title: IPD without bony decompression versus conventional surgical decompression for lumbar spinal stenosis: 2-year results of a double-blind randomized controlled trial.
abstract: OBJECTIVE
  Interspinous process devices (IPDs) are implanted to treat patients with intermittent neurogenic claudication (INC) based on lumbar spinal stenosis. It is hypothesized that patients with lumbar spinal stenosis treated with IPD have a faster short-term recovery, an equal outcome after 2 years and less back pain compared with bony decompression.
  
  
  METHODS
  A randomized design with variable block sizes was used, with allocations stratified according to center. Allocations were stored in prepared opaque, coded and sealed envelopes, and patients and research nurses were blind throughout the follow-up. Five neurosurgical centers (including one academic and four secondary level care centers) included participants. 211 participants were referred to the Leiden-The Hague Spine Prognostic Study Group. 159 participants with INC based on lumbar spinal stenosis at one or two levels with an indication for surgery were randomized into two groups. Patients and research nurses were blinded for the allocated treatment throughout the study period. 80 participants received an IPD and 79 participants underwent spinal bony decompression. The primary outcome at long-term (2-year) follow-up was the score for the Zurich Claudication Questionnaire. Repeated measurement analyses were applied to compare outcomes over time.
  
  
  RESULTS
  At two years, the success rate according to the Zurich Claudication Questionnaire for the IPD group [69 % (95 % CI 57-78 %)] did not show a significant difference compared with standard bony decompression [60 % (95 % CI 48-71 %) p value 0.2]. Reoperations, because of absence of recovery, were indicated and performed in 23 cases (33 %) of the IPD group versus 6 (8 %) patients of the bony decompression group (p < 0.01). Furthermore, long-term VAS back pain was significantly higher [36 mm on a 100 mm scale (95 % CI 24-48)] in the IPD group compared to the bony decompression group [28 mm (95 % CI 23-34) p value 0.04].
  
  
  CONCLUSIONS
  This double-blinded study could not confirm the advantage of IPD without bony decompression over conventional 'simple' decompression, two years after surgery. Moreover, in the IPD treatment arm, the reoperation rate was higher and back pain was even slightly more intense compared to the decompression treatment arm.
authors.affiliation: Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands. w.a.moojen@lumc.nl.|Department of Neurosurgery, Medical Center Haaglanden, The Hague, The Netherlands. w.a.moojen@lumc.nl.
authors.forename: Wouter A
authors.initials: WA
authors.lastname: Moojen
authors.affiliation: Department of Neurosurgery, Medical Center Haaglanden, The Hague, The Netherlands. m.arts@mchaaglanden.nl.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Arts
authors.affiliation: Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands. w.c.h.jacobs@lumc.nl.
authors.forename: Wilco C H
authors.initials: WC
authors.lastname: Jacobs
authors.affiliation: Department of Medical Statistics, Leiden University Medical Center, Leiden, The Netherlands. e.w.van_zwet@lumc.nl.
authors.forename: Erik W
authors.initials: EW
authors.lastname: van Zwet
authors.affiliation: Department of Medical Decision Making, Leiden University Medical Center, Leiden, The Netherlands. m.e.van_den_akker-van_marle@lumc.nl.
authors.forename: M Elske
authors.initials: ME
authors.lastname: van den Akker-van Marle
authors.affiliation: Department of General Practice, Erasmus Medical Center, Rotterdam, The Netherlands. b.koes@erasmusmc.nl.
authors.forename: Bart W
authors.initials: BW
authors.lastname: Koes
authors.affiliation: Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands. cvleggeert@lumc.nl.
authors.forename: Carmen Lam
authors.initials: CL
authors.lastname: Vleggeert-Lankamp
authors.affiliation: Department of Neurosurgery, Leiden University Medical Center, Leiden, The Netherlands. w.c.peul@lumc.nl.|Department of Neurosurgery, Medical Center Haaglanden, The Hague, The Netherlands. w.c.peul@lumc.nl.
authors.forename: Wilco C
authors.initials: WC
authors.lastname: Peul
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D013130:Spinal Stenosis / Q000601:surgery*
keywords: Bony decompression; Interspinous implants; Lumbar spinal stenosis; Randomized trial