Knee Replacement Surgery

Knee

Total Knee Replacement is sometimes recommended for advanced stage arthritis that does not respond to nonoperative treatments. A Partial or Total Knee Replacement is a surgical procedure which involves the replacement of the worn-out parts of the knee with an artificial joint. A total knee replacement implies that everything about the joint is being replaced – which isn’t true. What is actually being done is just a resurfacing of the bones of the joint. The prosthesis that is used is made up of plastic and metal and is placed on the joint surface of each bone. Most of the ligaments and all of the tendons remain intact. This allows the bones to glide against each other and allow the knee to bend and move without pain.

Why Knee Replacement?

It is important for you to realize that this is an elective surgical procedure which means that you have to choose it. It’s not absolutely essential, although almost certainly you would be improved by it as long as there are no major complications.

The main thing that we would like to achieve and the main purpose for doing a total knee replacement is to reduce your discomfort. We would expect that most people who have a total knee replacement would have either no pain whatsoever, or very minimal occasional pain which would not require any medication. Obviously, there are a lot of things that can cause discomfort around the knee that have nothing to do with a knee replacement. We do not replace tendons, ligaments, or muscles. All of these can possibly be the source of discomfort. Many times this type of pain can be controlled with anti-inflammatory medication and, if you are taking that type of medication now, it’s possible that you may still need to take that medication after the operation.

Preparing for Knee Replacement Surgery – What Should You Expect?

Blood Transfusion

Many patients who have a knee replacement will require blood transfusion. If you are donating blood for your surgery, you will be asked to donate one or two units of your own blood within 35 days prior to your surgery date. This will involve scheduling an appointment with the blood bank of the hospital, or if necessary, a blood donation facility recommended by your insurance carrier or one closer to where you live (for out-of-state patients). Only one unit of blood can be donated at a time, so you may need to come in for two visits. The blood is then stored until your operation.

If you are unable to donate blood, for whatever reason, donor blood will be used in your case, if necessary. People have expressed some concern about blood transfusion because of the risk of transmitting diseases. Donor blood is carefully screened for communicable diseases. With the new technology, the risk of hepatitis and HIV infection is extremely low. To our knowledge, disease transmission through use of donated blood has never occurred in any of our patients. However, there is no question that your own blood is the safest. Therefore, if you are able, we recommend that you donate blood for your surgery. If you’re coming a long way, arrangements can be made to have you give blood locally and have it transported here for your surgery. Please be assured that blood that you give will be given back to you, if needed.

Pre-admission Testing

Within two weeks prior to your surgery, you will be asked to undergo several laboratory tests and possibly an electrocardiogram and chest x-ray. This is called pre-admission testing. This will help us to tell whether there are any conditions which might increase the risk of surgery. A physical examination, performed by your own medical doctor or hospital staff here, is also a part of pre-admission testing.

Just Before Surgery

You will not be allowed to drink or eat anything after midnight and on the morning of the surgery. In some cases, you may be allowed to take a medication you normally take in the morning with a minimal amount of water. If instructed to do so, you will need to let the admitting nurse know that you have done this.

When you come into the hospital on the day of surgery, you may have some additional x-rays that might not have been taken previously and have a physical examination by your surgeon or resident. If you have not already done so, you will be asked to sign an operative consent form to state that you understand what is being proposed and that you are in agreement that we may proceed with the operation. Just prior to surgery, an intravenous line will be started and you will be taken into the operating suite.

Anesthesia

You will be seen by an anesthesiologist on the morning of surgery. The anesthesiologist can answer specific questions you might have. Most of our surgeries are performed under spinal anesthesia. This is a very safe form of anesthesia. It is safer than general anesthesia, which is one of the reasons why we recommend it. Spinal anesthesia disturbs the major body functions a lot less than general anesthesia. Unless there are some specific reasons why a spinal anesthetic should not be used in your case, this is our preferred method of anesthesia.

The anesthesiologist will give you some medication to make you sleepy so that you’re not really aware of what’s going on in the operating room. You will not be totally asleep either. However, the area that will be operated on will be totally numb throughout the operation and for several hours after the surgery.

Knee

The Surgery

As stated before, the surgery involves the removal of all of the damaged bone and cartilage. This is done with saws and drills much like a carpenter uses. The next step is to prepare the bone for the prosthesis. This involves using specialized tools to make precise cuts and to shape the bone so that the prosthesis will fit properly. The artificial joint is then placed into the bone with or without bone cement. The surgery itself takes between two to three hours, depending on the complexity of your case. It may depend on how many previous surgeries you’ve had, how badly deformed your knee is, how mobile it is, etc., as to how long it will take. The length of time is not really very important.

Total knee prostheses can be attached to the bone using a material called methylmethacrylate or, more simply, bone cement. With proper technique,this gives an immediate fixation of the prosthesis to the bone. Another method is called biologic fixation. This method requires that the surface of the prosthesis next to the bone is porous. With time, bone grows into the pores and the prosthesis becomes an integrated part of the joint. There are advantages and disadvantages to each type of “fixation.” Furthermore, the type of fixation recommended to you will depend on your age, weight, and activity level.

Recovery Room

When your surgery is completed, you will go to the recovery room where you will be closely monitored until the effects of the anesthesia and intra-operative medicines are decreased and you are relatively awake and comfortable.

Orthopaedic Unit

When you have completed your stay in the recovery room, you will be transferred to your hospital room in the orthopaedic nursing unit. You will be lying on your back in a comfortable position. If you have surgery early in the morning, you may sit up on the edge of the bed that evening. In general, all patients are out of bed within twenty-four hours and attending physical and occupational therapy. The therapists will instruct you in learning how to use crutches or a walker and being taught some of the precautions that are necessary in the immediate post-operative period. The physical therapist will answer any of your questions and will go over all of the details.

Risks

It is important that you understand that there are risks associated with any major surgical procedure and total knee replacement is no exception. This section is not meant to alarm you but you really do need to know these kinds of things in order to make the decision as to whether you wish to proceed with a total knee replacement. These risks include the risk of death. That’s true of any major surgical procedure requiring anesthesia and blood transfusion. The risk of death in our hospital for total knee replacement is in the order of 1 per 1,000 cases so that you can see that the risk is very small, but it’s not 0. The specific risk for you will depend upon your general medical condition, your age, and the difficulty of the surgical procedure, but the risk of death itself is really very small.

Although precautions are taken, there are other potential risks that need to be taken into account. These include infection, limitations in knee motion, and loosening of the prosthesis. Although these do not occur frequently, you should be aware that they could occur.

A major potential risk is the risk of infection. Again, in this hospital, the risk of infection is in the order of 1/2% or less. 1/2% would be 1 case in 200 and, in our hospital, the risk is actually 1 case in 400. You will be receiving an antibiotic on the morning of surgery and this will be continued for 24-36 hours after surgery. There are other preventive measures that will also be undertaken to reduce the possibility of infection. In spite of these, a very small percentage of patients will develop an infection and that generally can be treated by antibiotics and cured. This would require longer hospitalization, treatment with antibiotics for a longer period of time, perhaps opening and draining of the knee and, in some instances, perhaps even removal of the artificial components themselves in order to cure the infection after which another knee replacement could be implanted. There is also some risk of an infection elsewhere in your body after the surgery settling in the knee and therefore we strongly recommend that patients who have total joint replacement take antibiotics whenever they have infections in another area and particularly if they are going to have extensive dental work. Antibiotics do not need to be taken for routine cleaning or simple fillings. We will provide you with a card indicating what needs to be done if you can give this to your doctor or to your dentist should that be necessary.

Another risk of total knee replacement is that the motion of the knee may be more limited than before the surgery. To a certain extent, how well your prosthesis moves after it’s put in will depend upon how much your knee moved before the operation. People with very stiff knees before the operation may not get as much motion as patients without stiff knees. In addition, some people whose knees moved easily before the operation may actually lose some motion after the operation. However, the important thing to understand is that it is motion without pain that is important. If there is a lot of motion before the operation but it is painful and after the operation there is some limitation of motion but it is pain-free, this is an improvement. We would like the knee to move to about 105°. This makes it easy for the patient to get up and down stairs and go up and down out of a chair quite easily. This will be one of the things that you will be required to do in the post-operative period. Physical therapy, both in the immediate post-operative period and after you go home, is very important. It’s important to recognize that this is not something that is just going to come your way without any participation on your part. You will have to extend some effort to get the best possible result. We will be asking you to move your knee in the post-operative period. We will be asking you to work on strengthening your muscles. If, in about 10 days, you are not getting your knee to 90°, a right angle, we may recommend a manipulation. A manipulation means that you would be put to sleep and your knee would be passively, physically bent for you. This could break down some adhesions (scar tissue) that might have formed around your knee after the surgery.

One of the things that could occur is the loosening of the prosthesis. This loosening would not happen suddenly, but it would be a gradual process and it would be characterized by discomfort. In most instances, if a prosthesis becomes loose, it can be corrected but that usually means further surgery. Now what is the nature of this risk? That depends on several circumstances. We think in general, it’s probably a cumulative risk of about 1% per year, so that if you have your prosthesis for 20 years, the possibility of loosening over that 20 years could be as high as 1 in 5. If you have your prosthesis for 10 years, it could be 10%. However, improvements in the instruments, prostheses, and the surgical techniques used today may result in a reduction in the risk of loosening.

Now there is a host of other possible complications if you review series of several thousand you will see literally dozens of possible complications that could take place but take place with exceeding rarity. Things such as muscle ruptures, pulling off of the tendon, injuries to nerves and blood vessels, superficial infection and opening of the wound, and other things of this nature may occur. They don’t occur very often, but they can occur.