When Should Metal-on-Metal Hip Implant Patients Undergo Revision Surgery?

There appears to be little consensus in the medical community regarding the treatment of patients with defective metal-on-metal hip implants. According to a number of presentations made at the American Academy of Orthopedic Surgeons’ (AAOS) annual meeting earlier this month, there are varying opinions among researchers and doctors as to what factors should determine whether or not a patient with an all-metal hip implant needs to undergo painful revision surgery.

Metal-on-metal hip implants have been worrying the medical community since the August 2010 worldwide recall of DePuy Orthopaedics’ ASR Hip Resurfacing System and the DePuy ASR Acetabular System. DePuy, a division of Johnson & Johnson, currently faces more than 5,000 U.S. lawsuits over its defective ASR hip implants who allege the implants failed within a few years of initial surgeries. At last count, another 900 lawsuits were pending in the U.S. over an all-metal version of its Pinnacle hip replacement device, with plaintiffs claiming it is similar in design to the ASR implants and should have been recalled as well.

It is believed that metal-on-metal hip implants can shed dangerous amounts of cobalt and chromium through wear, leading to tissue damage, premature device failure, the need for revision surgery, and even long-term health problems, including heart and nervous system damage. Last May, the U.S. Food & Drug Administration (FDA) directed 21 makers of all-metal hip implants, including DePuy, to conduct post-market studies of their products to determine if they were shedding dangerous amounts of metallic debris in patients.

More bad news about metal-on-metal hip implants could come as soon as next month. Last week, The Sunday Telegraph reported that researchers at Bristol University in the U.K. found that some recipients of the devices had sustained genetic damage to the cells of the bladder, a possible precursor to cancer. Even more disturbing, at least three of the patients studied had developed full-blown cancer. That study has yet to be released, as an analysis of its findings is ongoing. However, researchers hope to officially unveil its findings next month.

Obviously, metal-on-metal hip implants have to be removed if patients exhibit signs of obvious failure, such as chronic pain and difficulty walking. At issue is what should be done if patients experience no discomfort, but test positive for elevated levels of chromium and cobalt in the blood. According to a report from MedPage Today, regulators in the U.K. have advised in 2010 that chromium or cobalt levels of 7 ppb in metal-on metal hip implant patients should at least trigger imaging studies. If those also indicate abnormalities, then revision should be considered. However, the FDA has not made any recommendations about metal ion testing in the U.S.

According the MedPage Today report, a study presented by British researchers at last week’s AAOS conference indicated that serum chromium or cobalt ion levels of 7 ppb should trigger a discussion about immediate revision surgery. But another study presented moments earlier by a U.S. physician found no relationship between ion levels and tissue damage seen in metal-on-metal implant recipients who had revisions. Yet other research found that while removal of metal-on-metal implants leads to swift and steep declines in serum or whole blood ion levels, they often remain abnormally high for years afterward.

Yet another study, conducted by researchers at Imperial College London focused on the presence of pseudotumors, an indicator of serious soft-tissue damage, according to MedPage Today. The study compared ceramic-on-ceramic and metal-on-metal hip implants in patients who had no symptoms, and where problems were not clinically suspected. Despite an apparent absence of problems, MRI scans showed that 16 of 28 metal-on-metal recipients had pseudotumors, versus one of 15 patients with ceramic-on-ceramic implants.

According to MedPage Today, Joshua Jacobs, MD, a prominent researcher with Rush University in Chicago, said during a press briefing said that no single factor should determine whether a given patient should have a metal-on-metal implant removed.

“If a patient is symptomatic, they have a high-risk device, they have high metal ion levels, and maybe on x-ray … they show bone loss or on an MRI scan some soft tissue swelling, a so-called pseudotumor, that’s someone where I think you’d want to consider revision,”

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