Female Foot Model for High-Heeled Shoe Design - Computational Biomechanics of the Musculoskeletal System - page 22

FIgure 2.1 (See color insert.) Fixing foot and ankle in a neutral position by foot orthosis (left), and foot
bones surface model (right).
on the bony surfaces. The tension-only truss element was used to reflect the tensile-resistive but
noncompression-resistive mechanical characteristics of ligaments. Musculotendon forces were
applied at their corresponding sites of insertion by defining contraction forces via axial connector
elements. To simulate the surface interactions among joint contact pairs, an automated surface-to-
surface contact algorithm in ABAQUS was used. Because of the lubricating nature of articulating
surfaces, the contact behavior between the contacting bony segments was idealized as frictionless.
The same contact modeling algorithm was used to simulate the contact between the foot and
supporting interface. The surface interaction between the plantar foot and external foot supporting
surface was assigned with a coefficient of friction of 0.6 (Zhang and Mak 1999). The surface inter-
action between the high-heeled shoe and ground support was assigned a coefficient of friction of 0.5
(Hanson, Redfern, and Mazumdar 1999).
2.1.2 m aterial p ropertieS
In order to reduce the complexity of the FE model, except for the bulk soft tissue, the foot bones,
cartilages, and ligaments were idealized as homogeneous, isotropic, and linearly elastic. The Young's
modulus ( E ) and the Poisson's ratio (ν) determine the linearly elastic properties. The mechanical prop-
erties of bone, cartilage, plantar fascia, and ligaments were selected from the literature. The foot sup-
port was made of Pedilen ® rigid foam 300 with material properties adopted from Shiina, Hamamoto,
and Okumura (2006). High-density polyethylene is a common material for the outsole (Lewis 2003). A
long, thin steel shankpiece is typically embedded within the middle of the outsole to reinforce the shank
of high-heeled shoes. The shankpiece was assigned the material properties of steel. A flat support, with
an upper layer assigned the properties of rigid foam (Shiina, Hamamoto, and Okumura 2006) and a
lower layer assigned the properties of a rigid body, was used to simulate the ground support.
2.2 aPPlICatIonS oF the FInIte element model For
examInIng eFFeCtS oF heel heIght
This study aimed at evaluating the biomechanical effects of high-heeled support on the ankle-foot
complex using an FE model. In this study, balanced standing on different heel-elevated foot sup-
ports was simulated. Physiological muscle forces on the foot and location of ground reaction force
(GRF) of each condition were derived and prescribed. Plantar pressure measurements and motion
analysis were conducted to obtain the loading and boundary conditions and validate the FE model
response.