Thoracic Responses and Injuries of Male Post-Mortem Human Subjects in a Homogeneous Rear-Facing Seat During...

Area of Science:

• Biomechanics
• Occupant Safety

Background:

• High-speed rear-facing frontal impacts (HSRFFI) have caused rib fractures in post-mortem human subjects (PMHS).
• Seatback structure and properties are potential contributors to thoracic injuries.

Purpose of the Study:

• To evaluate if a homogeneous rear-facing seat with a foam-covered back mitigates thoracic injury risk during HSRFFI.
• To analyze the relationship between seat design, occupant kinematics, and rib fracture outcomes.

Main Methods:

• Three male PMHS underwent HSRFFI using a novel seat design with instrumented spine, chestbands, and rib strain gauges.
• Whole-body kinematics were captured using motion systems.
• Thoracic deformation and rib strain were analyzed in relation to impact forces.

Main Results:

• One PMHS experienced no rib fractures, while two sustained multiple fractures (13 and 30).
• Anterior-posterior chest compression did not consistently correlate with fracture occurrence.
• Inferior-superior thoracic deformation varied significantly, with higher deformation correlating with more severe outcomes.

Conclusions:

• The tested seat design showed variable effectiveness in preventing rib fractures during HSRFFI.
• Inferior-superior thoracic deformation, not just A-P compression, is critical for understanding rib fracture mechanisms.
• Findings inform the development of protective countermeasures and validation of human body models for rear-facing seating.