[Hybrid substitute materials for bone. Initial results and perspectives].

Hybrid materials for use as bone substitutes are composed of a synthetic substance to which autologous osteogenic cells are bound. Identification of osteogenic stem cells among bone marrow stromal cells was followed by the demonstration that a host of growth factors, hormones, and cytokines have effects on cultured osteoblasts. Porous ceramics have been developed as vectors for osteogenic cells previously grown in vitro. Porous hydroxyapatite beads bearing stromal cells were used to fill experimental ulnar defects in dogs. The cells were first grown on flat supports then on the three-dimensional hydroxyapatite network. Invasion by histologically identifiable bone tissue was seen in the stroma cell-bearing implants but not in control implants without stromal cells. Materials containing osteogenic cells may prove extremely useful since bone substitutes including hydroxyapatite ceramics are implanted in sites where osteogenic cells are scarce.