A new report by U.K. researchers provides further support for the argument that metal-on-metal hip replacements should be recalled from the market, due to the high failure rates and potential side effects of metal poisoning caused by the microscopic shavings of cobalt and chromium released into patients’ bloodstreams.
According to a study published this week by the The Lancet medical journal, researchers from the National Joint Registry of England and Wales looked at the registry’s data on hip replacements and found that all metal-on-metal hip implants seem to fail at a high rate, especially those with larger head sizes.
Researchers concluded that metal-on-metal implants should no longer be used, and indicated that individuals who have received the devices, especially young women implanted with large diameter heads, should be carefully monitored.
The study looked at data on on more than 31,000 metal-on-metal hip implants conducted in the United Kingdom from 2003 through 2011, and found that implants with larger heads and those used in younger women failed at higher rates when compared with others. For example, women who received a metal-on-metal hip implant with a 46 mm head suffered a 6.1% failure rate over a five year period, compared to a 1.6% failure rate for women who received a 28 mm metal-on-polythylene implant.
Concerns over the safety of metal-on-metal hip replacement systems have been growing over the past two years among orthopedic surgeons and health experts in the U.S., U.K. and Australia.
Many of the devices have already been associated with higher-than-expected failure rates, causing individuals to require additional surgery to replace or revise the artificial hip within a few years of the original surgery.
In August 2010, a DePuy ASR metal-on-metal hip recall was issued after it was discovered that about one out of eight implants failed within five years. However, more than 93,000 of the ASR components were implanted worldwide before the recall, with about 40,000 sold in the United States.
Approximately 3,500 individuals throughout the U.S. have already filed a DePuy ASR hip lawsuit against Johnson & Johnson and DePuy, alleging that the company failed to adequately research the design of their implant or warn about the risk of metal-on-metal hip poisoning.
In addition, hundreds of individuals are currently pursuing a DePuy Pinnacle lawsuit, after experiencing problems with the older metal-on-metal hip implant, which has also been linked to a high number of failures.
Similar product liability lawsuits have also been filed over problems with Wright Conserve metal hips, BioMet M2A-Magnum metal hips and other metal-on-metal hip replacements manufactured by other companies.
In the United States, approval for most metal-on-metal hip systems has been obtained through the FDA’s controversial 510(k) fast-track approval system, which allows manufacturers to avoid conducting rigorous pre-market testing if they can establish that the design is substantially equivalent to an existing device.
In May 2011, the FDA asked device manufacturers to obtain more information about the level at which the metal particles shed by hip replacements becomes dangerous, how much metal they actually shed and what the potential side effects of metallosis are.
Several critics have suggested that a metal-on-metal hip recall should be issued to revoke approval for the devices due to the risk of complications. However, many doctors have taken the issue into their own hands by deciding to no longer implant metal-on-metal systems.
Although metal-on-metal hip implants previously accounted for about one-third of all devices used in the United States, due to the belief that the all-metal structure would be more durable, sales have already dropped significantly in recent years.