Purpose: The purpose of this study was to perform a cost-effectiveness analysis of outpatient versus inpatient total hip arthroplasty (THA) in the USA, considering complication probability and the potential cost of such complications. Methods: A cost-effectiveness analysis was conducted from the societal perspective to evaluate the incremental cost and effectiveness of inpatient THA compared to outpatient THA over a lifetime horizon. Effectiveness was expressed in quality-adjusted life years (QALYs). Costs, expressed in 2019 US dollars, transition probabilities, and health utilities were derived from the literature. The primary outcome was the incremental cost-effectiveness ratio (ICER), with a willingness to pay (WTP) threshold set at $50,000/QALY. 1-way and probabilistic sensitivity analyses was performed to evaluate the effect of the various variables on the model. Results: In the base case, inpatient THA was more effective in terms of total utility (10.36 vs. 10.30 QALY), but also more costly ($48,155 ± 1673 vs. $43,288 ± 1, 606 for Medicare) than outpatient THA. Even with a lifetime horizon, the ICER was $81,116 per QALY and $140,917 per QALY for Medicare and private payer insurance, respectively, which is higher than the willingness to pay threshold. 1-way sensitivity analyses indicated that the variables having the most influence on the model were the utility of inpatient and outpatient THA and cost of inpatient and outpatient THA. Conclusions: This model determined that for a WTP threshold set at $50,000/QALY, outpatient THA is more cost-effective than inpatient THA from a societal perspective. Despite this, surgeons must weigh clinical factors first and foremost in determining if an individual patient can be safely operated on in the outpatient setting.
A New Method to Determine the Optimal Willingness to Pay in Cost-Effectiveness Analysis