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Meng, S., Cernicchi, A., Kleiven, S. & Halldin, P. (2020). High-speed helmeted head impacts in motorcycling: A computational study. Accident Analysis and Prevention, 134, Article ID 105297.
Open this publication in new window or tab >>High-speed helmeted head impacts in motorcycling: A computational study
2020 (English)In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057, Vol. 134, article id 105297Article in journal (Refereed) Published
Abstract [en]

The motorcyclist is exposed to the risk of falling and impacting ground head-first at a wide range of travelling speeds - from a speed limit of less than 50 km/h on the urban road to the race circuit where speed can reach well above 200 km/h. However, motorcycle helmets today are tested at a single and much lower impact speed, i.e. 30 km/h. There is a knowledge gap in understanding the dynamics and head impact responses at high travelling speeds due to the limitation of existing laboratory rigs. This study used a finite element head model coupled with a motorcycle helmet model to simulate head-first falls at travelling speed (or tangential velocity at impact) from 0 to 216 km/h. The effect of different falling heights (1.6 m and 0.25 m) and coefficient of frictions (0.20 and 0.45) between the helmet outer shell and ground were also examined. The simulation results were analysed together with the analytical model to better comprehend rolling and/or sliding phenomena that are often observed in helmet oblique impacts. Three types of helmet-to-ground interactions are found when the helmet impacts ground from low to high tangential velocities: (1) helmet rolling without slipping; (2) a combination of sliding and rolling; and (3) continuous sliding. The tangential impulse transmitted to the head-helmet system, peak angular head kinematics and brain strain increase almost linearly with the tangential velocity when the helmet rolls but plateaus when the helmet slides. The critical tangential velocity at which the motion transit from the rolling regime to the sliding regime depends on both the falling height and friction coefficient. Typically, for a fall height of 1.63 m and a friction coefficient of 0.45, the rolling/sliding transition occurs at a tangential velocity of 10.8 m/s (38.9 km/h). Low sliding resistance in helmet design, i.e. by the means of a lower friction coefficient between the helmet outer shell and ground, has shown a higher reduction of brain tissue strain in the sliding regime than in the rolling regime. This study uncovers the underlying dynamics of rolling and sliding phenomena in high-speed oblique impacts, which largely affect head impact biomechanics. Besides, the study highlights the importance of testing helmets at speeds covering both the rolling and sliding regime since potential designs for improved head protection at high-speed impacts can be more distinguishable in the sliding regime than in the rolling regime.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Finite element method, High-speed impact, Traumatic brain injury, Motorcycle, Helmet, Sliding and rolling, Tissue strain
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:kth:diva-266466 (URN)10.1016/j.aap.2019.105297 (DOI)000501651900007 ()31683233 (PubMedID)2-s2.0-85074186401 (Scopus ID)
Note

QC 20200114

Available from: 2020-01-14 Created: 2020-01-14 Last updated: 2020-05-11Bibliographically approved
Montanino, A., Saeedimasine, M., Villa, A. & Kleiven, S. (2019). Axons Embedded in a Tissue May Withstand Larger Deformations Than Isolated Axons Before Mechanoporation Occurs. Journal of Biomechanical Engineering, 141(12)
Open this publication in new window or tab >>Axons Embedded in a Tissue May Withstand Larger Deformations Than Isolated Axons Before Mechanoporation Occurs
2019 (English)In: Journal of Biomechanical Engineering, ISSN 0148-0731, E-ISSN 1528-8951, Vol. 141, no 12Article in journal (Refereed) Published
Abstract [en]

Diffuse axonal injury (DAI) is the pathological consequence of traumatic brain injury (TBI) that most of all requires a multiscale approach in order to be, first, understood and then possibly prevented. While in fact the mechanical insult usually happens at the head (or macro) level, the consequences affect structures at the cellular (or microlevel). The quest for axonal injury tolerances has so far been addressed both with experimental and computational approaches. On one hand, the experimental approach presents challenges connected to both temporal and spatial resolution in the identification of a clear axonal injury trigger after the application of a mechanical load. On the other hand, computational approaches usually consider axons as homogeneous entities and therefore are unable to make inferences about their viability, which is thought to depend on subcellular damages. Here, we propose a computational multiscale approach to investigate the onset of axonal injury in two typical experimental scenarios. We simulated single-cell and tissue stretch injury using a composite finite element axonal model in isolation and embedded in a matrix, respectively. Inferences on axonal damage are based on the comparison between axolemma strains and previously established mechanoporation thresholds. Our results show that, axons embedded in a tissue could withstand higher deformations than isolated axons before mechanoporation occurred and this is exacerbated by the increase in strain rate from 1/s to 10/s.

Place, publisher, year, edition, pages
ASME Press, 2019
Keywords
DAI, injury thresholds, mechanoporation, multiscale
National Category
Other Medical Engineering
Identifiers
urn:nbn:se:kth:diva-266763 (URN)10.1115/1.4044953 (DOI)000506878100014 ()
Funder
Swedish National Infrastructure for Computing (SNIC), SNIC2017-1-491Swedish Research Council, VR-2016-05314
Note

QC 20200122

Available from: 2020-01-20 Created: 2020-01-20 Last updated: 2020-02-17Bibliographically approved
Zhou, Z., Li, X. & Kleiven, S. (2019). Biomechanics of acute subdural hematoma in the elderly: A fluid-structure interaction study. Journal of Neurotrauma, 36(13), 2099-2108
Open this publication in new window or tab >>Biomechanics of acute subdural hematoma in the elderly: A fluid-structure interaction study
2019 (English)In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 36, no 13, p. 2099-2108Article in journal (Refereed) Published
Abstract [en]

Acute subdural hematoma (ASDH) due to bridging vein (BV) rupture is a frequent and lethal head injury, especially in the elderly. Brain atrophy has been hypothesized to be a primary pathogenesis associated with the increased risk of ASDH in the elderly. Though decades of biomechanical endeavours have been made to elucidate the potential mechanisms, a thorough explanation for this hypothesis appears lacking. Thus, a recently improved finite element head model, in which the brain-skull interface was modelled using a fluid-structure interaction (FSI) approach with special treatment of the cerebrospinal fluid as arbitrary Lagrangian-Eulerian fluid formulation, is used to partially address this understanding gap. Models with various degrees of atrophied brains and thereby different subarachnoid thicknesses are generated and subsequently exposed to experimentally determined loadings known to cause ASDH or not. The results show significant increases in the cortical relative motion and BV strain in the atrophied brain, which consequently exacerbates the ASDH risk in the elderly. Results of this study are suggested to be considered while developing age-adapted protecting strategies for the elderly in the future.

Place, publisher, year, edition, pages
Mary Ann Liebert, 2019
National Category
Medical and Health Sciences Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-243833 (URN)10.1089/neu.2018.6143 (DOI)000473049600431 ()30717617 (PubMedID)2-s2.0-85068219142 (Scopus ID)
Note

QC 20190212

Available from: 2019-02-06 Created: 2019-02-06 Last updated: 2020-02-17Bibliographically approved
Zhou, Z., Li, X. & Kleiven, S. (2019). Biomechanics of periventricular injury. Journal of Neurotrauma
Open this publication in new window or tab >>Biomechanics of periventricular injury
2019 (English)In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042Article in journal (Other academic) Submitted
National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-263069 (URN)
Note

QCR 20191029

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2019-11-13Bibliographically approved
Zhou, Z., Li, X., Kleiven, S. & Hardy, W. N. (2019). Brain Strain from Motion of Sparse Markers. Stapp Car Crash Journal, 63
Open this publication in new window or tab >>Brain Strain from Motion of Sparse Markers
2019 (English)In: Stapp Car Crash Journal, ISSN 1532-8546, Vol. 63Article in journal (Refereed) Published
Abstract [en]

Brain strain secondary to head impact or inertial loading is closely associated with pathologic observations in the brain. The only experimental brain strain under loading close to traumatic level was calculated by imposing the experimentally measured motion of markers embedded in the brain to an auxiliary model formed by triad elements (Hardy et al., 2007). However, fidelity of this strain calculation as well as the suitability of using triad elements for three-dimensional strain estimation remains to be verified. Therefore, this study proposes to use tetrahedron elements as a new approach to estimate the brain strain. Fidelity of this newly-proposed approach along with the previous triad-based approach is evaluated with the aid of a finite element (FE) head model by numerically replicating the experimental impacts and strain estimation procedures. Strain in the preselected brain elements obtained from the whole head simulation exhibits good correlation with its tetra estimation which exceeds triad estimation, indicating that the tetra approach more accurately estimates the strain in the preselected region. The newly calculated brain strain curves using tetra elements provide better representation of the experimental brain deformation and can be used for strain validation of FE head models.

National Category
Medical Engineering
Identifiers
urn:nbn:se:kth:diva-263068 (URN)2-s2.0-85082974041 (Scopus ID)
Note

QCR 20191029

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2020-05-25Bibliographically 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: 2020-03-09Bibliographically approved
Meng, S., Cernicchi, A., Kleiven, S. & Halldin, P. (2019). High-speed helmeted head impacts in motorcycling: A computational study. Accident Analysis and Prevention
Open this publication in new window or tab >>High-speed helmeted head impacts in motorcycling: A computational study
2019 (English)In: Accident Analysis and Prevention, ISSN 0001-4575, E-ISSN 1879-2057Article in journal (Refereed) Accepted
Abstract [en]

The motorcyclist is exposed to the risk of falling and impacting ground head-first at a wide range of travellingspeeds – from a speed limit of less than 50km/h on the urban road to the race circuit where speed can reach well above 200km/h. However, motorcycle helmets today are tested at a single and much lower impact speed, i.e. 30km/h. There is a knowledge gap in understanding the dynamics and head impact responses at high travelling speeds due to the limitation of existing laboratory rigs. This study used a finite element head model coupled with a motorcycle helmet model to simulate head-first falls at travelling speed (or tangential velocity at impact) from 0 to 216km/h. The effect of different falling heights (1.6m and 0.25m) and coefficient of frictions (0.20and 0.45) between the helmet outer shell and ground were also examined. The simulation results were analysed together with the analytical model to better comprehend rolling and/or sliding phenomena that are often observedin helmet oblique impacts. Three types of helmet-to-ground interactions are found when the helmet impacts ground from low to high tangential velocities: (1) helmet rolling without slipping; (2) a combination of sliding and rolling; and (3) continuous sliding. The tangential impulse transmitted to the head-helmet system, peak angular head kinematics and brain strain increase almost linearly with the tangential velocity when the helmet rolls but plateaus when the helmet slides. The critical tangential velocity at which the motion transit from the rolling regime to the sliding regime depends on both the falling height and friction coefficient. Typically, for a fall height of 1.63m and a friction coefficient of 0.45, the rolling/sliding transition occurs at a tangential velocity of 10.8m/s (38.9 km/h). Low sliding resistance in helmet design, i.e. by the means of a lower friction coefficient between the helmet outer shell and ground, has shown a higher reduction of brain tissue strain in the sliding regime than in the rolling regime. This study uncovers the underlying dynamics of rolling and sliding phenomena in high-speed oblique impacts, which largely affect head impact biomechanics. Besides, the study highlights the importance of testing helmets at speeds covering both the rolling and sliding regime since potential designs for improved head protection at high-speed impacts can be more distinguishable in the sliding regime than in the rolling regime.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Engineering and Technology Medical and Health Sciences
Identifiers
urn:nbn:se:kth:diva-262731 (URN)10.1016/j.aap.2019.105297 (DOI)000501651900007 ()31683233 (PubMedID)2-s2.0-85074186401 (Scopus ID)
Note

QC 20191021

Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2020-05-11Bibliographically approved
Saeedimasine, M., Montanino, A., Kleiven, S. & Villa, A. (2019). Impact of lipid composition and ion channel on the mechanical behavior of axonal membranes: a molecular simulation study. Paper presented at Joint 12th EBSA European Biophysics Congress / 10th IUPAP International Conference on Biological Physics (ICBP), JUL 20-24, 2019, Madrid, SPAIN. European Biophysics Journal, 48, S99-S99
Open this publication in new window or tab >>Impact of lipid composition and ion channel on the mechanical behavior of axonal membranes: a molecular simulation study
2019 (English)In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 48, p. S99-S99Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
SPRINGER, 2019
National Category
Biophysics
Identifiers
urn:nbn:se:kth:diva-255420 (URN)000473420400263 ()
Conference
Joint 12th EBSA European Biophysics Congress / 10th IUPAP International Conference on Biological Physics (ICBP), JUL 20-24, 2019, Madrid, SPAIN
Note

QC 20190815

Available from: 2019-08-15 Created: 2019-08-15 Last updated: 2019-08-15Bibliographically approved
Li, X., Sandler, H. & Kleiven, S. (2019). Infant skull fractures: Accident or abuse?: Evidences from biomechanical analysis using finite element head models. Forensic science international, 294, 173-182
Open this publication in new window or tab >>Infant skull fractures: Accident or abuse?: Evidences from biomechanical analysis using finite element head models
2019 (English)In: Forensic science international, Vol. 294, p. 173-182Article in journal (Refereed) Published
Abstract [en]

Abusive Head Trauma (AHT) is considered by some authors to be a leading cause of traumatic death in children less than two years of age and skull fractures are commonly seen in cases of suspected AHT. Today, diagnosing whether the observed fractures are caused by abuse or accidental fall is still a challenge within both the medical and the legal communities and the central question is a biomechanical question: can the described history explain the observed fractures? Finite element (FE) analysis has been shown a valuable tool for biomechanical analysis accounting for detailed head geometry, advanced material modelling, and case-specific factors (e.g. head impact location, impact surface properties). Here, we reconstructed two well-documented suspected abuse cases (a 3- and a 4-month-old) using subject-specific FE head models. The models incorporate the anatomical details and age-dependent anisotropic material properties of infant cranial bones that reflect the grainy fibres radiating from ossification centres. The impact locations are determined by combining multimodality images. The results show that the skull fracture patterns in both cases of suspected abuse could be explained by the described accidental fall history, demonstrating the inherent potential of FE analysis for providing biomechanical evidence to aid forensic investigations. Increased knowledge of injury mechanisms in children may have enormous medico-legal implications world-wide. 

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Abusive Head Trauma; Multiple skull fractures; Finite element head model; Ossification centers; Impact location
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-259171 (URN)10.1016/j.forsciint.2018.11.008 (DOI)000454861200029 ()30529991 (PubMedID)2-s2.0-85057577148 (Scopus ID)
Note

QC 20190923

Available from: 2019-09-12 Created: 2019-09-12 Last updated: 2020-03-09Bibliographically approved
Montanino, A., Deryckere, A., Famaey, N., Seuntjens, E. & Kleiven, S. (2019). Mechanical characterization of squid giant axon membrane sheath and influence of the collagenous endoneurium on its properties. Scientific Reports, 9(1), Article ID 8969.
Open this publication in new window or tab >>Mechanical characterization of squid giant axon membrane sheath and influence of the collagenous endoneurium on its properties
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2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, no 1, article id 8969Article in journal (Refereed) Published
Abstract [en]

To understand traumas to the nervous system, the relation between mechanical load and functional impairment needs to be explained. Cellular-level computational models are being used to capture the mechanism behind mechanically-induced injuries and possibly predict these events. However, uncertainties in the material properties used in computational models undermine the validity of their predictions. For this reason, in this study the squid giant axon was used as a model to provide a description of the axonal mechanical behavior in a large strain and high strain rate regime (ε=10%,ε⋅=1s−1), which is relevant for injury investigations. More importantly, squid giant axon membrane sheaths were isolated and tested under dynamic uniaxial tension and relaxation. From the lumen outward, the membrane sheath presents: an axolemma, a layer of Schwann cells followed by the basement membrane and a prominent layer of loose connective tissue consisting of fibroblasts and collagen. Our results highlight the load-bearing role of this enwrapping structure and provide a constitutive description that could in turn be used in computational models. Furthermore, tests performed on collagen-depleted membrane sheaths reveal both the substantial contribution of the endoneurium to the total sheath’s response and an interesting increase in material nonlinearity when the collagen in this connective layer is digested. All in all, our results provide useful insights for modelling the axonal mechanical response and in turn will lead to a better understanding of the relationship between mechanical insult and electrophysiological outcome.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Medical Engineering Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-255034 (URN)10.1038/s41598-019-45446-y (DOI)000472137700065 ()31222074 (PubMedID)2-s2.0-85067621816 (Scopus ID)
Note

QC 20190729

Available from: 2019-07-16 Created: 2019-07-16 Last updated: 2020-03-09Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-0125-0784

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