Determining Cost-Effectiveness of Total Hip and Knee Arthroplasty Using the Short Form-6D Utility Measure

With the implementation of the Patient Protection and Affordable Care Act, cost-effectiveness analyses are becoming increasingly important for resource allocation, and particularly for the justification of costly procedures, such as total knee and total hip arthroplasties (TKAs and THAs). Therefore, using the Short Form-6D (SF-6D) utility values, the purpose of this study was to determine (1) the quality-adjusted life years (QALYs) gained and (2) and the cost-effectiveness of undergoing THA and TKA.

A total of 844 patients (357 men, 487 women) who had a mean age of 65 years (range, 39 to 80 years) underwent primary TKA, and 224 patients who had a mean age of 69 years (range, 44 to 88 years) underwent primary THAs at 7 institutions. The SF-6D values were derived for each patient preoperatively and at 1-year follow-up. QALYs were estimated at 1 year, and lifetime QALYs gained were determined using predicted life-expectancy values, at a discounted rate of 3% per year of life expectancy, to reflect a diminishing gain with time. National-level costs were determined using the 2011 Nationwide Inpatient Sample, and incremental cost-effectiveness ratios (ICER) were deduced for both groups.

The preoperative SF-6D values for the THA and TKA cohorts were 0.614 (range, 0.37 to 1) and 0.62 (range, 0.3 to 0.93). Postoperatively, SF-6D values improved significantly at 1 year in both groups. One-year QALYs for TKA and THA were 0.768 and 0.799. Lifetime QALYs gained for the groups were 2.07 and 1.85 (1.39 and 1.34 if discounted at a rate of 3% per year). The estimated ICER for TKA vs baseline presurgery was $43,107 per QALY, and $39,453 per QALY for THA vs baseline presurgery.

The ICER showed that THA and TKA are cost-effective, compared to the $50,000 USD/QALY threshold for cost-effectiveness, and justify resources allocated to these surgeries. The SF-6D can utilize existing functional outcome data, which makes these cost calculations considerably easier and more feasible for practicing orthopedists.