By convention, injury is classified into several categories —these are
listed below.
Types
of injury
• Penetrating
• Nonpenetrating blunt
• Blast overpressure
• Thermal
• Chemical
• Other, including crush and barotrauma
In this chapter discussion centres on blunt, penetrating and blast
injury only.
Impact
between the body and an external object may result in tissue compression,
stretching, tearing and other deformation ranging in severity from trivial to
tissue injury beyond recoverable limits. The severity of damage is related to
many factors, the most important of which are the amount of energy transferred
and the nature and extent of the tissues over which it is applied.
In
penetrating injury of low velocity and low available energy, tissue damage is
focused over a small area, for example injuries caused by low-energy handguns,
knives, sharp instruments, spikes of glass, wood or metal. Injury severity and
outcome is related to the tissues involved. While low-velocity and low-energy
injury to the soft tissue in the forearm will be slight, a similar injury
involving the mediastinum might be lethal. In this case debates concerning
velocity and energy transfer become academic. In high-velocity injury,
associated
with the potential for high-energy transfer, damage to structures may
extend over a wide area remote from the wound track (see later).
In
blunt injuries mechanisms may be multiple and tissue damage of complex aetiology.
Mechanisms are listed below.
Mechanisms
of blunt injuries
•Acceleration
• Deceleration
• Rotational
• Stretch and shear
Victims
of motor vehicle accidents may be injured either by rapid deceleration or by
deformation with intrusion of vehicle components into the interior of the
vehicle. In a crash, as deceleration occurs, the occupant’s body is thrown
against the interior of the vehicle, often referred to as the ‘second
collision’. There is also a ‘third collision’ between soft tissues and
skeletal structures. All may contribute to injury, the extent of which will
depend on the body region involved, degree of restraint and severity of the
impact. Deformation and intrusion may result in blunt, penetrating or crush
injury. Prolonged entrapment may exacerbate matters. Ejection of an occupant may
occur, in which case rapid deceleration of the body occurs when it strikes the
ground or another vehicle. Ejection is associated with increased likelihood of
serious injury and death. When a pedestrian is struck by a moving vehicle there
is often an acceleration injury in addition to the direct trauma at the sites of
impact (Fig. 18.1). In an adult, injury is commonly due to bumper (fender)
impact to the limbs; in children, such an impact is over a wider area often
involving the chest and abdomen, and is associated with multiple injuries and
high mortality.
Patterns
of injuries in road traffic accidents
Although the variety of injuries that may occur in a road traffic
accident is vast, consistent patterns of injury are observed. The following are
typical combinations:
• head, face and cervical spine injuries;
• cervical whiplash and sternal injuries;
• sternal fracture and dorsal spine injury;
• lower rib fractures with injury to kidneys, liver or spleen;
• intra-abdominal and diaphragmatic injuries;
• pelvic fracture with lower urinary tract injury;
• lower limb fracture with hip dislocation or spinal fracture.
Seat-belt
injuries
While the wearing of automobile seat belts has undoubtedly saved many
lives and has also reduced the incidence and severity of injuries to passengers,
there are instances in which significant injury may be produced by their use.
These lesions are secondary to restraint caused by the seat belt, whereby the
occupant is forced by inertia against the straps as the vehicle rapidly
decelerates. Injury may also be attributed to incorrect seat belt usage
resulting in ‘submarining’ below the lap section of the belt on impact.
While injuries to the head, face, lung, heart, aorta and liver/spleen are rarer
since the introduction of seat belts, an increased incidence of injuries to
stomach, duodenum, pancreas, small bowel and mesentery has been noted. Major
intra-abdominal vessels may also be traumatised and fractures of the lumbar
spine can occur.
Airbags
There is considerable interest in the use of airbags for drivers and
front seat passengers. Evidence of their effectiveness and safety is gradually
emerging with increased use. While they have saved lives, deaths, particularly
in front-seat child passengers, have been reported. These were related to inadvertent
inflation in slow-speed impacts with inflation velocity sufficient in some cases
to decapitate. More evidence is required.
Death
following injury
Dr Donald Trunkey has pointed out that deaths following injury fall
broadly into three groups giving a distinct trimodal pattern (Fig.
18.2).
Immediate
deaths (50 per cent) — those occurring immediately or within the
first few minutes of injury and usually due to widespread damage to the brain or
upper spinal cord, the heart or major vessels, or multiple injuries. This first
peak is due to injuries which are generally lethal so that little can be done in
their management that is likely to affect outcome. Reduction of this peak can
only be achieved by preventive measures such as wearing of
• Early deaths (30 per cent) — those occurring within the first few
hours after injury [called by some the ‘golden hour(s)’ of trauma]. These
deaths are deemed preventable and are due to facial injuries with developing airway
obstruction, lethal disruption of the breathing mechanism, massive
blood loss into body cavities or from multiple long bone fractures leading to
collapse of the circulation, and dysfunction of the central
nervous system due to space-occupying collections of blood within the skull.
This became the basis of the ABCDE approach to initial assessment of the
severely injured (see later).
• Late deaths (20 per cent) — those occurring days or weeks after
injury, generally due to sepsis and multiple organ failure. Organ failure may
involve the heart, kidney, liver, lung, brain and haemopoietic systems.
it is among those cases represented by the second and third peaks that potentially preventable deaths occur.