Variety Of Metal On Metal Hip Replacements
A study to be presented at the British Hip Society conference in March 2012 links faulty metal-on-metal hip replacement systems to possible kidney cancer and bladder cancer, the United Kingdom’s The Telegraph reports.
The findings suggest that the metal shavings made up of cobalt and chromium — produced when parts grind against each other — cause changes to cells that could be precursors to cancer in 20 percent of patients with all-metal hip-replacement systems. In addition, the metal particles have been blamed for tissue damage, tumors, high metal ion blood counts and metal blood poisoning.
Dangers from Metal Debris
According to The Telegraph, the study was launched after a U.K. regulatory agency in April 2010 warned residents with all-metal devices to undergo annual checks, including scans and blood tests, if doctors suspect their hip implants are shedding metal debris. Signs of potential complications are pain in the groin, hip or leg; swelling at or near the hip joint; and a limp or change in walking ability.
The study was conducted by researchers at the University of Bristol and involved 72 patients. Of the subjects, 17 were found to have genetic damage to the bladder and three already had cancer.
The U.K.’s Medicines and Healthcare products Regulatory Agency (MHRA) has said there is no evidence yet of an increased risk of cancer in patients who receive metal-on-metal devices.
However, metallosis — the build-up of metallic debris in the soft tissues of the body — has long been questioned, and not just in the U.K. In May 2011, the FDA directed 21 makers of all-metal hip implants to conduct post-market studies of their products to determine if they were shedding dangerous amounts of metal. It could take up to a year before the FDA gets the results.
Some Implants Require Revision Surgery
The Telegraph also reported that because of the soft-tissue damage resulting from metallosis, revision surgery for patients whose metal-on-metal hip implants have failed can be complicated. Several types of hip replacement devices have been taken off the market because equipment that was intended to last about 15 years was loosening and wearing out within a few short years, forcing patients to undergo a second, corrective surgery.
In August 2010, DePuy Orthopaedics recalled 93,000 ASR metal hip implants, which included its ASR XL Acetabular System total hip replacement and ASR Hip Resurfacing System. Previously, in 2008, Zimmer Holdings recalled its Durom Cup for similar problems. Thousands of patients have sued over the faulty devices, which they say the manufacturers knew were not functioning correctly.