Kishimoto Hideaki
Dept. of Orthopedic Surgery, Nojima Hospital, Japan.
Clin Calcium. 2016 Jan;26(1):107-15.
Bone strength depends on its structural and material properties. Structural properties are determined by the size and shape of bone and also the microarchitecture. Material properties are determined by mineral crystallinity, collagen structure and microdamage in bone. The strength of bone is adapted to the needs of physical activities by biologic mechanisms, bone modeling and remodeling. The deterioration of bone strength in postmenopausal women is characterized by a trabecular bone deficit with poor trabecular connectivity and followed by a cortical bone deficit with trabeculation of endocortical bone and intracortical porosity due to accelerated bone remodeling. In high turnover osteoporosis antiresorptive therapy is effective in preventing the structural deficit and in increasing the stiffness and the toughness(bone strength)by increasing the mean degree of mineralization of bone tissue through the prolongation of secondary mineralization. But the long-term use of strong antiresorber, i.e. bisphosphonate or denosumab, would result in highly mineralized bone and disturbed repair of microcracks by inhibition of bone remodeling. Intermittent use or discontinuation of strong antiresorber after about 3-5 years of administration could be recommended to avoid the deterioration of bone strength.
骨强度取决于其结构和材料特性。结构特性由骨的大小、形状以及微观结构决定。材料特性由矿物质结晶度、胶原结构和骨内微损伤决定。骨强度通过生物机制、骨塑形和重塑来适应身体活动的需求。绝经后女性骨强度的下降表现为小梁骨缺乏，小梁连接性差，随后是皮质骨缺乏，由于骨重塑加速，出现骨内膜骨小梁化和皮质内孔隙。在高转换型骨质疏松症中，抗吸收治疗通过延长二次矿化增加骨组织矿化平均程度，从而有效预防结构缺陷并增加硬度和韧性（骨强度）。但是长期使用强效抗吸收剂，即双膦酸盐或地诺单抗，会导致骨高度矿化，并通过抑制骨重塑干扰微裂纹修复。建议在给药约3 - 5年后间歇性使用或停用强效抗吸收剂，以避免骨强度恶化。
