w w w . r b o . o r g . b r
Original
Article
Total
knee
arthroplasty
with
computer-assisted
navigation:
an
analysis
of
200
cases
夽
,
夽夽
Marcus
Vinicius
Malheiros
Luzo,
Luiz
Felipe
Morlin
Ambra
∗,
Pedro
Debieux,
Carlos
Eduardo
da
Silveira
Franciozi,
Raquel
Ribeiro
Costi,
Marcelo
de
Toledo
Petrilli,
Marcelo
Seiji
Kubota,
Leonardo
José
Bernardes
Albertoni,
Antônio
Altenor
Bessa
de
Queiroz,
Fábio
Pacheco
Ferreira,
Geraldo
Sérgio
de
Mello
Granata
Júnior,
Mário
Carneiro
Filho
OrthopedicsandTraumatologyDepartment,UniversidadeFederaldeSãoPaulo,SãoPaulo,SP,Brazil
a
r
t
i
c
l
e
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n
f
o
Articlehistory:
Received5September2012 Accepted15January2013 Availableonline18March2014
Keywords:
Arthroplastyreplacement Knee
Computer-assistedsurgery
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b
s
t
r
a
c
t
Objective:toevaluatetheresultsfromsurgerywithcomputer-assistednavigationincases oftotalkneearthroplasty.
Method:a totalof 196patientswhounderwent total kneearthroplastywith computer-assistednavigationwereevaluated.Theextensionandflexionspaces(gaps)wereevaluated duringtheoperationandthealignmentaftertheoperationwasassessed.TheKneeSociety Score(KSS)questionnaireforassessingpatient’sfunctionwasappliedpreoperativelyand postoperativelyafterameanfollow-upof22months.
Results:inall,86.7%ofthepatientspresentedgoodalignmentofthemechanicalaxis(less than3◦ofvarusorvalgusinrelationtothemechanicalaxis)and96.4%ofthepatients
presentedbalancedflexionandextensiongaps.Beforetheoperation,97%ofthepatients presentedpoororinsufficientKSS,butaftertheoperation,77.6%presentedgoodorexcellent KSS.
Conclusion: the navigation system made it possible to achieve aligned and balanced implants, withnotablefunctionalimprovementamongthepatients.Itwasfoundtobe useful inassessing, understandingandimproving knowledgein relationtoperforming arthroplastyprocedures.
©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.
Artroplastia
total
do
joelho
auxiliada
por
navegac¸ão:
análise
de
200
casos
Palavras-chave:
Artroplastiadesubstituic¸ão
r
e
s
u
m
o
Objetivo:avaliarosresultadosdascirurgiasassistidaspornavegac¸ão(CAN)nasartroplastias totaisdejoelho.
夽Pleasecitethisarticleas:LuzoMVM,AmbraLFM,DebieuxP,FrancioziCES,CostiRR,PetrilliMT,etal.Artroplastiatotaldojoelho
auxiliadapornavegac¸ão:análisede200casos.RevBrasOrtop.2014;49:149–153.
夽夽WorkperformedintheDepartmentofOrthopedicsandTraumatology,EscolaPaulistadeMedicina,FederalUniversityofSãoPaulo,
SãoPaulo,SP,Brazil.
∗ Correspondingauthor.
E-mail:felipeambra71@gmail.com(L.F.M.Ambra).
Joelho
Cirurgiaassistidapor computador
Método:foramavaliados196pacientessubmetidosàartroplastiatotaldejoelhocomauxílio danavegac¸ãoporcomputador.Avaliadosnointraoperatórioosespac¸os(gaps)deextensão edeflexão,oalinhamentopós-operatórioeoquestionáriofuncionaldaKneeSocietyScore (KSS)pré-operatórioepós-operatóriocomseguimentomédiode22meses.
Resultados: dospacientes,86,7%apresentarambomalinhamentodoeixomecânico(dentro de3◦devaroouvalgoemrelac¸ãoaoeixomecânico)e96,4%apresentaramambososgaps
deflexãoeextensãobalanceados.Nopré-operatório,97%dospacientesapresentavamKSS funcionalruimouinsuficiente,nopós-operatório77,6%apresentavamKSSfuncionalbom ouexcelente.
Conclusão:anavegac¸ãoproporcionouaobtenc¸ãodeimplantesalinhadosebalanceadoscom importantemelhoriadafunc¸ãonospacientes.Foramevidenciadossuautilidadenoestudo, oentendimentoeoaperfeic¸oamentodoconhecimentonaexecuc¸ãodasartroplastias.
©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Todososdireitosreservados.
Introduction
Totalknee arthroplasty (TKA) isa safeand effective treat-ment for restoring function and relieving pain inpatients with gonarthrosis (knee osteoarthrosis). With the aging of the population, there has been a tendency toward increasingnumbers ofpatientswith this pathological con-dition and greater demand for TKA. Within this scenario, searching for new options that might contribute toward improvingtheresultsandrefiningtheprocedureisvery valu-able.
Success in knee arthroplasty is influenced by fac-tors relating to the patient, type of implant and sur-gical technique. In relation to the procedure, adequate positioning of the components and consequent good alignment of the limb are important prognostic fac-tors. Incorrect positioning may affect implant functioning, increase the wear on the material and cause loosening of the prosthesis. Studies have demonstrated that align-ing the components within 3◦ of the normal mechanical axis diminishes the risks of irregular wear and early loosening.1
Thedevelopmentofinstrumentswithintramedullaryand extramedullaryguideshasincreasedtheaccuracyofimplant alignment, but alignment errors still occur. Tibial compo-nent alignment errors exceeding 3◦ with the use of an extramedullaryguideweredescribedin21.3%ofthecasesin oneseries.2
Navigationwasdevelopedasa toolto increasethe pre-cision ofcorrect positioning ofthe implants in total knee arthroplasty.Itisareproducibleandprecisemethodforbone resection and ligament balancing, and isalso accurate for evaluatinglimbalignment.3Asurveyconductedamong mem-bersofthe EuropeanSocietyofSports Traumatology, Knee Surgeryand Arthroscopyandthe SwissOrthopedicSociety showed that 33.1% of surgeons use navigation in at least 50%ofTKAproceduresand25%useitinmorethan75%of them.4
Inthisstudy,wediscusstheshort-termresultsfrom pri-mary total knee prostheses that were implanted with the aidofcomputer-guidednavigation, includingevaluationsof thepostoperativemechanicalaxisandpostoperativefunction overtheshortterm.
Methods
Studydesignandsamplecharacteristics
AfterapprovalbytheResearchEthicsCommitteeofHospital SãoPaulo(Unifesp),200patientswereselectedconsecutively to undergo TKA.All the patients presentedindicationsfor arthroplastyinconformitywiththeinclusionandexclusion criteriadescribedbelow.Thisstudywasthuscharacterizedas aprospectivecaseseries.
Patients with a radiographic diagnosis of primary osteoarthrosis who had not presented improvement in theirpainandfunctionalconditionsafteraminimumofsix months of conservative treatment were included. Revision arthroplastypatientsandthosewithactiveinfectionorloss ofextensormechanismfunctionwereexcluded.
Surgicaltechnique
After a medianlongitudinal skin incision had been made, medialparapatellararthrotomywasperformed.Afterthejoint hadbeenexposed,pinswithpassivereflectivesensorswere implantedintheanteromedialregionofthedistalfemurand proximaltibia,forthenavigatortoread.Thereferencepoints requestedbythenavigatorwerethengathered(femoral inter-condylarcenter,centerofhiprotation,internalandexternal rotation ofthe tibia,knee rangeofmotionbetween0◦ and 90◦,centerofanklerotation,posteriorlimitsofthefemoral condyles,anteriorfemoralcorticalbone,centerofthemedial andlateralplateaus,centeroftheproximaltibia,centerofthe ankle,centersofthelateralandmedialmalleoliandjoint incli-nationofthefemur).Theinformationrelatingtothepatient’s anatomyandjointrangesofmotionweretheninputtothe software.
thefemoralcutwasdone.Atthistime,usingthedataonlimb alignment,balancingofflexionandextensiongaps,femoral rotationandfemoraljointinclination,thesizeofthe prosthe-sisanditsbestpositioningcouldbedefined,alwaysinrelation tothemechanicalaxis.
Afterthefemoral,tibialandpatellarcutshadbeenmade, therespectivetrialcomponentsweretested,andthequality ofthelimbalignmentinrelationtothemechanicalaxisin thecoronalandsagittalplanesandadequacyofthebalancing fortheplannedimplantswereagaininvestigatedbymeansof thenavigator.Allthesedatawererecordedandstored.Allthe componentswerethenplacedappropriatelyandcemented, includingthepatellarcomponent(thepatellaewerereplaced). Thedatawere againgathered,confirmedand,atthistime, recordedasfinal.Thisconcludedthenavigatedstageofthe procedureandthesurgicalsitewasthenclosed.Thedatawere dulyrecordedandsubsequentlycomparedinordertoproduce thisstudy.
Alltheoperationswereperformedbythesamesurgeon. The implant used was the Columbus PS prosthesis and the navigator used was the Orthopilot 4 in all cases. No intramedullaryguideswereused.Thebonecutsandallthe otherprocedureswerenavigationassisted.
Extractionmethodfordataandvariables
Toconductthepresentstudy,themechanicalaxisofthelower limb(initialandfinal)andtheflexionandextensiongaps (lat-eraland medial)were measured intraoperativelybymeans ofnavigation,asdescribedabove.Allthedatawereobtained beforeandafterperformingthebonecutsand/orpositioning theprosthesis,takingthefirsttobe“initial”andthesecond, “final”.
The alignment and balancing obtained intraoperatively wereverifiedbasedonthemechanicalaxisofthelowerlimbs and the final flexion and extension gaps (in millimeters), respectively.Kneeswereconsideredtobewellalignedif,after arthroplasty,theypresentednotmorethan3◦ofdeviationin thecoronalplane.1Inrelationtothefinalflexionand exten-sion gaps, knees that presented a difference between the medialandlateralgapofnotmorethan3mmwereconsidered tobalanced.
Toevaluatethefunctionalresult,theKneeSocietyScore (KSS) was used. Thequestionnaire was appliedbefore the operation and in the sixth month after the operation, to all the patients. The scoring scale was from 0 to 100, dividedintofourcategories:excellent(morethan84points), good (70–84), insufficient (60–69), and poor (less than 60 points).5–7
Statisticalmethods
Thepatients’flexionandextensiongapsandthemechanical axis were described using absolute or relative frequen-cies.
The KSS was described using summary measurements (mean,standarddeviation,minimumandmaximum)before andafterthetreatmentand comparisonsweremadeusing thepairedWilcoxontest.
Table1–Evaluationofbalancingandalignment.
Variable n %
Balancingoftheflexiongap
No 5 2.6
Yes 191 97.4
Balancingoftheextensiongap
No 2 1.0
Yes 194 99.0
Alignmentofthemechanicalaxis
No 26 13.3
Yes 170 86.7
Balancingoftheflexion/extensiongap
No 7 3.6
Yes 189 96.4
Balancingofthegapandalignmentofthemechanicalaxis
No 33 16.8
Yes 163 83.2
Total 196 100
The pre- and postoperative KSS categories were also describedandthechangesincategorieswerecomparedusing thepairedWilcoxontest.
Results
Ofthe200patientsincludedinthisstudy,11.7%(23)weremen, 88.3% (104) knees wereright knees and themean age was 68.7years(25–88years).Fourpatientswereexcludedfromthe study:onedidnotmeettheinclusioncriteriaandthreewere excludedbecauseofdata-gatheringmistakes.
In96.4%ofthepatients,therelationshipbetweenthe lat-eral and medial gapswas balanced both inflexion and in extension.Adequate alignmentofthemechanicalaxis(not morethan3◦ofvarusorvalgusinrelationtothemechanical
axis) wasattainedin86.7%ofthepatients. Idealbalancing ofthe gaps inassociation with adequate alignment ofthe mechanicalaxiswasreachedin83.2%ofthepatients(Table1). Inevaluatingthesagittalaxis,theidealwasconsideredto benotmorethan5◦offlexionor10◦ofhyperextension.Thus, only3%(sixpatients)presentedflexion.Inthesepatients,the meanwas7◦andthemaximumwas9◦.Noneofthepatients presentedhyperextensionabovethelimitconsidered.
The mean preoperative functional KSSwas 44.13 (min-imum of 15 and maximum of 70). Six months after the operation, themean was 76.85(minimumof30 and maxi-mumof100)(Table2).Beforetheoperation,97%ofthepatients presentedpoororinsufficientfunctionalKSS;afterthe oper-ation,77.6%presentedgoodorexcellentKSS(Tables3and4). Thus,therewasastatisticaldifferencebetweenthetwotimes (p<0.001).
Discussion
Table2–Summarymeasurementsofthepre-andpostoperativefunctionalKSS.
Variable Mean SD Median Minimum Maximum n p
Pre-opKSS 44.13 11.58 45 15 70 196 <0.001
Post-opKSS 76.85 13.15 80 30 100 196
Table3–Comparisonofpreoperativeandpostoperative KSSaccordingtocategory.
KSS Preoperative Postoperative p
n % n %
Poor 173 88.3 19 9.7 <0.001
Insufficient 17 8.7 25 12.8
Good 6 3.1 78 39.8
Excellent 0 0.0 74 37.8
Total 196 100 196 100
theasymmetricalpressureexertedonthecomponentswhen subjectedtoloads.
In this context, navigation-assisted surgery provides an additiontosurgeons’experience:anotherveryimportant fac-torindetermining thequality ofthe result, withobjective methodsformeasuringthisalignment.Ontheother hand, despitetheunequivocalbenefitbrought bythis technology, which hasbeen attestedthrough a study ofhighest value in the literature, i.e. the meta-analysis conducted by Het-aimishetal.9ontheradiographicalignmentofcomponents, theinherentclinicalimpactofthistechniquehasyettobe proven.
Overa minimumfollow-up offive years,Ishida et al.10 foundbetterclinicalandradiographicresultsthroughusing navigation-assistedsurgerythanthroughusingthetraditional technique.ThisresultwasalsofoundinthestudybyLongstaff et al.,11 who were able tocorrelate correctalignment with betterclinicalresultsand earlyrehabilitation.Ontheother hand,therearealsomanyreportsintheliteraturethatdonot makeanyconnectionbetweenbetteralignmentandthe clin-icalresult,12,13 which showsthat thereisa needtodesign studies ofbetterquality withlonger follow-up, inorder to evaluatetheclinicalresults.
Inastudyon80TKAprocedures,Bathisetal.14achieved adequate alignmentin78% ofthecasesusing the conven-tionaltechnique.Martinetal.15reachedanidealalignment in76%ofthe 100prosthesesimplantedusingconventional instruments.Inastudyon500TKAprocedures,Tingartetal.16 achieved adequate alignment in 74% using conventional
guides.Thus,incomparisonwiththeliterature,navigationin thisstudyprovidedahigherpercentageofalignedprostheses: 86.7%.
Other thanthealignment,itisknownthattheligament balanceisafundamentalstructureinconstructingadequate resultsinTKAprocedures.Thekinematicidealisforthereto beasymmetricalbalancebetweenthespacesobtainedin flex-ionandextension.Failureinthisregardisshownbylimitation ofthe rangeofmotion,accelerated wearonthe polyethyl-eneandalterationstopatellarexcursions.17Navigationisa usefulinstrumentforsuppressingsubjectiveelementsduring thebalancing,andthisisitspointofgreatestbenefit, accord-ingtovariousauthors.Here,thisinstrument,withtheuseof objectivemeasurements,makesitpossibletoreplace “sym-metrical laxity” with“symmetrymeasured inmillimeters”, thusbestowingprecisionontheclassicalapproximation.In thestudy presentedhere,constructionoftheTKAfollowed theconceptspreestablishedthroughthegaptechnique.A bal-ancewasachievedinrelationtobothofthegapsin96.4%of thecasesoperated.
In a similar manner, other authors have defended the hypothesisthatthroughthismethod,greatercoronal stabil-ity and alignment isattained.18,19 On the other hand, the fundamentalpointisthepeculiarcapacityofthetechnique toinfluencethealignmentandbalancingonacase-by-case basis,accordingtothesurgeon’scriteria.Inthepresentstudy, despitetheidealligamentbalancingseenwithsymmetrical gaps,thisdidnotresultdirectlyinaneutralmechanicalaxis inallthecases.Onthecontrary,neutralalignmentwasonly attainedwhentheligamentbalancingwassymmetrical.
Insomespecificcases,sacrificingthealignmentmightbe considered,i.e. asmall deviationinrelation totheneutral mechanical axismight beconsciouslyallowed.This would bedonetoprioritizetheligamentbalance,especiallyincases ofgreatdeformityinwhichreestablishmentofaneutralaxis wouldalreadybeadebatablematter.Slightvariationinthe mechanicalaxissometimesbecomestheonlywayand,albeit undesirable,essentialforobtainingsymmetricalgaps. How-ever, balanced ligament tensioning improves the dynamic alignment ofTKAprocedures,andnavigation isatoolthat aidsinthisobjective.20
Table4–Evaluationofthepostoperativecategoryinrelationtothepreoperativecategory.
PreoperativeKSS PostoperativeKSS
Poor Insufficient Good Excellent Total p
n % n % n % n % n %
Poor 17 8.7 21 10.7 68 34.7 67 34.2 173 88.3 <0.001
Insufficient 1 0.5 3 1.5 7 3.6 6 3.1 17 8.7
Good 1 0.5 1 0.5 3 1.5 1 0.5 6 3.1
Excellent 0 0.0 0 0.0 0 0.0 0 0.0 0 0.0
Ritteretal.21demonstratedthatpatientswithflexion con-tracturegreater than5◦ orhyperextension greaterthan 10◦ presentedgreater risk of pain and poor functional results assessedusing the KSS.In the present study,only3% (six patients)presentedpostoperativeflexioncontracturegreater than5◦,andnoneofthempresentedhyperextensiongreater than10◦.Wedidnotfindanycorrelationbetweenthesedata andtheKSS.
Thelargepopulationevaluatedand theprecisionofthe datagatheredwereinsufficienttocoverthemethodological limitations of the study presented here. This was a cases series:itdidnothaveacontrolgroupandthestudysubjects werenotrandomized.Theminimumclinicalobservationwas sixmonths,whichcanbeconsideredtobeashorttimewithin theevolutionofarthroplastyresults.Nonetheless,thisstudy attaineditsobjectivewithregardtodemonstratingthe con-tributionofnavigationtowardtrainingandaccumulationof knowledgeonthistopic.
Conclusion
Navigationmadeitpossibletoachievealignedandbalanced implantswithsignificantfunctionalimprovementamongthe patients.Itwasfoundtobeusefulforevaluation, understand-ingandknowledgerefinementregardingimplementationof arthroplasty.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
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