Metallosis, also known as metal poisoning, occurs when metallic debris accumulates in the body’s soft tissue. Usually, the condition refers to cobalt and chromium particles that absorb into tissue as a result of faulty metal orthopedic implants. High levels of cobalt in the body, also known as cobaltism, can cause damage to the body’s organs. Metal parts from orthopedic devices can shed small metal particles when they grind together. When metallosis occurs, the immune system identifies the metal ions as foreign bodies and aggressively attacks the soft tissue that contains them. Damaged and inflamed tissue can contribute to premature loosening of the orthopedic device. Metallosis can also lead to necrosis, which is characterized by extreme skin rash and death of skin cells.
Symptoms of metallosis
- Joint stiffness
- Lack of range of motion
- Peripheral neuropathy
- Optic nerve atrophy
- Pseudotumors (a group of enlarged cells that resemble a tumor, but which is actually the result of massed fluids)
- Skin rash
- Loosening of a metal orthopedic implant
Treatment for metallosis is the removal of the source of the metal ions. In most cases, this requires revision surgery, or the surgical removal of the metal device that is causing the condition.
DePuy hip metallosis has been known to occur in patients who have received a metal-on-metal DePuy hip replacement system, such as the ASR acetabular hip model, or the metal-on-metal version of the Pinnacle hip model. The DePuy ASR hip was voluntarily pulled from the U.S. market in 2010, due to reports of higher than expected rates of device dislocation, a side effect that could be the result of metallosis.
Zimmer hip metallosis is caused by the chafing of metal ball and socket parts in Zimmer’s metal-on-metal hip replacement systems, such as the Zimmer Durom Cup model artificial hip. Sales of the Durom Cup were voluntarily suspended in 2008 due to higher than expected instances of device failure. Eventually, Zimmer re-issued the Durom Cup hip to the market, blaming instances of device dislocation on inadequate surgical technique, and not on defective design.
Stryker hip metallosis has been linked to the Rejuvenate and Trident devices. Certain metal neck and stem components used with these implants have been reported by some patients to corrode and degrade to the point where tissue damage was sustained. In July 2012, Stryker implemented a voluntary recall of the Rejuvenate and ABG II modular-neck stems from the market. The company announced that the measure was taken “because there is a potential for fretting and corrosion at the modular neck junction which may lead to adverse local tissue reactions.”