w w w . r b o . o r g . b r
Original
Article
Study
of
the
metatarsal
formula
in
patient
with
primary
metatarsalgia
夽
Eduardo
Kenzo
Arie,
Norma
Sueli
Albino
Moreira,
Gilmar
Soares
Freire,
Bruno
Schifer
dos
Santos,
Liu
Chiao
Yi
∗SantaCasadeSantos,Santos,SP,Brazil
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received24May2014 Accepted17July2014 Availableonline11July2015
Keywords:
Metatarsalgia Metatarsalbones Reproducibilityoftests
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b
s
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c
t
Objectives:Theaimsofthisstudywere(i)toascertaintheprevalenceofdifferenttypesof metatarsalformulaamongpatientswithprimarymetatarsalgia;(ii)tocomparethevariable of“shorteningofthefirstmetatarsalinrelationtothesecond”(I/II)betweenthe metatarsal-giaandcontrolgroups;and(iii)toanalyzetheintraandinterobserverconcordancebymeans ofMorton’stransverselinemethodandHardyandClapham’sarcmethod.
Methods:A cross-sectionalobservationalstudywasconductedon56patientsbymeans ofradiographsontheir112ft,ofwhich56wereinthemetatarsalgiagroupand56inthe controlgroup.TheevaluationsweredonebetweenDecember2012andJune2013.The mea-surementsweremadebythreethird-yearorthopedicsresidentswithpriortraininginthe methodsused,andatemplatewasused.
Results:Therewasnoconcordancebetweenthetwomethods,asshownbyBland–Altman plots, although theintraclass correlation coefficients showed thatthe intra and inter-observerreproducibilitywashighusingthe transverselinemethod(0.78 and0.85)and moderateusingthearcmethod(0.73and0.60).Comparisonbetweenthegroupsshowed thattherewasastatisticaldifference(p≤0.05)suchthattherewasgreatershorteningofthe firstmetatarsal(3.39mm)inthecontrolgroupthaninthemetatarsalgiagroup(2.14mm). Inthepatientswithprimarymetatarsalgia,theindexminusmetatarsalformulawasmore prevalentaccordingtothetransverselinemethod(62.5%)andthezeroplustypeaccording tothearcmethod(71.4%).
Conclusion:Inthepresentstudy,itwasobservedthatthemetatarsalformulaprevalences dependedonthemeasurementmethod.Inbothgroups,shorteningofthefirstmetatarsal predominated.Therewasnointraorinterobserverconcordanceineitherofthetwo pro-posedmethods.
©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.
夽
WorkdevelopedintheOrthopedicsService,SantaCasadaMisericórdiadeSantos,Santos,SP,Brazil.
∗ Correspondingauthor.
E-mails:[email protected],[email protected](L.C.Yi).
http://dx.doi.org/10.1016/j.rboe.2015.06.018
Estudo
da
fórmula
metatarsal
em
pacientes
com
metatarsalgia
primária
Palavras-chave:
Metatarsalgia Ossosdometatarso Reprodutibilidadedostestes
r
e
s
u
m
o
Objetivos: Verificaraprevalênciadostiposdefórmulametatarsal(FM)empacientescom metatarsalgiaprimária(MP);compararavariável“encurtamentodoprimeirometatarso emrelac¸ãoaosegundo”(I/II)entreosgruposmetatarsalgia(GM)econtrole(GC);analisar
aconcordânciaintraeinterobservadorespelosmétodosdaslinhastransversais(MLT)de Mortonedosarcos(MA)deHardyeClapham.
Métodos:Estudoobservacionaltransversalem56pacientespormeioderadiografiasdos112 pés,56doGMe56doGCavaliadosentredezembrode2012ejunhode2013.Asmensurac¸ões foramfeitasportrêsresidentesdoterceiroanoemortopedia,comtreinamentopréviodos métodoseusodetemplate.
Resultados:Nãohouveconcordânciaemnenhumdosdoismétodosverificadospelosgráficos deBland–Altman,apesardeocoeficientedecorrelac¸ãointraclassesapresentarumaalta reprodutibilidadeintraeinterobservadorespeloMLT(0,78e0,85)emoderadapeloMA(0,73 e0,60).Nacomparac¸ãoentreosgrupos,observou-sediferenc¸aestatística(p≤0,05)comum
encurtamentodoprimeirometatarso(3,39mm)maiornoGCemrelac¸ãoaoGM(2,14mm). NospacientescomMP,aFMtipoindexminusfoimaisprevalentepeloMLT(62,5%)eotipo
zeropluspeloMA(71,4%).
Conclusão: FoiobservadoqueaprevalênciadaFMdependedométododemensurac¸ão.Em ambososgruposhouvepredomíniodoencurtamentodoprimeirometatarso.Nãohouve concordânciaintraeinterobservadoresemnenhumdosmétodospropostos.
©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Todososdireitosreservados.
Introduction
Metatarsalgia, characterized by pain in the plantar region of the forefoot under the metatarsal heads, is one of the most frequent complaints in clinical practice among con-ditions affecting the feet.1,2 Nearly 80% of the normal
population present some form of pain in the metatarsal region over their lifetime.3 The main etiological factors
are biomechanical alterations, which makeup 92% of the total.4 These can be classified as primary, secondary and
iatrogenic. Primary metatarsalgiaalterations are related to the anatomy of the metatarsals and their relationships, which can lead to mechanical overload on the affected metatarsus and may evolve with pain and plantar cal-losities. In some cases, these consequences may become incapacitating.1,5
Thepresenceofashortfirstmetatarsus,knownas Mor-ton’stoe,isconsideredbymanyauthorstobeacontributing factor for the development of primary metatarsalgia.1,3,6
The relationship among the lengths of the metatarsals is defined as the metatarsal formula.3,7 Although this tool
is used both for diagnostic investigation and for guid-ance toward treatment, the choice of the measurement method and their results are matters of controversy in theliterature. Themethodsmostcitedare Morton’s trans-verse line (MTL) and Hardy and Clapham’s arc method (AM).8–10
Onecrucialaspectininterpretingdiagnostictestsisthat theobservers’measurementsshouldbecoherent,sothatthe resultswillbereproducible.Thisistheconceptofprecision,
whichisnecessaryforthevalidationofthemethodandits usefulnessinclinicalpractice.11
Theobjectives ofthepresent studywere toobserve the prevalenceofthetypesofmetatarsalformulaamongpatients withprimarymetatarsalgia;comparethevariableof “shorten-ingofthefirstmetatarsusinrelationtothesecond”between themetatarsalgiagroup(MG)andthecontrolgroup(CG);and analyzetheintraandinter-observeragreementthroughthe MTLandAMmethods.
Methods
Thiswasacross-sectionalobservationalstudyon56patients (112ft), over the ageof 18years and all female, who were dividedinto28patients(56ft)intheMGand28(56ft)inthe CG.
TheMGconsistedofpatientswithpainfulsymptomsinthe regionofthemetatarsalheads,whohadbeendiagnosedas presentingprimarymetatarsalgiaduetomechanicaloverload. TheCGwascomposedofpatientswithplantarfasciitis,who presentedpaininthehindfootregion.
Patientswereexcludediftheypresenteddeformitiesthat compromised theforefoot, midfootorhindfoot; apersonal historyofprevioussurgeryortraumatothefeet;orpersonal historiesofdiabetesmellitus,rheumatologicaldiseases, vas-culardiseasesorneuropathies.
Procedures
Threemedicalresidentsinorthopedicswhowereintheirthird yearofspecializationandunderthesupervisionofthe princi-palinvestigatorevaluatedallthepatientswithcomplaintsof painintheirfeetwhowentthroughtheoutpatientserviceof ourdepartmentbetweenDecember2012andJune2013.
Thevolunteersunderwentsimpleradiographyonbothfeet inthe uprightstanding position, intruedorsoplantarview withacranialangleof15◦,atrealsize.12
Reproducibility
Toassessinterobserverreliability,alltheradiographicimages were measuredusing theMTLand AMseparately bythree observers.
Toassessintraobserverreliability,oneoftheobserverswas randomlychosentoperformthemeasurementsagain,eight weeksafterthefirstevaluation.
All three observers received prior training on the mea-surementmethods.Tohelptheevaluationandmakeitmore reliable and reproducible, an illustrative and explanatory modelforbothmethodswasattachedbesidetheregistration form(Fig.1).
Morton’s transverse line method of measurement was appliedschematically:1–setupalineoverthediaphysealaxis ofthesecondmetatarsal;2–drawatransverseline perpen-diculartotheapexoftheheadofthefirstmetatarsal;3–draw atransverselineperpendiculartotheapexoftheheadofthe secondmetatarsal;4–measurethedistancebetweenthese twotransverselinesinmillimeters.HardyandClapham’sarc methodwasalsoappliedschematically:1–setupalineover thediaphyseal axisofthesecond metatarsal;2–markthe centerofthearcsattheintersectionofthislinewithanother linethattouchesthemostmedialpointoftalonavicularand the most lateral point of calcaneocuboid; 3 – draw an arc thattouchestheapexofthe headofthefirstmetatarsal;4 –drawanarcthattouchestheapexoftheheadofthesecond metatarsal;5–measurethedistancebetweenthesetwoarcs inmillimeters.6–9
Statisticalanalysis
Basedona pilotstudy performedpreviouslyand consider-ingthevariableof“relativedifferenceinthelengthbetween thefirstandsecondmetatarsals”(I/II),thesamplesizewas
definedas28patients pergroup,withapower of80%and significancelevelof0.05.
Thedescriptiveanalysiswaspresentedasthemeanand standarddeviationofthevariablesanalyzed.Toevaluateintra andinterobserverreliability,theinterclasscorrelation coeffi-cient(ICC)wasappliedandclassifiedas:minimal(≤0.25),low
(between0.26and 0.49), moderate (between0.50and 0.69), high(between0.70and0.89)orveryhigh(≥0.90).13
Single-factoranalysisofvariancewasusedtocomparethe CGandtheMGregardingthevariableI/II.
To observe the prevalences of the types of metatarsal formula,Viladot’s classification3,14 asmodified byMancuso
etal.15 wasused,consideringtwotypes:valueslower than
Table1–Relativedifferenceinlengthbetweenthefirst andsecondmetatarsals.
Observer Method Mean(SD)
A Transverselines −2.77mm(2.90)
Arc 0.04mm(2.90)
B Transverselines −2.72mm(2.87) Arc 0.42mm(2.88)
C Transverselines −2.47mm(3.04)
Arc −0.88mm (2.94)
mm,millimeters;SD,standarddeviation.
Table2–Comparisonoftheinterobserveragreement analysisbetweenthetransverselinemethodandthearc method.
Method ICC CI p
Transverselines 0.85 [0.81;0.89] 0.104 Arc 0.60 [0.50;0.69] 0.001a
ICC,intraclasscorrelationcoefficient;CI,confidenceinterval;p, sig-nificanceleveloftheanalysisofvarianceinblocks.
a p≤0.05.
−0.5mmwereclassifiedasindexminusandpositivevalues
aszeroplus.
Results
Thedescriptivedataandthestatisticalanalysisresultswere asfollows:
Table1showsthemeanandstandarddeviation(SD)ofthe measurementsonthevariableI/IIusingboththeMTLandthe AMbyallthreeobservers.
Table2demonstratesthattheMTLpresentedhigherICC andlowerCI,incomparisonwiththeAM,whileinanalysis ofvariancedividedinto blocks,theAMpresenteda signifi-cantdifference(p≤0.05),whichdemonstrateddisagreement
betweentheobservers.
TheBonferroni methodshown inTable3 demonstrated thatthemeansofobserversAandBdiffered(p≤0.05)from
themeanofobserverC,usingtheAM.
Figs.2and3presenttheresultsfromtheBland–Altman plots, whichindicatedthattherewasnoagreementamong theobservers,usingeithertheMTLortheAM.
Table3–Statisticalanalysisonthecomparisons betweenobservers,twobytwo.
Observerscompared p
C–A 0.001a
C–B 0.002a
B–A 0.296
Fig.1–PrevioustrainingandtemplateformeasurementsusingMorton’stransverselinemethod(A)andHardyand
Clapham’sarcmethod(B).
3
2
1
0
–2 –4
–6
–8 0
Means of the evaluations
Standard deviations of the evaluations
2
Fig.2–Interobserverevaluationusingthetransverselinemethod.
Table4presentsthedescriptivemeasurementsonthe vari-ableI/II,accordingtotheMTLandAM,madebyobserverAat twodifferenttimes.
Table4–Relativedifferenceinlengthbetweenthefirst andsecondmetatarsals.
Evaluations Method Mean(SD)
1st time
Transverselines −2.77mm(2.90)
Arc 0.04mm(2.90)
2nd time
Transverselines −2.57mm(2.80) Arc 0.06mm(2.77)
SD,standarddeviation;mm,millimeters.
Table5demonstratesthattheMTLobtainedahigherICC andlowerCIthantheAMdid.TheStudentttestindicatedthat therewasagreementbetweentheevaluationsusingthetwo methods.
Table5–Comparisonanalysisonintraobserver agreement.
Method ICC CI p
Transverselines 0.78 [0.70;0.84] 0.275 Arc 0.73 [0.64;0.81] 0.909
ICC,intraclasscorrelationcoefficient;CI,confidenceinterval;p, sig-nificanceleveloftheStudentttestanalysis.
6
Standard deviations of the evaluations
–2
–4 0 2 4
Means of the evaluations
6 4
2
0
Fig.3–Interobserverevaluationusingthearcmethod.
Figs.4and5indicatethattherewasnoagreementbetween theevaluationsusingeithertheMTLortheAM.
Comparisonsbetweenthegroupsweremadeusingthefirst measurementsfromobserverA,bymeansoftheMTL.
Themeanvalueofthedescriptivemeasurementsonthe variableI/IIintheMGwas−2.14mm(SD=3.05)andintheCG
itwas−3.39mm(SD=2.63)(Fig.6).
TheresultfrominferentialanalysistocomparetheCGand theMGregardingthevariableI/IIwasusedinasingle-factor mixedmodelofvariance.Thisindicatedthattherewasa dif-ference(p≤0.05)betweenthemeansoftheCGandMG.
Table6showsadescriptivecomparisonbetweentheMTL andAMregardingtheprevalencesoftypesofmetatarsal for-mulaintheCGandMG.TheMGshowedhigherprevalenceof
–2 –4
–6
–8 0 2
Mean (Evaluation 1, Evaluation 2) –6
–4 –2 0 2 4
Mean –2 SD Mean Mean +2 SD
Evaluation 1 – Evaluation 2
Fig.4–Intraobserverevaluationusingthetransverselinemethod.
–6
Mean (Evaluation 1, Evaluation 2)
Mean –2 SD Mean Mean +2 SD
–2
–4 0 2 4
–10 –5 0
Evaluation 1 – Evaluation 2
6 5
Control Metatarsalgia –8
–6 –4 0 2 4
Relative difference
–2
Fig.6–Distributionofthevariableof“relativedifferenceof thelengthbetweenthefirstandsecondmetatarsal”, accordingtoeachgroup.
Table6–Prevalenceofthetypesofmetatarsalformula inthegeneralsampleandinthegroups.
Method Metatarsal formula
Metatarsalgia group
Control group
Transverse lines
Indexminus 62.5% 85.7% Zeroplus 37.5% 14.3%
Arc Indexminus 28.6% 53.6% Zeroplus 71.4% 46.4%
feetwiththeindexminustypeofmetatarsalformula(62.50%) accordingtotheMTL,whilethezeroplustypeofmetatarsal formulawasmoreprevalentaccordingtotheAM(71.43%).The
CGpresentedhigherprevalenceoftheindexminustypeof
metatarsalformula(85.71%)accordingtotheMTL,andalso accordingtotheAM(53.57%).
Discussion
Thelengthrelationshipsbetweenthemetatarsals,more
com-monly known as the metatarsal formula, is a matter of
controversyintheliteraturewithregardtoboththechoiceof methodformeasurementandtheassociationofthiscondition
withthedevelopmentofseveraldisordersthatcompromise
theforefoot,suchasprimarymetatarsalgia.7,10
Theresultsfromthepresentstudyshowedthat measure-mentofthemetatarsalformulathroughthetransverseline methodisrelatedtohigherprevalenceoffeetwithasecond metatarsallongerthanthefirst(indexminus).Thesamewas observedbyMorton,6whocorrelatedthistypeoffootasa
con-tributingfactorforthedevelopmentofprimarymetatarsalgia. This concept has been established by several authors.1,3,5
However,whenthesame methodwasusedforthe control group,even greater prevalenceofthe index minus typeof footwasobserved,asalsoseenbyBarrocoetal.12among332
normalfeet intheirstudy. Incomparing themeans ofthe numericalvariableof“relativedifferencebetweenthelength ofthefirstandsecondmetatarsals”,asignificantdifference wasobserved(p≤0.05).However,thisfindingwastheinverse
oftheconceptualhypothesis,withgreatershorteningofthe firstmetatarsalinthecontrolgroupthaninthemetatarsalgia group.Thisresult,combinedwithdataintheliterature,12
con-tradictsthe“Morton’stoe”theoryanddemonstratesthatfeet withshorteningofthefirstmetatarsalorwithanindexminus typeofmetatarsalformulameasuredthroughthetransverse linemethodareinfactthemostprevalenttypeoffeetamong thegeneralpopulation.
The present study foundthat the prevalences of differ-enttypesofmetatarsalformulaamongpatientswithprimary metatarsalgiadependonthemeasurementmethod. Unlike in the transverse line method, the mostprevalent typeof metatarsalformulaobservedthroughthearcmethodisthe zero plusformula,asobservedbyHardyandClapham and other authors.9,16,17 Thisphenomenon possibly occurs due
to technicaldifferences between the measurements: when patientswithahighintermetatarsalangle(greaterthan9◦)
areevaluated,thereisarelativedecreaseinthelengthofthe firstmetatarsalasmeasuredthroughMorton’stransverseline method.However,whenpatientswhosefeetdonotpresent deformitiesareevaluated,aswasthecaseinthepresentstudy, in which the patients presenteda normal intermetatarsal angle(between0◦ and8◦),thereisarelativeincreaseinthe
lengthofthefirstmetatarsalwhenmeasuredthroughHardy andClapham’sarcmethod.15
Several ways to measure metatarsal length have been described in the literature, such as anatomopathological assessmentsonthefeetofcadavers,18clinicalparameters,19
lateral-view radiography,20 tomography21 and
computer-basedmeasurement,22evenforsurgicalplanning.23However,
the manualradiographicmethod ofmeasuringthe relative lengthofMorton’stransverselinesandHardyandClapham’s arcs are the methods most cited and used as diagnostic instruments.7,9,10
Inthepresentstudy,theevaluationsmadebythe third-yearorthopedicresidents,whohadreceivedprevioustraining andusedatemplate,didnotpresentintraandinterobserver agreementusingeithermethod.Thetransverselinemethod presenteda greater correlationcoefficient than that ofthe arcmethod,possiblyduetothesimplicityofthetechnique, sincethearcmethodhasoneadditionalstep.Thisstep com-prisesanadditionallinethatisdrawnontheChopartjoint, andthiswasconsideredbytheobserverstobethe disagree-mentfactor.However,inanotherstudy,noneofthemethods presented agreement according to the Bland and Altman method.24Whenthemeanvaluesfromtheintraand
interob-serverevaluationswerepairedandplottedwiththeirstandard deviations and agreementlimits, instead offinding results nearthezerolineofequality,theresultswereverydiscrepant. Thisdemonstratesthelackofagreementandreproducibility ofthemethodsand,thus,putstheiruseinclinicalpractice intoquestion.
The reproducibility of a test indicates the precision of the method and determines its validity and use in clin-ical practice.11 The Bland and Altman statistical method
of the correlation coefficients in isolation is inappropriate becausethis maybringincompleteinformationand inade-quateinterpretations.25,26
Adiagnostictechniqueshouldpresentprecisionand repro-ducibility,with consistencyover differentobservationsand littlevariability.However,thetechniquesproposedtoassess themetatarsalformulacannotbecomparedorstandardized, preciselybecausethecurrentsubjectivecriteriapresentgreat intraandinterobservervariability.
Different methods for measuring the length of the metatarsalshavethepotentialtogiverisetodifferentresults, withpotentialconsequencesforsurgicalplanning.Inthelight ofthecurrentresults,surgicaltreatmentbasedonlyonthis radiographicparameteris,tosaytheleast,questionable. Clin-icalexaminationmustbethepriorityinrecommendingany metatarsalosteotomyandshouldbecomplementedbyother parameters,suchasassessmentoftheinstabilityofthefirst rayandanatomicalalterationsofthemetatarsalsinthe coro-nalplane.
Conclusion
Itwasobservedthattheprevalenceofthemetatarsalformula dependsonthemeasurementmethod. Incasesofprimary metatarsalgia, the indexminus typeis related toMorton’s method, while the zero plus type is related to Hardy and Clapham’smethod.
IncomparingtheCGandtheMGusingMorton’stransverse linemethod,therewaspredominanceofshorteningofthefirst metatarsalinbothgroups.
The methods for measuring the metatarsal formula appliedinthepresentstudydidnotshowanyintraor inter-observeragreement.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
Acknowledgement
WearegratefultoDr.MauricioSgarbiforenablingand sup-portingthisstudy.
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