MODEL RELEASED. Testing artificial hip. Researcher using a device to simulate the wear experienced by an artificial hip during use. The ball part of the implant fits into a socket in the pelvis, allowing rotation and movement of the leg. The balls of two implants (white, lower left and lower right) are being rotated in the artificial sockets to see how long they last. A hip replacement generally lasts for 15 years, but new hip designs have not been in use for long enough for figures to be calculated, other than by experiments like these. Photographed at the Rizzoli Institute, Bologna, Italy.