Statistical analysis
SENSITIVITY
Results are reported as means and mean difference along with their 95% confidence intervals and tested using independent sample t test. Differences in costs and effectiveness between the two groups were drawn and displayed graphically with cost-effectiveness planes. Incremental cost-utility (ICUR) and cost-effectiveness (ICER) ratios were calculated by dividing the mean difference in total costs per patient between treatment groups by the mean difference in QALYs and in OMAS, respectively. Therefore, ICER is the price in euro’s per point difference on the OMAS.Missing data were handled according to the recent paper by Brand et al. [The confidence intervals of the ICER and the cost-effectiveness plane were based on bias-corrected and accelerated non-parametric bootstrapping of 1000 bootstrap samples after combining the multiple data sets into one mean single imputation [In addition to the primary CUA and CEA analyses, preplanned subgroup-analyses were performed for patients younger/older than 60 years old and for patients with/without a SSI. Sensitivity analyses were performed by varying medical costs of screw removal, outpatient clinic visits, emergency room visits and revalidation clinic admissions by 30%. Analyses were performed using R version 3.6.1 (R Foundation for Statistical Computing, Vienna, Austria).