More Concern about DePuy Metal-on-Metal Implants

London, UKMuch has been written about DePuy Orthopedics and their potential for early failure due to an implied design flaw. Despite the fact that metal-on-metal hip implants are increasing in popularity and designed to last 15 years or so, early failures have prompted a recall of the DePuy hip replacement system known as the ASR cup. Since then there have been troubling allegations the DePuy metal-on-metal implant could be associated with non-cancerous tumors.

That's the situation overseas in the UK at any rate, according a recent report in the Sunday Times of London. The Medicines and Healthcare products Regulatory Agency (MHRA) in Britain announced an official review in April of some 40,000 hip replacements. Following review, it is expected that many implants will be replaced.

The Sunday Times reports that DePuy is one of the manufacturers involved in the potential replacement of hip implants (hip revision surgery) in the UK.

So far, there has been no mention of potential non-cancerous tumor growth associated with defective hip implants in the US, but the UK reports are troubling—especially given the popularity of metal-on-metal implants and their promise of durability. While most implant procedures are carried out on older patients, the Times reports that eight percent of hip replacements involve people under the age of 55.

Doctors are now warning that metal debris originating from the defective implants can cause non-cancerous tumors, severe swelling and sinew damage.

It has been reported that younger women are particularly vulnerable to the effects of metal debris. Those at risk will have blood tests conducted to determine levels of metal compounds in the blood.

Even though it is phasing out the products subject to the safety concerns, DePuy issued an urgent safety notice back in March emphasizing that its products should not be used in "females of childbearing age" and admitting to "higher than expected" rate of implant removals.

The non-cancerous tumor concern goes back to a report released in January 2008—more than two years ago—when a report to the MHRA found "evidence of genetic damage in patients with certain metal hip implants."

A year ago, the Nuffield Orthopedic Centre in Oxford published a study showing that women under 40 were at the highest risk of developing such tumors, associated with "soft tissue destruction." In a group of more than 1,200 patients who had hip resurfacing over an eight-year period, four percent required a further operation because of the reaction, described as "pseudotumours." The Nuffield study said 13 percent of women under 40 required hip revision surgery.

Justin Cobb, professor of orthopedic surgery at Imperial College London, suggested that the problem originated with the alignment of the two halves of the metal-on-metal replacements, adding that such procedures are generally effective. The adverse reaction was identified in only a small number of cases." It's like a Formula One car," he said in statement to the Sunday Times. "If you don't get the wheels perfectly aligned, you will shed them on the first lap."

The patients thought to be affected include those who have undergone full hip replacements involving metal-on-metal implants, or a resurfacing procedure where a metal surface is added to the top of the thigh bone and the hip socket is lined with metal. Following tests, those considered at risk will undergo hip revision surgery.

In 2008, the year of the initial report to the MHRA, there were nearly 65,000 hip replacement operations, of which about 4,500 were full replacements with metal-on-metal implants. About 5,000 patients had metal-on-metal resurfacing operations.

DePuy nonetheless has stood by its product, pronouncing it as safe. "This is not a recall, as data about safety were not the basis for this decision," DePuy said in a statement.