The manufacturers of certain types of pedicle screw systems, called dynamic-stabilization systems, have been ordered by the U.S. Food & Drug Administration (FDA) to conduct post-marketing studies on a number of potential safety issues. Sixteen companies, including Johnson & Johnson and Zimmer Holdings Inc., currently market these devices.
The FDA cleared the first dynamic stabilization system component in 1997. Dynamic stabilization systems are used in spinal surgery and some are intended to provide stabilizing support to the spinal column during bone fusion. 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. According to the FDA, 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.
Dynamic stabilization systems differ from traditional, rigid stabilization systems that have been on the market for decades, and provide stability via screws inserted into segments of the spine. These systems are not intended to allow motion.
When intended as stabilizers during bone fusion, dynamic-stabilization systems are considered class II devices, and are subject to the FDA’s premarket notification requirement (also known as 510(k)). Devices subject to this requirement are cleared for marketing in the United States if the FDA finds them to be substantially equivalent to legally marketed predicate devices.
The FDA is now 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 postmarket surveillance studies 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.
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