One of the marvels of modern medicine is the ability to remove fractured or worn-out joints and replace them with devices meant to reduce or eliminate pain, permit increased mobility, and enhance quality of life. Some replacement systems, however, have been found to cause serious and long-lasting side effects, such as metallosis.
What is metallosis?
Metallosis is a kind of metal poisoning. The biochemical processes of the human body naturally depend on many metals – zinc, iron, copper, and chromium, to name a few. Yet, even these normally benign metals can be toxic if taken in quantity or if they are not passed from the body through elimination. Additionally, metal poisoning can occur when metal-on-metal joint replacements shed metal ions into the nearby soft tissues.
Is this why some joint implants have been recalled?
The Federal Drug Administration (FDA) has recalled the following metal-on-metal (MoM) hip implants:
- Smith & Nephew R3 Metal Liners of the R3 Acetabular System
- DePuy ASR TM XL Acetabular System
- Zimmer Durom® Acetabular Component
The recalls were made because the devices had a high rate of failure, and one cause of the failures was the build-up of cobalt and chromium in the soft tissues surrounding the implant.
What happens when metal levels are high?
When metal ions build up near the replaced joint, it stimulates the lymph nodes and kidneys to try to remove them. When the levels are too high, metallosis develops which can lead to several complications, including implant failure, tissue and bone death, and organ damage. Revision surgery may be necessary.
What are the symptoms of metallosis?
Often there is pain in the replaced joint. If the tissue or bone becomes necrotic (dies), there can be a dislocation or fracture. Sometimes pockets of fluid, called pseudotumors, develop in the area. There may be a clunking noise in the hip. Metal poisoning can enter the bloodstream and affect the nervous system, skin and other organs, causing skin rashes, visual impairment, hearing impairment, confusion, thyroid issues, and heart problems. It has not been proven that metallosis causes cancer; however, the World Health Organization (WHO) International Agency for Research on Cancer lists trivalent chromium and cobalt as potential carcinogens.
Symptoms evolve over several months, usually nine or more months after surgery but less than four years.
How do doctors diagnose metallosis?
Doctors diagnose metallosis by doing a blood test or withdrawing fluid from the joint of a patient who complains of symptoms. They look for elevated levels of cobalt ions in blood, joint fluid, hair and urine. The problem is, in its early stages metallosis can be present without symptoms. The FDA does not have enough information to certify what the safe level of metal ions in blood should be; however, the cobalt level is typically less than 2 micrograms per liter. Some patients with severe metal poisoning from MoM implants had levels as high as 122 micrograms per liter.
Imaging tests like X-rays and magnetic resonance imaging (MRI) may also be used to detect tissue damage.
How is metallosis treated?
It is not possible to remove excess cobalt from the joint or blood. The only proven treatment is surgery to remove the metal implant and replace it with a ceramic-on-metal or plastic-on-metal implant. If the metallosis is severe, the surgery may not go well. Some patients suffer fractures during the revision surgery because their bones have become weak and there has been extensive tissue damage. Recovery can be very difficult.
Are some people more susceptible to metallosis than others?
Yes. The FDA says there is more risk for the following people:
- People with implants on both sides
- Those taking corticosteroids like prednisone
- People who have kidney problems
- Patients who have suppressed immunity
- Those who are highly active
- Overweight patients.
Metallosis is more likely to develop in metal-on-metal hip implants than knee replacements.
What should I do if I have already had an implant?
If you have a metal-on-metal joint, you should see your doctor every one to two years, even if you have no adverse symptoms. He should do a complete physical examination and routine X-ray of the joint. The FDA does not recommend routine blood tests to check metal levels. If you have any symptoms described above, you should immediately see your orthopedic surgeon and primary care physician; they will probably do follow-up exams at least every 6 months.
How do I know if I was given a metal-on-metal hip?
Sometimes at the time of surgery patients are given written documentation which describes the type of device used. Or you can call your orthopedic surgeon and ask for the manufacturer and model of your implant. Dozens of companies manufacture hip replacement systems. These are the manufacturers of the most widely used hip replacement devices in the United States:
- DePuy, a division of Johnson & Johnson
Pinnacle Hip Replacement System
ASR XL Acetabular System (recalled)
ASR Hip Resurfacing System (recalled)
Complete DePuy product list
- Stryker Orthopaedics
ABG II modular-neck hip stems (recalled)
Complete Stryker product list
- Zimmer Holdings
Durom Acetabular Component (Durom Cup)
Continuum Cup, M/L Taper
Complete Zimmer product list
- Smith & Nephew
R3 Acetabular System (recalled)
Complete Smith & Nephew product list
- Biomet Inc.
M2a (M2a-Magnum, M2a-38, M2a-Taper, M2a-28mm, Stanmore and Exceed ABT)
Complete Biomet product list
- Wright Medical Technology Inc.
Conserve Plus Total Resurfacing Hip System
Profemur Z Hip Stem
Complete Wright product list
Is there a legal remedy for the damage done by faulty implant products?
Yes. Patients who have been injured by medical devices can file a lawsuit against the manufacturer, seeking to be compensated for the injuries they have incurred. Monetary damages may be awarded to help patients who were injured by the very medical devices which should have helped them.
The mission of PGMBM is to protect those who are injured by the negligence or misconduct of others – including pharmaceutical companies and manufacturers of medical devices. To read more about our efforts on behalf of hip implant patients. You can contact us online to call 1-888-348-6787 to discuss how we can help you.