Mylène Jansen

KJD in regular care 115 6 efficacy, and characteristics of these patients were compared to the entire group of regular care patients. Statistical analysis Characteristics were compared between regular care and clinical trial patients using independent t -tests or, in case of categorical variables, chi-square tests. WOMAC data before and 1 year after treatment was compared for both groups separately, using paired samples t -tests. The 1-year WOMAC values were compared and tested between groups for clinical significance, defined as a difference of more than 15 WOMAC points 20 , and for statistical significance using linear regression, corrected for baseline values and possible significantly different baseline or treatment characteristics. The influence of different baseline characteristics on the 1-year change in total WOMAC score, corrected for baseline WOMAC, was identified using linear regression. Being a responder to KJD treatment was analyzed according to the Outcome Measures in Rheumatology-Osteoarthritis Research Society International (OMERACT- OARSI) responder criteria, defined as an increase of ≥50% and ≥20 points in WOMAC pain or function scales, or a ≥20% and ≥10-point improvement in both scales, and potential predictors identified. 21 For all values, mean and standard deviations (SD) are given, and for all changes over time the mean change and 95% confidence interval (95%CI) are shown. P- values <0.05 were considered statistically significant. IBM SPSS Statistics version 25 (IBM Corp; Armonk, NY) was used for all statistical analyses. Results Baseline characteristics Before 2018, 84 patients were treated with KJD in regular care in our hospital and all accepted to participate in the orthopedic standard registry. Between 2006 and 2014, 62 patients were treated in the 3 trials combined. The baseline characteristics of both groups are shown in Table 1, showing a different distraction duration between both groups, which was longer for clinical trial patients (48.1 (SD 8.1) days; regular care 45.3 (4.3); p= 0.019), but shorter when excluding the OPS patients who received distraction for 8 instead of 6 weeks (RCT 42.8 (2.3); regular care 45.3 (4.3); p< 0.001). In 1 patient in the regular care group compartment syndrome occurred and the distraction frame was removed after 2 days. This patient was excluded from the distraction duration in Table 1, since no full treatment was applied.