Rev. bras. ortop. vol.51 número2

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

Original

Article

Overdiagnosing

of

femoroacetabular

impingement:

correlation

between

clinical

presentation

and

computed

tomography

in

symptomatic

patients

夽

Richard

Prazeres

Canella

,

Guilherme

Pradi

Adam

,

Roberto

André

Ulhôa

de

Castillo

,

Daniel

Codonho

_,

_Gerson

_Gandhi

_Ganev

_,

_Luiz

_Fernando

_de

_Vicenzi

a_{ImperialHospitaldeCaridade,Florianópolis,SC,Brazil}

b_{ClínicaImagem,Florianópolis,SC,Brazil}

c_{HospitalGovernorCelsoRamos,Florianópolis,SC,Brazil}

d_{CentrodePesquisasOncológicas(CEPON),Florianópolis,SC,Brazil}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received24March2015 Accepted12May2015

Availableonline16February2016

Keywords:

Hip

Femoroacetabularimpingement X-raycomputedtomography

a

b

s

t

r

a

c

t

Objective:Tocorrelatetheanglesbetweentheacetabulumandtheproximalfemurin symp-tomaticpatientswithfemoroacetabularimpingement(FAI),usingcomputedtomography (CT).

Methods:Weretrospectivelyevaluated103hipsfrom103patients,usingmultisliceCTto measuretheacetabularage,acetabularversion(initssupraequatorialportionandinits middlethird),femoralneckversion,cervical-diaphysealandalphaanglesandtheacetabular depth.Forthestatisticalanalysis,weusedthePearsoncorrelationcoefficient.

Results:Therewereinversecorrelationsbetweenthefollowingangles:(1)acetabular cov-erageversusalphaangle(p=0.019);(2)acetabularversion(supraequatorial)versusalpha angle(p=0.049).Forpatientswithfemoralanteversionlowerthan15degrees:(1)acetabular version(supraequatorial)versusalphaangle(p=0.026);(2)acetabularversion(middlethird) versusalphaangle(p=0.02).Forpatientswithacetabularversion(supraequatorial)lower than10degrees:(1)acetabularversion(supraequatorial)versusalphaangle(p=0.004);(2) acetabularversion(middlethird)versusalphaangle(p=0.009).

Conclusion:Therewasastatisticallysignificantinversecorrelationbetweentheacetabular versionandalphaangles(thesmallertheacetabularanteversionanglewas,thelargerthe alphaanglewas)insymptomaticpatients,thussupportingthehypothesisthatFAIoccurs whencamandpincerfindingsduetoacetabularretroversionareseensimultaneously,and thatthelatteralonedoesnotcauseFAI,whichleadstooverdiagnosisinthesecases.

©2015SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

夽

WorkperformedintheImperialHospitaldeCaridade,Florianópolis,SC,Brazil.

∗ _{Correspondingauthor.}

E-mail:[email protected](R.P.Canella).

http://dx.doi.org/10.1016/j.rboe.2016.02.001

Sobrediagnóstico

do

impacto

femoroacetabular:

correlac¸ão

entre

a

clínica

e

a

tomografia

computadorizada

em

pacientes

sintomáticos

Palavras-chave:

Quadril

Impactofemoroacetabular Tomografiacomputadorizada porraiosX

r

e

s

u

m

o

Objetivo:Correlacionar,portomografiacomputadorizada(TC),osângulosentreoacetábulo eofêmurproximalempacientessintomáticoscomimpactofemoroacetabular(IFA).

Métodos: Avaliamos,retrospectivamente,103quadris(103pacientes)emedimosporTC

multisliceosângulosdecoberturaacetabular,deversãoacetabular(emsuaporc¸ão suprae-quatoriale noseu terc¸omédio),de versãodocolofemoral,cervicodiafisário,alfae de profundidadeacetabular.Paraanáliseestatística,usamosocoeficientedecorrelac¸ãode Pearson.

Resultados:Houvecorrelac¸ãoinversaentreosângulos:1)coberturaacetabularversusângulo alfa(p=0,019);2)versãoacetabular(supraequatorial) versusânguloalfa(p=0,049).Para pacientescomanteversãofemoralmenordoque15◦_{:1)versãoacetabular(supraequatorial)} versusânguloalfa(p=0,026);2)versãoacetabular(terc¸omédio)versusânguloalfa(p=0,02). Parapacientescomversãoacetabular(supraequatorial)menordoque10◦_:1)versão

acetab-ular(supraequatorial)versusânguloalfa(p=0,004);2)versãoacetabular(terc¸omédio)versus

ânguloalfa(p=0,009).

Conclusão: Hácorrelac¸ãoinversaestatisticamentesignificativaentreosângulosdeversão acetabulareoânguloalfa(quantomenoroângulodeanteversãoacetabular,maioroângulo alfafemoral)empacientessintomáticos.Issoreforc¸aahipótesedequeoIFAocorrequando hásimultaneamenteosachadosdecamepincerporretroversãoacetabularequeessenão causaoIFAisoladamente,oquelevaasobrediagnósticonessescasos.

©2015SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Todososdireitosreservados.

Introduction

Recentadvancesinunderstandingtheanatomyand biome-chanicsofthecoxofemoraljointhaveshownthat morpholog-icalalterationstothehiporactivitieswithexcessiverange ofmotionthatleadtorepetitivecontactbetweenthefemoral neckandtheacetabularrimmayleadtoaprogressive degen-erativeprocessandearlyosteoarthrosisofthehip.1

Reinhold Ganz2,3 _{was the main author responsible for}

describingfemoroacetabularimpingement(FAI)anditstwo subtypes:camandpincer.Cam-likeimpingementiscausedby aboneprominenceatthecervicocapitaljunction,whichleads tolossofthenormalsphericityofthefemoralhead. Pincer-likeimpingementiscausedbyexcessiveacetabularrooforby acetabularretroversion.AccordingtoBecketal.,4_both

sub-typesarepresentin86%ofthepatientsdiagnosedwithFAI. Sofar,littleisknownaboutthecauseandnaturalhistory oftheseanatomicalalterations.5_{Itisunderstoodthatthere}

isa dynamic interaction between the proximalfemur and theacetabulum,6,7_{whichbeginsattheembryonicstage}8_with

endochondralossificationregulatedbyintrauterinepressure andcontinuesuntiladulthood.Thejointremodelingdepends onthemechanicalstresstowhichthehipisexposed.9_Thus,

variationsintheacetabularangle10,11_{and/ortheangleofthe}

proximalfemur12,13_{wouldleadtoearlyjointdamage.}

However,ithasrecentlybeensuggestedthatpincer-likeFAI isdiagnosedexcessively.14,15 _{Inastudyinwhichthe}

angu-larrelationshipbetweentheacetabulumandproximalfemur wascorrelated amongasymptomaticpatients,thepresence ofposterior angling of the acetabulum was thought to be

presentduetocompensationofthefemoralanatomyduring hipdevelopment.15_{Inananalysisonhipspresentingthecam}

andpincertypes,itwasobservedthattherewasnosignificant differenceinacetabularversionincomparisonwithnormal hips.Thissuggeststhatacetabularretroversionwouldnotbe theonlycauseofFAI.14

Ourstudyhadtheaimofusingmultislicecomputed tomo-graphy(CT)tocorrelatetheanglesbetweentheacetabulum andtheproximalfemur,insymptomaticpatientswithFAI.

Methods

Ourstudywasanalyzedandapprovedbytheresearchethics committeeofourinstitution.Weselected103patientswho underwent multisliceCT ontheir hipsbetweenMarch and December2010,becauseofclinicalsuspicionof femoroacetab-ularimpingement.Allofthesepatientspresentedcomplaints ofpaininthehipjointandtestedpositiveforanteriorimpact inphysicalexaminationmaneuversat90degreesofflexion combinedwithadductionandinternalrotation.

Dataonthesepatients’acetabularandfemoralangleswere gatheredand subjectedtostatisticalanalysis.Noexclusion criteriawereused.Thepatients’meanagewas37years(range: 16–68);21weremenand82werewomen.

Fig.1–Tomographicmeasurementoftheacetabularroof angleusingChen’smethod.

ofgadotericacid.Followingthis,magneticresonance imag-ing(MRI) wasalsoperformed,using aGEInfinitymachine. AxialT1sequenceswithfatsaturationinthefemoralneck, sagittaland coronalsequencesofthickness0.3cm, coronal STIRsequencesofthickness0.5cmandaxialprotondensity sequenceswithfatsaturationwereproduced.Thefollowing angles were measured: acetabular roofangle using Chen’s method (Fig. 1); acetabular version angle in its cranial or supraequatorialportion(Fig.2)andinitsmiddlethird(Fig.3); alphaangleofthecervicocapitaljunctionofthefemur(Fig.4); cervicodiaphysealangle(Fig.5);acetabulardepth(Fig.6);and femoralneckversionangle(Fig.7).

Themeasurements were made on the multislice tomo-graphyimages,inanADW4.3workstation.Thealphaangle ofthecervicocapitaljunctionofthefemurwasevaluatedby meansofanoblique axialplanethat crossedthe centerof thefemoralneck,usingcoronalreformattingasthereference. Measurementsofthealphaangleandthemiddlethirdofthe acetabularversion werethenmadeonthe imageobtained, inaccordancewiththestudybyKamathetal.16_However,we

Fig.2–Tomographicmeasurementoftheversionanglein thecranialorsupraequatorialportionoftheacetabulum.

Fig.3–Tomographicmeasurementoftheversionanglein themiddlethirdoftheacetabulum.

alsoincludedmeasurementsoftheangleofversionofthe cra-nialportionoftheacetabulum,becauseoftheimportanceof thislocationinthegenesisoftheimpactandfor differenti-ationoftheoverallretroversionoftheacetabulumfromthe retroversionofitscranialportionalone.

Tomeasuretheacetabularanteversion,imagesintheaxial planewereused,withcorrectionofpossiblepelvictilt,and linestangentialtotheanteriorandposteriorbordersofthe acetabulumweretracedoutatthelevelsofthecenterofthe femoral head and the top ofthe femoralhead. Theangle betweentheselinesandthesagittalplanewasmeasured.

To measure the acetabular roof angle, the technique describedbyChenetal.wasused.17_{Thisinvolvedusingan}

image in the coronal plane that crossed the acetabula, in which the fundus ofthe acetabulum took on a“teardrop” appearance.Onthisimage,twolinesmeetingatthecenter ofthefemoralheadweretracedout:oneoriginatingatthe borderoftheacetabulumandtheotherparalleltotheaxial axisofthepelvis.

Fig.5–Tomographicmeasurementofthe cervicodiaphysealangle.

Theangleoffemoralneckversionwasmeasuredbymeans of3Dreconstructionofthefemur.Viewingfromabove,two linesweretracedout:onecrossingthecenterofthefemoral neckandtheother,tangentialtotheposteriorportionofthe femoralcondyles.Thecervicodiaphysealanglewasmeasured onthe3Dreconstructionusingananteriorview.Inamanner similartomeasurementsonradiographs,onelinewastraced outalongtheaxisofthefemoraldiaphysisandanotheralong theaxisofthefemoralneck,andtheanglebetweenthemwas measured.

Toanalyzethedataobtainedbymeansofdescriptive statis-tics,weusedPearson’scorrelationcoefficient,takingp<0.05 assignificant.

Results

Table1presentstheanalysisonallthepatientsstudied.From

this,astatisticallyinversecorrelation(p<0.05)wasobserved

Fig.6–Tomographicmeasurementoftheacetabulardepth.

Fig.7–Three-dimensionalreconstructionofthefemur, withsubtractionoftheremainderofthebonestructuresin ordertomeasurethefemoralneckversion.

through cross-correlatingthe values ofthe acetabularroof angle versus the alpha angle and angle of version of the cranialorsupraequatorialportionoftheacetabulumversus thealphaangle.Nostatisticalcorrelationwasobservedupon cross-correlatingtheremainingvalues.

InTable2,onlythepatientswithfemoralanteversionless

than 15 degrees were selected. Once again, a statistically significant inverse correlation (p<0.05) was observed upon cross-correlatingthevaluesoftheangleofversionofthe cra-nialorsupraequatorialportionoftheacetabulumversusthe alphaangle.Inthisevaluation,therewasalsoaninverse cross-correlationbetweentheangleofversionofthemiddlethird oftheacetabulumandthealphaangle.Theother numbers evaluateddidnotpresentstatisticalvalue.

InTable3,onlythepatientswithversionoflessthan10

degreesinthecranialorsupraequatorialportionofthe acetab-ulum were selected. In relationto Table 2, we observed a strongerstatisticallyinversecorrelation(p<0.005)upon cross-correlatingthevaluesoftheangleofversionofthecranialor supraequatorialportionoftheacetabulumversusthealpha angleandangleofversionofthemiddlethirdofthe acetabu-lumversusthealphaangle.Theothernumbersevaluateddid notpresentstatisticalvalue.

Fig.8showsthestatisticallysignificantinversecorrelation betweenthesupraequatorialacetabularversionandthealpha angleamongthepatientsselectedinTable3,ingraphform.In otherwords,thesmallertheangleofacetabularanteversion was,thelargerthefemoralalphaanglewas,insymptomatic patients.

Discussion

Moynihan et al.18 _{warned about the potential for}

Table1–Statisticalanalysison103patients,inwhichn=numberofpatientsanalyzedandp<0.05suggestsstatistical significance.

Center-edge angle(Chen)

Acetabular depth

Cranial acetabular

version

Middle-third acetabular

version

Cervicodiaphyseal angle

Alphaangle Femoral versionangle

Center-edgeangle(Chen)

Pearson’scorrelation 1 −0.159 0.45 0.097 −0.046 −0.231 −0.029

p 0.109 0 0.328 0.646 0.019 0.775

n 103 103 103 103 103 103 103

Acetabulardepth

Pearson’scorrelation −0.159 1 −0.352 −0.377 0.274 0.14 0.025

p 0.109 0 0 0.005 0.159 0.8

n 103 103 103 103 103 103 103

Cranialacetabularversion

Pearson’scorrelation 0.45 −0.352 1 0.493 −0.103 −0.194 −0.001

p 0 0 0 0.302 0.049 0.989

n 103 103 103 103 103 103 103

Middle-thirdacetabularversion

Pearson’scorrelation 0.097 −0.377 0.493 1 0.06 −0.183 0.089

p 0.328 0 0 0.547 0.065 0.372

n 103 103 103 103 103 103 103

Cervicodiaphysealangle

Pearson’scorrelation −0.046 0.274 −0.103 0.06 1 0.099 −0.019

p 0.646 0.005 0.302 0.547 0.318 0.846

n 103 103 103 103 103 103 103

Alphaangle

Pearson’scorrelation −0.231 0.14 −0.194 −0.183 0.099 1 0.104

p 0.019 0.159 0.049 0.065 0.318 0.294

n 103 103 103 103 103 103 103

Femoralversionangle

Pearson’scorrelation −0.029 0.025 −0.001 0.089 −0.019 0.104 1

p 0.775 0.8 0.989 0.372 0.846 0.294

n 103 103 103 103 103 103 103

10.00

5.00

.00

–5.00

–10.00

–15.00

30.00 40.00 50.00 60.00 70.00 80.00

Alpha angle

Cranial acetabular angle

Observed

r=–0.477 p=0.004 n=35

Linear R2 _Linear=0.228

Fig.8–Correlationbetweensupraequatorialacetabular versionandalphaangleintheselectedpatientsofTable3.

Thereisafundamentalaimtodiscriminatebetterbetween benign“abnormalities”andthosethatwillprogressandcause harm.Likeinthespine,thereishighprevalenceof “abnormal-ities”inthehipregion.MRImayshowalterationsthatarenot clinicallyimportant,thusalsoleadingtooverdiagnosis.19

Most cases of femoroacetabular impingement (FAI) are considered tobeprimary, i.e.ofunknowncause.Hipswith symptomaticFAIdifferfrom“normal”hipsduetoa combina-tionoffactorssuchasmorphology,vulnerabilityofthelabrum andcartilageanddemandsplacedonthehips,inrelationto activitylevelandrangeofmotion.19

Cam-like FAIisrecognizedas afactor thatcauses early osteoarthrosis ofthe hip,through injury tothe joint carti-lageandlabrum,whichleadstofunctionalincapacityinyoung adultpatientswithanactivelifestyle.20

Abnormalities at the head-neck junction in skeletally matureindividualshavebeencorrelatedwithhip osteoarthro-sis. This has been demonstrated in cases of proximal epiphyseal slippage of the femur and in cases of fractur-ingofthefemoralneckwithconsolidationpresentingslight rotationaldeformity.12,21 _{Theorigin ofthesemorphological}

alterations remains unknown,19 _{but somestudies}15,22 _have

Table2–Statisticalanalysiswithselectionofthepatientswithfemoralanteversionoflessthan15degrees.

Center-edge angle(Chen)

Acetabular depth

Cranial acetabular

version

Middle-third acetabular

version

Cervicodiaphyseal angle

Alphaangle Femoral versionangle

Center-edgeangle(Chen)

Pearson’scorrelation 1 −0.187 0.333 0.067 0.054 −0.176 −0.212

p 0.219 0.025 0.661 0.727 0.248 0.161

n 45 45 45 45 45 45 45

Acetabulardepth

Pearson’scorrelation −0.187 1 −0.443 −0.409 0.164 0.238 0.017

p 0.219 0.002 0.005 0.282 0.116 0.911

n 45 45 45 45 45 45 45

Cranialacetabularversion

Pearson’scorrelation 0.333 −0.443 1 0.49 −0.003 −0.331 0.018

p 0.025 0.002 0.001 0.983 0.026 0.906

n 45 45 45 45 45 45 45

Middle-thirdacetabularversion

Pearson’scorrelation 0.067 −0.409 0.49 1 −0.003 −0.346 0.04

p 0.661 0.005 0.001 0.984 0.02 0.794

n 45 45 45 45 45 45 45

Cervicodiaphysealangle

Pearson’scorrelation 0.054 0.164 −0.003 −0.003 1 −0.009 −0.034

p 0.727 0.282 0.983 0.984 0.954 0.827

n 45 45 45 45 45 45 45

Alphaangle

Pearson’scorrelation −0.176 0.238 −0.331 −0.346 −0.009 1 0.002

p 0.248 0.116 0.026 0.02 0.954 0.992

n 45 45 45 45 45 45 45

Femoralversionangle

Pearson’scorrelation −0.212 0.017 0.018 0.04 −0.034 0.002 1

p 0.161 0.911 0.906 0.794 0.827 0.992

n 45 45 45 45 45 45 45

n,numberofpatientsanalyzed. p<0.05suggestsstatisticalsignificance.

Hogervorst21_{suggestedthatthesealterationsoccurredatthe}

endofgrowth.

ComputedtomographyisusefulforevaluatingFAIbecause it enables measurement of angles with clear anatomical referencesandreducestheinterobserverdiscrepancies. Mea-surementoffemoralversionisdonemoreeasilyandprecisely throughtomographythanthroughconventionalradiography. Tomographyalsoenablescorrelationofpositioningerrors dur-ing thepost-processing. Another advantageoftomography isthe3Dreconstructionsthat canbemade,whichprovide detailedmodelsthatareveryusefulforpreoperativeplanning. Themainprobleminmakingevaluationsusingtomography isthefactthatpatientsareevaluatedinthedecubitus posi-tionandtheremaybechangestopelvictiltinrelationtothe uprightstandingposition.23,24

Inourstudy,wereproducedourdailypracticeregarding investigationofFAI.CTisrequestedandthefollowingare rou-tinelymeasured:acetabularroofangleusingChen’smethod; angleofversionofthecranialorsupraequatorialportionof theacetabulumandinthemiddlethird;alphaangleofthe cervicocapitaljunctionofthefemur;cervicodiaphysealangle; acetabulardepth;andangleofversionofthefemoralneck.

Buller et al.15 _{evaluated 230 hips of 115 asymptomatic}

patientsbymeansof3Dreconstructionsoftware.Theangle ofversionofthefemoralneck,cervicodiaphysealangle,angle of version and inclination of the acetabulum and center-edgeangle were measured.They showedthat therewas a positivecorrelationbetweentheanglesoffemoraland acetab-ularversionandconcludedthatcompensationbetweenthe femurandacetabulumoccurredduringjointformation.The present study suggests that in some patients in whom it was believed thatpathological retroversion ofthe acetabu-lum(pinceraction)wasoccurring,theproximalfemurwould compensateforthis.Thesepatientswerethuswronglybeing diagnosedwithFAI.ThedifferencebetweenBuller’sstudyand oursisthatweevaluatedasymptomaticpopulation,i.e.all ofour patientshad undergoneexaminationdue toclinical suspicionofFAI.

Tönnis and Heinecke22 _{demonstrated the relationship}

Table3–Statisticalanalysiswithselectionofthepatientswithversionofthecranialorsupraequatorialacetabulumof lessthan10degrees.

Center-edge angle(Chen)

Acetabular depth

Cranial acetabular

version

Middle-third acetabular

version

Cervicodiaphyseal angle

Alphaangle Femoral versionangle

Center-edgeangle(Chen)

Pearson’scorrelation 1 −0.236 0.25 0.14 0.043 −0.151 −0.334

p 0.172 0.148 0.423 0.807 0.387 0.05

n 35 35 35 35 35 35 35

Acetabulardepth

Pearson’scorrelation −0.236 1 −0.305 −0.266 0.146 0.227 0.051

p 0.172 0.074 0.122 0.402 0.189 0.769

n 35 35 35 35 35 35 35

Cranialacetabularversion

Pearson’scorrelation 0.25 −0.305 1 0.146 −0.043 −0.477 −0.175

p 0.148 0.074 0.402 0.807 0.004 0.314

n 35 35 35 35 35 35 35

Middle-thirdacetabularversion

Pearson’scorrelation 0.14 −0.266 0.146 1 0.038 −0.434 −0.007

p 0.423 0.122 0.402 0.828 0.009 0.967

n 35 35 35 35 35 35 35

Cervicodiaphysealangle

Pearson’scorrelation 0.043 0.146 −0.043 0.038 1 0.053 −0.135

p 0.807 0.402 0.807 0.828 0.764 0.439

n 35 35 35 35 35 35 35

Alphaangle

Pearson’scorrelation −0.151 0.227 −0.477 −0.434 0.053 1 0.045

p 0.387 0.189 0.004 0.009 0.764 0.799

n 35 35 35 35 35 35 35

Femoralversionangle

Pearson’scorrelation −0.334 0.051 −0.175 −0.007 −0.135 0.045 1

p 0.05 0.769 0.314 0.967 0.439 0.799

n 35 35 35 35 35 35 35

n,numberofpatientsanalyzed. p<0.05suggestsstatisticalsignificance.

acetabulum.Inaddition,theynotedthatnormalorincreased femoralanteversionwasgenerallycompensatedfor,through diminishedacetabularversion,andviceversa.

Neppleetal.25_{observedthatthegeneralprevalenceofcoxa}

profundawas55%amonghipsinfourgroups(dysplastichips, hipswithresidualdeformitiesfromLegg-Calvé-Perthes dis-ease,hipswithFAIandasymptomatichips)and concluded thatcoxaprofundawasanonspecificradiologicalfindingand thatit couldbeconsideredtobeanormalfinding,atleast amongwomen.

In2008,Ganzetal.2_{questionedthenotionthatallpatients}

with morphological abnormalities indicative of FAI would developarthrosisandcontraindicatedtreatmentfor asymp-tomatic patients. A study by Hartofilakidis et al.26 _showed

thatmost(82.3%)ofthepatientswithradiological evidence ofFAI remained asymptomatic and freefrom osteoarthro-sisfor amean of18.5 years, and that the onlysignificant predictor ofosteoarthrosis was the presenceof idiopathic osteoarthrosisinthecontralateralhip.Thissuggeststhat sys-temicpathological factorsmay havegreaterinfluencethan minimalmorphologicalalterationsandwouldcontraindicate surgical treatment for asymptomatic patients with radio-graphicevidenceofFAI.

Arthroscopictreatmentofcam-likeimpacthasshowngood results, especiallyamongpatients placinghighdemandon thejoints.JavedandO’Donnell27_{evaluatedtheresultsfrom}

treatingcam-likeFAIbymeansofarthroscopicfemoral osteo-chondroplasty in patients over the age of 60 years. They reportedahighsatisfactionrate(75%),withoutanycasesof complicationsandwithevaluationtototalhiparthroplastyin 17%ofthecases.

Intheorthopedicliterature,severaltreatmentsfor pincer-like FAI have been described, including periacetabular osteotomy1,2_{andrimtrimmingwithlabralrepair.}28_However,

therearenorandomizedprospectivestudieswith measure-ment of objective data, for example regarding the result from physiotherapeutic treatmentforpatientswith pincer-likeFAIalone.Thecamandpincercomponentsrarelyoccur separately,1,4_{butithasstillnotbeeninvestigatedwhetherit}

isnecessarytodealwithcamandpincerdeformitiesinthe samehip,orjustononesideofthejoint.19

Siebenrock et al.24 _{warned that in hips with coxa}

reconstructionfortreatingFAImight,inreality,betheresult fromconcomitantlydealingwithlabralorchondrallesions.29

ArthroscopictreatmentforthefemoralcomponentofFAI (cam),withfemoralosteochondroplastyandconsequent cor-rection of the alpha angle, followed by repair ofchondral andlabrallesions,hasshownexcellentclinicalresults.20_We

believethatthis technique, whichisnotgreatly aggressive towardthe acetabularroof,could beindicatedforthe vast majorityofpatientswithrealindicationsfororthopedic sur-gicaltreatment.

Conclusion

Ourfindings,supportedbythepresenceofastatistically sig-nificantinverse correlationbetweentheangleofacetabular versionandthe alphaangleinsymptomaticpatients, rein-force the hypothesis that pincer action due to acetabular retroversionisnotthesolecauseofFAI,giventhatin asymp-tomaticindividuals,thereis acetabularretroversionthat is compensatedbythefemur.Insymptomaticpatients,this cor-relationisinverse,i.e.thesmallertheacetabularanteversion is,thelargerthealphaangleofthefemuris.

Thismayaidorthopedistsinmakingtherapeuticdecisions regardingthevariousclinical presentationsofFAIand also provideawarningtothemregardingtheexistenceof over-diagnosis.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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1. CrawfordJR,VillarRN.Currentconceptsinthemanagement

offemoroacetabularimpingement.JBoneJointSurgBr.

2005;87(11):1459–62.

2. GanzR,LeunigM,Leunig-GanzK,HarrisWH.Theetiologyof

osteoarthritisofthehip:anintegratedmechanicalconcept.

ClinOrthopRelatRes.2008;466(2):264–72.

3. GanzR,ParviziJ,BeckM,LeunigM,NötzliH,SiebenrockKA.

Femoroacetabularimpingement:acauseforosteoarthritisof

thehip.ClinOrthopRelatRes.2003;417:112–20.

4. BeckM,KalhorM,LeunigM,GanzR.Hipmorphology

influencesthepatternofdamagetotheacetabularcartilage:

femoroacetabularimpingementasacauseofearly

osteoarthritisofthehip.JBoneJointSurgBr.

2005;87(7):1012–8.

5. HavivB,BurgA,VelkesS,SalaiM,DudkiewiczI.Trendsin

femoroacetabularimpingementresearchover11years.

Orthopedics.2011;34(5):353.

6. BeaupreGS,OrrTE,CarterDR.Anapproachfor

time-dependentbonemodelingandremodeling:theoretical

development.JOrthopRes.1990;8(5):651–61.

7. McKibbinB.Anatomicalfactorsinthestabilityofthehipjoint

inthenewborn.JBoneJointSurgBr.1970;52(1):148–59.

8. CarterDR,OrrTE,FyhrieDP,SchurmanDJ.Influencesof

mechanicalstressonprenatalandpostnatalskeletal

development.ClinOrthopRelatRes.1987;(219):237–50.

9. CarterDR.Mechanicalloadinghistoryandskeletalbiology.J

Biochem.1987;20(11–12):1095–109.

10.DoraC,ZurbachJ,HerscheO,GanzR.Pathomorphologic

characteristicsofposttraumaticacetabulardysplasia.J

OrthopTrauma.2000;14(7):483–9.

11.ReynoldsD,LucasJ,KlaueK.Retroversionoftheacetabulum:

acauseofhippain.JBoneJointSurgBr.1999;81(2):281–8.

12.LeunigM,CasillasMM,HamletM,HerscheO,NötzliH,Slongo

T,etal.Slippedcapitalfemoralepiphysis:earlymechanical

damagetotheacetabularcartilagebyaprominentfemoral

metaphysis.ActaOrthopScand.2000;71(4):370–5.

13.ItoK,MinkaMA,LeunigM,WerlenS,GanzR.

Femoroacetabularimpingementandthecam-effect:a

MRI-basedquantitativeanatomicalstudyofthefemoral

head-neckoffset.JBoneJointSurgBr.2001;83(2):171–6.

14.CobbJ,LogishettyK,DavdaK,IranpourF.Camsandpincer

impingementaredistinct,notmixed:theacetabular

pathomorphologyoffemoroacetabularimpingement.Clin

OrthopRelatRes.2010;468(8):2143–51.

15.BullerLT,RosneckJ,MonacoFM,ButlerR,SmithT,Barsoum

WK.Relationshipbetweenproximalfemoralandacetabular

alignmentinnormalhipjointsusing3-dimensional

computedtomography.AmJSportsMed.2012;40(2):367–75.

16.KamathS,NarayanaswamyS.Computedtomography

assessmentofhipjointsinasymptomaticindividualsin

relationtofemoroacetabularimpingement.AmJSportsMed.

2010;38(8):NP1.

17.ChenL,BoonthathipM,CardosoF,CloptonP,ResnickD.

Acetabulumprotrusioandcenteredgeangle:new

MR-imagingmeasurementcriteria–acorrelativestudywith

measurementderivedfromconventionalradiography.

SkeletalRadiol.2009;38(2):123–9.

18.MoynihanR,DoustJ,HenryD.Preventingoverdiagnosis:how

tostopharmingthehealthy.BrMedJ.2012;344:19–23.

19.PollardTC.Aperspectiveonfemoroacetabularimpingement.

SkeletalRadiol.2011;40(7):815–8.

20.ByrdJW,JonesKS.Arthroscopicfemoroplastyinthe

managementofcam-typefemoroacetabularimpingement.

ClinOrthopRelatRes.2008;467(3):739–46.

21.HogervorstT,BoumaH,deBoerSF,deVosJ.Humanhip

impingementmorphology:anevolutionaryexplanation.J

BoneJointSurgBr.2011;93(6):769–76.

22.TönnisD,HeineckeA.Acetabularandfemoralanteversion.

Relationshipwithosteoarthritisofthehip.JBoneJointSurg

Am.1999;81(12):1747–70.

23.KonishiN.Thethree-dimensionalacetabularcoverageandits

positionalchangeduetochangeofpelvictilt.HipJoint.

1993;19:423–7.

24.SiebenrockKA,SchoenigerR,GanzR.Anterior

femoro-acetabularimpingementduetoacetabular

retroversion:treatmentwithperiacetabularosteotomy.JBone

JointSurgAm.2003;85(2):278–86.

25.NeppleJJ,LehmannCL,RossJR,SchoeneckerPL,ClohisyJC.

Coxaprofundaisnotausefulradiographicparameterfor

diagnosingpincer-typefemoroacetabularimpingement.J

BoneJointSurgAm.2013;95(5):417–23.

26.HartofilakidisG,BardakosNV,BabisGC,GeorgiadesG.An

examinationoftheassociationbetweendifferent

morphotypesoffemoroacetabularimpingementin

asymptomaticsubjectsandthedevelopmentofosteoarthritis

ofthehip.JBoneJointSurgBr.2011;93(5):580–6.

27.JavedA,O’DonnellJM.Arthroscopicfemoral

osteochondroplastyforcamfemoroacetabularimpingement

inpatientsover60yearsofage.JBoneJointSurgBr.

2011;93:326–31.

28.PhilipponMJ,SchenkerML.Anewmethodforacetabularrim

trimmingandlabralrepair.ClinSportsMed.2006;25(2):293–7.

29.PalmerWE.Femoroacetabularimpingement:cautionis

warrantedinmakingimaging-basedassumptionsand