Discussion
Obesity, weight loss
OBESITY
This study reports on changes to willingness for surgery following an education, exercise and weight loss intervention and extrapolates longer-term cost implications from a PHI perspective. Such interventions are core treatments for knee OA and have been shown to reduce willingness for surgery globally [Previous international studies have found similar interventions to be cost-effective or cost-saving when compared to the standard care pathway [Our study helps decision makers better understand the economic implications and potential benefits of delivering similar interventions. The model presents evidence to suggest that, when at least 60% of willing participants go on to have surgery in the following 5 years, BKBM may be a dominant intervention: it improves participant health (as demonstrated by the RCT) and delivers a return on investment. Interventions such as BKBM allow PHIs to take an active part in member health and presents a potential win-win for PHIs, members, and the broader health system.There are important limitations to our study. First, due to the unavailability of long-term surgical data from the PHI, our study explored orthopaedic cost consequences under a range of possible probability levels for surgery given a participant’s willingness status. To address the uncertainty in this parameter estimate, we have conducted a break-even analysis to test the variability of our results. The unavailability of long-term surgical PHI data also meant our model assumed a fixed relationship between willingness states and progression to surgery.Second, the economic evaluation considered a narrow set of benefits relating to reduced TKR healthcare utilisation; there are a range of further benefits to participants and payers that have not been considered, such as the impact of weight loss, improved health and lower non-TKR healthcare utilization [Third, results presented in this study do not account for possibility that participants become more likely to undergo surgery after achieving weight loss. Obesity is a significant predictor of surgical failures, making it a concern to most surgeons [Fourth, our study assumed a fixed transition probability for TKR over the 5-year study period. Research into the progression to surgery suggests there are multiple pathways, some faster and some slower, so on balance we believe this is a reasonable assumption [Finally, by adopting a PHI payer perspective, the transferability of our findings in public sector settings may be low. Participants in our study had access to surgery and were more likely to be engaged with their personal health.