Biomedical Engineering Reference
In-Depth Information
Introduction
Anatomy of Humerus Bone
Humerus is the longest and the largest bone of the upper limb. It comprises a
rounded head at the upper end, the shaft, and the expanded lower end. This bone
pivots in three rotational degrees of freedom from its proximal end at the shoulder
joint [
1
]. The head of the humerus forms less than half of the sphere and its smooth
surface is covered by hyaline cartilage which articulates with the glenoid cavity
with the scapula forming a ball and socket joint. It lies at an angle to the shaft and
fits into a shallow socket of the scapula also known as shoulder blade to form the
shoulder joint [
2
]. The anatomical neck is a slight constriction separating the head
from the rest of the upper end of the humerus. The shaft is almost cylindrical in the
upper half of its extent, prismatic and is flattened below [
3
]. It is not a weight
bearing bone and therefore weight bearing is not a factor and shortening does not
significantly worsen the end results. Humeral shaft fractures result from direct and
indirect trauma. Pure compressive forces result in proximal and distal humerus
fractures; bending forces, however, typically result in transverse fractures of the
humerus shaft [
4
]. Humerus connects the shoulder by articulating the humeral
head with the glenoid of the scapula, to the elbow by articulating the testal
humerus with the ulna and radius, as shown in Fig.
1
[
5
]. The elbow is one of the
few places in the body where two bones articulate with one bone [
6
].
Biomechanics of Bones
FE models of long bones constructed from CT data are an invaluable tool in the
field of bone biomechanics. The structural properties of bone consist of the size,
shape, and architecture of bones in addition to mechanical properties of bone
tissue [
7
]. Bone tissue is a type of dense connective hard tissue. Bones are
composed of inorganic salts impregnated in a matrix of collagen fibers, proteins,
and minerals. They maintain the shape of the body and assist in force transmission
during movement [
8
]. The mechanical properties of bone vary between species
and individuals or due to age and disease [
9
]. Bone mass is increased by
mechanical loading through the application of resistance or increased weight
bearing activity [
10
]. One method to analyze the loading of the bone is by bio-
mechanical modeling [
11
].
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