Biomedical Engineering Reference
In-Depth Information
All the incorporated ligaments were modeled as incompressible discrete axial connectors with
nonlinear load-deformation behavior, as exhibited by natural ligaments (Narayan, Srirangam, and
Frank 2001). The material properties of the intact healthy cervical spine are presented in Table 16.1.
During assembly of the cervical components, the interacting surfaces of the intervertebral discs
and the vertebral endplates were tied together to prevent sliding. The tips of the ligaments were
also tied to the corresponding anatomic insertion position on the bony vertebrae (Figure 16.2c).
A frictionless sliding contact property was applied to the inferior articular process and the concave
articular surface of the facet joint and of the uncovertebral joint.
The kinematic motions of the spine are quite complex when performing routine daily activities.
However, motions can be simplified into the three anatomic planes: flexion (bending anteriorly)
and extension (bending posteriorly), lateral bending, and axial torsion (Figure 16.2d). In the present
table 16.1
material Properties of Cervical Spine Components
Poisson's
ratio
Component
young's modulus (mPa)
description
Cortical bone
12,000
0.30
0.5 mm thickness
Cancellous bone
100
0.25
Endplate cartilage
1,200
0.30
0.5 mm thickness
Matrix of annulus fibrosus
3.4
0.45
Nucleus pulposus
1
0.49
43% volume of disc
Annulus fiber
450
0.45
19% volume of annulus
Ligament
Nonlinear tension only discrete axial connectors
C3-C5 (load-deflection relationship)
all
Pll
Sl & ISl
lF
Cl
d(mm)
F(n)
d(mm)
F(n)
d(mm)
F(n)
d(mm)
F(n)
d(mm)
F(n)
0
0
0
0
0
0
0
0
0
0
1
28
1
25
1
7
2
38
2
55
2
52
2
44
2
12.5
4
60
4
130
3
72
3
62
3
18
6
80
6
180
4
89
4
78
4
22.5
8
108
8
210
5
102
5
89
5
26
10
230
6
115
6
30
7
32.5
C5-C6 (load-deflection relationship)
all
Pll
Sl & ISl
Fl
Cl
d(mm)
F(n)
d(mm)
F(n)
d(mm)
F(n)
d(mm)
F(n)
d(mm)
F(n)
0
0
0
0
0
0
0
0
0
0
1
20
1
20
1
8
2
30
2
75
2
40
2
40
2
14
4
68
4
145
3
58
3
60
3
20
6
102
6
204
4
78
4
78
4
25
8
130
8
250
5
98
5
92
5
29
10
145
10
265
6
112
6
32.5
7
120
7
35
Note:
ALL, anterior longitudinal ligament; CL, capsular ligament; LF, flaval ligament; ISL, interspinous ligament; PLL,
posterior longitudinal ligament; D(mm), deflection in millimeters; and F(N), force in Newtons.
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