Biomedical Engineering Reference
In-Depth Information
Fig. 5.25
Model verification: a MR-image, b FE-model, c superposition of MR-image and FE-
model
3
:
53 kPa
and
E
1;
M
ΒΌ
3
:
1 kPa
for
gluteal
muscle
tissue
assuming
isotropic
material behaviour.
These derived parameters rely on measurements from one healthy 35 year old
male subject and one healthy 42 year old female subject and therefore may not
generally represent human gluteal soft tissue. Substantial individual variability in
the mechanical properties of soft tissue (cf.
Sect. 5.2.2.4
) may exist. To provide a
parameter classification accounting for gender, age and state of health, a more
comprehensive study could reveal more detailed information.
The main objective of this subsection was to present a possible technique to
establish biomechanical parameters for skin/fat and muscle tissue in the human
gluteal region. Focus was laid upon the separation of the specific tissue compo-
nents of the skin-fat-muscle compound and furthermore, the identification of the
biomechanical parameters of single tissue types. Although the derived parameters
apply to only a few individuals, the human gluteal tissue long-term moduli agree in
the order of magnitude, as has been previously reported.
Additional tissue parameter data derived from various volunteers is supplied as
follows (Table
5.5
):
Critical Review: The above listed parameters are not pure material parameters
but rather ''structural parameters'' or ''material-structural parameters'' since the
previously described measurements always involve the anatomical structure of
individual subjects. The parameters thus do not rely on standardized sample
geometries, and a region of proportional elongation and constant stress distribution
over the cross-section does not exist. Such a loading scenario is therefore not
comparable with a tensile or compression test sample as used in a laboratory testing.
The presented approach can, however, be justified by characterizing the tissue
material in vivo in contrast to ex vivo material characterization, which most often
does not adequately reflect existing conditions. Furthermore, the derived structure
parameters sufficiently model complex three-dimensional loading scenarios as
shown in the following paragraph, as well as in the experimental tissue-foam
interaction scenario presented in
Sect. 6.2.5
.
