Mylène Jansen

Return to sport and work after KJD and HTO 91 5 year postoperatively. The sum of the item scores can be converted to a 0–100 score, where 0 represents the worst and 100 the best possible score. 33 A score of 71 or more is classified as being satisfied with their work ability with respect to the knee, while a score of 50 or less is considered as being unsatisfied. In addition, job titles were classified as light, medium or heavy workload by 2 occupational experts, who independently scored all jobs based on work-related physical demands of the knee. 34,35 A more detailed description of the questionnaire can be found in a previous publication. 36 Statistical analysis A sample size calculation was performed for the primary RCT. 24 For the present study, a convenience sample was used, aiming for a response rate >80%. Demographic data, pre- and postoperative sport- and work participation were analyzed using descriptive statistics. Also, descriptive statistics were used to analyze time to RTS and RTW, frequency and duration of sports participation. RTS rate was calculated by selecting all patients that participated in 1 or more sports either presymptomatically, preoperatively or both, and calculating which percentage of these patients could RTS at 6 months and 1 year postoperatively. Given the 6-week delay in return to normal activities due to the distraction device, differences between KJD and HTO in RTS and RTW rates were analyzed at 2, 4 and 6 months, and at 1 year follow- up, using the chi-square test. To test for differences in sports participation (level, frequency, hours/week) and work participation (hours/week, workload) between groups, the Fisher’s exact test was used. The Wilcoxon Signed-Rank test was used to compare presymptomatic and postoperative Tegner scores within groups. To test for differences between the KJD and HTO group, the Mann-Whitney U test was used for the ΔTegner score (postoperative minus presymptomatic score) and the unpaired t -test was used for the postoperative Lysholm score. The change in mean total WORQ scores from preoperative to final follow-up was compared using the unpaired t -test; mean and standard deviations (SD) are given. Next, the scores of all WORQ items at the 3 time points were dichotomized to determine how many patients experienced severe difficulty with a work-related knee-demanding activity. “Severe difficulty” and “extreme difficulty/unable to perform” were classified as “severe difficulty”. “Moderate difficulty,” “mild difficulty” and “no difficulty” were classified as “no severe difficulty”. A p- value of p< 0.05 was considered significant. All statistical analyses were performed with SPSS for Windows (Version 24.0. Armonk, NY: IBM Corp.). Results Out of 62 eligible patients, 55 patients responded (89%) and 51 patients completed the questionnaire (82%). Two KJD patients and 2 HTO patients declared that they were not interested in participation. Baseline characteristics of the respondents are presented in Table 1.