Few Patients Should Get Metal-on-Metal Hip Implants, FDA Panel Says

FRIDAY, June 29 (HealthDay News) — A panel of U.S. government
experts said Thursday that metal-on-metal hip implants have little use in
most patients, with evidence mounting that the devices deteriorate sooner
than other implants, shedding particles of metal into the surrounding
joint and bloodstream.

The panel, convened by the U.S. Food and Drug Administration, stopped
short of advocating a ban on the devices, as some experts have done in
Britain, the Associated Press reported.

The panel also recommended that patients who experience any pain or
other symptoms should be evaluated with an X-ray and blood test for levels
of metal. They also noted, however, that current tests still aren’t
accurate in measuring these levels.

Patients with metal-on-metal implants who are not having pain only
require annual X-rays to track the condition of the device, the experts
said.

While thousands of Americans have benefited from hip replacements over
the years, problems with metal-on-metal implants can lead to troubles
requiring surgery to replace defective devices.

Specifically, experts say, tiny fragments of metal can shear off from
these artificial joints, causing chronic pain or infection and raising
levels of metals in the bloodstream. Experts estimate that more than
500,000 Americans have received a metal-on-metal hip joint, mostly between
2003 and 2010.

Worry over the failure rate of the implants, and the speed at which
they were initially approved for the U.S. market, led to the special
two-day advisory panel session that began Wednesday.

Speaking earlier this week, FDA spokeswoman Michelle Bolek acknowledged
that “data from recent studies and from FDA’s own review show some
patients experiencing complications, including the need for additional
surgeries, which could be attributed to metal-on-metal hip implant
devices.”

Since 1999, almost 17,000 problems with these devices have been
reported to the FDA. Of these, more than 12,000 were reported last year
alone.

According to the agency, the problems with metal-on-metal implants are
about the same as those seen with polyethylene and ceramic implants,
except for the specific risks caused by the metal itself.

But others say that when it comes to complications, metal-on-metal
implants are in a class of their own. Writing earlier this month in the
New England Journal of Medicine, Dr. Joshua Rising, of the Pew
Charitable Trusts, and colleagues said that “there is now compelling
evidence that these implants fail at a higher rate than hip prostheses
made of other materials; indeed, one type of metal-on-metal hip has a
failure rate of nearly 50 percent at six years.”

Of the estimated 400,000 hip replacements done in the United States
each year, 27 percent involve metal-on-metal devices, according to the
FDA.

Critics, including an independent panel of experts at the Institute of
Medicine, have noted that metal-on-metal implants may have been approved
too quickly under the FDA’s “fast-track” program for medical devices.

Responding to concerns, in May 2011 the FDA ordered manufacturers to
carry out “post-market” studies, tracking the safety of metal-on-metal hip
implants in recipients. But in the NEJM article, Rising and
colleagues noted that most of these studies have yet to begin and their
first results will take years to arrive.

Metal-on-metal devices have already been recalled twice. In 2008, a
device from manufacturer Zimmer, the Durom Acetabular Component, was
recalled because instructions were not clear.

And in 2010 a device from DePuy Orthopaedics Inc. was recalled because
more patients than expected had to have new surgeries, according to the
FDA.

Earlier this month, a device called the R3 Acetabular System from Smith
Nephew was taken off the market because the company said it was “not
satisfied with the clinical results of this component.”

In Europe these concerns have led to calls to ban metal-on-metal hip
replacement devices. Writing in March in the journal The Lancet,
British researchers concluded that “metal-on-metal stemmed articulations
give poor implant survival compared with other options and should not be
implanted.” Metal-on-metal implants had a five-year failure rate of more
than 6 percent, three times higher that seen with ceramic or plastic
joints.

Mindy Tinsley is a spokeswoman for metal implant maker DePuy
Orthopaedics Inc., which is owned by Johnson Johnson. She said that
“DePuy believes that no single bearing surface meets the needs of all
patients, and metal-on-metal implants provide the potential benefit of
greater function and a lower risk of dislocation for some patients.”

Tinsley also said that all metal-on-metal implants are not alike and
they should not be grouped together if problems arise.

One orthopedic expert agreed. Dr. Joshua Jacobs, first vice president
of the American Academy of Orthopaedic Surgeons, said that “metal-on-metal
devices are not all the same. You have to go down to the individual
product to fully understand the result. When you lump metal-on-metal
together you miss a lot of important differences.”

According to Jacobs, who is chairman of the department of orthopaedic
surgery at Rush University Medical Center in Chicago, the advantages of
metal-on-metal implants are that there is typically less wear on the
joint, leading to less loosening and less bone loss over time.

In addition, he said, metal allows for a thinner, larger socket and
head, which makes it less likely the hip will dislocate after surgery,
which is a common failure of other types of hip replacement.

Still, given the problems with these devices, Jacobs agrees that
patients need to be monitored.

“We are trying to learn the optimal way of monitoring patients with
metal-on-metal implants, so we can understand when it is appropriate to
intervene,” he said. “Right now we are amassing clinical data to
understand that better.”

More information

For more on hip replacement, visit the
American Academy of Orthopaedic Surgeons
.

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