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, experts say. Specifically, experts say, tiny fragments of metal can shear off from these 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, has led to a special two-day session, beginning Wednesday, by experts at the U.S. Food and Drug Administration.
