Numerical analysis of the mechanical response of intervertebral disc considering collagen fibres conformation

Soft connective tissues are naturally optimised composite materials with directionally dependent mechanical properties since they are composed also by fibres rationally distributed in an amorphous ground matrix. A hyperelastic fibre-reinforced non-homogeneous constitutive model has then been adopted for anulus fibrosus in the disc. The formulation adopted allows for an appropriate description of disc tissues and distinguishes the different contribution of ground material and fibres. Several analyses have been made to take into account different values of volume content, distribution and inclination of fibres in the range of experimental data at disposal from literature. The performed investigation evidences the specific contribution of collagen fibres into the mechanical response of human intervertebral segment and confirms the present approach as an accurate tool for fibre-reinforced soft tissues.