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Fracture-Dislocation of the Thoracic Spine in Extension by Upright Seats in Severe Rear Crashes
Technical Paper
2011-01-0274
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
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Language:
English
Abstract
Purpose: This study presents cases of fracture-dislocation of
the thoracic spine in extension during severe rear impacts. The
mechanism of injury was investigated.
Methods: Four crashes were investigated where a
lap-shoulder-belted, front-seat occupant experienced
fracture-dislocation of the thoracic spine and paraplegia in a
severe rear impact. Police, investigator and medical records were
reviewed, the vehicle was inspected and the seat detrimmed. Vehicle
dynamics, occupant kinematics and injury mechanisms were determined
in this case study.
Results: Each case involved a lap-shoulder-belted occupant in a
high retention seat with ≻1,700 Nm moment or ≻5.5 kN strength for
rearward loading. The crashes were offset rear impacts with 40-56
km/h delta V involving under-ride or override by the impacting
vehicle and yaw of the struck vehicle. In each case, the
occupant's pelvis was restrained on the seat by the open
perimeter frame of the seatback and lap belt. The rear loading
caused the head, neck and upper body to displace off the side or
top of the seatback. The seatback frame acted like a fulcrum as the
unsupported head and upper body was accelerated forward causing
extension of the spine around the seatback frame as the head and
shoulders moved rearward of the frame. In each case, there was
fracture-dislocation of the thoracic spine in extension with spinal
cord injury resulting in paraplegia. Two occupants were overweight
and two were obese, which increased inertial loads on the
spine.
Conclusions: High retention seats have improved safety of
occupants in rear crashes, but there are situations where the upper
body becomes unsupported in a severe rear crash. This can lead to
extension loads on the spine causing fracture-dislocation, spinal
cord injury and paraplegia. Injury is a result of the strong seat
frame remaining upright, the lap belt holding the pelvis on the
seat and the upper body moving off the seatback concentrating load
on the thoracic spine. The seatback frame acts like a fulcrum
resulting in fracture-dislocation of the spine in extension.
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Citation
Viano, D., "Fracture-Dislocation of the Thoracic Spine in Extension by Upright Seats in Severe Rear Crashes," SAE Technical Paper 2011-01-0274, 2011, https://doi.org/10.4271/2011-01-0274.Also In
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