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Original
article
Two-level
lumbar
total
disc
replacement:
Functional
outcomes
and
segmental
motion
after
4
years
S.
Trincat
a,∗,b,
G.
Edgard-Rosa
c,
G.
Geneste
c,
T.
Marnay
caHôpitalprivé«lesFranciscaines»,3,rueJean-Bouin,30032Nîmes,France
b65,avenueJean-Jaurès,30900Nîmes,France
cCliniqueduParc,50,rueEmile-Combe,34170Castelnau-le-Lez,France
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Accepted17October2014
Keywords:
Totaldiscreplacement
Degenerativediscdisease
Low-backpain
a
b
s
t
r
a
c
t
Introduction:Lumbartotaldiscreplacementisaneffectivetreatmentforsingle-leveldiscogeniclower backpain.Butthereplacementoftwodisclevelsiscontroversial.
Hypothesis:Two-leveltotaldiscreplacementwillimprovefunctionwhilepreservingspinalmotion. Materialandmethods:Acontinuousseriesof108patients(51women,57men)surgicallytreatedover twolevelswiththeProDisc-Limplant(SynthesSpine)wasevaluatedretrospectivelywithanaverage follow-upof4years.Ninety-threeofthesepatientswereoperatedforL4/L5andL5/S1degenerativedisc disease,while15wereoperatedforL3/L4andL4/L5disease.Theprocedurewascarriedoutthrough theleftretroperitonealapproachin65patients,therightretroperitonealapproachin42patientsand bothapproachesin1patient.TheOswestryscore,lumbarVASandradicularVASwereusedtoevaluate function.ThemotionoftheprostheticdiscsegmentswasevaluatedusingCobb’smethod.Datawere collectedprospectivelyinthecontextofregularpatientmonitoring.Aretrospectiveanalysiswascarried outbyanindependentexaminer.
Results:Theprocedureledtoastatisticallysignificantimprovementinthefunctionalscores.Themotion oftheupperdiscsegmentwas9◦(0◦–19◦)inflexion/extensionand5.5◦(2◦–12◦)inlateralbending.It was6.2◦(0◦–14◦)and1.9◦(0◦–7◦)atthelowerdiscsegment.TherangeofmotionwassimilarinL3/L4 andL4/L5,butwaslessinL5/S1.Lackofmobilitywasnotcorrelatedwithalterationsinthefunctional outcome.Thecomplicationratewas18%.
Discussion:Two-levellumbardiscreplacementimprovesspinalfunctionwhilepreservingitsmobility. Butthisprocedureisfraughtwithrisksandmustbecarriedoutbyahighly-experiencedteam.Alonger follow-upisneededtoevaluatethesustainabilityoftheresultsandtodetectanyadjacentsegment disease.TheFrenchNationalAuthorityforHealth(HAS)hasrecommendedagainsttwo-levellumbardisc replacement,soitnolongercanbeperformedinFrance.
©2014ElsevierMassonSAS.Allrightsreserved.
1. Introduction
Single-level lumbar total disc replacement (TDR) has been shown to be non-inferior to spinal fusion. Its useis generally acceptedinveryspecificindications [1,2].Butdiscreplacement attwolevelsiscontroversialbecauseofconflictingresults[3–8]. Currently,atwo-levelprocedurecannotbeperformedinFrance becausetheHAS(FrenchNationalAuthorityforHealth)has recom-mendedagainstit.However,TDRhasbeenshowntobenon-inferior tospinalfusionforthetreatmentoftwo-leveldegenerativedisc disease(DDD),whileimprovingmobilityandfunctionalrecovery
∗ Correspondingauthor.Tel.:+0466295455;fax:+0466383172.
E-mailaddress:[email protected](S.Trincat).
intheshortterm[9].Thealternativeistouseahybridconstruct [10,11]thatcombinesfusionandarthroplasty,withpreservation ofsegmentalmotionbeingthetheoreticaladvantageofthelatter. Thegoalofthisstudywastoevaluatetheperioperative com-plicationsandfunctionaloutcomesinpatientswhohadundergone two-levellumbarTDRafteraminimumfollow-upof2years.The spinalsegmentmotionwasevaluatedatthelastfollow-upusing radiographs.
2. Materialandmethods
Thiswasacontinuousretrospectivestudyof150patients oper-atedfortwo-levellumbarTDRwhowereevaluatedatleast2years aftertheprocedure.Ofthese150patients,onlythoseoperatedat L3/L4andL4/L5orL4/L5andL5/S1wereincluded.Patientswere http://dx.doi.org/10.1016/j.otsr.2014.10.014
excludedfromtheanalysisiftheydidnothavecompleteandusable preoperativeandpostoperativeclinicalandradiologicalrecords.In theend,theanalysiswascarriedouton108patients(57men,51 women)havinganaverageageof46±10years(range19–73).The averagefollow-upwas49months(range25–63).
Thesurgicalindicationwasestablishedinpatientswith multi-levelsymptomaticDDDthatwasresistanttomedicaltreatmentor well-conductedrehabilitationandpresentedModic0,1or2signs onMRI[12,13],orfailingthat,apositivelumbardiscogram.
TheprocedurewascarriedoutatL4/L5andL5/S1in93cases and at L3/L4 and L4/L5 in 15 cases.It wasperformed through theleft retroperitoneal (anterolateral) approach in 65 patients, therightretroperitonealapproach [14]in 42patientsand both approaches in 1 patient. TheProDisc-L TotalDisc Replacement system(SynthesSpine,WestChester, PA, USA) wasusedin all patients. This is a semi-constrained implant consisting of two cobalt-chromealloy endplates with keels that are coated with porousplasma-sprayed titaniumand an UHMWPE core that is clipped tothe inferior endplate and articulates withthe supe-riorendplatethroughaconvexdome.Theaveragedurationofthe procedurewas111±31min(70–230)withanaveragebloodloss of316±453mL(50–3500).Thesurgicalscarwas10±2cm(5–18) longonaverage.
Data was collected prospectively in the context of regular patientfollow-up.TheOswestryDisability Index(ODI)and sev-eralEVAtests(lumbarpain,radicularpainandsatisfaction)were performedpreoperativelyandthenpostoperativelytoassess func-tionat3months,6months,1year,2yearsandthenevery2years. Radiographic assessment consisted of standard A/P and lateral weight-bearingviews,dynamicsimages(Fig.1)andstandingviews oftheentirespinalcolumn.Thesegmentalmotionwasevaluated usingCobb’smethod[15].
Thedatawereanalysedretrospectivelybyanobserverwhowas notaffiliatedwiththesurgeons,implant designersand implant manufacturer.StatisticalanalysiswasperformedwithStatview® softwaretocomparepreoperativeandpostoperativedatawith Stu-dent’st-test.DifferenceswereconsideredsignificantifP<0.05. 3. Results
ResultsofthesegmentalmotionanalysisaregiveninTable1. Overall,thetwolevelsremainedmobileinflexion/extensionand lateralbending;therangeofmotionwassignificantlygreaterin theuppersegment.Specificanalysisofthemotionofeachtypeof constructfoundnodifferencesbetweenthetwolevelsintheL3/L4 andL4/L5constructs,butsignificantlylowervaluesinthelower segmentoftheL4/L5and L5/S1constructs.MotionintheL4/L5 segmentwasunaffectedbythetypeofconstructused.
Table1
Intraprostheticmotion(degrees).
Flexion/extension Lateralbending Level1 9±5.7(0–19) 5.5±3.2(2–12) Level2 6.2±4.5(0–14) 1.9±2.4(0–7) P <0.05 <0.05 L3/L4 8±5.7(1–14) 6.9±3.2(3–10) L4/L5 8±7.0(1–14) 2.2±3.2(0–7) P n/s n/s L4/L5 7.3±8.2(1–19) 4.3±3.7(0–8) L5/S1 4.4±5.2(1–12) 0.75±0.95(0–2) P <0.05 <0.05 L4/L5(upperlevel) 8±7.0(1–14) 2.2±3.2(0–7) L4/L5(lowerlevel) 7.3±8.2(1–19) 4.3±3.7(0–8) P n/s n/s n/s:notsignificant.
Fig.1.A.DynamiclateralbendingX-raysforL4/L5;B.Dynamicflexion/extension X-rays.
Functionally,therewasasignificantimprovementintheODI, lumbarVASandradicularVAS;thesatisfactionVASwas7.9atthe lastfollow-up(Table2,Fig.2).
If a “mobile segment” is defined as one with more than 2◦ motion,thenthreetypesofprogressionwereobserved:constructs wheremotionwaspreservedonbothlevels(74%ofcases,including 87%ofL4/L5–L5/S1),constructswheremotionwaspreservedinthe uppersegment(21%ofcases)andconstructswithoutanymotion (7%ofcases).Nosignificantdifferenceswerefoundbetweenthese
Table2
Functionalresults.
Preoperative Lastfollow-up P ODI/50 25±9 12±10 −50% <0.05 LumbarVAS 7.1±2 2.8±2.4 −60% <0.05 RadicularVAS 5.4±3.1 2.6±3 −52% <0.05 SatisfactionVAS – 7.9 – –
Fig.2.A.ChangeinfunctionnalVASandpatientssatisfactionatlastfollow-up.B. ChangeintheODI.
Fig.3.ODI/100,comparisonofmultilevel(2–3)totaldiscreplacement.
threegroupsintermsofthefunctionaloutcomes(VAS-L,VAS-R andODI)atthelastfollow-up(P>0.05).
ThecomplicationsarelistedinTable3.Therewasan18% com-plicationrate(all causescombined)for theentire series,which occurredin15%ofpatients.Earlysurgicalrevisionwasrequired in2.8%ofpatients:oneforunclippingoftheUHMWPEinsertand twoforretroperitonealhematomasecondarytolettinggoofvein
Table3
Complications.
Implant-related Notimplant-related 1unclippingofpolyethylene
core
3iliacveinwounds
2leftcommoniliacveinwounds(2 L4/L5–L5/S1usingleftapproach)
1rightcommoniliacveinwound(1 L4/L5–L5/S1usingrightapproach) 2implantsubsidence(superior
endplateofmiddlevertebra)
4retroperitonealhematoma 1L5radiculardeficiency 1duramaterwound 2deepveinthrombosis 1wounddehiscence 5urinaryinfection
sutures or ligatures. No late revisionswere needed during the follow-upperiod.
4. Discussion
Thisstudyisthefirsttoevaluatethemotionofatwo-level lum-bardiscreplacementconstruct.Itconfirmsthatmotionispreserved inthetwosegmentsaftermorethan4yearsoffollow-upandthat functionaloutcomesaregood.Themajorstrengthofthisstudylies inthelargenumberofpatientsincluded.Theretrospectivenature ofthestudyandtheinabilitytoprocessalltheradiographicrecords reducesitsimpacthowever.
The theoretical amplitude of implant motionis 20◦ in flex-ion/extensionandbending[3].Thetruerangeofmotionobserved invivoislowerbecauseofthepresenceofmuscle,capsuleand lig-amentstructures.Itisalsolowerthanphysiologicalvalues[16,17], amountingto75%atL3/L4,50%atL4/L5and 33%atL5/S1[17]. Leivseth[18]reportedsimilarfindingsof66%ofthephysiological valuesatL3/L4,45%atL4/L5and27%atL5/S1[17,19].This phe-nomenoncanbeexplainedbythepersistenceofpain,apprehension onthepartofthepatientandpresenceoftissueretractions[18].
However,themotionvalueswerenearthoseobservedatone levelwiththesameimplant[3,15,18](Table4).Theaveragemotion oftheCharitéTMArtificialDisc(DePuySpine,Inc.,Raynham,MA,
USA)was7.5◦inflexion/extensionaftertwoyears[20].Themotion islessatL5/S1incomparisontoL3/L4andL4/L5[3,15,18],likely becauseofinterlocking.Atthispoint,nostudyhascomparedthe motionofhybridconstructsandtwo-leveldiscreplacement con-structs.
Although the outcomeswere positive and motion was pre-served, in some patientsthe replacement disc wascompletely frozenanddidnotmoveatoneorbothlevels.Thiscanbeexplained byvariousfactors[18].First,themobilityofanimplantisrelatedto thequalityofitspositioning,whichmustbeascloseaspossibleto thevertebra’sinstantaneouscenterofrotation.Non-optimal posi-tioningreducesimplantmotion,evenifitdoesnotnecessarilylead topoorfunctionaloutcomes[20].Itisalsopossiblethatexcessive discheighthasanegativeeffectofmobilitybecauseofthe result-ingdistraction.Thisphenomenoncanalsobeexplainedclinicallyby thepersistenceofpainandstiffness,asmentionedabove.Butthis stiffnessdoesnotseemtobecorrelatedtothefunctionaloutcome. Figs.3and4comparethefunctionalresultsreportedin stud-iesofmultileveldiscreplacement[3,4,6,8].Theimprovementwas
Table4
Comparisonofflexion/extensionmotionatL3/L4,L4/L5,L5/S1invariouspublishedstudies.
Mobility Thisstudy Physiological 1level 2levels Hybrid Hayes[16] Frobin[17] Huang[15] Leivseth[18] Tropiano[3]
L3/L4 8◦ 10◦(2◦–18◦) 14.2◦(±3.7) 7.5◦(3◦–12◦) 8.0◦(±5.5◦) – – –
L4/L5 8.8◦ 13◦(2◦–20◦) 16.4◦(±4.1) 6.2◦(2◦–18◦) 8.0◦(±3.9◦) 10◦(8◦–18◦) – –
Fig.4.VAS/10,comparisonofmultilevel(2–3)totaldiscreplacement.
comparablebothintermsoftheODI(Fig.3)andtheVAS(Fig.4), butthesmallnumberofpatientsinsomeofthesestudiestempers theinterpretationoftheseresults.Onlyonestudyprovidessimilar informationforhybridconstructs[10].Despitetheuseofdifferent constructs,theODIandlumbarVASweredecreasedby53%and65%, respectively,after2yearsoffollow-up,whichwascomparableto theresultsofthecurrentstudy(Fig.5).
Severalauthors have highlightedthe biomechanical risks of multilevel TDR. Huang [15] reported a 24% rate of junctional degenerationwithhypomobility.Italsoseemsthattheseimplants increasethepressureontheposteriorfacetjoints[4,21–23],which caneventuallyleadtosymptomaticlumbarfacetarthropathy. Mul-tilevelconstructscanalsobethesourceofcoronalplanedeformity [24].
Therateofearlycomplicationsrelatedtotheimplantorthe surgeryinthecurrentstudy(Table5)wassimilartootherseries reportingresultswithmultilevelimplants[4,6,8](Fig.6).
Surgically,themainintra-operativerisk revolvesaroundthe iliacandiliolumbarveins;damagingthemcancausepotentially life-threatening bleeding. This risk justifies having a vascular surgeonpresentinthewardoroperatingroom.Performing preop-erativeCTangiographycanhelptoidentifythebifurcationlevelor lookforanyanatomicalvariations.Thesevenouswoundsarealsoa postoperativeriskwiththepossibilityofretroperitonealhematoma secondarytoveinsuturedehiscenceordeepvenousthrombosis secondarytothecompressionappliedduringrepair.
Asforimplant-relatedcomplications,twocasesofsuperior end-platecompressionoccurredinpatientsabove60yearsofagewith osteoporoticbone forwhich the TDRindicationwasdebatable. OsteoporosisshouldbeacontraindicationandpreoperativeDEXA
Fig.5. Functionaloutcomes;comparisontohybridconstructs.A.ODI;B.Radicular
VAS;C.LumbarVAS.
Table5
Comparisonofcomplicationswithmultilevelimplants.
Currentstudy Siepe,Spine2007 Hannibal,Spine2007 Bertaglioni,Spine2005
Implant ProDisc ProDisc ProDisc ProDisc
Levels 93L4/L5+L5/S1 20L4/L5+L5/S1 29L4/L5+L5/S1 15@2levels 15L3/L4+L4/L5 3L3/L4+L4/L5 10@3levels
Complications 18% 30% 19% 16%
3iliacveinwounds 1hypogastricplexus 1leftEIVthrombosis 1implantsubsidence 4retroperitonealhematomas 1segmentalstenosis 2footdrops 1PEcoredislocation 1L5radiculardeficiency 1L2/L3L3/L4hernia 1femoralartery
thrombosis
1wounddehiscence 1duramaterwound 1wounddehiscence 1L3/L4hernia 1retrogradeejection 2deepveinthrombosis 1retroperitonealseroma 1L5vertebrafracture
1wounddehiscence 1posteriorfacetarthropathy 5urinaryinfections
1unclippingofPEcore 2implantsubsidences
Fig.6.Complicationrateformultilevelimplants.
scanshouldbeconsideredbeforethesurgicalprocedure.Vertebral fracturecantheoreticallyoccurinthemiddlevertebrabecauseof thekeels[3,25].Nofractureswereobservedinthecurrentstudy. Otherrarercomplicationswereobservedsuchasdislocationofthe polyethylenecore[8]andimplantmigration[7].
BecauseofcurrenthealthregulationsinFrance,two-leveltotal discreplacementcannolongerbeperformed.Asaconsequence,we areexploringthepossibilityofusinghybridconstructsinpatients withmultileveldegenerativediscdisease.
5. Conclusions
Two-leveltotallumbardiscreplacementresultedinsatisfactory functionaloutcomes,whilepreservingmotionintheoperated seg-mentinmostpatients.TherangeofmotionwassimilaratL3/L4and L4/L5,butwaslessatL5/S1.Theabsenceofmotioninoneoreven twolevelswasnotcorrelatedwithpoorerfunctionaloutcomes.
Butthisprocedureisnotdevoidofperioperativerisk,especially vascularones;itshouldbeperformedbyteamsthatarewell-versed inthesurgicaltechnique,potentiallyincollaborationwitha vascu-larsurgeon.
Aprospectiverandomisedstudyisneededtoproperlycompare multilevelTDRwithhybridconstructs.However,multilevel degen-erativediscdiseaseisacontraindicationtoarthroplastyinFrance becauseoftheHASrecommendations.
Amedium-termanalysisofthecurrentstudypopulationwillbe neededtore-evaluatethesegmentalmotionanddetectany adja-centsegmentdisease.Additionalevaluationofthesagittalbalance andsegmentallordosiscorrelatedwiththefunctionaloutcomes couldalsohelpusbetterdefinetheindicationsandidentifyrisk factorsforpoorfunctionaloutcomes.
Disclosureofinterest
TM:Clinicaltrials:principalinvestigator,studycoordinatorand primaryresearcherforProDisc-L(SynthesSpine,WestChester,PA, USA).
GG:Clinicaltrials:co-investigator,non-primaryresearcherfor ProDisc-L(SynthesSpine,WestChester,PA,USA).
S.TrincatandG.Edgard-Rosadeclarethattheyhavenoconflicts ofinterestconcerningthisarticle.
Acknowledgements
NathalieLarive,ClinicalResearchAssociate,CliniqueduParc, Castelnau-le-Lez,France.
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