Metal Hip Replacements: Toxic Effects?
Illness Reports Spur FDA Demand for Safety Studies of Metal-on-Metal Hip Replacements
WebMD News Archive
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.