Total Knee Replacement (TKR)
Total knee replacement, also called total knee arthroplasty, is a surgical procedure in which the worn out or damaged surfaces of the knee joint are removed and replaced with artificial parts. The knee is made up of the femur (thigh bone), the tibia (shin bone), and patella (kneecap). The meniscus, the soft cartilage between the femur and tibia, serves as a cushion and helps absorb shock during motion. Arthritis (inflammation of the joints), injury, or other diseases of the joint can damage this protective layer of cartilage, causing extreme pain and difficulty in performing daily activities. Your doctor may recommend surgery if non-surgical treatment options have failed to relieve the symptoms.
Total knee replacement surgery is commonly indicated for severe osteoarthritis of the knee. Osteoarthritis is the most common form of knee arthritis in which the joint cartilage gradually wears away. It often affects older people.
In a normal joint, articular cartilage allows for smooth movement within the joint, whereas in an arthritic knee the cartilage itself becomes thinner or completely absent. In addition, the bones become thicker around the edges of the joint and may form bony “spurs”. All of these factors can cause pain and restricted range of motion in the joint.
Your doctor may advise total knee replacement if you have:
- Severe knee pain which limits your daily activities (such as walking, getting up from a chair or climbing stairs).
- Moderate to severe pain that occurs during rest or awakens you at night.
- Chronic knee inflammation and swelling that is not relieved with rest or medications
- Failure to obtain pain relief from medications, injections, physical therapy, or other conservative treatments.
- A bow- legged knee deformity
The exact cause of osteoarthritis is not known, however there are a number of factors that are commonly associated with the onset of arthritis and may include:
- Injury or trauma to the joint
- Fractures at the knee joint
- Increased body weight
- Repetitive overuse
- Joint infection
- Inflammation of the joint
- Connective tissue disorders
Your doctor will diagnose osteoarthritis based on the medical history, physical examination, and X-rays.
X-rays typically show a narrowing of the joint space in the arthritic knee.
The goal of total knee replacement surgery is to relieve pain and restore the alignment and function of your knee.
The surgery is performed under spinal or general anesthesia. Your surgeon will make an incision in the skin over the affected knee to expose the knee joint. Then the damaged portions of the femur bone are cut at appropriate angles using specialized jigs. The femoral component is attached to the end of the femur with or without bone cement. The surgeon then cuts or shaves the damaged area of the tibia (shinbone) and the cartilage. This removes the deformed part of the bone and any bony growths, as well as creates a smooth surface on which the implants can be attached. Next, the tibial component is secured to the end of the bone with bone cement or screws. Your surgeon will place a plastic piece called an articular surface between the implants to provide a smooth gliding surface for movement. This plastic insert will support the body’s weight and allow the femur to move over the tibia, similar to the original meniscus cartilage. The femur and the tibia with the new components are then put together to form the new knee joint. To make sure the patella (knee cap) glides smoothly over the new artificial knee, its rear surface is also prepared to receive a plastic component. With all the new components in place, the knee joint is tested through its range of motion. The entire joint is then irrigated and cleaned with a sterile solution. The incision is carefully closed, drains are inserted and a sterile dressing is placed over the incision.
Rehabilitation begins immediately following the surgery. A physical therapist will teach you specific exercises to strengthen your leg and restore knee movement. Knee immobilizers are used to stabilize the knee. You will be able to walk with crutches or a walker. A continuous passive motion (CPM) machine can be used to move the knee joint . Continuous passive motion is a device attached to the treated leg which constantly moves the joint through a controlled range of motion, while the patient relaxes. Your physical therapist will also provide you with a home exercise program to strengthen thigh and calf muscles.
Use of the GameReady Device
Risks and complications
Total knee replacement surgery is considered major surgery, but every precaution is taken to make the procedure as safe as possible. As with any surgical procedure, there are risks with being placed under anesthesia. You will meet the anesthesiologist taking care of you prior to the surgery and be able to discuss the specific risks of anesthesia.
Bleeding is an expected risk of surgery, as your bone is a vascular structure. Cutting the bone, removing bone spurs, and inserting an implant will cause blood loss. Since a tourniquet is used during surgery, the blood loss often occurs after surgery. Dr. Su uses special techniques to reduce blood loss, minimizing your risk of transfusion. Certain patients will still need a blood transfusion after surgery, particularly if you are anemic, or are having both knees replaced. If you believe you may need a blood transfusion after surgery, you can pre-donate your own blood so that you can receive it after surgery.
There is a risk of formation of blood clots after total knee replacement surgery, so it is necessary that you use a blood thinner. Generally, these medications are used temporarily after surgery, to protect you from dangerous blood clots. In addition, moving around during your recovery, as soon as possible, will help decrease the risk of clots.
Infection is always a risk when an implant is involved. An infection can occur immediately after surgery, or years after the surgery. Infection rates are lowest at hospitals that perform the most surgery; Hospital for Special Surgery has performed more knee replacement surgeries than any other hospital in the world. After your recovery, it is also important to let your health care providers know that you have an artificial knee, so that you can take precautions to prevent late infections. You should make certain your dentist knows that you have an implant, because you will have to take antibiotics prior to any dental work.
The knee is prone to scar tissue formation after surgery, particularly if you are immobilized. It is essential that you begin bending and extending your knee immediately after surgery. This will help minimize the formation of scar tissue; if you do not bend or extend your knee sufficiently by the time of your first postoperative visit, you may need an outpatient procedure called a manipulation, in order to break up scar tissue. If you are unable to achieve full motion, you will have difficulty walking and negotiating stairs.
A knee implant is our best method of treating severe arthritis; however, it is an artificial joint, and cannot completely recreate the natural knee joint. Therefore, there can be the sensation that the knee implant does not feel like one’s own knee; also, on occasion, there can still be pain around a total knee replacement.
It is common that there will be residual numbness on the outside of the skin incision. At times it will diminish over the course of recovery; other times, it may be permanent. Generally, this does not bother patients nor limit them.
Despite these risks, total knee replacement is generally very successful and these complications can all be managed.
Rapid Recovery TKR
Dr. Su has been researching methods to improve and enhance the recovery from TKR ever since his training was completed in 2003. As patients typically experience pain and swelling after TKR surgery, Dr. Su has been investigating ways to diminish these sensations so that recovery can be more rapid. This includes: pre-emptive analgesia, performed by the anesthesiologist prior to surgery. This means that, in anticipation of postoperative pain, the nerves supplying the knee are blocked with local anesthetic before the incision is carried out. Medications such as an anti-inflammatory medication are also given prior to surgery to aid in this goal.
The surgical technique for TKR is also carried out in a less invasive way than traditional knee replacement was performed 10 to 15 years ago. Rather than the long, 12-inch incision that was performed, a smaller incision usually measuring about 5-6 inches can now be made. The extensor mechanism (made up of the quadriceps tendon, patella, and patellar tendon) used to be flipped over during the surgery, placing tension on these structures and potentially leading to more pain; this is no longer done during the surgery.
Smaller instruments are used during the surgery also, to allow for it to be performed through a smaller incision. All of these modifications add up to less surgical trauma during the operation and a theoretically quicker recovery.
At the conclusion of the operation, Dr. Su also minimizes the amount of bleeding and swelling that a patient experiences. He is using combination of hemostatic agents that decrease blood loss after the operation, which reduce the blood transfusion rate postoperatively and may diminish the collection of blood in the knee. Reducing swelling may reduce post-surgical pain and improve knee range of motion.
Finally, Dr. Su has studied the benefits of a cooling and compression device on the knee after TKR surgery. The GameReady™ device, which is a portable cryopneumatic device, gently squeezes and cools the knee, and has been shown to decrease the amount of narcotic pain medication needed after TKR surgery.
Although in general, TKR surgery recovery can be difficult and painful, Dr. Su and his team are doing everything they can to promote a more rapid recovery.
Computer Navigated TKR
Dr. Su is one of a handful of surgeons who uses computer navigation for all of his knee replacement operations. Computer navigation is an enabling technology that provides real-time, intraoperative information to a surgeon, in order to perform the operation with greater precision.
During a knee replacement, a surgeon must cut the bone of your femur and tibia at precise angles in order to create a well-aligned joint afterwards. Surgeons believe that the better a total knee replacement is aligned, the longer it may last and the better it may function. Unfortunately, the current tools that are used by most surgeons to perform a knee replacement are rather rudimentary and often lead to “outliers”. In fact, many studies have shown that even experienced surgeons will have up to a 30-40% rate of outliers, where the total knee replacement is greater than 3o from where it was intended.
Computer navigation, because it is able to provide information to the surgeon during the operation about how instruments are aligned, is able to reduce the rate of outliers dramatically. In a study that Dr. Su was involved with, when computer navigation was used, 96% of total knee replacements were within +/- 2o of the intended target. Thus, the number of outliers were cut down by a factor of 7!
Researchers in Australia have now demonstrated that a TKR that was performed with computer navigation has a better chance of survival (free from another operation) at 10 years, as compared to total knee replacements performed without computer navigation.
Dr. Su continues to work closely with Orthalign, Inc, the company that manufactures the KneeAlign computer navigation system, in order to refine and improve this technology.