Institute of Orthopedics

The surgeon makes an incision along the top of the thigh bone (femur) and pulls the thigh bone away from the socket of the hip bone (the acetabulum). An artificial socket made of metal coated with polyethylene (plastic) to reduce friction is inserted in the hip. The top of the thigh bone is cut, and a piece of artificial thigh made of metal is fitted into the lower thigh bone on one end and the new socket on the other.

The artificial hip can either be held in place by a synthetic cement or by natural bone in-growth. The cement is an acrylic polymer. It assures good locking of the prosthesis to the remaining bone. However, bubbles left in the cement after it cures may act as weak spots, causing the development of cracks. This promotes loosening of the prosthesis later in life. If additional surgery is needed, all the cement must be removed before surgery can be performed.

An artificial hip fixed by natural bone in-growth requires more precise surgical techniques to assure maximum contact between the remaining natural bone and the prosthesis. The prosthesis is made so that it contains small pores that encourage the natural bone to grow into it. Growth begins 6 to 12 weeks after surgery. The short term outcome with non-cemented hips is less satisfactory, with patients reporting more thigh pain, but the long term out-look is better, with fewer cases of hip loosening in noncemented hips. The trend is to use the non-cemented technique. Hospital stays last from four to eight days.

Both chronic osteoarthritis and rheumatoid arthritis commonly cause people to lose knee function to the degree that they need a knee joint replacement (total knee arthroplasty or TKA). But knee damage may also stem from injury or infection. Generally, people require a TKA a decade earlier due to rheumatoidarthritis as opposed to osteoarthritis