脊柱侧弯的非融合治疗.pdf

ORIGINAL ARTICLETreatment of degenerative spondylolisthesis:potential impactof dynamic stabilization based on imaging analysisThomas W.Lawhorne III Federico P.Girardi Curtis A.Mina Iaonnis Pappou Frank P.Cammisa JrReceived:19 March 2008/Revised:19 February 2009/Accepted:5 March 2009/Published online28 March 2009?Springer-Verlag 2009AbstractIntraspinous and pedicle screw-based(PSB)dynamic instrumentation systems have been in use for adecade now.By direct or indirect decompression,thesedevices theoretically establish less painful segmentalmotion by diminishing pathologic motion and unloadingpainful disks.Ideally,dynamics should address instabilityin the early stages of degenerative spondylolisthesis beforeexcessive translation occurs.Evidence to date indicatesthat Grade II or larger slips requiring decompression shouldbe fused.In addition,multiple segment listhesis,severecoronal plane deformities,increasing age,and osteoporosishave all been listed as potential contraindications todynamic stabilization.We reviewed the exclusion andinclusion criteria found in various dynamic stabilizationstudies and investigational drug exemption(IDE)proto-cols.We summarize the reported limitations for bothpedicle-and intraspinous-based systems.We then con-ducted a retrospective chart and imaging review of 100consecutive cases undergoing fusion for degenerativespondylolisthesis.All patients in our cohort had beenindicated for and eventually underwent decompression oflumbar stenosis secondary to spondylolisthesis.We esti-mated how many patients in our population would havebeen candidates for dynamic stabilization with eitherinterspinous or pedicle-based systems.Using the criteriafor instability outlined in the literature,32 patients dem-onstrated translation requiring fusion surgery and 24patients had instability unsuitable for dynamic stabiliza-tion.Six patients had two-level slips and were excluded.Two patients had coronal imbalance too great for dynamicsystems.Twelve patients were over the age of 80 and 16demonstrated osteoporosis as diagnosed by bone scan.Finally,we found two of our patients to have vertebralcompression fractures adjacent to the site of instrumenta-tion,which is a strict exclusion criteria in all dynamictrials.Thirty-four patients had zero exclusion criteria forintraspinous devices and 23 patients had none for PSBdynamic stabilization.Therefore,we estimate that 34 and23%of degenerative spondylolisthesis patients indicatedfor surgery could have been treated with either intraspinousor pedicle-based dynamic devices,respectively.KeywordsDynamic stabilization?Degenerativespondylolisthesis?Dynamics?Spinal fusionIntroductionKirkaldy-Willis divided the spectrum of degenerativechanges in the lumbar spine into three distinct phases:(1)temporary dysfunction;(2)instability;and(3)re-stabi-lization.Stage 1 degeneration is likely to respond toconservative measures.In terms of accepted treatmentguidelines,treatment of early stage 2 disease has been agray area in which conservative measures have been thetreatment of choice,but have a diminishing effect.Latestage 2 cases are most likely to be treated with stabiliza-tion/fusion surgery.Finally,in stage 3 the role ofT.W.Lawhorne IIISpine Service,Rush University Medical Center,1653 W.Congress Parkway,Chicago,ILUSAF.P.Girardi?C.A.Mina(&)?I.Pappou?F.P.Cammisa JrSpine Service,Hospital for Special Surgery,535 E.70th Street,New York,NY,USAe-mail:minachss.eduT.W.Lawhorne III?F.P.Girardi?C.A.Mina?I.Pappou?F.P.Cammisa JrDepartment of Orthopedics,Weill Medical College of CornellUniversity,New York,NY,USA123Eur Spine J(2009)18:815822DOI 10.1007/s00586-009-0941-9decompression without fusion serves a role.Dynamic sta-bilization offers an opportunity for more aggressivetreatment of patients in the early stage 2 of Kirkaldy-Willisdegeneration 9.Some patients with degenerative spondylolisthesis canbe treated with decompression alone or with fusion.Acertain number of both groups do not do well.Therefore,weperceive degenerative spondylolisthesis(DS)patients asideal candidates for evaluating the applicability of dynamicstabilization.Degenerative spondylolisthesis is a segmentaldestabilization,which is the result of multifactorial degen-erative changes in the low lumbar spine.A number offactors have been associated with its development inclu-ding:disk degeneration,facet joint orientation,gender,ligament hyperlaxity,and physical overactivity 19.From a pathoanatomic perspective,DS evolves fromdegeneration of the disk.It eventually reduces its stiffnessand places greater stress on the facets.When subjected toshear forces,this may lead to subluxation.Because of theinherent stability of L5 and occasional presence of L5sacralization,the L4-5 and L3-4 levels are more frequentlyaffected.Progression of a slip results in facet hypertrophyand disk bulging,which in turn contribute to forward dis-placement of the thecal sac.Imaging studies demonstratediminished cross-sectional area of the cauda equina,facetdegeneration,and hypertrophy,and diffuse disk bucklingand degeneration.All of these factors contribute to thesymptoms of spinal stenosis and therefore are important incharacterizing the extent of the disease.Fusion the best answer?Until recently,surgical options in the treatment of degene-rative lumbar spondylolisthesis have been limited.Thetwo options available to the surgeon had been to either:(1)treat symptoms with conservative measures includingphysical therapy and injections;or(2)proceed with oper-ative decompression with or without fusion.In prior years,inconsistent fusion rates had been accompanied by unreli-able success.With the advent of fusion technologies suchas cages and segmental instrumentation,the rate of fusionin degenerative cases now approaches 95%.Unfortunately,the outcomes of fusion surgery have failed to improve at anequal rate.Even the most skilled surgeons achieve only a5070%good to excellent outcome with fusion surgery 2,25.Also,there is no correlation to attain fusion successand clinical outcome;meaning,not all pseudoarthroses arepainful nor are all successful fusions painless 23.Onecould argue that if instability alone were the cause of backpain,successful fusion should fix the problem every time.By fusing and stopping all motion(both normal andabnormal)one has not solved the problem.Poor resultsassociated with fusions have been associated with abnor-mal loading at the bonemetal interface after cageinsertion.Polikeit 17 demonstrated that cage insertionincreased the stress and markedly altered the load transferof the endplates.Similarly,McAfee 12 demonstrated thatclinical success of fusion was dependent upon solid boneformation around the cage,resulting in an increase in thearea of load transmission and decrease in the load over thefootprint of the cage.Sengupta 23 concluded from thisdata that improvements in back pain in surgery dependmore on the creation of a normal loading pattern than fromthe inhibition of motion.In addition,fusion carries with it the added risk ofadjacent segment disease in the long term.There have beennumerous studies examining the risk factors for and con-sequences ofthis post-fusion complication includingaccelerated degeneration of adjacent segments and flatback syndrome 16.Maintaining the protective effect ofsegmental motion can theoretically reduces the accelera-tion of adjacent segment degeneration 24.Dynamics:unloading,not unmovingDynamic stabilization has arisen as a means to alter loadtransmission across degenerated spinal segments whileavoiding the aforementioned problems with fusion.Usingvariable constructs,this technique has several theoreticaladvantages over fusion:(1)adjacent level protection 15,24;(2)protection of rotatory stress to the sacroiliac jointduring sitting 10;(3)maintenance of normal restingposture 6;(4)shorter OR time 24;(5)requirement offewer levels of treatment,because unlike fusion one canstop below adjacent segments with degeneration 24.Two classes of dynamic stabilizers,intraspinous-(IS)and pedicle screw-based(PSB)dynamic systems have beenin use for almost a decade now outside of North America.These devices theoretically establish less painful segmentalmotion by diminishing pathologic motion and unloadingpainful disks.Interspinous distraction devices(X-Stop,Wallis,DIAM,Coflex)function by inducing flexion inthe degenerative segment and result in less buckling of theligamentum flavum,offloading of the facets,and reduceIVD pressures 4.PSB dynamics systems(Graf ligament,Dynesys,Isobar,DSSS,M-brace,TFAS and TOPS)offloadspinal units in a fashion similar to pedicle-based posteriorinstrumentation 20.Because they do not depend on thepresence of posterior elements,pedicle-based systems canbe used with posterior decompression.Whereas randomized studies have shown that fusion isbeneficial in degenerative spondylolisthesis with spinalstenosis,it is debatable whether added instrumentation isbeneficial 11.Dynamic systems may combine advantages816Eur Spine J(2009)18815822123of both:providing more stability than decompressionalone,and being less invasive than instrumented fusion24.Materials and methodsOur study was performed in two parts.In Part 1,we sur-veyed the literature and current investigational drugexemption(IDE)studies to determine the indications forusing dynamic stabilization systems.In Part 2,we retro-spectively applied these criteria to a group of 100consecutive degenerative spondylolisthesis patients whohad undergone surgery in our practice.The objective wasto estimate the percentage of our DS patients who couldhave undergone dynamic stabilization with either inter-spinous or PSB systems.Part one:review of indicationsAfter reviewing the literature and IDE protocols,weassembled a list of criteria,which are considered in studiesusing both IS and PSB dynamic stabilization.Most of thelisted inclusion/exclusion criteria for dynamic stabilizersare true for any operative DS candidate:they have mode-rate to severe lumbar spinal stenosis with leg pain,theyhave failed conservative treatment(NSAIDS,PT,injec-tions),they have had no prior fusion surgery and have nosignificant comorbidities precluding them from surgery.However,there were several inclusion/exclusion criteria inthe dynamic studies that differentiated these patients fromother DS patients.They included:(1)instability on flexion/extension radiographs;(2)degree of spondylolisthesis slip;(3)age of patient;(4)degree of scoliosis;(5)degree ofosteoporosis;(6)presence of vertebral body fracture;and(7)the number of levels of slip present.These criteria wereuniformly mentioned in the literature and IDE studies ofdynamic devices,and it was with these criteria that wedetermined our estimation of potential utility of dynamicstabilization(Tables 1,2).Degree of slipDynamic stabilization systems are limited to cases withrelatively minor deformity 24.Ideally,dynamics shouldaddress instability in the early stages of degenerationbefore excessive translation occurs 9,20.Schwarzenbach20believesthatseveresegmentalinstabilityandadvanced disk disease increase the risk of failure indynamic devices.The dynamic device studies to date haveallowed only Grade I slip for interspinous and PSB systems(Table 1).Evidence to date indicates that Grade II or largerslips requiring decompression should be fused 1.Multiple-level slipsMultiple segment anterolisthesis has not been evaluated inmost dynamic studies addressing spondylolisthesis 14,21.Patients with multiple-level listhesis will therefore beexcluded as dynamic candidates.The Dynesys IDE didallow double-level DS slips;however,the large Dynesysstudy by Stoll et al.24 did not.Coronal deformityThe dynamic stabilizers are designed to stop progression ofonly minor deformity in the coronal plane 24.Dynesyshas been found to be useful in early stages of degenerative,Table 1 Summary of exclusion criteria for interspinous(IS)dynamic stabilizersExclusioncriteriaXstopWallisCoflexDIAMAverageinterspinousexclusionSourceThunderZuchermanESJSenegasSpine Health.orgKimSinghInstabilityinstabilityinstabilityNo DS2 mm onflex/ext4 mmunstable3 mmtranslationDegree of slipGrade IGrade INo DSN/AGrade IGrade IGrade IAgeN/A50youngerpreference1860No elderly(max=71)N/AAge80Scoliosis25?25?N/A25?severesignificant25?scoliosisQuality of boneSevere OPSevere OPOPSevere OPDexa-2.5OPOPAny OPFracture of bodyBody fxPath fxN/AN/AN/ABody fxAny body fxDouble spondyN/AYesN/AYesN/AN/ADouble OKOtherNo Modic 2 or 3no L5S1 lesionDS degenerative spondylolisthesis,OP osteoporosis,fx fractureEur Spine J(2009)18:815822817123gradual scoliosis,but as the deformity becomes morepronounced,failure is more likely 20.Currently,themaximum amount of degenerative scoliosis permitted inDynesys investigational trial is listed as 10?.The same istrue for the other PSB devices analyzed here.The inter-spinous device protocols have uniformly allowed up to 25?of coronal deformity and for this reason we will differ inour threshold for scoliosis between the IS and PSB groups(Table 3).InstabilityTranslation of greater than 3 mm or 510?of rotationalmovement on lateral flexion-extension radiographs isradiographic evidence of instability 1.In the past,thisdefinition of instability has been an absolute indication forfusion 5.Some interspinous dynamic devices even list2 mm as a contraindication to their use 4.However,mostof the interspinous IDEs exclude cases of more than 3 mmof translational movement as seen on flexion-extensionfilms including Coflex,XStop,and Wallis.The PSB sys-tems can tolerate more instability and they uniformly donot define a maximum translation as exclusion criteria 7.Age,osteoporosis,and fractureSengupta,a pioneer in dynamics,feels that dynamic sta-bilization is ideal for younger patients.In a younger patientwith longer follow-up and greater physical demands,thelikelihood of eventually developing adjacent disease withrigid fixation would be higher 21.In the older populationone may be more inclined to use dynamics in the patientwho might be at higher-risk for a more invasive fusionprocedure.However,there have been some limitationsdefined with dynamics in elderly patients with osteoporoticbone 20.Unlike a fusion implant,a dynamic implant-boneinterface will be actively tested on a daily basis for the lifeof the patient.Currently,most IS and PSB devices have setan upper limit of use around 7580 years of age for theirIDE(TOPS,Dynesys,Coflex,Wallis).All studies haveexclusion criteria that include a diagnosis of osteoporosisand or chronic insufficiency fractures of the vertebral bodies27.For the purpose of this study,we have defined an agegreater than 80,a diagnosis of osteoporosis,or a history ofinsufficiency fracture as reasons to exclude any type ofdynamic stabilization as a surgical option.Table 1 outlines the exclusion criteria for interspinousdynamic stabilizers while Table 2 outlines the exclusioncriteria for PSB dynamic stabilizers.Part two:radiographic evaluation of 100 degenerativespondylolisthesis patientsWe then rev