Experimental evaluation and constitutive modelling of cervical spine ligaments under low and high strain rates

Abstract

Abstract In the paper the mechanical behavior under low (0.5 s⁻¹) and high-strain rate (50 s⁻¹) of four human cervical spine ligaments, anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), ligamentum flava (LF), and capsular ligament (CL), harvested from elderly donors (70–90 years) is investigated. Results highlight that the PLL, LF, and CL exhibit statistically significant increases in stiffness and elastic modulus under high-strain loading. An increase in the failure force was observed only for the PLL and LF at 50 s⁻¹. Meta-regression analyses revealed that age exerts a negative influence on certain mechanical parameters, emphasizing the need for age-matched biomechanical data in both clinical and computational studies. A visco-hyperelastic constitutive model was fitted to the experimental stress-stretch curves, capturing both low-strain and high-strain rate responses with high goodness-of-fit metrics. Presented results advance understanding of ligament mechanics in older populations and offer valuable data for improving mathematical models aimed at injury prediction, particularly for high-impact events.