Uni-Compartmental Knee Replacement

Introduction      A uni-compartmental knee replacement is an elective surgery, which means patients elect to have a joint replacement done.  As a physician, I never tell patients they have to have their knee replaced.  My philosophy is to give my patients as much information as possible for them to make informed decisions regarding their health and joint pain and let them tell me how and when I can best help them.       The purpose of this web page is to educate patients about the major aspects of knee replacement surgery.  Many studies have shown that an informed patient will have less surprises and be more satisfied with their surgery.  I do not intend to scare people away from getting their knee pain treated.  Although the following information is a reasonable overview of what I consider the major aspects of knee surgery, it is not a substitute for a clinical consultation where I can directly answer your questions. If you would like more information, please schedule an appointment to see me. History of Uni-Compartmental Knee Replacement        Uni-compartmental knee replacements have been used for the past 30 years.  Many different designs have emerged and some poorer designs have disappeared.  Approximately 90% of uni-compartmental knee replacements are for the medial compartment and 10% are for the lateral compartment.  Typically, the other two compartments must have normal articular cartilage to consider replacing just the one arthritic compartment.  The advantages of a uni-compartmental knee replacement are better proprioception (the sense of position of the joint),  intact ACL and PCL ligaments so more normal kinematics, and a quick rehab with less pain.  Only about 10% of patients with arthritis are reasonable candidates for a uni-compartmental knee replacement.        A uni-compartmental knee replacement involves replacing half of the end of the thigh bone (femur) and half of the top of the shin bone (tibia) with metal parts that then act as half of a new knee joint. A plastic (polyethylene) insert is positioned between the 2 metal components to help cushion the new knee joint and allow the knee to bend.  The parts are fixed into your bones with bone cement. The parts are made of cobalt chrome and polyethylene.   For a first time surgery, it is likely that your incision will be 8 cm of about 3 inches in length.  I inform all patients that if I feel that there is arthritis in one of the other two compartments that would typically not be replaced, then I may precede with a total knee replacement during the surgery.  If the ACL is deficient or absence, then a uni-compartmental knee replacement will not work properly and a total knee replacement should be performed.  These facts means that on rare occasions, a patient may wake up from surgery expecting to have a uni-compartmental knee replacement but instead have a total knee replacement.  . Mobile Bearing Uni-Compartmental Knee Replacements (Oxford)      Some orthopedic companies (Biomet) offer knee replacements (Oxford) that allow the components to move inside the knee.  The plastic insert can rotate and move between the femoral and tibial component.  The advantages of this device are that the knee assumes the  rotation and position that best fits that particular patient's need and is not limited by the rotation and position that the surgeon selects in the operating room.  By allowing the liner to rotation, the stress on the plastic is likely decreased which might help the plastic last longer.   Whether this mobile bearing technology will improve the long term survival of the knee replacement remains unknown, but the short term and intermediate term results have been good.  If you are interested in an Oxford uni-compartmental knee replacement, please inquire about whether you would be a good candidate during your office visit with Dr. Kurtz. Pre-operative Joint Replacement Education Class Multiple studies have shown that pre-operative education improves patient’s outcomes after joint replacement surgery. Baptist Hospital offers a free 3 hour pre-operative instructional class.  Although it is not imperative, I strongly recommend that my patients attend this class. During this class, you will meet with the nurses that will be taking care of you after your surgery discuss what you can expect after surgery talk about what you need to bring with you to the hospital discuss whether you plan to go home with a home health nurse visiting you in your house or to an inpatient rehabilitation center The pre-operative joint class is offered Tuesday, Wednesday, and Thursday mornings After the pre-operative joint class, you will meet an anesthetist to discuss with him/her your anesthetic options.  Ask which medications you should take the morning of your surgery Medical Clearance If you have not seen your medical doctor recently, you should make an appointment with him/her as soon as possible. Your surgery can then be performed 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 my office stating that you are medically fit for your surgery. If there is a question as to whether you have seen your medical doctor recently enough, call your medical doctor and ask him or her. If you see a medical specialist (e.g., a heart or lung doctor), have him/her also send a note to my office stating that you are medically fit for your surgery. If you have no medical doctor and no medical problems, let me know during your clinic visit.  If you have no medical doctor and you do have medical problems, I will refer you to a medical doctor prior to any surgery. You must inform my office immediately about any infection anywhere on your body, especially in the skin over your hip. This can include a pimple or scratch, or infection in your fingernails, toenails, teeth, 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 my office. Blood Donation Patients are welcome to donate their own blood at the Nashville American Red Cross prior to surgery with the intention of receiving their own blood after surgery should the need arise.  If you donate your own blood before surgery, please remind me prior to the operation so I can be certain that you receive your own blood. As the likelihood of needing a blood transfusion is relatively low, I neither encourages or discourages pre-operative blood donation. Patients with anemia and relatively low pre-operative blood levels (hematocrit) are more likely to need a post-operative transfusion. Patients with serious medical problems are also more likely need a blood transfusion as well.   Unfortunately, if you donated your own blood, but we do not transfuse it back, that blood will not be given to anyone else and will be thrown out. Medicines You should stop all aspirin seven days before the surgery Stop all “non-steroidal” anti-inflammatory drugs (such as Advil, Motrin, Alleve, Naprosyn, Celebrex  etc.) three days prior to the operation. 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 my office of this, preferably a week before your surgery. If you are unsure whether any drugs you take fall in these categories, contact my office 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 for the pre-operative joint class and anesthesia visit. Day of Surgery Patients are asked not to eat anything for 8 hours before their surgery which typically means nothing after midnight.. Most of your normal medicines should be taken the morning of your surgery with a small sip of water.  Please ask the anesthesiologist at your pre-operative visit which medicines you should take. Patients report to the admission office on the first floor and will be taken up to the 5th floor pre-admission floor. Patients will see me, Dr. Kurtz, in the holding room prior to the operation. Family members can wait in the family waiting room on the 4th floor After the surgery, Dr. Kurtz will update your family members about how the operation went and how you are doing. The patient will typically spend ~ 2 hours in the recovery room before being taken to their hospital room on the 8th floor. Once the patient has been assigned a room, family member can wait in the patient’s room for the patient to arrive. Wound Closure  I feel strongly that the wound closure is as important as the insertion of the components.. I therefore close the surgical incision with both interrupted and running suture in order to help evenly distribute the force on the skin edges. All of the sutures dissolve over the following 6 weeks.  I also apply Dermabond (similar to Super Glue) to the incision after it is closed. The incisions typically do not bleed or drain after surgery. The water-proof dressing that is applied in the operating room typically does not need to be changed, and most patients remove the dressing about a week after the operation. During your hospital stay Pain medicine is custom tailored to every patient's need.. Most patients received both a long acting oral pain medicine and additional short acting oral pain medicine as needed. Patients will receive IV antibiotics for 24 hours after surgery. Patients will receive a blood thinner for about 3 weeks. Patients are encouraged to walk immediately after surgery. Patients are encouraged to shower the day after surgery. Physical therapists will work with each patient multiple times each day helping them learn how to safely walk and work on range of motion. All IVs and catheters are removed once the patient is medically stabilized, usually 1-2 days after surgery. I typically sees every patient at least once a day and often times twice a day.  I also try to round on my patients over the weekend, but occasionally, weekend rounds maybe covered by one of my partners. The hospital stay is usually about 2-3 days. Leaving the hospital A social worker will help determine how much help you need at home, and contact your insurance company to see what help is covered. The physical therapist, social worker, and Dr. Kurtz will help determine whether you might be able to go home, to a rehabilitation facility, or a short-term nursing home. Patients will receive a prescription for pain medication and a blood thinner. If the patient is taking the blood thinner, coumadin, your blood will be drawn at home or at a lab every 3 to 4 days for the next 3 weeks. You must also make sure that Dr. Kurtz’s assistant receives the results of your blood tests, and changes the dose of coumadin as needed. Follow up Patients first follow up is between 2 and 4 weeks after surgery Patients second follow up is ~6 weeks after the first visit.  Patients are then followed on a yearly basis for a 2-3 years.  Every joint replacement patient should have an x-ray of their replacement every 2-3 years regardless if they are having pain or not.        Knee replacements usually fail because the plastic bearing surface wears out, the components loosen, or the components get infected.  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. Appropriate follow up can hopefully identify small problems before them become bigger problems.  If you develop new knee pain, notify my office immediately. Risks of a Uni-Compartmental knee replacement Blood Clots: Blood clots in your leg veins are possible after any surgery on the lower extremities.  The occurrence of blood clots can be minimized with blood thinners, foot pumps, compression stockings, and early mobilization.  The main danger of blood clots is if they dislodge and travel to your veins in your lungs.  This phenomenon is called a pulmonary embolus and can result in respiratory difficulty, chest pain, or even death.  Blood clots may or may not hurt or cause swelling in your leg and can occur anywhere in either leg.  If you have unexplained pain or swelling in your legs, let Dr. Kurtz know as he may order a duplex ultrasound to look for a blood clot.  If you feel chest pain or breathing difficulties, you should call 911 and then call Dr. Kurtz.  The risk of these clots causing death has been drastically reduced, and is less than 0.1%.  The treatment for a proven blood clot is additional blood thinners, and occasionally a filter in your veins. Infection: Antibiotics are given before and after surgery to decrease the risk of infection, but an infection still can occur immediately or even years after the surgery. It is usually treated with another surgery to remove infected tissue and often the prosthesis as well. If the components are removed, a revision knee prosthesis can sometimes be inserted months later if the infection clears, but sometimes the patient is left without a knee joint or a knee fusion.  Although patients rarely have life threatening problems from their joint infection, an infection is a devastating complication. Arthritis Progression in other compartments:  One of the possible complications of a uni-compartmental knee replacement is that the other normal compartments of the knee may develop arthritis and pain over time.  If arthritis progresses elsewhere in the knee, a total knee replacement may need to be performed to alleviate pain in the native compartments. Stiffness: Patients may experience stiffness in the knee joint after surgery.  Usually, a stiff knee before surgery is more likely to remain stiff after surgery; however, any knee can lose motion after surgery.  It is imperative that patients work hard with the physical therapist after surgery to prevent the knee from getting stiff.  Occasionally, the patient must have their knee manipulated under anesthesia to regain the motion lost in the post-operative period. Component Loosening: Occasional the bone will not grow into the implanted components.  The components may loosen and change position.  Component loosening can occur years after the surgery from wear debris from the plastic liner.  The motion of the loose component may cause pain and require another surgery to revise the components.  Nerve Injury: Although extremely rare, nerves to your leg and feet.  These nerves may or may not recover by themselves. If they do not, you may need a brace for your ankle, and your walking ability could be limited. Bleeding: Rarely, the blood vessels around the knee are damaged by the surgery and excessive bleeding occurs after or during the surgery, requiring either surgery or special procedures under X-ray control to correct the problem. Occasionally, blood gathers in the knee even if no major blood vessel is damaged and further surgery (or observation) is required to correct the 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. Fracture: The femur, patella, or tibia can crack when preparing the bone for insertion of the components, actually inserting the components, or even years after the surgery. Fractures usually are treated with metal cables or a plate, and usually heal. Osteolysis: Polyethylene bearings can wear over many years and cause osteolysis which is the body's response to the plastic wear debris from the knee replacement.  The body tends to attack the tiny plastic particles and inadvertently causes the bone around the knee joint to weaken.  The weakened bone can lead to fractures or component loosening. Dislocation: The femoral component rarely can dislocate from the tibia component.   Knee replacements with a mobile bearing can also dislocate if the bearing surface rotates more than it should.  If your uni-compartmental knee dislocates, a surgeon will manipulate your leg under anesthesia or sedation to place the components back together. Occasionally, unstable knee replacements need to be revised to correct this condition if it keeps occurring. Need for Further Surgery: Though uncommon, uni-compartmental knee replacements occasionally fail sooner than expected. Some other problems can also make further surgery necessary, including: bone forming where it should not, breaking of the bone around the prosthesis (during or after surgery), and irritation of the soft tissues by wire or sutures. Death: Though very rarely, patients have died following knee replacements. This can be due to underlying medical or heart problems that arise or worsen 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. It is important to remind patients that though numerous complications have been reported in the literature, most are minor and rare.  I would not recommend it to you if the typical results were not outstanding. Measures that you can take to help prevent complications  include: Telling your doctor immediately of any possible infection anywhere on your body.  Also let my office know. 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 my office if there are any questions.) Always mention to any doctor performing an invasive procedure on you that you have a hip replacement.