FDA to Hold Hearing on Metal-on-Metal Hip Replacements

Mark Crane

March 29, 2012

March 29, 2012 — Amid growing concerns about failure rates and safety issues associated with metal-on-metal (MoM) total hip replacement systems, the US Food and Drug Administration (FDA) announced today that an expert advisory panel will meet in late June to provide advice about the risks and benefits of the devices.

The FDA said it is seeking expert scientific and clinical input about the systems, as well as potential patient and practitioner recommendations about the management of patients implanted with such devices. The 2-day meeting will be held on June 27 and 28.

The agency is currently considering whether to make MoM hip implants subject to more rigorous testing and premarket review requirements, the FDA said in a statement.

In May 2011, the FDA issued an order for manufacturers of MoM hip systems to conduct postmarketing surveillance studies to collect more safety data on these devices, including data related to metal ion concentrations in the bloodstream. The action came 9 months after manufacturer DePuy had voluntarily recalled its ASR MoM hip-replacement technology after learning that the 5-year rate of revision surgery for patients in England and Wales was roughly 1 in 8.

A recent study published in the Lancet noting an increased failure rate related to those systems that use large-diameter femoral heads has added to the agency's existing concerns about the safety of MoM hip systems, the statement said. That study found that MoM hip replacement implants fail at a higher rate within 5 years than implants made of other materials. In addition, people with existing MoM implants should have clinical and radiologic exams at least annually, the report recommends.

According to an accompanying commentary by Art Sedrakyan, MD, PhD, from Weill Cornell Medical College in New York City, "We are left with more than 500,000 patients with metal-on-metal prostheses in the USA and more than 40,000 in the UK who are at elevated risk of device failure, which will inevitably result in the burden of further surgical treatments as well as billions of dollars in costs to taxpayers."

The Lancet authors also noted that physicians should consider potential toxicity to bodily organs before recommending an MoM implant. Strong evidence exists now that cobalt and chrome can cause genetic damage, they add.

Another article published in the BMJ last month charged that hundreds of thousands of patients with MoM implants may have been unwittingly exposed to toxic substances. The health risk arises from implants in which the pelvic cup and the femoral head are both made with a cobalt–chrome alloy, as opposed to other materials such as ceramic or polyethylene. The wear and tear of MoM releases metal ions that can seep into local tissue, destroy muscle and bone, and leave patients with long-term disabilities, the author write.

These metal ions, which may be carcinogenic, also can become blood-borne and spread to the lymph nodes, spleen, liver, and kidneys.

There are 2 categories of these MoM systems:

  • MoM total hip replacement systems consisting of a metal ball (femoral head), a metal femoral stem in the thighbone, and a metal cup in the hip bone (acetabular component); and

  • MoM hip resurfacing systems consisting of a trimmed femoral head capped with a metal covering and a metal cup in the hip bone (acetabular component).

Hip replacement surgery is intended to provide increased patient mobility and reduce pain by replacing the damaged hip joint in patients in whom there is evidence of sufficient sound bone to seat and support the components, the FDA said.

"We are asking outside scientific and medical experts to discuss recent information on these devices so that the agency can continue to make reliable safety recommendations to patients and their health care providers," William Maisel, MD, MPH, deputy director of science at the FDA's Center for Devices and Radiological Health, said in an FDA news release.

The expert panel will discuss failure rates and modes, metal ion testing, imaging methods, local and systemic complications, patient risk factors, and considerations for follow-up after surgery.

There are currently 4 device options for hip replacement in the United States:

  • metal-on-polyethylene, in which the ball is made of metal and the socket is made of plastic (polyethylene) or has a plastic lining;

  • ceramic-on-polyethylene, in which the ball is made of ceramic and the socket is made of plastic (polyethylene) or has a plastic lining;

  • MoM, in which the ball and socket are both made of metal; and

  • ceramic-on-ceramic, in which the ball is made of ceramic and the socket has a ceramic lining.


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