Cost-Effectiveness of Surgical and Nonsurgical Treatments for Unicompartmental Knee Arthritis: A Markov Model

Abstract

Background: There has been increased utilization of surgical options for the treatment of end-stage unicompartmental arthritis in patients at both extremes of the age spectrum. The purpose of this study was to determine how these changing paradigms affected the lifetime cost-effectiveness of total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), and nonsurgical treatment (NST).

Methods: Using a Markov decision analytic model, we assessed how lifetime costs and quality-adjusted life years (QALYs) vary as a function of age at the time of initial treatment (ATIT) of patients with end-stage unicompartmental knee osteoarthritis undergoing TKA, UKA, and NST. Separate models were estimated for ATITs at 5-year intervals from 40 through 90 years. Direct medical costs, QALYs, and transition probabilities were determined from the published literature. Indirect costs (lost wages, Social Security disability collections, and value of missed workdays) were calculated. Cost-effectiveness and incremental cost-effectiveness ratios (ICERs) were calculated for each treatment at each ATIT. The model assumed no crossover from NST to UKA or TKA. ICERs were compared with a willingness-to-pay threshold of 50,000 U.S. dollars, and a 1-way sensitivity analysis was used to assess the robustness of ICER-based treatment decisions. Societal savings were estimated.

Results: In the base-case model, surgical treatments were less expensive and provided a greater number of QALYs than NST from 40 to 69 years of age. From 70 years of age and onward, surgical treatments remained cost-effective compared with NST, with ICERs remaining below the societal willingness-to-pay threshold. When surgical treatments were compared, UKA dominated TKA for all ATITs. The preferential use of UKA in all U.S. patients with unicompartmental osteoarthritis would result in an estimated lifetime societal savings of 987 million to 1.5 billion U.S. dollars per annual wave of patients undergoing treatment.

Conclusions: In this preliminary assessment, recent expansion of surgical treatments into younger and older age demographics appears to be cost-effective in the setting of unicompartmental knee osteoarthritis. Our findings suggest that NST should be used sparingly in patients below the age of 70 years and UKA should be chosen over TKA in order to maximize cost-effectiveness.

Level of evidence: Economic and decision analysis Level IV. See Instructions for Authors for a complete description of levels of evidence.