In vivo behavior in rabbit radius bone defect of scaffolds based on nanocarbonate hydroxyapatite

Bone defects treatment may require the use of biomaterials that behave as a support and promote bone regeneration. Limitations associated with the use of autografts and allografts make it necessary to design new synthetic bone substitutes. Some of the most promising biomaterials currently under investigation are based on nanocarbonate hydroxyapatite (nCHA). In this study, we studied the bone-inducing capacity of nCHA-based scaffolds alone (SAG) and enriched with osteostatin (SAGO) or with bone marrow aspirate(SAGB) after implantation for 12 weeks in a 15-mm long critical defect performed in the radius of New Zealand rabbits. Bone formation obtained was compared with a group with the unfilled defect (CE), as control group, and other with the defect filed with iliac crest autograft (GS), as gold standard. X-ray follow-up was performed at 2, 4, 6 and 12 weeks and μCT and histological studies at 12 weeks. The radiological results showed a greater increment in bone formation in the GS group (75%–100%), followed by the SAG and SAGB groups (50%–75%). μCT results showed an increase of bone volume/tissue volume values in GS group followed by SAG and SAGB groups (0.53, 0.40, and 0.31 respectively) compared with CE group (0.26). Histological results showed limited resorption of the nCHA scaffolds and partial osseointegration in the SAG and SAGB groups. However, in the SAGO group, the presence of connective tissue encapsulating the scaffold was detected. In SAG, SAGB, and increase of bone formation were observed compared with CE group, but less than the GS group. Thus, the investigated materials represent a significant advance in the design of synthetic materials for bone grafting, but further studies are needed to bring their in vivo behavior closer to autograft, the gold standard.