintheimagingdevicemaybedifferenttothestatic calibrationpostureformovementanalysis.Forexample,whenthe

subjectsarelyingsupine[6]majorbiasmaybeexpectedfromsoft tissueartifactbetweenthelyingsupineandstandinguppostures.

Inthiscontext,anewsystem,EOS1

(EOSImaging–France), basedonlow-dosebi-planarX-raystakeninastandingposition

[10]togetherwithexternalmotioncapturemarkersmayserveas areference.Imagesfromthissystemareusedtoreconstruct3D bonesmodelswhichcanberegisteredtoexternalmarkersandin theappropriatesubject’spostureforstaticcalibration.Itisthen possibletoassesstherelationshipbetweentheexternalmarkers based coordinate systems and the bones models. In clinical routine,thesystematicuseofX-rays,evenlowdose(6–9times lessthan conventionalX-rays),remains problematic.However, depending on the accuracy, it may be suitable to validate alternativemethodsofHJCslocalization.Theaimofthepresent study was to evaluate the accuracy of hip joint center (HJC) localizationusingtheEOS1

system.

2. Materialandmethod

2.1. Subjects

Seventeenvolunteers(11malesand6females)were consid-ered after informed consent and ethical committee approval. Subjectshadameanweightof75.8kg(range54.3–102kg),mean height1.74m(range1.52–1.92m)andBodyMassIndexes(BMI) rangedfrom17to33. Keywords: BiplanarX-rays EOS Gaitanalysis Biomechanics Jointcenter ABSTRACT

Accuratelocalizationofjointcentersisessentialinmovementanalysis.However,jointcenterscannotbe directlypalpatedandalternativemethodsmustbeused.Toassesstherelativemeritsofthesemethods,a medicalimagebasedreferenceshouldbeused.TheEOS1

system,anewlowdosebi-planarX-rays imagingtechniquemaybeconsidered.Theaimofthisstudywastoevaluatetheaccuracyofhipjoint center(HJC)localizationusingtheEOS1

system.Seventeenhealthyyoungadultsparticipatedinthe study.FemoralheadsandpelvicexternalmarkerswerelocalizedusingtheEOS1

systemandtheHJCs wereexpressedinthemovementanalysiscoordinatesystem.Resultsshowedthatexternalmarker localizationwasreliablewithin0.15mmfortrainedassessors.MeanaccuracyforHJClocalizationwas 2.9mm(SD:1.3,max:6.2).TheEOSbasedmethodthereforeappearedreliableandmaybeusedfor femoralheadlocalizationorasareferencetoassesstheaccuracyofothermethodsforHJClocalization.

* Correspondingauthor.Tel.:+33144246338;fax:+33144246366. E-mailaddress:helene.pillet@ensam.eu(H.Pillet).

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2.2. Protocol

Volunteerswereequippedwithfour14mmreﬂectivemarkers placedontheanteriorandposterioriliacspinelandmarksofthe pelvis.Foreachsubject,twoacquisitionsweretakenwiththeEOS1

(Fig.1)inastandardstandingposturedescribedbyChaibietal.

[11].EachacquisitionconsistedoftwosimultaneousX-rayimages in the sagittal and coronal plane.Acquisitions were performed 5minaparttoallowthesystemtocooldown.Three-dimensional reconstructionofthefemurwasperformedasdescribedbyChaibi et al.[11].Asphere wasﬁttedin theleastsquare sensetothe femoral head regionof themodel tolocalize thefemoral head centerintheEOS1

coordinatesystem.Threedimensionalpositions ofthepelvicmarkerswerealsocomputed:theprojectedimagesof a14mmdiameterspheremodelweremanuallyadjustedonthe twosetsofbi-planarX-raystomatchreﬂectivemarkerscontours.

2.3. Repeatabilityofmarkersidentiﬁcation

Datafrom4ofthesubjectswereused(1maleand1femalewith aBMI>25,1maleand1femalewithaBMI<25).Markersfrom theﬁrstpairofimageswereconsidered.Twotrainedoperators (bioengineers)independentlyplacedthreetimestheentiresetof markers.ThemethoddescribedbyGlu¨eretal.[12]wasusedto calculatetheinter-operatorrepeatabilityofmarkerlocalizationon theimages.

2.4. Accuracyoffemoralheadregistration(Fig.2)

The right and left femoral heads were localized for each acquisition(FH1EOS1andFH2EOS2).Wecalculatedthe

transforma-tiontomapthepelvicmarkersfromtheﬁrstacquisitiontothe

secondacquisitionintheleastsquaresense[13].The transforma-tionwasthenappliedtothepositionofthefemoralheadfromthe ﬁrstacquisitiontomapitontothesecondacquisitionwhichgives FH1EOS2.Accuracyofthefemoralheadregistrationwascalculated

asDFH,thedistancebetweenFH1EOS2 andFH2EOS2.Itshouldbe

notedthatDFHincludesaccuracyoffemoralheadlocalizationand

repeatabilityofpelvismarkerslocalization.

3. Resultsanddiscussion

Inter-operatorvariabilityinmarkerslocalizationwas0.15mm. Uncertaintywasmainlyrelatedtovisibilityofsomeofthemarkers duetoboneormarkersuperposition,andsometimestothelackof sphericityof themarkers ontheimages.ThedistanceDFHwas

homogeneousforleftand rightHJCand2.9mminaverage(SD: 1.3).Therewasonlyoneoutlier(6.2mm,Table1,S8left)over34 measurements.

TheEOSmethodappearsmorereliablethanotherpublished methods. Ina recent studydescribing a 3D ultrasoundmethod

[14], authors reported an accuracy of 4mm for the distance betweentheleftandrightfemoralheadswithrespecttomagnetic resonanceimaging(MRI).However,sinceMRIimagesweretaken lyingsupineandexternalmotioncapturemarkerscannotbeseen ontheimages,theauthorswereunabletoassesstheaccuracyof thefemoralheadlocalizationwithrespecttothepelviccoordinate system.Leardinietal.usedasimilartechniquebasedX-ray(called RSA)tocomparethepositionoftheHJCoutputbypredictiveand functional methods [4]. The authors reported a comparable accuracy for the marker localization (0.2mm) from the RSA technique but didnot reporttheaccuracy of thefemoral head localization.However,thetechnique describedinLeardinietal. studyinvolveslevelsofionizingradiationthataretoohightobe

Fig.1.Twopairsofradiographiesforonesubject(theﬁrstpaircenteredontherightlowerlimbandthesecondpaircenteredontheleftlowerlimb).Pelvismarkersarevisible onbothX-rays.

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used in extensive data collection and necessitated the use of tantalum ballsinstead ofexternal markers. Itis only since the EOS1

system, with low dose radiation, that such stereoradio-graphytechniquesmaybeenvisagedforextensivestudies.

Typicalaccuracyofnon-imagebasedmethodstolocatethehip joint center range from 13mm to 30mm [15]. The current technique,withanaverageand directlycomparableaccuracyof 2.9mminaverage seemsappropriatetoserveasa reference.A greatadvantageofthisapproach,i.e.simultaneousvisualizationof femoral headand externalmarkers,is thatit isnotaffectedby

subjectspeciﬁcitiessuchasBMIorunusualanatomy.Ittherefore constitutesastrongbaseeitherfordirectmeasurementofthehip jointcenterorforevaluationofalternativemethodsofestimation.

Acknowledgments

TheauthorsaregratefultoVICON(OMG-UK)fortheloanofa motioncapturesystemnecessaryfortheoverallstudy.

Conﬂictofintereststatement

Theauthorsdonothaveanyﬁnancialorpersonalrelationships with other people or organizations that could inappropriately inﬂuencethemanuscript.

References

[1]StagniR,LeardiniA,CappozzoA,BenedettiMG,CappelloA.Effectsofhipjoint centremislocationongaitanalysisresults.JBiomech2000;33:1479–87.

[2]BellAL,PedersenDR,BrandRA.Acomparisonoftheaccuracyofseveralhip centerlocationpredictionmethods.JBiomech1990;23:617–21.

[3]DavisRB,OunpuuS,TyburskiD,GageJR.Agaitanalysisdatacollectionand reductiontechnique.HumMovSci1991;10:575–87.

[4]LeardiniA,CappozzoA,CataniF,Toksvig-LarsenS,PetittoA,SforzaV,etal. Validation ofa functionalmethodfortheestimation ofhip jointcentre location.JBiomech1999;32:99–103.

[5]EhrigRM,TaylorWR,DudaGN,HellerMO.Asurveyofformalmethodsfor determiningfunctionaljointaxes.JBiomech2007;40:2150–7.

[6]OtakeY,SuzukiN,HattoriA,HagioK,SuganoN,YonenobuK,etal. Four-dimensionalmodel ofthelower extremityafter total hiparthroplasty.J Biomech2005;38:2397–405.

[7]KawakamiH,SuganoN,YonenobuK,YoshikawaH,OchiT,HattoriA,etal.Gait analysissystemforassessmentofdynamicloadingaxisoftheknee.Gait Posture2005;21:125–30.

[8]OhnishiT,SuzukiM,NawataA,NaomotoS,IwasakiT,HaneishiH. Three-dimensionalmotionstudyoffemur,tibia,andpatellaatthekneejointfrom bi-planeﬂuoroscopyandCTimages.RadiolPhysTechnol2010;3:151–8.

Fig.2.Schematicoftheprocesstoobtainaccuracydata.

Table1

Accuracyofpelvismarkersbasedregistrationofthefemoralheadfor17subjects: distance(mm)betweenthefemoralheadregisteredfrompelvismarkersandthe femoralheadcomputedfromthefemurmodelforrightandleftsides.

Subjects Distanceforthe rightfemoralhead(mm)

Distancefortheleft femoralhead(mm) 1 2.0 3.2 2 3.7 3.6 3 3.2 1.8 4 3.3 2.7 5 0.7 1.5 6 2.8 1.7 7 2.1 1.5 8 3.0 6.2 9 1.0 1.8 10 4.5 4.4 11 0.9 2.5 12 3.8 2.8 13 4.7 4.5 14 4.2 2.1 15 4.1 3.7 16 1.7 3.0 17 3.0 3.6 Mean 2.9 3.0 Max 4.7 6.2

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[9]SholukhaV,LeardiniA,SalviaP,RoozeM,SintSV.Double-stepregistrationof invivostereophotogrammetrywithbothinvitro6-DOFselectrogoniometry andCTmedicalimaging.JBiomech2006;39:2087–95.

[10]DuboussetJ,CharpakG,SkalliW,DeguiseJ,KalifaG.EOS:Anewimaging systemwithlowdoseradiationinstandingpositionforspineandbone&joint disorders.JMusculoskeletRes2010;13:1–12.

[11]ChaibiY,CressonT,AubertB,HausselleJ,NeyretP,HaugerO,etal.Fast3D reconstructionofthelowerlimbusingaparametricmodelandstatistical inferencesandclinicalmeasurementscalculationfrombiplanarX-rays. Com-putMethodsBiomechBiomedEng2012;15:457–66.

[12]Glu¨erCC,BlakeG,LuY,BluntBA,JergasM,GenantHK.Accurateassessmentof precisionerrors:howtomeasurethereproducibilityofbonedensitometry techniques.OsteoporosInt1995;5:262–70.

[13]So¨derkvistI,WedinPA.Determiningthemovementsoftheskeletonusing well-conﬁguredmarkers.JBiomech1993;26:1473–7.

[14]PetersA,BakerR,SangeuxM.Validationof3-Dfreehandultrasoundforthe determinationofthehipjointcentre.GaitPosture2010;31:530–2.

[15]Sangeux M, Peters A, Baker R. Hip joint centre localization: evaluation onnormalsubjectsinthecontextofgaitanalysis.GaitPosture2011;34: 324–8.