Open Access Research article

Two-year clinical outcomes of a multicenter randomized controlled trial comparing two interspinous spacers for treatment of moderate lumbar spinal stenosis

Vikas V Patel1, Peter G Whang2, Thomas R Haley3, W Daniel Bradley4, Pierce D Nunley5, Larry E Miller67, Jon E Block7* and Fred H Geisler8

Author Affiliations

1 University of Colorado Hospital, Denver, CO, USA

2 Yale Orthopaedics/Spine Service, New Haven, CT, USA

3 Performance Spine and Sports Physicians, P.C., Pottstown, PA, USA

4 Texas Back Institute, Denton, TX, USA

5 Spine Institute of Louisiana, Shreveport, LA, USA

6 Miller Scientific Consulting, Inc., Asheville, NC, USA

7 The Jon Block Group, 2210 Jackson Street, Suite 401, San Francisco, CA 94115, USA

8 The Chicago Back Institute at Swedish Covenant Hospital, Chicago, IL, USA

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BMC Musculoskeletal Disorders 2014, 15:221  doi:10.1186/1471-2474-15-221

Published: 5 July 2014



Interspinous spacers are a minimally invasive surgical alternative for patients with lumbar spinal stenosis (LSS) unresponsive to conservative care. The purpose of this prospective, multicenter, randomized, controlled trial was to compare 2-year clinical outcomes in patients with moderate LSS treated with the Superion® (Experimental) or the X-Stop®, a FDA-approved interspinous spacer (Control).


A total of 250 patients with moderate LSS unresponsive to conservative care were randomly allocated to treatment with the Experimental (n = 123) or Control (n = 127) interspinous spacer and followed through 2 years post-treatment. Complication data were available for all patients and patient-reported outcomes were available for 192 patients (101 Experimental, 91 Control) at 2 years.


Zurich Claudication Questionnaire (ZCQ) Symptom Severity and Physical Function scores improved 34% to 36% in both groups through 2 years (all p < 0.001). Patient Satisfaction scores at 2 years were 1.8 ± 0.9 with Experimental and 1.6 ± 0.8 with Control. Axial pain decreased from 59 ± 26 mm at baseline to 21 ± 26 mm at 2 years with Experimental and from 55 ± 26 mm to 21 ± 25 mm with Control (both p < 0.001). Extremity pain decreased from 67 ± 24 mm to 14 ± 22 mm at 2 years with Experimental and from 63 ± 24 mm to 18 ± 23 mm with Control (both p < 0.001). Back function assessed with the Oswestry Disability Index similarly improved with Experimental (37 ± 12% to 18 ± 16%) and Control (39 ± 12% to 20 ± 16%) (both p < 0.001). Freedom from reoperation at the index level was 84% for Experimental and 83% for Control (log-rank: p = 0.38) at 2 years.


Both interspinous spacers effectively alleviated pain and improved back function to a similar degree through 2 years in patients with moderate LSS who were unresponsive to conservative care.

Trial registration


Interspinous spacer; Lumbar spinal stenosis; Minimally invasive; Randomized controlled trial; Superion