Statistical analysis
REGRESSIONS
Shapiro–Wilk test was used to check the normality of the data. To evaluate the differences of the structural and radiological outcomes before and after HTO, paired Wilcoxon signed-rank tests and paired T tests were used for non-normally and normally distributed data, respectively. To evaluate the differences of the clinical outcomes at baseline and different follow-up time points, Friedman tests and repeated measures ANOVA (analyses of variance) were performed for non-normally and normally distributed data, respectively. For repeated measures ANOVA, Mauchly’s tests were conducted to check if the sphericity assumption was met, and Greenhouse–Geisser corrections were applied if the sphericity assumption was violated. Paired Wilcoxon signed-rank tests and paired T tests with Bonferroni multiple testing correction method were used as post hoc analyses for Friedman tests and repeated measures ANOVA, respectively. Data were reported as mean ± standard deviation (SD) or median (interquartile range [IQR]).To model the change of the outcomes during the follow-up period, both linear and nonlinear mixed-effects models were used. The models with lower Akaike information criterion with correction for small sample sizes (AICc) and Bayesian information criterion (BIC) were considered to better fit the data. To further examine the factors that potentially influenced the treatment effects, covariates including age, sex, BMI, KL grade, femorotibial angle at baseline, posterior tibial slope angle at baseline, and symptoms severity at baseline were included in the models. Stepwise regressions, AICc, and BIC were used to select the optimal multivariate mixed-effects models. To validate the robustness of the multivariate models, the collinearity between the covariates were tested for significance. The values of correlation coefficient between 0 and 0.3 (0 and − 0.3) indicate a weak positive (negative) linear relationship, those between 0.3 and 0.7 (− 0.3 and − 0.7) indicate a moderate positive (negative) linear relationship, and those between 0.7 and 1.0 (− 0.7 and − 1.0) indicate a strong positive (negative) linear relationship [