FDA orthopedic panel: PMA application for spine stabilization system ‘not approvable’

Panelists reviewed data for Zimmer’s Dynesys device, which has already been used in 40,000 cases worldwide.

By Susan M. Rapp
November 2009, Copyright ® 2009 SLACK Incorporated.

In a 5 to 1 vote today, the FDA Orthopaedic and Rehabilitation Devices advisory panel did not recommend approving Zimmer Spine’s premarket approval (PMA) application P070031 for marketing clearance of the Dynesys Spinal System, a dynamic non-fusion spine stabilization system.

One panelist abstained from voting.

Officials from Zimmer Spine were seeking the panel’s favorable recommendation to the FDA for use of the Dynesys system in one or two contiguous levels from L1 to S1 in the lumbar spine in skeletally mature patients requiring spinal alignment and stabilization.

The device has been used outside the United States since 1994 and received the European CE mark in 1999.

Needs clearer indications

The FDA previously cleared the Dynesys system as an adjunct to fusion surgery, but with this application, the sponsor sought a non-fusion indication that would allow Dynesys to be used without bone graft in individuals with symptoms consistent with spondylolisthesis up to Grade 1 and spinal stenosis or stenosing lesions.

John D. Kelly IV, MD, of Philadelphia, the panel’s acting voting chair, told ORTHOSuperSite he was surprised by the vote results and noted that the panel’s opinion only represents a recommendation to the FDA. The federal agency will make a final approval decision.

Kelly said he likely would have voted for approving the device with conditions.

“The rest of the panel really felt that the long-term data just were not there. There were too many safety concerns,” he said.

Panel members also said they voted against approving the device due to possible screw breakage after long-term use and the absence of a clear definition of the kind of patient for which the device is indicated.

A challenging study

At the end of the day, temporary voting member Raj Rao, MD, of the Medical College of Wisconsin in Milwaukee, said he remained unconvinced by the device’s safety and effectiveness data.

“I think the study has fallen apart at some places. … We have dropout from the study, so we have inadequate follow-up information to make a clear determination as to the efficacy,” he said. Also, “There are substantial questions as to the safety aspect of the construct given concerns with screw issues, including loosening, lucency, migration and screw fracture.”

Patients enrolled in Zimmer Spine’s clinical trial for this PMA application failed 3 months of nonoperative treatment. They were randomized (2:1) so that by the time study data were analyzed, 217 patients received the titanium pedicle screws, flexible polyethylene cord and polycarbonate urethane spacers of the Dynesys device through a posterior approach. Eighty-nine patients received a control procedure: fusion with a pedicle screw-based device made by Zimmer Spine with bone grafting.

The patients were followed for 24 months, at which time the overall clinical success was 52.1% in the Dynesys and 40.4% in the control group.

Future consideration

Spine surgeon Edward N. Hanley, MD, of Charlotte, N.C., who made the first motion at the meeting to approve the device with conditions — which was not seconded — said the sponsor did “a good job with the usual difficult situation in clinical spine surgery and provided us with appropriate, adequate information to make a determination of approvability. In my opinion, they have demonstrated for the indications proposed [both] safety and effectiveness.”

His proposed conditions for approval concerned labeling and the post-approval study.

A few panel members and some industry representatives suggested that the FDA consider the sponsor’s application again in the future, along any with any additional supplemental and post-hoc study data collected.

As part of a new requirement, FDA reviewers analyzed payments that physicians participating in the Dynesys PMA study received and included their findings in documentation for the meeting. They reported that 10 of 26 sites, where about 54% of Dynesys and 54% of control patients were treated, received total compensation from Zimmer Holdings Inc. or Zimmer Spine of more than $100,000.