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In this Wednesday, March 5, 2014 photo, Dr. Joshua Jacobs, orthopedics surgery chief at Rush University Medical Center and president of the American Academy of Orthopaedic Surgeons in Chicago, holds a model of a cementless hip replacement. About two of every 100 Americans now has an artificial joint, doctors are reporting. That's 2.5 million with a new hip and 4.7 million with a new knee, according to the first major study to look at how common these operations have become. Results were reported Tuesday, March 11, 2014 at an American Academy of Orthopaedic Surgeons conference in New Orleans. (AP Photo/M. Spencer Green)

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