Is it safe the empirical distal femoral resection angle of 5 to 6 of valgus in the Brazilian geriatric population?

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

Original

Article

Is

it

safe

the

empirical

distal

femoral

resection

angle

of

5

◦

_to

6

◦

of

valgus

in

the

Brazilian

geriatric

population?

夽

Fernando

Cury

Rezende

a,∗

,

Márcio

de

Castro

Ferreira

b

,

Pedro

Debieux

c

,

Carlos

Eduardo

da

Silveira

Franciozi

d

_,

_Marcus

_Vinicius

_Malheiros

_Luzo

e

_,

Mário

Carneiro

f

a_Resident_Orthopedist_in_the_Knee_Group,_Department_of_Orthopedics_and_{Traumatology,}_Universidade_Federal_de_São_Paulo_(UNIFESP),

SãoPaulo,SP,Brazil

b_Orthopedist_at_the_Orthopedics_and_Sports_{Rehabilitation}_Center,_Hospital_do_Corac¸ão_de_São_Paulo_(HCor),_São_Paulo,_SP,_Brazil c_Attending_Physician_in_the_Knee_Group,_Department_of_Orthopedics_and_{Traumatology,}_UNIFESP,_São_Paulo,_SP,_Brazil

d_PhD_from_the_Department_of_Orthopedics_and_{Traumatology,}_UNIFESP;_and_Attending_Physician_in_the_Knee_Group,_Department_of

OrthopedicsandTraumatology,UNIFESP,SãoPaulo,SP,Brazil

e_PhD;_Affiliated_Professor_in_the_Department_of_Orthopedics_and_{Traumatology,}_UNIFESP;_and_Attending_Physician_in_the_Knee_Group,

DepartmentofOrthopedicsandTraumatology,UNIFESP,SãoPaulo,SP,Brazil

f_PhD;_Affiliated_Professor_in_the_Department_of_Orthopedics_and_{Traumatology,}_UNIFESP;_and_Head_of_the_Knee_Group,_Department_of

OrthopedicsandTraumatology,UNIFESP,SãoPaulo,SP,Brazil

a

r

t

i

c

l

e

i

n

f

o

Articlehistory: Received15June2012 Accepted3August2012

Keywords: Kneejoint

Arthroplastykneereplacement Ostearthritis

Panoramicradiography

a

b

s

t

r

a

c

t

Objective:Thepurposeofthisstudyistodetermineifthereisasafedistalfemoralresection angletorestorethenormalaxialalignmentofthelimbintotalkneearthroplasty(TKA)in theBraziliangeriatricpopulationwithkneearthrosis.

Method:Thisstudyanalyzed99pre-operativehip-knee-ankleradiographsofosteoarthritic kneesof66patients(54women,12men)withkneeosteoarthritis.Thedistalfemoralcut anglewasdeterminedbasedonthefemoralmechanical-anatomicalangle(FMA).Mean, medianandstandarddeviationmeasurementsofthedistalfemoralcutanglewere calcu-lated,differentiatedbygenderandside.Themeanresultofthedistalfemoralresection anglewascomparedto5.7◦_,_the_mean_average_angle_of_previous_and_similar_study_based_on

Europeanpopulationofpatientswithkneearthrosis.

Results:Themeanaverageofthedistalfemoralresectionangleofthestudywas6.05(range 3–9◦_)._The_distribution_of_this_angle_between_genders_showed_a_slight_superior_average_of_the

malepopulation(6.17◦₎_compared_to_the_female_(6.02◦_),_but_with_no_{statistically}_significant

difference(p=0.726).Therewasnostatisticallysignificantdifference(p=0.052)betweenthe meanaverageofthisstudy(6.05◦₎_compared_to_the_mean_average_of_the_literature_(5.7◦_).

However,considering3◦_as_the_limit_of_acceptable_error_in_the_coronal_plane,_this_empirical

femoralresectionanglewouldnotbeappropriatedfor19.7%ofthepopulation.

夽

StudyconductedattheDepartmentofOrthopedicsandTraumatology,UniversidadeFederaldeSãoPaulo,SãoPaulo,SP,Brazil.

∗ _{Corresponding}_author_at_:_Avenida_Onze_de_Junho,_582,_Vila_Clementino,_São_Paulo,_SP,_Brazil._Tel.:₊₅₅₁₁₂₉₂₄_6217;_fax:₊₅₅₁₁₂₉₂₄_6217.

E-mail:rezendefernando@hotmail.com(F.C.Rezende).

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Conclusion: Thedistalfemoralresectionangleof5–6◦_is_not_completely_safe_for_the_Brazilian

geriatricpopulation.

É

seguro

o

corte

femoral

distal

em

artroplastia

total

do

joelho

com

5

◦

_a

₆

◦

de

valgo

empiricamente

na

populac¸ão

geriátrica

brasileira?

Palavras-chave: Articulac¸ãodojoelho Artroplastiadojoelho Osteoartrite

Radiografiapanorâmica

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e

s

u

m

o

Objetivo: Determinarseexisteumânguloseguroparaocortefemoraldistal,paraqueo membroresultealinhadoapósumaartroplastiatotaldejoelho(ATJ),napopulac¸ãogeriátrica brasileiracomgonartrose.

Método: Foramfeitasradiografiaspanorâmicasde99membrosinferioresem66pacientes consecutivos(54mulherese12homens)portadoresdegonartrosedojoelho.Oângulodo cortefemoraldistalfoideterminadopeloencontroentreoeixomecânicofemoral(EMF)e oeixoanatômicofemoral(EAF).Foramcalculadososvaloresdamédia,odesviopadrãoea medianadoângulodocortefemoraldistaldessespacientesdiferenciadosporsexoelado.O valormédiodoângulodecortedofêmurdistalidealaquiobtidofoicomparadocomovalor médiode5,7obtidoemestudopréviosemelhanteaessefeitocompopulac¸õeseuropeias depacientesosteoartríticossubmetidosaATJ.

Resultados: AmédiadoânguloformadopelosEAF×EMF,consideradooângulodocorte

femoraldistalemumaATJ,dogrupoestudadofoide6,05(variaçãode3o_a₉o_)._A_{distribuição} desse ângulo entre os sexos evidenciou uma média discretamente superior entre os homens(6,17o₎_em_{comparação}_com_as_mulheres_(6,02o_),_porém_sem_{significância} estatís-tica(p=0,726).Nãohouvediferençaestatística(p=0,052)entreovalormédioobtidona amostraatual(6,05-DP1,27)comovalormédioobtidonaliteratura(5,7◦_)._Entretanto,_se

considerarmosaceitávelumerrode3◦_no_plano_coronal,_19,7%_da_populac¸ão_operada_se

encontrariamforadessafaixaaceitávelseoptarmospelocortefemoralempíricodeacordo comoinstrumental.

Conclusão: OcortefemoraldistalnaATJem5◦_ou₆◦_de_valgo_não_é_{completamente}_seguro

paraapopulac¸ãogeriátricabrasileira.

Introduction

The geopolitical increase observed among developing counties,andespeciallyinBraziloverthelastdecade,hasled toatypicaland unavoidable inversionofthe agepyramid. This has established not only a large but also a growing numberofelderlypeople,whichinBrazilhasalreadyreached 15millionpeople.1_{Unfortunately,}_there_is_no_Brazilian_data

onthenumberofarthroplastyproceduresperyear,butthe increasing number of indications that are associated with increasinglongevityleadstothesuppositionthatthereisa growingneedfortheseprocedures.

There isa consensus inthe literature that the durabil-ityofaknee prosthesisisdependent ontheresultant axis of the operated limb,2 _given _that _for _the _procedure _to _be

carried out, the elemental principle used is that the load shouldbeequallydistributedbetweenthemedialandlateral femoral–tibialcompartments.3–5_Thus,_a_lower_limb_is

consid-eredtobealignedwhenits mechanicalaxis(thelinefrom thecenterofthefemoralheadtothecenteroftheankle,4,6–9

knownastheMaquetline10₎_crosses_the_center_of_the_knee.

Theerrorlimitisacceptedtobeavarusorvalgusangular vari-ationof3◦_.11,12_Achievement_of_this_result_depends_on_making

thebonecutsperpendicularlytothemechanicalaxisdesired, inassociationwithmedial–lateralligamentequalization.

Inthiscontext,bothnavigation-assistedsurgeryandthe classic methodsusing intra orextramedullary guides have been shown to be effective for achieving an aligned limb. Theformerhasbeenshowntobeeffectiveforgoodresults,13

butislimitedbythehighcostandlonglearningcurve.The classicalmethod,whichusesanintramedullaryguideforthe femurandanextramedullaryguideforthetibia,whichhas gained massusagewithinoursetting,presentsresultsthat arenotablysatisfactoryandeasilyimplementedforplanning thebonecutspreoperatively.12_Thus,_panoramic_radiographs

ofthelowerlimbsshouldbeobtainedbeforetheoperation14,15

andtheangleofthedistalfemoralcutshouldbedetermined fromthemeetingpointsbetweenthemechanicalaxesandthe femoralanatomy.3,4_However,_these_measurements_are

some-timesneglected,16_with_regard_to_either_preoperative_analysis

orpostoperativeassessment,becauseofthecoastorthe dif-ficulty in finding radiological centers that do this type of imaging.

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Table1–Inclusionandexclusioncriteriaofthestudy.

Inclusioncriteria Exclusioncriteria Radiographicdiagnosisof

primaryosteoarthrosis

Secondaryosteoarthritis

Sixmonthsofconservative treatment

Presenceofipsilateralknee prosthesis

>18yearsofage Presenceofipsilateralhip prosthesis

Incapacitytostandupright Deformityfixedinflexion>10◦

dataavailableinthe medicalliteratureare based onmean

angles for American and European populations that have

previouslybeenstudied.6,17,18_These_populations_may_not

rep-resenttheindividual anatomyofeach patient, oreventhe anatomyoftheaverageBrazilianpopulation,becauseofthe highdegreeofmiscegenationamongthesepeople.19

Thepresent studyhad the aimofdeterminingwhether thereisasafe anglefordistalfemoralresectiontorestore the normal alignment of the limb aftertotal knee arthro-plasty(TKA), amongthe Braziliangeriatricpopulation with kneearthrosis.

Material

and

method

FromJune2008toJanuary2009,panoramicradiographswere produced on99 lower limbsin 66 consecutive patients(54 womenand12 men)agedover 60years,who allhad knee arthrosisforwhichconservativetreatment(drugsand phys-iotherapy)hadfailed.Thus,theyallhadasurgicalindication forreplacementarthroplasty, inaccordance withthe inclu-sionandexclusioncriteriashowninTable1.Thereasonfor excludingpatientswhowereincapableofstandinguprightor whohadrigiddeformitiesinflexionwasthatitwas impossi-bletoproducepanoramicradiographsinaccordancewiththe standardestablishedforthisstudy.

Beforetheoperation,allthepatientsunderwentpanoramic radiography on their lower limbs, performed in the same radiologicalcenter.Theradiographswereproducedwiththe patientsstandingupright,withthefeettogetherinthecase ofpatientswithvarusdeformityorthekneestogetherinthe caseofvalgus.Thekneeswereatmaximumextensionandthe lowerlimbswereattheneutralrotationposition,whichwas ensuredbypositioningthepatellaforwardsinthedirectionof thebulboftheX-raymachine.20

Theangleofthedistalfemoralcutwasdeterminedfrom the meeting point between the femoral mechanical axis (FMA)3,4 _and_the_femoral_anatomical_axis_(FAA)₍_Fig.₁_)._The

FAA wasdefinedbythe linethat crossesthe centerofthe femoralisthmus(giventhataccordingtotheliterature,thisis thepointthatallowsthesmallestrangeofangularerror21,22₎

andthecenteroftheintercondylarnotch.Inturn,theFMA consistsof the line that crossesthe center of the femoral head(proximally)andthecenteroftheintercondylarnotch (distally).

Theaxesweretracedoutusingarulerandtheangleswere measuredusingaprotractor(Desetec®_for_both_{instruments),} graduatedin0.1mmand0.5◦_divisions._All_the_measurements

Fig.1–Magnificationofthefemuronapanoramic radiographonthelowerlimbsshowingtheangleofthe distalfemoralresectiondeterminedbytheintersectionof

thefemoralmechanicalaxis(FMA)andthefemoral

anatomicalaxis(FAA).

were madebythesame externalevaluatorusingthesame tools.15,17,23

Tocalculatethesamplesize,a95%confidenceintervalwas used,withprecisionof0.3.Forthepurposesofstatistical cal-culations,theunpairedStudent’st-testwasused.Thus,the mean value forthe idealdistalfemoral resectionobtained here was compared with the mean value of 5.7 that had beenobtainedinasimilar,previousstudythatwasconducted onEuropeanpopulationsofosteoarthriticpatientswhohad undergoneTKA.18_The_mean,_standard_deviation_and_median

valuesfortheanglebetweentheFAAandtheFMA(angleof thedistalfemoralcutinTKA),bothoverallanddifferentiated accordingtosexandside,isshowninTable2.

Results

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Table2–Mean,standarddeviationandmedianvaluesfortheanglebetweentheFAAandtheFMA(distalfemoral resectionangleinTKA):overallanddifferentiatedaccordingtosexandside.

Right

Female 5.99 1.24 6 3 9 41 0.588

Male 5.71 1.11 6 3.5 7 7

Total 5.95 1.22 6 3 9 48

Left

Female 6.13 1.42 6 3.5 9 39 0.932

Male 6.17 1.11 6 5 8.5 12

Total 6.14 1.35 6 3.5 9 51

Meanforbothsides

Female 6.02 1.29 6.1 3 9 54 0.726

Male 6.17 1.2 5.9 4 9 12

Total 6.05 1.27 6 3 9 66

Distribution of the distal femoral resection angle in the study

16

14

12

10

8

6

4

2

0

N. patients

2

1 3 4 5 6 7 8 9

Distal femoral resection angle

Fig.2–Histogramshowingthedistributionofthedistal femoralresectionanglesinthestudy.

ThemeanangleformedbytheFAAandtheFMA,which

wasconsideredtobetheangleofthedistalfemoralcutina TKA,was6.05◦_(range:_3–9◦₎_in_the_group_studied_here₍_Fig.₂_). Thedistributionofthisanglebetweenthesexesshowed thatthemeanwasslightlyhigheramongthemen(6.17◦₎_than amongthewomen(6.02◦_),_but_without_statistical_significance (Fig.3)(p=0.726).

Comparison between the mean value obtained in the presentsample(6.05;SD1.27)andthemeanvalueobtainedin literature(5.7◦₎_showed_that_there_was_no_statistical_difference betweenthem(p=0.052).

16

14

12 10

8 6

4

2

0

Distribution of the distal femora resection angle between the sexes

N. patients

Distal femoral resection angle

2

1 3 4 5 6 7 8 9

Male

Female

Fig.3–Histogramshowingthedistributionofthedistal

femoralresectionanglesbetweenmalesandfemales.

Discussion

In Insall’sclassicaltheory ofgap balancing,3,4 _achievement

of postoperativemechanical alignment isconsidered tobe fundamentalforthelongevityofkneeprostheses.Fromthis viewpoint,panoramicradiographsbecomeessentialfor surgi-calplanningandarethemosteffectivemeansfordetermining notonlythefemoral,tibialandwhole-limbmechanicalaxes, butalsotheeffectsofsupportforthem,whichaddsprecision totheresults.15,24_This_is_in_contrast_to_the_theory_of_McGrory

etal.,12_who_advocated_planning_done_only_using_short_films

for kneeswith little deformity,and planning based on the anatomicalaxes.

Despiteallthetheories,thequestionablepracticeof replac-ingpreoperativeplanningwithdistalfemoralbonesectioning atanglesmeasuredempiricallybasedondatapreestablished in the international literatureis well known. Thus,within theBraziliansetting,16_preoperative_planning_has_become_the

exception,eitherbecauseofdifficultyinfindingradiological centersthatarequalifiedtoperformthisprocedureorbecause of the inevitable additional cost. Kapandji25 _and _Maquet26

definedthemeananglebetweentheFAAandtheFMAasa valgusangleof6◦_;_on_the_other_hand,_Moreland_et_al.2_found a valgusangle of4◦_. _In_turn, _Insall _and _Easley27 _described thesamemeasurementasavalgusangleof7◦_and_produced anempirical“confidenceinterval”forthiscut,consistingof avalgusanglerangeof4–7◦_,_always_in_relation_to_the_FAA. However,inthepresentstudy,forstatisticalcomparisonof the meanangleforthedistalfemoralresection,thevalgus angleof5.7◦_was_used,_based_on_the_study_by_Deakin_et_al.,18 whichwasconductedmorerecentlywithmethodologyand epidemiologicalanalysisthatweremoreappropriate.

Thefirstconclusionfromthisstudywasthatthereisno statistical significanceregardingthe angleformedbetween the FAA andthe FMA,incomparingaBrazilianpopulation (6.05)withforeignpopulations(5.7).However,aless percep-tible yet moreimportant conclusion was that if empirical femoralresectioninaccordancewithwhattheinstruments showedweretobechosen,thiswouldleave19.7%ofthe pop-ulationoperatedwithinsufficientalignmentofthelowerlimb, evenifanerrorof3◦_in_the_coronal_plane_were_to_be_considered acceptable.11,12 _These_data_are_convergent_with_what_is_seen

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tomildvalgus(femoral-tibialanglesfromvarusof8◦_to val-gusof1◦_),_which_suggests_that_distal_femoral_resection_with avarusangle>6◦ _should_be_used_for_severe_varus deformi-ties(femoral–tibialangle>varusof8◦₎_and_a_valgus_angle_<₆◦ formoderatetoseverevalgus(femoral-tibialangle>valgusof 1◦_).18

Analysisonthequestionofgendershowedthattherewas nostatisticaldifferencewithinthepopulationstudiedhere, which is coherent with what has been found in the gen-eralpopulation,8,28_but_divergent_from_what_was_found_in_the

osteoarthriticpopulationoftheUnitedKingdom,18_in_which

themeananglewasgreateramongmales.Infact,despitethe lackofstatisticalsignificance,the absolutemean valuefor theangleamongmaleswas substantiallygreater(6.17 ver-sus6.02),whichsuggeststhatifthepopulationstudiedhad beenlarger(whichwasthemostimportantlimitationofthe presentstudy),statisticalsignificancemighthaveensued.

In the light of the above discussion, it can be stated withsimilardegreesofprecisionboththatempiricalfemoral resectionatavalgusangleof6◦_is_appropriate_for_the Brazil-ianpopulationandthatifsurgeonsdonotwishtoexclude asignificantminorityofthepopulationfromthepossibility ofobtaininggoodresultsintermsofalignment,theyshould planthisstageoftheprocedureinanindividualizedmanner. Obviously,theangle offemoralresectionisjustoneofthe manyfactorsthatleadtoappropriatealignment,whichwillbe addedtoothersuchfactorsinobtainingagoodresult.Anerror intheentrypointfortheguidenailintheintercondylararea, forexample,orevenplacementofanailthatisshorterthan whatwasplanned,mayaltertheresultantvalueforthedistal femoralanglethatisobtained,giventhatforthemeasured andconstructedanglestobethesame,thesameanatomical axisneedstobeused,withproximalanddistalpointsequal towhatwasplanned,whichisnotalwayseasytoobtain dur-ingthe operation.ReedandGollish29 _used_a_mathematical

formulabasedonthedivergenceoftheintroduction ofthe femoralnailguideinrelationtotheanatomicalaxisbothat theintercondylarpointofentryandatthemedullary extrem-ity.From this,theydemonstratedthe potentialerrorinthe distalfemoralcutandconcludedthatnotonlyshould radio-graphicpreoperativeplanningbeperformed,butalso,incases ofwidemedullarycanals,intraoperativeradiographsshould beproduced.

Conclusion

Therewasnostatisticallysignificantdifferenceinthemean angleformedbetweentheFMAandtheFAA,betweenmen andwomenintheBrazilianpopulation.Likewise,therewasno statisticaldifferenceinthemeanvalueforthisanglebetween theBrazilianpopulationstudiedhereandtheEuropean popu-lationsofpreviousstudies.TheBrazilianmeananglefound was6.05◦_._Distal_femoral_resection_with_a_valgus_angle_of_5–6◦_, forTKA,isnotcompletelysafefortheBraziliangeriatric pop-ulation.

Conflicts

of

interest

Theauthorsdeclarethattherewerenoconflictsofinterest.

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