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Total Knee Replacement PORT publishes recent findings
The volume of total knee replacements (TKRs) performed in the
United States reached 150,000 in 1990, with expenditures of $3.5
billion. Hospital costs alone for knee implants are about $9,000
per procedure, exclusive of physician fees and rehabilitative
treatments. Patients with advanced joint destruction who undergo
TKR usually experience pain relief and increased joint mobility,
but long-term benefits are much less certain.
The Total Knee Replacement Patient Outcomes Research Team (PORT)
is supported by the Agency for Health Care Policy and Research
(HS06432) to assess and improve the outcomes of this procedure.
Led by Deborah A. Freund, Ph.D., of Indiana University, the PORT
investigators recently published three studies. They compare
rural with urban costs for TKRs, calculate the rates of tibial
osteotomies in Canada and the United States, and compare the
usefulness of general and specific measures to assess
health-related quality of life following TKR.
Culler, S.D., Holmes, Ann M., and Gutierrez, B. (1995).
hospital costs of knee replacement for rural residents by
location of service." Medical Care 33(12), pp.
Knee replacement surgery, which improves the functional mobility
of persons with severe arthritis, is rapidly diffusing into rural
hospitals. The predicted cost per TKR is lower in rural than
urban hospitals, especially in hospitals that do a large number
of TKRs, according to this study by TKR PORT researchers. They
analyzed 1985-1989 data from the Health Care Financing
Administration's Medicare Provider Analysis and Review and found
that cost savings ranged from $1,560 (for a Medicare patient
discharged home with average severity of illness) to $6,306 (for
hospitalization of a Medicare patient with multiple knee
replacements and high severity of illness).
The higher the hospital's TKR case volume, the greater the cost
savings. For example, the median volume of knee replacements for
rural hospitals was nine per year, with an average cost per
hospitalization of $8,690. By increasing the hospital's volume
even by one knee replacement per year, the predicted cost per
case fell $48. This incremental cost savings declined as volume
increased for both urban and rural hospitals, although the
incremental effects remained greater in rural hospitals. Also,
the significant cost savings that can be achieved by moving
patients from low- to high-volume hospitals in each setting
provides support for regionalization of TKR surgery. For
instance, more than $1,000 per hospitalization can be saved if a
rural patient has knee replacement surgery in a rural hospital
performing nine or more TKRs per year, compared with one in which
only a single surgery is performed each year.
Wright, J., Heck, D., Hawker, G., and others (1995, October).
"Rates of tibial osteotomies in Canada and the United States,"
Clinical Orthopaedics, pp. 266-275.
Tibial osteotomy, one surgical option for treating osteoarthritis
of the knee, has declined as TKR surgery has increased over the
past decade. Osteotomy shifts the axis of weightbearing onto a
more normal joint surface and lessens pain in about 80 percent of
patients. Disadvantages of this procedure include incomplete
relief of pain, and there is a 50 percent rate of pain recurrence
10 years after osteotomy. TKR, on the other hand, does not allow
patients to return to vigorous sports or heavy labor, and there
is a possibility of loosening the prosthesis. For these reasons,
tibial osteotomy still may be the most appropriate procedure for
younger, active patients with primarily unicompartmental
osteoarthritis who want to participate in vigorous physical
activity, according to TKR PORT researchers.
They calculated the rates of tibial osteotomies performed from
1985 to 1990 in Ontario, Canada, and the United States, using
data from the Health Care Financing Administration, Ontario
Health Insurance Plan, and National Hospital Discharge Survey
databases. They found that osteotomy rates decreased in both
countries by about 11 to 14 percent per year in patients 65 years
and older and by 3 to 4 percent per year in patients younger than
65 years. Men received twice as many osteotomies as women in both
countries. In the United States, the average rate of tibial
osteotomies was two to three times lower than in Ontario, most
likely due to different expectations and preferences of patients
and/or surgeons. A portion of the decline in osteotomy rates in
older patients may be a result of the increasing use of TKR and
growing confidence among surgeons in TKR outcomes. Also, the
longevity of the prosthesis is of less concern in older patients
than in younger patients.
Hawker, G., Melfi, C., Paul, J., and others (1995).
"Comparison of a generic (SF-36) and a disease specific (WOMAC)
instrument in the measure of outcomes after knee replacement
surgery." Journal of Rheumatology 22(6), pp.
Measuring the health status of individuals with a particular
medical condition is best achieved by using both specific health
status measures relevant to the particular condition and generic
measures of overall health status, particularly when assessing
the health status of elderly persons who typically have several
coexisting medical conditions. The Total Knee Replacement PORT
investigators compared the generic health-related quality of life
(HRQL) measure, the SF-36, with the disease-specific HRQL
measure, the Western Ontario and McMaster Universities
Osteoarthritis Index (WOMAC) in assessing the health status of
nearly 1,200 Medicare patients who had undergone knee replacement
surgery 2 to 7 years previously. The investigators accumulated
data through a mail survey of self-administered questionnaires to
three random samples of Medicare beneficiaries.
The SF-36 measured physical, role/emotional, and role/social
functioning; bodily pain; vitality; and general health
perceptions. The WOMAC, designed to assess hip or knee
osteoarthritis, assessed stiffness, pain, and physical
functioning. The SF-36 correlated better with patients'
coexisting conditions than the WOMAC on all dimensions of pain,
physical functioning, and overall scores. However, the WOMAC
overall scores correlated better than the SF-36 scores with the
current condition of the knee, rated from 1 or "much worse" to 5
or "much better." The researchers conclude that generic measures
are necessary to compare outcomes across different populations
and different diseases, whereas disease-specific measures assess
the specific disabilities of patients in defined diagnostic
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