Panel recommends the FDA not approve a minimally invasive lumbar stabilization system
The Orthopaedic and Rehabilitation Devices Panel of the Medical Devices Advisory Committee of the FDA voted when it met February 19 against three questions related to a premarket application for approval of the Medtronic DIAM Spinal Stabilization System.
Eleven voting members of panel, which included eight temporary voting members, voted down all three questions the FDA representatives at the meeting asked about the system’s safety and efficacy, as well as its benefits vs. its risks. However, a few experts on panel on the panel voted yes to the individual questions.
The meeting focused on the results of a clinical trial that compared the outcomes of a primary dataset of 97 patients who received the DIAM implant to 53 patients in a nonoperative control group. The device, which is “H”-shaped and is placed between two adjacent lumbar spinous processes (L2-5), is intended for patients with moderate low back pain (LBP) secondary to a single-level symptomatic lumbar degenerative disc disease (DDD) diagnosis.
Harvey E. Smith, MD, of the University of Pennsylvania, in Philadelphia, a temporary voting member of today’s panel, told Healio.com he voted against all three questions.
“I did not think there was substantial evidence to say it was definitively safe when we do not entirely understand the mechanism of the spinous process resorption, and given the fact that it was a relatively early follow-up and the nature of the device, that was a concern from the safety perspective, in my opinion,” Smith said.
Data from an animal model that was studied showed a possible negative reaction to the foreign body of the implant, according to Smith. This finding raised questions about safety of the implant, Smith noted in the interview with Healio.com after the meeting.
Representatives of the sponsor of the premarket approval application P140007, Medtronic Sofamor Danek USA, presented findings from the clinical trial for the device, which is implanted in a minimally invasive procedure between the spinous processes of the patient’s affected level. It has a stiff silicone core that reportedly transfers some of the axial spinal load through the device. This design is meant to load share with the posterior disc, anulus and facet joints, according to a presentation by Kathryn Simpson, PhD, director of Regulatory Affairs at Medtronic.
The proposed indications for the DIAM system in the PMA documentation were for skeletally mature patients with moderate LBP, with or without radicular pain, with the current episode lasting less than 1 year in duration secondary to lumbar DDD at a single symptomatic level from L2-5. Patients must have their DDD confirmed radiologically with one or more of the following factors: Greater than 2 mm decreased disc height vs. the adjacent level, scarring or thickening of the ligamentum flavum, anulus fibrosis, or facet joint capsule or herniated nucleus pulposus, according to documentation for the meeting.
The device is typically indicated for use in the treatment gap for patients who are not yet candidates for spinal fusion or total disc replacement surgery.
Overall success was defined as a greater than 15 point Oswestry Disability Index (ODI) improvement, the absence of any serious adverse events and no need for additional surgical procedures, which was defined as a failure.
According to the clinical trial results, 63.9% of patients in the DIAM group reached overall success at 12-months compared with 15.1% of the nonoperative control group, who received patient education plus either spinal injections, medications or physical therapy.
Among the patients treated with the DIAM system, 69.1% achieved more than a 15 point ODI improvement, 4.1% of them experienced secondary surgery failures and 8.2% experienced an associated serious adverse event.
Medtronic representatives noted in their presentation that spinous process fractures or erosions were observed in patients in the DIAM group throughout the clinical trial.
Brent Blumenstein, PhD, of Trial Architecture Consulting in Washington, D.C., said at the meeting he voted no on all three questions due to “serious issues with the information we got from the trial.
“I think the primary endpoint, as I pointed out, is mixed up and flawed with respect to its applicability to both arms. The proper emphasis on the intent-to-treat analysis was not done,” he said, which may have resulted in some bias.
The trial data show the device is safe at the 12-month follow up, but more data are needed to show the implant’s long-term safety and efficacy, Leonard Topoleski, MD, of the University of Maryland, said at the meeting. He also voted no on the three questions.
Smith agreed with Topoleski. He told Healio.com 12-month follow-up was not sufficient: “I thought for an implanted device that was a new design, given the spinous process resorption, the animal model data showing a reaction to the implant and also some data showing that there was some wear debris, 12 months was not a sufficient follow-up time in my opinion. I think there is clearly an effect of the study, the sponsors did a lot of work they should be commended for, tackling a difficult disease, but within the rigors of the data, as they were presented, the data just was not there in their present form to be able to vote yes for it.” – by Robert Linnehan