YOUR UNICONDYLAR KNEE REPLACEMENT
 ANDREW A. SHINAR, MD
Vanderbilt University
Arthritis & Joint Replacement Center
The Vanderbilt Village, 1500 21st Ave. South
Nashville, TN 37212
(615) 343-0825
Updated 10/20/02
The purpose of this form is to instruct you on the major aspects of your unicondylar knee replacement surgery, inspire you to ask questions, and inform you of its major risks. We intend this form to neither frighten you, nor to cover up your fears. We hope that it can ensure that you understand the procedure well, and thereby relieve the fears you might have. It is not meant to be complete with regard to every detail of the surgery or its risks. If you would like more information, please ask Dr. Shinar.
Modern knee replacements were developed in the 1970s, and have gone through many changes in technique, implants, and post-operative care since then. We all now benefit from this experience, and understand the procedure and its risks quite well for most surgeries.
Unicondylar knee replacements offer the advantages over standard total knee replacements of having speedier and easier recovery, and better eventual function. They have become more popular lately as information has become available regarding their long-term outcome.
Medicines
- You should stop all aspirin seven days before the surgery.
- Stop all older “non-steroidal” anti-inflammatory drugs (such as Advil, Motrin, Alleve, Naprosyn, etc.) three days prior to the operation.
- You may continue to take the newer anti-inflammatories (such as Celebrex, Vioxx, and Bextra) up to the day of your surgery.
- If you take coumadin or other blood thinners (such as Plavix), please contact your medical doctor to find when it is safe to discontinue these drugs. If your medical doctor feels it is unsafe to stop these drugs, you must inform Dr. Shinar of this, preferably a week before your surgery.
- If you are unsure which to stop, contact Dr. Shinar or your medical doctor.
- All other medications should be continued unless your medical doctor instructs you otherwise. You should ensure that you bring a list of all your medications and their doses to the hospital with you.
- If you regularly drink alcohol, inform Dr. Shinar and your medical doctor.
Medical Clearance
- If you have not seen your medical doctor recently, you should make an appointment with him/her as soon as possible. You can then schedule your surgery once your medical doctor clears you for it.
- If you have recently seen your medical doctor, you should have him/her send a note to Dr. Shinar stating that you are medically fit for your surgery.
- If there is a question as to whether you have been seen recently enough, call your medical doctor.
- If you see a medical specialist (such as a heart or lung doctor), you should have him/her also send a note to Dr. Shinar stating that you are medically fit for your surgery.
- If you have no medical doctor and no medical problems, let Dr. Shinar know.
- If you have no medical doctor and you do have medical problems, let Dr. Shinar know this, and he will refer you to a medical doctor.
- You must inform Dr. Shinar immediately if you have any infection anywhere on your body, especially in the skin over your knee. This can include a pimple or scratch, or an infection of your teeth, fingernails, toenails, or urine.
- If you have any ongoing dental problems or even old infections, you must see your dentist before the operation, and have him/her contact Dr. Shinar.
No one is in absolutely perfect health. Our goals before the surgery are to ensure that your condition is good as it can reasonably be, and that in this condition, you stand the best chance of tolerating the surgery.
Pre-operative Hospital Visit
- You will have blood drawn for testing.
- You will meet an anesthetist. Discuss with him/her your options regarding spinal, general, or epidural anesthesia. All are adequate for Dr. Shinar’s needs. Ask which medications you should take the morning of your surgery.
- Prior to surgery, you may meet Dr. Shinar’s assistants, physical therapists, social workers, and others involved with the process. It is a true team effort.
The procedure involves replacing half of the top of your leg bone and some of the bottom of your thigh bone. These metal and plastic parts along with the rest of your cartilage form your new knee joint. The parts are fixed into your bones with precise fit (“press fit”), and/or bone cement. The muscles and tissues that are moved out of the way are repaired with sutures. The incision, which is usually 3 to 4 inches, is centered over the front of your knee, and is repaired with staples.
If you stay overnight, Dr. Shinar or one of his assistants will see you in the hospital the day after surgery. (If not, you should let the nurses know.)
The medical care while you are in the hospital involves:
- Controlling your pain with pills, or medicine through your veins
- Thinning your blood with drugs and pumping of your feet (with special boots) to help prevent clots
Most often, the post-operative stay goes uneventfully. Rarely, though, patients may need a urinary catheter, blood transfusions, or other medical care.
The physical therapy after the surgery mainly involves safely getting in and out of bed in the hospital, learning how to move your knee, and learning how to walk with the support of a walker or crutches. A machine that moves your knee for you may be placed on your leg. Strengthening exercises are added, as your pain allows. Usually, you will start walking the day of the surgery with assistance of nurses and physical therapists. You may put all your weight on your knee, but should use crutches or a walker for balance.
- The stay in the hospital is usually a few hours. Occasionally, patients stay overnight. If needed, a social worker will determine how much help you need at home, and will contact your insurance company to see what help is covered.
- On going home, you will receive a prescription for pain medication, and instructions regarding a follow-up appointment with Dr. Shinar.
- Dr. Shinar will likely prescribe blood thinners (Coumadin or other) when you leave the hospital, and will monitor the medication’s effect with blood tests. If coumadin is the medication you are receiving, you must make sure that your blood is drawn at home or at a hospital or lab within 2 to 3 days after your discharge. You must also make sure that Dr. Shinar’s assistant or your medical doctor receives the results of your blood tests, and changes the dose of coumadin as needed.
- Staples are removed between 1 and 3 weeks after surgery, either by Dr. Shinar’s assistant or by a nurse who comes to your home.
- Often, Dr. Shinar will place a pain pump that infuses a small amount of numbing medicine into your knee through a very small tube. The nurses in the recovery room will show you how to use it, and how to remove it 2 days after the surgery.
Though the success rate with knee replacement is very high, all surgery involves risks, and there is no guarantee that your surgery will be as successful as you and Dr. Shinar wish it to be.
The main risks include:
- Blood Clots: Clots in your leg veins are very common when blood thinners are not used, but dangerous ones are uncommon when blood thinners or leg compression devices are used. They may hurt or may be silent, and can occur anywhere from your pelvis to your feet. You should let your doctor know when you have pain in any of these regions. The clots can rarely cause long-term problems with the return of blood from your leg to your body, but the main danger with them is that they may dislodge from your leg veins and travel to your lungs. In the lungs, they can be silent, cause severe pain, or even cause your death. If you feel chest pain or have new breathing problems, you should let your doctor know immediately. The risk of these clots causing death has been drastically reduced, and is much less than 1%. The treatment for these clots when they occur is more thinning of the blood with medications, and occasionally with placement of a filter in your veins.
- Infection: Antibiotics given around the time of the surgery greatly decrease this risk, but it still can occur soon after the surgery or even years after the surgery. It is usually treated with another surgery to remove infected tissue or to remove the prosthesis. If removed, the prosthesis can sometimes be replaced, but sometimes cannot. In the end, you may be worse off than if you never had surgery, though this is an uncommon result.
- Stiffness: Sometimes, the healing response can stiffen your knee after surgery even if it was not stiff before surgery. Rarely, it is necessary for Dr. Shinar to manipulate your knee under anesthesia between 2 and 12 weeks after your surgery to improve the motion.
- Nerve Injury: The nerve to your leg and foot can rarely be damaged by the surgery. This nerve may or may not recover by itself. If it does not, you may need a brace for your ankle to walk, and your walking ability could be limited. It is normal for a small area of skin next to the incision to become numb after the procedure. This is usually not bothersome in the long run.
- Bleeding: Rarely, the blood vessels around the knee are damaged by the surgery. Excessive bleeding in the knee and lack of blood flow to the leg occurs after or during the surgery. Extra surgery would be required to correct this problem. Occasionally, blood gathers in the wound even if no major blood vessel is damaged and further surgery (or observation) is required to correct the problem.
- Instability: The knee usually feels stable and strong after the muscles recover, but the ligaments about the knee may stretch or become damaged from the surgery, making the knee feel loose. Occasionally, repeat surgery or a brace is necessary to correct this problem
- Limp: The limp that most people have before the surgery usually persists until the muscles become stronger after surgery. It sometimes never goes away, and sometimes the surgery creates a new limp. Most people, however, note that the way they walk is greatly improved by the surgery.
- Early Failure: Occasionally, the unicondylar knee replacement does not take care of enough of the pain about the knee, and it needs to be converted to a full knee replacement. Also, the cartilage in the rest of the knee can degenerate, requiring full knee replacement.
- Fracture: The bone around the new parts or the parts themselves can break during or after the surgery, requiring bracing or further surgery.
- Need for Further Surgery: Though uncommon, knee replacements occasionally fail before ten years. Some other problems can also make further surgery necessary.
- Inability to Perform Unicondylar Surgery: It is possible that Dr. Shinar would deem it unreasonable to perform a unicondylar knee replacement while attempting to perform the surgery, in which case he would likely perform a total knee replacement.
- Death: Though very rarely, patients have died following knee replacements. This can be due to underlying medical or heart problems that surface or become worse after the surgery. It can also be due to blood clots traveling to the lungs as mentioned above, or from the stress placed on the body by more than the usual amount of bleeding.
- Other Problems: This list is meant to cover only the major problems most frequently encountered. Just as everyone is unique, so are many problems. At this point, it is important to remind you that though complications are numerous and common, most are minor. The surgery is -much more often than not- very effective in reducing pain and improving function. We would not be recommending it to you if it were not.
If a unicondylar knee replacement fails, it can be converted to a total knee replacement. Some bone is lost in the process of the original procedure and its failure, and the total knee replacement following this is more complex. It may involve bone graft, and it may require placement of stems that attach to the knee replacement parts. Though it is more complex than a first time knee replacement, it is not as complex as revision of a complete knee replacement. The eventual outcome of a conversion to a knee replacement is usually quite good.
As the stay in the hospital after unicondylar replacement is usually quite short, most of the therapy as above is performed outside the hospital. We encourage you to be active in working on your motion and function as directed by your physical therapist.
As mentioned, you are never completely safe from the risk of infection.
Measures that you can take to help prevent infection include:
- Telling your doctor immediately of any possible infection anywhere on your body.
- Receiving antibiotics before any dental, urinary, or rectal procedure for two years. You will require pre-procedure antibiotics for a longer period if you have a disease that compromises your immune system. (Call Dr. Shinar if there are any questions.)
Knee replacements usually fail by a gradual process that can occur silently 5 to 25 years after the surgery. Pain is often not present until significant destruction has taken place. Revision surgery can be made more difficult by waiting until after this destruction has occurred. On the other hand, many knee replacements that are loose on x-rays are not painful and function normally for a long time. No uniform protocol as to when you should have repeat x-rays has been universally agreed upon, and your insurance company may not pay for a routine screening visit. Check with Dr. Shinar as to when he wishes you to return to have screening x-rays taken, and check with your insurance company prior to returning. If you develop new pain in your knee, notify Dr. Shinar immediately.
Vanderbilt Orthopaedic Institute
Medical Center East, South Tower, Suite 4200
Nashville, TN 37232-8774
Carolyn Aubrey
615-343-0825
615-322-7556 (Fax)
carolyn.aubrey@vanderbilt.edu
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