Federal regulators are trying gather additional information about the potential risk of metal poisoning from the metal-on-metal hip replacements, as concerns continue to grow about the high levels of cobalt and chromium that may enter the bloodstream from the artificial hip implants.  

On May 6, the FDA ordered hip implant makers to conduct post market studies to gather data on the levels of metal in the blood of people who have received their hip implants and what health effects those implants might have. The agency sent a total of 145 post market surveillance orders to 21 different manufacturers, including DePuy Orthopaedics, Zimmer and Stryker.