Biomedical Engineering Reference
In-Depth Information
Fig. 5.11 Schematic
representation of the
anatomic structure of the
human gluteal region
(transversal cut) (Sobotta
2007)
investigating the stress-strain state of gluteal soft tissue under loading. Material
parameters employed for human soft tissue within these computational investi-
gations have been derived in different manners. Specifically, buttock indentation
tests have been performed by (Todd and Thacker 1994) where the soft tissue
compound was assumed to be linearly elastic (E = 15.2 kPa, m = 0.49). (Oomens
et al. 2001) used rat data to represent human muscle tissue (l
1
= 12 kPa, a
1
= 30)
and skin parameters (l
1
= 16 kPa, a
1
= 10) derived from pig experiments using
the Ogden form for incompressible materials according to (3.203). Fat parameters
were assumed (l
1
= 20 kPa, a
1
= 5). In an additional study by (Oomens et al.
2003), again, animal data were employed as the basis for the investigation.
Using a neo-H
OOKEAN
material model, (Sun et al. 2005) made assumptions
about the material properties of skin (E = 0.85 MPa), fat (E = 0.01 MPa) and
muscle (E = 0.126 MPa) using a Poisson's ratio of m = 0.485. Literature based
parameters were used in a recent study by (Lim et al. 2006) using the M
OONEY
-
R
IVLIN
material model to describe human soft tissue behaviour. (Linder-Ganz and
Gefen 2007) used a neo-H
OOKEAN
material model employing material data of
porcine gluteal muscle as well as skin/fat data from indentation testing. The
instantaneous material constants were downsized to obtain the long-term material
response.
The 3D anatomical structure of the human buttock used in these investigations
was mostly based on reconstructed MRI-data, e.g. in (Sun et al. 2005) and
(Lim 2006), which provided realistic anatomical information. More abstract
models of the buttock, considering a distinct buttock section, were used in (Todd
and Thacker 1994) and (Oomens 2003) aiming to establish the stress-strain state in
tissue adjacent to prominent bone structures. Tissue layer thickness information, as
well as abstract anatomical structures, were derived from MR-images.
Besides geometric modelling approaches, the investigations previously men-
tioned were mainly based on tissue parameters derived from ex vivo animal
