NEWARK, N.J. - Five makers of medical device implants have reached a US$310 million agreement to resolve concerns over doctor kickbacks, U.S. prosecutors said Thursday. The agreements were made by Biomet Orthopedics Inc., DePuy Orthopaedics Inc., Smith & Nephew Inc., Stryker Corp., and Zimmer Holdings Inc. The five companies account for almost 95 per cent of the market in hip and knee implants. Four will pay a total of $310 million; all agreed to be monitored. The amounts were based on market share. "This investigation uncovered evidence that health care decisions were being made based on a doctor's wallet and not on a patient's well-being," said Weysan Dun, the agent in charge of the FBI's New Jersey division. Authorities said the companies paid orthopedic surgeons exorbitant amounts of money to be consultants and exclusively use their products. Patients and hospitals were not told of the relationships, U.S. Attorney Christopher Christie said.