Integration of dense HA rods into cortical bone

HA ceramics are daily used in human surgery for bone healing partly due to their ability to integrate into bone. They are generally used under a macro porous form. The behaviour of dense HA after implantation is not so well kn own. We implanted within cortical sheep femurs dense pure HA-ceramics cylin ders for periods from 2 weeks to 18 months. The samples were then sectioned and examined using back-scattered and secondary SEM and the interface was analysed using EDS. Histomorphometry measurement was also performed using a n image analysis device coupled to a light microscope. It appeared that the cylinders were in direct contact with immature bone after three weeks. The bone maturated within three months. The implant surface showed moderate si gns of resorption and some grains were released from the surface. The resor ption zone was only a few mu m thick after 18 months. The bulk ceramic cont ained default zones of increased porosity. They can constitute fragile zone when located close to the surface in which the resorption rate is increase d. We conclude that dense pure HA is poorly degraded when implanted in cort ical bone. Degradation depends on the defaults found on the ceramic structu re and the remodelling of bone surrounding the material. (C) 1999 Elsevier Science Ltd. All rights reserved.