Biomedical Engineering Reference
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Figure 4.12.
Collagen membrane containing MBCP® granules in the defect area.
new bone formation. Most models associate isolation from whole bone marrow
aspirates,
ex
vivo
expansion and then an attachment of mesenchymal stem cells
to the biomaterial. However there are several critical questions regarding the
quality of cell population isolation, the preservation of stem cell properties after
expansion, and, given the complexity of the model, its reproducibility in clinical
and surgical applications [72]. Moreover it is still a challenge in tumoral therapy,
and few studies have focused on the use of ceramics in irradiated bone. The
authors have previously reported good results for bone substitution with BCP
and bone marrow grafts in pre-radiation or post-radiation conditions in animal
studies [73,74]. Recently Jegoux et al. [75] reported the association of MBCP®
granules with a 20/80 HA/TCP ratio, a porcine collagen membrane, and bone
marrow for reconstruction in an irradiatepreclinical model.
Bone implantations were performed in rabbits. Segmental defects two cm in
length were surgically removed from the middle height of the femur. Osteosyn-
theses were performed by two superposed steel plates. A 30
40 mm resorbable
porcine collagen membrane was placed around the defect and then completely
fi lled with MBCP ® granules (Figure 4.12 ).
External fractionated radiation delivery was initiated two weeks after im-
plantation and performed at ONCOVET (59650 Villeneuve d'Ascq, France). The
delivered doses were calculated to be equivalent to those used in the treatment of
squamous cell carcinoma in rabbits. Irradiation was strictly localised on the hind
legs. Irradiation was delivered by low-energy photons from an X-ray source with
energy of 300KVp (PANTAK, THERAPAX DXT 300, Gulmay Medical, UK). A
total cumulative dose of 32 Gy was delivered at a rate of two Gy per day, four days
per week, for four weeks. One week after radiation, an autologous BM graft was
injected into the implanted site. One ml of BM was removed from the right
humeral epiphysis with an 18 G needle previously heparinated (50 mg of heparin
in 1000 ml of physiologic serum dilution) and were then immediately injected
transcutaneously into the centre of the implants under radioscopic control.
Eighteen weeks after the BM injection, the implants were analysed. Ilium
aspirate was technically more diffi cult to perform than in other sites in both spe-
cies, owing to the orientation of the cortical surface that was also covered in thick
muscles. Physiological bone marrow cells were found in all samples and cell
counts confi rmed that the grafts enclosed the physiological bone marrow without
blood recovery. The global abundance of haematopoietic cells was signifi cantly
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