Rev. bras. ortop. vol.50 número1

r e v b r a s o r t o p . 2015;50(1):114–116

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

Case

report

Spontaneous

dislocation

of

the

polyethylene

component

following

knee

revision

arthroplasty:

case

report

夽

Eduardo

Zaniol

Migon

_,

_Geraldo

_Luiz

_Schuck

_de

_Freitas,

_Marcos

_Wainberg

_Rodrigues,

Gustavo

Kaempf

de

Oliveira,

Luis

Gustavo

Morato

Pinto

de

Almeida,

Carlos

Roberto

Schwartsmann

OrthopedicsandTraumatologyService,SantaCasadePortoAlegre,PortoAlegre,RS,Brazil

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t

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c

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e

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n

f

o

Articlehistory:

Received31January2014 Accepted11February2014 Availableonline29December2014

Keywords: Kneearthroplasty Polyethylene Prosthesisfailure

a

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c

t

Dislocationofthepolyethylenecomponentinkneearthroplastyisararecomplication.The maintriggeringfactorisfailureofthelockingmechanism,whichmayresultfromtechnical errorsofinsertion,traumaorevenimplantfailure.Here,acaseofdislocationofthe poly-ethylenecomponentfromthetibialbase,nineyearsafterrevisionarthroplasty,isreported. ItisbelievedthatthisisthefirstsuchcasereportedintheBrazilianliterature.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

Luxac¸ão

espontânea

do

polietileno

após

artroplastia

de

revisão

de

joelho:

relato

de

caso

Palavras-chave: Artroplastiadojoelho Polietileno

Falhadeprótese

r

e

s

u

m

o

Aluxac¸ãodopolietilenoemartroplastiadojoelhoéumacomplicac¸ãorara.Oprincipalfator desencadeanteéafalhanomecanismodetravamento,quepodeserdecorrentedeerros técnicosnainserc¸ão,dotraumaouaindadefalhadoimplante.Osautoresrelatamcaso deluxac¸ãodopolietilenoapartirdabasetibial,noveanosapósartroplastiaderevisão. Acredita-sequesejaoprimeirocasorelatadonaliteraturanacional.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevierEditora Ltda.Todososdireitosreservados.

夽

WorkdevelopedattheOrthopedicsandTraumatologyService,SantaCasadeMisericórdiadePortoAlegre,RS,Brazil.

∗ _{Correspondingauthor.}

E-mail:edumigon@hotmail.com(E.Z.Migon). http://dx.doi.org/10.1016/j.rboe.2014.12.002

rev bras ortop.2015;50(1):114–116

115

Introduction

Totalkneearthroplastyhasbeenreportedtobeoneofthemost successful orthopedic procedures, with implant longevity greaterthan15yearsinaround90%ofthecases.1,2_Amongthe

complicationsmostcommonlyreported,problemsrelatingto healingoftheoperative wound,infection,thromboembolic disorders, postoperative stiffness, periprosthetic fractures, alterations to patellar tracking, osteolysis, aseptic loosen-ing,instabilityandpolyethylenewearcanbehighlighted.3,4

Althoughthepolyethylenecomponentissubjectedtocyclical stresswiththepossibilityoffailuresecondarytofatigue, dislo-cationofthiscomponentisaveryrareevent.4,5_{Here,wereport}

acaseofthis,whichwebelievetobethefirstonedescribedin theBrazilianliterature.

Case

report

Thepatientwasa68-year-oldwomanwithahistoryof arthro-plastyoftheleftkneeperformedin2002.Eightmonthsafter thefirstprocedure,shestartedtopresentaconditionoflocal pinand persistent effusion.After sixmonthsoffollow-up, withpersistentlypositiveinflammationtestsandindicative scintigraphy tests with technetium and gallium, but with threearthrocentesis samplesthatdidnotproducebacterial growthincultures,theprosthesiswasremovedandacement spacerwasinserted.ThegermStreptococcusviridianswas iso-latedand antibiotictherapywasinstituted,guidedbydeep tissuethathadbeencollectedduringthesurgicalprocedure.

InOctober2003,thearthroplastywasrevisedusingnails andwedges,cementcontainingantibioticanda posterosta-bilizedpolyethylenecomponent.Therewasnorecurrenceof infectionafterthisoperation.

In2012,thepatientsoughttheemergencyserviceofour hospital,withacomplaintofsuddenpainandinstabilityin thekneethathadbeenoperated,afterabruptphysicaleffort.

Fig.1–Radiographsinanteroposteriorandlateralviewsof

theleftknee,demonstratingtherevisionprosthesis

withoutsignsoflooseningordislocationofthetibial

polyethylene.

Fig.2–Transoperativeclinicalimageofrevisionofthe

arthroplastyoftheleftknee,demonstratingosteolysisin

themedialtibialmetaphysis.

Onexamination,coarseinstabilityofthekneewasobserved, withjointeffusionanddiffusepain.Althoughtheinitial diag-nostichypothesissuggestedthepossibilityofperiprosthetic fracturing,radiographsdemonstrateddisplacementofthe tib-ialpolyethylene(Fig.1).

Thepatientthereforeunderwentanewrevisionprocedure. During theoperation,anareaofosteolysisintheproximal medialtibialmetaphysiswasshown,inadditiontodislocation ofthepolyethylene(Fig.2).Nevertheless,thetibialnail pre-sentedadequate stability.Thus,thepolyethylenepiecewas

exchanged and a larger medial metal wedgewas inserted

(Figs.3and4).

Currently, one year after this operation, the patient presentsexcellentpostoperativeevolution:nopain,no effu-sion, completeextension, flexionof115◦_{, varus andvalgus} stabilityandadequatepatellartracking.

Fig.3–Transoperativeclinicalimage(finalresult)of

116

Fig.4–Radiographsinanteroposteriorandlateralviewsof

theleftknee,demonstratingpostoperativecontrolof

revisionofthearthroplasty,withexchangeofthe

polyethyleneandthemedialtibialmetalwedge.

Discussion

Thereal incidenceofdislocationofthe polyethylenepiece fromitstibialbaseisunknown.Onlyafewcaseshavebeen reportedintheliterature.Upto2007,onlyfourpapers pub-lishedinEnglishdescribed thisphenomenon.5 _Mostofthe

reportsrelatedtocasesofimplantsinwhichthecruciate lig-amentswerepreserved.

The causes have not been well determined. Technical

errorsininsertingthepolyethyleneduringthesurgery,such asincompleteseating,andalsooccurrencesoftrauma,may cause damage and failure of the locking system.4 _Forced

flexionmovementsstartingfromextension,whichgenerate greaterposteriorloadconcentration,maycontributetoward anterior loosening. Polyethylene dislocation may also be causedbytheimplantdesign,insituationsofashallowtibial baseoranexcessivelynarrowtrackforthepolyethylenepiece tobefittedinto.4–8

Inrelationtothetreatment, surgeryforsuspectedcases isrecommendedintheliterature.Therearereportsofgood resultsachievedbyexchangingonlythepolyethylenepiece. However,aninvitrotrialdemonstratedthattheforceneeded todisplacethepolyethylenebecameprogressivelylowerwith increasing numbers ofexchanges,which suggests that the lockingsystembecomesweakened.4 _{Therefore,during}

revi-sionsurgery,incasesinwhichthereismovementbetween the preexistingtibialbaseand thenewpolyethylenepiece, revisionofthetibialcomponentwillalsobeindicated.4,5,7,8

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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complicationsoftotalkneearthroplasty.JBoneJointSurgAm. 1997;79(2):278–311.

4.WrightRC,CrouchA,YacoubianSV,RavenRB3rd,Falkinstein Y,YacoubianSV.Nontraumaticspontaneousdislocationof polyethylenetibialinsertafter1yearafterTKA.Orthopedics. 2011;34(12):933–5.

5.AndersonJA,MacDessiSJ,DellaValleAG.Spontaneous recurrentdislodgmentofthepolyethyleneoftibialinsertafter totalkneearthroplasty.Acasereport.JBoneJointSurgAm. 2007;89(2):404–7.

6.ChenCE,JuhnRJ,KoJY.Dissociationofpolyethyleneinsert fromthetibialbaseplatefollowingrevisiontotalknee arthroplasty.JArthroplasty.2001;23(2):339.e11–3.

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