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The epidemiology of head injuries in Sweden from 1987 to 2000
KTH, Superseded Departments, Aeronautical Engineering.ORCID iD: 0000-0003-0125-0784
KTH, Superseded Departments, Aeronautical Engineering.
2003 (English)In: Injury control and safety promotion, ISSN 1566-0974, Vol. 10, no 3, 173-180 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the present study was to evaluate the variability in the annual head injury incidence rate in Sweden from 1987 to 2000. It was hypothesized that the annual incidence rate would decrease over time due to a variety of primary preventive strategies that have been introduced in Swedish society. We used the Hospital Discharge Register at the National Board for Health and Welfare and head injury codes 800-804, and 850-854 from ICD9 system and S2.0-S2.9, and S6.0-S6.9 codes from ICD-10 system. We evaluated the patterns of age, gender, external cause of injury (E-code), type of injury, length of hospital stay, and trends over time. Head injuries due to transportation collision were reduced over the 14-year period analysis. Falls persisted as the dominant cause of head injury. Overall, men had 2.1 times the incidence of head injury compared to women. There was a decline in younger ages experiencing a head injury over this interval, while the number of head injuries among elderly people increased over time. Concussion was about three times more frequent than fractures. Hematoma and diffuse or focal contusions had a much lower incidence rate than concussion. Concussions and fractures decreased over time. Diffuse or focal injuries showed a steady rate of occurrence over the study interval while hematoma increased. Although length of hospital stay varied widely from zero to more than 50 days, 73.6% of hospital days were confined to two days or less. The incidence rate is stable over this time frame. While head injuries attributable to transportation accidents decreased, falls made up an increasing proportion of head injuries. Since we observed an increase in head injuries among elderly, primary prevention strategies may need to be targeted at this age group, and at preventing falls.

Place, publisher, year, edition, pages
2003. Vol. 10, no 3, 173-180 p.
Keyword [en]
adolescent, adult, aged, article, falling, female, head injury, human; incidence, length of stay, male, middle aged, statistics, Sweden, traffic accident
National Category
Engineering and Technology Medical and Health Sciences
URN: urn:nbn:se:kth:diva-12473PubMedID: 12861916OAI: diva2:315019
QC 20100429Available from: 2010-04-28 Created: 2010-04-28 Last updated: 2011-02-11Bibliographically approved
In thesis
1. Finite Element Modeling of the Human Head
Open this publication in new window or tab >>Finite Element Modeling of the Human Head
2002 (English)Doctoral thesis, comprehensive summary (Other scientific)
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.

Place, publisher, year, edition, pages
Stockholm: KTH, 2002. ix, 49 p.
Report. Department of Aeronautics, 2002-9
Finite element method (FEM), Human head, brain, head injury, epidemiology, statistics, simulations.
urn:nbn:se:kth:diva-3347 (URN)
Public defence
2002-05-29, 00:00 (English)
QC 20100428 NR 20140805Available from: 2002-05-22 Created: 2002-05-22 Last updated: 2010-04-28Bibliographically approved

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