Biomedical Engineering Reference
In-Depth Information
Keywords Biomechanics computed tomography
Finite element modeling
Human femur
Introduction
Femur, the longest and strongest bone in the skeleton is almost perfectly cylindrical
in the greater part of its extent. In the erect posture it is not vertical, being separated
above from its fellow by a considerable interval, which corresponds to the breadth of
the pelvis, but inclining gradually downward and medial ward, so as to approach its
fellow toward its lower part, for the purpose of bringing the knee joint near the line of
gravity of the body. The degree of this inclination varies in different persons, and is
greater in the female than in the male, on account of the greater breadth of the pelvis
[
1
]. Being an important structure, femur serves two distinct functions: it acts as a
supporting structure allowing the weight of the upper body to be transferred from the
hip joint to the knee joint and it also acts as a stiff structure about which muscles act to
facilitate movement at both the hip and knee joints. The neck of the femur is a point of
structural weakness and a common fracture site in elderly people, especially in
women suffering from osteoporosis and is usually associated with a fall and at age of
65 or above. Fracture of the shaft of the femur occurs when subjected to extreme force
such as in a road traffic accident. Thus, this complete study of human femur is
addressed under biomechanics. As biomechanics is the study of motions experienced
by living things in response to applied loads. Koch was the first who gave a complete
and thorough description of the structure of the femur and demonstrated the relations
which exist between the structure and the function as well as between the external and
internal architecture of the femur [
2
]. Macroscopically, the structure of femur con-
sists of two types: (1) cortical or compact bone which is a dense outer layer mainly
resisting bending and (2) cancellous or spongy or trabecular bone present in the
interior of mature bones; this structure mainly resists compression and bone elements
placing or displacing themselves in the direction of functional pressure according to
Wolff's Law [
3
]. The shape of the femur is asymmetric and curved in all three planes.
Hence, a 3D model is required for a quantitative stress analysis [
4
,
5
]. With minor
modifications CT scans of FE models can be used to generate reliable subject-specific
FE models that accurately predicts strains in quasi-axial loading configurations
[
6
-
9
]. A thorough understanding and behavior of femur is essential to elucidate the
femur fracture and provide better guidance to the artificial femur replacement.
Various works have been carried out to investigate the loading mode and stress
distribution [
10
,
11
]. For better understanding of femoral loading forces exerted by
the soft and hard tissues of the thigh together are considered, a 3D model is created
taking into account all thigh muscles, body weight, contact forces at the hip, patel-
lofemoral, and knee joints [
12
-
15
]. A mathematical model is developed to simulate
3D femur bone and femur bone with implant in the femoral canal, taking into account
stress distribution and total displacement during horizontal walking [
16
]. Material
properties of femur bones are evaluated to facilitate further study of total hip joint and
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