Degradation and Recovery of Bone: OVX and Treatment

描述（由申请人提供）：与年龄相关的骨折只能部分解释为骨量减少，骨量减少是随着年龄增长而普遍发生的。预测骨折失败的部分原因是：a)当使用投影x射线方法测量骨量时，丢失了几何信息；b)对骨骼失效特性的足够详细信息的无知；c)对骨骼体内载荷的详细信息的无知（骨折风险与载荷与强度的比率有关，而不是仅与骨强度有关）。准确预测骨折风险的第四个障碍是，骨组织力学特性的变化是由年龄或疾病引起的，骨组织中胶原蛋白、非胶原蛋白或骨骼含水量的变化是x射线无法检测到的。由于软组织变化在x射线检测中是不可见的，因此存在与年龄和更年期相关的组织材料特性（骨质量）变化，这些变化是不可见的，不被理解的，并且不可预测地增加了骨折的风险。

DESCRIPTION (provided by applicant): Age-related bone fracture is only partially explained by the reduction in bone mass that universally occurs with aging. The failure to predict fracture comes in part from a) the loss of geometrical information when projection x-ray methods are used to measure bone mass, b) ignorance of sufficiently detailed information about the failure properties of bone, and also c) ignorance of detailed in vivo loads on bones (Fracture risk is related to the ratio of load to strength, rather than to bone strength alone). A fourth barrier to accurately predicting fracture risk is that changes in bone tissue mechanical properties caused by age or disease related changes in the collagen, non-collagenous proteins or water content of bone are not detectable to xray methods. As a result of the invisibility of soft tissue changes to x-ray detection, there are age and menopause related changes in tissue material properties (in bone quality) that are invisible, not understood and that unpredictably increase bone fracture risk. Our data support the novel working hypotheses: 1) The viscoelastic properties of bone affect the fracture toughness and apparent strength of bone tissue, 2) The viscoelastic properties of ovine bone degrade after ovariectomy, causing a decrease in the strength and fracture toughness of bone tissue for rates of loading associated with falls. The main goal of the proposed work is to determine the onset time of viscoelastic property degradation and whether cortical bone can recover normal viscoelastic and strength properties with estrogen replacement.