Table 2.

Material properties and element specifications for the annular fibres and the ligaments (T3D2 three-dimensional two-node truss elements)

Material	Element type	No. of elements (in cage model)	Elastic modulus (MPa)	Poisson ratio	Referencea, cross sectional area (mm2)
Annulus fibre layers	T3D2
Outermost		480 (339)	550	0.3	0.7
Second		480 (340)	495	0.3	0.63
Third		480 (338)	440	0.3	0.55
Fourth		480 (335)	420	0.3	0.49
Fifth		480 (317)	385	0.3	0.41
Innermost		480 (0)	360	0.3	0.30
Ligaments	T3D2
Lig. long. anterius		45 (0)	20	0.3	38
Lig. long. posterius		35	70	0.3	20
Lig. flava		13	50	0.3	60
Lig. intertransversia		12	50	0.3	10
Lig. interspinalia		6	28	0.3	35.5
Lig. supraspinalia		6	28	0.3	35.5
Lig. capsulae		20	20	0.3	40

^a Values have been adapted from Shirazi-Adl et al. [34] and Smit et al. [37] for annulus fibre layers and have been taken from Lu and Hutton [19] for ligaments