ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

complexity of the vertebrae and skull. The ANSYS 8.0 (ANSYS, Inc. Pennsylvania,
USA) for the three-dimensional solid volume and mesh reconstruction using bottom-up
approach.
The geometry of bony structures was obtained from the dry embalmed specimens and
the geometrical data of the associate soft tissues was obtained from literature [19-24] in
the development of the FE modeling. The completed neck model was also configured
to contain a lordosis of about 37 o , which is consistent with the neck posture of a seated
50th percentile male. Figure 1 shows the final C0-T1 FE model consisting of 27,712
elements and 31,749 nodes.
Fig.1 FE model C0-T1 complex (lateral and posterior views)
The muscle properties were represented by basic Hill-type muscle model consisting of a
contractile element and a parallel elastic element to provide the active and passive
muscle force, respectively. The active muscle force was calculated by the following
dimensionless form as:
Factive = a(
t)
∗ Fmax
∗ fTL
( L)
∗ fTV
( V )
where a ( t)
, fTL ( L)
and ( V )
f TV are the functions describing the muscle active level-
time, tension-length and tension-velocity relationships, respectively, from previous
studies on muscle active state modeling [25,26] and shown in Figure 2. F max is the
muscle peak isometric force and was calculated by the initial muscle cross section area
and a peak muscle stress of 50 Ncm -2 [25]. The passive muscle force F passive was
determined directly from the current length of the muscle using an exponential
relationship [26].
To investigate the responses of the head-neck complex during motor vehicle collision at
different impact directions, the acceleration onset vectors (direction) experienced at T1
were assumed to be in the same as impact collision directions. The oblique side impact
directions for front-side and rear-side impacts were set at –45 o and –135 o respectively.
For each simulation, horizontal acceleration of a half-sine-wave pulse with peak value
of 5G and duration of 100ms, which was adapted by Panjabi et al. [27] was applied on
the inferior surface of T1 vertebral body. In the whole process, the T1 inferior surface
was constrained to move only in the same direction as the impact direction in a
transverse plane. The global head neck (C0-C7), spinal motion segments intervertebral
rotations, and peak strain in various ligaments under these conditions were further
investigated for possible injury analysis.