What is Metallosis?
December 11, 2010
Metallosis occurs when metallic debris builds up in the periprosthetic soft tissues. In the case of the DePuy ASR Acetabular system, the two parts of the hip implant abraded against one another, creating friction and releasing metallic ions of cobalt and chromium into the body.
Those microscopic metal ions cause an autoimmune response. The immune system identifies the metal ions as foreign bodies and automatically inflames the area around the debris. The body is essentially trying to "trap" the foreign particles in the inflamed area so that the metal can't spread to the rest of the body. In the case of the DePuy hip implant, it appears that the immune system sends inflammatory cells to the synovial membrane as well, causing synovitis. Synovitis is generally quite painful, since the membrane is too inflamed to allow the joint to rotate properly.
Metallosis can be complicated by metal sensitivity, which is essentially an allergic reaction to metal. The normal autoimmune response to foreign matter in the body is to inflame the area and attack the foreign cells. When the body is hypersensitive to a particular substance (like metal), the immune system overreacts and multiplies its efforts to eliminate the foreign body. In the process, normal healthy tissue can get caught in the crossfire as the body mounts an ever-growing campaign against the foreign body.
In patients with a DePuy ASR Acetabular System, the immune system is fighting a losing battle, even after its efforts are multiplied through metal sensitivity. Your white blood cells (leukocytes) attack any foreign organism, but they also "tag" and remember the organisms that have attempted to invade before and come up with secretions designed to wipe out those specific invaders.
In the ASR hip implant, the device's friction constantly releases new metal ions into the bloodstream, which means the immune system continually receives a message that its efforts are not enough to eliminate the foreign matter.
A simple analogy for the metallosis is a food allergy, which occurs when the body identifies a food as so dangerous to the body that its autoimmune reaction is exaggerated. Essentially, it identifies the food as a poison and reacts strongly so that the brain will realize the food is dangerous and move the body away from it. In extreme allergies, the body's immune response can be so overly strong that it can actually kill the person.
Generally, this sort of over-reaction occurs if the immune system is completely unfamiliar with a foreign body and can find no parallels with other objects it has encountered in the past. It can also occur if the body is over-subjected to the object; for example, it is possible to give yourself an allergy to just about any food if you consume excess amounts for months at a time.
Symptoms of metallosis generally include pain around the site of the implant, pseudotumors (a mass of inflamed cells that resembles a tumor but is in fact merely collected fluid), and a noticeable rash that indicates dying tissue. The damaged and inflamed tissue can also contribute to loosening the implant or causing dislocation, since the tissue that would normally hold the implant in place is weakened.
Women, the small in stature, and the obese are at greater risk for metallosis because their body structure causes more tension on the implant and contributes to the release of the metal ions into the bloodstream.
If you're concerned that you have an ASR XL Acetabular hip implant and would like to speak to someone about getting compensation for your medical problems now and in the future, please give our offices a call at 800-677-7095 or fill out our online form. We're here to answer any questions you have and advise you of your rights.