Biomedical Engineering Reference
In-Depth Information
which were confirmed by Yung et al., as being those which would profit a lot from
orthoses, since due to their design, they shift the center of pressure during gait to the
forefoot, apart from showing hyper pressures [ 48 ].
3
Techniques for Plantar Forces Analysis
As explained before, when analyzing gait, a variety of factors have to be accounted
for due to alteration on gait pattern or plantar forces, like body weight and height,
gait characteristics, foot geometry and deformities, patient tissues physiological
conditions, pathologies and others. In the case of diabetic patients, one can predict
the areas where ulcers will most probably be developed. It is known that shear
forces act as enablers in the weakening of plantar surface tissues, being more critical
during heel contact and during stance final phase, namely right before toe-off, than
during mid stance. Since GRF horizontal in-plane component is greater in these time
instants, the corresponding contact areas, namely under the calcanous and under
the metatarsal heads, are regions of major ulceration for a patient with diabetes. To
reduce the ulceration risk it is to use orthoses that allows redistributing plantar forces
into superior areas, since better foot accommodation reduces relative movement
between the two contact surfaces, decreasing shear stress.
With availability of new tools and technologies, it has become recent practice
to use CT images to obtain 3D computer body models. These models lead to
realistic simulation results and by associating them with experimental values is
possible to determine body internal stress and strains and predict their influence
in the individual comfort, namely by designing foot orthoses [ 27 ]. Geometry is
a key factor when studying strain, stress and plantar shear forces therefore any
simulation has to be well controlled and defined process. With geometrically well
defined anatomical structures, namely for the foot, it is possible to simulate all types
of situations affecting gait and stability of an obese patient, for example.
Nowadays there are many tools to create 3D anatomical model, some of them will
be explain in the next sections of this chapter. Nevertheless and in what concerns
the foot, the major difficulty is to obtain CT scans where the foot is in positions
usable for certain simulation studies, since the majority of CT scans are done with
the person lying down, leading to foot relative position being quite different from
adequate positioning for gait studies, for example.
3.1
Scanning 3D Objects
With a 3D scanner is possible to obtain and analyze a real object, in respect to its
shape and appearance, in a static or dynamic way. This collects data that can be used
to construct three dimensional models useful for several applications like industrial
design and inspection, orthotics and prosthetics, reverse engineering and prototyp-
ing (Fig. 4 ), structures quality control and documentation of cultural artifacts [ 2 ].
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