• Total Knee Arthroplasty


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    • Abstract: Total Knee ArthroplastyDisclaimer: This background information is not intended to be a comprehensivescientific discussion of the topic, but rather an attempt to provide a baseline levelof information for anyone unfamiliar with the subject matter.

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Total Knee Arthroplasty
Disclaimer: This background information is not intended to be a comprehensive
scientific discussion of the topic, but rather an attempt to provide a baseline level
of information for anyone unfamiliar with the subject matter.
Background:
Total Knee Arthroplasty
Knee replacement, or knee arthroplasty, is a common surgical procedure most often
performed to relieve the pain and disability from degenerative arthritis, most commonly
osteoarthritis, but other arthritides as well. Major causes of debilitating pain include
meniscus tears, osteoarthritis, cartilage defects, and ligament tears.
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.
Technique
The surgery involves exposure of the front of the knee, with detachment of part of the
quadriceps muscle from the patella. The patella is displaced to one side of the joint
allowing exposure of the distal end of the femur and the proximal end of the tibia. The
ends of these bones are then accurately cut to shape using cutting guides oriented to the
long axis of the bones. The cartilages and the anterior cruciate ligament are removed; the
posterior cruciate ligament may also be removed but the collateral ligaments are
preserved. Metal components are then impacted onto the bone or fixed using
polymethylmethacrylate (PMMA) cement. A round-ended implant is used for the femur,
mimicking the natural shape of the bone. On the tibia the component is flat, although it
often has a stem which goes down inside the bone for further stability. A flattened or
slightly dished high-density polyethylene surface is then inserted onto the tibial
component so that the weight is transferred metal to plastic not metal to metal. During the
operation any deformities must be corrected, and the ligaments balanced so that the knee
has a good range of movement and is stable. In some cases the articular surface of the
patella is also removed and replaced by a polyethylene button cemented to the posterior
surface of the patella. In other cases, the patella is replaced unaltered.
Variations
There are many different implant manufacturers and all require slightly different
instrumentation and technique. No consensus has emerged over which design of knee
replacement is the best. Clinical studies are very difficult to perform requiring large
numbers of cases followed over many years. The most significant variations are between
cemented and uncemented components, between operations which spare or sacrifice the
posterior cruciate ligament and between resurfacing the patella or not. Some also study
patient satisfaction data associated with pain.
Minimally invasive procedures have been developed that do not require dramatic cuts to
and through the quadriceps femoris muscle, reducing post-operative pain and disability.
This type of less invasive procedure is done by using gender-specific or patient-specific
knee implants that fit the knee better and more precisely, and have better long-term
affects on the patient.
Partial knee replacement
Unicompartmental arthroplasty (UKA), also called partial knee replacement, is an option
for some patients. The knee is generally divided into three "compartments": medial (the
inside part of the knee), lateral (the outside), and patellofemoral (the joint between the
kneecap and the thighbone). Most patients with arthritis severe enough to consider knee
replacement have significant wear in two or more of the above compartments and are best
treated with total knee replacement. Some patients have wear confined primarily to one
compartment, usually the medial, and may be candidates for unicompartmental knee
replacement. Advantages of UKA compared to total knee replacement (TKA) include
smaller incision, easier post -op rehabilitation, shorter hospital stay, less blood loss, lower
risk of infection, stiffness, and blood clots, and easier revision if necessary.
Pre-operative preparation
Before the surgery is performed, pre-operative tests are done: usually a complete blood
count, electrolytes, APTT and PT to measure blood clotting, chest X-rays, ECG, and
blood cross-matching for possible transfusion. Accurate X-rays of the affected knee are
needed to measure the size of components which will be needed. Medications such as
warfarin and aspirin will be stopped some days before surgery to reduce the amount of
bleeding. Patients may be admitted on the day of surgery if the pre-op work-up is
completed in advance.
Post-operative rehabilitation
Protected weight bearing on crutches or a walker is required until the quadriceps muscle
has healed and recovered its strength. Continuous Passive Motion is commonly used
postoperatively. Hospitalization varies depending on the health status of the patient and
the amount of support available outside the hospital setting. Usually full range of motion
is recovered over the first two weeks. At approximately six weeks patients have usually
progressed to full weight bearing with a cane. Complete recovery from the operation
involving return to full normal function may take three months and some patients notice a
gradual improvement lasting many months longer than that.
Risks and complications
According to the American Academy of Orthopedic Surgeons, blood clots in the leg
veins are the most common complication of knee replacement surgery. A prevention
program is usually implemented, which may include periodic elevation of legs, lower leg
exercises to increase circulation, support stockings and medication to thin the blood.
Periprosthetic fractures can occur with the aging patient population either intraoperatively
or postoperatively.
The knee at times may not recover its normal range of motion (0 - 135 degrees usually)
after total knee replacement. Much of this is dependent on pre-operative function. Most
patients can achieve 0 - 110 degrees, but stiffness of the joint can occur. In some
situations, manipulation of the knee under anesthetic is used to improve postoperative
stiffness.
In some patients, the kneecap is unstable post-surgery and dislocates to the outer side of
the knee. This is painful and usually needs to be treated by surgery to realign the
kneecap; however, this is quite rare.
In the past, there was a considerable risk of the implant components loosening over time
as a result of wear. As medical technology has improved however, this risk has fallen
considerably. Knee replacement implants can last up to 20 years in many patients;
whether or not they actually last that long depends largely in part upon how active the
patient is after surgery.
Infection
While it is relatively rare, periprosthetic infection remains one of the most challenging
complications of joint arthroplasty.
Supporting Evidence:
A. Institute for Clinical Systems Improvement Guideline: Preoperative
Evaluation, 2008. An evidence based guideline, which describes appropriate
evaluation for elective, low-risk operative procedures for adult and pediatric
patients.
B. Institute for Clinical Systems Improvement Health Care Order Set:
Preoperative Total Hip and Total Knee Arthroplasty, 2006. An evidence based
order set, which covers the preoperative care of adults for elective total hip and
total knee arthroplasty beginning at hospital admission prior to surgery and does
not include preoperative and screening orders from the physician office.
C. Institute for Clinical Systems Improvement Health Care Order Set:
Postoperative Total Hip and Total Knee Arthroplasty, 2006. An evidence
based order set, which covers the postoperative care of adults for total hip and total
knee arthroplasty and does not include discharge orders.
D. Institute for Clinical Systems Improvement Protocol: Perioperative
Protocol, 2009. An evidence based protocol, which describes the steps performed
throughout the perioperative period that are necessary to prevent wrong site, wrong
patient, or wrong procedure as well as to prevent surgical site infection and prevent
the unintentional retention of a foreign object.
E. Institute for Clinical Systems Improvement Protocol: Venous
Thromboembolism Prophylaxis. An evidence based guideline, which addresses
risk assessment for venous thromboembolism, risk assessment for bleeding, and
mechanical and pharmacologic therapies to reduce the occurrence of venous
thromboembolism in adult hospitalized patients.
F. Total knee replacement. National Institutes of Health (NIH) Consensus
Development Panel on Total Knee Replacement - Independent Expert Panel. 2004
Feb 17. 18 pages. NGC:003622. Guideline for use with knee joint failure caused by
osteoarthritis (OA); rheumatoid arthritis (RA), juvenile rheumatoid arthritis,
osteonecrosis, and other types of inflammatory arthritis
G. AAOS clinical guideline on osteoarthritis of the knee (phase II). American
Academy of Orthopaedic Surgeons - Medical Specialty Society. 2003. 15 pages.
NGC:003374. Guideline to guide qualified physicians through a series of diagnostic and
treatment decisions in an effort to improve the quality and efficiency of care in patients
with osteoarthritis of the knee.
H. Steps to reduce surgical risk. In: I guidelines for perioperative evaluation.
Brazilian Society of Cardiology. 2007. 7 pages. NGC:006322. Guideline with
objectives 1) To refine and unify the terminology used by the entire multidisciplinary
team, including the patients and their family and 2) To establish new routines, change
indication for surgery according to the information obtained during the perioperative
evaluation.
I. American Academy of Orthopaedic Surgeons clinical guideline on prevention of
symptomatic pulmonary embolism in patients undergoing total hip or knee
arthroplasty. American Academy of Orthopaedic Surgeons - Medical Specialty
Society. 2007 May 19. 63 pages. NGC:005665. A guideline to improve patient care by
outlining the appropriate information gathering and decision making processes involved
in managing the prevention of symptomatic pulmonary embolism in patients undergoing
total hip or knee arthroplasty.
J. AAOS clinical guideline on osteoarthritis of the knee. American Academy of
Orthopaedic Surgeons - Medical Specialty Society
American Association of Neurological Surgeons - Medical Specialty Society
American College of Physical Medicine and Rehabilitation - Professional
Association American College of Rheumatology - Medical Specialty Society. 1996
(revised 2003). 17 pages. NGC:003069. A guideline to guide qualified physicians
through a series of diagnostic and treatment decisions in an effort to improve the quality
and efficiency of care in patients with osteoarthritis of the knee.
Areas of Current Clinical Review and Discussion:
• Anticoagulation management postoperatively
• Surgical technique selection
• Prosthesis selection
Basket of Care Scope samples:
• Adults with first-time elective unilateral total knee arthroplasty
including preoperative screening, hospital care, and postoperative
rehabilitation.
• Adults, without other co-morbid conditions, with first-time unilateral
elective total knee arthroplasty including preoperative screening,
hospital care and postoperative rehabilitation for 90 days.


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