Differences in Osteoconduction at Porous Hydroxyapatite according to Pore Geometry

Lee, Choon Ki; Chang, Bong Soon; Hong, Kug Sun

Abstract

PURPOSE: To assess the histological response and the reinforcing effects of bone ingrowth within porous hydroxyapatite implants depending on pore geometry.
MATERIALS AND METHODS
Three types of porous hydroxyapatite (cylindrical, sponge and cross type) were prepared. Forty-two white rabbits were divided into 3 groups and 5x5x7 mm-sized porous hydroxyapatite block was inserted through the medial cortical window of a proximal tibia. Histomorphological changes were examined using light and scanning electron microscopy. Biomechanical compression test was performed using material test machine.
RESULTS
At four weeks after implantation, the implants showed different histological changes depending on pore geometry. In cylindrical type porous hydroxyapatite, new bone was arranged in a concentric pattern around vessel similar to osteon. In sponge and cross type, irregular lamellar bone pattern was found. At 8 weeks, evidence of remodelling of new bone and bone marrow formation within porous hydroxyapatite was found. In biomechanical study, ultimate compressive strength significantly increased in all three implants after 8 weeks of implantation compared to preimplantation.
CONCLUSIONS
In cylindrical type porous hydroxyapatite, new bone was arranged in a concentric pattern around vessel, and compressive strength was highest. Sponge type porous hydroxyapatite showed irregular lamellar bone pattern and was rather flexible and ductile. Cross type porous hydroxyapatite showed borderline pattern of both cylindrical and sponge type porous hydroxyapatite.