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首页> 外文期刊>Journal of the mechanical behavior of biomedical materials >In silico re-foundation of strain-based healing assessment of fractures treated with an external fixator
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In silico re-foundation of strain-based healing assessment of fractures treated with an external fixator

机译：用外固定器处理的基于菌株的菌株愈合评估的硅重建

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In the last decades, the literature has demonstrated a renewed interest in finding quantitative and non-invasive techniques for the assessment of bone fractures, by replacing X-ray images. Many different approaches have been proposed from ultrasounds to vibrations. This study aims to numerically assess the foundation of a method firstly proposed in 70' years, based on strain gauges measurements on external fixators for fracture healing monitoring. The theoretical basis consists in the load transfer from the fixator to the bone caused by the callus stiffening during healing. The feasibility is questioned since the level of fixator strain and its variation in in vivo conditions should be high enough to be detectable by the sensors. A finite element model of a fractured tibia phantom treated with a monolateral external fixator was developed and validated experimentally. Then, this reference model was used to simulate bone healing and to investigate the sensitivity of virtual strain measurements to callus geometry and loading conditions. The analysis of load distribution among fixator components and their strain maps allowed to identify optimum strain gauges locations which resulted on the pins more distant from the callus, regardless of the simulated conditions. Even in the worst case of a very thin (3 mm) transverse callus in constrained compression conditions, the strain level (asymptotic to 100 mu epsilon/100 N) and its variation per week (-50 mu epsilon/100 N/wk) resulted measurable in the first healing phase, before plateau conditions occurring after about 6 weeks from fixation. A thicker callus causes higher strain levels and can significantly improve measurements, whilst the callus orientation and the loading conditions have a minor effect. However, in case of a free compression loading, also the rods could provide useful indications if sensorized. The results support the method applicability in in vivo conditions for the considered test case. Further in-vestigations will be addressed to evaluate the effect of the fixator structure and configuration as well as of patient specific healing timing on the method sensitivity.
机译：在过去的几十年里，文献表明，通过替代X射线图像，寻找定量和非侵入性的骨折评估技术重新引起了人们的兴趣。从超声波到振动，人们提出了许多不同的方法。本研究的目的是在70年内首次提出一种基于应变仪测量骨折愈合监测的外固定器的方法的基础。理论基础在于愈合过程中骨痂变硬导致的载荷从固定器转移到骨骼。这种可行性受到质疑，因为固定器应变水平及其在体内条件下的变化应足以被传感器检测到。建立了单侧外固定器治疗胫骨骨折的有限元模型，并进行了实验验证。然后，使用该参考模型模拟骨愈合，并研究虚拟应变测量对骨痂几何形状和加载条件的敏感性。通过分析固定器组件之间的载荷分布及其应变图，可以确定最佳应变计位置，无论模拟条件如何，这些位置都会导致销钉距离骨痂更远。即使在最糟糕的情况下，在有限的压缩条件下，非常薄（3 mm）的横向骨痂，应变水平（接近100με/100 N）及其每周变化（-50με/100 N/wk）在第一个愈合阶段可测量，在固定约6周后出现平台条件之前。较厚的愈伤组织会导致更高的应变水平，并能显著改善测量结果，而愈伤组织方向和加载条件的影响较小。然而，在自由压缩载荷的情况下，如果传感器化，杆也可以提供有用的指示。这些结果支持了所考虑的测试用例在体内条件下的方法适用性。进一步研究将评估固定器结构和配置以及患者特定愈合时间对方法敏感性的影响。

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