Foot and Ankle Model for Surgical Treatment - Computational Biomechanics of the Musculoskeletal System - page 42

by defining contraction forces via axial connector elements. The GRF was applied as a concentrated
force to the rigid plate. The superior surfaces of the encapsulated soft tissue, distal tibia, and fibula
were fixed throughout the simulation and the foot shank positions were represented by turning the
rigid plate to the same angles. The boundary conditions applied are shown in Figure 3.2.
Balanced standing was also studied to investigate the arch deformation. Half of the body weight,
which was approximately 270 N for a 54-kg subject, was applied vertically on the foot. During bal-
anced standing, it was simplified such that only the Achilles tendon force was applied, neglecting the
other muscle forces.

3.3.2 S imulation of f irSt and S econd t arSometatarSal J ointS f uSion
To simulate midfoot joint fusion, the first and second TMT joints (Figure 3.3) were fused. The
tied articulating pairs were the medial cuneiform and first metatarsal, the medial cuneiform and
intermediate cuneiform, the intermediate cuneiform and second metatarsal, and the second meta-
tarsal and medial cuneiform (Figure 3.3). The three instants were simulated in the normal foot
model and the joint fusion model. The stress distribution on the bones, with particular interest
to the metatarsal bones, and the contact pressure on the adjacent joints of the fused region were
reported.

(a)

FIgure 3.3 The fixed bones of the first and second TMT joints (a).