A multiscale ex vivo method to investigate intervertebral disc strain and fiber recruitment in anterolateral bending using 9.4T MRI-DVC and DIC microscopy
OA Location
Author(s)
Slater, TD
Raftery, KA
van Heeswijk, VM
Thambyah, A
Newell, N
Type
Journal Article
Abstract
Study Design
Ex vivo, multiscale analysis of disc strain using ultrahigh-field MRI-based digital volume correlation (MRI-DVC) and differential interference contrast (DIC) microscopy.
Objective
To evaluate the relationship between three-dimensional strain distributions and collagen fiber recruitment in porcine cervical intervertebral discs under flexion and lateral bending.
Summary of Background Data
Flexion combined with lateral bending is often linked to disc herniation, yet the strain patterns and fiber-level changes in the annulus fibrosus are not well understood. Multiscale characterization is essential to uncovering failure mechanisms.
Methods
Four porcine cervical motion segments were scanned in neutral and anterolaterally (AL)-bent postures using 9.4T MRI, with 3D strains calculated via DVC. Samples were sectioned and imaged with DIC microscopy to quantify collagen fiber recruitment based on fiber crimp patterns, using a crimp grading scale (0 = fully straight, 1 = semi-crimped, 2 = uncrimped).
Results
MRI-DVC revealed an inhomogeneous strain distribution in AL-bent discs, with higher magnitudes compared to the neutral discs. Fiber uncrimping was greater in the AL-bent discs (mean crimp grade: 0.44, mostly straight) compared with the neutral discs (1.56, predominantly crimped). Across the bending axis, the anterior-right region exhibited higher strains than the posterior-left (minimum principal strain ~25% greater), which correlated with the presence of sequential lamellae having straight and fully-crimped fibers. A greater amount of fiber uncrimping was observed in the posterior-left than anterior-right disc regions.
Conclusion
This study confirms the suitability of MRI-DVC combined with DIC microscopy for relating macroscopic strains to microscopic fiber crimp, and for identifying regions of high strain across multiple length scales. Under AL-bending, this methodology revealed that the disc's posterior region exhibited taut fibers, which may contribute to its susceptibility to herniation.
Ex vivo, multiscale analysis of disc strain using ultrahigh-field MRI-based digital volume correlation (MRI-DVC) and differential interference contrast (DIC) microscopy.
Objective
To evaluate the relationship between three-dimensional strain distributions and collagen fiber recruitment in porcine cervical intervertebral discs under flexion and lateral bending.
Summary of Background Data
Flexion combined with lateral bending is often linked to disc herniation, yet the strain patterns and fiber-level changes in the annulus fibrosus are not well understood. Multiscale characterization is essential to uncovering failure mechanisms.
Methods
Four porcine cervical motion segments were scanned in neutral and anterolaterally (AL)-bent postures using 9.4T MRI, with 3D strains calculated via DVC. Samples were sectioned and imaged with DIC microscopy to quantify collagen fiber recruitment based on fiber crimp patterns, using a crimp grading scale (0 = fully straight, 1 = semi-crimped, 2 = uncrimped).
Results
MRI-DVC revealed an inhomogeneous strain distribution in AL-bent discs, with higher magnitudes compared to the neutral discs. Fiber uncrimping was greater in the AL-bent discs (mean crimp grade: 0.44, mostly straight) compared with the neutral discs (1.56, predominantly crimped). Across the bending axis, the anterior-right region exhibited higher strains than the posterior-left (minimum principal strain ~25% greater), which correlated with the presence of sequential lamellae having straight and fully-crimped fibers. A greater amount of fiber uncrimping was observed in the posterior-left than anterior-right disc regions.
Conclusion
This study confirms the suitability of MRI-DVC combined with DIC microscopy for relating macroscopic strains to microscopic fiber crimp, and for identifying regions of high strain across multiple length scales. Under AL-bending, this methodology revealed that the disc's posterior region exhibited taut fibers, which may contribute to its susceptibility to herniation.
Date Issued
2025-12-01
Date Acceptance
2025-12-15
Citation
JOR Spine, 2025, 8 (4)
ISSN
2572-1143
Publisher
Wiley
Journal / Book Title
JOR Spine
Volume
8
Issue
4
Copyright Statement
© 2025 The Author(s). JOR Spine published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/41459418
PII: JSP270154
Subjects
DIC microscopy
MRI DVC
annulus fibrosus
anterolateral bending
ex vivo
fiber recruitment
microstructural analysis
multiscale biomechanics
porcine intervertebral disc
strain distribution
Publication Status
Published
Coverage Spatial
United States
Article Number
e70154
Date Publish Online
2025-12-25