Fig. 8

Changes in disc height index (DHI) after surgery. There was a slow, progressive decrease in the disc height of operated discs over time. The DHI in both the 16G puncture and annulus trephination groups were significantly lower than the DHI of the control group after surgery (**P < 0.01, vs. control group). The DHI of the PLGA implantation group was comparable to that of the control group and significantly higher than those in the 16G puncture group and annulus trephination group over the 6 months (*P < 0.05, vs. 16G puncture group or annulus trephination group)