OPLL經典綜述講讀王雪鵬杭州市骨科研究所杭州市第一人民醫院骨科Ossificationoftheposteriorlongitudinalligament(OPLL)resultsfrompathologicreplacementofthePLLwithlamellarbone,potentiallycausingspinalcordcompressionandneurologicdeteriorationOPLLwasfirstdescribedinJapanesepatientsandhasclassicallybeenconsideredacauseofmyelopathyinpatientsofEastAsianoriginspondylosismyelopathyradiculopathystenosisdischerniationAmongpatientsinJapanwithcervicalspinedisorders,theincidencehasbeenestimatedat1.9%to4.3%and,inotherAsiancountries,upto3.0%OPLLhasbeenrecognizedasanetiologyofmyelopathyregardlessofethnicity,withanestimatedincidencerateof0.1%to1.7%amongNorthAmericansandEuropeansPathoanatomyThePLLrunsalongthedorsalsurfaceoftheC1anteriorarchandcervicalvertebralbodiesandconsistsoflongitudinalfibersconfluentwiththetectorialmembranecraniallyandendingatthesacrumcaudallyfunctionally,thePLLresistsspinehyperflexionPathophysiologyThepathologicprocessleadingtoOPLLbeginswithchondroblast-andfibroblast-likespindlecellproliferation,alongwithvascularinfiltrationleadingtoPLLdegenerationandhypertrophy.Endochondralossificationfollows,resultinginitsreplacementwithmaturelamellarboneGenetics,localtissuecharacteristics,andassociatedmedicalcomorbiditieshaveallbeenimplicatedinthisfinalcommonpathwayMedicalcomorbiditiesarealsoassociatedwiththedevelopmentofOPLLUpto50%ofCaucasianpatientswithOPLLalsohavediffuseidiopathicskeletalhyperostosisHypoparathyroidism,hypophosphatemicrickets,hyperinsulinemia,andobesityhavebeenidentifiedasriskfactorsNaturalHistoryPatientswithOPLLcommonlypresentintheirfifthandsixthdecades,withmenaffectedtwiceasoftenaswomen.Mostpatientshavesomeneurologicsymptomsatdiagnosis,with28%to39%fulfillingdiagnosticcriteriaformyelopathyInpatientswithmyelopathy,64%haddeteriorated,however,and89%ofpatientswithNurickgrade3or4myelopathywhorefusedsurgeryhadprogressedtoawheelchair-orbed-boundstateRiskfactorsforthedevelopmentofmyelopathyinclude＞60%spinalcanalstenosis,＜6mmofspaceavailableforthecord,increasedcervicalrangeofmotion,andOPLLthatislaterallydeviatedwithinthespinalcanalAge,gender,andthenumberoflevelsaffectedbyOPLLdonotaffecttheprognosisClinicalPresentationChangesingaitorbalance,lossoffinemotorcontrol,andupperextremityweakness,numbness,orparesthesiasaresuggestiveofmyelopathyEarlymuscularfatigueorworseningsymptomsattheextremesofcervicalmotionarealsoconcerningPatientswithOPLLareatanincreasedriskofacutespinalcordinjurywithtrauma,andrapidneurologicdeteriorationinassociationassociationwithevenaminortraumaorwhiplashinjuryshouldraiseconcernforthedevelopmentofcentralcordsyndromePhysicalExaminationRadiologicEvaluationThelateralradiographisalsousedtodeterminetherelationshipoftheOPLLtothekyphosisline(K-line),whichisdrawnfromthecenterofthecanalatC2tothecenterofthecanalatC7AlargeOPLLmassorlossofcervicallordosiscausestheOPLLtoprotrudeposteriortotheK-line(referredtoasK-linenegative).ThisisanegativeprognosticfactorforposteriorsurgeryaloneCTwithsagittalandcoronalreformattinghasemergedasthebenchmarkforradiographicevaluationofOPLLandisnecessarytoreliablycharacterizeitGreaterthan60%canaloccupancyatanylevelandalaterallydeviatedmassareassociatedwithhighratesofmyelopathyThis“doublelayersign”onaxialorsagittalCTimagesisassociatedwithduraltearrates＞50%withanteriordecompressionversus13%whenthesignisabsentNonsurgicalManagementProphylacticsurgeryisneithernecessarynorrecommendedManagementincludestemporaryimmobilizationwithaneckbrace,steroidalornonsteroidalanti-inflammatorymedications,activitymodification,andphysicaltherapypatientsshouldbeadvisedtoavoidactivitiesthatmayresultinsuddenorexcessivecervicalspinemotionbecauseOPLLisassociatedwithahighrateofacutespinalcordinjury,eveninpatientswhodonotmeetsurgicalcriteriaSurgicalTreatmentSurgicaldecompressionisthetreatmentofchoiceforpatientswithNurickgrade3or4myelopathyorsevereradiculopathycausedbyOPLLviaeitherananteriororposteriorapproachAnteriorDecompressionandFusionProponentsarguethatitallowsforasuperiordecompressionandismoreeffectiveatmaintainingorrestoringcervicallordosisthanisposteriorsurgery.Associatedanteriorpathology,suchasdiskherniations,canalsobeaddressedDisadvantagesincludetechnicaldifficulty,inabilitytodecompresscranialtoC2,andhighratesofpseudarthrosisanddysphagiawhenthreeormorelevelsrequiretreatmentDuraltearsarealsomuchmorecommonwithananteriorapproach,giventhatanteriorduralossificationoccursin13%to15%ExposureisprovidedbythestandardSmith-Robinsonapproach,anddiskectomy,hemicorpectomy,orsubtotalcorpectomysufficienttoallowexposureoftheunderlyingOPLLmassisperformedCorpectomiesofuptofivelevelshavebeenperformedwithsuccess,butremovalofthreeormorecontiguouslevelsisassociatedwithincreasedcomplicationandreoperationratesComplicationsoccuraspartoftheapproach(eg,dysphagia,dysphonia),thedecompression(eg,C5palsy,duraltears),orthefusion(eg,graftsubsidence,pseudarthrosis)Nerverootpalsiesoccurin4%to17%ofpatientsthrougheitherdirecttraumaortraction.Patientspresentwithweakness,numbness,pain,orparesthesias,mostcommonlyintheC5distributionDuraltearsoccurin4%to20%ofpatients,oftenbecauseofduralossificationorattenuation.Cerebrospinalfluidleakagemayresultinpseudomeningoceleorfistulaformation,leadingtoneuraldamage,airwaycompression,meningitis,orwoundcomplicationsTearsrecognizedintraoperativelyaretreatedbydirectrepairorbyapplicationofautogenousfascialorsyntheticcollagengrafts.Closureofpinholedefectsoraugmentationofrepairsisdonewiththrombogenicsealants,suchasfibringlueorgelatinfoam.Postoperatively,divertinglumbardrainsandbedrestcanbeusedInanefforttoreduceduraltearrates,Yamauraetalintroducedthe“anteriorfloatingmethod”forcervicaldecompression,consistingofsubtotalvertebralbodyresectionandthinning,butnotremoval,oftheOPLL.Theposteriorvertebralbodyisnotreconstructed,allowingtheOPLLto“float”anteriorlyandawayfromthespinalcanal.At5-yearfollow-up,theauthorsachievedameanrecoveryrateof68.5%andimprovementinJapaneseOrthopaedicAssociationscoresfrom8.3to14.2.Noleaksofcerebrospinalfluidoccurred,but14%ofpatientswereleftwithaninadequatedecompression.Inthesepatients,orwithOPLLprogression,theauthorsrecommendedsubsequentposteriordecompression.Whenaddressingmorethantwoorthreelevels,fibularstrutgraftsarepreferredfortheirstructuralsupport.Foroneortwolevels,structuralgraftsoftricorticaliliaccrest,fibula,andvertebralbodieshaveallbeendescribed.Morerecently,interbodycageswithnonstructuralbonegraftorbonegraftsubstituteshavebeenused.Overallratesofpseudarthrosisvaryfrom3%to15%,withthehighestratesoccurringinpatientsundergoingfusionofthreeormorelevels.PosteriorDecompressionWhenmorethantwoorthreecervicallevelsareaffectedbyOPLL,posteriorsurgery(ie,laminoplasty,orlaminectomyandfusion)ispreferredbecauseofthetechnicaleaseandlowerrateofcomplications.Disadvantagesincludetheriskofpostoperativediseaseprogression,inabilitytocorrectcervicalkyphosis,andpoorresultsinK-linenegativepatients.Laminoplastyaccomplishesthisbyhingingopenthelaminaewitheitheran“opendoor”or“Frenchdoor”technique,resultingina30%to40%increaseinthesizeofthespinalcanalLaminectomyandfusionentailsremovalofthelaminaefollowedbyinstrumentedposterolateralfusion,resultingina70%to80%increaseincanalvolumeAfullanalysisoftheadvantagesanddisadvantagesbetweenlaminoplastycomparedwithlaminectomyandfusionhasbeendiscussedelsewhereOurpreferenceistouselaminectomyandfusionforOPLLbecausetheretainedcervicalmotionwithlaminoplastymayallowdiseaseprogression,andtheriskforprogressiontokyphosisattheaffectedlevelsiseliminatedwithfusionForseveredisease,recoveryratesafterposteriordecompressionappeartobelowerthanthosefollowinganteriordecompression,butwithalowercomplicationrateIwasakietalretrospectivelycomparedtheresultsofanteriordecompressionandfusionwiththoseoflaminoplasty;theyreportedbetteroutcomesafteranteriorsurgeryinpatientswithanOPLLmassoccupying＞60%ofthecanal;however,itresultsinareoperationrateof26%versus2%inthelaminoplastygroup.With＜60%canaloccupancy,recoveryrateswereequivalent.Aprospectivecomparisonofanteriordecompressionandfusionversuslaminoplastyfoundsimilarresults.Patientswith＞50%canaloccupancyhadsuperiorrecoveryrateswithanteriorsurgerybutequivalentrateswith＜50%involvementPatientswith＜5°ofcervicallordosisalsohadsignificantlyworseoutcomesfromlaminoplasty,and50%lostlordosisversusnoneinthefusiongroup.HalfofthelaminoplastypatientsexperiencedOPLLprogressionversusonlyoneafteranteriorsurgeryHowever,surgicalcomplicationsheavilyfavoredlaminoplasty,witha23%complicationrateanda14%reoperationrateintheanteriorgroupandnoneinthelaminoplastypatientsOnlyonestudytodatehasexaminedtheresultsoflaminectomyandfusionforOPLL.Chenetalreportedameanrecoveryrateof62%at5yearsamong83patientswhounderwentinstrumentedlaminectomyandfusionfromC2orC3toC7.Patientswithagoodoutcomehadsignificantlymorepostoperativelordosis(16.1°versus10.4°).Nootherfactors,includingoccupyingratio,weresignificantbetweengroups.Thereoperationratewas4%,alltheresultofepiduralhematomaformation.Whetherposteriorfusionhadaneffectondiseaseprogressionwasnotevaluated,althoughtheauthorsnotednolongtermdeclinei