An analysis of a theoretical cohort of patients using a mathematical model suggests that it is cost-effective for morbidly obese individuals to have bariatric surgery prior to total hip arthroplasty (THA), compared with having hip-replacement surgery alone.
Emily Dodwell, MD, assistant professor of orthopedic surgery, Weill Cornell Medical College, New York, and her colleagues presented the results at the American Academy of Orthopaedic Surgery’s 2015 annual meeting.
Previous studies showed that hip osteoarthritis is 2 to 4 times more common in people who are obese, and that hip-osteoarthritis patients who are obese are 3 times more likely to need THA, than those who are not obese. Based on this, Dodwell’s team created a “state-transition Markov model” using data from real patients. It simulated a theoretical flow of 100,000 morbidly obese patients either through primary THA with persisting obesity, or through bariatric surgery followed by THA after losing excess weight. The model also took into account the probabilities of needing repeat surgery and other patient parameters.
The assumptions in the model included that patients had a body mass index of at least 35 kg/m2 and had end-stage hip osteoarthritis and therefore were primary THA candidates.
The model yielded a cost of $55,795/patient for THA alone and $75,207/patient for bariatric surgery followed by THA. They also found there were 13.94 additional quality-adjusted life-years (QALYs) associated with THA alone and 15.11 QALYs associated with combining bariatric surgery and THA. By dividing the cost difference of $19,412 by the QALY difference of 1.17, the team arrived at an incremental cost-effectiveness ratio (ICER) of $16,591/QALY.
In addition, they performed a tornado analysis, which is a form of sensitivity analysis, and found this also favored combined surgery over THA alone.
“Performing bariatric surgery before THA appears to be cost-effective in the current state of what we believe in the US is the societal willingness to pay for QALYs,” Dodwell said.
Southren DL, McLawhorn AS, Figgie MP, et al. Cost-effectiveness of bariatric surgery prior to total hip arthroplasty in morbidly obese patients. Poster presented at: American Academy of Orthopaedic Surgery 2015 Annual Meeting; March 24-28, 2015; Las Vegas, NV. Abstract P078.