Osteogenic response of hydroxyapatite cement implanted into the femur of rats with experimentally induced osteoporosis

Hydroxyapatite (HAP) cement was implanted in the femur of rats with experimentally induced osteoporosis, and the osteogenic response was studied histomorphologically. Osteoporosis was induced with ovariectomy with either a normal diet or a low-calcium diet. The rats fed a low-calcium diet after ovariectomy showed a decrease in both cumulative photodensity and the cortical thickness index. There was significant bone conduction in the femur of these rats, but the development of new bone was late, and the affinity index was small. The change in the affinity index with time was similar between the ovariectomy group and the ovariectomy/low calcium-group, suggesting the possibility that estrogen plays a major role in bone conduction.