Kinematic response of the spine during simulated aircraft ejections.
BACKGROUND
Military aviators are susceptible to spinal injuries during high-speed ejection scenarios. These injuries commonly arise as a result of strains induced by extreme flexion or compression of the spinal column. This study characterizes the vertebral motion of two postmortem human surrogates (PMHS) during a simulated catapult phase of ejection on a horizontal decelerator sled.


METHODS
During testing, the PMHS were restrained supinely to a mock ejection seat and subjected to a horizontal deceleration profile directed along the local z-axis. Two midsized males (175.3 cm, 77.1 kg; 185.4 cm, 72.6 kg) were tested. High-rate motion capture equipment was used to measure the three-dimensional displacement of the head, vertebrae, and pelvis during the ejection event.


RESULTS
The two PMHS showed generally similar kinematic motion. Head injury criterion (HIC) results were well below injury threshold levels for both specimens. The specimens both showed compression of the spine, with a reduction in length of 23.9 mm and 45.7 mm. Post-test autopsies revealed fractures in the C5, T1, and L1 vertebrae.


CONCLUSIONS
This paper provides an analysis of spinal motion during an aircraft ejection.The injuries observed in the test subjects were consistent with those seen in epidemiological studies. Future studies should examine the effects of gender, muscle tensing, out-of-position (of head from neutral position) occupants, and external forces (e.g., windblast) on spinal kinematics during aircraft ejection.
Damon
Andrew M
AM
Center for Applied Biomechanics, Department of Orthopedic Surgery, University of Virginia, 1011 Linden Ave., Charlottesville, VA 22902, USA. amd3j@virginia.edu
Lessley
David J
DJ
Salzar
Robert S
RS
Bass
Cameron R
CR
Shen
Francis H
FH
Paskoff
Glenn R
GR
Shender
Barry S
BS
D000054:Acceleration / Q000009:adverse effects*; D000337:Aerospace Medicine; D000401:Aircraft; D001696:Biomechanical Phenomena; D002102:Cadaver; D003198:Computer Simulation; D006801:Humans; D008297:Male; D008875:Middle Aged; D008889:Military Personnel; D013124:Spinal Injuries / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D013131:Spine / Q000503:physiopathology*; D014481:United States