The Evolution of Minimally The Evolution of Minimally Invasive Spine SurgeryInvasive Spine Surgery

and applications in Complex Spine and applications in Complex Spine

SurgerySurgery

Daniel Hutton, D.O.Daniel Hutton, D.O.

Disclosures Disclosures –– None None

Minimally Invasive Minimally Invasive SurgerySurgery

Developed from dissatisfaction of excessive Developed from dissatisfaction of excessive exposure, postoperative pain or scarring.exposure, postoperative pain or scarring.

Has led to shorter length of hospitalization, Has led to shorter length of hospitalization, less blood loss, and greater patient less blood loss, and greater patient satisfactionsatisfaction

Minimally invasive principles shared with Minimally invasive principles shared with many other specialtiesmany other specialties–– Laparoscope/RoboticsLaparoscope/Robotics

–– Natural orifice translumenal endoscopic surgery Natural orifice translumenal endoscopic surgery (NOTES)(NOTES)

Minimally Invasive Spine Minimally Invasive Spine SurgerySurgery

Collaboration with IndustryCollaboration with Industry

Risk vs. RewardRisk vs. Reward

Clear delineation of surgical goals:Clear delineation of surgical goals:

–– Neural decompressionNeural decompression

–– Postoperative Pain Postoperative Pain

–– Complications Complications

–– Blood LossBlood Loss

–– Intraoperative timeIntraoperative time

–– Length of Hospital stayLength of Hospital stay

Is Minimally Invasive Spine Is Minimally Invasive Spine Surgery worth the hype?Surgery worth the hype?

Touted features:Touted features:–– Less muscle damageLess muscle damage–– Less postoperative painLess postoperative pain–– Shorter hospital stayShorter hospital stay–– “Focused” exposure“Focused” exposure

Necessary to examine the type of surgery Necessary to examine the type of surgery being performedbeing performed–– Diverse surgeries with different objectivesDiverse surgeries with different objectives–– For example, unilateral lumbar microdiscectomy For example, unilateral lumbar microdiscectomy

vs. lumbar fusion vs. scoliosis correctionvs. lumbar fusion vs. scoliosis correction

Lumbar MicrodiscectomyLumbar Microdiscectomy

First reported in 1934 by Mixter and First reported in 1934 by Mixter and BarrBarr

More understanding of local More understanding of local anatomy/comfort with operationanatomy/comfort with operation

1997, Foley & Smith described 1997, Foley & Smith described microdiscectomy utilizing tubular microdiscectomy utilizing tubular retractorsretractors

Mixter WJ, Barr JS. Rupture of the intervertebral disc with involvement of the spinal canal. NEngl JMed.

1934;211:210-215.

Foley KT, Smith MM. Microendoscopic discectomy.Tech Neurosurg. 1997;3:301-307.

MicrodiscectomyMicrodiscectomyOpen vs. MISOpen vs. MIS

Arts, et al.Arts, et al.–– 328 patients (161 MIS, 167 open)328 patients (161 MIS, 167 open)–– Functional outcomes at 8 wks and 1 year:Functional outcomes at 8 wks and 1 year:

Primary Outcome: RolandPrimary Outcome: Roland--Morris Disability Questionnaire Morris Disability Questionnaire (RDQ) for sciatica(RDQ) for sciatica

Secondary Outcome: Secondary Outcome: –– 100100--mm visual analog scale for leg pain and back painmm visual analog scale for leg pain and back pain–– Patient’s selfPatient’s self--report of recovery measured on the 7report of recovery measured on the 7--point Likert point Likert

scalescale–– Functional and economic scores on the Prolo scaleFunctional and economic scores on the Prolo scale–– Bodily pain and physical functioning scores on the ShortForm36Bodily pain and physical functioning scores on the ShortForm36–– Bothersomeness Index scoresBothersomeness Index scores–– Complication and reoperation ratesComplication and reoperation rates

Patrick DL, Deyo RA, Atlas SJ, Singer DE, Chapin A, Keller RB. Assessing health-related quality of life in patients with sciatica. Spine. 1995;20(17):1899-1908.

Collins SL, Moore RA, McQuay HJ. The visual analogue pain intensity scale: what is moderate pain in millimetres? Pain. 1997;72(1-2):95-97.

Bombardier C. Outcome assessments in the evaluation of treatment of spinal disorders: summary and general recommendations. Spine. 2000;25(24): 3100-

3103.

Prolo DJ, Oklund SA, Butcher M. Toward uniformity in evaluating results of lumbar spine operations: a paradigm applied to posterior lumbar interbody fusions.

Spine. 1986;11(6):601-606.

Brazier JE, Harper R, Jones NM, et al. Validating the SF-36 health survey questionnaire: new outcome measure for primary care. BMJ. 1992;305(6846): 160-

164.

Used with permission from the Journal of the American Medical Association

Used with permission from the Journal of the American Medical Association

MicrodiscectomyMicrodiscectomyOpen vs. MISOpen vs. MIS

Arts, et al.Arts, et al.

–– Conclusions:Conclusions:

Tubular microdiscectomies were associated Tubular microdiscectomies were associated

with with statistically significantlystatistically significantly more leg and more leg and

back pain as compared to open.back pain as compared to open.

–– Leg/Back VAS pain p<0.05Leg/Back VAS pain p<0.05

No differences in size of incisionsNo differences in size of incisions

Patients less satisfied with MIS Patients less satisfied with MIS

May still be appropriate for morbidly obese.May still be appropriate for morbidly obese.

Postoperative Leg and Back PainPostoperative Leg and Back Pain

Does less tissue damage mean less pain?Does less tissue damage mean less pain?–– Muramatsu, et al. evaluated for postoperative Muramatsu, et al. evaluated for postoperative

enhancement as a sign of scar formation and found enhancement as a sign of scar formation and found no difference in open versus MIS.no difference in open versus MIS.

–– Arts, et al. evaluated the MRI T2 signal intensity of Arts, et al. evaluated the MRI T2 signal intensity of the multifidus muscle and measured serial CPK of the multifidus muscle and measured serial CPK of compared open vs. MIS at 1 year. compared open vs. MIS at 1 year. No advantage to MIS on VAS, CPKNo advantage to MIS on VAS, CPK MRI T2 intensity of MIS discectomy was significantly MRI T2 intensity of MIS discectomy was significantly

lower (p=0.04).lower (p=0.04).

We don’t have a clear corollary for postoperative We don’t have a clear corollary for postoperative back pain.back pain.

Muramatsu K, Hachiya Y, Morita C. Postoperative magnetic resonance imaging of lumbar disc herniation: comparison of

microendoscopic discectomy and Love’s method. Spine. 2001;26(14):1599-1605.

Arts M, Brand R, van der Kallen B, Nijeholt GL, Peul W. Does minimally invasive lumbar disc surgery result in less muscle

injury than conventional surgery? A randomized controlled trial. Eur Spine J. Epub Jun 16, 2010.

What About What About Complications?Complications?

Metaanalysis of MIS lumbar decompression and Metaanalysis of MIS lumbar decompression and MIS lumbar fusionsMIS lumbar fusions–– No difference in rate or magnitude of complicationsNo difference in rate or magnitude of complications

O’Toole, et al. reported an impressively low rate O’Toole, et al. reported an impressively low rate of infection after MIS spine surgeryof infection after MIS spine surgery

0.22% (3/1338), thought to be due to less tissue 0.22% (3/1338), thought to be due to less tissue damage/devascularization.damage/devascularization.

Fourney DR, Dettori JR, Norvell DC, Dekutoski MB. Does Minimal Access Tubular Spine Surgery Increase or Decrease

Complications in Spinal Decompression or Fusion? Spine 2010, 35;9S:S57-S65.

O’Toole JE, Eichholz KM, Fessler RG. Surgical site infection rates after minimally invasive spinal surgery. J Neurosurg Spine 11:471-

476, 2009.

What about more What about more complex scenarios?complex scenarios?

MIS Lumbar FusionsMIS Lumbar Fusions

Prospectively studied 59 patients, open vs. MIS PLIFProspectively studied 59 patients, open vs. MIS PLIF Evaluated T2 intensity on PreEvaluated T2 intensity on Pre-- and Postand Post--Op MRI, CK, VAS Back/LegOp MRI, CK, VAS Back/Leg Patients allowed to choose approachPatients allowed to choose approach MIS with less T2 damage on MRIMIS with less T2 damage on MRI MIS had a statistically significant improvement in VAS at one year MIS had a statistically significant improvement in VAS at one year

–– 10.7 vs. 21.2 10.7 vs. 21.2 –– P<0.001P<0.001

Fan S, Hu Z, Zhao F, Zhao X, Huang Y, Fang X. Multifidus muscle changes and clinical effects of one-level posterior lumbar

interbody fusion: minimally invasive procedure versus conventional open approach. Eur Spine J, 2010;19:316-324.

MIS Lumbar FusionsMIS Lumbar Fusions

Wang, et al. compared 1 or 2 level open vs. MIS lumbar fusionsWang, et al. compared 1 or 2 level open vs. MIS lumbar fusions–– Unilateral symptoms received MIS, Bilateral with openUnilateral symptoms received MIS, Bilateral with open–– MIS offered improved MIS offered improved

EBL p<0.065EBL p<0.065 LOS p=0.017 (single level), 0.259 (2LOS p=0.017 (single level), 0.259 (2--level)level) Hospital charges p=0.027 (single level), 0.071 (2Hospital charges p=0.027 (single level), 0.071 (2--level)level) Lesser need for discharge to rehab with MISLesser need for discharge to rehab with MIS

Similar results from Ntoukas and MullerSimilar results from Ntoukas and Muller–– Statistically significant improvements in EBL, hospitalization, and VAS (p<0.001)Statistically significant improvements in EBL, hospitalization, and VAS (p<0.001)–– Also statistically significant more radiation exposure, and surgical time (p<0.001)Also statistically significant more radiation exposure, and surgical time (p<0.001)

Wang MY, Cummock MD, Yu Y, Trivedi RA. An analysis of the differences in the acute hospitalization charges following

minimally invasive versus open posterior lumbar interbody fusion. J Neurosurg Spine 12:694-699, 2010.

Ntoukas V, Muller A. Minimally invasive approach versus traditional open approach for one level posterior lumbar interbody

fusion. Minim Invas Neurosurg 2010;53:21-24.

Thoracic Spine SurgeryThoracic Spine Surgery

1958, Thoracic discectomy 1958, Thoracic discectomy performed via transthoracic performed via transthoracic approach.approach.

Benefits include:Benefits include:–– Direct visualization of Direct visualization of

offending pathologyoffending pathology–– No need for No need for

retraction/manipulation of retraction/manipulation of neural elementsneural elements

Downfalls:Downfalls:–– Large incisionLarge incision–– Need for chest tubeNeed for chest tube–– Thoracic neuralgia/postThoracic neuralgia/post--

thoracotomy pain syndromethoracotomy pain syndrome May be as high as 50%May be as high as 50%

Crafoord C, Hiertonn T, Lindblom K, et al. Spinal cord compression caused by a protruded thoracic disc. Report of a case treated with

antero-lateral fenestration of the disc. Acta Orthop Scand 1958;28:103–7.

Pluijms WA, Steegers MAH, Verhagen AFTM, et al. Chronic post-thoracotomy pain: a retrospective study. Acta Anaesthesiol Scand

2006;50:804-8.

Thoracic DiscectomyThoracic Discectomy

Dissatisfaction with thoracotomy led to innovation of other Dissatisfaction with thoracotomy led to innovation of other approaches:approaches:–– Transpedicular discectomyTranspedicular discectomy–– Costotransversectomy/LECACostotransversectomy/LECA–– Thoracoscopic DiscectomyThoracoscopic Discectomy

Multiple portalsMultiple portals Better threeBetter three--dimensional understandingdimensional understanding DualDual--Lumen intubation Lumen intubation Steep learning curve, McAfee, et al.Steep learning curve, McAfee, et al. “Learn to operate with chopsticks” “Learn to operate with chopsticks”

–– MinithoracotomyMinithoracotomy “Minimally“Minimally--Invasive” (pathologyInvasive” (pathology--guided dissection)guided dissection) Option for transpleural or retropleuralOption for transpleural or retropleural May obviate the need for chest tubeMay obviate the need for chest tube Dramatically decreased risk of intercostal neuralgiaDramatically decreased risk of intercostal neuralgia Option for corpectomy and expandable cage from same approach, Keshavarzi, Option for corpectomy and expandable cage from same approach, Keshavarzi,

et al.et al.

Currier BL, Eismont FJ, Green BA. Transthoracic disc excision and fusion for herniated thoracic discs. Spine 1994;19:323–8.

McAfee PC, Regan JR, Zdeblick T, et al. The incidence of complications in endoscopic anterior thoracolumbar spinal reconstructive surgery.

A prospective multicenter study comprising the first 100 consecutive cases. Spine 1995;20:1624–32.

Keshavarzi S, Park MS, Aryan HE, Newman CB, Gonda D, Taylor WR. Minimally Invasive Thoracic Corpectomy and Anterior Fusion in a

Patient with Metastatic Disease: Case Report and Review of the Literature. Minim Invas Neurosurg 2009; 52:141-143.

Thoracic DiscectomyThoracic Discectomy

Bartels et al., 2007Bartels et al., 2007–– Compared Thoracoscopic vs. MiniCompared Thoracoscopic vs. Mini--Thoracotomy for excision of Thoracotomy for excision of

centrallycentrally--located thoracic disc hernationslocated thoracic disc hernations–– MiniMini--thoracotomy had:thoracotomy had:

Shorter duration of surgeryShorter duration of surgery Less blood lossLess blood loss Shorter duration of ICU stayShorter duration of ICU stay Shorter duration of chest tubeShorter duration of chest tube

–– Less steep learning curve with miniLess steep learning curve with mini--thoracotomy than with thoracotomy than with thoracoscopic.thoracoscopic.

Bartels HMA, Peul WC. Mini-Thoracotomy or Thoracoscopic Treatment for Medially Located Thoracic Herniated Disc? Spine 2007,

32;20:E581-E584.

Mayer HM. Microsurgical anterior approach to T5–T10 (Mini-TTA). In: Mayer HM, ed. Minimally Invasive Spine Surgery, 2nd ed.

Berlin: Springer; 2006:129–37.

Huang TJ, Hsu RWW, Li YY, et al. Minimal Access Spinal Surgery (MASS) in treating thoracic spine metastasis. Spine

2006;31:1860–3.

Spinal DeformitySpinal Deformity

“Life is a Kyphosing Event”“Life is a Kyphosing Event”Dave Dave

PollyPolly

PresentationPresentation

Patients with adult degenerative scoliosis Patients with adult degenerative scoliosis present with back pain and disability in 85% present with back pain and disability in 85% casescases

Pain may be from Pain may be from –– Degenerative disc disease and nerve root Degenerative disc disease and nerve root

compression/irritation, especially on the concave compression/irritation, especially on the concave sideside

–– Facet arthropathyFacet arthropathy–– Central canal stenosis and neurogenic Central canal stenosis and neurogenic

claudicationclaudication–– Sagittal malalignment and curve progressionSagittal malalignment and curve progression

PresentationPresentation

Contributing & Associated Contributing & Associated FactorsFactors

––Degenerative Disc DiseaseDegenerative Disc Disease

––OsteoporosisOsteoporosis

––Segmental instabilitySegmental instability

–– Iatrogenic (spinal Iatrogenic (spinal surgery/fusion)surgery/fusion)

PresentationPresentation

Sagittal BalanceSagittal Balance C7 Plum LineC7 Plum Line

–– Visibly balanced; a Visibly balanced; a vertical line from the vertical line from the midpoint of the C7 midpoint of the C7 body to the posterior body to the posterior superior corner of the superior corner of the sacrum sacrum

C

7

Sagittal Cobb AngleSagittal Cobb Angle

Cobb AngleCobb Angle

––Thoracic KyphosisThoracic Kyphosis

T5T5--T12T12

2020--40 degrees > 40 degrees > thoracic kyphosisthoracic kyphosis

––LumbarLumbar

T12T12--S1S1

40 degrees40 degrees––Lordosis Lordosis

Treatment OptionsTreatment Options

Conservative: Medication, Physical Conservative: Medication, Physical Therapy and Physical Medicine, BracingTherapy and Physical Medicine, Bracing

Not as effective as in other back pain Not as effective as in other back pain conditionsconditions

No Substantial Evidence for any No Substantial Evidence for any nonsurgical treatment in adult scoliosisnonsurgical treatment in adult scoliosis

Everett et al: A systemic Literature Review of Nonsurgical Treament in Adult Everett et al: A systemic Literature Review of Nonsurgical Treament in Adult Scoliosis. Spine 2007, 32:S120Scoliosis. Spine 2007, 32:S120--S134S134

Surgical ConsiderationsSurgical Considerations IndicationsIndications

–– Persistent pain despite conservative treatmentPersistent pain despite conservative treatment

–– Progression of deformityProgression of deformity

–– Progressive neurologic deficit Progressive neurologic deficit

Risks Risks –– Morbidity higher than adolescent scoliosisMorbidity higher than adolescent scoliosis

–– Secondary to stiff curves and need for complex Secondary to stiff curves and need for complex reconstruction (osteotomies)reconstruction (osteotomies)

–– Medical including cardiopulmonaryMedical including cardiopulmonary

–– Bone qualityBone quality

Surgical OptionsSurgical Options

Decompression aloneDecompression alone

Decompression and Posterior Decompression and Posterior Instrumented FusionInstrumented Fusion

Decompression and Anterior/Posterior Decompression and Anterior/Posterior FusionFusion

––Can have favorable results with all Can have favorable results with all approaches depends on goals and patient approaches depends on goals and patient expectationsexpectations

CONTROVERSYCONTROVERSYRole of Role of

decompression decompression alone or limited alone or limited fusionfusion

Role of combined Role of combined anterior and anterior and posteriorposterior

Choice of fusion Choice of fusion level (how high & level (how high & how low)how low)

Surgical Principals Surgical Principals

“The goals of surgery on the adult “The goals of surgery on the adult deformity patient are to treat pain deformity patient are to treat pain and relieve neurological problems and relieve neurological problems while maintaining or achieving threewhile maintaining or achieving three--dimensional balance. The absolute dimensional balance. The absolute degree of coronal curve correction in degree of coronal curve correction in an adult deformity patient is less an adult deformity patient is less important than maintaining good important than maintaining good sagittal balance.”sagittal balance.”

Heary, Neurosurgery Supplement. 2008;63(3):69Heary, Neurosurgery Supplement. 2008;63(3):69--76 76

Anterior vs Posterior vs Anterior vs Posterior vs BothBothAnteriorAnterior

––Severe Coronal Deformity >60’Severe Coronal Deformity >60’

PosteriorPosterior

––Osteotomies with segmental posterior Osteotomies with segmental posterior instrumentation (anterior column can be instrumentation (anterior column can be addressed TLIF)addressed TLIF)

36036000 FusionFusion

––Old ways with high morbidityOld ways with high morbidity

––New modalities show very good promise New modalities show very good promise

Far Lateral Far Lateral

Endoscopic anterior releaseEndoscopic anterior release

MinimallyMinimally--Invasive Deformity Invasive Deformity SurgerySurgery

Wang & Mummaneni, 2010.Wang & Mummaneni, 2010.–– 23 patients with degenerative scoliosis, combined direct lateral 23 patients with degenerative scoliosis, combined direct lateral

release/interbody fusion, posterior percutaneous instrumentationrelease/interbody fusion, posterior percutaneous instrumentation Preop Cobb 31.4Preop Cobb 31.400

Mean number of levels 3.7 correctedMean number of levels 3.7 corrected

–– Correction of deformity: Cobb 11.5Correction of deformity: Cobb 11.50 0 (+19.9(+19.900), improved sagittal balance ), improved sagittal balance by 8 cm.by 8 cm.

–– Significant improvement in VAS back (p<0.001)Significant improvement in VAS back (p<0.001)–– 29% Pseudoarthrosis rate29% Pseudoarthrosis rate

Compares with Spinal Deformity Study Group Compares with Spinal Deformity Study Group Occurred at the TL and LS junctions.Occurred at the TL and LS junctions.

Promising for ligamentous sparing in long constructs in attempts to Promising for ligamentous sparing in long constructs in attempts to prevent PJK/DJKprevent PJK/DJK

Still leaves a lot to be desired for pseudoarthrosis ratesStill leaves a lot to be desired for pseudoarthrosis rates Limited options if/when construct needs to extend to ilium.Limited options if/when construct needs to extend to ilium.

Wang MY, Mummaneni PV. Minimally invasive surgery for thoracolumbar spinal deformity: initial clinical experience with clinical and

radiographic outcomes. Neurosurg Focus (3):E9, 2010.

CasesCases

Case Presentation (Trauma)Case Presentation (Trauma)

75 year old retired aeronautical 75 year old retired aeronautical engineer had a five foot fall from engineer had a five foot fall from ladder.ladder.

No neurological deficitsNo neurological deficits

Severe midline back painSevere midline back pain

No calcium supplementation, No calcium supplementation, nonsmokernonsmoker

History of HTN, CADHistory of HTN, CAD

Case PresentationCase Presentation

TLICS: 4 ptsTLICS: 4 pts

TLISS: 4 ptsTLISS: 4 pts

70% Canal 70% Canal compromise, 30% compromise, 30% height lossheight loss

Surgical Options??Surgical Options??

Vaccaro AR, Lehman RA, Hulbert RJ, et al. A New Classification of Thoracolumbar Injuries. The importance of Injury Morphology, the Integrity of the Posterior Ligamentous Complex, and Neurological Status. Spine, 2005;30(20)2325-2333.

Vaccaro AR, Zeiller SC, Hulbert RJ, et al. The Thoracolumbar Injury Severity Score. A Proposed Treatment Algorithm. J Spinal Disord Tech, 2005;18(3)209-215.

Case PresentationCase Presentation

Minimally invasive Minimally invasive retroperitoneal, transpsoas retroperitoneal, transpsoas L2 corpectomyL2 corpectomy

Posterior L1Posterior L1--3 fusion3 fusion

Postop photographPostop photograph

Case Presentation (Trauma)Case Presentation (Trauma)

81 year old female who fell off a 81 year old female who fell off a ladder while pruning her rosesladder while pruning her roses

–– Severe back painSevere back pain

–– Left leg weakness, right femur fractureLeft leg weakness, right femur fracture

–– Previous L4Previous L4--5 TLIF for spondylolisthesis5 TLIF for spondylolisthesis

Preoperative CTPreoperative CT

Case Presentation Case Presentation (Degenerative Scoliosis)(Degenerative Scoliosis)

71 year old male with severe back 71 year old male with severe back pain and neurogenic claudicationpain and neurogenic claudication

–– Back pain made better with lying supineBack pain made better with lying supine

–– Claudication made better by flexed Claudication made better by flexed postureposture

–– Now unable to ambulate more than 30 Now unable to ambulate more than 30 yards yards

Preoperative XraysPreoperative Xrays Right Right

lumbar lumbar scoliosis scoliosis 232300

Flattening of Flattening of lumbar lumbar

lordosislordosis

Intraoperative Fluoroscopy Intraoperative Fluoroscopy –– Stage 1Stage 1

Intraoperative Xrays Intraoperative Xrays ––Stage 2Stage 2

Case Presentation Case Presentation (Flat Back Syndrome)(Flat Back Syndrome)

73 year old female with severe back 73 year old female with severe back pain and neurogenic claudication, pain and neurogenic claudication, progressive over the last 15 yearsprogressive over the last 15 years

–– Previous L4Previous L4--5 fusion 19885 fusion 1988

–– Severe pain when standing up straightSevere pain when standing up straight

–– Recently confined to her wheelchair from Recently confined to her wheelchair from painpain

Preop XrayPreop Xray

Preoperative scoliosis XraysPreoperative scoliosis Xrays

16cm positive 16cm positive sagittal balancesagittal balance

19.5 degree 19.5 degree right lumbar right lumbar scoliosisscoliosis

Preoperative MRIPreoperative MRI

Case Presentation Case Presentation (Spinal Metastasis)(Spinal Metastasis)

69 year old with metastatic renal cell 69 year old with metastatic renal cell carcinoma to T7carcinoma to T7

–– Followed initially on surveillance studies, Followed initially on surveillance studies, and received radiationand received radiation

–– Eventually progressed with the amount of Eventually progressed with the amount of back pain and spinal cord compressionback pain and spinal cord compression

Preoperative MRI and CTPreoperative MRI and CT

Thank YouThank You

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Decompression or Fusion? Spine 2010, 35;9S:S57Decompression or Fusion? Spine 2010, 35;9S:S57--S65.S65.O’Toole JE, Eichholz KM, Fessler RG. Surgical site infection rates after minimally invasive spinal surgery. J Neurosurg SpineO’Toole JE, Eichholz KM, Fessler RG. Surgical site infection rates after minimally invasive spinal surgery. J Neurosurg Spine 1111:471:471--476, 2009.476, 2009.

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Wang MY, Cummock MD, Yu Y, Trivedi RA. An analysis of the differences in the acute hospitalization charges following minimallWang MY, Cummock MD, Yu Y, Trivedi RA. An analysis of the differences in the acute hospitalization charges following minimally iy invasive versus nvasive versus open posterior lumbar interbody fusion. J Neurosurg Spine 12:694open posterior lumbar interbody fusion. J Neurosurg Spine 12:694--699, 2010.699, 2010.

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