The effect of degeneration on intervertebral disc herniation: a human ex vivo study with multiscale structural analysis
File(s)
Author(s)
Slater, Thomas D
Farinelli, Carlotta
Raftery, Kay A
La Barbera, Luigi
Newell, Nicolas
Type
Journal Article
Abstract
Study design:
Human cadaveric structural investigation of mechanical load-induced acute disc herniation across degeneration grades.
Objective:
To understand the structural effects of loading to failure in discs of different degeneration grades for inferring herniation mechanisms.
Summary of background data:
Animal models have been extensively used to study disc herniation in non-degenerate discs, but their relevance to human pathology is unclear and validation in human discs is limited. Studying microstructural failure in human discs is therefore essential for investigating mechanisms of herniation and how these are affected by degeneration.
Methods:
Human cadaveric intervertebral discs (n=16) were imaged using MRI, graded for degeneration using the Pfirrmann classification and assigned to either loaded or unloaded groups. Loaded discs were flexed (13°) to physiological limits and loaded to failure (~90% of disc height). Discs were sectioned and examined macroscopically and microscopically to quantify structural failures (graded ordinally 0-3), facilitating comparison across degeneration grades.
Results:
Direct comparison of MRI, macroscopic, and microscopic images provided the most comprehensive depiction of the human disc to date. Loaded discs exhibited significantly increased damage scores across radial tears (ordinal rating: 1.46 vs 0.92, P=0.045), lamellae separations (1.12 vs 0.78, P=0.043), endplate tears (0.85 vs 0.50, P=0.033), and nucleus clefts (1.51 vs 0.82, P=0.008). Increased disc degeneration was associated with increased annulus bulging scores (0.42 vs 1.72, P<0.013), and larger clefts being present in the discs.
Conclusions:
The standardised mechanical loading applied produced consistent macrostructural and microstructural failure of the disc. The findings motivate a hypothesis that mechanisms of herniation may vary with degeneration. Mildly degenerate discs may herniate via extrusion of inner disc material, whereas more degenerate discs may herniate through posterior annulus disc bulging. Treatment strategies, including surgical timing and expectations for spontaneous resorption, may therefore be tailored by degeneration grade.
Human cadaveric structural investigation of mechanical load-induced acute disc herniation across degeneration grades.
Objective:
To understand the structural effects of loading to failure in discs of different degeneration grades for inferring herniation mechanisms.
Summary of background data:
Animal models have been extensively used to study disc herniation in non-degenerate discs, but their relevance to human pathology is unclear and validation in human discs is limited. Studying microstructural failure in human discs is therefore essential for investigating mechanisms of herniation and how these are affected by degeneration.
Methods:
Human cadaveric intervertebral discs (n=16) were imaged using MRI, graded for degeneration using the Pfirrmann classification and assigned to either loaded or unloaded groups. Loaded discs were flexed (13°) to physiological limits and loaded to failure (~90% of disc height). Discs were sectioned and examined macroscopically and microscopically to quantify structural failures (graded ordinally 0-3), facilitating comparison across degeneration grades.
Results:
Direct comparison of MRI, macroscopic, and microscopic images provided the most comprehensive depiction of the human disc to date. Loaded discs exhibited significantly increased damage scores across radial tears (ordinal rating: 1.46 vs 0.92, P=0.045), lamellae separations (1.12 vs 0.78, P=0.043), endplate tears (0.85 vs 0.50, P=0.033), and nucleus clefts (1.51 vs 0.82, P=0.008). Increased disc degeneration was associated with increased annulus bulging scores (0.42 vs 1.72, P<0.013), and larger clefts being present in the discs.
Conclusions:
The standardised mechanical loading applied produced consistent macrostructural and microstructural failure of the disc. The findings motivate a hypothesis that mechanisms of herniation may vary with degeneration. Mildly degenerate discs may herniate via extrusion of inner disc material, whereas more degenerate discs may herniate through posterior annulus disc bulging. Treatment strategies, including surgical timing and expectations for spontaneous resorption, may therefore be tailored by degeneration grade.
Date Issued
2026-09-01
Date Acceptance
2026-04-10
Citation
Spine Open, 2026, 2 (3)
ISSN
3066-8905
Publisher
Lippincott, Williams & Wilkins
Journal / Book Title
Spine Open
Volume
2
Issue
3
Copyright Statement
© 2026 The Author(s). Published by Wolters Kluwer Health, Inc. This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
10.1097/bn9.0000000000000103
Subjects
intervertebral discs
mechanical loading
disc herniation
degeneration
nucleus pulposus
annulus fibrosus
endplate
Pfirrmann grading
structural injury
microstructural analysis
cadaveric
Publication Status
Published
Article Number
e0103
Date Publish Online
2026-06-25