When arthritis and other conditions attack the hips, knees and other joints, exercise, hobbies – even a quick stroll across the house – can bring agony. For most patients, joint replacement is a life-changing experience, restoring normal range of motion and allowing a return to normal routines. And as the population ages, the number of replacement surgeries is on the rise.
More than 1 million Americans have a hip or knee replaced each year, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases. These replacements, known as prostheses, are very reliable, says Al Mollabashy, MD, medical director of orthopedic oncology surgical services at Baylor University Medical Center, part of Baylor Scott & White Health. In many cases, they can last 20 years, which may be the remaining lifetime of the patient. But as we are living longer, more active lives, more and more patients will end up needing a replacement for their replacement. "The problem is, all those implants done 20 years ago are now coming to maturation and are, for lack of a better term, wearing out," Dr. Mollabashy says. "There will be a need for a lot of joint revision surgery in the next 10 years."
Most Common in Complex Joints
Joint revision surgery is most common in the complex joints: first the knee, followed by the hips and shoulder, Dr. Mollabashy says. "The number one reason is infection, which can occur at any time, especially early after surgery," he explains. That is because the immune system, the body’s fighting force against infections, has a more difficult time attacking bacteria that find their way to the metal or plastic of joint replacements. "The second major reason for joint revision surgery is wear of the prosthesis, and loosening after the prosthesis has been used long term," Dr. Mollabashy adds. "That can occur in the 10- to 20-year range.
Pain is the leading sign of problems with the implanted joint, says Dr. Mollabashy. Others include change of function, the joint. "If the prosthesis is loose, it may present in different ways, including weakness or an inability to bear full weight on the joint," he adds. Warmth and redness, and draining, are the most common signs of infection.
An X-ray can offer the first indication of what is happening. A referral to an orthopedic surgeon is the next step. Even if there are no troublesome symptoms, a joint, like any mechanical device, needs regular checkups to remain in working order, Dr. Mollabashy points out. "Many people believe that a primary joint replacement will last forever. Unfortunately, that isn’t the case. Patients need to be seen by their primary surgeon every few years to get a radiograph to see if everything is going well."
As a large, nationally recognized program, the orthopedic surgeons on the medical staff at Baylor University Medical Center have considerable expertise in joint revision surgery, Dr. Mollabashy notes. Joint revision surgery requires a high level of experience on the part of the surgeon and team, as well as specialized tools, and extensive preoperative planning. In fact, depending on the procedure in question and the particular case, revision of joint replacement can be far more complex than the original surgery. This is why not all surgeons who perform total joint replacement also perform joint revision surgery.
Most patients experience excellent results, says Dr. Mollabashy. "The key is that it doesn’t just take a surgeon to care for a person with a failed replacement. It takes a team, including radiologists, pathologists, infectious disease specialists, physical therapists, and operating room personnel who are accustomed to doing these procedures." The team works together to develop an individualized treatment plan specifically for the needs of each patient.
The Baylor Dallas team also cares for patients with joint problems caused by tumor growth and other effects of cancer in the Complex Joint and Musculoskeltal Tumor Program. Tumors commonly occur in the ends of the long bones of the body, including the bones of the knees and hips. "By and large, it’s usually when there is a metastatic cancer from another organ that damages bone," Dr. Mollabashy says. Another cause is myeloma, a type of cancer that starts in the bone marrow. "The initial joint problems don’t have the same causes as typical joint revision, but the implants we use to correct the problem, and the surgical techniques are similar," says Dr. Mollabashy. Patients with cancer may also require additional care to prevent future damage and infection in the affected area.
Innovations in Implants
Improvements in joint replacement materials and techniques have extended the typical lifespan of implants, Dr. Mollabashy says. "We now have better, more porous metals, called trabecular metals," he explains. These designs, made with an element called tantalum, have several advantages over the traditional titanium or stainless steel materials. For one, they are more effective at encouraging growth of bone and soft tissue on the implant itself. This tends to improve the connection and fit. These materials are also more elastic, so they move and give more like natural bone.
Another improvement, says Dr. Mollbashy, is new techniques for fixing the replacement to the bone that "don’t require the use of cement." That avoids "one of the primary causes of trouble with replacement joints," he adds. "Cement breaks down and causes loosening."
"After time, many people think they have to accept that their initial joint replacement no longer works properly, but it’s simply not the case," Dr. Mollabashy says. "Most patients who undergo joint revision experience a dramatic improvement in joint function and mobility and an improved quality of life."