Histomorphometric evaluation of titanium implants in osteoporotic rabbits.

In this study, the osteointegration of two kinds of titanium implants were analyzed (cylindrical and screw-type) inserted in the tibiae of control (n = 8) and osteoporotic (n = 12) female rabbits. Osteoporosis was induced by the surgical removal of the ovaries (oophorectomy). Bone mass density of all animals was evaluated by densitometry of the tibiae and vertebrae. Densitometry was carried out at the beginning of the study and 4 months after oophorectomy. Mass loss in the tibia was not observed, however, in the vertebrae there was an 11% loss compared with the initial value. The implants remained for 8 weeks, after which the animals were then sacrificed and bone segments were analyzed by histomorphometry. The trabecular volume and mineral apposition rate was significantly greater in control animals than in osteoporotic animals, independent of which type of implant was used. In the osteoporotic animals, the area and osteoid perimeter were greater than in the control animals. By measuring the thickness of the compact layer in the tibia, it was observed that in the control animals, it was 28% thicker than in the osteoporotic animals. This study leads to the conclusion that bone formation was greater in the control animals than in the osteoporotic animals. The screw-type implants yielded the greatest formation of bone both in the control and in the osteoporotic animals.