Metal-on-Metal Hip Implants Tied to Metallosis?

Corrosion, serious tissue reactions and metallosis are all possible side effects for recipients of the metal-on-metal hip implant. The safety of these devices has come under serious question with many recipients requiring revision surgery to remove the harmful devices. The DePuy ASR was recalled in 2010 due to studies showing it corroded much more quickly than other types of implants, most notably those made of ceramic and plastic. Once corrosion occurs in the metal hip implant the tissues surrounding the implant can become inflamed or soft tissue masses, lesions and necrosis can occur. The femoral heads as well as the acetabular cup of the DePuy hip implants are constructed of cobalt and chromium. The past few years have seen serious concerns regarding the metal chromium and cobalt particles which shave off when the femoral head and acetabular cup rub against one another during any activity. Once the levels of corrosion reach the unsafe stage the implant will likely have to be removed during a revision surgery.

Journal of Anthroplasty Study

A recent study in the Anthroplasty Journal compared the levels of corrosion on the femoral heads of the metal hip implants with those constructed of metal-on-polyethylene which implements a synthetic liner between the metal cup and femoral head. This liner acts as a buffer between the two metal pieces meaning there is less chance of the small metal ions slivering off and causing metallosis or metal toxicity in the bloodstream. The metal ions in the bloodstream can lead to kidney and liver disease or certain types of cancer, while the metal shards which lodge in surrounding tissues can lead to serious inflammation, tumors and even bone loss.

The study findings showed the metal-on-metal implants had significantly higher corrosion levels, increasing over time. More specifically, nineteen of the thirty-three femoral heads removed from patients were metal-on-metal, and almost half of those showed corrosion outside the taper zone. Of the fourteen femoral heads constructed of metal-on-polyethylene only one showed any level of corrosion at all. These levels of corrosion were in turn tied to higher numbers of adverse tissue reactions among the recipients of the metal-on-metal hip implant leading to necessary revision surgeries.

Recall of the Metal Hip Implant

Although the DePuy ASR was recalled in 2010, other metal-on-metal hip implants remain in use, causing medical experts to call for the complete removal of these unsafe medical devices from the market. An upcoming meeting in June of the FDA’s orthopedic advisory board will respond to consumer and physician concerns regarding the metal implants and review the failure rates associated with these implants. The board will likely also discuss the relative patient risk, the potential complications, and the procedure for metallosis testing and implant imaging. At a minimum the board may demand a more rigorous testing procedure for the metal-on-metal devices based on the data indicating that as many as one out of eight implants could fail within five years of the surgery. Over 6,000 patients have already pursued product liability claims against several manufacturers of the metal-on-metal hip implant devices with more expected to follow.