TABLE 3.

Histological rating scale.

Content	Grade	Grade Description
I. Annulus fibrosus	1	Normal pattern of fibrocartilage lamellae (U-shaped in the posterior aspect and slightly convex in the anterior aspect) without ruptured fibers and without a serpentine appearance anywhere within the annulus
	2	Ruptured or serpentine-patterned fibers in less than 30% of the annulus
	3	Ruptured or serpentine-patterned fibers in more than 30% of the annulus
II. Border between the annulus fibrosus and nucleus pulposus	1	Normal
	2	Minimally interrupted
	3	Moderate/severe interruption
III. Cellularity of the nucleus pulposus	1	Normal cellularity with large vacuoles in the gelatinous structure of the matrix
	2	Slight decrease in the number of cells and fewer vacuoles
	3	Moderate/severe decrease (>50%) in the number of cells and no vacuoles
IV. Matrix of the nucleus pulposus	1	Normal gelatinous appearance
	2	Slight condensation of the extracellular matrix
	3	Moderate/severe condensation of the extracellular matrix

*The histological rating scale is based on four types of degenerative changes, with scores ranging from four points for normal discs (1 point per class) to 12 points for severe disc degeneration (3 points per class).