Benefits, Risks and Alternatives

INTRODUCTION
If you are contemplating having a total knee replacement, we feel you should know the facts about the expected benefits, as well as the risks and possible complications of the procedure. This information booklet is designed to review these facts with you so that you may make a more intelligent decision regarding surgery.

NON OPERATIVE TREATMENT
In our opinion total knee replacement is not a conservative operation. In the procedure your complete joint surface is removed and it is replaced with plastic and metal components. You become dependent on the function of these components and any failure of the components can result in pain and loss of function. We feel you should exhaust all reasonable nonoperative measures to control pain and maintain function prior to considering total knee replacement.

Arthritis of the knee is, by definition, a wearing away of cartilage. The cartilage that lines the knee is an exceptional material. It is smoother than any man-made bearing. The cartilage has no nerve endings in it and therefore, any motion between cartilaginous surfaces does not cause pain. In a patient with arthritis, as the cartilage wears away, debris is generated which causes an inflammatory response which produces pain and also accelerates the destruction of the joints.5->As compared to cartilage, the underlying bone does have-Eirve endings in it and also is not a good bearing material, motion between bones without cartilaginous surfaces may cause significant pain.

The mainstay of non-operative treatment is to control this process by decreasing the force applied across the joint, as well as decreasing the number of times that force is applied. In order to decrease the force several things can be done; the first is weight loss. Any excess weight causes significant extra force across the joint which increases the joint destruction as well as pain. Because of the muscles acting across the knee joint, normal walking causes a force across the knee approximately three to five times body weight. Therefore, if you are 20 pounds overweight, the force across the knee is increased by almost 100 pounds. Even small amounts of weight loss will decrease the force about the knee, slow down the destruction of the knee joint and decrease pain.

Another way to decrease the force is to use a cane or crutch. Usually it is used in the opposite hand, but can be used in the hand on the same side as the involved knee. Avoidance of high stress activities such as impact loading (e.g. jumping or jogging) or heavy lifting (greater than 20 pounds) also will be helpful in decreasing the force about the knee. Walking exceptionally long distances (greater than a mile) increases the number of times that the joint load is applied and this will also add to the deterioration of the joint.

The use of anti-inflammatory medications is also an important mainstay of non-operative treatment. Aspirin is the most commonly used anti-inflammatory medication but many people cannot take it because of either allergy or gastrointestinal difficulties. There are many aspirin substitutes that are currently on the market but are significantly more expensive than aspirin. There are many aspirin substitutes currently available which may have fewer side effects and more convenient dosage frequencies, but they are considerably more expensive. Some of these include Motrin, Naprosyn, Tolectin, Feldene, Voltaren, Lodine etc. For these drugs to achieve maximum effectiveness they must be taken regularly to maintain an effective level in the blood. An appropriate trial of one of these medications should be two weeks of continuous dosage. side effects should be monitored, and the drug discontinued if they occur. Chronic long term use requires monitoring of blood and urine tests by your doctor.
Exercise is useful mainly to maintain muscle tone and range of motion. Isometric exercises and gentle range of motion exercises should be sufficient because arthritis is often a problem of "wear and tear". Vigorous exercise and the use of weights only results in further deterioration of the joint.

Heat is also helpful to decrease stiffness and relieve pain. Superficial heat such as provided by liniments and appointments, etc. do not deliver the heat deep enough to be beneficial. The best is a hot water bottle or hot pack because the temperature can be controlled and they deliver a significant amount of heat deep to the joint. Use of a heated whirlpool or spa may also be helpful. Use of a heating pad can be helpful but care must be taken to avoid burning the skin.

Occasionally a Cortisone Injection can be helpful providing temporary relief for up to six months. Repeated cortisone injections (more than three) can cause damage to the knee and should be avoided.
In summary, the non-operative treatment of arthritis of the knee involves weight loss (if overweight), the use of a cane, use of an anti-inflammatory medication, avoidance of activities that cause increased force across the knee, gentle exercises to maintain muscle tone and range of motion, the use of heat and occasionally a cortisone injection.

ALTERNATIVES TO TOTAL KNEE REPLACEMENT
Total knee replacement is by far the best solution to most problems involving severe arthritis of the knee. But occasionally in certain circumstances other alternatives may be more appropriate. In patients who are under 40 who have a severe problem with only one knee and are otherwise healthy, consideration should be given to knee fusion (arthrodesis). After this operation the thigh bone (femur) grows to the lower leg bone (tibia) such that no motion occurs at the knee. This completely relieves pain and provides a stable leg for walking. Its advantages are that there are no implants that can come loose or fail in the future. There are no activity restrictions as are required after total knee replacement. For a manual laborer it may be ideal because there are no lifting restrictions. The disadvantage is that the knee no longer bends. Sitting in a tight space may be difficult, especially for tall people.

For patients in the 40 to 60 age group, with bowed legs or knock-knee deformity, a bone realignment (osteotomy) may be the best operative procedure. This is where the upper end of the tibia bone, or lower end of the femur bone, near the knee is cut and a wedge of bone removed to realign the leg. This procedure requires that some portion of the knee still has good cartilage on it and it is not possible when the cartilage is completely destroyed. This procedure has approximately a 70% success rate where success is defined as improvement of symptoms rather than complete freedom of pain. It is, however, an operation that preserves the knee joint and can allow full activity without restrictions.

Another alternative is cleaning out the knee joint (arthroscopic debridement). An instrument called an arthroscope is inserted into the knee and various other instruments are used to remove arthritic debris from the joint. Using only several small puncture wounds in the skin areas of complete loss of cartilage may be drilled or abraded. This procedure may give temporary relief of approximately six months and occasionally can work for several years. If there is x-ray evidence of severe arthritis, arthroscopic debridement is usually not successful.

A final alternative is partial knee replacement (unicompartmental knee replacement). This may be applicable if only one compartment (medial or lateral) is worn away and the remainder of the joint still has good cartilage. This is usually not recommended under age 60, when a realignment might be tried.

In your particular case one of these alternatives may be applicable. This should be discussed with your surgeon.

BENEFITS OF THE PROCEDURE
Total knee replacement is one of the most successful of all surgical procedures. Total knee replacement initially got a bad name as compared to total hip replacements. Early designs did not take into account the complicated biomechanics of the knee joint. The implants were designed as fully linked hinges (completely constrained) resulting in high stresses being placed at the point of fixation to the bone. In the 1970's less constrained knee replacements were developed. These designs allowed the stress to be taken up by the ligaments and yet had enough constraint to provide stability. Use of these prostheses and development of more accurate instrumentation has allowed the success rate to increase dramatically. At the present time knee replacements in the appropriate patients, are felt to succeed 95% of the time; these results are actually better than total hip replacement.

A "success" is defined as freedom from pain and restoration of motion as well as function. A successful knee replacement will allow a person to return to the routine activities of daily living. Certain restrictions do apply however. Persons with total knee replacements should not expect to resume jumping or jogging activities (impact loading). Lifting of weights of greater than 20 pounds should be avoided. Multiple repetitive loads such as walking long distances (greater than a mile) should be avoided. Tennis and racketball are not advised but golf, swimming and bicycling are good exercises. There are also some restrictions of motion. Although the leg with a knee replacement can flex up to 120 degrees, it is not advised that you attempt to bend it more. Therefore, it is not possible to squat and kneeling may be painful. An ideal candidate for total knee replacement is a patient who is over 65, not overly active, with normal mental capacity and who is not overweight.

The converse of this represents the so called "high risk patient" for total knee replacement; namely those who are under 65, overweight, very active or, who have had a previously cemented total knee that has failed. The relative success rates and risks in this group are discussed below.
In summary, if you are an ideal candidate, the expected benefits from total knee replacement should offer a 95% chance of relieving your pain and restoring motion and function for routine activities of daily living.

RISKS AND POSSIBLE COMPLICATIONS
The two major complications that can cause failure of a total knee replacement are infection and loosening. Infection has a very small chance of occurring (1 out of 100 in first time knee replacements and 4 out of 100 for revision knee replacement), but if infection occurs it is a very difficult problem to treat. Most infections in total knee replacement occur due to contamination at the time of surgery or subsequent would breakdown. It is a myth that surgery can be a truly sterile procedure. Any time that people are in an operating room there will be small number of bacteria that can settle in the wound. We take a number of precautions to decrease the number to a minimum. These include the use of sterile instruments and drapes as well as gowns and masks and head covers.

The patients leg is thoroughly cleaned with an antiseptic agent and all other areas are covered with sterile drapes. In addition to these routine measures, the surgery is performed in an "ultra clean room" or "laminar air flow room". In this type of operating room a uniform flow of filtered air is continually circulated over the wound. "Space Helmets" (body exhaust filtration systems) are also worn by the surgical team. Another measure to decrease infection is the use of prophylactic antibiotics. This means to use antibiotics in advance to prevent an infection rather than to treat it after it occurs. Normally we use antibiotics during surgery and for 48 hours after surgery.

If an infection occurs in a total knee, every effort is made to retain the prosthesis but this is successful less than 20% of the time. If the implant is loose or if the infection continues to reoccur, it is usually necessary to remove the implant completely in order to cure the infection. This, of course, leaves the patient without a knee joint, and although walking is possible, usually two crutches are required, the leg requires a brace and motion is minimal. At least six weeks of intravenous antibiotics are required to treat the infection. After the infection is cured, consideration can be given to reimplantation of a total knee but statistics show that 10% of reimplantation cases develop infection again. Because of this high recurrent rate, knee fusion is sometimes considered as an alternative to replacement of the artificial knee.

The second major complication is that of loosening. The key to success for total knee replacement is that all motion should occur between inert materials (i.e. metal and plastic). If the implant, loosens from their boney attachment, the motion between bone and implant will cause pain, bone destruction and ultimate failure. Loosening usually takes several years to develop and can occur as late as 10 to 15 years for a cemented implant.
The process of loosening is attributed to failure (cracking) of the cement used to anchor the implant to the bone. It is felt that this cracking is a "fatigue failure" caused by multiple repetitive loads or loads that are excessively high in certain areas.

The risk of loosening in ideal candidates is approximately 3% in 10 to 15 years. In non-ideal candidates such as patients with excessive body weight and younger, more active patients as well as patients who have had a previously failed cemented implant, the chance of loosening increases.

Other possible complications need to be mentioned. Instability can occur due to poor ligament balance. This can cause buckling when weight bearing and may require the use of a knee brace and/or cane. Usually it is not painful. Rarely is revision surgery needed to correct this problem. Instability is relatively rare with only 1-2% having a functional problem.
The knee cap may fail to track properly in it's groove (patellar tracking problems) in 1-5% of patients. This results in a jumping or snapping of the knee cap when the knee is bent. Occasionally complete dislocation can occur. Usually knee cap tracking problems can be managed with exercises and the use of an elastic sleeve. Sometimes corrective surgery is required.

Poor motion of the knee after surgery is another risk. Over 90% of patients after total knee replacement will be able to extend the knee and bend it beyond 90 . In a small percentage of patients internal scarring can result in reduced motion and some pain.

Another complication that may occur is formation of blood clots in the legs or pelvis. There are two potential problems that can result from blood clots: Chronic swelling in the affected leg and serious complications if the clots travel to the lungs (pulmonary embolism). If this occurs, it can be life threatening.

Four different preventative measures can be taken to decrease the risk of blood clot formation. The first is the use of a blood "thinner" (anti-coagulation) like Coumadin in low doses. The second is the use of spinal or epidural anesthesia (sometimes in conjunction with general anesthesia). Third, mechanical pumps (compression stockings) can be used. Finally, early mobilization beginning on the first day after surgery and active in bed exercises such as ankle "pumps" are a helpful. Several of these measures may be used in combination resulting in a less than 10% chance of developing blood clots and a chance of a pulmonary embolus less than 3%. The chance atal pulmonary embolus with this regimen is 1 in 5000.

Other risks of which you should be aware of are: anesthetic risks, the strain of surgery on the heart and lungs, and possible damage to nerves, arteries and veins which can affect the circulation and the function of the leg. All of these occur less than 1% of the time.

Revision total knee replacements require special mention. A revision is defined as a total knee replacement done for a previously failed implant. The chance of success in revision knee replacement is only 80% as compared to 95% for primary procedures. The rate of developing an infection is increased to 4%. Usually the cause for failure has been loosening of the implant from the bone.

We have gone over all of these complications in some detail not to frighten you intentionally, but to inform you of the possible risks of the procedure. Taken in total, the risks are usually quite low and the chances of success greatly outweigh a chance of failure.

CEMENTLESS TOTAL KNEE REPLACEMENT
Because of the increased loosening rates of cemented total knee replacements in the so called "high risk" patients, efforts have been made to develop a way to insert knee replacements without cement. In this country the most popular method has been to achieve fixation by "bone ingrowth". In this case a portion of the component is coated with a porous metal surface and fixation is achieved by bone growing up to and into the pores in the metal.

Animal research began in the mid to late 1970's and use in humans began in the early 1980's. Cementless total knee replacements have not been as successful as the cemented ones. It has been difficult to obtain ingrowth of bone into the tibias component. Mild to moderate pain of unknown cause has been reported in up to 20% of cases. Despite these problems, it still may be advisable to consider a cementless tibial component in patients who are under 50 years of age, or who are excessively obese (over 250 pounds). Cementless femoral components, on the other hand, have performed as well as cemented ones.

Current practice is to decide at surgery if a cementless femoral component can be used. This depends on the quality of the remaining bone and the accuracy of the bone cuts. If a cementless femoral component is used in conjunction with cemented tibial and patellar components, it is called a "Hybrid" total knee.

CONCLUSIONS
It is hoped that this paper has given you some understanding as to the expected benefits, risks and possible alternatives to total knee replacements as well as discuss the new development of cementless total knee replacement. I hope this will have answered some questions for you, but it probably has generated other questions. Please do not hesitate to discuss these with your surgeon.

If you are considering having this surgery, you have adifficult decision ahead of you. It is our feeling you can best make this decision by learning as much as possible about the procedure and the various alternatives. Frequently we are asked what we recommend in an individual case. Usually this is put in the form of "What would you do if this were you, your mother, brother, sister, etc.?" We usually will make a recommendation but we will not make the decision for you. If our mother, father, brother, sister, etc. were faced with the similar problem as yours, we feel we could advise them which decision would be best for them because we know them very well. We know what are their fears, their concerns and their aspirations. Basically, we know a lot about them. If you are a patient of ours, we may know you fairly well, but not well enough to understand all of these factors to allow us to make a decision for you. So please take the time to understand and educate yourself about the problems and various solutions. Only as an informed patient can you made an intelligent decision.