How hip is hip replacement surgery?

People in their 60s and 70s were once the primary beneficiaries of total hip replacement (THR) surgery, which has been relieving pain in people with severe osteoarthritis of the hip since 1960. Today, however, THR is an option for adults of any age, whether in their 90s, 50s, or younger – thanks to advances in surgery, rehabilitation, and the design of the implant used to replace the diseased hip. A study in the March 2003 issue of Mayo Clinic Proceedings found that THR was reliable, durable, and safe in 65 elderly patients (average age 92) who underwent surgery between 1970 and 1997. More recent studies have produced similar findings in both older and younger adults.

In the United States, about 170,000 THRs are performed every year, in adults aged 20 to 100. Virtually everyone who undergoes the procedure can walk farther and faster than they could before surgery. Although THR cannot restore the ability to run or participate in other high-impact activities or contact sports, otherwise healthy, well-motivated THR patients nearly always can – and should – resume low-impact activities, including cycling, swimming, hiking, doubles tennis, golfing, and bowling. In elderly patients, THR often restores functional independence and eliminates the need for long-term supportive care.

It’s no wonder, then, that many people bothered by pain in the hip area are eager for surgery. "People often come to me thinking that THR will help them, frequently because a friend who’s had the procedure is thrilled with the result," says Dr. Michael L. Reyes, head of the joint replacement surgery program at the Seton Medical Center in San Francisco, California. But the decision to proceed with surgery should not be made lightly. THR is a major operation that requires precautions to limit the risk of side effects, and many weeks to several months of recuperation before recovery is complete.

Furthermore, only certain patients can be helped. "I have two main problems," Dr. Reyes says. "One is persuading people – particularly those in their 50s – to wait until they fulfill the criteria for surgery, and the other is convincing some people that they are not candidates for THR in the first place."

Replicating A Normal Hip Joint

The hip joint is formed by the ball-shaped head of the thigh bone (femur) and a cup-shaped cavity, or socket (acetabulum) in the pelvic bone (see illustration on Page E-1). Bands of tissue (ligaments) provide stability and connect the ball to the socket. The surfaces of the ball and socket are covered with a smooth durable lining (articular cartilage) that provides cushioning. All remaining joint surfaces are covered by a layer of thin, smooth tissue (the synovial membrane), which manufactures a lubricant (synovial fluid). In some people, the tissues that protect the joint begin to erode owing to overuse, normal wear and tear, or trauma. As a result, the bones may begin to rub together, which can prompt severe pain.

The Procedure

Hip replacement, or arthroplasty, involves removing the degenerated sections of the hip joint and inserting a prosthesis – a ball attached to a stem that is inserted into the remaining portion of the thigh bone and a socket that must be fixed to the pelvis at the other end (see illustration on Page E-1). The prosthesis may be made of plastic, ceramic, metal, or a combination of these materials. Two major methods of fixation, which are also sometimes used in combination, are available:

• Cementless. The ends of the prosthesis are coated with a porous material and tightly fitted into place. The porous material encourages new bone growth, which fuses with the prosthesis and provides additional reinforcement. Little to no weight can be put on the affected leg for about three weeks after the prosthesis is inserted. Crutches or a walker must be used for a total of six to 12 weeks. Cementless prostheses are generally recommended for younger, more active patients with good bone density.

• Cemented. The prosthesis is secured to the femur and the acetabulum with special bone cement. Because a patient with a cemented prosthesis can put full weight on the limb and walk without support almost immediately after surgery, rehabilitation is faster. Cemented prostheses are more commonly recommended for older patients and those with compromised health or poor bone density.

Life With A New Hip

Patients who undergo THR require life-long follow-up care aimed primarily at protecting and monitoring the integrity of the prosthesis, which normally lasts 15 to 20 years. Staying active is important to maintain the gains achieved through surgery. But overuse may speed implant failure, which can be highly painful and difficult to repair. The specific activities permitted depend on each patient’s general health, fitness, motivation, and familiarity with the activity. Professional guidance about how to exercise is important because, unlike a normal hip, the prosthesis does not contain nerves that can send pain signals warning of possible damage.

A physical examination and x-ray studies should be performed every 12 to 18 months. If loosening or other evidence that the prosthesis may fail is discovered, the prosthesis should be removed and replaced. This procedure, known as revision surgery, is nearly always successful. However, results are generally not as good as they are after the initial procedure. The need for revision surgery can be delayed or eliminated by postponing initial THR until hip pain significantly interferes with daily life and walking distance decreases to about a mile or less. Many experts endorse these criteria.

Who Is Most Likely To Benefit?

THR should be considered only after trying less invasive alternatives, including pain relievers and anti-inflammatory medications, weight loss if applicable, and use of a cane. Although osteoarthritis is the most common reason for THR, the procedure can relieve chronic hip pain due to rheumatoid arthritis, bone tumors, and certain other underlying causes. THR is used less frequently for hip fractures, which are more often repaired with plates, screws, and pins rather than an entirely new artificial joint.

More women than men fulfill the criteria for THR. A study published in the February 2003 issue of the American Journal of Medicine based on data from the Nurses’ Health Study, a large- scale, long-term population study, examined nurses who underwent the procedure for osteoarthritis after 1990. The two clearest indicators of risks were advanced age and long-term obesity. This study found no association between THR and recreational physical activity, smoking, alcohol use, or hormone replacement therapy.

Chronic medical problems are not usually an obstacle to THR. Heart disease, diabetes, and chronic obstructive lung disease (emphysema or chronic bronchitis) rarely cause the procedure to be postponed. THR can even be performed in people with bone quality and density that are significantly compromised by osteoporosis. Medical problems that may delay surgery include active infections and unstable angina, unstable hypertension, or unstable chronic obstructive pulmonary disease.

New and exciting advances in the field of joint replacement surgery, which include minimally-invasive procedures, computer navigation, and modern new implants, have made this procedure even better, resulting in much less pain and discomfort post-op, shorter hospital stay, and much faster functional recovery.