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Randomized Controlled Trial
. 2013 Nov 14;347:f6415.
doi: 10.1136/bmj.f6415.

Interspinous Process Device Versus Standard Conventional Surgical Decompression for Lumbar Spinal Stenosis: Randomized Controlled Trial

Free PMC article
Randomized Controlled Trial

Interspinous Process Device Versus Standard Conventional Surgical Decompression for Lumbar Spinal Stenosis: Randomized Controlled Trial

Wouter A Moojen et al. BMJ. .
Free PMC article


Objective: To assess whether interspinous process device implantation is more effective in the short term than conventional surgical decompression for patients with intermittent neurogenic claudication due to lumbar spinal stenosis.

Design: Randomized controlled trial.

Setting: Five neurosurgical centers (including one academic and four secondary level care centers) in the Netherlands.

Participants: 203 participants were referred to the Leiden-The Hague Spine Prognostic Study Group between October 2008 and September 2011; 159 participants with intermittent neurogenic claudication due to lumbar spinal stenosis at one or two levels with an indication for surgery were randomized.

Interventions: 80 participants received an interspinous process device and 79 participants underwent spinal bony decompression.

Main outcome measures: The primary outcome at short term (eight weeks) and long term (one year) follow-up was the Zurich Claudication Questionnaire score. Repeated measurements were made to compare outcomes over time.

Results: At eight weeks, the success rate according to the Zurich Claudication Questionnaire for the interspinous process device group (63%, 95% confidence interval 51% to 73%) was not superior to that for standard bony decompression (72%, 60% to 81%). No differences in disability (Zurich Claudication Questionnaire; P=0.44) or other outcomes were observed between groups during the first year. The repeat surgery rate in the interspinous implant group was substantially higher (n=21; 29%) than that in the conventional group (n=6; 8%) in the early post-surgical period (P<0.001).

Conclusions: This double blinded study could not confirm the hypothesized short term advantage of interspinous process device over conventional "simple" decompression and even showed a fairly high reoperation rate after interspinous process device implantation.

Trial registration: Dutch Trial Register NTR1307.

Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare that the FELIX trial was funded by Paradigm Spine/InSpine and was carried out by the Leiden-The Hague SIPS group; no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.


Fig 1 Flow chart of enrollment and follow-up. IPD=interspinous process device
Fig 2 Scores on Zurich Claudication Questionnaire (top), modified Roland Disability Questionnaire (middle), and visual analogue scale (bottom) in two groups during follow-up. IPD=interspinous process device

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