Evid Based Spine Care J 2011; 2(1): 45-56
DOI: 10.1055/s-0030-1267086
Systematic review
© Georg Thieme Verlag KG Stuttgart · New York

Efficacy of interspinous device versus surgical decompression in the treatment of lumbar spinal stenosis: a modified network analysis

Dean Chou1 , Darryl Lau2 , Jeffrey Hermsmeyer3 , Daniel Norvell3
  • 1University of California, San Francisco, CA, USA
  • 2University of Michigan Medical School, Ann Arbor, MI, USA
  • 3Spectrum Research Inc, Tacoma, WA, USA
Further Information

Publication History

Publication Date:
10 May 2011 (online)

ABSTRACT

Study design: Systematic review using a modified network analysis.

Objectives: To compare the effectiveness and morbidity of interspinous-device placement versus surgical decompression for the treatment of lumbar spinal stenosis.

Summary: Traditionally, the most effective treatment for degenerative lumbar spinal stenosis is through surgical decompression. Recently, interspinous devices have been used in lieu of standard laminectomy.

Methods: A review of the English-language literature was undertaken for articles published between 1970 and March 2010. Electronic databases and reference lists of key articles were searched to identify studies comparing surgical decompression with interspinous-device placement for the treatment of lumbar spinal stenosis. First, studies making the direct comparison (cohort or randomized trials) were searched. Second, randomized controlled trials (RCTs) comparing each treatment to conservative management were searched to allow for an indirect comparison through a modified network analysis approach. Comparison studies involving simultaneous decompression with placement of an interspinous device were not included. Studies that did not have a comparison group were not included since a treatment effect could not be calculated. Two independent reviewers assessed the strength of evidence using the GRADE criteria assessing quality, quantity, and consistency of results. The strengths of evidence for indirect comparisons were downgraded. Disagreements were resolved by consensus.

Results: We identified five studies meeting our inclusion criteria. No RCTs or cohort studies were identified that made the direct comparison of interspinous-device placement with surgical decompression. For the indirect comparison, three RCTs compared surgical decompression to conservative management and two RCTs compared interspinous-device placement to conservative management. There was low evidence supporting greater treatment effects for interspinous-device placement compared to decompression for disability and pain outcomes at 12 months. There was low evidence demonstrating little to no difference in treatment effects between the groups for walking distance and complication rates.

Conclusion: The indirect treatment effect for disability and pain favors the interspinous device compared to decompression. The low evidence suggests that any further research is very likely to have an important impact on the confidence in the estimate of effect and is likely to change the estimate. No significant treatment effect differences were observed for postoperative walking distance improvement or complication rates; however, findings should be considered with caution because of indirect comparisons and short follow-up periods.

STUDY RATIONALE AND CONTEXT Traditionally, the most effective treatment for degenerative lumbar spinal stenosis is through surgical decompression 1. Recently, interspinous devices have been used in lieu of standard laminectomy. The idea of using a device to distract the spinous processes for symptomatic relief is not new. It was first used in the 1950 s but was abandoned secondary to device dislodgement, poor clinical indications, and implant malfunction. It is only recently that interspinous devices are being more popularized with various designs (from static spacers to dynamic devices) composed of an array of materials including allograft, titanium, polyetheretherketone, and elastomeric compounds. The mechanical mechanism by which interspinous devices are purported to treat spinal stenosis is to focally create slight spinal flexion by distraction of the spinous processes. This mimics the position of sitting, which increases the room for the nerves, potentially alleviating pain. Implantation of interspinous devices is a relatively straightforward surgical procedure and can be performed under local anesthesia. However, it is important to clearly identify evidence of whether interspinous devices are able to provide effective treatment and achieve similar goals to surgical decompression for degenerative lumbar spinal stenosis. In addition, the placement of interspinous devices is touted to be less morbid than a standard surgical decompression. OBJECTIVES To compare the effectiveness of interspinous-device placement versus surgical decompression for the treatment of lumbar spinal stenosis. To compare the morbidity of interspinous-device placement versus surgical decompression for the treatment of lumbar spinal stenosis. MATERIALS AND METHODS Study design: Systematic review using a modified network analysis for indirect comparisons. Sampling: Search: PubMed, Cochrane collaboration database, and National Guideline Clearinghouse databases; bibliographies of key articles. Dates searched: 1970 through March 2010. Inclusion criteria: Patients with lumbar spinal stenosis. Randomized controlled trials (RCTs) and nonrandomized comparison studies. RCTs only for indirect comparisons. Exclusion criteria: Trauma, significant lumbar instability, previous lumbar spine surgery, spondylolisthesis > grade I and patient younger than 40 years. Comparison studies involving decompression surgery with simultaneous interspinous-device placement. Case series of interspinous-device placement or decompression surgery were not included because of the inability to calculate treatment effects without a comparison group. Outcomes: Disability, pain, function, and morbidity measures. Analysis: Changes in outcome scores from baseline to follow-up and complication rates were extracted for all studies. Treatment effects were calculated by comparing change scores between treatment groups. For the studies without a direct comparison between surgical decompression and interspinous-device placement, a modified network analysis for indirect treatment comparisons was made. The treatment effect was calculated by comparing the treatment effects of decompression versus conservative management to the treatment effects of interspinous-device placement to conservative management. Mean treatment effects between studies were compared. Complications were pooled; however, scores from functional measures were not pooled. Two independent reviewers assessed the strength of evidence using the GRADE criteria assessing quality, quantity, and consistency of results. Quality of evidence was downgraded for indirect comparisons and for small number of studies. Details about methods can be found in the electronic supplemental material at www.aospine.org / ebsj

REFERENCES

  • 1 Weinstein J N, Tosteson T D, Lurie J D. et al . Surgical versus nonsurgical therapy for lumbar spinal stenosis.  N Engl J Med. 2008;  358 (8) 794-810
  • 2 Richter A, Schütz C, Hauck M. et al . Does an interspinous device (Coflex) improve the outcome of decompressive surgery in lumbar spinal stenosis? One-year follow up of a prospective case control study of 60 patients.  Eur Spine J. 2010;  19 (2) 283-289
  • 3 Park S C, Yoon S H, Hong Y P. et al . Minimum 2-year follow-up result of degenerative spinal stenosis treated with interspinous u (coflex).  J Korean Neurosurg Soc. 2009;  46 (4) 292-299
  • 4 Malmivaara A, Slätis P, Heliövaara M. et al . Surgical or nonoperative treatment for lumbar spinal stenosis? A randomized controlled trial.  Spine. 2007;  32 (1) 1-8
  • 5 Weinstein J N, Tosteson T D, Lurie J D. et al . Surgical versus nonoperative treatment for lumbar spinal stenosis four-year results of the Spine Patient Outcomes Research Trial.  Spine. 2010;  35 (14) 1329-1338
  • 6 Zucherman J F, Hsu K Y, Hartjen C A. et al . A prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: 1-year results.  Eur Spine J. 2004;  13 (1) 22-31
  • 7 Zucherman J F, Hsu K Y, Hartjen C A. et al . A multicenter, prospective, randomized trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication: two-year follow-up results.  Spine. 2005;  30 (12) 1351-1358

EDITORIAL STAFF PERSPECTIVE

There are several noteworthy factors regarding this topic and the systematic review as performed:

The current strength of evidence favoring interspinous spacers compared to decompression surgery with or without fusion regarding factors of disability and pain is low, meaning that „Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.”

  • There was general surprise voiced that there is no direct comparison study between decompression surgery alone (in properly selected patients) and interspinous spacers without decompression. For various reasons the higher-grade evidence relies on comparisons, such as interspinous spacers versus nonoperative modalities, decompression and fusion versus decompression and surgical decompression versus nonoperative treatment. The absence of the most compelling form of comparison studies—decompression alone versus interspinous spacer for more stable forms of stenosis and decompression and fusion versus decompression and interspinous spacer for more unstable forms of stenosis—was quoted as being „lamentable” and „overdue for correction.”

  • The absence of clinically relevant direct comparison studies necessitated a ‘network analysis’ with its inherent shortcomings of error through heterogeneity of its study cohorts and lower level of familiarity to a clinician community.

  • The short-term follow-up of studies with interspinous spacers (12 months) was noted to likely underreport complications, such as device loosening and need for more complex revision surgery for patients with interspinous devices, which would appear to be more likely to fail with time.

  • The impact of patients’ complications with interspinous devices as expressed in invasiveness of potential corrective surgery compared to less expensive and simple decompression surgery is presently not understood.

  • The potential for financial conflict of interest affecting several authors related to the development and subsequent marketing of certain interspinous devices was pointed out. To date there are no prospective comparison studies from financially disinterested third-party groups.

Case example

(Case provided by Jens Chapman)

Two years after L3 / 4 interspinous process-spacer placement a physically very active and healthy 65-year-old man presented with severe bilateral leg pain brought on by short-distance walking and relieved by bending and squatting (Fig [3a], Fig [3b], Fig [3c]). At the time the procedure had brought substantial symptom relief, however progressive symptom recurrence was noted about 18 months after the index procedure. The patient was found to have an X-Stop device at his L3 / 4 interspace with heterotopic bone formation surrounding the implant, as well as a subtle grade 1 degenerative spondylolisthesis.

The MRI scan revealed persistent significant central stenosis with facet hypertrophy and lateral recess compromise (Fig [3d]).

Because of failure of nonoperative treatment the patient underwent removal of the device and simple midline-sparing hemilaminotomies with partial facetectomies through a keyhole laminotomy approach (Fig [3e]). Abundant heterotopic bone surrounding the implant was carefully removed, while avoiding injury to the ligaments. Since decompressive surgery the patient experienced complete relief of lower extremity and back symptoms and return to activities of daily living including competitive golf 6 months to date.

This case illustrates some concerns about interspinous spacers. The role of simple soft-tissue–sparing decompression surgery, while avoiding destabilizing measures, compared to an implant-based nonfusion procedure remains to be established and cannot be concluded based on the current state of the literature. Does a nonfusion device in fact set up patients for more revision surgeries in the intermediate and longer run compared to simple decompression or fusion surgery in appropriately selected patient? Another question worth debating is how long does a satisfactory result in elective spine surgery have to last to be counted as a success? Alternatively, when is a revision procedure performed at an index level a complication? This case certainly illustrates some of the many unanswered questions.

Fig. 3a Preoperative x-ray (AP view).

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Fig. 3b Preoperative x-ray (extension).

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Fig. 3c Preoperative x-ray (flexion).

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Fig. 3d Magnetic resonance imaging (axial).

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Fig. 3e The intraoperative site revealed extensive foreign body debris (dark spots) and abundant reactive connective tissue build up around the area of the interspinous spacers.

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