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

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. Read more ....