Hip replacement surgery. Image 16 of 30. Saline spray being used to clean a hip during replacement surgery. The metal rod at centre is part of the implant inserted into the femur (upper leg bone). The implant will support a ball (to be added) that will articulate with an implant in the pelvis and form the new hip joint. This surgery is usually performed in response to arthritis, degeneration of the joints, and restores mobility to people who would otherwise be incapacitated by pain and unable to move freely. For a sequence of images showing the full surgery, see M551/340-369. For a sequence showing the operation on the femur, see images M551/344-359.