Figure 2.

The geometric induction of bone formation: the concavity, the shape of life. Concavities (Ripamonti et al., 1999; Ripamonti, 2006), as prepared in solid discs of highly crystalline sintered hydroxyapatite constructs on both planar surfaces (Ripamonti et al., 1999), (A) spontaneously initiate the induction of bone formation on day 30 after rectus abdominis implantation (B,C). The newly formed intramembranous bone is tightly attached to the hydroxyapatite biomatrix (B light blue arrow) anchoring into the hydroxyapatite substratum (B,C). On day 90 (D),the newly formed bone within the concavity (light blue arrows) remodels still surfaced by contiguous osteoblasts (dark blue arrow) continuously secreting bone matrix. (E) Tissue harvest of highly crystalline sintered constructs (dark blue arrows) implanted in the rectus abdominis muscle. Highly vascularized mesenchymal tissue (light blue arrow) had grown within the concavities of the harvested sintered construct (dark blue arrow). (F) On day 30, differentiating cells at the hydroxyapatite interface express bone morphogenetic protein-7 (also known as osteogenic protein-1, OP-1) within the cytoplasm (light blue arrow) later embedded as gene product (G) (light blue arrow) within the microstructure of the hydroxyapatite biomatrix (white arrows).