Based on existing research evidence, total knee replacement (TKR) is a safe
and cost-effective treatment for alleviating pain and restoring physical
function in patients who do not respond to nonsurgical therapies. There are
few contraindications to this surgery as it is currently used. Overall, TKR
has been shown to be a very successful, relatively low-risk therapy despite
variations in patient health status and characteristics, type of prosthesis
implanted, orthopaedic surgeons, and surgical facilities. Improvements can be
made in overall success of TKR by addressing each of these areas of variation
through further research. Each year, approximately 300,000 TKR surgeries are
performed in the United States for end-stage arthritis of the knee joint. As
the number of TKR surgeries performed each year increases and the indications
for TKR extend to younger as well as older patients, a review of available
scientific information is necessary to enhance clinical decision-making and
stimulate further research.
First used in the late 1950s, early TKR implants poorly mimicked the
natural motion of the knee and resulted in high failure and complication
rates. Advances in TKR technology in the past 10 years have enhanced the
design and fit of knee implants, resulting in improved short- and long-term
outcomes.
Despite the increased success of TKR, questions remain concerning which
materials and implant designs are most effective for specific patient
populations and which surgical approach is optimal for a successful outcome.
Physical, social, and psychological issues may influence the success of TKR,
and understanding patient differences could facilitate the decisionmaking
process before, during, and after surgery, thereby achieving the greatest
benefit from TKR. Particular attention also must be given to the treatment and
timing options related to the revision of failed TKR surgery.
To address these questions, the National Institute of Arthritis and
Musculoskeletal and Skin Diseases (NIAMS) and the National Institutes of
Health (NIH) Office of Medical Applications of Research (OMAR) convened a
consensus development conference to explore and assess the current scientific
knowledge regarding TKR. Specifically, the conference addressed the following
key questions:
What are the current indications and outcomes for primary TKR?How do specific characteristics of the patient, material and design of the
prosthesis, and surgical factors affect the short- and long-term outcomes of
primary TKR?Are there important perioperative interventions that influence
outcomes?What are the indications, approaches, and outcomes for revision TKR?What factors explain disparities in the utilization of TKR in different
populations?What are the directions for future research?
What are the current indications and outcomes for primary TKR?
How do specific characteristics of the patient, material and design of the
prosthesis, and surgical factors affect the short- and long-term outcomes of
primary TKR?
Are there important perioperative interventions that influence
outcomes?
What are the indications, approaches, and outcomes for revision TKR?
What factors explain disparities in the utilization of TKR in different
populations?
What are the directions for future research?
During the first 1½ days of the conference, experts presented the
latest TKR research findings to an independent panel. Included among the
experts presenting data were the principal investigators of a systematic
literature review prepared by the Minnesota Evidence-based Practice Center
under contract with the Agency for Healthcare Research and Quality (AHRQ).
After each set of presentations, a discussion period was held to allow
conference attendees to ask questions of the speakers and make comments. The
panel then met in executive session to weigh all of the scientific evidence
and prepare its consensus statement answering the above questions. On the
final day of the conference, the panel chairperson read the draft statement to
the conference audience and invited comments and questions. That afternoon, a
press conference was held to allow the panel to respond to questions from the
media.
In addition to its primary sponsors, the conference was cosponsored by the
following: the National Institute of Child Health and Human Development
(NICHD), the U.S. Food and Drug Administration (FDA), the National Institute
of Standards and Technology (NIST), and the Office of Research on Women's
Health (ORWH), NIH.
Primary TKR is most commonly performed for knee joint failure caused by
osteoarthritis (OA); other indications include rheumatoid arthritis (RA),
juvenile RA, osteonecrosis, and other types of inflammatory arthritis. The
aims of TKR are relief of pain and improvement in function. Candidates for
elective TKR should have radiographic evidence of joint damage,
moderate-to-severe persistent pain that is not adequately relieved by an
extended course of nonsurgical management, and clinically significant
functional limitation resulting in diminished quality of life. In patients
with RA and other inflammatory arthropathies, additional disease-specific
therapies may be needed to achieve control of disease activity before
proceeding with the surgical procedure.
TKR is an elective procedure, and the risks and outcomes vary. Therefore,
it is essential that patients be informed of the likely consequences of the
surgery in terms that are specific to them. Every patient's goals and
expectations (i.e., hopes and fears) should be ascertained before TKR to
determine whether their goals are attainable and their expectations are
realistic. Any discrepancies between the patient's expectations and the likely
surgical outcome should be discussed in detail before surgery.
In the past, patients between 60 and 75 years of age were considered to be
the best candidates for TKR. Over the past two decades, however, the age range
has been broadened to include, on the one hand, more elderly patients (e.g.,
octogenarians and beyond), many of whom have a higher number of comorbid
conditions, and, on the other hand, younger patients, whose implants may be
exposed to greater mechanical stresses (because of higher levels of physical
activity) over an extended time period. In patients younger than age 55,
alternative surgical procedures, such as osteotomy and unicompartmental knee
replacement, deserve consideration. Advanced age alone is not a
contraindication for TKR; however, perioperative complications are higher in
patients who are older at surgery as well as in those with more comorbid
conditions.
There are few absolute contraindications for TKR other than active local or
systemic infection and other medical conditions that substantially increase
the risk of serious perioperative complications or death. Obesity is not a
contraindication to TKR; however, there may be an increased risk of delayed
wound healing and perioperative infection in obese patients. Severe peripheral
vascular disease and some neurologic impairments are both relative
contraindications to TKR.
The success of primary TKR in most patients is strongly supported by more
than 20 years of followup data. Perioperative mortality approximates 0.5
percent. There appears to be rapid and substantial improvement in the
patient's pain, functional status, and overall health-related quality of life
in about 90 percent of patients, and 85 percent of patients are satisfied with
the results of surgery. Data suggest that these improvements in
patient-reported outcomes persist in both the short- and long-term studies.
Factors associated with the lack of improvement following surgery in the
remaining patients are not well known.
Complications following TKR include wound-healing problems; wound and
deep-tissue infection; deep-vein thrombosis and pulmonary embolism; pneumonia;
myocardial infarction; patellar fracture and/or extensor mechanism disruption;
joint instability, stiffness, and/or malalignment; and nerve and vascular
injuries. Factors associated with wound and deep-tissue infection include a
diagnosis of RA, diabetes mellitus, obesity, and use of glucocorticoids. One
of the most important factors leading to successful TKR is proper surgical
technique; the rate of complications in some studies that utilized national
administrative databases was inversely related to both surgeons' and
hospitals' volume of operations per year.
Rates of prosthesis failure requiring revision increase with duration of
followup after surgery from about 10 percent at 10 years to about 20 percent
at 20 years (~1 percent per year). Prosthesis failure rates vary
substantially across studies; factors associated with shortened time to
prosthesis failure include age younger than 55 years, male gender, diagnosis
of OA, obesity, and presence of comorbid conditions. It is hypothesized that
the higher rate of prosthesis failure observed in young obese men with OA is
related to higher levels of physical activity after TKR in this
population.
Thus, although the clinical conditions and circumstances leading to TKR are
broadly defined, several issues regarding indications remain unresolved.
Evidence-based indications from results obtained with standardized instruments
that measure pain, physical function, and quality of life as perceived by the
patient must be used to guide clinical decisionmaking and choice of surgery.
Instruments such as the Western Ontario and McMaster Universities
Osteoarthritis Index (WOMAC), the New Zealand Priority Criteria for Major
Joint Replacement, the Knee Society Score (KSS), or the Hospital for Special
Surgery (HSS) scale should be examined in this regard.
In short- (1-5 years) and long-term (5-10 years or longer) outcome studies,
outcomes typically include either self-reported measures of pain, function
(Short-Form 36 [SF-36] or WOMAC), or physician-reported measures (KSS, HSS
scales). Failure of the prosthesis is included in more long-term studies.
Short-term outcomes, as documented by functional outcome scales, are
generally substantially improved after TKR. Age, gender, and obesity do not
appear to be strongly associated with outcome, though lower body mass index
was associated with greater satisfaction and better functional outcome in a
large study of Canadian women. People with RA appear to have greater
improvements from baseline compared with people with OA, but this may reflect
the generally worse preoperative scores in those with RA. Functional outcome
is improved after TKR for people across the spectrum of disability status.
However, relatively lower functioning people, as measured by preoperative
WOMAC scores, improve by a greater percentage than those who are higher
functioning. Nonetheless, those with low baseline function do not achieve as
high an absolute level of function as those with better baseline status.
In general, prostheses are durable, but failure does occur. Because the
most common treatment for prosthesis failure is revision of the TKR, the
incidence of revision is commonly used as a measure of prosthesis failure.
The role of gender on failure rate is variable depending on the study. Data
based on two large studies (Sweden and Canada) demonstrate that gender has no
influence on revision rates among patients with OA. However, an American study
demonstrated that men had an overall greater risk of failure than women. Among
patients with RA, the risk of failure was greater in men than in women. In
addition, younger men who are obese appear to be at substantially higher risk
of revision than other patients, especially compared with older, nonobese
women.
Factors related to a surgeon's experience, technique, and choice of
prosthesis may have important influences on surgical outcomes. One of the
clearest associations with better outcomes appears to be the procedure volume
of the individual surgeon and the procedure volume of the hospital. Medicare
data indicate that the highest complication rate is observed among surgeons
who perform 12 or fewer operations per year, and complication rates decrease
as the number of operations performed each year increases. Similarly,
complication rates are highest in hospitals that perform less than 25
operations per year, and rates fall with increases in numbers of operations
performed.
Technical factors in performing surgery may influence both short- and
long-term success rates. Proper alignment of the prosthesis appears to be
critical in minimizing long-term wear, risk of osteolysis, and loosening of
the prosthesis. Computer navigation may eventually reduce the risk of
substantial malalignment and improve soft tissue balance and patellar
tracking. However, the technology is expensive and may increase operating room
time, and the benefits remain unclear.
Prosthesis design has evolved over time, with improvement in success rates.
A number of knee prosthesis designs are on the market today, however, and
their relative merits are generally unclear. Many design features, such as use
of mobile bearings or designs that spare cruciate ligaments, have theoretical
advantages, but durability and success rates appear roughly similar with most
commonly used designs.
The polyethylene components of modern prosthetic designs appear to be quite
durable. In the past, certain sterilization techniques—especially gamma
irradiation in air—appear to have had adverse effects on polyethylene
structure and durability. Storage in air with oxygen exposure, therefore, may
have had similar adverse effects. Modern sterilization and storage techniques
may largely solve this problem, but surgeons may need to be cautious with
polyethylene components that have been stored for several years.
Patients would benefit from being provided with an information card about
prosthesis design and date of manufacture. External labeling on prosthesis
packaging, including date of manufacture and sterilization, would be useful to
surgeons.
Several medical and rehabilitative strategies for TKR patients are used to
optimize surgical outcomes of reduced pain and improved function, and to
minimize complications such as deep-wound infections, thromboembolic disease,
postoperative anemia, and pulmonary infections. Despite the widespread use of
TKR, there is a notable lack of consensus regarding which medical and
rehabilitative perioperative practices should be employed, mostly because of
the lack of well-designed studies testing the efficacy and effectiveness of
such practices.
The use of perioperative antibiotics and other operating room procedures
reduces deep wound infections after knee surgery to less than 1 percent.
Although data also support the use of antibiotic impregnated bone cement as an
additional means of reducing the deep-wound infection rate, concern regarding
the availability, cost, and genesis of antibiotic resistant strains of
bacteria has tempered the enthusiasm for this strategy. Some data also support
the use of ultraclean-air operating rooms and whole-body exhaust-ventilated
suits worn by the operating room team to reduce infection rates. However,
these operating room procedures have not been universally adopted primarily
because of the uncertainty of their impact.
The American College of Chest Physicians (ACCP) Consensus Conference on
Antithrombotic Therapy classifies TKR as a high-risk procedure for venous
thromboembolism and recommends prophylaxis with (1) low-molecular-weight
heparin, (2) oral anticoagulants, (3) adjusted-dose heparin, or (4)
intermittent pneumatic compression/elastic stockings plus low-dose
unfractionated heparin or low-molecular-weight heparin. This recommendation is
based primarily on the reduction of the occurrence of deep venous thrombosis
(DVT) detected by venography following TKR. However, the vast majority of DVTs
following TKR are asymptomatic, and the available data indicate that DVT
prophylaxis does not alter the occurrence of symptomatic DVTs or pulmonary
embolism (PE), although no individual study was large enough to statistically
assess effects on the occurrence of PE. In addition, changes in postoperative
management that would be expected to reduce the incidence of DVT and PE,
including early mobilization, have occurred since these studies were
performed. Recent data demonstrate that detection and treatment of
asymptomatic DVTs do not alter the occurrence of symptomatic DVTs or pulmonary
embolism after TKR. Data from a large observational study of TKR published
after the most recent ACCP consensus conference show that use of warfarin does
not protect against pulmonary embolism or symptomatic DVTs compared with no
anticoagulation. Furthermore, bleeding complications, including catastrophic
gastrointestinal and wound hematoma, which could necessitate return to the
operating room, are risks of anticoagulation that must be considered.
The use of rehabilitation services is perhaps the most understudied aspect
of the perioperative management of TKR patients. Although there are several
theoretical reasons why the treatment of preoperative and postoperative
physical impairments such as muscle weakness and atrophy, joint contractures,
abnormal joint mechanics, and gait patterns should lead to improved short- and
long-term outcomes of surgery, there is no evidence supporting the generalized
use of any specific preoperative or postoperative rehabilitation intervention.
Similarly, the site of postacute care of TKR patients (home versus acute
rehabilitation unit versus skilled nursing facility) is currently determined
by local practice patterns and insurance reimbursement policies and not by
available data. Finally, no evidence-based guidelines exist for promoting or
limiting post-TKR physical activity.
Other practices for which there is no consensus either in the field or in
the literature include the prevention and/or treatment of postoperative anemia
(e.g., autologous blood transfusion, the use of erythropoetin, and various
intraoperative techniques) and the method of postoperative analgesia (epidural
analgesia versus intravenous narcotics, the use of cyclooxygenase-2 selective
inhibitors). There is consensus that pain should be managed aggressively.
There is general consensus that preoperative cardiac risk assessment should
be performed and cardiopulmonary function should be optimized before TKR.
Smoking cessation can reduce the risk of cardiac ischemia and postoperative
pneumonia and should be recommended for all smokers preoperatively although it
may need to be initiated at least 2 months before surgery for optimal effect.
Among patients older than age 70, preoperative assessment of mental status
with a standardized instrument such as the Mini Mental Status Exam (MMSE) can
help to identify patients at high risk for delirium. Postoperatively,
incentive spirometry should be used to reduce the incidence of pneumonia.
Preoperative patient education about what will happen during surgery and the
postoperative period has been shown to improve patient outcomes, including
reduced use of pain medications, reduced anxiety, and improved patient
satisfaction.
As the cumulative incidence of primary TKR increases, as indications extend
to older and younger individuals, and as the population ages, the absolute
number of revision knee replacements will increase even if the rate of
failures in primary procedures continues to decrease. Revision surgery is
complex and costly, requires technical expertise, and should be performed in
high-quality hospitals by skilled health care teams. Consequently, the
surgeon's experience, hospital characteristics, and related health care costs
with revision should be examined carefully.
As with primary TKR, revisions for failed TKR are done to alleviate pain
and improve function. The goals of TKR revision are restoration of mechanical
and rotational alignment, restoration of joint line and space, and achievement
of stable implant fixation.
It remains very important to refine the indications for revision and to do
so on the basis of the best available outcome data. The decision to revise, as
is true of decisions regarding primary procedures, must consider circumstances
such as the presence of disabling pain, stiffness, and functional limitation
unrelieved by appropriate nonsurgical management and lifestyle changes.
Evidence of progressive and substantial bone loss alone is sufficient reason
to consider revision in advance of catastrophic prosthesis failure. Fracture
or dislocation of the patella, instability of the components or aseptic
loosening, infection, and periprosthetic fractures are common reasons for
total knee revision.
The results of TKR revision are not as good as those of primary TKR, the
former being approximately 70 percent in the good-to-excellent range whereas
the latter is approximately 90 percent. Outcomes are better for patients who
undergo revision for aseptic loosening as opposed to infection. The proportion
of patients with good-to-excellent outcomes declines with each successive
revision.
It is critical to identify the cause of the original prosthesis failure to
improve the outcome following revision surgery. Early loosening may result
from poor surgical technique of the original TKR, infection, mechanical
overload, or osteolysis. Osteolysis appears to result from an inflammatory
reaction to particulate debris generated from the prosthesis. Efforts to
minimize osteolysis include a search for more durable and wear-resistant
materials. Research in management of osteolysis includes nonsurgical
treatment, such as use of bisphosphonates and cytokine inhibitors. Periodic
radiographic monitoring, as part of standard, long-term orthopaedic followup
care, may allow appropriate management before prosthesis failure.
A number of options must be considered in planning a revision operation.
Current revision implants have been available only for the past decade and
appear to improve results, although more long-term data are needed. Although
the literature on revision TKR is limited, outcomes of revision for failed
primary TKR show good results at 5 years, but long-term results are less
certain. Revision for infection is a challenging problem, with the most
successful functional results being obtained in a two-stage revision.
Salvage procedures for failed revision TKR include the following: (1)
resection arthroplasty (usually reserved for nonambulatory patients with
persistent infections), (2) arthrodesis, and (3) above-the-knee amputation. A
salvage procedure is eventually required in less than 10 percent of revised
TKRs. The primary indication for a salvage procedure is an infected revised
TKR. The limited data available indicate that pain relief and improved
function following any of these salvage procedures are limited and far
inferior to revision TKR.
There is clear evidence of racial/ethnic and gender disparities in the
provision of TKR in the United States. Although the absolute rates of TKR for
men and women are similar, they do not reflect the greater burden of arthritis
suffered by women. A Canadian study, after adjusting for age, self-reports of
arthritis, and willingness to accept surgery, found that women were
significantly less likely to undergo knee replacements. Furthermore, at the
time of surgery, women have worse pain and functional limitation than men.
A recent study of Medicare administrative data from 1998 through 2000
revealed annual procedure rates per 1,000 of 4.8 for white males, 3.5 for
Hispanic males, and 1.9 for African American males. The corresponding rates
were 5.9 for white women, 5.4 for Hispanic women, and 4.8 for African American
women. These disparities are not new—Medicare data from 1980 through
1988 demonstrated a range of white-to-African American ratio for TKR from 3.0
to 5.1 for men and a range of ratio from 1.5 to 2.0 for women.
Racial or ethnic differences in the provision of care are not limited to
joint replacements. Elderly whites are more likely than African Americans to
receive care from a physician. Medicare data from 1993 showed significant
racial or ethnic differences in the provision of angioplasties, coronary
artery bypass grafts, and screening mammography. Other studies have
demonstrated that African Americans are significantly less likely to undergo
carotid endarterectomies, lumbar disc procedures, repair of abdominal aortic
aneurysms, and kidney transplants.
Patients with Medigap insurance are more likely to have knee replacements
than those with Medicare alone. A Maryland study found that population rates
for discretionary orthopaedic, vascular, and laryngologic surgery increased
with community income levels.
A number of factors may be critical in explaining these disparities,
including issues related to equity and access, physician recommendations,
patient perceptions and preferences, and interactions between health care
providers and patients.
The limited role of economic and other access factors in these racial or
ethnic disparities can be demonstrated by persistence of significant
differences in the rate of procedures in the Veterans Administration (VA)
system, where cost and access are presumed equivalent across race or ethnic
groups. VA studies have found that white veterans are more likely than African
American veterans to undergo cardiac catherization, cardiac angioplasty, and
coronary artery bypass grafts. Furthermore, African American veterans were 1.5
times more likely than whites to undergo lower extremity amputation versus
lower extremity revascularization. Hispanic veterans were 1.4 times more
likely than whites to undergo amputation.
To receive a knee replacement, the patient must either first seek care from
a health care provider and be referred to an orthopaedic surgeon, or be
self-referred directly to an orthopaedic surgeon. The orthopaedic surgeon must
then offer TKR, and the patient must accept the recommendation of the surgeon.
Disparities can result from inequities at any of these steps.
Patients' acceptance of physician recommendations varies greatly. Among
persons with a potential need for TKR, only 12.7 percent of women and 8.8
percent of men were "definitely willing" to have the procedure. In
a Cleveland VA study, African American veterans were more likely to perceive
various traditional and complementary care modalities as efficacious and less
likely to perceive joint replacement surgery as efficacious. African American
patients in the same cohort were less likely than white patients to have had
family or friends who had joint replacement, or to report a good understanding
of joint replacement as a form of treatment.
The interaction between the patient and physician has a good deal to do
with final recommendations and the patient's acceptance of those
recommendations. There is support for the hypothesis that provider beliefs
about patients and provider behavior during encounters are independently
influenced by patient race or ethnicity. African American patients who visit
physicians of the same race or ethnicity rate their visits as more satisfying
and participatory than do patients who see physicians of other races or
ethnicities. This argues for encouraging minority students to enter medical
careers.
In summary, there are racial/ethnic and gender disparities in the provision
of TKR. These disparities are not different from disparities in a number of
other procedures. Physicians' beliefs about their patients, the limited
familiarity with these procedures in minority communities, patient mistrust of
the health care system, and personal beliefs about the most effective
treatment of joint problems may all play a role in racial or ethnic
disparities. In the final analysis, however, the full explanation for these
differences is not known.
The panel proposes a research agenda that reflects different perspectives
of knee-related disability and TKR surgery: (1) the societal perspective, (2)
the provider and health care system perspective, and (3) the individual
patient perspective. These perspectives are derived from a model of disease
and disability in Enabling America (Institute of Medicine, 1997), in
which disability (i.e., the alteration of the ability to perform expected
social roles) is the end result of a process that begins with pathology and
progresses to impairment and functional limitation. In the context of this
panel's deliberations, pathology of the knee results in pain and functional
limitation of the joint that is severe enough to affect the person's life. The
full spectrum of research and research methods, including basic, applied, and
clinical science and epidemiologic and health services research, should be
used to study all aspects of knee disability and therapies for it. Potentially
fruitful areas of basic and applied research include studies on the cellular
and molecular biology of aseptic loosening and osteolysis, the relationship of
knee kinematics to TKR function and durability, the relationship between the
properties of the knee component materials and wear, and the development of
surrogate markers for implant performance and survivorship.
Societal Need and Burden Perspective
Much of the research related to TKR has focused on factors that directly
affect outcomes of the surgical procedure rather than societal-level factors.
Relatively little population-based research exists on the prevalence of severe
pain and disability related to pathology of the knee. The burden on society of
this disability and the cost of its treatment have not been adequately
assessed. In addition, the cost-effectiveness of various prevention and
treatment modalities for the problem has not been well established.
Most of the existing research in this area has been limited to persons 65
years of age and older because the majority of the available data are derived
from the Medicare system. However, some people begin to experience severe pain
and disability in the knee in their 40s, and population data comparable to
Medicare data are not available for this younger age group. Of critical
importance to the consideration of knee-related disability and TKR surgery is
the determination of the potential need for this procedure in the total
population. To establish this need, research must systematically sample the
community at large to avoid the biases inherent in studying only those persons
with adequate access to the medical care system. The suggested design for this
study is a prospective, longitudinal, population-based cohort to delineate how
knee disability develops and how persons with this problem do or do not access
effective treatments, including but not limited to TKR surgery. The design of
such a cohort must ensure adequate representation of groups in the population
who are currently underserved; then it can be used to identify the extent of
disparities in the use of TKR surgery or other treatments for knee disability.
The variables to be measured in such a cohort study must be broad enough to
capture the disabling process. An additional goal of the cohort study would be
to compare outcomes of surgically and nonsurgically treated patients in order
to provide more accurate estimates of effect sizes for the studies of outcomes
outlined in the following section.
Provider and Health Care System Perspective
This realm of research concerns the surgeon, surgery/prosthesis,
perioperative care, and postoperative rehabilitation, and focuses on the
surgical outcomes of TKR. We recommend broadening the scope of this ongoing
research to include all variables related to the surgeon; surgical technique,
including type of prosthesis and implantation technique; selection and
perioperative care of patients; quality and characteristics of the
institution, such as infection control methods and surgical volume;
preoperative and postoperative interventions, including rehabilitation
therapy; and continuity of care, including the pre- and postoperative plan for
longer term followup and all types of physical activity. Outcomes should be
assessed in all patients who receive knee surgery, as opposed to a convenience
sample of those who return to the surgeon, with sufficient followup over the
life of the prosthesis. We suggest that a national, research-quality
multicenter registry be established to serve as a national resource of data
related to the short- and long-term sequelae of knee surgery, including
functional outcomes. The registry should be of sufficient size to permit
multivariable analyses of risk factors for poor outcomes, with aggressive
followup of all patients and their health outcomes.
In addition to the use of comprehensive research registries to observe
long-term outcomes, we advocate randomized controlled trials to evaluate
select aspects of the knee replacement surgery. For example, a randomized,
placebo-controlled trial of prophylactic anticoagulation that assesses the
outcomes of PE, bleeding, wound complications, and death seems warranted.
Given the lack of evidence about rehabilitative interventions and the
resources utilized by these interventions, we recommend that rehabilitation in
various sites be studied for its efficacy and effectiveness.
Individual Patient Perspective
This realm of research will evaluate the personal factors that affect the
decision to proceed to surgery as well as those factors that affect surgical
outcomes.
With respect to the decision to proceed to surgery, there is strong
evidence of disparities between genders and among racial or ethnic groups in
(1) knowledge of the surgery, given similar levels of medical need, (2)
willingness to have surgery, given the same level of knowledge, and (3) actual
surgical rates, taking need and willingness into account. We do not know the
extent to which these disparities are the result of subjective differences
across groups in perception of pain or disability and orientation to surgery
(e.g., risk aversion or cultural affinity with the health care providers who
might refer to surgery, or both), objective differences in access to care as a
result of the potential financial burden and extent and kind of health
insurance, or discrimination on the part of health care providers.
Once individuals have TKR, we know little about the patient-level factors
affecting outcomes, including medical and sociodemographic characteristics,
participation in rehabilitation services, the extent of social support, and
the level of patients' physical activity.
Patients may report outcomes more critically when asked explicitly in
qualitative studies compared with outcomes as expressed in standardized
quantitative measures, indicating that extant outcome measures may not capture
some of the difficulties patients experience after surgery.
Primary TKR is most commonly performed for knee joint failure caused by OA;
other indications include RA, juvenile RA, osteonecrosis, and other types of
inflammatory arthritis. The aims of TKR are relief of pain and improvement in
function. Candidates for elective TKR should have radiographic evidence of
joint damage, moderate-to-severe persistent pain not adequately relieved by an
extended course of nonsurgical management, and clinically significant
functional limitation resulting in diminished quality of life.
The success of primary TKR in most patients is strongly supported by more
than 20 years of followup data. There appears to be rapid and substantial
improvement in the patient's pain, functional status, and overall
health-related quality of life in about 90 percent of patients; about 85
percent of patients are satisfied with the results of surgery.
Short-term outcomes, as documented by functional outcome scales, are
generally substantially improved after TKR. Functional outcome is improved
after TKR for people across the spectrum of disability status. In general,
prostheses are durable, but failure does occur.
Age younger than 55 at the time of TKR, male gender, diagnosis of OA,
obesity, and presence of comorbid conditions are risk factors for
revision.
Factors related to a surgeon's case volume, technique, and choice of
prosthesis may have important influences on surgical outcomes. One of the
clearest associations with better outcomes appears to be the procedure volume
of the individual surgeon and the hospital.
Technical factors in performing surgery may influence both the short- and
long-term success rate. Proper alignment of the prosthesis appears to be
critical. Many design features, such as use of mobile bearings or designs
sparing cruciate ligaments, have theoretical advantages, but durability and
success rates appear roughly similar with most commonly used designs.
There is consensus regarding the following perioperative interventions that
improve TKR outcomes: systemic antibiotic prophylaxis, aggressive
postoperative pain management, perioperative risk assessment and management of
medical conditions, and preoperative education.
The effectiveness of anticoagulation for the prevention of pulmonary emboli
is unclear. There are insufficient data to support specific perioperative
rehabilitation strategies, methods to reduce postoperative anemia,
postoperative physical activity recommendations, and the site of postacute
care.
Revision TKR is done to alleviate pain and improve function. Fracture or
dislocation of the patella, instability of the components or aseptic
loosening, infection, and periprosthetic fractures are common reasons for
total knee revision. A painful knee without an identifiable cause is a
controversial indication. Contraindications for revision TKR include
persistent infection, poor bone quality, highly limited quadriceps or extensor
function, poor skin coverage, and poor vascular status. Results are not as
good as with primary TKR; outcomes are better for aseptic loosening than for
infections. When infection is involved, successful results occur with a
two-stage revision. Failed revisions require a salvage procedure (resection of
arthroplasty, arthrodesis, or amputation), with inferior results compared with
revision TKR.
There is clear evidence of racial/ethnic and gender disparities in the
provision of TKR in the United States. Racial or ethnic differences in the
provision of care are not limited to joint replacements. The limited role of
economic and other access factors in these racial or ethnic disparities can be
demonstrated by significant differences in the rate of procedures in the VA
system, where cost and access are assumed equivalent across race or ethnic
groups.
Patients' acceptance of physician recommendations varies greatly. Among
persons with a potential need for TKR, only 12.7 percent of women and 8.8
percent of men were "definitely willing" to have the procedure.
The interaction between the patient and physician affects the final
recommendations and the patient's acceptance of those recommendations.
Physicians' beliefs about their patients, the limited familiarity with these
procedures in minority communities, patients' mistrust of the health care
system, and personal beliefs about the most effective treatment of joint
problems may all have a role in these racial or ethnic disparities.
The goal of new population-based observational research is to discover the
need for services among persons with knee disability and the extent to which
this need is currently being met by resources available within the family and
in the community at large (including the health care system).
Research into the impact of providers and the health care system should be
broadened to include all TKR variables related to the surgeon, such as
training and experience; surgical technique, including type of prosthesis and
implantation technique; selection and perioperative care of patients; quality
and characteristics of the institution, such as infection control methods and
surgical volume; preoperative and postoperative modalities, including
rehabilitation therapy; and continuity of care, including the pre- and
postoperative plan for longer term followup and physical activity. In addition
to broadening the scope of variables studied, the outcomes assessment must
include all persons who receive knee surgery, as opposed to a convenience
sample of those who return to the surgeon, and the followup must be
sufficiently long to encompass the expected life of the prostheses.
Research should identify the extent to which disparities in the use of TKR
are the result of subjective differences across groups in perception of pain
or disability and orientation to surgery (risk aversion or cultural affinity
with the health care providers who might refer to surgery, or both); objective
differences in access to care as a result of the potential financial burden
and extent and kind of health insurance; or discrimination on the part of
health care providers. Research also should identify the patient-level factors
affecting outcomes after surgery, including medical and sociodemographic
characteristics, participation in rehabilitation services, the extent of
social support, and the level of a patient's physical activity after the
surgery.