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Whole-body vibration has been identified as a potential stressor to spinal cord injury (SCI) patients during pre-hospital transportation. However, the effect that such vibration has on the acutely injured spinal cord is largely unknown, particularly in the frequency domain of 5 Hz in which resonance of the spine occurs. The objective of the study was to investigate the consequences of resonance vibration on the injured spinal cord. Using our previously characterized porcine model of SCI, we subjected animals to resonance vibration (5.7±0.46 Hz) or no vibration for a period of 1.5 or 3.0 h. Locomotor function was assessed weekly and cerebrospinal fluid (CSF) samples were collected to assess different inflammatory and injury severity markers. Spinal cords were evaluated histologically to quantify preserved white and gray matter. No significant differences were found between groups for CSF levels of monocyte chemotactic protein-1, interleukin 6 (IL-6) and lL-8. Glial fibrillary acidic protein levels were lower in the resonance vibration group, compared with the non-vibrated control group. Spared white matter tissue was increased within the vibrated group at 7 d post-injury but this difference was not apparent at the 12-week time-point. No significant difference was observed in locomotor recovery following resonance vibration of the spine. Here, we demonstrate that exposure to resonance vibration for 1.5 or 3 h following SCI in our porcine model is not detrimental to the functional or histological outcomes. Our observation that a 3.0-h period of vibration at resonance frequency induces modest histological improvement at one week post-injury warrants further study.

Terrain parks and jumping features at ski resorts have become increasingly popular with skiers and snowboarders over the past decade. If a jumper were to land incorrectly, such as in an inverted posture where one lands on their head, the consequences can be devastating and can result in cervical spine fractures or dislocations and serious spinal cord injury. The objective of this study was to assess the potential for serious neck injury in head-first impacts onto snow surfaces with and without helmets. We conducted six paired head-first impact drop tests, with and without helmets on snow that varied from soft to hard. Drop tests were carried out with a head and neck assembly from a Hybrid III anthropomorphic test device using a custom designed drop carriage. The impact speed was 4.0 ± 0.1 m/s, representing an equivalent fall height of 0.82 m. The head was instrumented with three uniaxial accelerometers located at the center-of-gravity and a six-axis load cell was located at the upper neck. The results indicated that the helmets provided good head protection in the hard snow impacts, reducing head accelerations by as much as 48 %. Head accelerations were low in soft snow impacts both with and without a helmet. Overall, helmets were not an effective countermeasure to high neck loads, although a minor reduction was noted in the soft snow impacts. All tests resulted in neck loads that exceeded the injury assessment reference values for the neck. Notably in the hard snow impacts, the neck loads were more than double the injury assessment reference values for all tests. Because of the susceptibility of the neck to injury at the relatively low drop heights that we tested, efforts to prevent neck injuries should focus on education and training to avoid head-first impact. KEYWORDS: head injury, neck injury, head-first impact, helmet, anthropomorphic test device, snow impact Language: en