Advanced Trauma Life Support ATLS Student Course Manual 2018

406
BIOMECHANICS OF INJURY
in a 30-inch (75-cm) diameter circle at 40 yards (36 m).
However, the “shot” is spherical, and the coefficient of
drag through air and tissue is quite high. As a result,
the velocity of the spherical pellets declines rapidly
after firing and further after impact. This weapon can
be lethal at close range, but its destructive potential
rapidly dissipates as distance increases. The area of
maximal injury to tissue is relatively superficial unless
the weapon is fired at close range. Shotgun blasts can
carry clothing and deposit wadding (the paper or plastic
that separates the powder and pellets in the shell) into
the depths of the wound; these become a source of
infection if not removed.
Entrance and Exit Wounds
For clinical reasons, it may be important to determine
whether the wound is an entrance or exit wound. Two
holes may indicate either two separate gunshot wounds
or the entrance and exit of one bullet, suggesting the
path the missile may have taken through the body.
Missiles usually follow the path of least resistance once
they enter tissue, and clinicians should not assume
that the trajectory of the bullet followed a linear path
between the entrance and exit wound. Identification
of the anatomic structures that may be damaged and
even the type of surgical procedure that needs to be
done may be influenced by such information. An odd
number of wounds suggest a retained bullet or, less
likely, a tangential injury. Clinicians may be unable to
identify entrance and exit wounds precisely, nor is that
information always useful. It is more useful to describe
the anatomic location and appearance of wounds.
Bibliography
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