This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Kinematics of Human Cadaver Cervical Spine During Low Speed Rear-End Impacts
Technical Paper
2000-01-SC13
Annotation ability available
Sector:
Language:
English
Abstract
The purposes of this study were to measure the relative linear
and angular displacements of each pair of adjacent cervical
vertebrae and to compute changes in distance between two adjacent
facet joint landmarks during low posterior- anterior (+Gx)
acceleration without significant hyperextension of the head. A
total of twenty-six low speed rear-end impacts were conducted using
six postmortem human specimens. Each cadaver was instrumented with
two to three neck targets embedded in each cervical vertebra and
nine accelerometers on the head. Sequential x-ray images were
collected and analyzed. Two seatback orientations were studied.
In the global coordinate system, the head, the cervical
vertebrae, and the first or second thoracic vertebra (T1 or T2)
were in extension during rear-end impacts. The head showed less
extension in comparison with the cervical spine. Relative motion
for each cervical motion segment went from flexion at the upper
cervical levels to extension at the lower cervical levels, with a
transition region at the mid-cervical levels. This rotational
pattern formed an "S" shape in the cervical spine during
the initial phase of low-speed rear impacts.
A pair of facet joint landmarks on each cervical motion segment
was used to measure the distance across the joint space. Uni-axial
facet capsular strains were calculated by dividing changes in this
distance over the original distance in seven tests using three
specimens. In 20-degree seatback tests, the average strain was
32±11% for the C2/C3 facet joint (17%-43% range), and 59±26%
for the C3/C4 facet joint (41%-97% range). The C4/C5 and C5/C6
facet joints exhibited peak tensile or compressive strains in
different specimens. In 0- degree seatback tests, the average
strain was 28±11% for the C2/C3 facet joint (21%-41% range),
30±9% for the C3/C4 facet joint (21%-39% range), 22±4% for the
C4/C5 facet joint (19%-25% range), and 60±13% for the C5/C6 facet
joint (51%-69% range).
In 20-degree seatback tests, there was less initial cervical
lordosis, more upward ramping of the thoracic spine, and more
relative rotation of each cervical motion segment in comparison
with the 0-degree seatback tests. Relative to T1, the head went
from flexion to extension for 20-degree seatback tests while stayed
in extension for 0-degree seatback tests.