Relationship among bone mineral density,collagen composition,and biomechanical properties of callus in the healing of osteoporotic fracture

道德认知不能仅停留于知识层面。它最终应该内化为学生的一种品质,升华为学生的一种精神,而传统的教学方法使学生获得的道德认识却难以实现这一升华。因此,我们在思想道德教育中必须融入现代教育理念,让学生从自身实际出发,以兴趣为先导,以内需为动力,以实践为载体,积极倡导自主学习、合作学习与探究学习。使学生的主体性得到充分的发挥,让学生在主动思考、写作探索、亲身经历中自主地去发掘,自主地去构建科学的道德认知,为自身思想道德素质的全面提高创设扎实的基础。

Objective： To study the change and relationship among bone mineral density （BMD）, collagen composition and biomechanical properties of the callus in the healing process of osteoporotic fracture. Methods： The osteoporotic rat model and fracture model were established through bilateral ovariectomy （OV＇X） and osteotomy of the middle shaft of the right hind tibiae, respectively. Ninety female SD rats were randomly divided into OVX group and sham group. With the samples of blood and callus, roentgenoraphic and histological observation were performed for the assessment of the healing progress of the fracture, and the serum concentration of TRAP-5b, proportion of type I collagen, BMD and biomechanical properties of the callus were measured. Results： The OVX group experienced a significant delay of fracture healing. The mean serum concentration of TRAP-5b of rats in the OVX group was much higher than that in the sham group after the operation （P 〈 0.05）, but the difference at the same time point after fracture was smaller than that before fracture （P 〈 0.05）. The BMD of the callus in both groups reached the peak value at the 6 th week after fracture while the proportion of the type I collagen and the biomechanical strength reached the peak at the 8th week. Conclusions. The deficiency of estrogen after the ovariectomy could induce the up-regulation of the osteoclasts activities, whereas the potency of further activation after fracture was depressed. Although the synthesis of collagen together with its mineralization determines the biomechanical properties of new bone, the accumulation of collagen could be assessed as an index in the prediction of biomechanical strength of bones independent of the bone mineral deposition.