Advances in Understanding of Experimental Concussion Mechanisms

Hodgson, V. R.; Thomas, L. M.; Gurdjian, E. S.; Fernando, O. U.; Greenberg, S. W.; Chason, Jacob L.

doi:10.4271/690796

Cited by 11 publications

(3 citation statements)

References 9 publications

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“…Mass movement of the brain, skull deformation and acceleration upon impact increased cranial pressure at time of impact and the transmission of impact to the brain has been linked to brain damage and concussion as reported by Hodgson et al. 17…”

Section: Discussionmentioning

confidence: 90%

“…The authors concluded the skull deformation from the impact possibly having important implications on injury produced with blunt force head impacts, noting that the skull geometry of Rhesus monkeys and humans differ significantly. Mass movement of the brain, skull deformation and acceleration upon impact increased cranial pressure at time of impact and the transmission of impact to the brain has been linked to brain damage and concussion as reported by Hodgson et al 17 Melvin and Evans 18 reported that upon impact, the forces produce local deformations of the skull at the impact site with stress waves travelling away from the impact site throughout the skull to the underlying structures -likened to ripples in water. The combination of forces transmitted to the skull and subsequent deformation creates energy distribution and displacement throughout the materials.…”

Section: Discussionmentioning

confidence: 95%

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Anatomical head model to measure impact force transfer through the head layers and their displacement

Falland-Cheung

Waddell

et al. 2018

Journal of Concussion

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When the human head is subjected to blunt force impact, there are several mechanical responses that may result from the forces involved, including absorption of impact forces through the various layers of the head. The purpose of this study was to develop an anatomical head model to measure force transfer through the various head layers and their displacement when subject to short-duration high-velocity impacts. An anatomical head model was constructed using previously validated simulant materials: epoxy resin (skull), polyvinyl siloxane (scalp), agar/glycerol/water (brain) and modified intravenous fluid for the cerebrospinal fluid. An array of accelerometers (4 mm Â 4 mm Â 1.45 mm) was incorporated into the various layers of the head to measure forces in x-(anterior/posterior), y-(left/right) and z-(up/down) axis. All sensors were connected to a signal conditioning board and USB powered data loggers. The head model was placed into a rigid metal stand with an optical sensor to trigger data capturing. A weight (750 g) was dropped from a height of 0.5 m (n¼ 20). Impact forces (z-axis) of 1107.05 N were recorded on top of the skin, with decreasing values through the different layers (bottom of skin 78.48 N, top of skull 319.82 N, bottom of skull 87.30 N, top and centre of brain 47.09 N and base of brain 78.41 N. Forces in the x-and y-axes were similar to those of the z-axis. With the base of the brain still receiving 78.41 N, this highlights the potential danger of repetitive impact forces to the head. Upon impact the layers of the head are displaced in the x-, y-and z-direction, with the highest values shown in the z-axis. In conclusion, this study identified the importance of considering short-duration high-intensity impacts to the head and their effect on underlying tissues.

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Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 95%

Anatomical head model to measure impact force transfer through the head layers and their displacement

Falland-Cheung

Waddell

et al. 2018

Journal of Concussion

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“…Localised deformation of brain tissue, and distortion of the brain stem, occur as a result of shear stresses attributable to pressure gradients. Subsequently, it has been concluded that coup and contrecoup brain injuries can both occur from intracranial pressure gradients [74,79,[85][86][87].…”

Section: Intracranial Pressurementioning

confidence: 99%

Towards concussion prevention in ice hockey: mechanical metamaterial liners and helmet assessment

Haid

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Ice hockey has one of the highest concussion rates in sport. During player-to-player collisions, the most common concussive scenario, helmets have been shown to offer limited protection. Helmet testing that is representative of the broad range of potential head impacts requires extensive specialist equipment, while certification standards are currently not assessing the impact scenario that most commonly causes concussions in ice hockey. Consequently, helmets protect well in the scenario they are certified and designed for – falls onto stiff surfaces – but provide limited protection during other commonly occurring impacts, especially impacts with more compliant bodies. Due to the wide range of injurious head impacts in ice hockey, it is challenging to develop a helmet that protects well in all scenarios. The aim of this programme of research was to develop a simplified test method, capable of replicating common ice hockey head impacts. Then, to investigate the capabilities of a mechanical metamaterial to enhance protection during collisions without compromising protection during more severe head impacts. A novel test method, utilising laboratory equipment that is available to most researchers with an interest in impact protection, to replicate head impacts in ice hockey was developed and validated. It has been shown that a free-fall drop test method, with interchangeable impact surface orientation and compliance, can be used to create impact events that are representative of a range of common ice hockey head impacts. This newly developed test method can produce kinematic responses within less than 10% of key metrics obtained by current best practice methods to replicate ice hockey collisions and may facilitate widespread and more thorough testing in academic research and modifications to current test standard procedures. A series of investigations were conducted to assess the potential of a mechanical metamaterial, comprising bi-beam structures, with an adaptive response to specific impact scenarios. Testing and modelling of individual bi-beams, unit cells, and cellular structures of bi-beams suggest a cellular structure, comprising bi-beams, can be developed by arranging unit cells relative to each other between two stiff sandwich plates. It has been shown that controlling the direction of buckling and the associated contact situations, can cause an abrupt switch in stiffness (~155 – 180%) in axial direction. Applied as a liner in an ice hockey helmet, this could achieve enhanced protection against an additional cause of injury – collisions – without compromising the performance in the scenario the helmets are currently designed for – falls. Dimensional scalability facilitates a wide range of possible designs and fields of application. This programme of research contributes to the body of knowledge of head impact testing and helmet technologies to better protect players. Findings could help in developing better helmets that protect players against a wider range of head impacts which in turn would reduce concussions and make participation safer.

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