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Knee replacement, also known as knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve pain and disability. It is most commonly performed for osteoarthritis and also for other knee diseases such as rheumatoid arthritis and psoriatic arthritis. In patients with severe deformity from advanced rheumatoid arthritis, trauma, or long-standing osteoarthritis, the surgery may be more complicated and carry higher risk. Osteoporosis does not typically cause knee pain, deformity, or inflammation and is not a reason to perform knee replacement
Other major causes of debilitating pain include meniscus tears, cartilage defects, and ligament tears. Debilitating pain from osteoarthritis is much more common in the elderly.
Knee replacement surgery can be performed as a partial or a total knee replacement. In general, the surgery consists of replacing the diseased or damaged joint surfaces of the knee with metal and plastic components shaped to allow continued motion of the knee.
The operation typically involves substantial postoperative pain, and includes vigorous physical rehabilitation. The recovery period may be 12 weeks or longer and may involve the use of mobility aids (e.g. walking frames, canes, crutches) to enable the patient’s return to preoperative mobility. It is estimated that approximately 82% of total knee replacements will last 25 years.
REVISED KNEE REPLACEMENT SURGERY
In order for a total knee replacement to function properly, an implant must remain firmly attached to the bone. During the initial surgery, it was either cemented into position or bone was expected to grow into the surface of the implant. In either case, the implant was firmly fixed. Over time, however, an implant may loosen from the underlying bone, causing the knee to become painful.
The cause of loosening is not always clear, but high-impact activities, excessive body weight, and wear of the plastic spacer between the two metal components of the implant are all factors that may contribute. Also, patients who are younger when they undergo
the initial knee replacement may “outlive” the life expectancy of their artificial knee. For these patients, there is a higher long-term risk that revision surgery will be needed due to loosening or wear.
In some cases, tiny particles that wear off the plastic spacer accumulate around the joint and are attacked by the body’s immune system. This immune response also attacks the healthy bone around the implant, leading to a condition called osteolysis. In osteolysis, the bone around the implant deteriorates, making the implant loose or unstable.
Infection is a potential complication in any surgical procedure, including total knee replacement. Infection may occur while you are in the hospital or after you go home. It may even occur years later.
If an artificial joint becomes infected, it may become stiff and painful. The implant may begin to lose its attachment to the bone. Even if the implant remains properly fixed to the bone, pain, swelling, and drainage from the infection may make revision surgery necessary.
An antibiotic spacer placed in the knee during the first stage of treatment for joint replacement infection.
Revision for infection can be done in one of two ways, depending on the type of bacteria, how long the infection has been present, the degree of infection, and patient preferences.
If the ligaments around your knee become damaged or improperly balanced, your knee may become unstable. Because most implants are designed to work with the patient’s existing ligaments, any changes in those ligaments may prevent an implant from working properly. You may experience recurrent swelling and the sense that your knee is “giving way.” If knee instability cannot be treated through nonsurgical means such as bracing and physical therapy, revision surgery may be needed.
Sometimes a total knee replacement may not help you achieve the range of motion that is needed to perform everyday activities. This may happen if excessive scar tissue has built up around the knee joint. If this occurs, your doctor may attempt “manipulation under anesthesia.”
In this procedure, you are given anesthesia so that you do not feel pain. The doctor then aggressively bends your knee in an attempt to break down the scar tissue. In most cases, this procedure is successful in improving range of motion. Sometimes, however, the knee remains stiff. If extensive scar tissue or the position of the components in your knee is limiting your range of motion, revision surgery may be needed.
A periprosthetic fracture is a broken bone that occurs around the components of a total knee replacement. These fractures are most often the result of a fall, and usually require revision surgery.
In determining the extent of the revision needed, your doctor will consider several factors, including the quality of the remaining bone, the type and location of the fracture, and whether the implant is loose. When the bone is shattered or weakened from osteoporosis, the damaged section of bone may need to be completely replaced with a larger revision component.
Preparing for Surgery
You will be asked to schedule a complete physical examination with your primary care doctor several weeks before revision surgery. This is needed to make sure that you are healthy enough to have the surgery and complete the recovery process. Patients with chronic medical conditions, like heart disease, may also be evaluated by a specialist, such as a cardiologist, before surgery
Imaging tests. Your doctor will usually order imaging tests to learn more about the condition of your knee.
Laboratory tests. To determine whether you have an infection, your doctor may order blood tests. He or she may also aspirate your knee. In this procedure, joint fluid is removed using a needle and syringe, then analyzed in a laboratory to determine if infection is present.
Because your mobility will be limited after surgery, you will need help for several weeks with such tasks as cooking, shopping, bathing, and doing laundry if you live alone.
Your doctor’s office, a social worker, or a discharge planner at the hospital can help you make advance arrangements to have someone assist you at home. Depending on your condition, you may need to stay at a nursing facility or rehabilitation center for some time after you leave the hospital. Your healthcare team can also help you arrange for a short stay in an extended care facility during your recovery, if needed.
As with any surgical procedure, there are risks associated with revision total knee replacement. Because the procedure is longer and more complex than primary total knee replacement, it has a greater risk of complications. Before your surgery, your doctor will discuss each of the risks with you and will take specific measures to help avoid potential complications.
The possible risks and complications of revision surgery include:
You will most likely be admitted to the hospital on the day of surgery.
After admission, you will be evaluated by a member of the anesthesia team. The most common types of anesthesia are general anesthesia (you are put to sleep) or spinal, epidural, or regional nerve block anesthesia (you are awake but your body is numb from the waist down). The anesthesia team, with your input, will determine which type of anesthesia will be best for you.
Revision total knee replacement is more complex and takes longer to perform than primary total knee replacement. In most cases, the surgery takes from 2-3 hours.
To begin, your doctor will follow the line of the incision made during your primary total knee replacement. The incision may be longer than the original, however, to allow the old components to be removed. Once the incision is made, the doctor will move the kneecap and tendons to the side to reveal your knee joint.
Your doctor will examine the soft tissues in your knee to make sure that they are free from infection. He or she will assess all the metal and/or plastic parts of the prosthesis to determine which parts have become worn or loose or shifted out of position.
Your doctor will remove the original implant very carefully to preserve as much bone as possible. If cement was used in the primary total knee replacement, this is removed, as well. Removing this cement from the bone is a time-consuming process that adds to the complexity and length of the revision surgery.
After removing the original implant, the doctor will prepare the bone surfaces for the revision implant. In some cases, there may be significant bone loss around the knee. If this occurs, metal augments and platform blocks can be added to the main components to make up for the bony deficits.