Interspinous spacer for lumbar stenosis likely not inferior to existing device

SAN FRANCISCO — An interspinous device designed to treat patients with lumbar spinal stenosis implanted using a minimally invasive technique was associated with good clinical results at short-term follow-up, according to findings from a prospective, randomized, multicenter FDA investigational device exemption (IDE) trial presented here at the International Society for the Study of the Lumbar Spine Annual Meeting.

According to Scott L. Blumenthal, MD, the study’s noninferiority criteria were met at 24 months, which was the endpoint of the study. In all, 391 patients with lumbar stenosis at one or two levels were randomly assigned on a 1:1 basis to receive either the Superion Interspinous Spacer System (Vertiflex) or the device to which it was being compared, the X-STOP device (Medtronic).

The X-STOP device was the only interspinous spacer on the market at the time the study began, so it was used as the control device, according to Blumenthal.

Scott L. Blumenthal

“Both devices produced statistically significant improvements by 6-week follow-up that was maintained through the 24- and 36-month treatment follow-up. This prospective study indicates that interspinous devices produce good outcomes in appropriately selected patients with mild-to-moderate stenosis,” he said.

The investigation compared both devices in terms of composite findings for the Zurich Claudication Questionnaire and Oswestry Disability Index scores, VAS back and leg pain, and other factors, such as rates of reoperations and complications. Blumenthal showed graphs of the results that indicated all the clinical scores improved significantly in both groups, by about 50%, at as early as 6 postoperative weeks after surgery, and those improvements were maintained for the duration of follow‐up.

“The radiographic observations between the two groups, as you can see — 11% and 13% — were comparable. The X-STOP device had a combination of spinous process fractures and device dislodgements or migrations. Interesting enough, and as suspected, it is the method of insertion: There were no migrations or dislodgements in the Superion (group); just spinous process fractures were the only radiographic observations. Revisions were comparable between the two groups, as well,” Blumenthal said.

He noted the IDE trial results are now in the public domain, and the Superion system was cleared by the FDA in recent weeks. – by Susan M. Rapp

Reference:

Blumenthal SL, et al. Paper #60. Presented at: International Society for the Study of the Lumbar Spine Annual Meeting; June 8-12, 2015; San Francisco.

Disclosure: Blumenthal reports he is a paid consultant to and has stock/stock options with Vertiflex.