Knee replacement


Total Knee arthroplasty, is a surgical procedure to replace the weight-bearing surfaces of the knee joint to relieve the pain and disability of osteoarthritis or other knee diseases such as rheumatoid arthritis and psoriatic arthritis, or deformity from trauma;

Total knee arthroplasty does not typically reduce mortality.

TKA results in marked improvement in health-related quality of life, functional status and is highly cost-effective.

Other major causes of debilitating pain include meniscus tears, cartilage defects, and ligament tears.

Other causes of cartilage destruction include hemophilia, seronegative arthritides, crystal deposition diseases, pigmented villonodular synovitis, idiopathic or steroid-induced avascular necrosis, and bone dysplasias.

Knee replacement surgery can be performed as a partial or a total knee replacement.

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.

Initially the damaged cartilage surfaces at the ends of the femur and tibia are removed along with a small amount of underlying bone, they are then replaced with metal components that recreate the surface of the joint.

The metal parts may be cemented or press-fit into the bone and the undersurface of the patella is cut and resurfaced with a plastic button.

To create a smooth gliding surface a plastic spacer is inserted between the metal components.

The operation involves substantial postoperative pain, and includes vigorous physical rehabilitation.

Approximately 600,000 total knee arthroplasty performed every year in the United States.

In 2012 more than 670,000 totally knee replacements were performed in the US with charges of approximately $36.1 billion.

The number of total knee replacements are expected to increase due to the aging population.

Costs about $15,000 per procedure, about $9 billion per year.

90% of implants last more than 10 years.

Other causes of cartilage destruction include rheumatoid arthritis, hemophilia, seronegative arthritides, crystal deposition diseases, pigmented villonodular synovitis, idiopathic or steroid-induced avascular necrosis, and rare bone dysplasias.

Siblings of individuals undergoing joint replacement are 3-5 times more likely to require similar surgery than age-matched controls, suggesting genes contribute around 30% of the overall risk for severe osteoarthritis.

Chromosome 2 related to severe osteoarthritis of the knee.

Loss of joint space, cysts, subchondral sclerosis, and osteophytes confirm the diagnosis of osteoarthritis.

The overall mortality rate is less than 1%.

Risk of acute myocardial infarction following total hip or knee replacement was elevated during the first two weeks after the procedure (Lalmohamed A et al).

In the above study thee absolute six-week risk of acute myocardial infarction was 0.51% for hip replacement, and 0.21% for knee replacement.

The best predictor of range of motion following total knee replacement is the preoperative range of motion.

The primary indication is to relieve pain caused by severe arthritis.

Patients without significant loss of joint space tend to be less satisfied with their clinical result after the procedure.

Readmissions occur more frequently in older individuals, black patients, and in patients with more comorbidities processes.

High volume centers have improved outcomes, lower readmission rates, and decreased complication rates.

The Journal of Bone and Joint Surgery article examined the long term survival of total knee replacements in young, active patients 55 years old and younger to examine long-term outcomes (Long J et al): Of the 114 total knee replacements performed in 88 patients, the average age was 51 years old and patients were followed-up with after 30 years.

In the above study there was a 70 percent survivorship without revision surgery for any reason 30 years after the initial procedure.

In the above study the total knee replacement survivorship with failure defined as aseptic revision of the tibial or femoral component was 82.5 percent.

The average knee motion in the above studywas 110 degrees.

In a randomized trial treatment of knee osteoarthritis with total knee replacement compared to nonsurgical treatment, the former was associated with a higher number of serious adverse events but a greater number of patients had pain relief and functional improvement after 12 months (Skou ST et al).

Most patients in the above study who received nonsurgical treatment did not undergo total knee replacement before the 12 month follow-up.

Following total knee replacement poor outcome at three months to five years is reported to be 10 to 34% of patients.

Patients undergoing total knee arthroplasty or in high risk for postoperative Venus thromboembolism.

Substantial evidence is present that many commonly used treatments, including supplements (glucosamine) , acetaminophen, opioids, acupuncture, and arthroscopy have no clinical meaning for benefit over placebo in knee pain.

Enoxaparin, an inhibitor factor Xa and thrombin is often administered postoperative to reduce risk.
The surgical site is considered to be the main reason for postoperative venous thromboembolism through the extrinsic pathway of coagulation.
Targeting factor XI a key component of the intrinsic pathway attenuates thrombosis with little disruption of hemostasis.

Abelacimab an inhibitor of Factor XI given as a single intravenous dose after a total knee arthroplasty is affective for the prevention of venous thromboembolism and is associated with a low risk of bleeding.

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