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Comparison of Kinematic Responses of the Head and Spine for Children and Adults in Low-Speed Frontal Sled Tests
Technical Paper
2009-22-0012
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English
Abstract
Previous research has suggested that the pediatric ATD spine,
developed from scaling the adult ATD spine, may not adequately
represent a child's spine and thus may lead to important
differences in the ATD head trajectory relative to a human. To gain
further insight into this issue, the objectives of this study were,
through non-injurious frontal sled tests on human volunteers, to 1)
quantify the kinematic responses of the restrained child's head
and spine and 2) compare pediatric kinematic responses to those of
the adult. Low-speed frontal sled tests were conducted using male
human volunteers (20 subjects: 6-14 years old, 10 subjects: 18-40
years old), in which the safety envelope was defined from an
amusement park bumper-car impact. Each subject was restrained by a
custom-fit lap and shoulder belt system and photo-reflective
targets were attached to a tight-fitting cap worn on the head or
adhered to the skin overlying skeletal landmarks on the head,
spine, shoulders, sternum, and legs. A 3-D near-infrared target
tracking system quantified the position of the following markers:
head top, external auditory meatus, nasion, opisthocranion, C4, T1,
T4, and T8. Trajectory data were normalized by subject seated
height and head and spine rotations were calculated. The
Generalized Estimating Equations method was used to determine the
effect of age and key anthropometric measures on marker
excursion.
For all markers, the normalized forward excursion significantly
decreased with age and all spinal markers moved upward due to a
combination of rigid body rotation and spinal flexion with lesser
upward movement with age. The majority of the spine flexion
occurred at the base of the neck not in the upper cervical spine
and the magnitude of flexion was greatest for the youngest
subjects. Additional flexion occurred in the thoracic spine as
well. Our findings indicate that the primary factor governing the
differences in normalized head and spinal trajectories between the
various age groups was decreasing head-to-neck girth ratio with
increasing age. Other factors, such as muscle response and cervical
vertebral structural properties, may also contribute to the
differences, but were not evaluated in this paper. These results
can serve as a data set for validating the responses of restrained
ATDs and computational human models to low severity frontal
collisions.
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Authors
- Kristy B. Arbogast - Children's Hospital of Philadelphia
- Sriram Balasubramanian - Children's Hospital of Philadelphia
- Thomas Seacrist - Children's Hospital of Philadelphia
- Matthew R. Maltese - Children's Hospital of Philadelphia
- J. Felipe Garcia-Espana - Children's Hospital of Philadelphia
- Terrence Hopely - Rowan University
- Eric Constans - Rowan University
- Francisco J. Lopez-Valdes - University of Virginia
- Richard W. Kent - University of Virginia
- Hiromasa Tanji - TK Holdings
- Kazuo Higuchi - TK Holdings