Metal-on-Metal Hip Implants: Use With Caution, FDA Says

Disclosures

January 17, 2013

The US Food and Drug Administration (FDA) today issued an extensive set of cautionary guidelines for problematic metal-on-metal (MoM) hip implants that range from selecting the right surgical candidate to determining when to replace the hardware.

In recent years, MoM hip implants have been beset by manufacturer recalls and charges that regulators in Europe and the United States helped keep patients in the dark about the risks of these devices.

Today's guidelines represent an update of FDA safety information and recommendations that reflects the agency's current assessment of MoM hip implants, which includes the evaluation of published studies and the findings of an FDA Orthopedic and Rehabilitation Advisory Panel meeting in June 2012.

The source of the problem with these implants is metal release. That happens in the wear and tear of the implant's metal ball and metal cup sliding against each other. Other parts of the implant where 2 components connect also can release metal.

The tiny metal particles can damage bone and soft tissue surrounding the implant in what is called an "adverse local tissue reaction" (ALTR) or an "adverse reaction to metal debris," according to the FDA. Soft-tissue damage may lead to pain, device loosening and failure, and the need for revision surgery.

In addition, metal ions freed from the implant can enter the bloodstream, travel to other organs, and trigger illness in a systemic reaction. Examples are skin rash, cardiomyopathy, and renal function impairment.

The agency said it lacks the data to specify the concentration of metal ions in a patient's body or blood that would produce adverse systemic effects, noting that different patients have different reactions to implant particles.

Some MoM Hip-Implant Candidates at Higher Risk for Adverse Events

To reduce the risk for adverse events with MoM hip implants, the FDA today said that surgeons should determine whether the risk-benefit profile of using such devices is superior to that for alternatives, such as metal-on-polyethylene, ceramic-on-polyethylene, ceramic-on-ceramic, or ceramic-on-metal. A patient's age, sex, weight, diagnosis, and activity level all come into play, with a higher risk for increased device wear and ALTR for patients:

  • With bilateral implants

  • With resurfacing systems with small femoral heads (44 mm or smaller)

  • Who are female

  • Who are receiving high doses of corticosteroids

  • With evidence of renal insufficiency 

  • With suppressed immune systems 

  • With suboptimal alignment of device components 

  • With suspected metal sensitivity (eg, cobalt, chromium, nickel) 

  • Who are severely overweight 

  • With high levels of physical activity

After surgery, physicians should follow up on asymptomatic patients with physical examinations and routine radiography at least every 1 to 2 years. "If the hip is functioning properly, the FDA does not believe there is a clear need to routinely perform additional soft tissue imaging or assess metal ion levels in the blood."

Patients at risk for increased device wear and ALTR should be followed more closely, and symptomatic patients warrant follow-up at least every 6 months.

The updated FDA guidelines include recommendations for imaging symptomatic patients and testing their metal ion levels. However, the FDA is not recommending that a certain metal-ion level should be the deciding factor for revision surgery or any other intervention. Instead, physicians should take into account the overall clinical scenario, including symptoms, physical findings, and other diagnostic results, as well as increases in metal ions over time.

The agency noted that when patients experience an ALTR, replacing a MoM hip implant "may have a worse prognosis than revision of other types of bearing surfaces." If orthopedic surgeons suspect a patient has developed metal sensitivity, they must take pains to select the materials of the replacement implant, with an eye to avoiding nickel and chromium. Today's FDA guidance refers surgeons to another document on the agency Web site that offers more detailed recommendations on revision surgery.

To report problems with MoM hip implants, contact MedWatch by telephone at 1-800-FDA-1088; by fax at 1-800-FDA-0178; online at https://www.accessdata.fda.gov/scripts/medwatch/medwatch-online.htm; with postage-paid FDA form 3500, available at https://www.fda.gov/MedWatch/getforms.htm; or by mail to MedWatch, 5600 Fishers Lane, Rockville, Maryland 20852-9787.

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