Mylène Jansen

134 Chapter 7 panel, on the user-friendliness of the distraction device as experienced during treatment. Device characteristics relevant for analysis of user-friendliness and therewith for improvement of KJD treatment were incorporated in the questionnaires. The questionnaire consisted of 25 questions on difficulties performing activities regarding clothing, sleeping, wound care, general daily activities, and complications and were equal for the 2 devices (supplementary file I and Table 4). The effect of complications on the experienced user-friendliness was part of the analysis. Within the cohort available for analysis, 3 patients were treated with both the CD device and the DD device. These patients received a questionnaire for a direct comparison of experiences during treatment between the CD and the DD device (supplementary file II). Statistical analysis Baseline characteristics were compared between groups using independent t -tests or, in case of categorical variables, chi-square tests. Statistical testing for significance of all outcome parameters was performed with independent t -tests and results are displayed using mean and standard deviations (SD). In case of non-normal distribution, Mann-Whitney U tests were used instead of independent t -tests and results are displayed using median and interquartile range (IQR). For categorical variables with only 2 categories (questions 21 and 22; Table 4), chi-square test were used and the number of occurrences (and % of the total amount of patients) are given. P -values <0.05 were considered statistically significant. IBM SPSS Statistics version 25 (IBM Corp; Armonk, NY) was used for all statistical analyses. Results Patients The patients’ baseline characteristics are presented in Table 3. There were no statistically significant differences between the 2 groups regarding these baseline characteristics. Patient age ranged from 46–63 years in the CD group and 38–63 years in the DD group. Table 3 : Baseline characteristics of patients treated with knee joint distraction in this study CD device (n=22) DD device (n=22) P- value Age (years) 54.8 (4.8) 52.0 (6.7) 0.123 Male sex, n (%) 14 (64) 11 (50) 0.361* BMI (kg/m 2 ) 58.3 (3.9) 27.5 (2.9) 0.501 Left leg, n (%) 12 (55) 9 (41) 0.365* Mean and standard deviation or n (%) are given. P- values of continuous variables are calculated with independent t -tests and for categorical variables with chi-square tests (indicated with *). BMI: body mass index; CD: concept distraction; DD: dedicated distraction; SD: standard deviation.