FDA Initiating Review of Corrosion Tied to Metal-on-Metal Hip Implants

In the United States, metal-on-metal hip implants, as a class of medical devices, have long been the focus of safety concerns in the orthopedic community. Linked to an array of significant adverse reactions, federal regulators have announced a planned study concerning the devices’ association with corrosion.

The metal-on-metal hip devices were approved under the U.S. Food and Drug Administration’s (FDA) fast-tracked 510(k) approval process. Under this process, device makers are able to bypass clinical testing of their products if a device is found to be substantially similar to an already-approved device. While the devices were released to market under the 510(k), studies reveal that metal-on-metal devices fail far more frequently than similar, but non-all-metal devices.

This January, the agency proposed stronger regulations that would mandate that manufacturers of metal-on-metal hip devices prove implant safety and efficacy prior to selling them. According to Health Point Capital, the FDA seeks to close the so-called “loophole” in the federal Medical Device Amendments of 1976 under which medical devices were initially regulated.

The move followed increasing evidence that revealed the metal-on-metal systems fail prematurely and at increased rates and that the devices have led to serious bone and tissue damage due to their release of metallic debris with typical movement, such as walking. Mounting injury reports and litigation note metallosis (metal poisoning) as an alleged reaction to the devices, which typically leads to a need for revision surgery to remove and replace the device.

The FDA cited a “renewed concern of wear and corrosion of conical head/stem taper junctions in modern modular total hip replacements,” commissioning a study to better understand the links between the devices’ “volumetric” wear and corrosion in total hip replacement surgeries, as well as potential links to clinical outcomes, according to Health Point Capital. The study will take approximately two years to complete and will review about 250 explanted (removed) metal-on-metal hip devices of various sizes and genders. The American Society for Testing and Materials (ASTM) protocol for corrosion testing will be used to analyze the devices.

The project’s objective is to create a peer-reviewed journal article that will explain ties between wear and corrosion and relevant parameters—how long the device’s were implanted, lateral offset, device head size, materials, and modularity—which are meant to provide assistance with test methodology development as well as specific controls needed for pre-clinical trials of total hip implants, Health Point Capital reported

Metal-on-metal hip devices were designed to provide increased durability and longevity, as the devices’ seemingly stronger components were believed to be able to provide increased benefits over traditional devices constructed with plastic or ceramic elements. Since, the devices have been at the center of growing criticism for failing at unexpectedly high rates and leaving patients with serious, sometimes life-long injuries.

Some experts have accused European and American regulators of ensuring consumers were kept in the dark about the risks associated with metal-on-metal hip implants. Many have criticized device makers for placing profits over patient safety.

The FDA’s recently released guidelines for patients implanted with the devices include that physicians conduct physical examinations, diagnostic imaging, and metal ion testing on symptomatic patients.