Bone Ingrowth into the Parallel Cylindrical Tubes with Different Sizes of Porous Hydroxyapatite Implanted into the Rabbits

In this study, effects from pore size of the tube on the bone ingrowth and on the calcification of new bone permeated into the pore tube were examined through implantation of porous hydroxyapatite (HAp) in the lateral epicondyle in rabbits.The bone integration speed was strongly dependent on the pore size of the porous HAp. The 150-μm HAp provided a faster bone integration speed into the cylindrical tube than the 375-μm. However, when the pore size of the cylindrical tube in porous HAp was reduced to 20 μm, the bone integration speed into the cylindrical tube became slow. However, when the implanted period was prolonged to 8 weeks, the bone contact ratio into the 20-μm cylindrical tube dramatically increased and the bone density reached to74.0%. However, most new bones were remained as an osteoid bone. In contrast, the new bones formed inside of the 150-μm and 375-μm sized cylindrical tubes were calcified within the tube. It was concluded that the osteointegration into for the porous HAps and the calcification of osteoid formed were different with the pore size of the cylindrical tube. The optimum size of cylindrical tube was 150 μm.