Biology Reference
In-Depth Information
different types of largemotor boat propeller blades dictated the use of a large torroidal pool and
an outrigging set to hold and run the motor and propeller at a controlled speed (
Kroman et al.,
2007
). On the opposite end of the spectrum, testing the fracture tolerance of human phalanges
requires only a small drop tower set-up and force gauge, or a similar device used tomonitor the
force of the impact (
Kroman, 2007
). Drop tower constructs are commonly used in experimental
biomechanics and can range from several stories high to small and portable.
The principle behind all of the constructs is the same
d
to deliver a reproducible impact
with a set speed and force. They often involve a “tower” constructed of a linear rail system,
and then an “impactor” that can often be changed depending on the size and shape needed.
On a triggered release, the impactor travels down the rail at a set speed and impacts the
object, which is stabilized at the bottom of the tower. To ensure that you have the correct
equipment for the project, the best place to start is with your university's engineering depart-
ment. Not only can they provide information on the best impact delivery device, they can
assist with the best design for data collection as well. Since each project in this type of trauma
research is unique, most of the testing equipment also has to be manufactured from scratch.
High-speed film is also a key component in experimental testing as it can provide critical
data for the study. With high-speed film, it is possible to visualize the fracture patterns as they
occur, offering anthropologists a unique opportunity to witness the injury as it is being
created, rather than work backwards (
Kroman et al., 2011
). While the high-speed film set-
up is very costly, most locations set up for impact already have a system in place that can
be used. Again, collaboration with a facility familiar with experimental and impact testing
is a key component to this type of research design.
Human Cadavers
The other critical component of experimental testing that needs to be addressed is the use
of human cadaveric tissue. Human tissue is by far the gold standard for testing, and the
preferred state of the tissue is what is described as a “fresh frozen” state; in other words,
tissue that has not undergone a process of decomposition or embalming. The data may be
influenced by changes in bone quality caused by decomposition, embalming, or drying
(
Reilly and Burnstein, 1974; Galloway, 1999
). Bone quality can also be compromised by the
chronological age of the individual (as bone density decreases with age), so it is also critical
to outline your stipulations for the demographics of the cadavers that you are willing to
accept (
Bonfield et al., 1985; Oxnard, 1993
). The preparation of the tissue is also very impor-
tant, since soft tissue presence and/or condition influences the biomechanics, especially in
the cranium (
McElhaney et al., 1976
). Removal of soft tissue from the impact site alters the
elastic and biomechanical properties; however, in some cases it will be necessary in order
to adequately collect the data or visualize the injury site.
Experimental testing is also restricted by the availability of human cadaveric material.
Sample sizes may be small and limited in age, ancestry, and sex representation. The most
common sources of cadaveric material are often from biomechanical research facilities or
medical school donation programs. For anthropology students, the first source to check would
be with your local medical school due to the fact that extra cadavers donated to the school are
often used for research projects. It is important to keep in mind that costs may include admin-
istrative expenses and those for cadaver preparation. You should be prepared for returning all
elements of the cadaver to the medical school for cremation at the end of the project. If your
