House Republicans are being urged by Democrats to investigate the safety of metal-on-metal artificial hips, such as the recalled DePuy Orthopaedics ASR XL systems, and the process by which those devices are approved. The request was made by Energy and Commerce Committee chairman Rep. Henry Waxman of California.
Hip implants are typically made from ceramic or plastic parts. But some newer varieties are constructed with metal-on-metal parts. This design is intended to be more durable and last longer than traditional implants. Instead, they have been found to fail at a higher than expected rate.
Metal-on-metal hip implants involve a metal ball that fits into a metal socket. As the two parts move against each other, bits of metal can flake off into the hip joint, causing inflammation. This can cause pain and limited mobility in the hip joint, but can also cause the implant to fracture, loosen or dislocate, which requires revision surgery to remove and replace the device.
The bits of metal have also been linked to even more problems, including a type of blood poisoning known as metallosis. Metallosis can cause symptoms such as fever, headaches and fatigue, but only time will tell what long-term problems can arise from the blood poisoning.
These problems first came to light last fall after DePuy Orthopaedics, a subsidiary of Johnson & Johnson, recalled its ASR XL hip replacement and hip resurfacing systems following a high number of complaints and failures in just a short amount of time. Upon further review, the FDA identified similar problems with other metal-on-metal hip implants. There are about 20 manufacturers of metal-on-metal devices, and about 500,000 patients have received them. To date, the FDA has received about 5,000 complaints about metal-on-metal artificial hips.
As it turns out, the metal-on-metal hip implants were never put through rigorous clinical trials. Instead, they were approved under an accelerated program that allows medical devices categorized as “moderate risk” to be marketed in the United States if they are similar to other devices that have already been approved for sale. The process was recently criticized by the independent group Institute of Medicine.
The FDA’s report on metal-on-metal hip implants is expected within the next few months.