Kinematics is a branch of mechanics that deals with the motion of objects without references to the forces that cause that motion (PHTLS, 2016). Thus, the kinematics of trauma deals with looking at a trauma scene and attempting to determine what injuries might have resulted from the incident that took place (PHTLS, 2016). Certain injury patterns occur with certain mechanisms of injury; being aware of this allows pre-hospital providers to have high levels of suspicion for certain injuries when responding to a trauma call (PHTLS, 2016).
A traumatic event consists of three stages: the pre-event, the event, and the post-event (PHTLS, 2016). The pre-event consists of all the events that preceded the traumatic event, including the patient’s medical history and baseline mental status (PHTLS, 2016). The event phase is the traumatic event itself. It begins at the initial impact of one object against another (PHTLS, 2016). The post-event is where emergency medical providers can make a difference. Kinematics can be used to determine what injuries might be present (PHTLS, 2016). A scene survey is key to determine what mechanisms of injury might have occurred. (Caroline, 2014).
Kinetic energy is present in any traumatic event. Three collisions occur in a crash (PHTLS, 2016). The first collision is the vehicle of the crash hitting an object (PHTLS, 2016). This object may be moving or it may be stationary (PHTLS, 2016). It is important to note that the vehicle of a crash is not always an automobile. The second collision occurs when the patient hits the inside of the vehicle, crashes into an object, or is struck by energy in an explosion (PHTLS, 2016). The third collision is the internal organs of the body hitting the walls of the body, or being torn from their anchoring structures (PHTLS, 2016).
The formula for kinetic energy is (0.5)(mass)(velocity2). Thus, increasing velocity increases the amount of kinetic energy massively (PHTLS, 2016). This means that high-speed crashes have the potential to produce greater injury to patients. During a traumatic event, kinetic energy is transferred from an object to the human body, causing injury (PHTLS, 2016). Stopping distances help determine the amount of kinetic energy transferred in a traumatic event. The shorter the stopping distance, the more energy is transferred to the patient.
There are two types of trauma, blunt trauma and penetrating trauma. Blunt trauma occurs when the force is spread out over a larger area and the skin is not penetrated (Caroline, 2014). Penetrating trauma occurs when force is applied over a small area where the object can penetrate the skin and underlying tissue (Caroline, 2014). Blunt trauma can be caused by motor vehicle collisions, motorcycle accidents, pedestrian injuries, or falls (PHTLS, 2016). Penetrating trauma can be caused by gunshot wounds, knife attacks, or a multitude of other causes (Caroline, 2014).
Motor vehicle accidents have different kinematics depending on where the majority of the impact is taken. Frontal impacts cause the patient to move in an up and over a path, or a down and under path (PHTLS, 2016). Rear impacts are more damaging if the difference between the car speeds is large, or if the vehicle strikes another car after being hit from behind (PHTLS, 2016). Other impacts include lateral impacts, rotational impacts, and rollovers (PHTLS, 2016).
The severity of penetrating trauma depends on the frontal area of the projectile (PHTLS, 2016). The larger the frontal area, the more energy is transferred (Caroline, 2014). Frontal area size depends on the profile, tumble, and fragmentation (Caroline, 2014). It is important to remember that different weapons involved in penetrating trauma have different energy capacities (PHTLS, 2016). Low energy weapons include hand driven weapons such as knives (PHTLS, 2016). Medium energy weapons include handguns and rifles with muzzle velocities up to one thousand feet per second (PHTLS, 2016). High energy weapons have a muzzle velocity greater than two thousand feet per second (PHTLS, 2016).