Finite Element Modeling of the Human Head

I want to thank my dear colleague Peter Halldin at the Department of Aeronautics, KTH, for being such a nice and helpful roommate , as well as, together with my two other colleagues at the Neuronics; Karin Brolin and Magnus Aare, for open minded and stimulating discussions. I am grateful to Professor Jan Bäcklund, head of the Department, for his enthusiasm. I want to thank the Engineering Research AB for providing me with excellent software and assistance. Especially acknowledged for all support with ls-dyna are Ragnar Lindström, Åsa Gökstorp, and Daniel Hilding. I would like to express my sincere gratitude to my supervisor, Professor Hans von Holst, who really is a source of optimism, encouragement, fruitful ideas and support. Thank you, Hans! My gratitude to all the supportive colleagues at the Department, which have greatly facilitated my work. For my beloved Silvia I don't have enough words, so I simply say ¡Te quiero! Abstract 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 …