Department of Biomedical Engineering, The University of Melbourne, Melbourne, VIC, Australia.
Department of Mechanical and Product Design Engineering, Swinburne University of Technology, Melbourne, VIC, Australia.
J Mech Behav Biomed Mater. 2021 Jun;118:104457. doi: 10.1016/j.jmbbm.2021.104457. Epub 2021 Mar 16.
Underbody blast attacks of military vehicles by improvised explosives have resulted in high incidence of lumbar spine fractures below the thorocolumbar junction in military combatants. Fracture risk curves related to vertical loading at individual lumbar spinal levels can be used to assess the protective ability of new injury mitigation equipment. The objectives of this study were to derive fracture risk curves for the lumbar spine under high rate compression and identify how specimen-specific attributes and lumbar spinal level may influence fracture risk. In this study, we tested a sample of three-vertebra specimens encompassing all spinal levels between T12 to S1 in high-rate axial compression. Each specimen was tested with a non-injurious load, followed by a compressive force sufficient to induce vertebral body fracture. During testing, bone fracture was identified using measurements from acoustic emission sensors and changes in load cell readings. Following testing, the fractures were assessed using computed tomographic (CT) imaging. The CT images showed isolated fractures of trabecular bone, or fractures involving both cortical and trabecular bone. Results from the compressive force measurements in conjunction with a survival analysis demonstrated that the compressive force corresponding to fracture increased inferiorly as a function of lumbar spinal level. The axial rigidity (EA) measured at the mid-plane of the centre vertebra or the volumetric bone mineral density (vBMD) of the vertebral body trabecular bone most greatly influenced fracture risk. By including these covariates in the fracture risk curves, no other variables significantly affected fracture risk, including the lumbar spinal level. The fracture risk curves presented in this study may be used to assess the risk of injury at individual lumbar vertebra when exposed to dynamic axial compression.
军用车辆在底部受到简易爆炸装置的爆炸冲击，导致军事战斗人员胸腰椎交界处以下的腰椎骨折发生率很高。与个体腰椎水平的垂直加载相关的骨折风险曲线可用于评估新型损伤缓解设备的保护能力。本研究的目的是得出在高速压缩下腰椎的骨折风险曲线，并确定标本特性和腰椎水平如何影响骨折风险。在这项研究中，我们在高速轴向压缩下测试了涵盖 T12 至 S1 之间所有脊柱水平的三个椎体标本的样本。每个标本均进行了无损伤载荷测试，然后进行了足以引起椎体骨折的压缩力测试。在测试过程中，通过声发射传感器的测量和加载单元读数的变化来识别骨骨折。测试后，使用计算机断层扫描 (CT) 成像评估骨折情况。CT 图像显示了骨小梁的孤立性骨折，或涉及皮质骨和骨小梁的骨折。结合抗压强度测量的结果和生存分析表明，骨折对应的抗压强度随腰椎水平的降低而增加。中心椎体中平面测量的轴向刚度 (EA) 或椎体骨小梁的体积骨矿物质密度 (vBMD) 对骨折风险的影响最大。通过在骨折风险曲线中包含这些协变量，包括腰椎水平在内的其他变量不再显著影响骨折风险。本研究中提出的骨折风险曲线可用于评估个体腰椎在暴露于动态轴向压缩时受伤的风险。
