Time-Varying Material Properties of the Intervertebral Disc and the Influence on Spine Joint Mechanics

大约80%的人在生活中的某个时候会受到腰痛的影响。腰部是受伤最频繁的身体区域，平均补偿成本最高，导致的全球残疾比其他任何疾病都要多。有证据表明，下腰痛的主要原因是与日常活动和工业任务有关的机械暴露。虽然举起重物的任务通常与腰痛有关，但长时间站立或坐着等无害的久坐任务也与腰痛有关。然而，对于这些久坐的、看似无害的任务是如何导致腰部受伤的，人们几乎一无所知。 我的研究计划的总体方向是调查时变的低负荷暴露如何启动和加剧关节机械性能的改变，从而深入了解这些下背部损伤的途径。将调查由于慢性暴露而导致的健康脊柱结构(如椎间盘)的损伤开始和发展的原因。腰间盘的机械损伤被认为是高达50%的慢性下腰痛病例的原因。对健康、无损伤的个人在进行久坐不动的工作时对腰部的需求进行的研究将与组织水平的调查相结合，以评估脊柱组织的时间依赖反应和由此产生的损伤潜力。对关节性能和与机械负荷相关的损伤机制的联系的深入了解对于损伤预防至关重要，因为椎间盘中的生物修复机制比损伤过程慢，部分原因是该结构缺乏血液供应。一旦椎间盘损伤的第一阶段发生，脊髓组织自我修复的能力很容易被损伤恶化所超过。 这项研究的结果将提供与时间相关的组织材料特性，这些特性目前无法获得，并且是理解和模拟腰椎间盘和腰部损伤的限制因素。最终，将累积或慢性暴露与潜在疼痛产生联系起来，将是开发评估每日负荷和设定阈值限制或暴露标准以防止久坐任务伤害的方法的强大和新颖的基础贡献。这项工作将提供有关腰部潜在的健康组织反应的知识，为制定涉及坐姿到站立部件的职业工作站的使用指南奠定基础。

Low back pain affects approximately 80% of the population at some point in their life. The low back is the most frequently injured body area, has the highest average compensation costs, and results in more global disability than any other condition. Evidence suggests that the primary cause of low back pain is through mechanical exposure associated with everyday activities and industrial tasks. While tasks involving heavy lifting are often linked with low back pain, innocuous sedentary tasks such as prolonged standing or sitting have also been associated with low back pain. However, there is little understanding of how these sedentary, and seemingly benign tasks can result in injuries to the low back. The overall direction of my research program is to investigate how time varying exposure to low level loading initiates and exacerbates altered joint mechanical performance lending insight to these low back injury pathways. The causes of injury initiation and progression in the structures of the healthy spine (e.g. the intervertebral disc) due to chronic exposure will be investigated. Mechanical injuries to the intervertebral disc are thought to be responsible for up to 50% of chronic low back pain cases. Studies examining the demands on the low back of healthy, injury free individuals when performing sedentary tasks representing sitting and standing office computer or light assembly work will be combined with investigations at the tissue level to assess time-dependent responses of spinal tissues and the resulting injury potential. A solid understanding of the joint performance and links to injury mechanisms associated with mechanical loading is critical for injury prevention, as the biological repair mechanisms in the intervertebral disc are slower than the injury process, in part due to the lack of blood supply to this structure. The ability of the spinal tissues to repair themselves can easily be outpaced by injury deterioration once the first stage of an injury to the intervertebral disc has occurred. The outcomes from this research will provide time-dependent tissue material properties that are currently unavailable and are a limiting factor in the understanding and modeling of the intervertebral disc and low back injuries. Ultimately, the linking of cumulative or chronic exposure with potential pain generation would be a powerful and novel fundamental contribution in developing methods to assess daily loading and set threshold limits or exposure standards to prevent injuries for sedentary tasks. This work will provide knowledge of the underlying healthy tissue response in the low back, laying a foundation to develop usage guidelines for occupational workstations involving sit to stand components.