Superion Interspinous Process Spacer for Intermittent Neurogenic Claudication Secondary to Moderate Lumbar Spinal Stenosis: Two-Year Results from a Randomized Controlled FDA-IDE Pivotal Trial

Study Design. Prospective, multicenter, randomized, controlled, investigational device exemption noninferiority trial. Objective. To determine 2-year outcomes in patients with intermittent neurogenic claudication secondary to moderate lumbar spinal stenosis (LSS) who were treated with the Superion interspinous process spacer. Summary of Background Data. Interspinous spacers are a less-invasive treatment alternative compared with surgical decompression for patients with LSS unresponsive to conservative care. High-quality comparative data with these devices are lacking. Methods. Patients presenting with intermittent neurogenic claudication secondary to moderate LSS who failed at least 6 months of nonsurgical management were randomly allocated to treatment with the Superion spacer or a control spacer (X-Stop) and followed for 2 years. Results. A total of 391 randomized patients were implanted with Superion (n = 190) or control (n = 201) spacers at 29 sites in the United States between August 2008 and December 2011. Implants were successfully implanted in 99.5% of patients with Superion and 99.0% of control patients. The primary composite endpoint of this study was met, which demonstrated that the Superion spacer was noninferior to the X-Stop spacer. Leg pain, the predominant patient complaint, decreased in severity by 70% during 2 years in each group. Most (77%) patients achieved leg pain clinical success (improvement ≥20 mm) at 2 years. Back pain clinical success (improvement ≥20 mm) was 68%, with no differences between groups. Oswestry Disability Index clinical success (≥15% point improvement) was achieved in 65% of patients. The rates of complications and reoperations were similar between groups. Conclusion. The Superion interspinous process spacer relieves symptoms of intermittent neurogenic claudication secondary to moderate LSS in the majority of patients through 2 years.