The U.S. Food and Drug Administration today ordered manufacturers of certain types of pedicle screw systems, called dynamic stabilization systems, to conduct postmarket surveillance studies to collect clinical data on a number of potential safety issues, including fusion rates and frequency of additional surgeries.
Dynamic stabilization systems are used in spinal surgery and some are intended to provide stabilizing support to the spinal column during bone fusion. Currently, there is not enough clinical data to determine whether these dynamic stabilization systems provide enough spinal stability to allow for complete spinal fusion, as the system components may loosen, bend, or break over time. If fusion does not occur, a patient’s condition could worsen and possibly require additional surgical procedures.
The FDA is requiring postmarket studies to address these potential risks for systems already on the market. In addition, the FDA is requesting manufacturers with new dynamic stabilization systems or components to submit clinical information for agency review prior to marketing.
The FDA is not recommending any changes regarding the use of dynamic stabilization systems until it collects and reviews clinical data to better understand how these devices are being used. Patients who have or are considering the implantation of a dynamic stabilization system should consult with their health care practitioner.
Dynamic stabilization systems have different design features that allow bending or rotation while still facilitating fusion. Components used to achieve this flexibility include polymer cords, moveable screw heads, and springs.
Traditional, rigid stabilization systems have been on the market for decades, and provide stability via screws inserted into segments of the spine. The screws act as anchors that are then connected by uniform metallic rods, which immobilize the spinal segments and facilitate fusion. These systems are not intended to allow motion.
When intended as stabilizers during bone fusion, this type of device is class II and is subject to FDA’s premarket notification requirement (also known as 510(k)). Devices subject to this requirement are cleared for marketing in the United States if FDA finds them to be substantially equivalent to legally marketed predicate devices.
The FDA cleared the first dynamic stabilization system component in 1997. The FDA has cleared numerous dynamic stabilization systems or components since then. FDA has only ordered postmarket surveillance studies for the class II dynamic stabilization systems and components, which are intended for bone fusion.
The FDA has required the manufacturers of 16 dynamic stabilization systems or components on the market for spinal fusion to conduct postmarket surveillance studies, which must address the following:
- the fusion rate for dynamic stabilization systems compared to traditional stabilization systems;
- the incidence rate, severity, and time course of adverse events for dynamic stabilization systems compared to traditional stabilization systems;
- the type, incidence rate, and time course of subsequent surgical procedures for dynamic stabilization systems compared to traditional stabilization systems; and
- the cause of failure for dynamic stabilization systems based on analysis of all reasonable available systems that have been removed from patients, along with any association between the patient’s demographic and clinical data and the device failure.
In reviewing the clinical data gathered from the postmarket surveillance studies, the FDA will consider whether labeling changes or additional preclinical and clinical testing requirements are necessary for these devices.
Link to FDA’s Web site on 522 Postmarket Surveillance Studies: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfPMA/pss.cfm
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