A unicompartmental knee replacement is sometimes used instead of a total knee replacement when only one side of the knee has been damaged by osteoarthritis. Unicompartmental knee replacements involve smaller incisions, less bleeding, quicker recovery, and less bone loss than a total knee replacement.
The prosthesis does not interfere with existing ligaments, tendons, or nerves. You retain normal balance and the natural stability of the healthy half of your knee joint and your own tendons and ligaments. Your kneecap is left in place, enabling you to regain much of the strength in your quadriceps.
The minimally invasive partial knee replacement is indicated in patients who have severe arthritis of the knee that have failed conservative treatments may consider this procedure. Conservative measures may include, but are not limited to, medications (such as Advil, Naprosyn, Celebrex, and Vioxx), cortisone injections, strengthening exercises, and weight loss. If these treatments are not adequate, and you as a patient are not satisfied, then surgical procedures may be considered.
The partial knee surgery may be possible if the arthritis in the knee is confined to a limited area. If the arthritis is widespread, then the partial knee replacement is NOT appropriate, and should not be considered. In addition, the partial knee surgery is recommended in patients who are:
- Older than 55 years
- Not obese
- Relatively sedentary
- Have intact ligaments (specifically the ACL)
If these qualifications are not met, then the minimally invasive partial knee surgery may not be as successful. Unfortunately, many patients are therefore ineligible for this minimally invasive procedure.
Most patients who seek surgical management have arthritis that is too advanced for the minimally invasive partial knee replacement procedure. Because surgical treatment is considered a 'last-resort' by most patients, by the time surgery is necessary, their arthritis is too advanced to consider this minimally invasive procedure. If partial knee replacement is done in a patient who is a poor candidate, failure rates can be high, and conversion to a traditional total knee surgery may be more difficult.
Total knee replacement
Total knee replacement is a surgical procedure in which injured or damaged parts of the knee joint are replaced with artificial parts. The procedure is performed by separating the muscles and ligaments around the knee to expose the knee capsule (the tough, gristlelike tissue surrounding the knee joint). The capsule is opened, exposing the inside of the joint. The ends of the thigh bone (femur) and the shin bone (tibia) are removed and often the underside of the kneecap (patella) is removed. The artificial parts are cemented into place. Your new knee will consist of a metal shell on the end of the femur, a metal and plastic trough on the tibia, and if needed, a plastic button in the kneecap.
Total knee replacements are usually performed on people suffering from severe arthritic conditions. Most patients who have artificial knees are over age 55, but the procedure is performed in younger people. The circumstances vary somewhat, but generally you would be considered for a total knee replacement if:
- You have daily pain.
- Your pain is severe enough to restrict not only work and recreation but also the ordinary activities of daily living.
- You have significant stiffness of your knee.
- You have significant instability (constant giving way) of your knee.
- You have significant deformity (lock-knees or bowlegs).
An artificial knee is not a normal knee, nor is it as good as a normal knee. The operation will provide pain relief for at least ten years. If replacement provides you with pain relief and if you do not have other health problems, you should be able to carry out many normal activities of daily living. The artificial knee may allow you to return to active sports or heavy labor under your physician's instructions. Activities that overload the artificial knee must be avoided. About 90 percent of patients with stiff knees before surgery will have better motion after a total knee replacement. Total knee replacement is a major operation. About one patient in four develops one or more complications. The effect of most complications is that you must stay in the hospital longer. The most common complications are not directly related to the knee and usually do not affect the result of the operations. These complications include urinary tract infection, blood clots in a leg, or blood clots in a lung. Complications affecting the knee are less common, but in these cases the operation may not be as successful. These complications include:
- some knee pain
- loosening of the prosthesis
- infection in the knee
A few complications such as infection, loosening of prosthesis, and stiffness may require reoperation. Infected artificial knees sometimes have to be removed. This would leave a stiff leg about one to three inches shorter than normal. However, your leg would usually be reasonably comfortable, and you would be able to walk with the aid of a cane or crutches, and a shoe lift. After a course of antibiotics the surgery can often be repeated.
About 85 to 90 percent of total knee replacements are successful up to ten years. The major long-term problem is loosening. This occurs because either the cement crumbles (as old mortar in a brick building) or the bone melts away (resorbs) from the cement. By ten years, 25 percent of total knee replacements may look loose on x-ray, and about 10 percent will be painful and require reoperation. By ten years, possibly 20 percent may require reoperation.
Loosening is in part related to your weight and activity. For that reason, total knee replacement usually is not performed on very obese or young patients. A loose, painful artificial knee can usually, but not always, be replaced. The results of a second operation are not as good as the first, and the risks of complication are higher.
Preparing for a total knee replacement begins several weeks ahead of the actual surgery date. Sometimes this can be done at your local community hospital. Maintaining good physical health before your operation is important. Activities which will increase upper body strength will improve your ability to use a walker or crutches after the operation.
A blood transfusion is sometimes necessary after knee surgery. You may wish to donate several pints of blood prior to your surgery. Then if you require a transfusion you will receive your own blood. This is called autologous blood donation. The first donation must be given within 42 days of the surgery and the last, no less than seven days before your surgery. The usual amount of donation is two units, which may require separate visits to the blood center.
When donating blood, you must be healthy, without a cold, flu or infection, as you could get this same illness when your blood is transferred at the time of surgery. Eat a nourishing meal two to four hours prior to donation, and avoid strenuous exercise for twelve hours following the procedure.
The blood donor center will check the blood count before drawing additional units. A prescription for iron will be given. Iron may be constipating for some people, so sometimes a stool softener is prescribed. Stool softeners can also be purchased over the counter.
You may be a candidate for autotransfusion after your surgery. Blood collected from the wound drain is filtered and transfused back to the patient early in the post-operative period. The physician will assist you in deciding whether this procedure will be done.
The physician may order blood tests and urinalysis two weeks before surgery to make sure that a urinary tract infection is not present. Urinary tract infections are common, especially in older women, and often go undetected. Teeth need to be in good condition. An infected tooth or gum may also be a possible source of infection for the new knee. The orthopaedic physician may ask you to see a medical doctor, especially if medical problems have been present in the past.
When making preparations for surgery, you should begin thinking about the recovery period following surgery. A patient with a new total knee replacement will need help at home for the first several weeks. Assistance with dressing, getting meals, etc. may be necessary. Most often discharge from the hospital is anticipated in about 3-4 days. Your energy level will not have returned. If assistance from someone at home is not possible, it may be necessary to think about making arrangements to stay a few weeks in an extended care facility. A social worker is available at the hospital to plan an extended period of recovery if necessary.