Much of the pain and problems behind the DePuy ASR total hip implant were caused by metallosis. But what does that really mean?

By Taylor Lindstrom

Johnson & Johnson has announced that its subsidiary company DePuy issued a voluntarily recall of their ASR hip implant due to a number of patients who required a second hip replacement procedure, called a revision surgery." 

No mention was made of metallosis in the Johnson & Johnson press release. In fact, Johnson & Johnson didn't mention any of the more significant symptoms patients are suffering after receiving a DePuy ASR XL hip implant. They would prefer that the public believed the revision surgery process is simple and fixes the problem of a faulty hip implant with absolutely no long-term effects. 

We're recommending you get a second opinion - and a blood test.

Metal-on-metal hip replacement bearings like the DuPuy ASR XL Acetabular System total hip replacement were originally reintroduced as an alternative to metal-on-plastic or ceramic hip replacement systems. Metal-on-metal implants (for a hip implant, this is a design that involves both a metal ball and a metal socket) have certain advantages over plastic or ceramic when the design is properly engineered. They last longer, have high resistance to wear and tear, and can withstand more vigorous activity, making metal-on-metal the usual choice for surgeons with younger, more active patients who are going to put more strain on their implants.

However, a poorly engineered metal-on-metal hip resurfacing system has considerable complications, many of them more serious than their ceramic or plastic counterparts. 

The Blue Cross Blue Shield Association Technology Evaluation Center report on metal-on-metal total hip resurfacing notes that metal-on-metal systems have risks of elevated heavy metal ion levels, delayed hypersensitivity to metals, and even carcinogenesis - cancer, to the layman.

All hip replacement systems release tiny particles of the implant's material into the body when the two parts of the hip replacement rub against one another. In metal-on-metal implants, a small amount of friction and metallosis is predictable and part of the considered risks when the surgeon recommends a certain type of hip implant. 

However, when the metal parts are improperly made or installed, the friction releases much more metal into the bloodstream, causing serious metallosis and metal poisoning.

Engineers who have examined the DuPuy ASR hip replacement system noted several design flaws that contributed to increased metallosis and metal poisoning in patients. The implant is shallower than most other hip replacement systems, which made it much more challenging to implant than other systems. DePuy was fully aware of this setback; their instructions to the surgeon recommended a much more precise placement than other implants. 

One engineer we consulted with went on to note that the requirements for placement were so specific that only about 3% surgeons would be able to place the hip implant properly. This is not a comment on the surgeon's skill; the engineer was quick to note that the placement demands would be impossible for all but the most skilled and experienced surgeons, and even then the surgeon would have to be fully informed of the importance of precise placement. 

What's more, even with proper placement, the DePuy ASR hip replacement was made with a poorly designed cup and socket that did not fit together properly. If they had, friction would have been minimal and the metallosis risk would have been akin to other metal-on-metal hip implants. That said, a study by The Journal of Bone and Joint Surgery on metal-on-metal hip implants (not specifically DePuy implants) showed that patients had cobalt levels thirty-nine times higher than normal and chromium levels twenty-eight times normal.

Among patients who were experiencing pain with their DePuy ASR XL Acetabular system and took a blood test, we're seeing levels even higher than that. 

These metal particles, or ions, are released enter the bloodstream where they encounter and bond with proteins normally found in the body. The resulting new particles look foreign and activate the body's immune system. White blood cells are dispatched fight the foreign particles, and the white blood cells create antibodies to fight off what the body believes to be an infection. 

The body is really fighting a losing battle against the hip implant itself. The increased friction from the DePuy hip replacement system produces more metal ions with every movement of the hip, the immune system can never fully fight off or cure what it believes to be an infection. As the body tries to clean up the mess made by the hip implant, it can trigger an autoimmune response: the body starts to fight itself.

When the body is trying to fight off the foreign metal ions that have been released into the blood by the metal-on-metal hip replacement, other healthy body tissues can get caught in the crossfire. The soft tissue and bones surrounding the hip implant get infected, which means the blood supply to the bone or tissue is cut off. Without blood, the tissues starve and die, leaving behind black, dead tissue rotting in the body. This condition is called necrosis. 

Studies have shown that people at greater risk for metallosis include women, people of small stature, and the obese. Any of these groups are more likely to get metallosis because more weight is put on the joint, and therefore the two metal surfaces grind together more, releasing more metal particles into the blood. Add in the addition of a poorly engineered hip implant, and the amount of metal being released into the bloodstream becomes catastrophic.

A study done in England tested a group of patients who had received a DuPuy hip replacement and found a high percentage of patients developed metallosis-compared to almost no incidents in a group of patients who received a different brand of implant.

Some studies have further found that the metallosis could be the cause of early onset osteolysis, a process in which the body begins to reabsorb living bone tissue, causing bone deterioration. Osteolysis makes revision surgery nearly inevitable in implants that are designed to grow onto the surrounding bone, such as the ASR XL Acetabular system. With no bone to hold onto, the hip replacement system fails.

The DuPuy modular hip system is made from a chromium- and cobalt-based alloy. According to the International Agency for Research on Cancer (USA), cobalt is considered to be a possible carcinogen in humans. Animal studies have shown that cobalt is a direct cause of cancer when placed under the skin or in the muscle. Chromium has been linked to cancer as well, and there is no proven antidote for chromium poisoning.

In a study of nine patients who had received a DuPuy hip replacement and showed signs of early osteolysis, eight of the nine patients tested positive for a sensitivity to cobalt. In fact, metal sensitivity is twice as likely to be found in anyone with a well-functioning metal implant, and more than six times as common in those with a poorly functioning implant. (Y. Park) 

The metal-on-metal ASR hip replacement system released far more metal into the bloodstream than other implants of its type due to poor design, which means that in addition to a revision surgery, DePuy should also be accountable for the serious complications of metallosis, metal poisoning, metal hypersensitivity, and early-onset osteolysis - as well as increased risk of cancer. 

If you received a DePuy ASR XL Acetabular system, your medical complications far exceed what DePuy has offered to pay for. Before agreeing to their offer of a revision surgery, please contact our offices, and we'll help you understand any legal rights you may have.