The agenda for the U.S. FDA’s Sept. 8-9 advisory hearing includes a proposed down-classification of bone growth stimulator (BGS) devices to class II, but while the proposal met some resistance from an industry group, the panel sided with the FDA and declared BGS units ready for prime time as 510(k) devices.

The two-day hearing included a proposal to apply a class II designation to facet screw systems for spinal fixation, which have up to now been used without classification. While there were some concerns about data for neurological deficits accompanying device use, the panel voted unanimously to support this proposal.

‘Clearly not generic devices’

The FDA had previously thrown the question of down-classification of BGS devices to an advisory panel in 2006, during which industrial opposition to the move was also significant. That opposition resurfaced 14 years later and was embodied by the Bone Growth Stimulator Coalition, which counts Zimmer Biomet Holdings Inc., among its members. James Ryaby, an advisor to Orthofix Medical Inc., of Lewisville, Texas, advised the 2020 panel members that the findings from the 2006 panel are still valid, in part because the waveforms in the various devices are different. This is essentially a repeat of the argument made by Ryaby in 2006, and he reiterated the position, “these are clearly not generic devices.”

Ryaby said at the Sept. 8 hearing that there is no new knowledge to inform special controls, but also no new knowledge to support down-classification. Due to the lack of accumulated evidence, a sponsor should be required to generate level I and II clinical evidence, but Ryaby also argued that a preapproval inspection is critical to ensure consistent device production. The absence of a preclearance inspection authority for the FDA suggests that a PMA is crucial to ensuring consistent waveform production for the finished unit.

Stacey Bonnell of Depuy Synthes Co., of Westchester, Pa., countered with the claim that there is no unanimity in industry regarding the appropriate classification for BGS devices. Bonnell said the Orthopedic Surgical Manufacturers Association backs down-classification, adding that a class II designation would open the field for innovation and novel developments. “There is the potential for development of standards for the different stimulation types” as well, she said.

Charles Sansur of the Welch Group, who spoke on behalf of the American Association of Neurological Surgeons and the Congress of Neurological Surgeons, said the two associations fully support down-classification. Robert Muratore, chief scientific offers for Acoustic Sciences Associates (ASA) LLC, of Bethesda, Md., said ASA supports down-classification for devices that employ low-intensity pulsed ultrasound (LIPUS). LIPUS-based devices are improperly categorized as class III devices because they do not sustain or support life, and are not implanted, Muratore said, adding, “they do not present an unreasonable risk of illness or injury.” ASA is also of the view that a PMA imposes “an unreasonable cost and burden on innovation” and suppresses competition, he said.

The down-classification would apply to devices bearing the LOF and LPQ product codes for devices used as an adjunct to primary fusion. The FDA meeting documents indicate that there are at present nine BGS devices bearing PMAs, including one that was approved in 1979. Jesse Muir, a product reviewer for the FDA, said the agency is in possession of roughly 270 medical device reports filed since 1984, adding that localized reactions to the skin account for 187 of these. Each of these 187 reports was due to the use of an ultrasound that irritated the skin, and Muir commented that none of the serious adverse events could be directly attributed to the device.

Regarding the question of evidence, Muir said the FDA does not have a formal policy that requires randomized, controlled trials for PMA devices, there is not a mandate for a prospective, controlled study, and could include OUS studies. Muir acknowledged that there has been some historical difficulty in assessing fusion (or lack thereof), but noted that most of the PMA studies are at least a quarter of a century old. Broadly speaking, CT is credited with providing a more accurate assessment of device efficacy than flat-panel X-ray imaging,

In dealing with the FDA questions, the panel readily agreed that general controls are not sufficient for these devices, but the panel also foreshadowed its eventual stance by voting that these devices are neither life-supporting nor life-sustaining, although one panelist disagreed. The panel also voted that a sufficient body of information exists to develop a series of special controls. The panel further suggested that a degree of postmarket surveillance is indicated, and that a clinical study should be accompanied by a follow-up requirement of at least a year. However, interference with other devices is a concern voiced by the panel, although it is not clear how, or even whether, the FDA will react to this last observation.

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