Metal Hip Replacements: Toxic Effects?

Illness Reports Spur FDA Demand for Safety Studies of Metal-on-Metal Hip Replacements

By Daniel J. DeNoon
WebMD Health News

Reviewed by Louise Chang, MD

May 13, 2011 - Can metal-on-metal hip replacements make people sick by releasing metal ions into the bloodstream?

The FDA wants to know -- and is ordering the 21 makers of these devices to come up with answers.

"The FDA is aware of public health questions regarding the safety of metal-on-metal (MoM) total hip replacement (THR) systems," FDA public information officer Amanda Sena tells WebMD in an email exchange.

The most disturbing of these questions concern reports of "a small number of patients who may have developed symptoms or illnesses elsewhere in the body (systemic effects), including effects on heart, nervous system, and thyroid gland," according to Sena.

The worry is that the metal-on-metal contacts in the hip replacements grind off tiny metal molecules -- chromium and cobalt ions -- that might be toxic. Or not: There's not enough information to prove that the metal ions actually cause the adverse events that have been reported.

Moreover, some tiny metal particles may wear off the devices and enter the space around the implant, causing local damage.

When installing the implants, surgeons take particular care to make sure the metal ball and socket create as little friction as possible. But there's no way to completely avoid the devices from producing metallic debris, the FDA says.

And the devices may also loosen or develop other problems, causing pain and affecting a person's ability to walk.

Metal-on-metal hip replacement manufacturers have until June 5 to come up with a plan for safety studies. These studies must:

• Collect information on adverse events -- and the rates and time since implant at which they happen -- for each device.
• Collect data on levels of chromium and cobalt in patients' blood, before and after implantation.
• Report data on patients who have had their hip replacements removed or replaced, and compare this data to patients who have not had their implants removed.
• Report why removed devices failed.
• Report demographic variables that may be linked to adverse reactions to metal ions.
• Evaluate cardiac, neurological, immunosuppressive, allergic, and pain symptoms.
• Submit imaging data to show whether there are issues with the device or with the bone and tissues around the device.

Advice for Patients With Metal-on-Metal Implants

People who have a metal-on-metal hip replacement system -- and who are not having problems -- should continue with their regularly scheduled visits to their orthopaedic surgeon.

Anyone experiencing any new or worsening symptom three months or more after receiving a metal-on-metal implant should consult their orthopaedic surgeon immediately.

"Common symptoms may include pain, swelling, numbness, and/or change in ability to walk," the FDA's Sena says.

People with these implants should make sure their primary care doctor knows they have one and should remind their doctor about their implant if they have any new symptoms or medical conditions.

The FDA also encourages patients to participate in the new safety studies, whether or not they are having a problem with the devices. Patients may be contacted about the studies by the manufacturer of their device or by their orthopedic surgeon.

Patients may also look for studies at the FDA's post-market surveillance study web site.

Here's the list of manufacturers whose metal-on-metal hip replacement systems are included in the FDA action:

• Biomet
• Encore Medical
• Johnson & Johnson
• Stryker Howmedica Osteonics
• Wright Medical Technology
• Zimmer
• Link America Inc.
• Orthopedic Manufacturing Co.
• Advanced Bioresearch Association
• American Ortomed Corp.
• C.R. Bard Inc.
• Downs Surgical Ltd.
• Endomedics Inc.
• Implantology Corp.
• Joint Medical Products Corp.
• Med-Tek Corp./Synergy Orthopaedics Intl. Inc.
• Orthopaedic Device Corp.
• Osteo Technology, Inc.
• Pfizer Inc.
• Techmedic Inc.
• Turnkey Intergration USA Inc.

SOURCES: FDA letter to MoM THR system manufacturers, May 6, 2011.Amanda Sena, public relations officer, FDA, email exchange.FDA web site. ©2011 WebMD, LLC. All Rights Reserved.