There are several causes for a hip replacement surgery. Osteoarthritis is one of the most common causes of hip degeneration. In this case, the hip joint simply wears out and must be replaced. Avascular necrosis is also a cause for hip joint degeneration. This condition, also known as AVN is an actual collapse of the ball portion of the hip. Other prior hip problems such as fractures or abnormalities in childhood can also lead to the eventual degeneration of a hip over time.
When it has been decided that a hip replacement is necessary, a prosthesis is put inside the body in the place of the hip. This is done through a size-appropriate incision to reach the hip joint. A prosthesis made of two parts -- the acetabular component (the socket), and the femoral component (the ball) -- are stabalized in the bone to form the new joint.
In this procedure, the hip is dislocated and the degenerative hip joint is removed. The prosthesis can be secured with bone cement or press fit components. Bone will grow into the press fit components.