Dept of Oncology and Metabolism and INSIGNEO Institute for in silico Medicine, The University of Sheffield, Sheffield, United Kingdom.
Dept of Industrial Engineering, Alma Mater Studiorum, Università di Bologna, Bologna, Italy.
PLoS One. 2021 Jun 1;16(6):e0251873. doi: 10.1371/journal.pone.0251873. eCollection 2021.
The spine is the first site for incidence of bone metastasis. Thus, the vertebrae have a high potential risk of being weakened by metastatic tissues. The evaluation of strength of the bone affected by the presence of metastases is fundamental to assess the fracture risk. This work proposes a robust method to evaluate the variations of strain distributions due to artificial lesions within the vertebral body, based on in situ mechanical testing and digital volume correlation. Five porcine vertebrae were tested in compression up to 6500N inside a micro computed tomography scanner. For each specimen, images were acquired before and after the application of the load, before and after the introduction of the artificial lesions. Principal strains were computed within the bone by means of digital volume correlation (DVC). All intact specimens showed a consistent strain distribution, with peak minimum principal strain in the range -1.8% to -0.7% in the middle of the vertebra, demonstrating the robustness of the method. Similar distributions of strains were found for the intact vertebrae in the different regions. The artificial lesion generally doubled the strain in the middle portion of the specimen, probably due to stress concentrations close to the defect. In conclusion, a robust method to evaluate the redistribution of the strain due to artificial lesions within the vertebral body was developed and will be used in the future to improve current clinical assessment of fracture risk in metastatic spines.
脊柱是骨转移的首发部位。因此，椎体有被转移性组织削弱的高风险。评估受转移影响的骨的强度对于评估骨折风险至关重要。本工作提出了一种基于原位力学测试和数字体视学相关技术来评估人工损伤导致的椎体应变分布变化的稳健方法。对五具猪的椎体进行了在微 CT 扫描仪内压缩至 6500N 的测试。对于每个标本，在施加负载前后、在引入人工损伤前后都采集了图像。通过数字体视学相关（DVC）在骨内计算主应变。所有完整的标本都表现出一致的应变分布，在椎体中部的最小主应变峰值范围在-1.8%到-0.7%之间，证明了该方法的稳健性。在不同区域的完整椎体中都发现了相似的应变分布。人工损伤通常会使标本中部的应变增加一倍，这可能是由于靠近缺陷处的应力集中所致。总之，开发了一种稳健的方法来评估人工损伤导致的椎体内部应变的重新分布，该方法将用于改进当前对转移性脊柱骨折风险的临床评估。
