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Ortho panel recommends FDA approval of VertiFlex spinous spacer by 5-1 vote, 2 abstentions

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The Orthopaedic and Rehabilitation Devices Panel of the Medical Devices Advisory Committee of the FDA voted in favor of three questions posed to them when they met February 20 about the safety, efficacy and benefits vs. perceived risks of an interspinous spacer device to treat moderate lumbar spinal stenosis.

The sponsor, VertiFlex Inc., San Clemente, Calif., manufactures the Superion InterSpinous Spacer (ISS), and presented its premarket approval application (PMA) (P140004).

Eight voting members of the panel were presented with three questions at the meeting. For the first two questions put to the panel members, which included spine surgeons, orthopedic surgeons, biostatisticians and other experts, they voted 5 to 1, with two abstentions, which meant they felt there was reasonable assurance the sponsor’s device was safe to treat moderate lumbar spinal stenosis and was effective in patients who met the criteria specified in the proposed indications.

The proposed indications were for skeletally mature subjects suffering from pain, numbness, and/or leg cramping (neurogenic intermittent claudication) secondary to a diagnosis of moderate lumbar spinal stenosis, with or without Grade 1 spondylolisthesis.

Spinous process fractures were focused on in the FDA’s questions to the panel. When asked at the end of the meeting if the probable benefits of the sponsor’s device outweighed the probable risks, four panel members voted yes, two voted no and two abstained.

Following the meeting, Raj D. Rao, MD, chair of the FDA Orthopaedic and Rehabilitation Panel and a Spine Surgery Today Editorial Board member, told Healio.com, the panel generally supported the VertiFlex PMA.

"Having said that, there were some general concerns with the comparator group and how the comparator group X-STOP resulted in less than optimal results for our patients,” he said.

The meeting focused on results of the Superion investigational device exemption trial, which enrolled 470 adults with moderate spinal stenosis treated at 31 U.S. centers who were randomized 1:1 to receive the Superion ISS or the X-STOP (Medtronic; Langhorne, Pa.) device, an implant with similar indications used as a control treatment.

The data included 190 subjects with the Superion ISS and 201 with the X-STOP device. Success in the study was defined as an individual with clinically significant improvement in outcomes compared to baseline for at least two of three domains of the Zurich Claudication Questionnaire and without any clinically significant confounding treatments, such as epidural steroid injections, nerve block procedures or spinal cord stimulators.

Some patients enrolled in the trial never proceeded to the treatment phase.

At 24-months follow-up, 52.7% of the Superion ISS group and 50.2% of the X-STOP group were considered successful. However, study data showed spinous process fractures developed after treatment in 16.3% of Intent-to-Treat (mITT) subjects in the Superion ISS group and 8.5% of control mITT subjects.

Some fractures in both groups exhibited healing at various times during follow-up, according to the executive summary for the PMA.

“The panel was asked to judge whether the spinous process fracture by itself was a substantial safety issue and I think the panel generally felt the spinous process fractures were not a substantial safety issue, but did raise concerns about the possible loss of effectiveness with the device in time,” Rao said.

When asked why he voted no to question three concerning benefits vs. risks, S. Raymond Golish, MD, PhD, a voting member of the panel who in private practice in orthopedic and spine surgery in Jupiter, Fla., said,

“As I thought through it, I am not convinced we understand all of the probable risks, and so I could not say yes that the benefits outweigh the risks because I am not assured for myself that we have identified and properly assessed all of those risks. So, as a result of that, in question one, the safety, I could not then make a vote of yes for safety without better understanding the probable risks. So, I voted no.” – by Robert Linnehan

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