Spss 20.0 for windows pc version

SPSS 20.0 for Windows PC version (SPSS Inc., Chicago, IL) was used for statistical analysis. Independent t test was conducted to compare the age between the operation group and the control group, and χ² test was conducted to compare the sex between the two groups. One-way analysis of variation (ANOVA) was conducted to compare ADI, CCA, CMA, and SLMI between the pre-operative and post-operative conditions of the operation group and the control group. P < 0.05 was considered as statistical difference.

Statistical analysis was completed using SPSS 20.0 for Windows PC version (SPSS Inc., Chicago, IL). The kappa value was calculated to determine interobserver agreement regarding the Pfirrmann grade. Data from μ-CT scans were compared with the Kruskal–Wallis test. The Mann–Whitney test was applied to compare data between any two groups. Differences in osteogenic mRNA expression in different regions of the removed discs (posterior vs. anterior) were analyzed by paired t tests. Differences in the posterior portion of removed intervertebral discs of different Pfirrmann grades were analyzed by one-way analysis of variance (ANOVA), and comparisons of data between discs of any two grades were completed with least squares difference (LSD) tests. P < 0.05 was considered statistically significant, except in the Mann–Whitney test for which a corrected P < 0.007 as statistically significant. The corrected P value in the Mann–Whitney test was calculated using the following formula: $\mathrm{P}\text{'}=\frac{\mathrm{P}}{{\mathrm{C}}_{\mathrm{n}}^2+1}$
where P’ indicates the corrected P value (P = 0.05), and “n” represents the number of groups, which was 4 in our study. P’ was approximately 0.0071 based on the formula, and thus, we defined P’ < 0.007 as statistically significant.