Total knee replacement (TKR) surgery is cost-effective in patients with severe obesity (BMI of 40Kg/m2 or greater) and end-stage osteoarthritis (OA). Typically, surgeons hesitate to perform TKR in these patients because they tend to have high rates of complications post-surgery. Findings, featured in the paper, ‘The Value of Total Knee Replacement in Patients With Knee Osteoarthritis and a Body Mass Index of 40 kg/m2 or Greater - A Cost-Effectiveness Analysis’, were published in Annals of Internal Medicine.
Obesity is a major risk factor for knee osteoarthritis, which affects more than 14 million adults in the US. As such, a growing proportion of patients receiving TKR have obesity (BMI of 30 kg/m2 or higher). In fact, 45.5% of TKR recipients in 2006 to 2010 had a BMI between 30 and less than 40 kg/m2, and 14.8% had a BMI of 40 kg/m2 or greater. While TKR has been shown to be very effective and cost-effective in non-obese patients with end-stage knee OA in the US, the question of whether or not TKR is cost-effective in this population has not been addressed.
Researchers from Brigham and Women's Hospital used the Osteoarthritis Policy (OAPoL) model to assess the value of TKR in recipients with extreme obesity across two age strata - younger or older than 65 as well as in the presence and absence of two major comorbidities - cardiovascular disease and diabetes, that has been shown to increase the risk of perioperative complications.
The researchers took into consideration higher rates of complications and pain reduction in patients with extreme obesity. They used TKR parameters from longitudinal studies and published literature, and costs from Medicare Physician Fee Schedules, the Healthcare Cost and Utilization Project, and published data. The findings examined cost, quality-adjusted life-years (QALYs) and incremental cost-effectiveness ratios (ICERs), discounted at 3% annually.
They found that TKR was a cost-effective strategy for patients aged 50 to 65 years with severe obesity and for patients older than 65 years. Similar findings were noted for TKR among patients with extreme obesity and end-stage knee osteoarthritis in the presence of cardiovascular disease and/or type 2 diabetes.
Total knee replacement increased QALYs by 0.71 year and lifetime medical costs by US$25,200 among patients aged 50 to 65 years with a BMI of 40 kg/m2 or greater, resulting in an ICER of US$35,200. Total knee replacement in patients older than 65 years with a BMI of 40 kg/m2 or greater increased QALYs by 0.39 year and costs by US $21,100 resulting in an ICER of US$54,100.
In TKR recipients with a BMI of 40 kg/m2 or greater and diabetes and cardiovascular disease, ICERs were below US$75,000 per QALY. Results were most sensitive to complication rates and preoperative pain levels. In the probabilistic sensitivity analysis, at a US$55,000-per-QALY willingness-to-pay threshold, TKR had a 100% and 90% likelihood of being a cost-effective strategy for patients aged 50 to 65 years and patients older than 65 years, respectively.
The researchers concluded that from a cost-effectiveness perspective, TKR leads to substantial improvements in quality-adjusted life expectancy and offers a good value in patients with extreme obesity and end-stage knee osteoarthritis, including those with multiple comorbidities.
The study was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health.