Modeling and Numerical Analysis of a Cervical Spine Unit - Biologically Responsive Biomaterials for Tissue Engineering - page 156

vertebra, 6—vertebral artery, 7—nucleus pulposus, 8—annulus fibrosus, 9—bone
screw, 10—locking screw, and 11—bone plate.
At this stage we can say that the assembly fully fulfills the requirements imposed
in the beginning, those of functionality and geometrical similarity with the physio-
logical structure.
The modeling and assembling techniques could be successfully used for the
development of a functional implanted unit at any spinal level.

7.4 Simulation of Mechanical Behavior for ICU

The multitude of the complex shape elements involved in cervical functional unit,
implanted or not, makes the analytical analysis of the structure's biomechanical
behavior difficult. By applying such levels of simplifications in order to make
possible a classical approach, the behavior of the structure can dramatically differ.
So, the FEM is more suitable for our simulation purpose.
FEA is a method developed to compute a real model in a mathematical form for
a better understanding of a highly complex problem [ 1, 19, 33 ] . The geometric
structure is defined as a finite number of simple elements composing a mesh. More
finite elements in a structure mean higher accuracy of the analysis.
Having the model of the ICU developed in Chap. 3 , this chapter proposes a
mechanical simulation of this functional unit, using static structural module of the
ANSYS Workbench environment.
The study's main objective is to identify the stress-strain conditions at the
bone-metal interface for certain loading and restricting conditions. The bone-metal
interface is defined by the contact surface between the screw threads and the bone
engaged between the threads. There is also a metal-to-metal interface materialized
by the contact surfaces between the screw head and the implant plate, which is not
part of the study.
We simulated three cases, respecting the three different geometries of the bone
screws Sr1 , Sr2, and Sr3 . The studies were individually performed for each
implanted unit, by following the same steps and under the same loading and fixation
conditions.
For valid simulation results, parameters like precise contacts between parts,
material properties, mesh size, and loading and fixing conditions were set up for
ICU and presented in the following.

7.4.1 FEA Main Stages

In order to perform the numerical analysis of the ICU, the ICU assembly was
exported from CAD environment in *.sat file format. The individual connections
between the parts represent a feature of the assembly, which is transferred to the