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International audience; The aim of this work was to compare the osteogenicity of calcium phosphate ceramic granules with autologous bone graft in ectopic and orthotopic sites. Biphasic calcium phosphate (BCP) granules composed of hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) in a 60/40 ratio were sintered at 1050, 1125 and 1200 °C, producing different microporosities. Either BCP ceramic granules or autologous bone chips (n = 7) were implanted into paraspinal muscles. Osteoinduction was not observed in either the BCP implants or autologous bone chips after 6 or 12 weeks in the ectopic sites. Hollow and bored polytetrafluoroethylene (PTFE) cylinders were filled with autologous bone, BCP granules or left empty, then implanted into critical-sized defects in femoral epiphyses. The PTFE cylinders left empty contained marrow and blood vessels but not mineralized bone, indicating that this model prevented bone ingrowth (0.56 ± 0.43% at 12 weeks). Bone formation was observed in contact with the BCP1050 and BCP1125 granules in the femoral sites after 6 weeks. The amount of bone after 12 weeks was 5.6 ± 7.3 and 9.6 ± 6.6% for BCP1050 and BCP1125, respectively. Very little bone formation was observed with the BCP1200 implants (1.5 ± 1.3% at 12 weeks). In both the ectopic and orthotopic sites, autologous bone chips were drastically resorbed (from 19.4 ± 3.7% initially to 1.7 ± 1.2% at 12 weeks). This study shows that synthetic bone substitutes may have superior stability and osteogenic properties than autologous bone grafts in critical-sized bone defects.

International audience; This study evaluated the in vivo behavior of an injectable calcium phosphate bone cement implanted in bone defects at the distal end of rabbit femora. After 3 weeks, samples were harvested and processed for undecalcified sectioning. Scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared microspectroscopy showed direct contact of bone and cement without soft tissue interposition, biocompatibility, and bioactivity with osteoconductive properties.

International audience; In this paper we report a new method that permitted for the first time to selectively track a polysaccharide-based hydrogel on bone tissue explants, several weeks after its implantation. The hydrogel, which was developed for bone healing and tissue engineering, was labelled with a ruthenium complex and implanted into rabbit bone defects in order to investigate its in vivo degradation. 1, 2, 3 and 8 weeks after surgery, the bone explants were analyzed by synchrotron X-ray microfluorescence, infrared mapping spectroscopy, scanning electron microscopy, and optical microscopy after histological coloration. The results showed that the labelled polysaccharide-based hydrogel was likely to undergo phagocytosis that seemed to occur from the edge to the center of the implantation site up to at least the 8th week.

International audience; A new injectable and self-crosslinkable bone substitute (IBS2) was developed for filling bone defects. The IBS2 consisted of a chemically modified polymer solution mixed with biphasic calcium phosphate (BCP) ceramic particles. The polymer hydroxypropylmethyl cellulose was functionalized with silanol groups (Si-HPMC) and formed a viscous solution (3 wt %) in alkaline medium. With a decrease in pH, self-hardening occurred due to the formation of intermolecular -Si-O- bonds. During setting, BCP particles, 40 to 80 microm in diameter, were added to the polymer solution at a weight ratio of 50/50. The resulting injectable material was bilaterally implanted into critically sized bone defects at the distal femoral epiphyses of nine New Zealand White rabbits. The IBS2 filled the bone defects entirely and remained in place. After 8 weeks, bone had grown centripetally and progressed towards the center of the defects. Newly formed bone, ceramic, and nonmineralized tissue ratios were 24.6% +/- 5.6%, 21.6% +/- 5.8%, and 53.7% +/- 0.1%, respectively. Mineralized and mature bone was observed between and in contact with the BCP particles. The bone/ceramic apposition was 73.4% +/- 10.6%. The yield strength for the IBS2-filled defects was 16.4 +/- 7.2 MPa, significantly higher than for the host trabecular bone tissue (2.7 +/- 0.4 MPa). This study showed that BCP particles supported the bone healing process by osteoconduction while the Si-HPMC hydrogel created intergranular space for bone ingrowth. This new injectable and self-crosslinkable bone substitute could be used conveniently in orthopedic surgery for filling critical-size bone defects.