Agcaoglu Serife, Akkus Ozan
Weldon School of Biomedical Engineering, Purdue University, 206 South Martin Jischke Drive, West Lafayette, IN 47907, USA.
J Biomech Eng. 2013 Aug;135(8):81005. doi: 10.1115/1.4024134.
Stress fractures are frequently observed in physically active populations, and they are believed to be associated with microcrack accumulation. There are not many tools for real-time monitoring of microdamage formation during fatigue of bone, in vivo or in vitro. Acoustic emission (AE) based detection of stress waves resulting from microdamage formation is a promising method to assess the rate and energetics of microdamage formation during fatigue. The current study aims to assess the time history of the occurrence of AE events during fatigue loading of human tibial cortical bone and to determine the associations between AE variables (energy content of waves, number of AE waveforms, etc.), fatigue life, and bone ash content. Fatigue test specimens were prepared from the distal diaphysis of human tibial cortical bone (N = 32, 22 to 52 years old, male and female). The initiation of acoustic emissions was concomitant with the nonlinear increase in sample compliance and the cumulative number of AE events increased asymptotically in the prefailure period. The results demonstrated that AE method was able to predict the onset of failure by 95% of the fatigue life for the majority of the samples. The variation in the number of emissions until failure ranged from 6 to 1861 implying a large variation in crack activity between different samples. The results also revealed that microdamage evolution was a function of the level of tissue mineralization such that more mineralized bone matrix failed with fewer crack events with higher energy whereas less mineralized tissue generated more emissions with lower energy. In conclusion, acoustic emission based surveillance during fatigue of cortical bone demonstrates a large scatter, where some bones fail with substantial crack activity and a minority of samples fail without significant amount of crack formation.
应力性骨折在体育活动人群中很常见，人们认为它与微裂纹的积累有关。在体内或体外，用于实时监测骨骼疲劳过程中微损伤形成的工具并不多。基于声发射（AE）检测微损伤形成产生的应力波，是一种评估疲劳过程中微损伤形成速率和能量学的有前景的方法。本研究旨在评估人体胫骨皮质骨疲劳加载过程中声发射事件发生的时间历程，并确定声发射变量（波的能量含量、声发射波形数量等）、疲劳寿命和骨灰含量之间的关联。疲劳试验样本取自人体胫骨皮质骨的远端骨干（N = 32，年龄22至52岁，男女皆有）。声发射的起始与样本顺应性的非线性增加同时出现，并且在失效前阶段声发射事件的累积数量渐近增加。结果表明，对于大多数样本，声发射方法能够在疲劳寿命的95%时预测失效的开始。直至失效的发射数量变化范围为6至1861，这意味着不同样本之间的裂纹活动差异很大。结果还显示，微损伤的演变是组织矿化水平的函数，即矿化程度更高的骨基质在较少的裂纹事件下失效，能量更高，而矿化程度较低的组织产生更多能量较低的发射。总之，皮质骨疲劳过程中基于声发射的监测显示出很大的离散性，一些骨骼在大量裂纹活动的情况下失效，而少数样本在没有大量裂纹形成的情况下失效。
