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A Test Bed to Examine Helmet Fit and Retention and Biomechanical Measures of Head and Neck Injury in Simulated Impact
Published on: September 21, 2017
Dynamic biomechanics of the human head in lateral impacts
Jiangyue Zhang1, Narayan Yoganandan, Frank A Pintar
1Department of Neurosurgery, Medical College of Wisconsin, VA Medical Center, Milwaukee, WI, USA.
Summary
Lateral head impacts cause higher head accelerations and injury metrics than frontal impacts. Stiffer padding increases head acceleration, and severe brain injury can occur without skull fracture in lateral impacts.
Area of Science:
- Biomechanics
- Orthopedic Surgery
- Neurology
Background:
- Lateral head impacts are a significant concern in automotive safety.
- Understanding the biomechanics of lateral head impacts is crucial for developing effective protection strategies.
- Existing injury criteria are primarily based on frontal impact data, necessitating research into lateral impact responses.
Purpose of the Study:
- To investigate the biomechanical responses of the human head under lateral impact.
- To analyze the influence of padding properties on head kinematics and injury metrics.
- To compare lateral impact injury thresholds with established frontal impact thresholds.
Main Methods:
- Free drop tests were performed on human head specimens (PMHS) with simulated intracranial substance.
- Impact velocities ranged from 2.44 to 7.70 m/s using different padding materials (40D, 90D flat, 90D cylinder).
- Tri-axial accelerometers and a pyramid nine accelerometer package (pNAP) were used to measure accelerations, which were then transformed to the head's center of gravity (CG).
Main Results:
- A significant "hoop effect" was observed due to skull deformation.
- Stiffer padding materials led to higher head accelerations.
- Head Injury Criterion (HIC) values at skull fracture were 2-3 times higher than the frontal impact threshold (HIC=1000).
- High rotational head accelerations (up to 42.1 krad/s²) were recorded before skull fracture.
Conclusions:
- Lateral head impacts produce distinct biomechanical responses compared to frontal impacts.
- Skull fracture in lateral impacts is associated with significantly higher injury metrics.
- Severe brain injury may occur in lateral impacts even without accompanying skull fracture, highlighting the need for specific injury criteria.
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