Total knee replacement cost-effective for end-stage osteoarthritis even in severe obesity
A modeling study analyzed the long-term effects and costs of total knee replacement for patients who were ages 50 years or older and had end-stage knee osteoarthritis and a body mass index of 40 kg/m2 or greater.
Total knee replacement is an effective and cost-effective strategy for treating end-stage knee osteoarthritis in severely obese patients, a study found.
Researchers used the Osteoarthritis Policy Model to assess long-term clinical benefits, costs, and cost-effectiveness of total knee replacement in patients with a body mass index (BMI) of 40 kg/m2 or greater. Data were derived from longitudinal studies and published literature, and costs were assessed from Medicare Physician Fee Schedules and the Healthcare Cost and Utilization Project. Results of the study were published March 23 by Annals of Internal Medicine.
In patients who had a total knee replacement, a BMI of 40 kg/m2 or greater, and diabetes and cardiovascular disease, incremental cost-effectiveness ratios (ICERs) discounted at 3% annually were below $75,000 per quality-adjusted life-year (QALY). A probabilistic sensitivity analysis showed that, at a $55,000-per-QALY willingness-to-pay threshold, total knee replacement had a 100% likelihood of being a cost-effective strategy for patients ages 50 to 65 years and 90% likelihood for patients older than age 65 years.
Total knee replacement in patients ages 50 to 65 years with a BMI of 40 kg/m2 or greater resulted in an estimated discounted quality-adjusted life expectancy (QALE) of 10.1 years, compared with 9.3 years for patients without total knee replacement. Patients with knee replacements accrued an additional $25,200 in costs over age-matched patients who didn't get a knee replacement (ICER, $35,200 per QALY). Patients older than age 65 years with total knee replacement had a QALE of 6.7 years versus 6.3 years for age-matched patients without total knee replacement, which increased costs by $21,100, resulting in an ICER of $54,100 per QALY. Of this older cohort, 0.61% had a periprosthetic joint infection.
More than 50% of patients older than age 65 years with a BMI of 40 kg/m2 or greater had Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scores of 15 or below during the first five years after surgery, compared with fewer than 1% of patients who did not have total knee replacement. On average, patients' pain decreased 34.4 WOMAC points after replacement.
The study authors concluded that withholding total knee replacement from patients with a BMI of 40 kg/m2 or greater may not be justified from the standpoint of effectiveness or cost-effectiveness. “Even under unfavorable conditions (such as multiple comorbidities, [total knee replacement] efficacy decreased by 50%, or complication probabilities increased 7-fold), the procedure remained quality-adjusted life prolonging, on average, and had a cost-effectiveness ratio that never exceeded $148,000 per QALY,” they wrote. “Total knee replacement in patients with a BMI of 40 kg/m2 or greater seems to be a valuable treatment strategy.”