Total joint replacement is a surgical procedure in which certain parts of an arthritic or damaged joint, such as a hip, knee or shoulder joints, are removed and replaced with a plastic or metal device called a prosthesis. The prosthesis is designed to enable the artificial joint to move just like a normal, healthy joint.
Hip replacement involves replacing the femur (head of the thighbone) and the acetabulum (hip socket). Typically, the artificial ball with its stem is made of a strong metal, and the artificial socket is made of polyethylene (a durable, wear-resistant plastic). In total knee replacement, the artificial joint is composed of metal and polyethylene and it is used to replace the diseased joint. The prosthesis is anchored into place with bone cement or is covered with an advanced material that allows bone tissue to grow into it.
In shoulder replacement surgery, the artificial shoulder joint can have either two or three parts, depending on the type of surgery required.
- the humeral component (metal) is implanted in the humerus
- the humeral head component (metal) replaces the humeral head at the top of the humerus
- the glenoid component (plastic) replaces the surface of the glenoid socket
Total joint replacements of the hip, knee, and shoulder have been performed since the 1960s. Today, these procedures have been found to result in significant restoration of function and reduction of pain in 90 to 95% of patients. While the expected life of conventional joint replacements is difficult to estimate, it is not unlimited. Today’s patients can look forward to potentially benefiting from new advances that may increase the lifetime of the prostheses.
Total joint replacement is usually reserved for patients who have severe arthritic conditions.
Circumstances vary, but generally patients are considered for total joint replacement if:
- functional limitations restrict not only work and recreation, but also the ordinary activities of daily living
- pain is not relieved by more conservative methods of treatment, such as medications, by the use of a cane, and by restricting activities or physical therapy
- stiffness in the joint is significant
- X-rays show advanced arthritis or other problems