Biomechanics of Impact Traumatic Brain Injury

Brain injury is a major cause of death and disability. A better understanding of the biomechanics of the brain under loading conditions that lead to injury can reduce mortality and morbidity. During normal activity, simple body movements such as twisting or jumping can cause the brain to deform within the cranial cavity. External head loading can be severe even during intentional body movements such as heading a football (soccer in the US), punching a boxer, or experiencing a head collision in US football. At large enough magnitudes, these head loadings can produce irreversible effects in the neural, axonal, and vascular structures of the brain. Mechanisms of tissue damage as well as links with clinical observations have not been completely characterized. Macro-mechanical and micro-mechanical characterization of head loading is a prerequisite to the determination of brain damage mechanisms.Characterization of head loading occurring in motor vehicle crashes is a subject of continuing research. This loading can be of the contact or non-contact type and produces complex brain response states with a wide range injury severity. Analysis of head impact in motor vehicle crashes has recently become more amenable to computational methods. Structural models of the head, particularly finite element models, have acquired a greater degree of sophistication and are accounting for anatomical detail and representing more phenomena. Coupled fluid-structure response is increasingly being built into established finite element applications. Techniques for the treatment of boundary conditions associated with the complex interactions between the various components of the brain are areas of developing research. Material response characterization still remains a difficult challenge since such studies require a living brain.The objective of this chapter is to describe the head-brain complex, with emphasis on its mechanical characteristics, and to give a brief exposition of some computational biomechanics techniques used in the study of the mechanisms of traumatic brain injury occurring under motor vehicle crash conditions.