The value of a decision aid for shared decision making in surgical and orthopedic practice. A multicenter costeffectiviness analysis.

Background: Practice variation and varying patient reported outcomes in the four most performed orthopedic and surgical operations demonstrate inefficient use of care. Shared decision making has the potential to increase patient satisfaction and reduce the operation rate. Here we evaluate decision aids in orthopedic and surgical practice to improve patient outcome and to reduce the number of operations and prevent ineffective surgery. Research question: What is the effect of an online decision aid in patients with knee or hip osteoarthritis, gallstones or an inguinal hernia on the proportion of operations, patient reported outcomes and quality of shared decision making during 6 months follow up in comparison to patients managed without a decision aid (usual care). Hypothesis: The operation rate following implementation of an online decision aid in patients with knee or hip osteoarthritis, gallstones or an inguinal hernia is lower than the usual care and patient satisfaction and quality of shared decision making will increase. An estimated minimal reduction of 5 to 10% for each condition in operation rates is associated with a potential cost savings ranging from €25.6 to €40.9 million annually. Study design: Stepped wedge design (according to predefined implementation schedule). Study population: Patients referred to an orthopedic surgeon with advanced hip or knee osteoarthritis or to a general surgeon for gallstones or inguinal hernia. Intervention: A shared decision making strategy executed after a stepwise implementation of the decision aids according to a standardized protocol in patients with knee and hip osteoarthritis, gallstones or an inguinal hernia. Usual care / comparison: The comparison strategy is usual care. This is decision making based on current guidelines, personal experiences and preferences. Outcome measures: Primary outcome is the proportion of surgical interventions before and after implementation. Secondary outcomes are changes in quality of the shared decision making process, patient reported outcomes, and costs. Sample Size: Hip osteoarthritis ( N=95 patients per hospital / per 3-month period); Knee osteoarthritis (N=120 patients per hospital / per 3 month period); Gallstones (N=45 patients per hospital /per 3-months period); and Inguinal hernia (N=50 patients per hospital / per 3-month period). Nine hospitals agreed to participate in the study. Six intervention hospitals with a stepwise implementation of the intervention and three control hospitals to monitor time trends of surgery rates throughout the entire study period. Data analysis: Descriptive analyses will be used to describe the population. Mixed models will be used to analyse effect sizes and time trends. Time schedule: Total 30 months - 3 months of start-up, 3 months baseline measurement, 15 months of implementation of the intervention, 6 months of follow-up after implementation of the intervention in the last hospital, 3 months of data analysis and reporting.