Table 2.

Histological grading scheme for intervertebral degeneration model

I. Cellularity of the annulus fibrosus

Grade

Fibroblasts comprise more than 75 % of cells

Neither fibroblasts nor chondrocytes comprise more than 75 % of cells

Chondrocytes comprise more than 75 % of cells

II. Morphology of the annulus fibrosus

Grade

Well-organized collagen lamellae without ruptures or serpentine

Inward bulging, ruptured or serpentine fibers in less than one-third of the anulus

Inward bulging, ruptured or serpentine fibers in more than one-third of the anulus

III. Border between the annulus fibrosus and nucleus pulposus

Grade

Normal, without any interruption

Minimal interruption

Moderate or severe interruption

IV. Cellularity of the nucleus pulposus

Grade

Normal cellularity with stellar-shaped nuclear cells evenly distributed throughout the nucleus

Slight decrease in the no. of cells with some clustering

Moderate or severe decrease (>50 %) in the number of cells with all the remaining cells clustered and separated by dense area of proteoglycans

V. Morphology of the nucleus pulposus

Grade

Round, comprising at least half of the disc area in midsagittal sections

Round or irregularly shaped, comprising less than one quarter to half of the disc area in midsagittal sections

Irregularly shaped, comprising less than one quarter of the disc area in midsagittal sections

The scale is based on 5 categories of degenerative change, with scores ranging from 5 points (1 in each category) for a normal disc to 15 points (3 in each category) for a severely degenerated disc