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Numerical Accident Reconstructions: A Biomechanical Tool to Understand and Prevent Head Injuries
KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.ORCID iD: 0000-0002-0980-4051
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Traumatic brain injuries (TBIs) are a major health and socioeconomic problem throughout the world, with an estimated 10 million deaths and instances of hospitalization annually. Numerical methods such as finite element (FE) methods can be used to study head injuries and optimize the protection, which can lead to a decrease in the number of injuries. The FE head models were initially evaluated for biofidelity by comparing with donated corpses experiments. However, there are some limitations in experiments of corpses, including material degradation after death. One feasible alternative to evaluating head models with living human tissue is to use reconstruction of real accidents. However, the process of accident reconstruction entails some uncertainties since it is not a controlled experiment. Therefore, a deeper understanding of the accident reconstruction process is needed in order to be able to improve the FE human models. Thus, the aim of this thesis was to evaluate and further develop more advanced strategies for accident reconstructions involving head injuries.

A FE head model was used to study head injuries in accidents. Existing bicycle accident data was used, as were hypothetical accident situations for cyclists and pedestrians. A FE bicycle helmet model having different designs was developed to study the protective effect.

An objective method was developed based on the Overlap Index (OI) and Location Index (LI) to facilitate the comparison of FE model responses with injuries visible in medical images. Three bicycle accident reconstructions were performed and the proposed method evaluated. The method showed to have potential to be an objective method to compare FE model response with medical images and could be a step towards improving the evaluation of results from injury reconstructions.

The simulations demonstrated the protective effect of a bicycle helmet. A decrease was seen in the injurious effect on both the brain tissue and the skull. However, the results also showed that the brain tissue strain could be further decreased by modifying the helmet design.

Two different numerical pedestrian models were compared to evaluate whether the more time-efficient rigid body model could be used, instead of a FE pedestrian model, to roughly determine the initial conditions as an accident reconstruction involves some uncertainties. The difference, in terms of the head impact location, rotation and velocity, attributable to the two models was in the same range as differences due to uncertainties in some of the initial parameters, such as vehicle impact velocity.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , xvi, 88, XIV p.
Series
TRITA-STH : report, ISSN 1653-3836 ; 2015:4
Keyword [en]
Head injuries; Accident Reconstruction; Finite element analysis; Injury prevention; Helmet; Cyclist; Pedestrian; Epidemiology
National Category
Other Medical Sciences
Research subject
Applied Medical Technology
Identifiers
URN: urn:nbn:se:kth:diva-164091ISBN: 978-91-7595-512-4 (print)OAI: oai:DiVA.org:kth-164091DiVA: diva2:804818
Public defence
2015-05-08, 3-221, Alfred Nobels Allé 10, Huddinge, 09:00 (English)
Opponent
Supervisors
Note

QC 20150414

Available from: 2015-04-14 Created: 2015-04-13 Last updated: 2015-04-14Bibliographically approved
List of papers
1. A National Survey of Traumatic Brain Injuries Admitted to Hospital in Sweden from 1987 to 2010
Open this publication in new window or tab >>A National Survey of Traumatic Brain Injuries Admitted to Hospital in Sweden from 1987 to 2010
Show others...
2015 (English)In: Neuroepidemiology, ISSN 0251-5350, E-ISSN 1423-0208Article in journal (Refereed) Accepted
National Category
Other Medical Sciences
Research subject
Medical Technology
Identifiers
urn:nbn:se:kth:diva-164082 (URN)
Funder
VINNOVA, IHF 2013-05118
Note

QP 201504

Available from: 2015-04-13 Created: 2015-04-13 Last updated: 2017-12-04Bibliographically approved
2. Correlation between Injury Pattern and Finite Element Analysis in Biomechanical Reconstructions of Traumatic Brain Injuries
Open this publication in new window or tab >>Correlation between Injury Pattern and Finite Element Analysis in Biomechanical Reconstructions of Traumatic Brain Injuries
Show others...
2015 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 48, no 7Article in journal (Refereed) Published
Abstract [en]

At present, Finite Element (FE) analyses are often used as a tool to better understand the mechanisms of head injury. Previously, these models have been compared to cadaver experiments, with the next step under development being accident reconstructions. Thus far, the main focus has been on deriving an injury threshold and little effort has been put into correlating the documented injury location with the response displayed by the FE model. Therefore, the purpose of this study was to introduce a novel image correlation method that compares the response of the FE model with medical images.

The injuries shown on the medical images were compared to the strain pattern in the FE model and evaluated by two indices; the Overlap Index (OI) and the Location Index (LI). As the name suggests, OI measures the area which indicates both injury in the medical images and high strain values in the FE images. LI evaluates the difference in center of mass in the medical and FE images. A perfect match would give an OI and LI equal to 1.

This method was applied to three bicycle accident reconstructions. The reconstructions gave an average OI between 0.01 and 0.19 for the three cases and between 0.39 and 0.88 for LI. Performing injury reconstructions are a challenge as the information from the accidents often is uncertain. The suggested method evaluates the response in an objective way which can be used in future injury reconstruction studies.

National Category
Other Medical Sciences
Research subject
Applied Medical Technology
Identifiers
urn:nbn:se:kth:diva-164090 (URN)10.1016/j.jbiomech.2015.02.057 (DOI)000353751200014 ()2-s2.0-84925426031 (Scopus ID)
Note

QC 20150521

Available from: 2015-04-13 Created: 2015-04-13 Last updated: 2017-12-04Bibliographically approved
3. The Protective Effect of Bicycle Helmets
Open this publication in new window or tab >>The Protective Effect of Bicycle Helmets
(English)Manuscript (preprint) (Other academic)
National Category
Other Medical Sciences
Research subject
Applied Medical Technology
Identifiers
urn:nbn:se:kth:diva-164088 (URN)
Note

QS 2015

Available from: 2015-04-13 Created: 2015-04-13 Last updated: 2015-04-14Bibliographically approved
4. Importance of the Bicycle Helmet Design and Material for the Outcome in Bicycle Accidents
Open this publication in new window or tab >>Importance of the Bicycle Helmet Design and Material for the Outcome in Bicycle Accidents
2014 (English)In: Proceedings, International Cycling Safety Conference 2014, Chalmers , 2014, 1-14 p.Conference paper, Published paper (Refereed)
Abstract [en]

In Sweden the most common traffic group that needs to be hospitalized due to injury is cyclists where head injuries are the most common severe injuries. According to current standards, the performance of a helmet is only tested against radial impact which is not commonly seen in real accidents. Some studies about helmet design have been published but those helmets have been tested for only a few loading conditions. Therefore, the purpose of this study was to use finite element models to evaluate the effect of the helmet’s design on the head in some more loading conditions.

A detailed head model was used to evaluate three different helmet designs as well as non-helmet situations. The first helmet (Baseline Helmet) was an ordinary helmet available on the market. The two other helmet designs were a modification of the Baseline helmet with either a lower density of the EPS liner (Helmet 1) or a sliding layer between the scalp and the EPS liner (Helmet 2). Four different impact locations combined with four different impact directions were tested.

The study showed that using a helmet can reduce the peak linear acceleration (85%), peak angular acceleration (87%), peak angular velocity (77%) and peak strain in the brain tissue (77%). The reduction of the strain level was dependent on the loading conditions. Moreover, in thirteen of the sixteen loading conditions Helmet 2 gave lowest peak strain.

The alteration of the helmet design showed that more can be done to improve the protective effect of the helmet. This study highlighted the need of a modification of current helmet standard test which can lead to helmets with even better protective properties as well as some challenges in implementing new test standards.

Place, publisher, year, edition, pages
Chalmers, 2014
Keyword
Bicycle, helmet design, head injuries, finite element analysis
National Category
Civil Engineering
Identifiers
urn:nbn:se:kth:diva-158020 (URN)
Conference
International Cycling Safety Conference, November 18-19, 2014, Gothenburg, Sweden
Note

QC 20150123

Available from: 2014-12-19 Created: 2014-12-19 Last updated: 2015-04-14Bibliographically approved
5. Comparison of MADYMO and Finite Element Human Body Models in Pedestrian Accidents with the Focus on Head Kinematics
Open this publication in new window or tab >>Comparison of MADYMO and Finite Element Human Body Models in Pedestrian Accidents with the Focus on Head Kinematics
(English)Manuscript (preprint) (Other academic)
National Category
Other Medical Sciences
Research subject
Applied Medical Technology
Identifiers
urn:nbn:se:kth:diva-164086 (URN)
Note

QS 2015

Available from: 2015-04-13 Created: 2015-04-13 Last updated: 2015-04-14Bibliographically approved

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