Decreased opioid use, increased revision risk seen after unicompartmental vs total knee replacement
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Unicompartmental knee replacement compared with total knee replacement correlated with a decreased risk of postoperative opioid use and a lower risk of venous thromboembolism, according to study results. However, unicompartmental replacement had an increased risk of revision.
Using one U.S. and four U.K. databases, researchers identified patients who were at least 40 years old and had osteoarthritis. Of these patients, 33,867 underwent unicompartmental knee replacement (UKR) and 557,831 patients underwent total knee replacement (TKR). In all databases, opioid use between 91 and 365 days postoperatively was assessed for all patients. Investigators assessed postoperative complications at 60 days postoperatively and implant survival at 5 years. All databases evaluated outcomes apart from readmission, which was evaluated in three databases. Mortality was evaluated in two databases. Propensity score-matched Cox proportional hazards models were created for each outcome measure. To account for observed differences in control outcomes, investigators generated calibrated hazard ratios and then combined these with their meta-analysis. Overall, 32,379 patients who underwent UKR and 250,377 patients who underwent TKR were propensity score matched.
Results showed UKR correlated with a decreased risk of postoperative opioid use and decreased risk of venous thromboembolism. There was also a correlation between UKR and an increased risk of revision. However, no differences were seen between UKR and TKR for infection and readmission. Investigators noted there was not enough evidence to demonstrate whether the mortality risk decreased with the type of replacement. – by Monica Jaramillo
Disclosures: The researchers report no relevant financial disclosures.
Perspective
Back to TopDavid W. Murray, MD, FRCS
The excellent study of Burn and colleagues compared the outcome of matched unicompartmental (33,000) and total (250,000) knee replacements based on routinely collected data from four U.S. and one U.K. health care databases. Although the findings from each database were different, the conclusions from the meta-analysis of all five databases are what would be expected: Following UKR, there was evidence of better clinical outcomes with a 19% (CI 10% to 27%) decrease in use of opioids, which was a proxy for persistent pain, and a lower complication rate with a 38% (CI 5% to 64%) decrease in venous thromboembolism. However, the revision rate of UKR at 5 years was 64% (CI 40% to 94%) — higher than that of TKR.
The authors compared their results to the recently published randomized study (TOPKAT) comparing UKR and TKR, and found their results were broadly similar, except that in TOPKAT the revision rates of UKR and TKR were the same.
An important weakness of the health care database study and other similar studies, acknowledged in the paper, is that the precise indications for the procedure are not known, so these cannot be matched for and may have a profound influence on the outcome. For example, many surgeons tend to use UKR for patients with early arthritis, who they feel will not do well with TKR. These patients often do not do well following UKR and have a high revision rate. Had the study been able to compare UKR and TKR done for bone-on-bone medial compartment arthritis, the primary indication for UKR, which is satisfied in about half the cases having knee replacement, they might have found the revision rate of UKR and TKR were similar as in TOPKAT.
University of Oxford
Nuffield Orthopaedic Centre
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