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Consequences of head size following trauma to the human head
KTH, Tidigare Institutioner                               , Farkost- och flygteknik.ORCID-id: 0000-0003-0125-0784
KTH, Tidigare Institutioner                               , Farkost- och flygteknik.
2002 (engelsk)Inngår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 35, nr 2, s. 153-160Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The objective of the present study was to evaluate whether variation of human head size results in different outcome regarding intracranial responses following a direct impact. Finite Element models representing different head sizes and with various element mesh densities were created. Frontal impacts towards padded surfaces as well as inertial loads were analyzed. The variation in intracranial stresses and intracranial pressures for different sizes of the geometry and for various element meshes were investigated. A significant correlation was found between experiment and simulation with regard to intracranial pressure characteristics. The maximal effective stresses in the brain increased more than a fourfold, from 3.6 kPa for the smallest head size to 16.3 kPa for the largest head size using the same acceleration impulse. When simulating a frontal impact towards a padding, the head injury criterion (HIC) value varies from the highest level of 2433 at a head mass of 2.34 kg to the lowest level of 1376 at a head mass of 5.98 kg, contradicting the increase in maximal intracranial stresses with head size. The conclusion is that the size dependence of the intracranial stresses associated with injury, is not predicted by the HIC. It is suggested that variations in head size should be considered when developing new head injury criteria.

sted, utgiver, år, opplag, sider
2002. Vol. 35, nr 2, s. 153-160
Emneord [en]
Human head, Impact, Finite element analysis, Parametrization
HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-12474DOI: 10.1016/S0021-9290(01)00202-0ISI: 000173610100001OAI: oai:DiVA.org:kth-12474DiVA, id: diva2:315032
Merknad
QC 20100428Tilgjengelig fra: 2010-04-28 Laget: 2010-04-28 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Inngår i avhandling
1. Finite Element Modeling of the Human Head
Åpne denne publikasjonen i ny fane eller vindu >>Finite Element Modeling of the Human Head
2002 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The main objectives of the present thesis were to define the dimension of head injuries in Sweden over a longer period and to present a Finite Element (FE) model of the human head which can be used for preventive strategies in the future. The annual incidence of head injuries in Sweden between 1987 and 2000 was defined at over 22 000, cases most of which were mild head injuries. In contrast to traffic accidents, head injuriy due to fall was the most important etiology. Of special interest was that the number of hematoma cases has increased.

A detailed and parameterized FE model of the human head was developed and used to evaluate the effects of head size, brain size and impact directions. The maximal effective stresses in the brain increased more than a fourfold, from 3.6 kPa for the smallest head size to 16.3 kPa for the largest head size using the same acceleration impulse. The size dependence of the intracranial stresses associated with injury is not predicted by the Head Injury Criterion (HIC). Simulations with various brain sizes indicated that the increased risk of Subdural Hematoma (SDH) in elderly people may to a part be explained by the reduced brain size resulting in a larger relative motion between the skull and the brain with distension of bridging veins. The consequences of this increased relative motion due to brain atrophy cannot be predicted by existing injury criteria.

From studies of the influence of impact directions to the human head, the highest shear strain in the brain stem is found for a Superior-Inferior (SI) translational impulse, and in the corpus callosum for a lateral rotational impulse when imposing acceleration pulses corresponding to the same impact power. It was concluded that HIC is unable to predict consequences of a pure rotational impulse, while the Head Impact Power (HIP) criterion needs individual scaling coefficients for the different terms to account for differences in intracranial response due to a variation in load direction. It is also suggested that a further evaluation of synergic effects of the directional terms of the HIP is necessary to include combined terms and to improve the injuryprediction.

Comparison of the model with experiments on localized motion of the brain shows that the magnitude and characteristics of the deformation are highly sensitive to the shear properties of the brain tissue. The results suggest that significantly lower values of these properties of the human brain than utilized in most 3D FE models today must be used to be able to predict the localised brain response of an impact to the human head. There is a symmetry in the motion of the superior and inferior markers for both the model and the experiments following a sagittal and a coronal impact. This can possibly be explained by the nearly incompressible properties of brain tissue. Larger relative motion between the skull and the brain is more apparent for an occipital impact than for a frontal one in both experiments and FE model. This correlates with clinical findings. Moreover, smaller relative motion between the skull and the brain is more apparent for a lateral impact than for a frontal one for both experiments and FE model. This is thought to be due to the supporting structure of the falx cerebri.

Such a parametrized and detailed 3D model of the human head has not, to the best knowledge of the author, previously been developed. This 3D model is thought to be of significant value for looking into the effects of geometrical variations of the human head.

sted, utgiver, år, opplag, sider
Stockholm: KTH, 2002. s. ix, 49
Serie
Report. Department of Aeronautics ; 2002-9
Emneord
Finite element method (FEM), Human head, brain, head injury, epidemiology, statistics, simulations.
Identifikatorer
urn:nbn:se:kth:diva-3347 (URN)
Disputas
2002-05-29, 00:00 (engelsk)
Merknad
QC 20100428 NR 20140805Tilgjengelig fra: 2002-05-22 Laget: 2002-05-22 Sist oppdatert: 2010-04-28bibliografisk kontrollert

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