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Abstract
Osteoporosis is the commonest metabolic bone disorder that leads to increased mortality and morbidity especially in elderly. Most previous researches on osteoporosis studied the postmenopausal osteoporosis and its impact on the biochemical values of bone resorption and formation. Most previous studies also focused on treatment of osteoporosis by using antiresorptive drugs. The current study was designed to investigate the effects of immobilization -as one of the silent causes of osteoporosis- on bone structure, after different periods of immobilization. The aim of the present study is to find more natural costless sources for treatment of osteoporosis induced by immobilization.
The study included 75 adult male albino rat with average weight of 200 gm. They were divided into three groups. Group I (control group): included ten rats, group II (the immobilization group): were immobilized by casting of their right lower limb for two weeks (group IIa that included six rats) or four weeks (group IIb that included seven rats) and group III that received a dietary supplement during the same period of immobilization. Group III was divided into four groups according to the given dietary supplements. Group IIIa received Ca daily with immobilization at a dose of 0.09mg/gm body weight. Group IIIb received vitamin D with immobilization at a dose of 0.5µg/kg daily. Group IIIc received vitamin K daily with immobilization at a dose of 0.0009mg/gm body weight, and group IIId received both Ca and vitamin D (in the same previous doses) with immobilization. Each of these four groups was further subdivided into two sub groups; subgroup1 included six rats and subgroup 2 included seven rats. The experiment in subgroup 1 and 2 lasted for two weeks and four weeks respectively.
The distal end of the immobilized rat femur in different groups was processed and examined by different histological techniques. Scanning electron microscopic examination was performed, and then morhpohmetric studies were done for cancellous bone thickness, compact bone thickness, eroded surface percentage, osteoid surface percentage, osteoid thickness and the thickness of the outer fibrous layer and the inner osteogenic layer of the periosteum. Finally statistical analysis was done using one way ANOVA test.
Decreased periosteal activity was noticed in the immobilized groups and in the groups that received Ca with immobilization. Active periosteum was noticed in the immobilized groups that received vitamin D, or vitamin K or Ca and vitamin D with immobilization. Subperiosteal bone resorption occurred in the immobilized groups; while, subperiosteal new bone formation was noticed in the groups that received vitamin K with immobilization.
Multiple erosion cavities were frequently seen in the endosteal surface of the compact bone, in the immobilized groups and in the immobilized group that received Ca with immobilization. Microscopic fracture of the compact bone was also noticed in the immobilized group, while an almost normal structure of the compact bone was seen in the groups that received vitamin K with immobilization.
Button phenomenon, thin discontinuous widely separated bone trabecuale, osteolysis and erosion cavities were frequently noticed in the cancellous bone of the immobilized groups and in the groups that received Ca with immobilization. Fractured cancellous bone was noticed in the immobilized groups. Erosion cavities could also be seen in the cancellous bone trabeculae of the groups that received vitamin D with immobilization and less frequently seen in the groups that received Ca and vitamin D with immobilization. An almost normal structure of the cancellous bone was seen in the groups that received vitamin K with immobilization. Wide bone marrow spaces and increase number of marrow adipocytes were noticed in the immobilization groups and in the groups that received Ca with immobilization.
No osteoid layer could be detected in the cancellous bone trabecuale of the immobilized group, while minimal amounts of osteoid were seen in the groups that received either Ca or vitamin D with immobilization. A thick osteoid layer was seen on most bone trabecuale in the groups that received either vitamin K or Ca and vitamin D with immobilization.
Widening of the Haversian canals and cancellization of the compact bone were demonstrated in scanning electron microscopic examination of the immobilized group and the group that received Ca with immobilization.
The histomorphometric results confirmed most of the histological results. A significant decrease (p<0.05) was noticed in the mean outer cortical bone thickness, the mean cancellous bone thickness, the mean osteoid surface percentage and the mean osteoid thickness in immobilization group and in the groups that received either Ca or vitamin D with immobilization, when compared to the control group. The mean cancellous bone thickness also showed a significant decrease in the group that received both Ca and vitamin D with immobilization, when compared to the control group. The mean eroded surface percentage showed a significant increase in the immobilization group and in the groups received Ca or vitamin D with immobilization, when compared to the control group and a significant decrease was noticed in the groups that received vitamin K or Ca and vitamin D with immobilization, when compared with the immobilized group. The mean thickness of the outer fibrous layer of the periosteum in immobilized group showed a significant increase and the mean thickness of the inner ostesogenic layer of the periosteum showed a significant decrease when compared to the control group.