Metallosis is metal poisoning of the tissues, blood and bone. In most cases, such extreme levels of metal come from the degradation of metal-on-metal hip implant systems.
According to the U.S. Food and Drug Administration (FDA), any artificial hip implant carries risks of wear, but metal-on-metal hip implants cause the additional concern of metal poisoning. Many metal components are made of chromium and cobalt.
The metal ball and metal cup that slide against each other during movement can cause wear of both components. Over time, tiny metal particles shed from the parts and begin to collect in the area surrounding the implant. Some of the metal ions may enter the bloodstream. A metal ion is a microscopic atom compound of the metal that carries an electrical charge.
Symptoms of Metallosis
Different patients will experience different symptoms of metallosis. The most common reaction is tissue and bone death in the area directly next to the implant components that are shedding metal. The bone and tissue literally dies, a process known as necrosis. Dead tissue and bone cannot support the movement of the metal components, which may dislocate or result in a bone fracture.
Pseudotumors may develop around the tissue that contains metal particles. As the body tries to flush the particles away, serous fluid may collect and form tumor-like bulges under the skin. This fluid might become infected if it stays static for too long, but the lymphatic system usually tries to flush the metal ions out of the body through the kidneys so the metal can escape the system through urine. However, the kidneys can take only so much metal.
Dangers of Metallosis
Metal poisoning can affect nearly every system and organ in the body because the metal ions circulate through the bloodstream. Among the advanced issues associated with metal poisoning are:
- Cardiomyopathy, which means the heart enlarges and has trouble pumping blood
- Vision problems, including blindness
- Deafness
- Thickening of the blood, causing circulation issues
- Nervous system problems
- Thyroid problems
- Tinnitus, which is ringing or buzzing in the ears
- Psychological disturbances, such as anxiety or depression
- Cognitive issues, including forgetfulness
- Skin rash
If the implant begins to feel loose or starts making popping or squeaking noises, these may be early signs of metallosis.
Revision Surgery Might be Needed
While some medications might be prescribed to help expel metal ions from the body through the urine, many patients require a hip replacement revision surgery.
In a revision surgery, the problematic metal implants are removed. Scar tissue is removed, too. If the remaining bone has suffered from necrosis, the resulting bone loss will require compensation in the form of bone reconstruction through bone grafts or additional artificial parts to build up the area and prepare it for the new implant system.
Most patients who have suffered from long-term cobalt poisoning will always need medication to deter symptoms.
Metallosis Lawsuits
Many metal-on-metal hip implant systems have faced recalls or been discontinued, like the DePuy ASR hip system, but patients who received a hip replacement before May 18, 2016, may have received a metal-on-metal hip system.
Johnson & Johnson agreed to pay $120 million to settle allegations in 46 states that the company misrepresented the longevity, safety and effectiveness of two metal-on-metal hip implant systems. Other lawsuits have been filed against Johnson & Johnson and other metal hip manufacturers around the world.
