AHRQ report on total knee replacement - Clinical Briefs - Agency for Healthcare Research and Quality

Author: Carrie Morantz, Brian Torrey
Date: March 1, 2004

The Agency for Healthcare Research and Quality (AHRQ) has released a report on total knee replacement. "Evidence Report/Technology Assessment: No. 86, Total Knee Replacement" is available online at http:// www.ahrq.gov/clinic/epcsums/knee sum.htm.

Total knee arthroplasty is one of the most common orthopedic procedures performed; 171,335 primary knee replacements and 16,895 revisions occurred in 2001. Because these procedures are elective and expensive (Medicare paid approximately $3.2 billion in 2000 for hip and knee joint replacements) and because the prevalence of arthritis is expected to grow substantially as the population ages, these procedures are likely to come under increasing scrutiny.

Previous reports suggest that total knee arthroplasty improves functional status, relieves pain, and results in relatively low perioperative morbidity. However, based on conclusions from consensus panels or surveys of health care professionals, there is considerable disagreement about the indications for the procedure; that is, which patients are most likely to benefit from total knee arthroplasty and, conversely, in which patients is the procedure contraindicated or of low value.

Observations in the evidence report include the following:

* Total knee arthroplasty and total knee arthroplasty revisions are associated with improved function. The strongest evidence exists over a follow-up period of up to two years, but the studies that extend to five and even 10 years of follow-up show positive results as well.

* The average age of patients undergoing total knee arthroplasty was 70 years, with few over age 85. Two thirds were female, one third were considered obese, and nearly 90 percent had osteoarthritis. No studies provided data on racial/ethnic status.

* There is no evidence that age, gender, or obesity is a strong predictor of functional outcomes.

* Patients with rheumatoid arthritis show more improvement than those with osteoarthritis, but this difference may be related to their poorer functional scores at the time of treatment and thus their potential for more improvement.

* The revision rate through five or more years is 2.0 percent of knees and 2.1 percent of patients.

* Perioperative complications as defined by the investigator occurred in 5.4 percent of patients and 7.6 percent of knees. Most of these complications were "knee related" or deep venous thrombosis. There were only eight cardiovascular or pulmonary complications reported among nearly 6,000 patients, suggesting that these adverse effects were not fully addressed in the literature.

* There is reason to suspect selection effects in both the type of patients referred for total knee arthroplasty and the cases being reported in the literature, as well as the attrition on follow-up. Therefore, these findings must be interpreted with caution as the basis for clinical practice.

* Total knee arthroplasty revisions show a similarly positive functional effect (with the same design limitations).

These conclusions are tempered by the limitations of the designs of many studies included in the analysis. Although osteoarthritis does not seem to be a predictor of outcomes, the results seem to be somewhat better in patients who have rheumatoid arthritis, but few of these studies simultaneously controlled for other patient aspects.

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