Bariatric surgery before TKA may be cost-effective for morbidly obese patients with knee OA

Morbidly obese patients who undergo bariatric surgery 2 years prior to TKA experience greater quality of life compared with TKA alone.

Bariatric surgery prior to total knee arthroplasty in morbidly obese patients with end-stage knee osteoarthritis may be a cost-effective option for improving outcomes, according to results of a computer model-based evaluation.

“The idea was to explore whether or not performing an intervention before a total knee arthroplasty for morbid obesity might alter patient outcomes and be a cost-effective way of altering those outcomes,” Alexander S. McLawhorn, MD, MBA, clinical orthopedic surgery fellow at Hospital for Special Surgery, told Orthopedics Today. “Bariatric surgery 2 years prior to a total knee arthroplasty in morbidly obese patients may be a cost-effective treatment protocol from the societal and health payer perspectives.”

Cost-effectiveness

McLawhorn and his colleagues constructed a state-transition Markov model to compare cost-utility of immediate total knee arthroplasty (TKA) and bariatric surgery 2 years prior to TKA for patients with morbid obesity and end-stage knee osteoarthritis (OA). Costs, expressed in 2012 United States dollars, were estimated using administrative and claims data. Costs and utilities were discounted 3% annually.

Researchers determined effectiveness in quality-adjusted life-years. The main outcome measure was the incremental cost-effectiveness ratio.

Compared with morbidly obese patients who underwent bariatric surgery 2 years prior to TKA, results showed fewer quality-adjusted life-years gained among morbidly obese patients who underwent TKA alone. Researchers found an incremental cost-effectiveness ratio of approximately $13,910 per quality-adjusted life-year between the two procedures, a figure below the threshold willingness to pay of $100,000 per quality-adjusted life-year. Stable results were also found across broad value ranges for independent variables. The median incremental cost-effectiveness ratio was $14,023 per quality-adjusted life-year, according to probabilistic sensitivity analysis.

“In the model, you have patients who are morbidly obese living with end-stage osteoarthritis, and we keep them living in that poor health quality state for 2 years between the time they get bariatric surgery and the time they receive a total knee replacement,” McLawhorn said. “Despite living in that poor quality of life state for 2 additional years compared to patients who just go ahead and get a total knee replacement, they still end up accruing a greater quality of life at the end of the day than those morbidly obese patients who only have a total knee replacement.”

Limitations

According to McLawhorn, the most significant limitation of their study is computer models cannot simulate the real world perfectly. Thus, translating the model results to making care decisions for individual patients is not always possible or easy. In particular, individual patient preferences for treatment cannot be ignored. McLawhorn also noted several assumptions had to be applied to construct the model.

“We are now using large state-wide and national databases to more closely examine bariatric surgery, morbid obesity, and total joint replacement in a rigorous way to [better] characterize the associations between weight loss surgery prior to total joint replacement and patient outcomes after joint arthroplasty,” he said. “In particular, we are trying to determine if there is an optimal time interval between the two procedures and if there are specific bariatric procedures [that] are more beneficial than others in terms of reducing the risk of complications and improving patient outcomes after total joint replacement. Those associations are not well-defined and should be explored, first in retrospective style studies and eventually in a prospective way.” – by Casey Tingle

Disclosure: McLawhorn reports no relevant financial disclosures.

Bariatric surgery prior to total knee arthroplasty in morbidly obese patients with end-stage knee osteoarthritis may be a cost-effective option for improving outcomes, according to results of a computer model-based evaluation.

“The idea was to explore whether or not performing an intervention before a total knee arthroplasty for morbid obesity might alter patient outcomes and be a cost-effective way of altering those outcomes,” Alexander S. McLawhorn, MD, MBA, clinical orthopedic surgery fellow at Hospital for Special Surgery, told Orthopedics Today. “Bariatric surgery 2 years prior to a total knee arthroplasty in morbidly obese patients may be a cost-effective treatment protocol from the societal and health payer perspectives.”

Cost-effectiveness

McLawhorn and his colleagues constructed a state-transition Markov model to compare cost-utility of immediate total knee arthroplasty (TKA) and bariatric surgery 2 years prior to TKA for patients with morbid obesity and end-stage knee osteoarthritis (OA). Costs, expressed in 2012 United States dollars, were estimated using administrative and claims data. Costs and utilities were discounted 3% annually.

Researchers determined effectiveness in quality-adjusted life-years. The main outcome measure was the incremental cost-effectiveness ratio.

Compared with morbidly obese patients who underwent bariatric surgery 2 years prior to TKA, results showed fewer quality-adjusted life-years gained among morbidly obese patients who underwent TKA alone. Researchers found an incremental cost-effectiveness ratio of approximately $13,910 per quality-adjusted life-year between the two procedures, a figure below the threshold willingness to pay of $100,000 per quality-adjusted life-year. Stable results were also found across broad value ranges for independent variables. The median incremental cost-effectiveness ratio was $14,023 per quality-adjusted life-year, according to probabilistic sensitivity analysis.

“In the model, you have patients who are morbidly obese living with end-stage osteoarthritis, and we keep them living in that poor health quality state for 2 years between the time they get bariatric surgery and the time they receive a total knee replacement,” McLawhorn said. “Despite living in that poor quality of life state for 2 additional years compared to patients who just go ahead and get a total knee replacement, they still end up accruing a greater quality of life at the end of the day than those morbidly obese patients who only have a total knee replacement.”

Limitations

According to McLawhorn, the most significant limitation of their study is computer models cannot simulate the real world perfectly. Thus, translating the model results to making care decisions for individual patients is not always possible or easy. In particular, individual patient preferences for treatment cannot be ignored. McLawhorn also noted several assumptions had to be applied to construct the model.

“We are now using large state-wide and national databases to more closely examine bariatric surgery, morbid obesity, and total joint replacement in a rigorous way to [better] characterize the associations between weight loss surgery prior to total joint replacement and patient outcomes after joint arthroplasty,” he said. “In particular, we are trying to determine if there is an optimal time interval between the two procedures and if there are specific bariatric procedures [that] are more beneficial than others in terms of reducing the risk of complications and improving patient outcomes after total joint replacement. Those associations are not well-defined and should be explored, first in retrospective style studies and eventually in a prospective way.” – by Casey Tingle

Disclosure: McLawhorn reports no relevant financial disclosures.