Head Response and Cervical Spine Injuries in an Oblique Lateral Helmeted Head Impact

Purpose: Oblique lateral head impacts are common in motorcycle accidents and roll-over crashes. However, the neck injury mechanisms following this impact have not been thoroughly described. This work aimed to characterize the head kinematics and cervical spine injuries from oblique lateral helmeted head impacts. Methods: Five post-mortem human surrogates (3 females) were hit laterally on the head with a 37 kg impactor with an oblique plane generating a compressive load. The impact velocities were 4 m/s (3 surrogates) and 5.1 m/s (2 surrogates). The surrogates were equipped with accelerometers on the helmets, in the mouth and at the sternum. Stereography was used to follow the 3D displacements of markers on the helmet. CT-scans and dissection were performed after the impact to assess injuries. Results: The most frequent injuries were posterior ligament ruptures (2 occurrences) and vertebral lamina fractures (2 occurrences). The head maximal accelerations were between 13 and 51 g, and the peak impact forces ranged from 1800 to 5600 N. The head maximal lateral bending was around 30 degrees (4 m/s) or 50 degrees (5.1 m/s). Conclusion: While the measured lateral rotations were under the physiological threshold, they were sufficient to cause injuries at the tested impact energy level. This suggests that the dynamic aspect of the impact and the combination of compression and lateral bending delivered by the oblique impactor are essential in the injury mechanism. This novel data will be determinant in understanding cervical spine injuries and improving the behavior of human body models.