Repairing segmental bone defects with living porous ceramic cylinders: an experimental study in dog femora.

Twenty-one porous hydroxyapatite-tricalcium phosphate ceramic cylinders 1.5 cm long and 1.2 cm in diameter were swathed with fresh autogenetic periostea taken from 21 dogs and implanted in the same animals' muscles to get living ceramic bone substitutes. These substitutes contained autogenetic growth stimulators including osteoblasts and other multipotential cells. One month later, they were transferred to the segmental bone defect sites created in femoral diaphysis of the same animals. The roentgenograms showed that in time the boundaries between the cylinders and bone sections became vague. X-ray diffraction analysis indicated that the spectra of the samples tended to be similar to those of natural bones by 6 months postoperatively. Their bending strengths also increased gradually. After the cylinders were transferred from muscles to the bone defect sites, newly formed bone tissues rapidly increased and the cylinders gradually fused with the contacted bones 2 months later. By 4 and 6 months, bone tissue occupied most areas of the materials. The ratio of newly formed bone tissue had a large lead over the materials. Haversian systems were clearly observed and matured bone tissues filled the ceramic pores and connected with each other. Results suggested that culturing complexes that consist of autogenetic periostea and biomaterials, taking advantage of living organic culturing medium, should be an effective approach to get satisfactory bioactive bone substitutes. It also provides a basis for clinically repairing bone defects in bearing sites with complex bioceramics.