medwireNews: Patients with osteoarthritis who undergo unicompartmental knee replacement (UKR) are less likely to require postoperative opioid treatment than those undergoing total knee replacement (TKR), researchers report.
“This finding might indicate that UKR has a lower risk of postoperative persistent pain,” say Daniel Prieto-Alhambra (Botnar Research Centre, Oxford, UK) and colleagues, but they stress that the potential pain benefits may come at the cost of an increased risk for revision surgery among individuals undergoing UKR compared with TKR.
The study included 32,379 patients from one of five databases from the USA (n=4) or UK (n=1) who received UKR between 2005 and 2018 and were propensity score-matched to 250,377 patients who received TKR during the same period.
Prieto-Alhambra and team report in The Lancet Rheumatology that the unilateral procedure was “consistently associated” with a lower risk for opioid use in the 3–12 months after surgery relative to TKR, with an overall hazard ratio (HR) of 0.81 after calibration to account for observed differences in control outcomes. In the four US databases, the cumulative incidence of opioid use during this period ranged from 34.7% to 42.0% for UKR and was approximately 5 percentage points higher for TKR; the rates in the UK database were 20.6% for UKR versus 25.9% for TKR.
Patients undergoing UKR also had a significantly lower risk for venous thromboembolism than those undergoing TKR (calibrated HR=0.62).
However, UKR was associated with a significantly elevated risk for revision surgery in all databases studied, with a calibrated HR of 1.64. Rates of implant survival in the 5 years after surgery ranged from 94.7% to 97.6% for UKR and from 92.2% to 96.6% after TKR. There was no association between the type of surgical procedure and infection or readmission risk, and the evidence for mortality risk was inconclusive.
The investigators explain that the design of their population-based study aimed to mirror that of the TOPKAT trial, which demonstrated that patients receiving UKR and TKR had similar clinical outcomes, including pain, function, and revision rates.
Writing in an accompanying comment, Adrian Sayers and Michael Whitehouse, both from the University of Bristol in the UK, say that the discrepancy between the findings of the current study and those from TOPKAT “makes interpretation difficult.”
Asking “what does this all mean in the long term for patients?” they note that “reduced postoperative opioid use (pain) in the first year of a UKR compared with TKR” is a “promising” result, but “[b]alancing this finding against a more than 50% increase in the revision rate is difficult.”
The commentators emphasize that “[t]he assessment of pain and function over an extended duration is now essential.”
They add: “With a focus on quality adjusted life-years, should a patient be expected to trade lower pain and improved function in the short term for an increased risk of revision reflecting increased pain and poor function in the long term?
“This decision is undoubtedly difficult for a patient, and not a decision for which evidence is abundant.”
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Lancet Rheumatol 2019; doi:10.1016/S2665-9913(19)30075-X
Lancet Rheumatol 2019; doi: 10.1016/S2665-9913(19)30097-9