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From NSW ITIM
Penetrating trauma is one of the four classifications of mechanism of injury. It is an uncommon trauma presentation in Australia.
Penetrating trauma can be defined as injuries caused by foreign objects penetrating the skin and disrupting underlying tissue and organs.
The penetrating object transfers it's kinetic energy to the body. This energy is then dissipated into the surrounding tissue, often focussed in a small area.
 Types of penetrating trauma
There are 4 common types of penetrating trauma:
Penetrating trauma can be classified based on the amount of energy produced:
 Stab wounds
Severity depends on:
Knifes are not only used with a stabbing force, but can also be used with a cutting or hacking force, such as that commonly caused by machetes. These forces can cause injuries such as fractures, amputations and blunt trauma to the underlying soft tissue.
 Gunshot wounds
Two main mechanism of injury:
 Permanent cavity
The permanent cavity is caused by the projectile crushing the tissue as it strikes. This cavity may be in a straight line or an irregular pathway as the bullet may be deflected into a number of angles after the initial penetration, such as after striking bone. As such, trying to predict the projectiles path is futile.
If the projectile deforms, such as the mushroom shape of a hollow point bullet, or yaw and tumbles, the permanent cavity size can be significantly increased.
 Temporary cavity
A pressure wave follows the penetrating projectile. The temporary cavity results when the penetrating projectile strikes tissue, which then accelerates radially away from where the projectile struck, like a pebble thrown into water.
The temporary cavity pressure may be at 4 times atmospheric pressure, pulsate a few times and last 4 or 5 milliseconds per pulsation.
Inelastic tissue, such as the liver, and fluid filled organs, such as the heart, are far more susceptible to disruption caused by the temporary cavity than that of more flexible tissue such as skeletal muscle and lung.
The damage caused in the human body by a bullet's temporary cavity can vary greatly, depending on the size of the cavity and its anatomic location. The forces of the temporary cavity follow the path of least resistance, separating tissue planes and tearing tissues where they are fixed and cannot be displaced.
Impalements are classified as low energy due to their typical low transfer of energy.
The penetrating object may be moving, such as equipment falling off a vehicle, or it may be stationary where a person falls or is pushed onto the object.
Any number of injuries are possible, dependant on the anatomical location of the penetration and the size and shape of the object.
Patient's who have sustained a impalement injury may be difficult to transport and manager as they may no be able to lay down with the penetrating object insitu. It may require specialist cutting equipment to free the person from the object sufficiently before being able to transport. As always, never remove an impaled object without being in an appropriate setting with specialist advice.
 Shrapnel woundsexplosion such as domestic gas bottle, an industrial accident or from an improvised explosive device (IED), commonly used by terrorists.
Shrapnel wounds may also be the result of a mechanical force such as a lawn mower deflecting an object such as stone and debris.
It may result in a single or multiple wounds.
It may be high or low energy, dependant on the cause.
The missile may be contaminated resulting in dirty wounds.
It may also be associated with other injuries, such as burns and blunt force trauma.
This image to the right shows multiple shrapnel wounds as a result of an improvised explosive device in a conflict zone. Each of the wounds must be examined thoroughly as they may be simply soft tissue injuries or may have resulted in internal injuries, not dissimilar to that of a gunshot wound.
 See also