Mechanical Age-Related Differences in the Human Cadaveric Annulus Fibrosus

This study investigated how aging influences the mechanical properties of the human annulus fibrosus using a human cadaveric model. Discs (T10–S1) from donors aged 53–90 were dissected into single-layer, bilayer, and multilayer annular samples. Single and bilayer specimens were tested in tension to characterize intralamellar and interlamellar mechanics, while multilayer samples underwent 180° peel tests to assess adhesive strength. Results showed that with increasing age, stiffness and stress parameters (Young’s modulus, stress at failure, and stress at 15% strain) significantly decreased in single and bilayer samples, indicating progressive weakening and compliance of annular collagen matrices. However, the peel tests revealed no age-related changes in interlamellar adhesion, suggesting the interlamellar matrix remains relatively unaffected by aging. These findings advance understanding of disc degeneration mechanics and identify matrix-specific aging vulnerabilities in human spines.