research article interspinous process decompression: expanding treatment...

Research ArticleInterspinous Process Decompression: Expanding TreatmentOptions for Lumbar Spinal Stenosis

Pierce D. Nunley,1 A. Nick Shamie,2 Scott L. Blumenthal,3 Douglas Orndorff,4

Jon E. Block,5 and Fred H. Geisler6

1Spine Institute of Louisiana, Shreveport, LA 71101, USA2Ronald Reagan UCLA Medical Center, Westwood, CA 90095, USA3Texas Back Institute, Plano, TX 75093, USA4Spine Colorado, Durango, CO 81301, USA52210 Jackson Street, Suite 401, San Francisco, CA 94115, USA6401 N. Wabash Avenue, Suite 62F, Chicago, IL 60611, USA

Correspondence should be addressed to Jon E. Block; [email protected]

Received 6 August 2016; Accepted 19 September 2016

Academic Editor: Anthony T. Yeung

Copyright © 2016 Pierce D. Nunley et al. This is an open access article distributed under the Creative Commons AttributionLicense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properlycited.

Interspinous process decompression is a minimally invasive implantation procedure employing a stand-alone interspinous spacerthat functions as an extension blocker to prevent compression of neural elements without direct surgical removal of tissue adjacentto the nerves. The Superion� spacer is the only FDA approved stand-alone device available in the US. It is also the only spacerapproved by the CMS to be implanted in an ambulatory surgery center. We computed the within-group effect sizes from theSuperion IDE trial and compared them to results extrapolated from two randomized trials of decompressive laminectomy. Forthe ODI, effect sizes were all very large (>1.0) for Superion and laminectomy at 2, 3, and 4 years. For ZCQ, the 2-year Superionsymptom severity (1.26) and physical function (1.29) domains were very large; laminectomy effect sizes were very large (1.07) forsymptom severity and large for physical function (0.80). Current projections indicate a marked increase in the number of patientswith spinal stenosis. Consequently, there remains a keen interest in minimally invasive treatment options that delay or obviate theneed for invasive surgical procedures, such as decompressive laminectomy or fusion. Stand-alone interspinous spacers may fill acurrently unmet treatment gap in the continuum of care and help to reduce the burden of this chronic degenerative condition onthe health care system.

1. Introduction

Lumbar spinal stenosis is a classic neural compression syn-dromewhere spine extension causes constriction of the nerveroots exiting the spinal column. Stenotic arthritic encroach-ment reduces the foraminal aperture resulting in the primarypatient complaint of intermittent neurogenic claudication [1].A simple postural solution to resolve these symptoms is tomove the spine into flexion thereby decompressing the nerveroots. The “gold standard” surgical option, laminectomy,decompresses the neural structures by directly removing

impinging ligament and bone [2]. Over 175,000 surgeries areperformed to treat spinal stenosis annually in the US, makingit the number one reason for spine surgery in the elderlypopulation [3].

As an alternative, interspinous process decompression isa minimally invasive procedure that builds on the conceptthat back extension is a seminal factor in the causativechain that instigates neurogenic claudication. This proce-dure involves the implantation of a stand-alone interspinousspacer that functions by serving as a lumbar vertebral jointextension blocker to prevent compression of neural elements

Hindawi Publishing CorporationBioMed Research InternationalVolume 2016, Article ID 3267307, 5 pageshttp://dx.doi.org/10.1155/2016/3267307

2 BioMed Research International

Figure 1: The Superion interspinous spacer.

in extension.The spacer blocks the extensionmotion withoutexposure or removal of tissue adjacent to the dura or exitingnerves [4].

On 20 May 2015, the US Food and Drug Administration(FDA) approved the Superion Interspinous DecompressionSystem (VertiFlex, San Clemente, CA, USA) for commer-cial distribution. Not requiring concomitant surgical decom-pression, this second generation stand-alone interspinousdevice is the only spacer commercially available to physiciansin the US (Figure 1). Following US regulatory approval, theSuperion achieved a number of consequential and significantregulatory and clinical milestones. First, the AMA CPT�Editorial Panel approved the addition of Category I CPTcodes to describe one- and two-level insertion of stand-alone interspinous spacers at their October 2015 meeting.Effective January 1, 2017, the new Category I codes willreplace the existing Category III CPT codes that applied tofirst generation spacers. Second, the Centers for Medicareand Medicaid Services (CMS) added the insertion of inter-spinous spacers to their list of approved surgical proceduresin Ambulatory Surgery Centers, effective January 1, 2016.Additionally, several peer reviewed publications of theSuperion Investigational Device Exemption (IDE) trial havedocumented the large, statistically significant improvementsachieved in condition-specific, pain, and functional clinicaloutcomes following device implantation at 6 months, 2 years,and 3 years [7–10]. Accomplishing this series of milestonessubstantiates the graduation of the Superion device from aconcept with potential to an acceptable and practical clinicalmodality for the treatment of intermittent symptoms ofneurogenic claudication secondary to moderate spinal steno-sis.

2. Materials and Methods

The Superion is indicated to treat skeletally mature patientssuffering from pain, numbness, and/or cramping in the legs(intermittent neurogenic claudication) secondary to a diag-nosis of moderate degenerative lumbar spinal stenosis, withor without Grade 1 spondylolisthesis, confirmed by X-ray,MRI, and/or CT evidence of thickened ligamentum flavum,narrowed lateral recess, and/or central canal or foraminalnarrowing. The Superion is indicated for those patients

with impaired physical function who experience relief inflexion from symptoms of leg/buttock/groin pain, numbness,and/or cramping, with or without back pain, and who haveundergone at least 6 months of nonoperative treatment. TheSuperion may be implanted at one or two adjacent lumbarlevels in patients in whom treatment is indicated at no morethan two levels, from L1 to L5 (Figure 2).

For this intended use, moderate degenerative lumbarspinal stenosis is defined as follows:

(i) 25% to 50% reduction in the central canal and/ornerve root canal (subarticular, neuroforaminal) com-pared to the adjacent levels on radiographic studies,with radiographic confirmation of any one of thefollowing:

(a) Evidence of thecal sac and/or cauda equinacompression

(b) Evidence of nerve root impingement (displace-ment or compression) by either osseous or non-osseous elements

(c) Evidence of hypertrophic facets with canalencroachment

(ii) Also associated with the following clinical signs:

(a) Present with moderately impaired physicalfunction (PF) defined as a score of ≥2.0 of theZurich Claudication Questionnaire (ZCQ)

(b) Ability to sit for 50 minutes without pain and towalk 50 feet or more.

To gauge the practical clinical significance of the publishedSuperion IDE findings, we computed the within-group (i.e.,Superion arm only) effect size at each annual postoperativeinterval compared to baseline for each clinical outcome sep-arately through 4 years using Cohen’s formula and thresholds[11, 12]. The effect size is computed as the standardizeddifference between two means or, simply put, the mean score(preop) – mean score (follow-up)/standard deviation of thechange. Effect sizes are typically reported in the range from0.0 (no effect) to >1.0 (very large effects) with the followingthresholds: 0.2 (small effect), 0.5 (medium effect), 0.8 (largeeffect), and >1.0 (very large effect). The effect size calculationprovides some normalization for baseline and distributionimbalances.

We identified two published laminectomy studies thatincluded at least one of the same outcomes as the SuperionIDE trial and included sufficient data to compute correspond-ing effect sizes. First, the Superion IDE results were comparedwith published findings for decompressive laminectomyby extrapolating within-group 4-year effect sizes for theOswestry Disability Index (ODI) from the published reportof the NIH-sponsored SPORT trial, the largest study ofsurgical and nonsurgical management of lumbar stenosis[5, 13]. Similarly, we estimated the 2-year effect size forZurich Claudication Questionnaire (ZCQ) symptom severityand physical function domains for decompressive laminec-tomy based on the published report of Stromqvist et al.[6].

BioMed Research International 3

(a) (b)

Figure 2: Anteroposterior (a) and lateral (b) plain radiographic images showing proper anatomical positioning of the Superion spacer in situ.

Effec

t siz

e

1.0

0.8

0.5

0.2

Very large

Large

1.111.2

1.05

1.37

1.03

1.46

1.07

1.26

0.8

1.29

Medium

Small

Outcomes

OD

I2yr

s

OD

I3yr

s

OD

I4yr

s

ZCQ

ss2

yrs

ZCQ

pf2

yrs

SuperionLaminectomy

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Figure 3: Within-group effect sizes calculated from the SuperionIDE trial in contrast with comparable effect size extrapolated fromthe SPORT trial [5] for ODI outcomes at 2, 3, and 4 years of follow-up and from Stromqvist et al. [6] for ZCQ symptom severity (ss) andphysical function (pf) at 2 years of follow-up.

3. Results

The comparative within-group effect sizes for Superion andlaminectomy treatments are provided in Figure 3. For backfunction, theODI results consistently showed very large effectsize estimates for both treatments at all follow-up inter-vals. Superion ODI effect sizes were particularly robust. Forcondition-specific impairment, the 2-year ZCQ results weresimilarly robust for Superion treatment with very large effectsizes for both the symptom severity and physical function

domains. In contrast, while laminectomy resulted in a verylarge effect size for symptom severity, the physical functiondomain result just met the threshold for a large effect size.Overall, the effect sizes for Superion were uniformly higherthan those reported for the “gold standard” treatment and didnot exhibit worsening with time.

4. Discussion

TheSuperion is the second “stand-alone” interspinous spacerapproved by the FDA and the only one currently availableon the US market. Importantly, the implantation proceduredoes not cause substantial alterations or disruptions to thespinal anatomy adjacent to neural structures. Specifically, theepidural space is not surgically exposed during spacer inser-tion, whereas laminectomy decompression directly opens theepidural space. The surgical exposure of the epidural spaceis known to routinely produce epidural scar, adhesions, andtethering around the dural sac and exiting nerve roots, whichcan cause symptomatic problems [14, 15]. Additionally, if sub-sequent surgical procedures are necessary to address progres-sive degenerative changes and/or reemergence of symptoms,the avoidance of the epidural space in the Superion placementreduces the complexity of future surgical options comparedto starting with a laminectomy procedure. Also, if deviceremoval is required, the implant can be explanted via thesame minimally invasive access as the original implantationprocedure. This suggests that interspinous spacers may beconsidered a reasonable “first line” option in the continuumof care for the treatment of moderate lumbar spinal stenosis(Figure 4).

The minimization of iatrogenic insult associated withimplantation of interspinous spacers significantly reduces therisk of operative adverse events. In a recent review of spinaldevices in the Medicare population, higher perioperativecomplication rates were found in decompression surgeries

4 BioMed Research International

Pedicle screws

Laminectomy FusionIndirect decompression

Moderate stenosis≤ grade 1 spondy

Severe stenosis ≥ grade 2 spondy

Mild stenosisno spondy

Nonoperativecare

Superion

Coflex®

Figure 4: The continuum of care of treatment for lumbar spinal stenosis. Superion represents the “first line” option for minimally invasivesurgical treatment.

compared to interspinous spacers [16]. Because of the min-imally invasive nature of the surgery, implantation of spacerscan be accomplished under local anesthesia in an ambulatorysurgical setting or with conscious sedation.

Lauryssen et al. [17] documented consistently similarclinical improvements in back and leg pain, back function,and condition-specific impairment for both the Superionand decompressive laminectomy at 2 years postoperatively.Herein, we found robust effect sizes (>1.0) at each postop-erative follow-up interval for ODI and ZCQ with Superiontreatment, uniformly higher than comparable effect sizeswithlaminectomy, and themagnitude of the effect sizewas durablethrough 4 years of follow-up.While estimates of the practicalclinical significance of the Superion compare favorably withpublished results for laminectomy, enthusiasm should betempered by the known limitations of using historical con-trols. Nevertheless, these results are encouraging and supportthe use of the Superion as an effective treatment option forlumbar spinal stenosis.

5. Conclusions

Interspinous spacers fill a distinct treatment gap in thecontinuum of care for patients with moderate degenerativelumbar spinal stenosis.These patients have exhausted conser-vative care butmay be inappropriate candidates for or unwill-ing to undergo surgical decompressive laminectomy. Becausespacers are implanted in aminimally invasive fashionwithoutanatomical disruption, they can be easily removed andconverted to laminectomy if symptoms reemerge. This studycorroborates previous reports that found similar clinicalbenefit provided by both spacers and laminectomy, providingthe patient with a minimally invasive surgical option withoutcompromising the extent or time duration of the symptomrelief.

Competing Interests

Dr. Block received support from VertiFlex to assist inmanuscript development. Dr. Blumenthal serves as Medical

Director at VertiFlex. All other authors declare that there isno conflict of interests regarding the publication of this paper.

Acknowledgments

The authors thank Terry Meredith for graphical assistance.

References

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[2] G.M.Overdevest,W. Jacobs, C. Vleggeert-Lankamp, C.Thome,R. Gunzburg, and W. Peul, “Effectiveness of posterior decom-pression techniques compared with conventional laminectomyfor lumbar stenosis,” Cochrane Database of Systematic Reviews,vol. 3, Article ID CD010036, 2015.

[3] R. A. Deyo, S. K. Mirza, B. I. Martin, W. Kreuter, D. C. Good-man, and J. G. Jarvik, “Trends, major medical complications,and charges associated with surgery for lumbar spinal stenosisin older adults,” The Journal of the American Medical Associa-tion, vol. 303, no. 13, pp. 1259–1265, 2010.

[4] V. Loguidice, W. Bini, S. Shabat, L. E. Miller, and J. E. Block,“Rationale, design and clinical performance of the Superion�Interspinous Spacer: aminimally invasive implant for treatmentof lumbar spinal stenosis,”Expert Review ofMedical Devices, vol.8, no. 4, pp. 419–426, 2011.

[5] J. N.Weinstein, T. D. Tosteson, J. D. Lurie et al., “Surgical versusnonoperative treatment for lumbar spinal stenosis four-yearresults of the spine patient outcomes research trial,” Spine, vol.35, no. 14, pp. 1329–1338, 2010.

[6] B. H. Stromqvist, S. Berg, P. Gerdhem et al., “X-stop versusdecompressive surgery for lumbar neurogenic intermittentclaudication: randomized controlled trial with 2-year follow-up,” Spine, vol. 38, no. 17, pp. 1436–1442, 2013.

[7] L. E. Miller and J. E. Block, “Interspinous spacer implant inpatients with lumbar spinal stenosis: preliminary results of amulticenter, randomized, controlled trial,” Pain Research andTreatment, vol. 2012, Article ID 823509, 10 pages, 2012.

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spinal stenosis: durable three-year results of a randomizedcontrolled trial,” Journal of Pain Research, vol. 8, pp. 657–662,2015.

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[10] V. V. Patel, P. G. Whang, T. R. Haley et al., “Two-year clinicaloutcomes of a multicenter randomized controlled trial compar-ing two interspinous spacers for treatment of moderate lumbarspinal stenosis,” BMC Musculoskeletal Disorders, vol. 15, no. 1,article 221, 2014.

[11] L. E. Kazis, J. J. Anderson, and R. F. Meenan, “Effect sizes forinterpreting changes in health status,”Medical Care, vol. 27, no.3, supplement, pp. S178–S189, 1989.

[12] G. M. Sullivan and R. Feinn, “Using effect size-or why the Pvalue is not enough,” Journal of Graduate Medical Education,vol. 4, no. 3, pp. 279–282, 2012.

[13] J. N. Weinstein, T. D. Tosteson, J. D. Lurie et al., “Surgical ver-sus nonsurgical therapy for lumbar spinal stenosis,” The NewEngland Journal of Medicine, vol. 358, no. 8, pp. 794–810, 2008.

[14] P. Fransen, “Prevention of scar tissue formation in spinal sur-gery: state of the art and review of the literature,” Journal ofNeurosurgical Sciences, vol. 55, no. 3, pp. 277–281, 2011.

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[16] R. A. Deyo, B. I. Martin, A. Ching et al., “Interspinous spacerscompared with decompression or fusion for lumbar stenosis:complications and repeat operations in the medicare popula-tion,” Spine, vol. 38, no. 10, pp. 865–872, 2013.

[17] C. Lauryssen, R. J. Jackson, J.M. Baron et al., “Stand-alone inter-spinous spacer versus decompressive laminectomy for treat-ment of lumbar spinal stenosis,” Expert Review of MedicalDevices, vol. 12, no. 6, pp. 763–769, 2015.

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