Application of hydroxyapatite to stenal prosthesis on chidhood

Hydroxyapatite is generally considered to be the mineral component of bone. The purpose of this study is to evaluate hydroxyapatite for use as the sternal prosthesis on chilhood. In each of two-week-old rabbits, hydroxyapatite sternums (HA group n＝4) were implanted into the defect after resection of the sternum. As the cintril study, dense almina veremic sterums(Al-d group, n＝4) and porous almina ceramic sternums(al-p group, n＝4) were implnted. Further evaluation was made by macroscopic, microscopic and scanning electronographic examination at three months after implantation of the sternal psosthesis. Rabbits with hydroxyapatitie sterum developed as well as normal control and the others. They had littele deformity of chest and reconstruction with hydroxyapatite achieved acceptable stability and caused no foreign body reactions. The macroscopic examination recealed that the hydroxyapatite achieved acceptable stability and caused no foreign body reactions. The macroscopis wxamination revealed that the hydroxyapatate steunum was nor anchored directly to the residual sternum and costal cartilage but firmly adhesive to the thin conective tissue. Hisrologic analysis showed the implant was found to be encapsulated with a thin conective tissue layer and outer bone tissue without sungns of inflammation nor foreign body reaction. On the scanning electorographic examination, hydroxyapatite granules were clearly showed at the surface of implanted hydroxyapatite sternum compared with pre-implanted hydroxuapatite sternum. On theother hand, almina ceramic sternums had exacellent biocompatibility as well as hydroxyapatite sternum, but no change were found at the surface of almina ceramic sternums on the scanning electronographis wxamination. It was cuncluded that the hydroxyapatite was useful for a artificial sternum, although further technical improvement will be required.