Fig. 4: Magnetic resonance imaging (MRI) analysis.

A Representative T2-weighted, mid-sagittal images of lumbar intervertebral discs (IVDs) in the UPAL gel implantation group and control group preoperatively and at 24 and 96 weeks after surgery. B Pfirrmann grading and the disc height index are shown. Box plots show the median (center line), 25th–75th percentiles (box edges), and range within 1.5 × interquartile range (whiskers); outliers are displayed as dots. **P < 0.01 between the two groups; P-values were determined with the Mann–Whitney U test. C, D T1ρ, T2*, and apparent diffusion coefficient (ADC) values derived from diffusion-weighted images of the IVDs are shown. T1ρ, T2*, and ADC values of lesional IVDs were normalized by the normal IVD values and evaluated for comparison. C Results of patients who underwent T1ρ, T2*, and ADC from preoperatively to 96 weeks postoperatively to evaluate within-group changes over time in each group. Data are presented as mean ± 95% confidence interval (CI), *P < 0.017 between each time point; P-values were determined with one-way analysis of variance with post-hoc tests using the Bonferroni paired t test. D Data obtained from MR images of all cases, including missing values, to compare the two groups at each time point. Box plots show the median (center line), 25th–75th percentiles (box edges), and range within 1.5 × interquartile range (whiskers); outliers are displayed as dots. *P < 0.05 between the two groups at each time point; P-values were determined with an unpaired two-tailed t test or Mann-Whitney U test. w, weeks.