w w w . r b o . o r g . b r
Original
article
Dimensional
analysis
of
total
hip
arthroplasty
polyethylenes
夽
Carlos
Roberto
Schwartsmann
a,b,∗,
Leandro
de
Freitas
Spinelli
b,
Leonardo
Carbonera
Boschin
b,
Ramiro
Zilles
Gonc¸alves
b,
Anthony
Kerbes
Yépez
b,
Telmo
Roberto
Strohaecker
c,
Ralf
Wellis
de
Souza
caUniversidadeFederaldeCiênciasdeSaúdedePortoAlegre,PortoAlegre,RS,Brazil
bServic¸odeOrtopediaeTraumatologia,ComplexoHospitalardaSantaCasadePortoAlegre,PortoAlegre,RS,Brazil
cLaboratóriodeMetalurgiaFísica,UniversidadeFederaldoRioGrandedoSul,PortoAlegre,RS,Brazil
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received9August2012 Accepted3October2012
Keywords:
Arthroplasty,replacement,hip Acetabulum
Polyethylene
a
b
s
t
r
a
c
t
Objective:Thispaperperformsadimensionalanalysisofdifferenttotalhiparthroplasty polyethylenes,cementedandnon-cemented,Brazilianmadeandimported.
Methods:It wasconsidered acetabularcomponentswith 50mm forthe 28mm femoral heads.Dimensionalanalysiswasperformedona3DcoordinateCarl-Zeissroboticdevice. Polyethylenethicknessanditsexternalmeasurements(maximumdiameteranddiameter forthefemoralhead)weremeasured.
Results:Theminimumthicknessofthepolyethylenewasguaranteedonalltested compo-nents.Thethicknessofcementedacetabularvariedfrom19.185mmto25.358mm,while thethicknessofthenon-cementedacetabularvariedfrom12.451mmto19.232mm.The thicknesswas27.96%lowerinnon-cementedacetabularcomponents.Withrespecttothe polyethyleneacetabularcavitythatreceivesthefemoralhead,allinternaldiametersexhibit atleast28mm.Inrelationtothemaximumouterdiameterofthepolyethylene,onlyone cementedacetabularcomponentreached50mmindiameter.
Conclusions:Therearelargedifferencesinmeasurementsbetweenbrandsandmodels ana-lyzed.Cementlessacetabularcomponentshavethesmallerthickness.Thediametersof non-cementedacetabularwerealsolowerthanthosecementedattheexpenseoftheir needtoinsertintothemetal-back.
©2013SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.
夽
WorkperformedintheHospitalComplexofSantaCasadePortoAlegreandinthePhysicalMetallurgyLaboratory,UniversidadeFederal doRioGrandedoSul,PortoAlegre,RS,Brazil.
∗ Correspondingauthor.
E-mail:[email protected](C.R.Schwartsmann).
2255-4971/$–seefrontmatter©2013SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditoraLtda.Allrightsreserved.
Análise
dimensional
de
diferentes
acetábulos
usados
na
artroplastia
total
do
quadril
Palavras-chave:
Artroplastiadequadril Acetábulo
Polietileno
r
e
s
u
m
o
Objetivo: Opresenteestudofazumaanálisedimensionaldosdiferentesacetábulos cimen-tadosenãocimentados,nacionaiseimportados,disponíveisnomercadonacionalpara artroplastiatotaldoquadril.
Métodos: Foramconsideradososacetábulosde50mm,destinadosàscabec¸asfemoraisde 28mm.Asanálisesdimensionaisforamfeitasemumequipamentotridimensionalrobótico demedic¸ãoporcoordenadas.Avaliou-seamenorespessuradopolietilenoesuasmedidas externas(diâmetrodoespac¸oparaacabec¸afemoralediâmetromáximodoacetábulo).
Resultados: Aespessuramínimadopolietilenofoigarantidaemtodososcomponentes tes-tados.Aespessuradosacetábuloscimentadosvarioude19,185mma25,358mm,enquanto aespessuradosacetábulosnãocimentadosvarioude12,451mma19,232mmAespessura foiemmédia27,96%menornosacetábulosnãocimentados.Emrelac¸ãoàcavidade acetab-ulardopolietilenoquerecebeacabec¸afemoral,todososdiâmetrosinternosapresentaram pelomenos28mm.Emrelac¸ãoaodiâmetroexternomáximodopolietileno,apenasum acetábulocimentadoatingiuos50mmdediâmetro.
Conclusões: Observaram-segrandesdiferenc¸asnasmedidasentreasmarcaseosmodelos analisados.Osacetábulosnãocimentadostêmumaespessuramenor.Osdiâmetrosdos acetábulosnãocimentadostambémforammenoresdoqueoscimentados,àcustadesua necessidadedeinserc¸ãonometal-back.
©2013SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Todososdireitosreservados.
Introduction
Hipsurgerycontinuestofaceconstantchallengesduetothe growingvolumeofpatientsandincreasingcosts,andbecause ofcontroversiesregardingthereliabilityandperformanceof theimplants.1,2Totalhiparthroplastyhasbeenincreasingly
indicatedforyoungerandmoreactivepatients.Theresults fromhiparthroplastyhavebeenshowntobeexcellentamong moreelderlypatients.However,amongyoungerpatients(<40 years),thefailurerateoverafive-yearperiodisbetween21% and 28%.3–7 Theclassical combination ofmetal articulated
withultra-highmolecularweightpolyethylenecontinuesto bethemostwidelyusedtype,1anditwillcontinuetobesofor
manyyearstocome,withtheadventofcrosslinked polyeth-ylene.
Themetal–polyethylenesurfaceisinexpensiveandenables immediate weight-bearing. Moreover, surgeons have wide experiencewiththismethodandthepresent-dayacetabula. However,thismethodhasthedisadvantagethatthecement agesandprogressivelydisintegrates.Schulteetal.,8 Keener
etal.,9Callaghanetal.10andBuckwalteretal.11 foundthat
69–90%oftheirresultsusingCharnleyprosthesesweregood, with20–30yearsoffollow-up.Wroblewskietal.12reportedan
evenlongerfollow-upperiod(30–40years)forCharnley pros-theses,with90%goodresults.
Wearingout isthe greatestobstacle tolongevityamong polyethyleneprostheses.Youngand activepatients, partic-ularly males under the age of55 years, are the ones who presentthegreatestriskofacceleratedwear.1Thethickness
ofthepolyethylenehasbeenreportedtobeoneofthefactors thatcausewear.AccordingtoBarteletal.,13thestressesin
thepolyethylenebecomegreaterifitsthicknessislessthan
5mm,whichleadstoanunacceptableriskofprematurewear. Thereforethiscriticalthicknessshouldbeforeseeninorderto avoidintensewear.Forthisreason,precisesizeassessment needstobedoneatthetimeofmanufacturingtheimplants. Theaimofthepresentstudywastomakeananalysisonthe dimensionsofdifferentcementedandnon-cemented50mm acetabulathataremadeinBrazilorimported.
Materials
and
methods
Thepresentstudymadeadimensionalassessmenton acetab-ula thatare availableontheBrazilianmarket,involving 11 Brazilian and imported components of a wide variety of brandsandmodels(bothcementedandnon-cementedtypes). Thesewerethennamedaccordingtotheirmanufacturersas A,B,C,etc.,forethicalandlegalreasons.Inorderto stan-dardizethisstudy,only50mmacetabuladestinedfor28mm femoralheadsweretakenintoconsideration.
Fig.1–CarlZeissdeviceusedformakingthe measurements:(a)ingeneralviewand(b)focused.
externalmeasurementsobtained(diameterofthespacefor thefemoralheadandthemaximumoveralldiameterofthe acetabulum)werethencomparedwithmeasurementsmade byprecisionpachymeters,takingthemeanofthree measure-ments.
Results
Table1presentstheresultsobtainedforthedifferent
man-ufacturers in relation to the cemented and non-cemented components.Theminimumthicknessofthepolyethylenewas assuredinall thecomponents tested.However,takinginto consideration thedifferent acetabula,largevariationswere observed.ThethicknessoftheBraziliancementedacetabula rangedfrom 19.185mmto25.358mm(meanof22.593mm), while the thickness of the imported cemented acetabula rangedfrom 21.058mmto23.143mm(meanof22.053mm). The thickness of the Brazilian non-cemented acetabula rangedfrom 15.444mmto19.232mm(meanof17.338mm), whilethethicknessoftheimportednon-cementedacetabula
Table1–Measurementsonthedifferentacetabula. Thickness
(mm)
Internaldiameter (mm)
Externaldiameter (mm)
Braziliancementedacetabula
A 23.236 28.1899 50.0321
A 19.185 28.2313 49.6687
B 25.358 28.2668 49.8918
Mean 22.593 28.2293 49.8642
Deviation 3.1363 0.0385 0.1833
Braziliannon-cementedacetabula
A 19.232 28.1200 45.3300
C 15.444 28.2836 47.9197
Mean 17.338 28.2018 46.62485
Deviation 2.6785 0.1157 1.8312
Importedcementedacetabula
D 21.959 28.1114 49.5826
E 23.143 28.2846 49.7334
F 21.058 28.4393 47.7133
Mean 22.053 28.278 49.010
Deviation 1.0457 0.1640 1.1253
Importednon-cementedacetabula
D 14.356 28.1689 43.1000
E 18.929 28.1775 45.7739
F 12.451 28.0620 45.9389
Mean 15.245 28.136 44.938
Deviation 3.3293 0.0643 1.5935
rangedfrom12.451mmto18.929mm(meanof15.245mm). Takingalltheacetabulaintoconsideration,themean thick-ness ofthe cemented acetabulawas 22.323mm,while the thickness of the non-cemented acetabula was 16.082mm. Thus,thethicknessofthenon-cementedacetabulawason average27.96%less.
In relation to the polyethylene acetabular cavity that receives the femoralhead, all the internal diameters were atleast28mm.Theclosest-fittingcavitywasinanimported non-cemented prosthesis (28.062mm), whilethe one with the greatest play was an imported cemented acetabulum (28.439mm).
Inrelationtothemaximumexternaldiameterofthe poly-ethylene,onlyoneBraziliancementedacetabulumreacheda diameterof50mm(50.032mm),andthediameterswentdown toassmallas43.100mm,whichwasfoundinanimported non-cemented prosthesis. The diameters of the Brazilian cemented acetabula ranged from 49.668mm to 50.032mm (meanof49.864mm),whiletheimportedcementedacetabula rangedfrom47.713mmto49.733mm(meanof49.010mm). The diameters of the Brazilian non-cemented acetabula rangedfrom45.330mmto47.919mm(meanof46.624mm), while the imported non-cemented acetabula ranged from 43.100to45.938mm(meanof44.938mm).
Discussion
Huo et al.2 reportedthat the rates ofwear forcrosslinked
reducetheriskofdislocation.Despitethe cleardifferences inthe dimensionsdetermined forthe pieces, it has to be takeninto accountthatnotall thepolyethylenepiecesare manufacturedwithcrosslinkingand,eveniftheywere, differ-entdegreesofradiationmightintroducedifferentresistances. Howeverthisfactorwasnotevaluatedinthepresentstudy. Theaimherewastoevaluatethedimensionalcharacteristics asameansofassessingthecompatibilityoftheseelements.
Bartel et al.13 showed that a minimum thickness of
5mm was necessary in order to avoidexcessive wear. We attemptedtoestablishthisaffirmationinthepresentstudy andfoundthatalltheacetabulahadmeasurementsgreater thanthisvalue.Charnley,inhisfirststudies,concludedthat thewearonconventionalacetabulawas0.1mm/year. Glyn-Jones etal.14 analyzedthe wearon the polyethylenein54
totalprosthesesandobservedthatcrosslinkedpolyethylene wore downat 0.06mm/year, while finding the same value as seen by Charnley in conventional acetabula. McCalden et al.15 observed even smaller values in a randomized
prospectivestudy comparing conventional and crosslinked polyethylenepieces:0.05mm/yearand0.003mm/year, respec-tively. Similar results were reported by Thomas et al.16:
0.005mm/yearforcrosslinkedpolyethyleneand0.037for con-ventional polyethylene.Woolson and Murphy17 and Gaffey
et al.18 evaluated patients with Harris–Galante prostheses
and observed wear of 0.14–0.15mm/year. Stilling et al.,19
Kampa et al.,20 Mutimer et al.,21 Datir and Angus22 and
Emmsetal.23evaluatednon-cementedprosthesesand
con-cludedthatthewearonthepolyethylenerangedfrom0.12to 0.28mm/year.Witteetal.24evaluatedtheSpotorno
prosthe-sisand observed0.31mm/year. Morerecently,Kurtzetal.25
conducted a systematic review on the literature and con-cludedthatcrosslinkedpolyethylenepresentedmeanwearof 0.042mm/yearandconventionalpolyethylene0.137mm/year. CatonandPrudhon26recentlyconductedareviewon
Charn-leyprosthesesoveralongfollow-upperiodandcametothe sameconclusionasalreadydemonstratedbyCharnley him-self,i.e.meanwearof0.1mm/year.Fromanextensivereview oftheliterature,Clementetal.27concludedthattherewasno
evidenceintheliteraturetoshowthatnon-cemented acetab-ula would present betterresults than cemented acetabula. In their analysis on all ages and indications, they con-cluded that cemented acetabula continued to be the gold standard.In relation tonew materials, Gottliebsenet al.28
analyzed non-cemented arthroplasty procedures with and without hydroxyapatite and concluded that implants with hydroxyapatiteworeoutmorerapidly,at0.18mm/year,versus 0.12mm/year. Dahlet al.29 comparedcemented prostheses
withceramic headsand withchromium–cobalt heads and observedthatthewearrateintheformerwas0.05mm/year andthelatter,0.1mm/year.Thus,non-cementedpolyethylene piecespresentedgreaterwear,whichmayhavebeenrelated totheir smaller thickness, asalsoobserved inthe present study.
Furthermore, determination of the dimensions is also importantwhen a femoralcomponent is exchanged, with placementofanewhead.Itneedstobeaskedwhetherthis willreallyhavethesamediameterastheoldoneandthus, whetheritwillfitperfectlywithoutcausingfrictionand par-ticles.Likewise,itneedstobeaskedwhetheranacetabulum
ofdiameter50mm,forexample,fromonecompanyisequal tooneof50mmfromanothercompany.Thisstudyshowed thatnotalltheheadswerecompatible,giventhatalthough theywerearoundthesizedesiredintheplanning,thisspace presentedsmallvariations,whichmighthavebeenenough foraperfectfitbetweendifferentbrandstobeachieved.In thesameway,forthecementedcomponents,itwasobserved thatnotallthe largestdiameters(50mm)werereallywhat wasclaimed.Inasimilarstudy,butonpolyethylenepiecesfor knee arthroplasty,Schwartsmannetal.30 observedthatthe
thicknessofthepolyethylenepiecewasnotstatedcorrectly bythemanufacturers.Theseauthorsobservedthatthe mea-surementsfoundweresmallerthanthespecificationsofeach ofthemanufacturers,andthattheimportedpolymerswere notsuperiortotheBrazilianonesregardingthickness.Similar resultswereobservedinthepresentstudy,butforacetabula. Inthecaseofnon-cementedcomponents,futurestudies shouldtakeintoconsiderationtheacetabuluminthemetal dome atthe timeofmeasuring thelargest diameters. The thicknessesofthesepolyethylenepieceswere smallerthan thoseofthecementedcomponents,whichmayexplainwhy therewasgreaterosteolysisinthenon-cementedarthroplasty procedures. Mall et al.31 analyzedcrosslinked and
conven-tionalpolyethylenepiecesand,afterfiveyearsoffollow-up, foundosteolysisinonly2%ofthefirsttypebut24%ofthe secondtype.
Itshouldbeborneinmindthatinthepresentstudy,wedid notdiscussthequalityoftheimplants,whichisafactorthat mightexplainthegenerallysmallerthicknessoftheimported components.Itcouldbeaskedwhetherthiswasbecausethe polyethylenewasofbetterquality,orwhetherthiswasdoneas aneconomymeasureinthemanufacturingprocess. Nonethe-less,thespacesdestinedforarticulationofthefemoralheads seemstopresentgreaterstandardization,withfewer discrep-ancies,eventhoughthereisincompatibilitybetweenbrands andmodels.
Conclusion
Thisdimensionalanalysisontheacetabulaavailableonthe Brazilian market showed large differences between brands andmodels.Themeasurementofa50mmacetabulumwas rarelyfound,eitherincementedorinnon-cemented polyeth-ylenepieces,andeitherinBrazilianorimportedpieces.The non-cemented acetabulahad smallerthickness, by around 27.96%.Thediametersofnon-cementedacetabulawerealso smallerthanthoseofcementedacetabula,butattheexpense oftheneedforinsertioninthemetalback.
Newstudiesareneededtoinvestigateallbrands,allsizes and allmodels,andalsowhetherthereareany differences betweenbatchesfromthesamecompany.Thequalityofthe implantsandtheirlevelofcrosslinkingwerenotanalyzedin thepresentstudy.
Conflicts
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