Mylène Jansen

Cartilage collagen structure after KJD and HTO using T2-mapping 307 15 the most affected compartment (MAC) and least affected compartment (LAC) of the joint, which were determined at patient inclusion, results were separated in the MAC and LAC femur and tibia (instead of medial and lateral femur and tibia). For both KJD groups (for KJD TKA and for KJD HTO ), the changes over time were calculated using repeated measures ANOVA. For differences in changes between these groups, mixed ANOVA was used, correcting for significantly different baseline characteristics. For the HTO group, the changes over time were calculated using paired t -tests, since only 2 time points were available. For differences in 2-year changes between HTO and KJD HTO , linear regression was used, correcting for baseline values and significantly different baseline characteristics. Pearson correlations were calculated between 1- and 2-year changes in T2 values and volumes, for each compartment and group separately. Since different time points were available for KJD patients, HTO patients and OAI patients, regression coefficients were calculated for the average tibia and average femur T2 relaxation times for each patient separately, including all available time points, to represent changes over time (ms/year). These coefficients were used to calculate the influence of baseline characteristics on the change in tibia and femur T2 relaxation times for each of the 3 treated patient groups and the untreated OAI patients separately, using linear regression. Each characteristic and baseline value was evaluated in separate models. To compare treated patients with the matched OAI untreated patients, regression coefficients were compared using linear regression, correcting for statistically significant differences in baseline characteristics between the groups. Continuous variables are given with mean and standard deviation, categorical variables with n and %; changes over time are given with mean change and 95% confidence interval (CI). For all tests, p< 0.05 was considered statistically significant. Results Patients For the KJD patients, 4 patients did not have complete T2-mapping datasets because of either motion artifacts, refusal for follow-up or conversion to another treatment (HTO or TKA), resulting in 8 KJD TKA and 8 KJD HTO patients. For the HTO patients, 3 patients did not receive the extended imaging at 2 years: 1 was MRSA positive and no imaging was performed, 1 did not want the metal plate removed at 18 months, and 1 converted to another treatment. As such, 17 HTO patients could be analyzed.