Mechanism of scalp and skull injuries, concussion, contusion and laceration.

Abstract

EAD injury occurs as a result of the absorption of energy and may be classified as being either direct or indirect. A direct injury occurs when the head comes in contact with another object because of a difference in their velocities. Thus a moving object striking a stationary head or a moving head striking a stationary object will produce a direct injury. An indirect injury to the head is produced when the body is suddenly set in motion or brought to rest and forces are applied to the head indirectly, as in injuries or a fall in which the subject lands on his feet or buttocks. Regardless of whether the injury is direct or indirect, certain physical conditions are imposed on the head as energy is absorbed. These include deformation (change in shape of the skull), and acceleration or deceleration of the head caused by a blow. In the usual head injury in civilian life, deformation and acceleration or deformation and deceleration exist simultaneously or develop in rapid succession. With a direct injury it is possible that the head alone may be involved whereas with an indirect injury there is likelihood of damage not only to the head but to other parts of the body as well. In indirect injuries it is not essential for the head to come in contact with a nonmoving or slower moving object. The sudden acceleration of the head may produce sufficient physical force to result in intracranial damage. The socalled whiplash injuries of the head and neck and injuries of the head in a fall with the lower parts of the body first striking a nonmoving object are examples of indirect forces acting upon the head. Injuries of the craniospinal junction are frequent in head injury. Setting the freely movable head into motion results in stresses on the structures of the neck that fix the head to the body. These stresses are occasionally so severe as to result in ligamentous and muscular injury, fractures of the cervical spine and spinal cord and brain injury. A discussion of head injury must recognize the occurrence of craniocervical damage. It is quite possible that a patient suffering from a minor head injury may have sustained a major injury to the cervical spine.