WASHINGTON, June 27: As concerns mount over the safety of metal-on-metal hip implants, health regulators are seeking advice on how best to minimize risks for the more than 500,000 patients who have received the devices. All-metal artificial hips were developed to be more durable than traditional implants, which combine a ceramic or metal ball with a plastic socket. Johnson & Johnson is the biggest manufacturer of the all-metal devices, and other device makers include Zimmer Holdings Inc and Wright Medical Group. (agencies)