Cost-effectiveness of total knee replacement: a prospective cohort study.

Objective: Total knee replacement (TKR) rates have significantly increased in the past decade. While the procedure itself might be costly, the cost-effectiveness and potential offset costs from patient and societal benefits have not been clearly established. The objective of this study was to perform an economic evaluation of TKR in patients with knee osteoarthritis (OA).

Methods: We conducted a 6-month prospective cohort study of 212 patients with knee OA who underwent TKR at a single hospital in Houston, Texas. We included patient-level data from hospital billing databases and the patients' self-reported direct and indirect costs. The clinical outcome measure was pain and function measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire; we used the minimum clinically important difference (MCID; ≥20-point change) and the WOMAC 20% (WOMAC20), 50% (WOMAC50), and 70% (WOMAC70) relative improvement criteria. Incremental cost-effectiveness ratios were estimated using direct and indirect costs and WOMAC improvement. A societal perspective was used and multiple sensitivity analyses were performed to assess the robustness of the principal analysis.

Results: The total incremental cost per TKR was $20,133. The incremental cost-effectiveness ratios (ICERs) for improvement at 6 months were $33,345, $25,255, $35,274, and $56,908 for the MCID, WOMAC20, WOMAC50, and WOMAC70, respectively. Best- and worst-case scenario sensitivity analyses did not have a significant impact on the ICERs. Patient time lost was the most influential variable in the multiway sensitivity analysis.

Conclusion: TKR is an effective intervention in reducing pain and improving functional status among patients with knee OA and is cost effective at both low and high levels of improvement.