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US FDA issues metal-on-metal hip safety update, proposes tougher approval process
The U.S. Food and Drug Administration recently updated its safety communications page for metal-on-metal hip arthroplasty implants and issued a proposed order that requires manufacturers of these systems to submit premarket approval applications.
Metal-on-metal (MoM) prostheses were originally evaluated in the United States under the 510(k) premarket notification program and designated as class III devices.
The U.S. Food and Drug Administration (FDA) web page was updated Jan. 17 with information that guides U.S. orthopaedic surgeons on patient selection and consideration of alternative hip systems. It also discussed how to educate patients about the risks of MoM hip implants and their revision and recommends that surgeons specifically monitor patients for adverse events following hip arthroplasty with these devices.
According to the communication, these recommendations were based on evaluating the risks and benefits of the implants and the literature on these devices, as well as results of the June 2012 FDA Orthopaedic and Rehabilitation Devices Advisory Panel meeting.
According to the FDA safety communication, the following individuals are most at risk for events such as device wear, loosening and adverse local tissue damage:
- patients with bilateral implants;
- patients with resurfacing systems with small femoral heads (44 mm or smaller); female patients;
- patients receiving high doses of corticosteroids;
- patients with evidence of renal insufficiency;
- patients with suppressed immune systems;
- patients with suboptimal alignment of device components;
- patients with suspected metal sensitivity (such as cobalt, chromium or nickel);
- patients who are severely overweight; and
- patients with high levels of physical activity.
“Presently, the FDA does not have enough scientific data to specify the concentration of metal ions in a patient’s body or blood necessary to produce adverse systemic effects,” the FDA wrote in the safety update. “In addition, the reaction seems to be specific to individual patients, with different patients having different reactions to the metal wear particles.”
The FDA stated there is no clear need for physicians to check metal ion levels in asymptomatic patients deemed to have properly functioning hips. But they did recommend the use of additional diagnostic imaging and seeking specialized radiology expertise to assess and diagnose soft tissue surrounding the implants in symptomatic patients.
For patients with MoM implants who are symptomatic, the FDA recommends an evaluation be performed every 6 months. All other patients should be evaluated every 1 year to 2 years, based on information in the communication. – by Jeff Craven
- References:
- www.fda.gov/MedicalDevices/Safety/AlertsandNotices/ucm335775.htm
- http://s3.amazonaws.com/public-inspection.federalregister.gov/2013-01006.pdf
Perspective
Back to TopFollowing the U.S. Food and Drug Administration (FDA) update from Jan. 17, 2013 on metal-on-metal (MoM) hip implants, a discussion has already taken place throughout Europe on its content and recommendations. Most European orthopaedic surgeons comment that the update’s impact on clinicians in Europe can be summarized as “too late and too little.”
Very few MoM hips are implanted today in Europe following the intense debate on its risks, and most surgeons who earlier implanted MoM hip prostheses have totally stopped this practice. Nations like Holland and Denmark have recommended a complete time-out for using these implants until we have comprehensive and reliable data to make a final conclusion on their risks and benefits. This makes sense because there are still several other implants and bearing options besides MoM that are available and offer good results.
In my opinion, the health authorities should lead the way and ban the use of MoM hip implants temporarily until the data are clear about the prostheses’ risks and benefits. Therefore, I too feel that the FDA update lacks the solid direction orthopaedic surgeons need at this time.
Perspective
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Overall, from the U.K. perspective, metal-on-metal (MoM) has been a problem. [For] most surgeons in the United Kingdom, our usage of MoM hip replacements has dwindled to almost nothing because we cannot find any advantage. The patients do not do any better in terms of function. There is some evidence the patients’ reported pain levels are higher anyway and the revision rate is higher, so it is not adding much value.
In terms of MoM, we [Medicines and Healthcare products Regulatory Agency] have gone a little bit further than the FDA because we also recommend having a metal ion level test. It is hard to find a metal ion level where you can say whether patients are likely to run into problems, but one of the reasons we chose to go down that route was that the medical literature is not absolutely clear on whether aseptic lymphocytic vasculitis associated lesion reaction is a hypersensitivity reaction or just a reaction to high metal ion levels. Most patients will have a reaction if the level is quite high. We chose this level of 7 parts per billion (ppb) for both cobalt and chrome. If you have a level of 7 ppb or above, chances are a fair number of people so far that have problems have levels of that or above that. That is the sort of level where you start to feel more worried. If it is below 7 ppb, what we have discovered is that low levels are rarely associated with a problem, especially levels below 3 ppb.
The difficulty is, the patients who are anxious seem to develop some of the symptoms that are put down as being due to high metal levels. They do not feel right; maybe their eyes are not good; there is a buzzing in their ears, and it is difficult to reassure that sort of patient. We have gone a little bit further to suggest that there may be a place for doing a metal ion level test. Not that that metal ion level means you should revise at a particular level, but at a low level we feel we can reassure a patient; and at a higher level, we think that can be a sign that things might be going the wrong way.