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Aims: Hydroxyapatite (HA) is widely known in orthopaedic surgery and is proved to be safe and effective in bone substitution. Actually synthetic HA is a merely reproduction of the chemical constitutes of the natural HA (Ca, P). New technologies demonstrate that it is possible to assembly new materials starting from the primary microscopic unit (nano molecules) with a process called “bottom to the top”, realizing macromolecules biologically active and smart. Even bone is nano structured in HA crystalline units (20–40 nm) regularly oriented upon collagen fibres (300 nm).

Methods: This study concern a new nano structured HA realized by an auto assembled process “biologically inspired”, like in human bone formation, of nano HA crystals and collagen as to realize a new material very similar to natural bone. Samples of the nano-HA were tested in living bone in vivo (rabbits) and compared with a synthetic Mg-HA (Ha added with Magnesium). Macroscopic, radiographic, light microscopic and SEM analysis were performed periodically. New osteogenesis, bone ingrowth and ongrowth, bone apposition rate were evaluated up to 12 weeks. :The preliminary results of this study showed for both the biomaterials optimal bone apposition and biocompatibility. In the first month an earlier osseointegration was observed in traditional Mg-HA samples. The histological examination revealed a primary direct bone apposition from the surrounding living bone. The Nano-HA samples showed a slower secondary bone apposition, may be because of the initial larger gap and consequent lesser direct contact between the material and the guest bone. No adverse effect or reactive phenomenon were observed.

Conclusions: This study demonstrates the reliability of this new nano structured HA that demonstrates to be biologically active and useful in bone substitution. Further studies will reveal new promising improvements in bone substitution with interesting multidisciplinary innovations.

The abstracts were prepared by Ms Grazia Gliozzi. Correspondence should be addressed to her at the Italian Orthopaedic Research Society, Laboratory for Pathophysiology, Instituti Ortopedici Rizzoli, University of Bologna, Bologna, Italy.