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Table 1 Type and corresponding number of elements used in different finite element models of the lumbosacral spine

From: Mild (not severe) disc degeneration is implicated in the progression of bilateral L5 spondylolysis to spondylolisthesis

  INTACT NOR LYTIC M-DEG LYTIC M-DEG-COL LYTIC S-COL LYTIC
Nodes 308,539 320,256 320,256 382,025 382,025
Brick element (4-noded tetrahedrons) 1,454,554 1,522,196 1,522,196 1,811,798 1,811,798
Facet articulation (Nonlinear point contact elements) 5 per joint 5 per joint 5 per joint 5 per joint 5 per joint
Bilateral L5 lytic defect (Zero gap elements) 0 25 per side 25 per side 25 per side 25 per side
Annulus fibres (cylindrical beam elements) L1-L2 (O) 312–321–293-266 (I) (O) 289–272–229-224 (I) (O) 289–272–229-224 (I) (O) 350–311–279-262 (I) (O) 350–311–279-262 (I)
L2-L3 (O) 362–385–347-287 (I) (O) 271–266–254-168 (I) (O) 271–266–254-168 (I) (O) 359–316–268-255 (I) (O) 359–316–268-255 (I)
L3-L4 (O) 330–298–232-240 (I) (O) 265–244–212-189 (I) (O) 265–244–212-189 (I) (O) 395–318–269-258 (I) (O) 395–318–269-258 (I)
L4-L5 (O) 308–331–303-237 (I) (O) 251–218–233-163 (I) (O) 251–218–233-163 (I) (O) 385–322–284-253 (I) (O) 385–322–284-253 (I)
L5-S1 (O) 243–258–236-219 (I) (O) 202–192–169-167 (I) (O) 202–192–169-167 (I) (O) 436–352–341-291 (I) (O) 436–352–341-291 (I)
Ligaments per level (cylindrical beam elements) ALL 14 14 14 14 14
PLL 6 6 6 6 6
TL 16 16 16 16 16
LF 18 18 18 18 18
ISL 9 9 9 9 9
SSL 4 4 4 4 4
CL 24 per joint 24 per joint 24 per joint 24 per joint 24 per joint
ILL 20 20 20 20 20
LSL 22 22 22 22 22
  1. The concentric rings of annulus fibres were modelled using nonlinear beam elements
  2. (O) Layer1 (outermost)-Layer2-Layer3-Layer4 (innermost) (I); ALL Anterior Longitudinal Ligament, PLL Posterior Longitudinal Ligament, TL Transverse Ligament, LF Ligamentum Flavum, ISL Interspinous Ligament, SSL Supraspinous Ligament, CL Capsular Ligament, ILL Iliolumbar Ligament, LSL Lumbosacral Ligament