Metal on metal hip implants account for approximately one-third of the 250,000 hip implants done in the United States annually. However there is mounting evidence that these implants may be defective, and that these defects may cause a variety of serious problems in patients. Data from joint registries confirms that metal on metal implants are more likely to fail and require a revision surgery than any other bearing interface.
When a metal on metal hip implant is used in a total hip arthroplasty or a hip resurfacing surgery, the acetabular insert, which was typically made with a type of plastic known as ultra high molecular weight polyethylene, is instead made out of cobalt chromium, and articulates against a metal femoral head, which is also made of cobalt chromium.
The problem with this type of interface is multi-factorial. When hip or knee implant components move against each other, the friction causes wear. This happens with any medical device implant, just as it occurs with your god given joints. The body attempts to rid itself of this particulate debris by carrying the particles away in the lymphatic system. However, the wear particles that are produced from a metal on metal implant may be detrimental to patients’ health in a number of ways.
First, these wear particles may trigger the onset of osteolysis, a biological autoimmune response in which the body, thinking that it is being infected, attacks and erodes its own healthy bone. This can lead to pain, swelling, limitation on range of motion, and eventually failure of the implant, which will then need to be revised.
Second, these metal particles can cause metallosis, which is an allergic reaction to the metal debris in the area of the metal on metal implant. This is often characterized by a darkening or discoloration of the surrounding tissues, and in some cases, benign tumors in those tissues. This often leads to complications including degradation of the joint and eventual joint failure.
Finally, while not definitively proven in the medical literature, experts are concerned that this metal debris may affect other organs. International Agency for Research on Cancer (IARC) has listed cobalt and cobalt compounds within group 2B (agents which are possibly carcinogenic to humans). Chromium has also been determined to be hazardous to humans (depending on the amount and method of exposure). Studies are ongoing but some suggest that people with exposures to these metals may suffer chromosomal damage. While it has not been shown definitively that people with metal on metal implants may have a higher rate of cancer, the findings are of concern.
If you or a loved one are suffering from complications of a metal-on-metal implant and would like a free consultation with a hip implant attorney, please contact us immediately.