1. What is a joint replacement?
Joint replacements are surgeries to remove an arthritic or damaged joint and replace it with a prosthesis, or artificial joint. In 2005, over 285,000 hip replacements and over 523,000 knee replacements were performed in the U.S. As the population is getting older, the projected numbers of joint replacements that will be needed are staggering. By 2030, it is anticipated that close to 600,000 hip replacements and 3.5 million knee replacements will be done. Since the 1970s, orthopedists and engineers have worked together to develop the technology and materials used in joint replacements. Improvements in design and technique have made this one of the most successful orthopedic surgeries, with success rates upward of 90 percent.
2. What causes a joint to need to be replaced?
A joint is formed by the ends of two or more bones, which are covered with a smooth layer called cartilage. For example, the knee joint consists of the lower leg bones (tibia and fibula) and the thigh bone (femur). The hip joint is formed by the upper end of the femur (the ball) and part of the pelvis, called the acetabulum (the socket).
The smooth cartilage normally allows for near frictionless movement of the joints. But when the cartilage is damaged or diseased, the tissues around the joint become inflamed and painful. Over time, the cartilage wears away so that the rough edges of the bone rub against each other, causing more stiffness and pain. In some cases, the pain is so severe that a person will avoid using that joint, causing muscles around the joint to atrophy and making it even more difficult to move the joint. If only parts of the joint are damaged, the surgeon can sometimes replace just those parts. But if the whole joint is affected, then it may require a total joint replacement.
3. How is joint damage assessed and treated?
After a thorough physical examination and X-rays, the doctor will assess the extent of the joint damage. If other treatment options do not relieve the pain, then total joint replacement will be considered to restore pain-free mobility to the joint. This inpatient procedure involves removing the damaged parts of the joint and replacing them with metal and plastic surfaces that come in a variety of sizes to fit different patients. If patients have bone loss (from severe deformity or revision surgery), they may need custom-shaped implants for their surgery.
The materials used in a prosthesis generally are metal (stainless steel, cobalt-chrome alloys and titanium alloys) and durable, wear-resistant plastic (polyethylene). Bone cement may or may not be needed to secure the prosthesis to the bone.
4. Are there any complications in total joint replacements?
Complications are rare in total joint replacements, but they can include infection around the wound or prosthesis, blood clots from decreased mobility, excessive wear, loosening or breakage of the prosthesis, dislocation and nerve injury. The leg length may be shorter or longer afterward. You may need a blood transfusion. Some doctors will request that you donate your own blood ahead of time, so that you can receive it back after the surgery.
5. What happens after the total joint replacement?
After the surgery, it will likely take a few months for the surrounding tissues and muscles to heal and strengthen around the replaced joint. However, patients are encouraged to begin walking and using the replaced joint shortly after the operation. They can participate in a wide variety of activities, except for certain strenuous activities and sports, which can potentially destroy the artificial joint. Joint replacements are not really meant for high-impact activities.
