Purpose: To evaluate disk degeneration in human and animal models by using a T1ρ magnetic resonance (MR) imaging technique to help in understanding the natural history and progression of intervertebral disk degeneration.
Materials and methods: After institutional review board approval was obtained, 80 subjects (54 men and 26 women; mean age ± standard deviation, 31.6 years ± 6.20) with 400 lumbar intervertebral disks were examined at MR imaging. With approval from the animal care committee, six rhesus monkeys received two levels of either annulus fibrosus puncture or pingyangmycin subendplate injection at L3-4 and L5-6 to mimic disk degeneration. Lumbar spines of all the animals were examined at radiography and MR imaging preoperatively and 1 day and 1, 3, 6, 9, and 13 months postoperatively. Pfirrmann grading system and T1ρ quantification were used to evaluate the degenerative degree of the disks of both humans and animals.
Results: The mean T1ρ values of lumbar intervertebral disks of human subjects were 136.0 msec ± 31.4 and 76.1 msec ± 14.2 at Pfirrmann grades II and III, respectively. The T1ρ values in lumbar intervertebral disks of the rhesus monkey models of disk degeneration had a rapid decrease from approximately 110 msec to 80 msec and then tended to stabilize after operation. There was a large T1ρ value decrease between Pfirrmann grades II and III in human subjects that coincided with the rapid degeneration process of lumbar intervertebral disks in the rhesus monkeys. Pfirrmann grades were significantly correlated with T1ρ values in both humans (r = -0.681, P < .001) and rhesus monkeys (r = -0.824, P < .001).
Conclusion: The data demonstrate that rapid intervertebral disk degeneration occurs early in the degenerative cascade, between Pfirrmann grades II and III.