The annulus fibrosus of the intervertebral disc is comprised of layers of circumferential lamellae. Previous studies have also identified radial structures dubbed translamellar cross-bridges, but the full extent, concentration, interconnection and their mechanical contribution, are poorly understood. The objectives of this study were to use a combination of magnetic resonance imaging (MRI) and optical coherence tomography (OCT) to document the cross-bridges in 3D and to measure the strength and stiffness of the cross-bridges using a peel test between lamellae. The images produced show an interconnected network of bridge structures throughout the annulus. The mechanical contribution proved difficult to separate from the remaining interlamellar matrix contribution, but comparing load curves between sample thicknesses, and with OCT images of the samples, did suggest discrete, radial structures influence the peel strength. This study will contribute to future tissue engineering efforts by increasing the current understanding of the native disc structure.
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