Monday, March 12, 2012

Reviewing the Safety of Metal-on-Metal Hip Implants

According to a recent BBC Newsnight investigation, literally hundreds upon thousands of patients across the globe may have been exposed to potentially toxic substances following the implantation of metal-on-metal hip implants. Even though it is now believed that the dangers of these hip devices—which appear to have been very poorly regulated at best—was well known and documented for decades, recipients of the devices were nonetheless kept in the dark. The implants which are in question are known as “metal-on-metal,” and are constructed via a head at the top and a lining the head fits into which are made of cobalt-chromium alloy.

The Failure Rate of Metal-on-Metal Hip Implants
These hip implants are used in hip replacements and hip resurfacing, and came into wide-spread use in the 1997. The target group for these metal-on-metal hip replacements was younger, still-active patients who expected the hip replacement to last the rest of their life. Unfortunately, the numbers show that the failure rates among both genders are significantly higher than normal—from 11.8% failure in resurfacing to 13.6% for the total hip replacement as compared to rates of only between 3 and 5% for implants made of other materials.

How Many People Have Hip Implants?
Since 2003, the BBC article reports that over 60,000 patients in England and Wales and over a million in the United States have received the potentially dangerous metal-on-metal hip replacement. The metal ions from the cobalt and chromium hip implants are believed to seep into local tissues causing reactions which can not only destroy muscle and bone but can eventually leave the victim with a permanent disability. The fact that cobalt and chromium can lead to such serious health issues was actually documented in scientific journals over three decades ago.

Was There a Cover-up?
DePuy, a major manufacturer of the metal-on-metal hip implant, released an internal memo in 2005 which stated that in addition to possible changes in immune functioning there was additional concern that the metal debris from the device could be carcinogenic. The memo went on to state that the possibility of distant effects of the device was “worrying,” and that one study indicated a three times higher risk of lymphoma and leukemia ten years following the hip replacement. Despite these very real concerns DePuy continued marketing the device and indicated none of the potential health concerns in their subsequent promotional materials.

A Discussion of the Long-Term Health Effects of the Hip Implant
In 2006 the Medicines and Healthcare Products Regulatory Agency convened a meeting to discuss the long-term health effects of the metal-on-metal hip implant made from cobalt and chromium. An advisory board was appointed, however out of the group’s eight members, two were consultants for DePuy and one was the director of product development for Smith and Nephew—obvious conflicts of interest. In the end the group chose to sidestep the potential dangers of the metal-on-metal hip implants, even refusing to warn women of child-bearing age of the potential dangers despite the fact that metal ions had previously been detected in umbilical cord and placental blood among women with the implant. No alert was put out to either surgeons or patients, and it was not until March of 2011 that the British Orthopedic Association sent out a warning advising that the metal-on-metal hip replacements should be “carefully considered and possibly avoided.”

Excessive Levels of Cobalt Resulting from the Hip Implant
Although there are no current guidelines regarding unacceptable levels of cobalt ions in those receiving implants, a designer and consultant for DePuy theorizes that patients whose device is functioning properly should have cobalt levels of no more than 2 ug/L. Subsequent studies, however, have shown that the cobalt concentrations in the blood of those with a metal-on-metal hip implant have reached over 300 ug/L—approximately 600 times the levels in a person without a cobalt hip replacement device.

Design Changes to the Hip Implant
The BBC reports that the Pinnacle hip replacement device is not the only metal-on-metal implant with potential health hazards in the form of metal ion concentrations. Other implants made by Zimmer, DePuy, and Smith and Nephew have also showed an increase in metal ions in the body. Rather than alerting patients at any time in the past couple of decades regarding the potential hazards of the metal-on-metal implant, the companies “tweaked” the design of their hip implants by shortening the taper which inserts into the head and added grooves to allow surgeons the choice to use them with ceramic or metal heads. Unfortunately, these particular changes, when combined with bigger heads created another issue in the form of increased wear. This increased wear in turn led to higher levels of metal ions in the blood and greater joint failure rates.

The FDA Approval Process
Another internal e-mail among DePuy executives in 2009 discussed concerns by Japanese surgeons who reported observing “generated metal debris between stem taper and head, and final necrosed tissue.” Over five years after the design changes took place DePuy engineers were still struggling to determine why the implants were failing, yet patients had still not been warned of the potential dangers and surgeons were still implanting the devices. The 510(k) FDA approval process in the United States allows many potentially harmful devices to slip through the cracks when they are deemed to be “substantially equivalent,” to a device already on the market. When approved through the 510(k) process, no clinical trials are required. In May of 2011 the FDA invoked a rule which required post-marketing studies in which blood samples would be taken from those implanted with the metal-on-metal hip device to measure the metal ions. The FDA has also prohibited hip implants from being fast-tracked, placing them in a higher risk category.

As stated in the BMJ/BBC Newsnight investigation article by Deborah Cohen, not only have the manufacturers of the hip replacement devices demonstrated a completely inadequate response to the very real potential health hazards, the regulatory bodies have also failed to give doctors and patients the required information to allow them to make a valid decision about their health and their future. If you or a loved one has suffered ill effects from a metal-on-metal hip implant device you should seek legal representation as soon as possible to protect your future rights.

To read more on the safety of metal on metal hip implants, readers are encouraged to read Deborah Cohen’s outstanding and informative article on the subject that was recently published in the BMJ. You can find the article at http://www.bmj.com/content/344/bmj.e1410

Author: Sullo & Sullo Attorneys

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