Biology Reference
In-Depth Information
local medical school is not an option, other sources of cadaveric material include services that
provide cadavers for surgical or medical research. However, these often come with a very hefty
price tag in addition to tight restrictions on use. See DiGangi and Moore (Chapter 2), this
volume, for information on the ethics inherent with studying human remains.
What About Animal Models?
With the paucity of available cadaveric material, and the ethical issues that accompany
their use, it may seem very tempting to use an animal substitute in place of human cadavers.
However, while easier to find and easier on the budget, there are also potential problems with
the use of nonhuman models for studying trauma and fracture biomechanics. The main
concern when dealing with the study of fracture biomechanics is the difference in the
strength and structure of human bone compared to animal bone. When comparing
nonhuman to human bone, the pig has the greatest similarity in bone structure to humans,
and for that reason is often used in a variety of
in vivo
orthopedic implant research (
Pearce
et al., 2007
). However, with that stated, pig models have consistently produced varying
degree of experimental results. Additionally, many researchers use “butcher grade” animals
due to easy availability. These animals are not fully skeletally mature, and their subadult
status adds yet another confounding variable to the mix. Animal models can provide a help-
ful alternative in research design, but biomechanical studies utilizing human cadavers are
still considered the gold standard in the field.
CASE STUDY: EXPERIMENTAL IMPACT BIOMECHANICS RESEARCH
INTO CRANIAL BASE FRACTURES
As discussed, experimental testing is a research method that is well suited for application
to questions regarding the specifics of fracture biomechanics. There are many areas of dispute
in the literature regarding the etiology of fracture patterns, and one such area of dispute has
focused on cranial base fractures. Cranial base fractures have been attributed to a wide range
of injuries as their causation, including falls, blows to the top of the skull, and blows to the
lateral or temporal area of the skull (
Berryman and Symes, 1998
). To address the questions
of (1) how cranial base fractures are created and (2) how they travel or propagate through
the skull, a cadaveric testing model was set up (
Kroman et al., 2005
). Fifteen fully fleshed,
unembalmed human cadaver heads were used for this test, since an animal model was not
biomechanically appropriate. A portion of the cranial vault was resected, along with the
brain and dura, to allow for direct visualization of the cranial base and the capture of the frac-
ture event by high-speed film. A drop tower system was utilized to ensure that a calibrated
and fully monitored blow was delivered to the specimen each time.
The specimens were impacted in different areas, which included near the vertex (top of the
vault), midway on the parietal, and from a lateral aspect. Five data acquisition load cells
(small devices used to record force) monitored the response of the bone and calculated the
compressive and shear stress during the impact in millisecond intervals. After testing,
each specimen was dissected, photographed, charted, and analyzed. Each cranium was
then processed down to clean bone to allow reconstruction and further visualization of the
fracture pattern. The data from the high-speed camera were also reviewed.
