Charged beads: generation of bone and giant cells.

Based on reports of electrically induced bone formation and findings that some materials used to promote bone ingrowth are stimulatory in bead form, the osteogenic potential of beads with different surface charges was examined. In this preliminary study, three types of Sephadex beads were injected into chick femora: type I, DEAE beads, positively charged; type II, CM beads, negatively charged; type III, G-25, uncharged. Beads were injected into the femoral midshaft, and after 3 days, 4 days, and 1 week, birds were sacrificed and femora were processed for histology. Type I beads: at 3 days, were surrounded by multinucleated giant cells; by 4 days, patches of bead-associated new bone were present along with giant cells; after 1 week, occasional bead-associated multinucleated cells were seen, but now most beads were surrounded by new intramedullary bone, forming an extensive bead-bone lattice. With bead types II and III, bead-associated new bone was seen at 3 days and 4 days only when beads lodged near the endosteum or in the metaphysis. At 7 days, no bone was seen with either of these two bead types. The response to the type I beads may be likened to a remodeling phenomenon with large numbers of giant cells at 3 days, new bone and giant cells at 4 days, and evidence only of bone formation at 7 days.