Artificial Hips: Newer Might Not Be Better

Jury Still Out on Which Implants Are Safest and Most Durable

By Salynn Boyles
WebMD Health News

Reviewed by Laura J. Martin, MD

Nov. 29, 2011 -- Traditional hip implants might be safer and last longer than some new ones, an FDA-funded study finds.

It's among the first studies to compare outcomes in people who got different kinds of artificial hip implants with different materials.

When researchers evaluated total hip-replacement data from studies and national registries, they found no advantage for the newer metal-on-metal or ceramic-on-ceramic devices, compared with traditional metal-on-polyethylene or ceramic-on-polyethylene ones.

The available evidence suggests that traditional hip replacement devices work as well as newer, costlier implants and might last longer than at least some newer artificial hips.

The researchers conclude that manufacturers of the newer implants cannot claim that their devices are better than traditional ones.

But others feel that more research is needed to draw any strong conclusions.

All-Metal Implants Under Fire

More than 270,000 hip replacements are performed in the United States, and that number is projected to double over the next decade.

The surgery is very effective for improving mobility, but many patients need an additional operation within 10 to 15 years to replace worn out, damaged, or displaced parts.

The hope has been that the newer hip replacement devices would last longer than traditional implants.

All-metal implants have been especially popular with orthopedic surgeons in the U.S. since the introduction of a new generation of the devices in the late 1990s, but their use has declined sharply over the past year or so as concerns about their safety and durability have emerged.

Last May, FDA officials expressed concerns that the metal-on-metal implants may make people sick by releasing toxic metal ions into the bloodstream. The agency ordered 21 manufacturers that market the devices to study the issue.

In August, two all-metal implants were voluntarily removed from the market by manufacturer Johnson & Johnson following complaints that the devices failed years earlier than expected in many patients.

And in September, a British hip replacement registry found more widespread evidence of early failure for the metal-on-metal devices.

'Many Metal-on-Metal Implants Working Well'

Joshua J. Jacobs, MD, second vice president of the American Academy of Orthopaedic Surgeons, says while some metal-on-metal hip replacement devices do appear to be prone to early failure, others probably are not.

"As of now, most metal-on-metal devices that have been implanted in the United States are working well," he tells WebMD.

But he adds that people who have them should not ignore pain, swelling, or numbness around the area of the implant.

"It is important to seek the advice of an orthopedic surgeon without delay just in case a problem is brewing," he says.

In the new research review, published online in the journal BMJ, researcher Art Sedrakyan, MD, PhD, of New York's Weill Cornell Medical College and colleagues looked at 18 studies including more than 3,000 patients as well as outcomes from 830,000 hip replacement surgeries reported to various national registries.

Conclusion: 'More Study Needed'

The three largest national surgical registries showed evidence of higher rates of early implant failure associated with metal-on-metal devices, compared to metal-on-polyethylene implants.

One study showed fewer repeat surgeries for device failure for ceramic-on-ceramic implants, but the national registries data did not support this finding.

Sedrakyan tells WebMD that larger studies with longer follow-up times will be needed to determine the differences between the various devices.

Jacobs says the fact that the researchers had to consider all metal-on-metal, ceramic-on-ceramic, and polyethylene-containing devices together limited the findings.

"By necessity, this analysis was done by class, but it is important to recognize that within these broader classes some devices are performing better than others," he says.

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SOURCES: Sedrakyan, A. BMJ, published online Nov. 29, 2011.Kurz, S. The Journal of Bone and Joint Surgery, April 2007.Art Sedrakyan, MD, PhD, associate professor, Weill Cornell Medical College, New York.Joshua J. Jacobs, MD, second vice president, American Academy of Orthopaedic Surgeons, Rosemont; professor and chairman, department of orthopedic surgery, Rush University Medical Center, Chicago.WebMD Health News: "Metal Hip Replacements: Toxic Effects?"

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