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The Influence of Neck Muscle Tonus and Posture on Brain Tissue Strain in Pedestrian Head Impacts
KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.ORCID iD: 0000-0001-7908-6270
KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.ORCID iD: 0000-0003-0125-0784
2014 (English)In: Stapp Car Crash Journal, ISSN 1532-8546, Vol. 58, ​63-101 p.Article in journal (Refereed) Published
Abstract [en]

Pedestrians are one of the least protected groups in urban traffic and frequently suffer fatal head injuries. An important boundary condition for the head is the cervical spine, and it has previously been demonstrated that neck muscle activation is important for head kinematics during inertial loading. It has also been shown in a recent numerical study that a tensed neck musculature also has some influence on head kinematics during a pedestrian impact situation. The aim of this study was to analyze the influence on head kinematics and injury metrics during the isolated time of head impact by comparing a pedestrian with relaxed neck and a pedestrian with increased tonus. The human body Finite Element model THUMS Version 1.4 was connected to head and neck models developed at KTH and used in pedestrian-to-vehicle impact simulations with a generalized hood, so that the head would impact a surface with an identical impact response in all simulations. In order to isolate the influence of muscle tonus, the model was activated shortly before head impact so the head would have the same initial position prior to impact among different tonus. A symmetric and asymmetric muscle activation scheme that used high level of activation was used in order to create two extremes to investigate. It was found that for the muscle tones used in this study, the influence on the strain in the brain was very minor, in general about 1-14% change. A relatively large increase was observed in a secondary peak in maximum strains in only one of the simulated cases.

Place, publisher, year, edition, pages
2014. Vol. 58, ​63-101 p.
Keyword [en]
Pedestrian accidents, muscle tonus, finite element method, brain tissue strain
National Category
Other Medical Engineering
Research subject
Applied Medical Technology
Identifiers
URN: urn:nbn:se:kth:diva-157681Scopus ID: 2-s2.0-84945411734OAI: oai:DiVA.org:kth-157681DiVA: diva2:771053
Note

QC 20150217

Available from: 2014-12-12 Created: 2014-12-12 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Understanding Boundary Conditions for Brain Injury Prediction: Finite Element Analysis of Vulnerable Road Users
Open this publication in new window or tab >>Understanding Boundary Conditions for Brain Injury Prediction: Finite Element Analysis of Vulnerable Road Users
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Vulnerable road users (VRUs) are overrepresented in the statistics on severe and deadly injuries in traffic accidents, most commonly involving the head. The finite element (FE) method presents the possibility to model complex interactions between the human body and vehicles in order to better understand the injury mechanisms. While the rapid development of computer capacity has allowed for increasingly detailed FE-models, there is always a benefit of reducing the studied problem. Due to its material properties, the brain is more sensitive to rotational motion than to purely linear, resulting in complex injury causation. When studying brain injuries caused by a direct impact to the head, simulations using an isolated head model significantly increases efficiency compared to using a complete human body model. Also evaluation of head protective systems uses isolated mechanical head representations. It is not, however, established the extent to which the boundary conditions of the head determine the outcome of brain injuries.

FE models of both the entire human body and the isolated head were used in this thesis to study the effect of the body, as well as active neck muscle tension, on brain injury outcome in VRU accidents. A pediatric neck model was also developed to enable the study of age-specific effects. A vehicle windscreen model was developed to evaluate the necessity of capturing the failure deformation during pedestrian head impacts.

It was shown that the influence of the neck and body on brain injury prediction is greater in longer duration impacts, such as pedestrian head-to-windscreen impacts with an average difference of 21%. In accidents with shorter duration impacts, such as head-to-ground bicycle accidents, the average influence was between 3-12%. The influence did not consistently increase or limit the severity, and was dependent on the degree of rotation induced by the impact, as well as the mode of deformation induced in the neck. It was also shown that the predicted brain injury severity is dependent on capturing the large deformations of fractured windscreen, with the greatest effect near the windscreen frame. The pediatric neck model showed a large effect of age-dependent anatomical changes on inertial head loading, making it a promising tool to study the age-dependent effects in VRU accidents.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. 83 p.
Series
TRITA-STH : report, ISSN 1653-3836 ; 2017:11
Keyword
Brain injuries; Vulnerable Road Users; windscreen impacts; Finite Element Analysis; pedestrian accidents; cycling accidents; pediatric neck
National Category
Other Medical Engineering
Research subject
Applied Medical Technology
Identifiers
urn:nbn:se:kth:diva-215643 (URN)978-91-7729-568-6 (ISBN)
Public defence
2017-11-06, T2, Hälsovägen 11C, Huddinge, 10:00 (English)
Opponent
Supervisors
Note

QC 20171013

Available from: 2017-10-13 Created: 2017-10-12 Last updated: 2017-10-16Bibliographically approved

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Strömbäck Alvarez, VictorKleiven, Svein

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