Validating a Device for Whiplash Motion Simulation in a Porcine Model

Whiplash injury is a common outcome following minor automobile collisions. One theorizedmechanism for whiplash injury is that the rapid head and neck motions induced by a collision caninjure nerve cells in the dorsal root ganglia through pressure gradients developed in the spinalcanal and surrounding tissues. This injury mechanism has previously been studied in humancadaver and porcine models. However, the whiplash motion simulation methods in the latterstudies lacked the control necessary to explore the independent effects of head rotation andretraction on the measured spinal pressures. This project aimed to address the limitations ofprevious porcine whiplash studies by developing and validating a new whiplash motion simulationdevice to enable further study of this injury mechanism. The new proposed device consists of twoservomotors which can be programmed to precisely actuate a headplate through mechanicallinkages. For the current study, an inert surrogate model was used for preliminary testing of thedevice using a whiplash motion profile from previous porcine studies. The time scale of the motionprofile was adjusted to incrementally increase severity. The positional accuracy and repeatabilityof the device was assessed through marker tracking of the headplate and logging of the motorencoder positions. Angular rates and linear accelerations of the plate were also measured. Testingdemonstrated the strengths of the proposed device in accurately and repeatably replicatingprogrammed motion profiles. Some design modifications can potentially enable simulatingwhiplash motion severities commensurate with previous porcine whiplash studies. With futuretesting using this device, our understanding of the pressure-induced whiplash injury mechanismcan be improved, which can inform effective treatments and preventative measures for whiplashinjury

Load-sharing and kinematics of the human cervical spine under multi-axial transverse shear loading: combined experimental and computational investigation

This preprint has not undergone peer review or any post-submission improvements or corrections. The Version of Record of this article is published in Journal of Biomechanical Engineering, and is available online at https://doi.org/10.1115/1.4050030The cervical spine experiences shear forces during everyday activities and injurious events yet there is a paucity of biomechanical data characterizing the cervical spine under shear loading. This study aimed to 1) characterise load transmission paths and kinematics of the subaxial cervical spine under shear loading, and 2) assess a contemporary finite element cervical spine model using this data. Subaxial functional spinal units (FSUs) were subjected to anterior, posterior and lateral shear forces (200 N) applied with and without superimposed axial compression preload (200 N) while monitoring spine kinematics. Load transmission paths were identified using strain gauges on the anterior vertebral body and lateral masses and a disc pressure sensor. Experimental conditions were simulated with cervical spine finite element model FSUs (GHBMC M50 version 5.0). The mean kinematics, vertebral body strains and disc pressures were compared to experimental results. The shear force-displacement response typically demonstrated a toe region followed by a linear response, with higher stiffness in the anterior shear direction relative to lateral and posterior shear. Compressive axial preload decreased posterior and lateral shear stiffness and increased anterior shear stiffness. Load transmission patterns and kinematics suggest the facet joints play a key role in limiting anterior shear while the disc governs motion in posterior shear. The main cervical spine shear responses and trends are faithfully predicted by the GHBMC finite element cervical spine model. These basic cervical spine biomechanics and the computational model can provide insight into mechanisms for facet dislocation in high severity impacts, and tissue distraction in low severity impacts