Comparison of thoracolumbar spine kinematics and injuries in reclined frontal impact sled tests between mid-size adult female and male PMHS.

Disparities in injury tolerance and kinematic response remain understudied despite field data highlighting sex-based differences in injury risk. Furthermore, the automotive industry anticipates occupants will prefer reclined seating in highly automated vehicles. This study aimed to compare thoracolumbar spine kinematics and injuries between mid-size female and male post-mortem human subjects (PMHS) in reclined frontal impacts. Seven adult PMHS (three female, four male) were tested in reclined (50°) 50 km/h frontal impacts. The PMHS were seated on a semi-rigid seat and restrained by a prototype three-point seat belt system designed to mitigate submarining. The 3-D motions of five vertebrae and the pelvis were measured by an optical motion tracking system. Pressure transducers were inserted into intervertebral discs at three locations along the lumbar spine to track timing of lumbar vertebra fractures. Due to variations in the geometry of the pelvis and soft tissue surrounding the pelvis compared to the male subjects, the female subjects could not be positioned in the seat the same as the males, and, as a result, the females and their belt anchors needed to be translated forward in the seat to maintain similar belt geometry relative to the males. The females exhibited similar pre-test spinal curvatures and kinematics to the males. An L1 fracture was observed in one of three female subjects and two of four male subjects, and timing of these fractures were both similar (61 ∼ 65 ms) and close to the time of peak downward seat force. Generally, the female and male subjects exhibited similar kinematic and injury responses in this reclined frontal impact sled test condition.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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