Most all metal implants are constructed of cobalt and chromium, although many have a titanium stem (another potential problem regarding mismatched metals). Patients with particular sensitivities to cobalt and chromium may experience significant adverse health effects at relatively low levels of metal exposure while others may have dangerously high levels of cobalt and chromium, yet remain asymptomatic. While cobalt and chromium toxicity have many of the same symptoms, there are important differences as well.
Chromium Poisoning
Chromium has been used for literally thousands of years, prized for its resistance to corrosion and superior strength. Chromium VI can be found in stainless steel, automotive parts and medical implants. Chromium III is used as a dietary supplement in extremely minute amounts.
In some cases, symptoms of chromium poisoning can appear as soon as three months following implantation of a metal-on-metal hip device. When tiny chromium ions enter the bloodstream, they are sent to the liver and kidneys where the body will do its best to excrete the toxic metal. An oxidative reaction can occur when the chromium particles reach these two organs, impairing their ability to purify the blood as intended. Although cobalt poisoning tends to get the greater amount of attention, chromium poisoning can be equally dangerous, with following symptoms:
· The inability of the body to repair DNA
· Inflammation and hypersensitivity
· Liver necrosis when high levels of chromium are present
· Impairment of kidney function
· Respiratory issues including shortness of breath and asthma
· Hearing loss and vision impairment
· Sperm abnormalities, decreased sperm
· The formation of soft tissue nodules and necrosis
· Short-term nerve impairment
· Severe dermatitis and other skin conditions
· An increased risk of developing certain cancers.
Both cobalt and chromium can be retained in the body tissues for long periods of time; excess levels of either metal make it more difficult for the body to rid itself of the metals. Because chromium poisoning can cause kidney damage, it can be even more difficult for the body to excrete the chromium resulting from a metal-on-metal hip implant.
Cobalt Poisoning
Cobalt is a metal found in trace amounts in the human diet, particularly in drinking water as well as certain fish and vegetables. These minute amounts of cobalt are essential in transporting oxygen in the body, and regarding the body’s overall metabolism, as cobalt is a critical component of vitamin B12. Cobalt is used in the sterilization of medicine and foods, and can give glass a beautiful deep blue color. Many industrial processes utilize cobalt compounds; cobalt dust can be inhaled through the lungs from the cobalt oxide found in welding fumes. Cobalt is ingested, inhaled, or—in the case of metal hip implants—builds up from the metal ions which shear away from the device.
Following a single dose of cobalt—through ingestion or inhalation—the high blood and serum levels of cobalt will rapidly decrease within 24 hours as the liver and kidneys work to eliminate the metal through urinary excretion. Studies show that in the case of a single dose of cobalt, approximately 40% is eliminated within 24 hours and 70% after one week. However, testing done a full year later showed that at least 10% of the cobalt still remained in the body. Chronic exposure—such as that seen in those with metal-on-metal hip implants—can lead to significant damage to the body. Some of the symptoms associated with cobalt poisoning from an all-metal hip implant include:
· Hypothyroidism (considered by some experts to be the most sensitive indicator of cobalt toxicity)
· Cardiovascular issues such as fatal cardiomyopathy and myocardial injury as well as changes in echocardiogram readings
· Neurological issues including hearing loss, tinnitus, atrophy of the optic nerves, visual impairment, vertigo, chronic headaches, decline of cognitive functions, depression, anxiety and irritability
· Fatigue and poor concentration
· Renal Failure
· Changes to nails and skin, including rashes
· Muscle atrophy
· Seizures, convulsions and tremors
· An increase in certain cancers
· Reproductive disorders
· Changes to DNA
· The development of pseudo-tumors
Since 2006, there have been increasing reports of patients with all-metal hips who have developed athroprosthetic cobaltism. While the patients presented with hearing or vision impairment, cognitive decline, severe headaches, convulsions, extreme fatigue, heart failure or hypothyroidism, without exception all the patients experienced hip pain and had serum cobalt concentrations greater than 60 µg/L. “Normal” levels of cobalt in the human body are below 1.0, and anything above 5.0 is generally considered toxic.
A report in Aviation, Space and Environmental Medicine6 followed aviators who were implanted with all-metal hip devices and later developed serious health issues. The U.S. Air Force granted at least 20 waivers for aviators who had undergone hip replacement surgery through 2007. When those aviators began experiencing issues such as tinnitus, vertigo, visual impairment, muscle atrophy, weight loss, irritability, fatigue and heart failure, they were tested and found to have a high rate, as a group, of athroprosthetic cobaltism. Considering that aviators are generally younger and in better health than the typical hip implant recipient, the study concluded that the population-at-large is at a significant risk of heavy metal poisoning from metal-on-metal hip implants. The authors noted that “ …the insidious nature of arthroprosthetic cobaltism, with its non-specific symptoms and its ability to masquerade as simple hypertension or simply hypothyroidism or simple tinnitus, all but guarantees that cases will be diagnosed late, unless suspicion is always maintained at a high level.”6
Further, the authors believe that all those with a metal-on-metal hip implant should have at least annual measurement of serum cobalt and chromium levels along with regular, extensive scrutiny of hip functions. Since there is really no “treatment” for high levels of cobalt in the body, the source of the cobalt exposure must be removed (the cobalt and chromium hip implant device). The main objective of any treatment would be to eliminate exposure to cobalt, then treat symptoms supportively (thyroid replacement therapy, beta-blockers, corticosteroid steroid therapy, etc.) Just as with chromium excretion, normal renal function is necessary in order to excrete the excess cobalt created by a metal-on-metal hip implant.