Table 1.

Material properties used in the finite element models.

		Elastic modulus (MPa)	Poisson’s ratio	Reference
	Cortical bone	12,000	0.3	Cowin (1991)
	Trabecular bone	200	0.315	Lu et al. (1996)
	Posterior elements	3500	0.25	Cowin (1991)
	Ligaments	Non-linear	–	Galbusera et al. (2011)
	Annulus: fibers	25	0.3	Galbusera et al. (2011)
Normal disks	Annulus: ground substance	4.2	0.45	Pitzen et al. (2001)
	Nucleus pulposus	1	0.499	Pitzen et al. (2001)
	Annulus: fibers	12.5	0.3	–
Unstable disk	Annulus: ground substance	2.1	0.45	–
	Nucleus pulposus	1	0.499	–

“Unstable disk” summarizes the material properties used in the test case at the level of the spondylolisthesis in the models C–S and P–S.