Metallosis is a form of blood poisoning cause by high levels of toxic metals in the blood. Metal-on-metal hip implants create metal particles to be released into the bloodstream and soft tissue around the implant which can lead to metallosis.
Metallosis can cause tissue and bone death, severe pain, and implant failure. When metal particles build up to toxic levels metal poisoning can occur. Metal poisoning can cause tissue loss, loss of cognitive functions, and damage to the nervous system.
Metal poisoning and metallosis are most commonly caused through exposure to heavy metals in the environment. They can also be caused by bad drugs and “natural” remedies. The FDA warns against taking any drug from a questionable pharmacy or of unknown origin.
Medical devices can also cause metal poisoning. Metallosis is a particular kind of metal poisoning cause by joint replacement devices like metal-on-metal hip implants. It can lead to severe complications including implant failure, tissue and bone loss, and even organ failure. Often the treatment for metallosis caused by a metal-on-metal hip implant is a painful revision surgery to replace the offending device and clean the affected area.
Metal-on-metal hip implants like those from Depuy and Stryker use metal components made of cobalt and chromium. The Depuy ASR uses a metal ball and cup, and the Stryker Rejuvenate and ABG II use a metal neck and stem as well. Although the number of cases of metallosis is higher for patients that had hip resurfacing surgery, metallosis can be caused by components used in both hip resurfacing and total hip replacement.
Cobalt and Chromium and Hip Implants
Cobalt and chromium are essential for healthy cell function, and the body stores a certain level of both. However, increased amounts of cobalt and chromium in the blood stream can be toxic and lead to metallosis.
For hip replacement patients, increased levels of cobalt and chromium are caused by metal ions shed from metal implant components rubbing together. The excess metal builds up around the implant and joint. The lymph nodes and surrounding joint fluid attempt to remove the metal particles by absorbing the ions and transporting them through the bloodstream to the kidneys. The metal particles are then expelled from the body through the urine.
In many cases the metal ion buildup becomes too great for the body to handle on its own. Metal particles that can’t be flushed remain in the body causing metallosis and metal poisoning.
Because of their durability and corrosion resistance, cobalt and chromium metal-on-metal hip implants have been used since the 1950s. By the 1970s the first reports of metallosis began to surface. Patients frequently complained of pain and instability in the joint less than a year after surgery. Doctors began to find green and gray tissue around implant sites as well as a paste-like material surrounding the joint. Tests revealed high levels of cobalt in the joint fluid.
For decades, studies have shown that metal-on-metal hip implants released cobalt and chromium ions into the tissue surrounding the devices, as well as into the blood, joint fluid, and urine.
These studies, however, did not keep manufacturers from making metal-on-metal hip implants. Manufacturers claim the metal devices lasted longer. They also claim the newer designs of metal-on-metal implants cut down on the problems seen in older MoM devices. Larger articulation surfaces cut down on dislocation, but these larger surfaces also create more metal debris and have a higher failure rates. Only recently did the information regarding the rise in cases of metallosis, and earlier than expected device failure become widespread. Leading some patients to take legal action against implant manufacturers.
Numerous lawsuits have been filed against implant manufactures including DePuy, Stryker, Smith & Nephew, and Biomet by patients claiming that the hip replacement makers knew about the increased risk of their products and failed to warn the public about the dangers of metal-on-metal hip implants.
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How to Tell if You Have Metallosis
The syptoms of metallosis vary by individuals. Every person reacts differently to the levels of metal fragments and ions in their system. The most common sign of metallosis is necrosis in the tissue and bone, also known as tissue or bone death.
Tissue or bone death presents itself as gray or black tissue around the implant. The necrosis is caused by metal particles, shed from the working components of the device rubbing against one another, depositing themselves in the tissue surrounding the implant. Tissue or bone death cause pain and instability in the joint and can lead to bone loss, dislocation, and fracture.
Ocasscionaly, psuedotumors—non-cancerous pockets of fluid—will form around the affected tissue. The fluid is typically gray, rust, or yellow in color.
Metallosis can have wide ranging effects on other parts of the body as well including the skin, nervous system and other organs and can lead to the following:
- Cardiomyopathy (heart muscle condition), including heart failure
- Visual impairment that may lead to blindness
- Cognitive impairment
- Nerve problems
- Thyroid problems
- Auditory impairment that may lead to deafness
- Skin rashes
- Noise coming from the hip
- Implant loosening
Two patients suffering from metallosis were the subject of a 2010 State of Alaska Epidemiology Bulletin article written by Dr. Stephen S. Tower. The two patients were both healthy 49-year-old men that received metal-on-metal hip implants.
Within a year of receiving the implants, both men suffered from:
|Skin rashes||Poor memory and mental fogginess|
High levels of cobalt in the blood led to these symptoms in both men, despite healthy kidney function. Both men required revision surgery that showed tissue and bone death around the implants.
Studies show that the level of metal ions in the blood determine the severity of metallosis syptoms.
Symptoms of Metallosis Specific to Serum Cobalt Levels from Study Results
|Cobalt level in micrograms per liter of blood (>µg/L)||Possible symptoms|
|1 – 5||Heart and memory problems|
|> 7||Hip pain, tissue necrosis, pseudotumors|
|23||Hip pain, mental problems (concentration, memory), vertigo, some deafness|
|> 66||Blindness, hip pain, deafness, seizures, tremor, heart failure, goiter, rashes, abnormal blood pressure, depression, weakness|
Cancer and Metallosis
While the link between metallosis and cancer has not been proven, cobalt and trivalent chromium are listed as potential carcinogens by the World Health Organization (WHO) International Agency for Research on Cancer. After thousands of device failures, tests conducted by the London Implant Retrieval Centre confirmed that metal-on-metal implant release trivalent chromium ions.
Early stage metallosis can be hard to diagnose because it will often present without symptoms. Patients that complain of symptoms are tested for elevated levels of cobalt in the bloodstream. However, all patients with metal-on-metal hip replacements have elevated levels of cobalt ions in the blood, joint fluid, hair and urine making it even harder to diagnose.
Because there are few studies, the U.S. Food and Drug Administration (FDA) has not given a specific safe level of metal ions in the blood. The normal measurement for cobalt in joint fluid (serum), however, is less than 2 micrograms per liter (µg/L).
The British Medical Journal stated that the Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) limit for cobalt in the blood is 5 µg/L in a 2012 report. Some metal-on-metal hip implant patients had levels above 5 µg/L just a few months after surgery. The patients from Dr. Towers study in the State of Alaska Epidemiology Bulletin had levels at 122 µg/L and 23 µg/L.
Additional techniques for early detection include x-ray and MRI. The New York City Hospital for Special Surgery’s Dr. Hollis believes that using an MRI to detect tissue damage early can minimize complications during revision surgery.
The following types of patients are more at risk of suffering adverse effects from metal ions, according to the FDA:
|Who are female||With bilateral implants|
|With resurfacing systems with small femoral heads (44mm or smaller)||Who receive high doses of corticosteroids|
|With evidence of renal insufficiency||With suppressed immune systems|
|With suboptimal alignment of device components||With suspected metal sensitivity (e.g. cobalt, chromium, nickel)|
|Who are severely overweight||With high levels of physical activity|
Diagnosed with or Suffering Symptoms of Metallosis
Our Patient Care Specialists can help you determine if you are suffering from symptoms of metallosis and help you determine what you may be owed.
How is Metallosis Treated
Outside of revision surgery, few treatments exist for metallosis. Studies have been conducted on chelation therapy, commonly used to treat lead, arsenic, iron and mercury poisoning. Chelating agents bind to metal ions and are used to remove excess metal from the body. They can be given to the patient orally, intravenously, or intramuscularly.
Because cobalt cannot be chelated, this treatment has proven ineffective for treating metallosis. Revision surgery is the only proven treatment.
Early detection is key for a positive surgical outcome. Severe metallosis can cause unfavorable side effects including fractures during surgery and tissue damage leading to a longer and more difficult recovery.
The FDA and Metallosis
Metal-on-metal implants, according to the FDA, pose a higher risk to patients than other hip implants because of the metal ions shed into tissues. The agency warns that these ions can cause implant loosening, pain, illness and other damage to the body.
The FDA recommends that metal-on-metal hip implant patients follow up with their doctor right away if they experience symptoms. It is also recommended for patients presenting with extreme symptoms, to consider revision surgery sooner rather than later to minimize tissue, muscle, and bone damage.
While the FDA does not recommend blood tests to check metal levels routinely, it does encourage metal-on-metal implant patients not experiencing symptoms to visit their doctor every one to two years.
The FDA has recently ordered metal-on-metal hip manufacturers to conduct more studies on product safety and effectiveness while it determines the extent of the damage caused by metal ions.