and Anita Vasavada1, 2
1School of Mechanical and
Materials Engineering; 2 Program in Bioengineering;
Washington State University, Pullman, WA, USA
Computational models have many
advantages in biomechanical analysis. Specifically, we are
interested in the role of neck muscles in whiplash injury. Studies
have shown that women are more likely to experience whiplash injury
than men. A female neck musculoskeletal model is essential for
analyzing the gender difference in whiplash, especially the
influence of size, geometry and biomechanical properties. A male
neck musculoskeletal model  has been developed in our lab, but
currently a female neck model does not exist. The goal of this study
is to develop a biomechanical model of the female head and neck
system in SIMM (Software for Interactive Musculoskeletal Modeling;
Motion Analysis, Santa Rosa, CA) based upon female anatomy from the
National Library of Medicine’s Visible Human Project (VHP).
The biomechanical neck model of the
musculoskeletal system in SIMM consists of the following components:
skeletal anatomy, joint kinematics, muscle anatomy and
Computed Tomographic (CT) images of the
Visible Human Female (59 yrs old, 1.65 m tall) were obtained from
the National Library of Medicine website. Image analysis software
(3D-doctor, Able Software, Lexington, MA) was used to segment bone
geometry and visualize the 3D models of the skull and each cervical
vertebra. (Fig. 1, Fig. 2)
The vertebrae from the Visible Human
Female were scanned in the supine posture (lying on the back), which
is most likely different from the upright neutral posture. Thus the
relative orientations of vertebrae needed to be adjusted to
correspond to the upright neutral posture.
between vertebrae were obtained from Harrison, et. al ,
and normalized relative displacement between two vertebrae were
obtained from Frobin, et. al  to adjust the head and
vertebrae to their upright neutral posture in the sagittal plane
(Fig. 4). The data used for the model in upright neutral posture are
all measured from female subjects.
From the vertebral
data we have , we can know the intervertebral angle
and the relationship among x, y, l, displ and disc height (Hdisc,
these equations for x, y and l, which define the
upright neutral posture.
Other kinematic data needed are:
instantaneous axes of rotation between vertebrae, total range of
motion and relative intervertebral motion. Unfortunately, data from
female subjects only are not available for all parameters; in some
cases mixed male and female data were used.
anatomy and Force-generating parameters
The origin and insertion of each neck
muscle were defined according to the same anatomical landmarks as in
the male model, and straight lines were used to represent muscle
paths initially. Currently, muscle force-generating parameters
(fiber lengths and cross sectional areas) are not available for
developed the biomechanical model of female head and neck system initially (Fig.
5). Future model development involves using Magnetic Resonance Imaging (MRI) to
obtain female neck muscle geometry (volume and path), which allows calculation
of muscle force- and moment-generating properties; incorporating curved muscle
paths using MRI data; and performing dynamic analyses to address gender
differences in neck injury.
1. Vasavada, AN, et al. Spine.
2. Harrison, D D, et al. Spine.
21(6): 667-675, 1996
3. Frobin, W, et al. Clinical
Bioengineering Research Center & Whitaker Foundation
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