Remember the day your doctor told you that your knee or hip was permanently damaged and that to reduce the pain and improve mobility, you needed to consider having surgery to replace it? The good news, the doctor assured you, was that total joint replacement is usually highly successful. After hearing more about the potential pros and cons of surgery, one of your first questions probably was, how long do knee replacements last? (Or, “How long do hip replacements last?”)
How long do hip and knee replacements last?
Depending on the year, the answer to this question was most likely that the new joint would last somewhere between 10 and 20 years. If you were 70 or 80 years old at the time, this probably sounded good. But if you were 40, it might have been a little frightening. Even after you had the surgery, that nagging question of “how long will the new joint last?” probably remained in the back of your mind, resurfacing from time to time.
Each year, approximately 285,000 total hip replacements and 600,000 knee replacements are done in the United States. Most of them are successful. In a 1994 consensus statement on hip replacement and a 2003 consensus statement on knee replacement, the National Institutes of Health (NIH) reported that having knee or hip replacement reduced pain and improved functioning in most people. However, over time, some individuals develop problems with their replacement joints or implants. For these individuals, revision surgery — surgery to replace a worn-out, loosened, or otherwise “failed” artificial joint — may be necessary.
For many, revision surgery can relieve the pain and lessen the disability caused by a failed implant. However, revisions do not have as high a rate of success as first-time joint replacements, and revisions usually take more time in the operating room and require more rehabilitation time. In this article, I’ll discuss what you need to know about revision surgery, including what you can do to keep your joint replacement in good shape so that you’re less likely to need more surgery.
Hip revision surgery
Total joint replacement for the hip first became available in the early 1960’s. (See Recovering From Total Hip Replacement for more information on hip replacement surgery.) Since the procedure’s introduction, people who have had it have participated in many retrospective outcome studies (studies that look back on a treatment that has already been given to see what effects it had). These studies have shown that most of those who undergo hip replacement have less pain, better joint function, and a better quality of life. Over the years, implant makers have improved design, construction, and implantation methods, allowing surgeons to replace hips safely and effectively, with long-lasting results. The American Academy of Orthopaedic Surgeons says on its Web site that a hip replacement has an 80% likelihood of lasting 20 years. The 1994 total hip replacement consensus statement, which took into account a number of studies done throughout the world, said that more than 90% of replacement hip joints are never revised.
When a hip implant fails, it may cause a lot of pain and stiffness in the joint, and it may interfere with easy movement. There are several reasons why a hip implant may fail. Some of the most common are loosening of the implant, infection, and repeated dislocations.
Loosening of a hip implant
Loosening is when the implant no longer adheres tightly to the bone. Hip implants are made of two main components: a ball-and-stem piece that is attached within the thighbone and a cup that is attached within the hip socket. (See Implant Components for an illustration.) Originally, in all total hip replacements, the components were cemented to the bone using a material called methylmethacrylate. This cement provides very tight adhesion, but small cracks can develop in the cement over time, leading to a loosening of the implant. This happens for the most part in individuals who are very active or very heavy. In addition, when the cement cracks, tiny particles of it float around in the joint. The implant itself can wear down and create loose particles in the joint, as well. This is particularly a problem when a plastic part rubs against a metal part, causing friction and releasing particles of plastic and metal. Loose particles floating within the joint capsule cause inflammation in the joint, and the inflammation weakens the bone where the implant is attached. The weakened bone allows the implant to move and shift. Once the implant is loosened, pain is the primary symptom. A doctor confirms the loosening by taking x-rays and looking for signs of bone loss.
Companies making implants have worked to reduce the wearing down of the components by making them out of newer materials, including more durable metals, plastics, and ceramics. New fixation cements have also been developed. However, few if any long-term studies on the new materials are not yet available.
To prevent loosening related to cement particles, hip implant designers came up with an uncemented version. In this version, the back of the cup and the stem are made out of a porous material that new, healthy bone can grow into. This way, the bone attaches itself to the implant, providing stabilization and a tight fit. Surgeons often use these uncemented joints on people who are younger and potentially more active, hoping that the implants will last a lifetime. To be a good candidate for cementless implants, a person must be able to grow healthy bone. The implant will loosen if the surrounding bone, for whatever reason, doesn’t grow well enough to hold the implant in place.
Breaks and infection of hip implants
Hip implants can also fail if they break or if the joint becomes infected. Revision surgery is needed to replace a broken implant. If the joint becomes infected, the doctor may first try prescribing an intravenous antibiotic. If that doesn’t clear up the infection, surgery may be needed. The surgeon first removes the implant and cleans out the joint. Depending on how severe the infection is and what is causing it, the new implant may be put in right away and the patient treated with antibiotics for several weeks. Or the new implant may not be put in until the infection is cured, meaning a second surgery is needed. (A temporary joint, usually made of bone cement impregnated with antibiotics, helps keep the bones in their proper place until the second surgery.) The 1994 hip replacement consensus statement reported that less than 1% of people who had hip replacements developed infections.
Dislocations of the hip joint
Revision surgery is sometimes required if the replacement hip dislocates repeatedly. If you dislocate your hip, a doctor can usually use nonsurgical procedures to put the ball part of the implant back into the cup. But if it happens repeatedly, the muscles and tendons around the hip can become stretched, making it easier for dislocations to occur again. Replacing the old cup with a repositioned new one can usually reduce these painful and surprising dislocations. People who had minimally invasive joint replacement the first time around may be less likely to dislocate their hip since the tissues around it were less affected by the original surgery. Minimally invasive hip replacement is a relatively new technique that reduces the cutting of muscles and ligaments that help hold the ball in the socket. New surgical techniques have also made it easier for surgeons to position the implant correctly in the first place.
Knee revision surgery
Like total hip replacement, total knee replacement is usually successful. Of people who have a knee replaced, 90% have reduced pain, improved function, and a better quality of life, and 85% are satisfied with the results. However, knee implants are susceptible to many of the same problems that can plague hip implants.
The knee implant is made of several different components (see Implant Components for an illustration). The metal femoral component attaches to the end of the thighbone. The tibial component includes a T-shaped metal tray that attaches to the end of the shinbone and a spacer made of tough, slippery plastic. Finally, the plastic patellar component attaches to the back of the patella, or kneecap. (For more about knee replacement surgery and knee implants, see “Knee Replacement: Getting the Best Results” in the November/December 2004 issue.)
Surgeons routinely use cement to adhere the knee implant to the bone, and so, over time, the same loosening can occur as with total hip replacements. Along with cement particles, particles of the worn-down implant floating within the joint can contribute to loosening because of the bone-weakening inflammatory response they cause. Loosening may also be related to poor surgical technique, high levels of stress on the joint because of high levels of activity, or bone deterioration. Poor alignment of the femoral and tibial components of the implant can contribute to the wearing down and loosening of the implant. Newer surgical techniques, such as the use of computer navigation, may reduce alignment problems.
Other reasons for revision include fracture or dislocation of the patella, fractures in the bones near the implant, and infection. As with first-time knee replacement surgery, disabling pain and inability to function are the most common complaints that lead to knee replacement revision.
Of people who have total knee replacement revision surgery, 70% have less pain, improved functioning, and better overall quality of life, compared to 90% of people who have first-time knee replacement. Revision surgery to correct loosening is reported to be more successful than revision surgery to treat infection. In revision for infection, surgeons usually follow a two-stage surgical plan. In part one, the implant is removed, the joint is cleaned out, and a temporary joint is put in. After the infection is cured with antibiotics, a new implant is put in place. Revision is done only after attempts to treat the infection with intravenous antibiotics have failed.
Factors that put people at risk for knee implant failure include age under 55 and obesity. Some studies have indicated that men with osteoarthritis have a higher rate of failure than women, while other studies have indicated that there is no difference between men and women. In people with rheumatoid arthritis, the failure rate is higher among men.
Hip and knee revision surgery is more complicated
Overall, revision surgery is more complicated and takes longer than first-time total joint replacement, and the outcomes are not expected to be as good. Revision surgery is also costly, and it requires highly experienced surgeons and support staff. Before a new implant can be put in place, the surgeon has to take out the original implant and sometimes bone and tissue nearby. If cement was used, it all has to be removed. If an uncemented implant was used, the original implant has to be detached from any bone that has grown into it. The bones may be weaker than when the first surgery was done, so the surgeon may need to reinforce them with bone grafts or bone particles (from your body or from a bone bank), metal plates or wedges, rods, and/or wire. Special implants are used for revisions, and occasionally, a custom-made implant (made by the manufacturer for a specific individual) is needed. Once the surgery is done, the hospital stay afterward may be longer than for a first-time replacement, and the overall recovery time is also longer.
As someone who has had total joint replacement surgery, you may not be as apprehensive about having surgery as you were the first time around. You’ll still face some of the same risks as you did after your first total joint replacement, though. These risks include blood clots, anemia, infection, and pneumonia. After knee replacement revision, people may have a problem with alignment of the leg, shortening of the operated-on leg, and reduced range of motion. After hip revision, one leg may be shorter than the other, and people may need to walk with assistive devices such as a walker, crutches, or canes for longer than with first-time joint replacement, depending on how much bone grafting was needed. Surgeons carefully evaluate each patient, and some decisions on the best approach are made in the operating room. Minimally invasive procedures, such as those used for first-time hip and knee replacements, aren’t available for revision surgery, since the surgeon needs to remove the original implant.
What can you do to avoid joint revision surgery?
Now that we’ve reviewed the reasons for and potential problems of having revision surgery, let’s discuss what you can do to avoid it.
- If you are having joint replacement surgery for the first time, follow your doctor’s and physical therapist’s instructions afterward. You want the outcomes of this first surgery to be the best they can be. This means doing your exercises. You will need to increase and maintain your range of motion and slowly but gradually increase your joint strength and overall body conditioning. Once you are done with your physical therapy, it is up to you to maintain your range of motion and joint strength, as well as to watch for and report problems to your doctor. Avoid activities that place extra stress on your joint. For instance, some doctors suggest using an elevator when you can, since stairs put more stress on joints, especially the hips.
- If you’ve had a hip replacement, learn and follow the precautions against dislocation. Preventing dislocation in the first three to six months, while the soft tissues around the joint are still healing, is extremely important. Dislocation stretches the muscles and tendons, making it easier to dislocate again. Precautions include not crossing your knees when sitting, not bending your hips past a 90-degree angle, and not turning your leg inward.
- Follow your doctor’s advice about which activities to do and not to do. Most physicians recommend that people who’ve had joint replacement steer clear of high-impact activities, such as running and jumping, and carry no more than 40 pounds. Yes, you may be able to do these things, but you want your joint to function well for as long as you are alive. And each time a revision needs to be done on the same joint, the chance of success decreases.
- Remember that body weight in excess of 165 pounds can be detrimental to total joint longevity. Add a little low-impact exercise to your weight management program, such as walking, swimming, or bike riding. This will help with your cardiovascular health as well. Water exercise is the least stressful on your replacement joint.
- Stay in touch with your orthopedic surgeon so that the surgeon can periodically check on your joint.
- After joint replacement surgery, follow carefully your doctor’s precautions against infection. Doctors usually recommend taking antibiotics before and after other surgery, dental surgery, and dental cleaning. If you aren’t sure when you should be taking antibiotics, talk to your doctor. If you do develop an infection, have it treated in a timely fashion. Be especially careful of infections of the teeth, urinary tract, throat, skin, and lungs, as these are common. If not treated early, an infection that first affects a particular area may later travel to other parts of your body, including your replacement joint.
If it’s time for revision
If you and your doctor decide that you need revision surgery, here are a few things to keep in mind:
- Just like first-time total joint replacement surgeries, revisions have become more common. This means that doctors and hospital staff are becoming more experienced with the procedure.
- Some surgeons specialize in doing revisions. When choosing your surgeon and hospital, make sure they are highly experienced specifically with total joint replacement revisions.
- Your surgeon will evaluate you carefully. The surgeon will take into consideration the health of your bone, whether cement is needed, your age, what you can do and what you need to be able to do with your joint, as well as the reason that you need revision (loosening, breakage, infection, dislocation, and so on). Each situation will be treated accordingly.
- If you have been able to maintain muscle strength and good body conditioning since your original surgery, you may have an easier time recovering from revision surgery.
- Having had joint surgery, you are more experienced. You know the routine, you know what to ask, and you know what to expect from yourself, your family, and your health-care team. If you smoke, you know to stop at least two months before surgery. You may even have saved your crutches, walker, or other assistive devices from the last time.
Remember that there are things you can do to help prevent the need for revision surgery, and there are ways to make revision easier if you need it. Rather than worrying about the possible need for a revision, enjoy your life with your present joint replacement, taking good care of it along the way. Each year, surgeons and hospital staff become more experienced in first-time and revision joint surgery, and manufacturers create better joints. This means that people having a revision surgery are getting better care than ever before. Hopefully, it also means that fewer people will need revisions in the future.