This study characterized human skin of the lower leg and scalp during the surgical
process of skin expansion. To our knowledge, this is the first study in this field, which
has provided results that considerably improve our understanding of human skin. A
detailed
in vivo analysis was carried out involving four different patients that allowed
for observation during the relaxation process. A comparison between the
in vivo and
numerical finite elements model of the expansion was used to identify the
material elastic parameters of the skin. After a comprehensive search of
constitutive equations for describing skin, Delfino’s constitutive equation was
chosen to model the
in vivo results. We considered skin as an isotropic,
homogeneous, hyperelastic, and incompressible membrane. The parameters of
Delfino’s exponential function obtained for the first skin stretch process were
= 40.0 KPa
and
= 20.2. As skin is extended, such as with expanders or in other procedures that
tighten the skin, the collagen fibers are also extended and cause stiffening in
the skin, which results in it being more and more resistant to expansion or
further stretching. We observed this phenomenon as an increase in parameters
and
as
subsequent expansions continued. The results of this study allow for the
quantification of stiffening of the skin after several stretches, when the skin becomes
more and more inelastic. These results are very encouraging and provide insight into
our understanding of the behavior of stretched skin and maybe other biological
tissues, as swollen artery and veins.
Keywords
characterization of human skin, finite elements, skin
expansion, biomembranes, constitutive equation
Laboratório de Membranas and
Biomembranas
Departamento de Engenharia Civil
Pontífica Universidade Católica
Rua Marquês de São Vicente, 225
Gávea
22451-900 Rio de Janeiro, RJ
Brazil