Optimization of bone growth and remodeling in response to loading in tapered mammalian limbs
Optimization of bone growth and remodeling in response to loading in tapered mammalian limbs
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DOI：
10.1242/jeb.00514
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发表时间：
2003-09-01
影响因子：
2.8
通讯作者：
Crompton, AW
中科院分区：
文献类型：
--
作者：
Lieberman, DE;Pearson, OM;Crompton, AW
骨骼是如何通过形状和结构的变化来动态响应机械载荷的，人们对此知之甚少，特别是关于骨骼之间的变化。在结构上，皮质骨在体内主要通过调节两个过程--建模和哈弗斯重塑--来适应其机械环境。建模，这里定义为添加新的骨，可以通过随着生长改变骨的形状或大小来响应机械刺激而发生。哈弗斯重塑被认为是修复微裂纹或阻止微裂纹扩展的一种适应。在这里，我们研究了绵羊肢体的皮质骨是否调节骨膜建模和哈弗斯重塑，以优化后肢中干相对于质量的力量，以响应不同发育阶段的适度运动水平。用组织形态计量学的方法比较了运动和久坐治疗组幼年、亚成年和幼年绵羊骨膜生长和哈弗氏重塑的速度。还收集了幼年绵羊的胫骨和趾骨中干的活体应变数据。结果表明，肢体骨骼最初会根据与在不同位置增加质量相关的不同功率需求来优化对负荷的反应。在青少年中，运动导致近端中轴的骨膜重建率较高，而远端中轴的哈弗斯重建率较高。因此，远端元件中轴承受较高的应力，并可能具有较低的安全系数。随着动物年龄的增长，骨膜重建率下降，哈弗斯重建率上升，但适度的机械负荷对这两个过程都没有明显的刺激作用。
How bones respond dynamically to mechanical loading through changes in shape and structure is poorly understood, particularly with respect to variations between bones. Structurally, cortical bones adapt in vivo to their mechanical environments primarily by modulating two processes, modeling and Haversian remodeling. Modeling, defined here as the addition of new bone, may occur in response to mechanical stimuli by altering bone shape or size through growth. Haversian remodeling is thought to be an adaptation to repair microcracks or prevent microcrack propagation. Here, we examine whether cortical bone in sheep limbs modulates periosteal modeling and Haversian remodeling to optimize strength relative to mass in hind-limb midshafts in response to moderate levels of exercise at different growth stages. Histomorphometry was used to compare rates of periosteal growth and Haversian remodeling in exercised and sedentary treatment groups of juvenile, subadult and young adult sheep. In vivo strain data were also collected for the tibia and metatarsal midshafts of juvenile sheep. The results suggest that limb bones initially optimize responses to loading according to the varying power requirements associated with adding mass at different locations. In juveniles, exercise induces higher rates of periosteal modeling in proximal midshafts and higher rates of Haversian remodeling in distal midshafts. Consequently, distal element midshafts experience higher strains and, presumably, have lower safety factors. As animals age, periosteal modeling rates decline and Haversian remodeling rates increase, but moderate levels of mechanical loading stimulate neither process significantly.