Table 1.

Material properties used in the finite element model.

Part	Material Property	References
Bone	E = 12 GPa, v = 0.3	[32]
Rib cage	E = 4.86 GPa, v = 0.3	[33]
Encapsulated soft tissue	E = 15 kPa, v = 0.49	[34]
Ligaments		[21,35,36]
Anterior longitudinal ligament	E = 11.9 kPa, v = 0.39
Capsular ligament	E = 7.7 kPa, v = 0.39
Flava ligament	E = 2.4 kPa, v = 0.39
Interspinous ligament	E = 3.4 kPa, v = 0.39
Intertransverse ligament	E = 10 kPa, v = 0.39
Posterior longitudinal ligament	E = 12.5 kPa, v = 0.39
Foam materials
Soft mattress
Medium mattress	Figure 1b, v = 0.01
Hard mattress
Pillow
Ground plate	Rigid part