Biomedical Engineering Reference
In-Depth Information
1
mm
Figure 4.10.
MicroCT image analysis showing the bone ingrowth architecture at the expense
of both the composite and MBCP gel.
PL DLLA tubes charged with 20% BCP granules (six mm in diameter and
eight mm in length with an open internal channel of four mm) were sterilised by
irradiation at 25 KGrays. The tubes were implanted in rabbit femoral epiphyses.
Some implants were kept empty, and others were fi lled with MBCP gel®. After
six months, both samples were well-integrated into newly-formed bone. The com-
posite showed considerable resorption on the surface and bone ingrowth into the
implant with osteoconduction at the surface of the BCP granules (Figure 4.10).
The shape of the implant was signifi cantly changed by bone ingrowth at the ex-
pense of the implant. As a result, secondary mechanical properties appeared
thanks to bone ingrowth at the expense of the composite, contrary to the pure
polymer. In the hole of the defect, large bone ingrowth was observed at the ex-
pense of the MBCP gel.
Bone trabeculae and direct bone formation were observed between and at
the surface of the BCP granules of the MBCP gel. The thickness of the newly-
formed bone at the surface was around 300
m. Bone architecture and bone
remodelling were observed only after six months of implantation. The bone
trabeculae were perpendicular to the shell of the newly-formed bone directly in
contact with the composite. All the surfaces evidenced by the 3D reconstruction
were osteoconductive and supported bone formation (Figure 4.11).
Resorbable polymers such as PLLA (poly lactide acid) and poly DL lactide
co-glycolide (PDLG) have been used in clinical applications for many years [70].
It is often reported that such polymers cannot have bioabsorption kinetics that
are adapted to bone reconstruction. The addition of a calcium phosphate like
μ
-
TCP, or calcium carbonate, improves resorption control, probably thanks to the
release of Ca and PO
4
ions, neutralising the acid released as a result of the hydro-
lysis of the polymer. In the composite using biphasic calcium phosphate granules,
β
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