Over the years, there have been a number of highly publicized instances where medical devices allowed to enter the market were later found to fail at higher-than-expected rates. While rheumatologists don’t implant medical devices, they do have an interest in how these devices work—and that they work well—because they may recommend the use of prosthetic joints and other kinds of medical devices to their patients.
“Among the various devices coming under question in recent years, there has been a significant concentration in the orthopedic realm,” says C. Ronald MacKenzie, MD, associate professor of clinical medicine (rheumatology and medical ethics) at the Hospital for Special Surgery, the Weill-Cornell Medical Center in New York. “These concerns are therefore relevant for the patients we look after as rheumatologists.”
Three Risk Categories
Requirements that makers of medical devices notify the Food and Drug Administration (FDA) before marketing a new product were established under section 510(k) of the Federal Food, Drug, and Cosmetic Act passed in 1938. The process in place today started following passage of the Medical Device Amendments Act in 1976.
The FDA has classified medical devices into three categories, according to their level of risk. “Class I presents the lowest risk and are exempt from any type of premarket approval [PMA],” says David Challoner, MD, vice president for health affairs emeritus of the University of Florida in Gainesville. “These are things like tongue depressors. They go directly to market after their manufacturing processes are reviewed and approved.”
The middle category, Class II, is by far the biggest group, with 90% of all devices authorized for market falling under this umbrella.1 These devices are thought to pose some risk to the consumer but can usually be marketed after submitting PMAs, called 510(k) applications after the section of the law, showing their “substantial equivalence” to another legally marketable device.
Class III devices pose the highest level of risk and must establish both safety and efficacy. This is the only level with that requirement, and generally requires PMA.
Substantial Equivalence
To understand both the reality and the concerns about the current 510(k) process, you have to understand the concept of substantial equivalence.
“Ford comes up with a new car that has an engine, four tires, seats; while there are some cosmetic differences they are not really all that different from other cars at the mechanical level,” says Matthew Kraay, MD, Kingsbury G. Heiple and Fred A. Lennon Professor of Orthopaedics, Case Western Reserve University, Cleveland. “Most devices are approved that way. You only have to point to something that was approved in the past, called a ‘predicate device,’ and convince the FDA that yours is the same as the earlier one.”