The femoral component of the prosthesis is a part that can fit into the thigh bone. The acetabulum, a cup-shaped depression at the base of the hipbone (into which the ball-shaped head of the femur fits, forming a ball and socket joint), is drilled out and replaced with an artificial socket and the femoral prosthesis is similar in design to the femur with a head, a neck and a femoral component. The prosthesis is made of a metal alloy, usually titanium. Both prosthetic parts are held in place by a porous surface material allowing growth of bone into the prosthesis, or sometimes, by a special glue.