微重力环境对人体腰椎间盘力学响应影响的量化研究

The incidence of lumbar intervertebral disc (IVD) herniation and low back pain in astronauts during and/or after spaceflight is several times higher than that of the general population on earth. It has been hypothesized that swelling of the lumbar IVD in microgravity environment is the mechanism underlying such health issues in astronauts. However, due to the lack of effective methods to evaluate the swelling and mechanical responses of human lumbar IVD in microgravity environment, it is challenging to predict disc health risks or to develop protective countermeasures. There is an urgent need for such a method for effectively evaluating the impact of microgravity on the health of human IVD. Therefore, the goal of this project is to develop a computational method to quantitatively investigate the effects of microgravity on lumbar IVD swelling and biomechanical responses (including deformation, stress and strain distribution, mechanical damage, etc.) at different postures. First, a musculoskeletal dynamic model of human lumbar spine which includes swelling of the IVD will be developed to quantify the mechanical loading on the IVD at different postures in microgravity environment; then the biomechanical responses (mainly deformation, stress and strain distribution, mechanical damage, etc.) and their characteristics of the lumbar IVD under different mechanical loading condition corresponding to each of the posture will be quantitatively investigated with a biomechanical finite element model; finally, the health state of the IVD will be evaluated based on these mechanical response characteristics quantified in the second step. This project will help to understand the mechanism of lumbar IVD herniation and low back pain in the microgravity environment, and could serve as a theoretical basis for designing protective countermeasures. In addition, the computational model developed in this project will be a valuable tool to study other IVD diseases related to mechanical loading.

针对微重力环境下宇航员腰椎间盘突出与腰部疼痛发病率是普通人数倍的现象，目前还缺少有效的腰椎间盘在微重力环境中受力与膨胀状态以及力学响应的评估模型，无法实现宇航员腰椎疾病的预测与防护，急需一套腰椎间盘微重力环境下损伤的有效评估方法。本课题从生物力学仿真模型出发，首先建立一个能够有效描述腰椎间盘膨胀状态的新腰椎骨肌动力学模型, 研究微重力环境下航天环境宇航员特色运动姿态下腰椎间盘的受力状态。进而利用腰椎间盘生物力学有限元模型考察易发力学响应（主要有形变、应力应变分布、力学破坏等）及其特征，根据力学响应的核心参数及特征建立能够反映微重力对腰椎间盘健康影响的量化评估方案，最终达到对宇航员微重力环境下腰椎疾病的预测与评估目的。本课题研究结果将有助于宇航员腰椎间盘突出和腰部疼痛的发生机理研究，为研发相应保护装置提供理论依据，对腰椎疾病发生发展的生物力学深入研究提供了一套极具价值的理论工具。

本研究围绕微重力环境中航天员腰椎间盘突出和腰部疼痛高发生率的机理开展研究，重点解决两大问题：1、如何精准的获取微重力环境下腰椎间盘受力及膨胀状态；2、如何量化微重力对腰椎间盘生物力学响应的影响。本研究建立并验证了包含有腰椎间盘膨胀力学性能的新腰椎骨肌动力学模型。利用该模型量化分析了微重力环境中腰椎各组织在不同运动姿态下的力学响应，发现微重力环境导致腰椎各组织力学荷载变化明显，椎间盘上的荷载和肌力显著减小，椎间盘膨胀变化明显，高度和体积，以及韧带力均增大，且与实验数据较一致。量化分析了微重力环境导致的肌肉萎缩对腰椎各组织的力学荷载的改变；发现肌肉萎缩在多数日常活动中会增大椎间盘上的荷载。耦合了腰椎骨肌动力学模型和腰椎间盘生物力学有限元模型，量化了微重力环境对腰椎间盘内力-电-生化信号的影响以及对椎间盘内钙化沉积的影响；发现微重力下椎间盘内力学信号减小，椎间盘内营养物质浓度（如葡萄糖、氧气）和离子浓度（钠离子、氯离子，钙离子）减小，且蛋白多糖的合成速度减小。本研究对保障航天员长期微重力环境中的健康防护、保障航天员返回重力环境后的适应和生活能力、以及发展大众健康促进技术都具有重要科学意义。