Mylène Jansen

356 Chapter 17 As no standardized (KIDA) radiographs were available in these SF patients, radiographs taken in regular care at baseline and around 1 year after treatment (range 276 – 433 days) were used to score osteophytes using the revised Altman score. 6 The correlation between Altman and KIDA in KJD RCT patients was tested and showed to be moderately good ( R= 0.669; p< 0.001; Supplementary Table S1). All images were scored for osteophytes in each of the 4 regions twice by 1 observer (SM), giving each compartment a grade from 0 (normal) to 3 (severe). The average of both scores was used and due to the wide follow-up range, the follow-up radiograph was linearly corrected (extrapolated) to 365 days with respect to the baseline radiograph. The separate compartment scores were summarized to obtain a 0 – 12 whole-joint scoring. Only patients with baseline and 1-year follow-up radiographs were included in the analyses. Statistical analyses For all continuous parameters, changes over time for separate patient groups were analyzed using paired t -tests or where more than 2 time points were available, repeated measures ANOVA. The influence of available predefined patient characteristics (age, sex, BMI and Kellgren-Lawrence grade) on osteophyte formation was tested with linear regression. For comparisons where in both groups more than 2 time points were available, mixed ANOVA was used instead. In SF patients, for the categorical Altman score per region, the Wilcoxon Signed Rank test was used to test changes over time. The changes in whole-joint osteophyte Altman score and in synovial fluid biomarkers were analyzed with paired t -tests, and the Pearson correlations between total joint osteophyte Altman and biomarker baseline values and changes over time were calculated. Finally, SF patients were divided in 3 groups (trichotomized) based on an increase, no change or decrease in total osteophyte Altman score over time. The change in TGF β -1 and in IL-6 during the distraction period was compared between these 3 groups using a Kruskal-Wallis test, because of the resulting limited number of patients per group. Normal distributionwas verified for all outcome parameters; in case outcomes were not normally distributed, log transformation was performed. For all tests, a p- value <0.05 was considered statistically significant. Absolute values are presented with mean ± standard deviation (SD) while changes over time are presented as mean change and 95% confidence interval (95%CI). Results Patients Of all KJD patients, 1 was excluded before surgery due to inoperability, 3 KJD patients were lost to follow-up after receiving a different surgical treatment during follow-up and 1 patient