Pathophysiology
Patterns of injury can be considered in a number of ways:
Blunt Injury
Injuries that result from direct contact with a blunt object i.e. something hitting someone or someone hitting something. There may be overlying bruising, swelling or abrasions but damage to deeper structures may be less apparent, such as contusions, vascular damage, and fractures. Most RTCs, falls from height and horse-riding accidents cause blunt injuries.
Blunt trauma results in fracture, tearing by shear forces, pressure causing blowout type injuries, and coupcontrecoup injuries.
Penetrating injury
Any mechanism whereby the body surface is breached by an object leaving a wound.
Examples include stab wounds, gunshots, crossbow wounds, as well as patients being impaled on railings/objects.
In general, handguns, shotguns and hunting rifles are referred to as low-velocity weapons.
(High velocity weapons describes military grade weapons that can inflict greater damage).
Bullets travel in a straight line when stable, though can ricochet. An energy wave is produced as it passes through tissue, creating tearing injuries that extend further into tissues beyond the simple bullet wound track.
Stab wounds typically follow a direct path through the body resulting in damage along the line of the path itself(5), though this rarely happens with an individual in the anatomical position. As such, tracks may not be straight when you examine them.
Crush injury
This occurs when part of the body is subject to prolonged compression. The injury to soft tissues, muscles and nerves may be as a result of the direct trauma or lack of blood flow due to the compression causing distal ischaemia.
This can occur as a result of being trapped under heavy rubble/debris or entrapment in RTCs.
Crush asphyxia, a mechanical cause of hypoxia resulting from external compression in blunt thoracic trauma, may also develop.
Burns
Burns are tissue damage that result from heat, radiation, chemical or electrical contact. Burns are covered in more depth in other modules. It must be remembered that burns can co-exist with major traumatic injuries. If suggested by the mechanism both should be actively assessed for and treated e.g. explosions can cause burns (see below) alongside other injuries, and vehicle occupants can sustain burns due to subsequent vehicle fire with concomitant injuries from the impact.
Blast6
There are 4 mechanisms of blast injury caused by an explosion.
Primary blast injuries are caused by the travelling high pressure air wave and can be subtle and have a delayed presentation, such as tympanic membrane rupture or damage at air/solid interfaces such as alveoli or bowel linings. It may also produce significant injuries such as traumatic amputation or even vaporisation.
Secondary blast injuries are caused by debris that is displaced by the blast wind of the explosion, or materials that may be packed around an improvised explosive device, such as nails, hex nuts, bolts or ball bearings. Secondary blast injuries are more common than primary blast injuries and are the most common cause of mortality in victims of an explosion.
Tertiary blast injuries are caused when the person is displaced through the air and impacts on another object by the blast wind, or when a structure collapses and causes injury.
Quaternary blast injuries are those not included in the above. They can be caused by exposure to the resulting fire, fumes, radiation, biological agents, smoke, dust, toxins and environmental exposure, depending upon the source of the explosion.
Acceleration/deceleration injury
Occurs when a moving person comes to an abrupt stop, but internal body tissues continue to move with forward momentum, often with differential movement. This creates shearing forces and is most commonly seen with injuries within the thoracic aorta, immediately distal to the arch and can range from dissection to complete transection.
Acceleration/deceleration injuries may also be seen at the renal pedicles, the cervical-thoracic spinal junction and between white and grey brain matter7.