![]() ![]() Lateral bending may also be present to some degree in cases of compressive spinal injury documented in falls, diving into shallow water and sports including American football, rugby, ice hockey and gymnastics 23, 24. When the most serious rollover injuries occur (maximum Abbreviated Injury Scale 3+), the spine is the second most frequently injured body region following the thorax 22. Although a rare crash type constituting around 2.2% of crashes 20, more than 30% of fatalities occur in rollover crashes 21. lateral bending) despite the combination of compression and lateral bending being implicated as a common injury mechanism in rollover vehicle crashes 18, 19. These notably omit consideration of failure due to coronal plane loads (i.e. flexion/extension bending moment) is needed to fully describe the tolerance of the spine this is because the profile of failure loads and the injury outcome in axial compression are highly dependent on the mechanism of injury and the boundary conditions of the spine at impact 8, 11.Įxisting injury criteria of the cervical spine have primarily focused on load combinations of axial force and flexion-extension moments that are measured with ATDs. These studies helped define a compressive force limit for the cervical spine of 1.75–4.8 kN 17 but have also shown that incorporating forces and moments beyond compressive force alone (e.g. Our current understanding of cervical spine biomechanics in axial compression has been informed by impact tests using human cadaver spines or spine segments under various boundary conditions 7, 8, 9, 10, 11, 12, 13, 14, 15, 16. Injury criteria can then be used to design human surrogates, such as an anthropometric test device (ATD), and vehicle occupant protective systems or safety devices for falls and sports. With a defined injury mechanism, defining tolerance levels involves determining how much force or acceleration the body or a part of the body can withstand before injury occurs and must consider the rate at which the force or acceleration varies with time in the biological material 5, 6. To prevent injury to the cervical spine, it is necessary to understand typical mechanisms of injury as well as the tolerance of the spine to mechanical loading. The incidence and prevalence of spinal cord injury has not decreased for many decades 3, 4 despite improvements in road safety and vehicle crashworthiness providing reductions in mortality and injuries to other body regions. Road traffic crashes are the most common cause of spinal cord injury, followed by falls, violence and sports 2. The estimated lifetime cost per individual traumatic spinal cord injury can be up to $3 million and the economic burden of new cases in Canada is an estimated $2.67 billion per year 1. Traumatic cervical spine injuries can be catastrophic and carry considerable societal and economic consequences, particularly when the spinal cord is involved. These results provide the foundation for designing and evaluating strategies and devices for preventing severe spinal injuries. There was no relationship between axial force and lateral bending moment at injury which has been previously proposed as an injury criterion. The level of coronal plane eccentricity at failure appears to distinguish between the types of injuries sustained, with hard tissue structure injuries more common at low levels of eccentricity and soft tissue structure injuries more common at high levels of eccentricity. Larger coronal plane eccentricity at injury was associated with smaller resultant coronal plane force. Linear regression was used to define neck injury tolerance values based on a criterion incorporating coronal plane loads accounting for specimen sex, age, size and bone density. Injury was identified by high-speed video and graded by spine surgeons. Thirty-three human cadaveric functional spinal units were subjected to axial compression at three magnitudes of lateral eccentricity of the applied force. This study aimed to determine an injury criterion and accompanying tolerance values for cervical spine segments in axial compression applied with varying coronal plane eccentricity. There is currently no established injury criterion for the spine in compression with lateral load components despite this load combination commonly contributing to spinal injuries in rollover vehicle crashes, falls and sports. ![]()
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