A Constitutive Model for the Annulus of Human Intervertebral Disc: Implications for Developing a Degeneration Model and Its Influence on Lumbar Spine Functioning

Table 4

Material properties and element types of the finite element model.

Component	Element type	Number of elements	Material constants	Notes
Bone	R3D3	73016		Rigid body
Nucleus	C3D8	10106	𝐶1=0.16 MPa; 𝐷=0.024 MPa−1; 𝑐𝐹,0=1.810^−4 meq/mm^3; 𝑘0=1.92410^−16 m^4/Ns; 𝑛𝑓,0=0.8; 𝑒=4.8	Porohyperelastic NeoHookean [44]
Annulus	C3D8	19421	see Table 2	Porohyperelastic Fibre reinforced material (𝛼=±30^∘) [17]
Ligaments	T3D2	180	see Table 1	Tension only truss
Posterior processes; contact	GAP	30