2 Biomechanics of Closed Head Injury

This chapter discusses ways in which the brain is thought to be injured by a blunt impact to the head. The impacting object is assumed to be unlikely to penetrate the skull in the manner of a bullet, for example. The chapter is also concentrated on injuries to the brain, rather than lacerations and abrasions to the scalp or fractures of the skull. Obviously, if the skull is fractured and displaced inwards, then the part of the brain underlying the fracture will be injured. However, the brain can be very severely injured without the skull being fractured by the impact to the head (Gennarelli, 1980). Other intracranial injuries, such as subdural hematomas, are referred to briefly in relation to theories of mechanisms of primary injury to the brain. Secondary complications of head injury also affect the brain but they are not considered in this chapter.