William Kurtz, M.D. - Joint Replacement Surgeon
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Uni-Compartmental Knee Replacement

Introduction

A uni-compartmental knee replacement is involves replacing one or sometimes two of the three compartments in the knee joint.  This surgery preserves the cruciate ligaments and allows for a quicker recovery and more normal feeling knee joint.  About 5-10% of patients are candidates for a partial knee replacement.

History of Uni-Compartmental Knee Replacement

Uni-compartmental knee replacements have been implanted for the past 30 years. Many different designs have emerged and some poorer designs have disappeared. Approximately 80% of uni-compartmental knee replacements are for the medial compartment, 10% are for the lateral compartment, and 10% are for the patella femoral compartment. Typically, the other two compartments that are not replaced 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. I inform all patients who want a uni-compartment knee replacement that if I feel that there is too much arthritis in the rest of the knee joint then I would intra-operatively switch to a total knee replacement. 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.

Custom Partial Knee Replacement (Uni-compartmental or Bi-compartmental)

A custom partial knee replacement is now an available from Conformis where the size, shape and curvature of the patient's knee is determined from a pre-operatvie scan. Those computer images are then electronically sent to the company so that they can manufacture an implant with the identical shape as your existing knee. The custom implant is shipped back to the surgeon 6 weeks later for the patient's surgery.

Pre-operative Joint Replacement Education Class

  • Multiple studies have shown that pre-operative education improves patient's outcomes after joint replacement surgery
     
  • Baptist and Centennial Hospital offer a free 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
  • After the pre-operative joint class, you will meet an anesthetist to discuss with him or 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 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 encourage or discourage pre-operative blood donation.

  • Patients with pre-operative anemia (low hematocrit) are more likely to need a post-operative transfusion and should have their anemia worked out prior to surgery.  Sometimes, these anemic patients will take ProCrit prior to surgery to boast their blood counts.

  • Patients with serious medical problems are also more likely need a blood transfusion.

  • Unfortunately, if you donated your own blood and we do not give it back to you, your stored blood will be thrown out.

Medicines

  • When possible, please stop aspirin seven days before the surgery

  • I personally do not mind patients continuing their  "non-steroidal" anti-inflammatory drugs (such as Advil, Motrin, Alleve, Naprosyn, Celebrex  etc.); however, other surgeons might.
  • 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 asap.
  • 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 usually around 6 am for a morning case and 8 am for an afternoon case.
  • I see all patients in the holding room prior to the operation and answer any questions that may arise.

  • After the surgery, I will update your family members about how the operation went and how you are doing.

  • Patients will typically spend about 2 hours in the recovery room before being taken to their hospital room, but there is some variability based on room availability and the patient's recovery from anesthesia.

Wound Closure

  • I feel strongly that the wound closure is as important part of the case as the implantation 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

  • The incisions typically do not bleed or drain after surgery

  • The water-proof, bactericidal dressing is applied in the operating room and is typically removed a week after the operation.

During Your Hospital Stay

  • Pain medicine is custom tailored to every patient's need

  • Most patients received an oral pain medicine (Percocet or Lortab) every 4 hours as needed and IV morphine every one hour as needed for breakthrough pain.

  • Patients will receive IV antibiotics for 24 hours after surgery

  • Patients will receive a blood thinner for 2-3 weeks

  • Patients are typically encouraged to walk immediately after surgery

  • Patients are encouraged to shower the day after surgery

  • Physical therapists will work with each patient twice a day helping them learn how to safely walk and work on range of motion.

  • All IVs and catheters are typically  removed the morning after surgery.

  • I see my patients 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 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

  • The patient's first follow up is around 4 weeks after surgery and then a couple months later
  • Patients are seen one year after their surgery for an xray and then every 4 - 5 years after that.

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

Partial or uni-compartmental knee replacements have a slightly higher rate of revision surgery than total knee replacements. This is due in part to the fact that the revision of a partial knee replacement is often easier than the revision of a toal knee replacement, so surgeons and patients are more willing to have this revision surgery done. Another reason is because the partial knee replacements maintains part of the cartilage in the knee which can wear out over time. The partial knee repalcements also have smaller components and less surface area so they may be more prone to loosening.

  • 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 typically hurt and cause swelling in your 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 with blood thinners, and is less than 0.1%. The treatment for a proven blood clot is additional blood thinners, and occasionally a filter in your vein.

  • Wound Complications: Occasionally, a knee replacement patient may have some drainage following their surgery. This drainage is often brouught on by the blood thinners we have to use. If you have drainage, inform Dr. Kurtz's office immediately. Often I will keep the patient's leg straight with a knee immobilizer, and hold off on the blood thinners for a few days. Sometimes, patients need a repeat operation to wash out the blood from their knee joint.

  • 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 occasionally the prosthesis as well. If the components are removed, a revision knee prosthesis can 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 can be a devastating complication.

  • Arthritis Progression in other compartments: One of the possible complications of a uni-compartmental knee replacement is that the other non-replaced compartments of the knee may develop arthritis and pain over time. If arthritis progresses elsewhere in the knee, a total knee replacement may be needed to alleviate the knee pain.
     
  • 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 implanted components may loosen from the bone 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 activity-related pain and require another surgery to revise the components.
     
  • Nerve Injury: Most knee replacements have some numbness on the lateral side of the incision for a few months. This numbness does not typically cause the patients any discomfort or grief. Although extremely rare, nerves to your feet may be injuried during surgery. These nerves may or may not recover by themselves.
     
  • Bleeding: Rarely, the blood vessels around the knee may be damaged by the surgery and excessive bleeding may occur after or during the surgery. In these situations, additional surgery may be required to correct the problem. Occasionally, blood gathers in the knee joint (hematoma) and slowly leaks out of the wound and requires a wash out procedure to get the wound to stop bleeding.
     
  • Limp: The pre-operative limp that many people have usually persists for 2-3 months until the muscle strength improves. Occasionally, knee replacement surgery creates a new permanent limp.
     
  • Fracture: The femur, patella, or tibia can crack during surgery when the surgeon is preparing the bone or actually inplanting the components. Fractures can also occur years after the surgery from minor trauma. Fractures usually are treated with metal plates and screws and sometimes a revision knee replacement.
     
  • 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 the surgery.

  • Other Problems: This list is meant to cover only the most frequently encountered problems. Just as everyone is unique, so are many problems.  Although numerous complications have been reported in the literature, most are minor and rare. 

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
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