Biomedical Engineering Reference
In-Depth Information
8.
Motion and Bone Regeneration
Ching-Chang Ko, Martha J. Somerman, and Kai-Nan An
8.1 Introduction
cascades that occur during wound healing.
Therefore, the fi rst portion of this chapter
(Section
) will review the biological aspects
of bone healing.
One of the most interesting aspects of the
regeneration process is that it allows alteration
of its cellular activities through physical means,
such as exercise or motion [
8
.
2
Bone is a living material composed of cells and
an extracellular matrix (ECM) that has a multi-
component structure [
]. The ECM of bone is
composed of three phases: an inorganic mineral
phase, an organic phase, and an aqueous phase.
The inorganic phase of bone is calcium
hydroxyapatite, Ca
10
(PO
4
)
6
(OH)
2
. The organic
phase consists primarily of collagen fi bers and
associated noncollagenous ECM proteins. The
molecular confi guration of collagen provides
binding sites for hydroxyapatite crystal nucle-
ation and growth. The ECM is created and
maintained by active bone cells: osteoblasts,
osteoclasts, and osteocytes. Osteoblasts and
osteocytes are involved in bone formation and
maintenance, respectively, whereas osteoclasts
promote resorption of bone [
4
].
This characteristic conveys information of
structure-functional relationships (adapta-
tion) during the early stages of regeneration.
The relationship between motion and bone
regeneration is thought to be preprogrammed
in cells. Physical deformation—the distortion
of tissue by movement—can be transmitted
into the cell cytoskeleton and converted into
biochemical signals for promotion of osteogen-
esis [
19
,
20
,
21
,
55
,
62
]. It is generally accepted that precise
engineering motion parameters (magnitude,
frequency, direction, etc.) can provide useful
tools for designing therapies to regenerate
bone. Specifi c clinical movements, such as
dynamization [
18
,
60
]. Bone is, in
general, dynamic and constantly being remod-
eled by the action of these cells, and thus can
regenerate itself.
Bone regeneration is an important function
of the living organism. It provides reparative
power to the vertebrae organism, including
the ability to unite broken bones and to refi ll
defects [
2
,
99
], osteogenic distraction
applied to healing callus [
28
57
,
58
,
59
], and orth-
odontic tooth movement [
], have been used
in efforts to increase bone formation. Bone
regeneration includes bone healing, osteogen-
esis, and osseointegration. In this order, the
second portion of this chapter (
95
]. A complicated bony fracture will
require a healing construct (callus) to glue the
fragmented bone together. This callus sets
the foundation for regeneration to occur. Bone
regeneration is defi ned as a dynamic process
that consists of episodes of cell recruitment,
cell differentiation, mineralization, and reor-
ganization of mineral structures [
110
) is
devoted to a review of adaptation theory and
mechanobiology as they relate to bone regen-
eration. Examples including load-enhanced
implant osseointegration and mandibular dis-
traction osteogenesis will be used to illustrate
the relationship between physical stimuli and
tissue regeneration.
8
.
3
and
8
.
4
].
These episodes are similar to the biological
22
,
110
110
