Hip replacement (arthroplasty) is an operation to remove a painful or damaged hip joint and replace it with an artificial joint (prosthesis). The socket part of the hip joint (acetabulum) and the rounded part of the top of the femur (thigh bone) are replaced with artificial parts.

Why might I need it?

Hip replacement surgery is done to replace a hip joint that is damaged by disease or injury.

Osteoarthritis is one of the most common causes of a damaged and worn hip joint. It causes stiffness, swelling, pain and loss of motion to the extent that normal activities such as walking and climbing stairs become increasingly difficult. Walking aids such as a cane or walker may be necessary. If the usual treatments for arthritis (rest, analgesia, anti-inflammatory medication, physiotherapy) are not enough, hip replacement surgery may be necessary to relieve pain and restore quality of life.

Hip replacement surgery is also done for hip joints damaged by other forms of arthritis such as rheumatoid arthritis and septic arthritis.

Other common reasons for hip replacement include:

• Fracture of the neck of the femur. This is a very common injury in elderly patients (many have osteoporosis).
• Avascular necrosis - the blood supply to the head of the femur is cut off causing the bone to die.
• Paget's disease of bone.
• The late (delayed) effects of congenital dislocation of the hips.
• Other injury or disease of the hip joint.

Most patients with artificial hips are over 55 but the operation is occasionally performed on younger people.

What does it involve?

The hip joint is a ball-and-socket joint; the ball of the femur fits into a socket in the pelvis (acetabulum).

In hip replacement surgery, the existing hip joint is replaced with an artificial head of femur and acetabulum. The operation is done under general or spinal anaesthetic and is usually done in a special sterile ‘clean air’ theatre.

1. The surgeon makes a cut along the side of hip and exposes the hip joint.
2. The ball portion of the joint (head of the femur) is removed from the socket (acetabulum).
3. The upper part of the femur is cut off and the acetabulum is hollowed out.
4. A plastic or metal socket is fitted into the acetabulum.
5. A short, angled metal shaft or stem, with a smooth ball on its upper end, is placed into the hollow of the femur.
6. The new top of the femur is then placed into the socket. A bone cement may be used for either or both stem and socket.
7. Drains may be inserted to help drain any fluid or blood from the new joint. The surgeon then reattaches the muscles to the top of the femur and closes the wound.

Considerable advances have been made in technique and materials used in hip replacement. Current materials include titanium or cobalt chromium alloys.

A new process called metal on metal resurfacing involves replacing the diseased or damaged surfaces with metal surfaces. Less bone is removed as only the joint surfaces are replaced with metal inserts.

Blood transfusions may be necessary during or after the operation.

Joint replacements last about 10–15 years. The younger a person is at the time of surgery, the more likely it is that surgery will have to be repeated later in life. Artificial joints wear and loosen in the bone with time. Younger people are also likely to place more stress on the artificial joint. However, younger people with severe hip disease who have hip replacement surgery benefit from many years of increased flexibility and pain relief.

What happens after the operation?

After surgery, the hip is covered with a padded dressing. Special elastic anti-embolic (clotting) stockings are worn to prevent blood clots. A triangle-shaped cushion may be positioned between the legs to keep them from crossing or rolling in.

With the help of a walker, most people are out of bed and walking the day after the operation. However, you will need physiotherapy and an exercise programme to strengthen the hip and thigh muscles. As you get stronger the walker will be swapped for crutches.

You will have to stay in hospital for 4-6 days or until you can safely get in and out of bed and can walk up to 75 feet with crutches or a walker.

While you are encouraged to walk and take gentle exercise, high-impact activities should be avoided. Try not to bend or twist at the hip, avoid low chairs and toilet seats, and do not to cross your legs or lie on your side.

Home adaptations such as elevated toilet seats, shower seats, handrails and raising the surfaces of couches and chairs may be helpful.

The staples are removed 2 weeks after surgery. After 3-4 weeks, you should be able to walk with the help of a cane instead of crutches. After about 6 weeks you will probably be able to walk unaided.
Always tell your dentist and other health professionals that you have had a hip replacement. Antibiotics must be used before and after any medical or dental procedure for the rest of your life.

What are the benefits of hip replacement?

Pain relief is the greatest benefit and often the major reason for surgery. Surgery also improves movement, strength, and coordination. Limp is cured and most people are able to walk, climb stairs and lead an active life again.

What are the complications of hip replacement surgery?

• Infection. Call your doctor if you notice any drainage or foul odour from the wound, if you develop a fever, or if there is any increased tenderness, redness, or swelling. Deep infection may require removal of the joint.
• Blood clots in the deep veins of the pelvis or leg (deep vein thrombosis). Parts of these clots may break away (embolus) and lodge in a major lung artery causing life threatening pulmonary embolus. Anticoagulants are used to prevent deep venous thrombosis. Contact your doctor immediately if you develop breathlessness, chest pain or if you cough up blood.
• Loosening of the new joint, or wearing away of the joint or bone next to it, has always been a major problem in joint replacement. The shaft of the prosthesis becomes loose in the hollow of the thigh-bone or becomes dislocated. Revision surgery is necessary in around 10% of all total hip replacement cases. Because this is more likely if the joint is heavily stressed, hip replacement is not commonly done in young and physically active patients.
• Risks of general anaesthesia/spinal anaesthesia.
• Bleeding caused by injury to blood vessels.
• Injury to nerves or bones during the operation.
• Unequal leg length after the operation.
• Dislocation of the new joint. This usually occurs within a few weeks of surgery and causes immediate pain and inability to bear weight. It can be caused by moving the hip in certain ways i.e. sitting too low or crossing the legs.
• Rarely, fat embolism (pieces of fat from the bone marrow of the femur enter the bloodstream and travel to the lungs).