The failures of metal-on-metal hip implants have created a situation that is nothing short of a health-care catastrophe. For example, products from one company – ASR XL Acetabular System and DePuy ASR Hip Resurfacing System made by DePuy Orthopaedics, Inc. – have experienced an astonishing failure rate: Roughly 1 in 8 of patients with these joints need a second hip operation, called revision surgery.
The DePuy devices were implanted in about 93,000 patients worldwide.
The problems with metal-on-metal (MoM) implants (diagram) can be described as changes in materials that sounded good in theory but in practice developed unexpected dangers.
The theoretical improvements in the MoM implants were that the metal would prove more durable than polyethylene components used in conventional implants. That could make them more suitable for younger and physically active patients. It was also hoped that less total material would scrape off from the ball and socket as the components rubbed together. It was thought as well that there would be less chance of dislocation because the femoral head could be made larger with a MoM implant, and there would be less chance of the device fracturing.
Well, these hoped-for improvements didn’t pan out.
In August 2010, DePuy (a subsidiary of Johnson & Johnson) recalled its ASR hip systems.
According to the DePuy hip recall website, five years after being implanted with the ASR total replacement systems (approved for use in the United States and worldwide), 13 percent of patients had to have revision surgery. The resurfacing system (approved for use outside the U.S.) needed replacing in 12 percent of patients.
A plethora of problems arose with the hip implants, as reported by the Food and Drug Administration. Symptoms may include hip/groin pain, local swelling, numbness or changes in your ability to walk.
Other serious problems the FDA listed:
“Metal-on-metal hip implants, like other types of hip implants, are known to have adverse events including infection and joint dislocation. There are some case reports of the metal particles causing a reaction around the joint, leading to deterioration of the tissue around the joint, loosening of the implant and failure of the device, as well as some of the symptoms described above. In addition, some metal ions from the implant may enter into the bloodstream. There have been a few recent case reports of patients with metal-on-metal hip implants developing a reaction to these ions and experiencing medical problems that might have been related to their implants, including effects on the nervous system, heart and thyroid gland.”
Recently there have been a number of recalls and investigations by the FDA into orthopedic medical devices including the Zimmer Duron Acetabular Component as well as the DePuy devices, and also investigations and into drugs. To learn more, connect to these links:
Recalls (Zimmer components Surgeon Letter)
FDA’s hip joint concerns (MedPage Today report)
Zimmer Nexgen knee replacement (New York Times report)