A Multiscale Ex Vivo Method to Investigate Intervertebral Disc Strain and Fiber Recruitment in Anterolateral Bending Using 9.4T MRI-DVC and DIC Microscopy.
biomechanical · Level V
Where this comes from
- Record sourced from PubMed, PMID 41459418.
- Also identified by DOI 10.1002/jsp2.70154 and PMC identifier 12740184.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Ex vivo, multiscale analysis of disc strain using ultrahigh-field MRI-based digital volume correlation (MRI-DVC) and differential interference contrast (DIC) microscopy. To evaluate the relationship between three-dimensional strain distributions and collagen fiber recruitment in porcine cervical intervertebral discs under flexion and lateral bending. 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. 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). 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. 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.