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Sahandifar, P., Makoundou, C., Fahlstedt, M., Sangiorgi, C., Johansson, K., Wallqvist, V. & Kleiven, S. (2022). A rubberized impact absorbing pavement can reduce the head injury risk in vulnerable road users: a bicycle and a pedestrian accident case study. Traffic Injury Prevention
Open this publication in new window or tab >>A rubberized impact absorbing pavement can reduce the head injury risk in vulnerable road users: a bicycle and a pedestrian accident case study
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2022 (English)In: Traffic Injury Prevention, ISSN 1538-9588, E-ISSN 1538-957XArticle in journal (Refereed) Accepted
Abstract [en]

Objective: Vulnerable Road Users (VRU), including pedestrians and cyclists, are generally the leastprotected road users and are frequently missed in the planning process of preventive measures.Rubberized asphalt mixtures were originally developed as a possible environmentally friendly solutionto recycle the End-of-Life Tires while making the pavements more durable. The objective ofthe current study was to explore the effects of increasing the rubber content of the common rubberizedasphalt mixtures in reducing the head injuries risk for VRUs.Method: To achieve this purpose, four different sample series with 0, 14, 28, and 33 weight percentrubber in each were tested. A compressive test without permanent deformation and onewith failure were performed on each sample series. The mechanical behavior of each set wasmodeled using a MAT_SIMPLIFIED_RUBBER material model in LS-Dyna and validated against astandard Head Injury Criterion (HIC) drop test. Ultimately, previously low-speed accident reconstructedcases, a bicycle and a pedestrian one, were used to assess the effect of varying the rubbercontent on reducing the head injury risk.Results: In the bicycle accident case, the risk of skull fracture was reduced from 0.99 to 0.29 whencomparing the non-rubberized asphalt mixture with the 33% rubber mixture. In the same accidentcase, the risk of concussion, evaluated using the logistic regression method, was reduced from0.97 in the non-rubberized mixture to 0.81 in the 33% rubber mixture. The initial conditions, linearand rotational velocities, were lower for the pedestrian case compared to the bicycle case (thebicycle case was more severe compared to the pedestrian case), which led to lower strains in thepedestrian case. In the pedestrian accident case, the risk of skull fracture was reduced from 1.00in the non-rubberized mixture to 0.63 in the 33% rubber mixture, while the risk of concussion wasreduced from 0.64 to 0.07.Conclusion: The rubberized asphalt mixtures could reduce the head injury risk for the studiedcases when the rubber content in the asphalt mixture increases.

Keywords
Rubberized pavement; recycled rubber; head injury; bicycle accident; pedestrian accident; vulnerable road users
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-311602 (URN)10.1080/15389588.2022.2067990 (DOI)35604793 (PubMedID)2-s2.0-85130924758 (Scopus ID)
Funder
Vinnova, 2013-04465
Note

QC 20220504

This work was supported by “BVFF – Bana v€ag f€or framtiden” underGrant number 2016-02; Sweden’s innovation agency, Vinnova underGrant number: D.nr.: 2013-04465); the SAFERUP! Project through theEuropean Union’s Horizon 2020 Research and Innovation programMarie Skłodowska-Curie under Grant number 765057.

Available from: 2022-04-30 Created: 2022-04-30 Last updated: 2023-06-08Bibliographically approved
Lindgren, N., Halldin, P. & Fahlstedt, M. (2022). Influence of Headform on Assessments and Ratings of the Protective Performance of Bicycle Helmets. In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI: . Paper presented at 2022 International Research Council on the Biomechanics of Injury, IRCOBI 2022, porto, Portugal, 14-16 September 2022 (pp. 892-911). International Research Council on the Biomechanics of Injury
Open this publication in new window or tab >>Influence of Headform on Assessments and Ratings of the Protective Performance of Bicycle Helmets
2022 (English)In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2022, p. 892-911Conference paper, Published paper (Refereed)
Abstract [en]

Numerous helmet rating methods have been proposed to assess the safety and effectiveness of bicycle helmets. The methods usually involve a series of experimental impact tests using an Anthropomorphic Test Device (ATD) headform. There are several headforms available for the purpose and this study sought to assess how the choice of headform influences the safety assessment and ratings of bicycle helmets by following four proposed rating programs using three commonly used headforms. 19 head impact cases were evaluated computationally using the National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform, Hybrid III (HIII) headform, and standard EN960 headform. The results show that for most oblique impact cases, EN960 produced considerably lower Peak Angular Acceleration (PAA), Peak Angular Velocity (PAV) and head injury risk compared to HIII and NOCSAE. This implies that the safety performance of bicycle helmets could be rated higher when using uncoated metal headforms compared to rubber-coated ones. The different headforms' tendency to produce varying rotational motion in oblique impacts raises questions about which of the headforms are suitable for such impact tests. The results presented in this study emphasize the occasional contradictions in helmet ratings presented by helmet rating programs. 

Place, publisher, year, edition, pages
International Research Council on the Biomechanics of Injury, 2022
Keywords
Bicycle helmet, Head impact testing, Head injury risk, Headform, Oblique impacts, Bicycles, Safety devices, Safety engineering, Safety testing, Sporting goods, Sports, Anthropomorphic test devices, Head impact, Head injuries, Injury risk, Oblique impact, Protective performance, Impact testing
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-331251 (URN)2-s2.0-85139520263 (Scopus ID)
Conference
2022 International Research Council on the Biomechanics of Injury, IRCOBI 2022, porto, Portugal, 14-16 September 2022
Note

QC 20230706

Available from: 2023-07-06 Created: 2023-07-06 Last updated: 2023-07-06Bibliographically approved
Fahlstedt, M., Meng, S. & Kleiven, S. (2022). Influence of Strain post-processing on Brain Injury Prediction. Journal of Biomechanics, 132, Article ID 110940.
Open this publication in new window or tab >>Influence of Strain post-processing on Brain Injury Prediction
2022 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 132, article id 110940Article in journal (Refereed) Published
Abstract [en]

Finite element head models are a tool to better understand brain injury mechanisms. Many of the models use strain as output but with different percentile values such as 100th, 95th, 90th, and 50th percentiles. Some use the element value, whereas other use the nodal average value for the element. Little is known how strain post-processing is affecting the injury predictions and evaluation of different prevention systems. The objective of this study was to evaluate the influence of strain output on injury prediction and ranking.& nbsp;Two models with different mesh densities were evaluated (KTH Royal Institute of Technology head model and the Total Human Models for Safety (THUMS)). Pulses from reconstructions of American football impacts with and without a diagnosis of mild traumatic brain injury were applied to the models. The value for 100th, 99th, 95th, 90th, and 50th percentile for element and nodal averaged element strain was evaluated based on peak values, injury risk functions, injury predictability, correlation in ranking, and linear correlation.& nbsp;The injury risk functions were affected by the post-processing of the strain, especially the 100th percentile element value stood out. Meanwhile, the area under the curve (AUC) value was less affected, as well as the correlation in ranking (Kendall's tau 0.71-1.00) and the linear correlation (Pearson's r2 0.72-1.00). With the results presented in this study, it is important to stress that the same post-processed strain should be used for injury predictions as the one used to develop the risk function.

Place, publisher, year, edition, pages
Elsevier BV, 2022
Keywords
Finite element models, Brain injuries, Injury prediction, Strain
National Category
Vehicle Engineering Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-312187 (URN)10.1016/j.jbiomech.2021.110940 (DOI)000789615500005 ()35065410 (PubMedID)2-s2.0-85123012005 (Scopus ID)
Note

QC 20220518

Available from: 2022-05-18 Created: 2022-05-18 Last updated: 2022-06-25Bibliographically approved
Fahlstedt, M., Abayazid, F., Panzer, M. B., Trotta, A., Zhao, W., Ghajari, M., . . . Halldin, P. (2021). Ranking and Rating Bicycle Helmet Safety Performance in Oblique Impacts Using Eight Different Brain Injury Models. Annals of Biomedical Engineering
Open this publication in new window or tab >>Ranking and Rating Bicycle Helmet Safety Performance in Oblique Impacts Using Eight Different Brain Injury Models
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2021 (English)In: Annals of Biomedical Engineering, ISSN 0090-6964, E-ISSN 1573-9686Article in journal (Refereed) Published
Abstract [en]

Bicycle helmets are shown to offer protection against head injuries. Rating methods and test standards are used to evaluate different helmet designs and safety performance. Both strain-based injury criteria obtained from finite element brain injury models and metrics derived from global kinematic responses can be used to evaluate helmet safety performance. Little is known about how different injury models or injury metrics would rank and rate different helmets. The objective of this study was to determine how eight brain models and eight metrics based on global kinematics rank and rate a large number of bicycle helmets (n=17) subjected to oblique impacts. The results showed that the ranking and rating are influenced by the choice of model and metric. Kendall’s tau varied between 0.50 and 0.95 when the ranking was based on maximum principal strain from brain models. One specific helmet was rated as 2-star when using one brain model but as 4-star by another model. This could cause confusion for consumers rather than inform them of the relative safety performance of a helmet. Therefore, we suggest that the biomechanics community should create a norm or recommendation for future ranking and rating methods.

Place, publisher, year, edition, pages
Springer, 2021
Keywords
Bicycle helmet, Brain injury criteria, Concussion, Finite element models, Oblique impact tests, Test methods
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-291346 (URN)10.1007/s10439-020-02703-w (DOI)000609366100003 ()33475893 (PubMedID)2-s2.0-85099751874 (Scopus ID)
Note

QC 20210310

Available from: 2021-03-10 Created: 2021-03-10 Last updated: 2022-06-25Bibliographically approved
Möller, H., Creutzfeldt, J., Valeskog, K., Rystedt, H., Edelbring, S., Fahlstedt, M., . . . Abrandt Dahlgren, M. (2021). Technology-Enhanced Learning of Human Trauma Biomechanics in an Interprofessional Student Context. Teaching and learning in medicine, 1-10
Open this publication in new window or tab >>Technology-Enhanced Learning of Human Trauma Biomechanics in an Interprofessional Student Context
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2021 (English)In: Teaching and learning in medicine, ISSN 1040-1334, E-ISSN 1532-8015, p. 1-10Article in journal (Refereed) Published
Abstract [en]

Phenomenon: This study aimed to investigate how students can develop their understanding of trauma biomechanics by means of technology-enhanced learning—an interactive visualization tool developed to enhance understanding of the biomechanics underlying an injury via dynamic imaging sequences. Approach: Students were invited to explore the content as a learning resource during an interprofessional clinical placement on an orthopedic ward. Thirty volunteer medical, nursing, and physiotherapy/occupational therapy students participated in 10 interprofessional groups of three participants. They were video recorded while interacting with learning software that was divided into five sections: Work Up, General Information, Biomechanical Case Study, Biomechanical Risk Assessment, and Treatment. Investigators probed students’ learning experiences via four focus group discussions. A sociomaterial perspective was adopted, directing the analytical focus to how students’ made use of talk, gestures, bodies, and material objects to understand the visualized phenomena. Findings: When connecting the visualization to a patient case, certain features of the technology stood out as important for promoting engagement and understanding trauma mechanisms. Decreased tempo, showing the directions and dynamics of trauma biomechanics in slow-motion, and color coding of the strain on the affected structures were especially important for evoking the emotional responses. The visualization tool also supported students’ explorations of causal relationships between external forces and their biomedical effects. These features emphasize the sociomaterial relation between the design of the technology and the student activities. Insights: Dynamic visualization of biomechanical events has the potential to improve the understanding of injury mechanisms and specifically to identify anatomical structures at high risk of injury. Dynamic visualizations for educational purposes seem to promote possibilities for learners to contextualize visual representations relative to one’s own body. Educational methods and practice need explicit attention and development in order to use the full potential of the visualization technology for learning for the health care professions. 

Place, publisher, year, edition, pages
Informa UK Limited, 2021
Keywords
biomechanics, Embodied learning, interprofessional learning, trauma, visualization
National Category
Pedagogy Learning
Identifiers
urn:nbn:se:kth:diva-308510 (URN)10.1080/10401334.2021.1893735 (DOI)000635810500001 ()33792438 (PubMedID)2-s2.0-85103598151 (Scopus ID)
Note

QC 20220209

Available from: 2022-02-09 Created: 2022-02-09 Last updated: 2022-06-25Bibliographically approved
Zhou, Z., Li, X., Liu, Y., Fahlstedt, M., Georgiadis, M., Zhan, X., . . . Zeineh, M. (2021). Toward a Comprehensive Delineation of White Matter Tract-Related Deformation. Journal of Neurotrauma, 38(23), 3260-3278
Open this publication in new window or tab >>Toward a Comprehensive Delineation of White Matter Tract-Related Deformation
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2021 (English)In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 38, no 23, p. 3260-3278Article in journal (Refereed) Published
Abstract [en]

Finite element (FE) models of the human head are valuable instruments to explore the mechanobiological pathway from external loading, localized brain response, and resultant injury risks. The injury predictability of these models depends on the use of effective criteria as injury predictors. The FE-derived normal deformation along white matter (WM) fiber tracts (i.e., tract-oriented strain) recently has been suggested as an appropriate predictor for axonal injury. However, the tract-oriented strain only represents a partial depiction of the WM fiber tract deformation. A comprehensive delineation of tract-related deformation may improve the injury predictability of the FE head model by delivering new tract-related criteria as injury predictors. Thus, the present study performed a theoretical strain analysis to comprehensively characterize the WM fiber tract deformation by relating the strain tensor of the WM element to its embedded fiber tract. Three new tract-related strains with exact analytical solutions were proposed, measuring the normal deformation perpendicular to the fiber tracts (i.e., tract-perpendicular strain), and shear deformation along and perpendicular to the fiber tracts (i.e., axial-shear strain and lateral-shear strain, respectively). The injury predictability of these three newly proposed strain peaks along with the previously used tract-oriented strain peak and maximum principal strain (MPS) were evaluated by simulating 151 impacts with known outcome (concussion or non-concussion). The results preliminarily showed that four tract-related strain peaks exhibited superior performance than MPS in discriminating concussion and non-concussion cases. This study presents a comprehensive quantification of WM tract-related deformation and advocates the use of orientation-dependent strains as criteria for injury prediction, which may ultimately contribute to an advanced mechanobiological understanding and enhanced computational predictability of brain injury.

Place, publisher, year, edition, pages
Mary Ann Liebert Inc, 2021
Keywords
axonal injury, computational brain modeling, finite element analysis, injury criteria, tract-related deformation, Article, brain concussion, brain disease, computer model, controlled study, disease classification, fiber tract deformation, human, orientation, prediction, simulation, traumatic brain injury, white matter
National Category
Neurosciences
Identifiers
urn:nbn:se:kth:diva-310618 (URN)10.1089/neu.2021.0195 (DOI)000717775500001 ()34617451 (PubMedID)2-s2.0-85110370546 (Scopus ID)
Note

QC 20220406

Available from: 2022-04-06 Created: 2022-04-06 Last updated: 2022-09-23Bibliographically approved
Pipkorn, B., Alvarez, V., Fahlstedt, M. & Lundin, L. (2020). Head Injury Risks and Countermeasures for a Bicyclist Impacted by a Passenger Vehicle. In: Proceedings of International Research Council on the Biomechanics of Injury (IRCOBI) 2020: . Paper presented at 2020 IRCOBI Conference. , Article ID IRC-20-41.
Open this publication in new window or tab >>Head Injury Risks and Countermeasures for a Bicyclist Impacted by a Passenger Vehicle
2020 (English)In: Proceedings of International Research Council on the Biomechanics of Injury (IRCOBI) 2020, 2020, article id IRC-20-41Conference paper, Published paper (Refereed)
Abstract [en]

The potential injury reducing benefits by a bicyclist helmet and a vehicle mounted bicyclist protectionairbag (BPA) was evaluated by means of human body model simulations. The human body model SAFER HBM waspositioned on a bicycle and impacted by a passenger vehicle in 40 km/h. Three conditions were evaluated; withoutcountermeasure, with helmet and helmet together with bicyclist protection airbag (BPA). Head injury risk wasevaluated by means of predicted HIC15, BrIC and strain in the brain.The impact conditions caused different impact points on the vehicle, windscreen and A-pillar. Both the impactpoints showed highest HIC and peak brain tissue strain for the case with no countermeasures and lowest valueswhen including both the helmet and BPA. BrIC increased when including the BPA for the windshield impact wherethe head did not impact the BPA, but a reduction was observed when the impact location was at the A-pillar.Generally head injury risk was reduced for a bicyclist wearing a helmet when impacted by a passenger vehiclein 40km/h. Additional reductions was obtained for a vehicle with a BPA. Therefore, the conclusion from this studywas that helmet and BPA have the potential to protect the head in vehicle to bicyclist impacts.

National Category
Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-291347 (URN)
Conference
2020 IRCOBI Conference
Note

QC 20210323

Available from: 2021-03-10 Created: 2021-03-10 Last updated: 2022-06-25Bibliographically approved
Fahlstedt, M., Kleiven, S. & Li, X. (2019). Current Playground Surface Test Standards Underestimate Brain Injury Risk for Children. Journal of Biomechanics
Open this publication in new window or tab >>Current Playground Surface Test Standards Underestimate Brain Injury Risk for Children
2019 (English)In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380Article in journal (Refereed) Published
Abstract [en]

Playgrounds surface test standards have been introduced to reduce the number of fatal and severe injuries. However, these test standards have several simplifications to make it practical, robust and cost-effective, such as the head is represented with a hemisphere, only the linear kinematics is evaluated and the body is excluded. Little is known about how these simplifications may influence the test results. The objective of this study was to evaluate the effect of these simplifications on global head kinematics and head injury prediction for different age groups. The finite element human body model PIPER was used and scaled to seven different age groups from 1.5 up to 18 years old, and each model was impacted at three different playground surface stiffness and three head impact locations. All simulations were performed in pairs, including and excluding the body. Linear kinematics and skull bone stress showed small influence if excluding the body while head angular kinematics and brain tissue strain were underestimated by the same simplification. The predicted performance of the three different playground surface materials, in terms of head angular kinematics and brain tissue strain, was also altered when including the body. A body and biofidelic neck need to be included, together with suitable head angular kinematics based injury thresholds, in future physical or virtual playground surface test standards to better prevent brain injuries.

National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-250703 (URN)10.1016/j.jbiomech.2019.03.038 (DOI)000469156200001 ()31014544 (PubMedID)2-s2.0-85064461545 (Scopus ID)
Note

QC 20190625

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2022-10-24Bibliographically approved
Fahlstedt, M. & Halldin, P. (2019). The difference in ranking of bike helmets when using different finite element head models. In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI: . Paper presented at 2019 International Research Council on Biomechanics of Injury Conference, IRCOBI 2019, 11 September 2019 through 13 September 2019 (pp. 660-661). International Research Council on the Biomechanics of Injury
Open this publication in new window or tab >>The difference in ranking of bike helmets when using different finite element head models
2019 (English)In: Conference proceedings International Research Council on the Biomechanics of Injury, IRCOBI, International Research Council on the Biomechanics of Injury , 2019, p. 660-661Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
International Research Council on the Biomechanics of Injury, 2019
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-285431 (URN)2-s2.0-85090741109 (Scopus ID)
Conference
2019 International Research Council on Biomechanics of Injury Conference, IRCOBI 2019, 11 September 2019 through 13 September 2019
Note

QC 20201130

Available from: 2020-11-30 Created: 2020-11-30 Last updated: 2022-06-25Bibliographically approved
Robinson, Y., Lison Almkvist, V., Olerud, C., Halldin, P. & Fahlstedt, M. (2018). Finite Element Analysis of Long Posterior Transpedicular Instrumentation for Cervicothoracic Fractures Related to Ankylosing Spondylitis. Global Spine Journal
Open this publication in new window or tab >>Finite Element Analysis of Long Posterior Transpedicular Instrumentation for Cervicothoracic Fractures Related to Ankylosing Spondylitis
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2018 (English)In: Global Spine Journal, ISSN 2192-5682, E-ISSN 2192-5690Article in journal (Refereed) Published
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-226880 (URN)10.1177/2192568217745068 (DOI)000457230900005 ()30202710 (PubMedID)2-s2.0-85053528044 (Scopus ID)
Note

QC 20180515

Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2024-03-18Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-0980-4051

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