Medical Devices — Balancing Regulation and Innovation
Many Americans benefit from the implantation of medical devices, such as artificial joints and lifesaving defibrillators. Tragically, many also suffer or even die from complications related to medical devices that were never studied in clinical trials before being implanted in patients. As devices have evolved and become more complex, our device-approval system has become incapable of assuring safety and effectiveness. The system we use today was created 35 years ago in an era of much simpler and fewer devices, and it is now outdated.
A recent, but not rare, example provides a cautionary tale about the challenges of ensuring that complex medical devices are both effective and safe. Osteoarthritis of the hip joint is a common and debilitating disorder. Each year, nearly a quarter of a million patients with advanced painful arthritis receive a total hip replacement in the hope that it will restore mobility and improve their quality of life. Conventional artificial hip implants consist of a metal ball inserted into a plastic cup. In 2005, a new metal-on-metal design was introduced in which both components were made from a metal alloy. The design was touted as a major innovation that would improve durability and reduce the risk of hip dislocation — advantages that were especially appealing to younger patients but were never tested.
One metal-on-metal design is the DePuy (Johnson & Johnson) ASR XL Acetabular System, which was introduced into the U.S. market in 2005. The ASR was cleared by a Food and Drug Administration (FDA) process known as 510(k), which refers to the section of the 1976 Medical Device Amendments to the Federal Food, Drug, and Cosmetic Act that created it. Under that section, the criterion for clearance of a new medical device is that it be “substantially equivalent” to an already-marketed device (a “predicate”); clinical data are not required.
The ASR was constructed by borrowing a metal alloy cup from a different hip device known as the ASR Hip Resurfacing System and retrofitting it onto a standard hip implant. The manufacturer successfully made the case that the re-engineered implant was “substantially equivalent” to a predicate device. Its marketing clearance was therefore based not on clinical trials or other clinical data but on bench testing in a laboratory, which was inadequate to simulate the stresses that would be placed on it in patients’ bodies.
It soon became clear that the device failed at the astonishing rate of at least one in eight. According to a recent report presented at the British Hip Society Annual Conference, 21% of these hips have had to be replaced (revised) by 4 years after implantation, and the revision rate rises to 49% at 6 years, as compared with 12 to 15% at 5 years for other devices. Failure appears to be due to erosion of the metal in the articular surfaces and migration of metallic particles into the surrounding tissues and the bloodstream. Thus, the innovation led to tragedy for many patients. Before it was recalled in 2010, the ASR had been implanted in nearly 100,000 patients, and the result was a public health nightmare.