Interspinous process device versus standard conventional surgical decompression for lumbar spinal stenosis: Randomized controlled trial

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.