In the 1970s, the government issued the Cooper report, detailing over 10,000 injuries that occurred from medical devices.¹ This report prompted the Medical Device Amendment Act (MDAA) of 1976, which laid the foundation for medical device regulation in the United States. A timeline for the legislation that has followed since the 1970s is demonstrated in Figure 1.

The MDAA organized medical devices into three classes. Class I devices are low-risk devices that have substantial evidence supporting their safety. “General controls,” such as maintenance of proper labeling and manufacturing processes, and reporting of adverse events are deemed sufficient regulation of Class I products. Class II devices are higher risk compared with Class I devices and require more regulation. Examples of Class II devices include sutures and bone wax,² as well as most orthopaedic implants including total knee arthroplasties, intramedullary nails, and most spinal implants. These are subject to a premarket process known as a 510(k) clearance that will be discussed in more detail in the next section. Following the premarket clearance, manufacturers of Class II devices must conduct postmarket surveillance. Class III devices are of substantial importance to sustaining or supporting human health but may present a “potential unreasonable risk of illness or injury,” and these are the most highly regulated. Mobile bearing total knee replacements and spinal disk replacements are both examples of Class III devices.

The FDA organizes devices by 16 medical specialty “panels” and lists orthopaedic devices under Part 888 under the Code of Federal Regulations Title 21.³ This is available online and helps delineate the classes of various orthopaedic implants.

Depending on the class of the device, the availability of a predicate device, and the target population characteristics of the device, there are four main pathways by which devices are approved. These four pathways are the premarket approval (PMA) pathway, the premarket
notification (PMN), which is also known as the 510(k) pathway, the product development protocol (PDP), and the humanitarian device exemption (HDE). Class III devices, those that potentially pose the highest risk to patients, are approved through a PMA, which is the most costly and arduous of the pathways.⁴ The device manufacturers must complete an investigational new device (IND) application as well as provide results from a small safety trial.² A prospective trial that compares the IND to currently available devices, which is needed to demonstrate efficacy, often involves significant cost to the manufacturer. The PMA is reviewed by the Office of Device Evaluation, which is part of the Center for Devices and Radiological Health (CDRH), one of the six main branches of the FDA. Following PMA, devices may undergo significant postmarket modification, or “drift,” and require monitoring via a PMA supplement review.⁵

Devices that have a “substantially equivalent” predicate device with which they compare may undergo a PMN pathway, which is also called the 510(k) process. Manufacturers must produce evidence that the proposed device has an equivalent predicate device. In 1990, a legislation was introduced that required “safety and efficacy” to also be demonstrated as part of the 510(k) pathway. The FDA typically reviews applications for devices under the 510(k) pathway, as described by the Federal Food, Drug, and Cosmetic Act within 90 days.

The average time for a manufacturer to recoup the cost of approval via the PMA process was 8.5 years compared with 2.4 years when the 510(k) pathway was used.⁶ To avoid the cost of a prospective randomized controlled trial, many more devices are approved via the 510(k) pathway (over 4,000/yr) compared with the PMA pathway (<100/yr).⁷ The 510(k) pathway results in FDA clearance rather than approval. This is an important distinction, as FDA approval provides immunity from litigation but clearance does not.¹ Day et al⁸ found that orthopaedic devices are increasingly cleared through the 510(k) pathway over the use of PMA compared with nonorthopaedic devices. The same authors identified that devices cleared through the 510(k) pathway had 11.5 times the odds of having a subsequent recall compared with the PMA pathway.⁸