Table 1 Histological grading scale criteria based on Norcross et al.28.

From: Aberrant spinal mechanical loading stress triggers intervertebral disc degeneration by inducing pyroptosis and nerve ingrowth

Scores

Nucleus pulposus (NP) symptoms

5

Large, bulging central cavity with abundant NP material; > 2/3 (IVD) height; smooth borders with minimal disruption

4

Slightly reduced central cavity size with some NP material present; > 1/3 IVD height and < 2/3 IVD height; minimal border disruption may be present

3

Markedly reduced and disrupted cavity with minimal NP material and compartmentalization; total cavity > 1/3 IVD height and < 2/3 IVD height

2

Severe disruption of NP with minimal cavity; total cavity < 1/3 IVD height but > 0; consists only of a few small pockets lined by NP-like cells

1

Complete obliteration of cavity with no NP-lined pockets

Scores

Annulus fibrosus (AF) symptoms

5

Discrete, well-opposed lamellae bulging outward with no infolding; minimal preparation defect with “simple radial clefting”

4

Discrete lamellae, less well-opposed; minimal infolding may be present; fibers remain well-organized, but with ‘‘complex radial clefting’’

3

Moderate to severe infolding of discrete, relatively well-opposed lamellae; moderate fragmentation of lamellae; AF fibers remain well organized

2

Severe infolding and distortion of poorly opposed lamellae; severe fragmentation of lamellae; small regions of disorganized fibrous material replacing central lamellae

1

Severe infolding, distortion, and fragmentation of lamellae; extensive amount of disorganized fibrous material replacing central lamellae

Scores

Cartilage endplate (EP) symptoms

5

Neatly arranged chondrocytes without any lesion or ectopic bone formation

4

Hyaline cartilage cells were replaced by the spindle-shaped chondrocytes, ectopic bone formation only located at the “junction”

3

Ectopic bone formation located at superior cartilage endplate with smooth cartilage surface

2

Ectopic bone formation located at whole cartilage endplate with smooth cartilage surface

1

Ectopic bone formation located at whole cartilage endplate with flawed cartilage surface

  1. This scale mainly scores the disruption of nucleus pulposus central cavity, cellularity and collagen fiber orientation of annulus fibrosus and the degree of ectopia ossification of cartilage endplate. Simple radial clefting = the presence of radial gaps between AF lamellae with minimal fragmentation; complex radial clefting = the presence of radial, transverse, and/or oblique gaps in the lamellae with significant fragmentation; junction = the triangle junction between the cartilage endplate and the annulus fibrosus.
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