Biology Reference
In-Depth Information
ballistic projectile into and out of the bone, and can be differentiated from one another based
on the location of the bevel (angled edge of the fracture surface) surrounding the defect (for a
more detailed explanation, please refer to
Berryman and Symes, 1998
).
Injuries from ballistic weapons also can have fracture patterns that are similar to those
described in blunt trauma. Radiating and concentric fractures are often seen around the
entrance and exit wound, and like blunt trauma simply represent the normal biomechanical
response of the bone to the large amount of force being imparted on it. However, a lesser
degree of plastic deformation is seen in ballistic trauma than in blunt trauma. A simple
way to remember this is that ballistic trauma often results in pieces of bone that can be easily
fit back together like a puzzle (elastic deformation) while blunt trauma often results in
warped pieces of bone that cannot be fit back together (plastic deformation). To reiterate,
this goes back to the high rate of speed of the applied force and the bone's response via reach-
ing the fracture threshold more quickly.
Sharp Trauma
Sharp trauma is best conceptualized as a subcategory of blunt trauma. Like blunt trauma,
sharp trauma is considered as occurring at a slower rate of loading. However, the major
difference between blunt and sharp trauma is the surface area of the impacting weapon
that interacts with soft tissue and bone. This then affects the resultant injury pattern. As
we learned earlier, stress is calculated as force divided by area. This is a critical concept
for understanding sharp trauma.
For example, imagine holding a 12-pound bowling ball in the palm of your hand. With the
12 pounds of force spread out over the 9 square inches of the palm, the amount of pounds per
square inch (or psi) would be 1.33. While the bowling ball may be very heavy, with a psi of
1.33 you could easily hold this object in your hand. Now consider holding the same 12-pound
bowling ball, however this time with a knifepoint in between the ball and your hand.
Suddenly, the entire 12 pounds is focused in the 0.0001 square inches of the knifepoint,
and the psi climbs to 120,000. Now you could not hold the bowling bowl in your hand
without injury, as 120,000 psi exceeds the tissue threshold for injury (
Kroman, 2007
). It is
this reduction in surface area that leads to the incised type of wound commonly seen with
sharp trauma. However, it is important to note that since sharp trauma is a subcategory of
blunt trauma the same type of fracture patterns can still result, with both radiating and
concentric fractures being common.
Thermal Trauma
Fractures and damage to bone can also be caused by a variety of outside forces acting on
the body. One of the most common forces that complicates trauma analysis is fire. Since fire is
often used as a method by perpetrators to hide the true manner of death, it is important to
understand how fire or thermal exposure damages bone in order to analyze the difference
between fractures created by the fire as opposed to those that may have been created by
events before the fire.
The study of thermal damage to bone is exceedingly complex and takes into consider-
ation variables such as the heat of the fire, duration of the fire, and the amount of soft tissue
