Metal-on-Metal Hip Implant Overview
A metal-on-metal hip implant replaces the body’s own ball and socket in the hip joint with artificial components, both of which are made of metal. Oftentimes, one component consists of a titanium alloy that rubs against another component that consists of cobalt and chromium.
Patients who have trouble walking because of pain or stiffness due to hip deterioration often turn to hip replacement surgery when physical therapy or other non-invasive measures fail to provide relief. According to the U.S. Food and Drug Administration (FDA), patients who received hip replacement surgery before May 18, 2016 may have received a metal-on-metal system, some of which have been recalled due to the risks of early implant failure and debilitating complications.
Metal-on-Metal Hip Implant Systems Shed Metal Debris
Metal-on-metal hip replacement systems were created because surgeons thought the metal materials would offer better wear and longer life than plastic or ceramic materials.
Unfortunately, metal-on-metal systems have their own risks that include wear of the components that produce tiny bits of metallic debris that becomes embedded in nearby tissue. As the body tries to rid itself of the small metal invaders, fluid may build up and create a pseudotumor, which causes pressure and pain around the joint.
Metal Ions Pose Additional Dangers
Metal ions also may be released from the metal debris and enter the bloodstream. A blood test may reveal elevated levels of chromium or cobalt as a result of the ions leaching into the bloodstream.
According to the U.S. National Library of Medicine, National Institutes of Health, any type of metal implanted into a live body is apt to corrode to a certain extent based upon the metals used. Corrosion is an electrochemical process, which means metal ions are emitted from the metal. Each individual’s local tissue and immune system may react differently.
According to the Arthritis Foundation, in an article published in the medical journal Biomaterials, German researchers found the body’s reaction to metal debris might impair the body’s ability to form new bone. Researchers looked at the lab results of 18 patients who had to undergo hip revision surgery because their metal-on-metal implants failed.
They found that stem cells that were supposed to turn into bone cells lost their ability to do so in the bone marrow that was adversely affected by metal ions. The inability to grow new bone could cause the early loosening of these hip implants.
Side Effects of Metal-on-Metal Implants
Patients have reported a variety of complications linked to metal-on-metal hip implants. High amounts of metal that leach into the blood can lead to an increased risk of cancer, degenerative heart disease, metal poisoning and tissue death of the soft tissues that surround the implant.
Patients in the U.S. no longer receive metal-on-metal hip replacements, but they can receive hip resurfacing, which involves reshaping the head of the thigh bone and capping it with a metal covering.
Among the metal-on-metal hip replacement systems that have had high failure rates are those manufactured by DePuy, Zimmer, Johnson & Johnson, Stryker, Biomet, Wright Medical Technology and others.