Biomedical Engineering Reference
In-Depth Information
Similar results were also obtained in a long term study (12 months) carried
out by Cipitria et al.
46
They implanted PCL-TCP scaffolds into a 3 cm tibial
segmental defect sheep model. At 12 months, bony bridging across the
defect site and greater bone formation around the scaffold were observed.
46
The amount of bone formation was insucient for clinically relevant
bridging of the defect. Thus, to stimulate sucient bone formation within
defect sites (especially when treating large segmental bone defects) it is
advisable to combine FDM/ME-fabricated 3D scaffolds with either osteo-
genic cells or bone growth stimulating agents.
More recently, Berner et al.
47
investigated the effect of lay-down pattern
(raster angle) of PCL-TCP scaffolds on bone regeneration. PCL-TCP scaf-
folds with two different raster angles (0/901 and 0/60/1201) were fabricated
and implanted into rat critically sized cranial defects for 12 weeks
(Figure 9.5).
47
Micro-CT, micro-compression and histological analysis all
revealed that the 0/60/1201 scaffolds showed lower bone formation in com-
parison to the 0/901 scaffolds.
47
This was the first time (to the authors'
knowledge) that differences in in vivo bone regeneration have been reported
from differences in architecture of scaffold struts. It was speculated that
differences in porosity, surface area may have affected nutrient diffusion
and attachment of new matrix onto the scaffold. This study highlights the
importance of scaffold macro-architecture. It is often easy to forget this
important aspect of scaffold design when looking at the micro-architectural
features such as scaffold surface roughness and functionalisation.
d
n
3
r
4
n
g
|
1
.
Figure 9.5
(a) Cranial defects were drilled with a 5 mm dental drill, (b) the bone
and the surrounding periosteum were carefully removed without dam-
aging the dura, (c) the scaffolds were press fitted with good contact
between the host bone and the scaffold. This was evident from the
explanted specimens which showed excellent scaffold integration
into the host bone with no fibrous capsule evident at 12 weeks in either
the 0/901 laydown pattern group (d) and the 0/60/1201 laydown pattern
group (e).
47
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