Tea Polyphenol Attenuates Oxidative Stress-Induced Degeneration of Intervertebral Discs by Regulating the Keap1/Nrf2/ARE Pathway

Table 2

Pfirrmann system.

Grade	Pfirrmann system
	Structure	Signal	Disc height	Distinction between nucleus and anulus
I	Homogeneous	Bright hyperintense white signal intensity	Normal	Clear
II	Inhomogeneous	Hyperintense white signal	Normal	Clear, with or without horizontal gray bands
III	Inhomogeneous	Intermediate gray signal intensity	Normal or slightly decreased	Unclear
IV	Inhomogeneous	Hypointense dark gray signal intensity	Normal or moderately decreased	Lost
V	Inhomogeneous	Hypointense black signal intensity	Collapsed	Lost