Interspinous process device does not improve short-term outcomes for stenosis patients

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According to a study published in the British Medical Journal, in patients with lumbar spinal stenosis, the use of an interspinous process device (Coflex, Paradigm Spine) is not significantly more effective than the gold standard treatment of bony decompression. 

Wouter Moojen (Department of Neurosurgery, Leiden University Medical Center, Leiden, and Medical Center Haaglanden, The Hague, The Netherlands) and others write that bony decompression is the gold standard for surgical management of lumbar spinal stenosis and that “all surgical techniques to treat lumbar spinal stenosis should be compared with this technique”. They add that the interspinous process device was designed as a minimally invasive technique of stabilising and increasing the interspinous distance with indirect compression of the dural sac and nerve roots, commenting there is the suggestion that the device provides better short-term outcomes than bony decompression. Therefore, the aim of the FELIX (Foraminal enlargement lumbar interspinous distraxtion) study was to assess whether the interspinous process device was more effective in the short term than conventional surgical decompression for patients with intermittent neurogenic claudication due to lumbar spinal stenosis.


In the prospective, double-blind, multicentre trial, patients with intermittent neurogenic claudication due to lumbar stenosis (after conservative treatment had failed) were randomised to be implanted with interspinous process device (80) or undergo bony decompression (79). The primary outcome measure was a disorder-specific functional score obtained by the Zurich Claudication Questionnaire.


At the short-term follow-up point (eight weeks), there were no significant differences in the number of patients who were deemed to have had a successful recovery—63% of patients who received the device vs. 72% of patients who underwent decompression (p=0.44). There were also no differences between groups, at eight weeks, in the Modified Roland Disability Questionnaire values (p=0.28), visual analogue scale back pain (p=0.09), visual analogue scale leg pain (p=0.54), the McGill Pain Questionnaire (p=0.70), and the Likert scale for perceived recovery (p=0.37). Furthermore while both operating time (24 minutes vs. 43 minutes, respectively; p<0.001) and blood loss (10–50ml vs. 50–100ml, respectively; p<0.001) were significantly reduced for patients receiving the device compared with those receiving bony decompression, hospital stay was similar between the two groups (1.83 days for the device vs. 1.89 days for the decompression; p=0.753). Moojen et al add: “Late reoperation due to absence of recovery was indicated and performed in 21 of 72 (29%) cases in the interspinous process device group compared with six of 72 (8%) in the bony decompression group (p<0.001).”


Based on their findings, they authors claim that they could not recommend the interspinous process device “considering the higher reoperation rate without a short term advantages and most likely with higher costs. We doubt if reimbursement of interspinous process devices by society is appropriate. Furthermore, this study shows that future research in spine surgery should be very critical in the evaluation of a so called favorable outcome and weigh this against the disadvantages in robust double blind randomised trials.”


Moojen told Spinal News International: “We don’t put in any implant in degenerative disease before proving it with good prospective studies or—preferably— robust doubly blind randomized clinical trials.”

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