Statistical analysis
SECONDARY
To test whether the time-related changes within primary and secondary outcome measures were dependent on patient group, a linear mixed model was conducted for each parameter. “Time” (0, 0.75, 1.5, 3, 6, 9, 12, 18 and 24 months) and “group” (steroid vs. placebo) were defined as fixed factors, with the variable of interest being labeled as repeated measurement. “Patient ID” was chosen as the random effect (modeling random intercepts).By calculating a linear mixed model (LMM), missing values of a patient did not lead to the patient’s exclusion from data analyses. The interaction of “group x time” was defined as the target effect. In case of a significant interaction, pairwise comparisons were conducted to test for significant differences between groups at each point in time (resulting in 9 post-hoc independent t-tests). All pairwise comparisons were Holm corrected to avoid alpha inflation (correction for multiple comparisons).Continuous variables were tested for normal distribution Effect sizes are provided in terms of RCategorical data are displayed as absolute and relative frequencies (N/%) and compared The effect of surgery on the primary and secondary outcome measures was calculated as the change between timepoint 0 and 0.75.