Biomedical Engineering Reference
In-Depth Information
7.
Injectable Scaffolds for Bone and
Cartilage Regeneration
Claudio Migliaresi, Antonella Motta, and
Anthony T. DiBenedetto
7.1 Introduction
normally have simple geometric shapes that
do not readily conform to irregularly shaped
defects when implanted at a site in the body
[
Every year hundreds of thousands people
worldwide receive hip prostheses, implants for
bone repair, and surgical repair of degraded
cartilage. “Over
].
Bone graft substitutes have been classifi ed
into fi ve categories: allograft-based formula-
tions using allograft bone, alone or in combi-
nation with other materials; factor-based
formulations using natural and recombinant
growth factors, alone or in combination with
other materials; cell-based formulations using
cells to generate new tissue, alone or seeded on
a support matrix; ceramic-based formulations
using calcium phosphate and other ceramics,
alone or in combination; and polymer-based
formulations using both biodegradable and
nondegradable polymers, alone or in combina-
tion with other materials (see Chapter
66
million people worldwide
suffer from knee-joint failure each year due to
the breakdown of surrounding cartilage in the
joint and the inability of this cartilage to repair
itself through the natural regenerative pro-
cesses of healing in the body” [
15
27
]. Addition-
ally, at least
percent of the population suffers
from periodontal disease, and one-third of
these individuals will require a tooth implant
during their lifetime. The standard procedure
for repair of orthopedic injuries by tissue graft-
ing is to harvest tissue from the iliac crest
or femur of a patient and surgically placing it
at the injury site [
10
5
).
Approximately
% of the bone graft substi-
tutes currently available contain ceramics,
either alone or in combination with another
material [
60
]. A similar approach has
been developed for the strengthening and
rebuilding of a jaw bone by removing perios-
teal cells from the patient's jaw, cultivating
them in autologous blood serum mixed with
a matrix substance, and placing the mixture
in the degraded jaw bone [
59
].
In many clinical situations involving replace-
ment of hard or soft tissue, the aims of mini-
mizing the need for invasive surgery, avoiding
the medical complications associated with har-
vested tissue, and overcoming the limitations
of preformed scaffolds have assumed primary
importance. The use of noninvasive, injectable
scaffolds responds to these concerns. When
properly designed, an injectable scaffold can
provide a structure that encapsulates a homo-
geneous distribution of cells and bioactive
59
]. Although these
procedures are ideal from the point of view
of new bone growth in terms of osteoconduc-
tivity or osteoinductivity, both the harvesting
of the tissue and the placement of the graft
require invasive surgery that may result in
signifi cant complications. Furthermore, pre-
formed scaffolds used as a host for cells in vitro
42
95
