A total hip replacement is a surgical procedure whereby the diseased cartilage and bone of the hip joint is surgically replaced with artificial materials. The normal hip joint is a ball and socket joint. The socket is a "cup-shaped" component of the pelvis called the acetabulum. The ball is the head of the thighbone (femur). Total hip joint replacement involves surgical removal of the diseased ball and socket and replacing them with a metal (or ceramic) ball and stem inserted into the femur bone and an artificial plastic (or ceramic) cup socket. The metallic artificial ball and stem are referred to as the "femoral prosthesis" and the plastic cup socket is the "acetabular prosthesis." Upon inserting the prosthesis into the central core of the femur, it is fixed with a bony cement called methylmethacrylate. Alternatively, a "cementless" prosthesis is used that has microscopic pores which allow bony ingrowth from the normal femur into the prosthesis stem. This "cementless" hip is felt to have a longer duration and is considered especially for younger patients.