Time-lapsed microstructural imaging of bone failure behavior
Time-lapsed microstructural imaging of bone failure behavior
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DOI：
10.1016/s0021-9290(03)00254-9
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发表时间：
2004-01-01
影响因子：
2.4
通讯作者：
Müller, R
中科院分区：
文献类型：
--
作者：
Nazarian, A;Müller, R
轴骨和附件骨中的许多骨骼在日常活动过程中会受到重复的载荷。如果该载荷具有足够的大小或持续时间，则可能导致骨组织的破坏。直到最近，对这些裂缝的结构分析一直局限于二维剖面。由于这种方法固有的破坏性，对骨折进展的动态评估是不可能的。利用阶梯式微压缩和延时微计算机层析成像技术开发了一种图像引导技术来分析结构破坏。这项技术首次实现了在微观水平上直接三维可视化和量化骨折的起始和进展，并将骨小梁的整体破坏特性与单个小梁的破坏特性联系起来。本项目的目标是首先设计和制作一种新型的微机械测试系统，由微压缩装置和材料测试和数据采集系统组成；第二，验证测试系统是否能够基于图像引导的失效分析对松质骨试件进行分步测试。由于骨骼的速率依赖性，应力松弛是逐步测试方法中的一个令人担忧的因素。为了解决这些问题，在相同的总应变范围和测试条件下，将分步测试方法的结果与传统连续测试(被认为是分步压缩力学测试的金标准)获得的结果进行了比较。这是使用具有高度重复性和均匀结构特性的多孔铝合金样品以及来自单个鲸鱼脊椎的骨小梁样品进行的。分别以2%、4%、8%、12%、16%和20%的应变间隔，对5个泡沫铝柱体和小梁鲸骨按0%~20%应变顺序压缩成像。对于泡沫铝和鲸骨标本，连续和逐步方法获得的力学性能没有显著差异(P&gT；0.05)。这两种测试方法产生了非常相似的应力-应变曲线，弹性和塑性区域几乎相同，覆盖了鲸骨和泡沫铝试件的标准误差条。通过对两种测试方法的应力数据进行回归分析，进一步证实了这一点(鲸骨和泡沫铝试件的r(2)=0.98)。断裂起始和发展的动画显示，破坏总是发生在局部带中，结构的其余区域基本上不受结构类型的影响。综上所述，我们发现分步微压缩是一种有效的图像引导失效评估(IGFA)方法，与经典的连续测试相比具有更高的精度和准确度。我们期待即将到来的人类椎骨IGFA研究结果能提高我们对密度、形态和载荷因素在脊柱自发性骨折病因中的相对重要性的理解。最终，这种更好的理解可能会导致更成功的预防年龄相关性疲劳性骨折的方法。(C)2003爱思唯尔有限公司。保留所有权利。
Many bones within the axial and appendicular skeleton are subjected to repetitive loading during the course of ordinary daily activities. If this loading is of sufficient magnitude or duration, failure of the bone tissue may result. Until recently the structural analysis of these fractures has been limited to two-dimensional sections. Due to the inherent destructiveness of this method, dynamic assessment of fracture progression has not been possible. An image-guided technique to analyze structural failure has been developed utilizing step-wise micro-compression in combination with time-lapsed micro-computed tomographic imaging. This technique allows, for the first time, direct three-dimensional visualization and quantification of fracture initiation and progression on the microscopic level and relates the global failure properties of trabecular bone to those of the individual trabeculae. The goals of this project were first to design and fabricate a novel micro-mechanical testing system, composed of a micro-compression device and a material testing and data acquisition system; and second, to validate the testing system to perform step-wise testing of trabecular bone specimens based on image-guided failure analysis. Due to the rate dependant properties of bone, stress relaxation was a concerning factor with respect to the step-wise testing method. In order to address these concerns, the results of the step-wise testing method were compared to those obtained from a conventional continuous test (considered to be the gold standard for the step-wise compressive mechanical testing) over the same total strain range and testing conditions. This was performed using porous aluminum alloy samples with highly reproducible and homogenous structural properties as well as trabecular bone samples from a single whale vertebra. Five cylinders from aluminum foam and trabecular whale bone each were compressed and imaged in a stepwise fashion from 0% to 20% strain at intervals of 2%, 4%, 8%, 12%, 16% and 20%. Mechanical properties obtained from the continuous and step-wise methods were not significantly different for both aluminum foam and whale bone specimens (P > 0.05). Both testing methods yielded very similar stress-strain graphs with almost identical elastic and plastic regions with overlaying standard error bars for both whale bone and aluminum foam specimens. This was further concurred by performing regression analyses between the stress data from both testing methods (r(2) = 0.98 for whale bone and aluminum foam specimens). Animations of fracture initiation and progression revealed that failure always occurred in local bands with the remaining regions of the structure largely unaffected independent of structure type. In conclusion, we found step-wise micro-compression to be a valid approach for image-guided failure assessment (IGFA) with high precision and accuracy as compared to classical continuous testing. We expect findings from upcoming studies of IGFA of human vertebral bone to improve our understanding of the relative importance of densitometric, morphological, and loading factors in the etiology of spontaneous fractures of the spine. Eventually, this improved understanding may lead to more successful approaches to the prevention of age-related fatigue fractures. (C) 2003 Elsevier Ltd. All rights reserved.