GAITHERSBURG, MD. – Evaluation of patients for adverse effects associated with a metal-on-metal hip implant should include an expedited physical exam with an orthopedic surgeon, routine x-rays, and both standard and specialized laboratory tests, a Food and Drug Administration advisory panel recommended at the end of a 2-day meeting on June 28.
Lab testing should include the standard blood tests, as well as measures of sedimentation rate and C-reactive protein level, and more sophisticated imaging with MRI or CT, if needed, according to the advisory panel of the FDA’s Orthopaedic and Rehabilitation Devices Panel, which met for 2 days to review the safety data on these devices.
Blood or serum tests for metal ions (cobalt and chromium, which have been elevated in some patients who have received metal-on-metal devices, and have been associated with device failures) also can be helpful, panelists said, although these tests are not universally available and how to use the results in determining the course of treatment is still unclear. They made similar recommendations on how to follow up symptomatic patients who have undergone hip resurfacing with a metal-on-metal device.
There was less consensus on how to follow patients who have received one of these devices but are asymptomatic; recommendations included obtaining a baseline evaluation, with an MRI (at least in patients who are part of a postmarketing study) and tests for metal ions so changes can be monitored and compared over time. One panelist called for longitudinal studies that collect this type of information at baseline, so that predictive factors for failure could be identified.
The panel was not asked to vote on any issues, only to provide advice, so that the agency can make recommendations on the safety of these devices to health care providers and patients. The agency usually follows the recommendations of its advisory panels.
Metal-on-metal hip resurfacing systems, which became popular for use in younger active patients who had healthier bone, include the femoral head with a metal covering, a femoral stem, and an acetabular component. The metal-on metal hip devices were thought to last longer. The proportion of procedures in which devices are used has declined in reaction to increased revision rates and reports of adverse events.
In May 2011, the FDA issued a public health communication regarding adverse event reports associated with these devices and subsequently ordered manufacturers to conduct post-marketing studies addressing the safety issues of their metal-on-metal total hip replacement devices. The FDA has recalled two metal-on-metal devices, including one in August 2010 for a higher than expected revision rate.
A review of metal-on metal implants in December 2011 conducted by the American Academy of Orthopaedic Surgeons concluded that the risk of revision was higher among patients who receive these implants for total hip arthroplasty and hip resurfacing than those who undergo this surgery using a different bearing. The AAOS review also found that larger femoral head components used in hip arthroplasty are associated with higher revision rates, which was also reported by speakers during the FDA panel meeting.
Alerts about local and soft tissue reactions and recommendations on metal ion testing and imaging of patients who have received one of these devices has been issued in the United Kingdom, Australia, and Canada.
When asked if they could describe any types of patients for whom the benefits of a metal-on-metal device for resurfacing or hip replacement outweigh the risks, panelists said that the decision should be up to the individual surgeon and that there might be some cases where this type of device may be useful. But the orthopedic surgeons on the panel said they rarely or never used metal-on metal implants because of these adverse event reports and availability of other options.
"I see no indication for which I would use a metal on metal [device] over any other technology," said the panel chair, Dr. William Rohr, an orthopedic surgeon who practices in Fort Bragg, Calif. He added that he had not seen any evidence indicating that the performance of the metal-on-metal devices was better than that of other options, and he considered any increased risk over the others available unacceptable, and pointed out gender differences, with women at risk of poorer outcomes
Members of FDA panels have been cleared of potential conflicts of interest; in some cases, they are given waivers but not at this meeting.