The relationship between MRI and histology in a rat model of intervertebral disc degeneration

Objectives: To establish a slowly progressive, reproducible rat model of disc degeneration and investigate the relationship between MRI and histology in the long-term progression of disc degeneration. Materials and methods: The intervertebral discs of caudal spine in rats were punctured laterally, using 20-gauge sterile needles, 5 mm depth from the skin to the middle of the appropriate disc. The discs of tails were analyzed by in vivo MRI and histology before surgery and at 4, 8, 12, and 24 weeks post-surgery. Results: Based on histological grading system, the discs were categorized as normal, moderately degenerated, and severely degenerated, and histologic score of treatment groups was significantly correlated with the time post-stab. MRI measurements showed a progressive decrease in T2 signal intensity and MRI index starting at 4 weeks post-puncture. Furthermore, the degenerated discs did not recover spontaneously, as shown by decrease in T2 signal intensity and MRI index. We found significant correlation between the grade scale of histological score and MRI measurements. Conclusions: We demonstrated a correlation between grade scale of histological score and MRI measurements in a slow and progressive disc degeneration rat model. Therefore, MRI could provide a convenient, non-invasive, reproducible, and cost-effective option to monitor the progression of intervertebral disc degeneration.