Material Properties of the Intervertebral Disc

椎间盘是人体脊柱中相邻椎体之间的主要关节。椎间盘退行性疾病是导致成人疼痛和残疾的主要原因；在需要手术的情况下，用人工材料代替病变椎间盘正在成为治疗的选择。与此同时，脊柱损伤在与高加速度有关的事件中很常见，例如跌倒、运动损伤、道路交通事故和暴力行为；这些损伤通常与长期残疾有关。据世界卫生组织预测，到2030年，仅道路交通事故造成的伤害就将成为疾病负担的第三大原因。对脊柱损伤的相关机制缺乏全面的了解，特别是高能创伤。北约官方报告承认当前损伤标准的局限性和脊柱损伤风险曲线的缺乏；这些标准和曲线将使我们能够适当地评估车辆和保护系统。同样，人体测量测试装置（或假人）在预测人体脊柱在负荷下的反应时的类人反应也是值得怀疑的。因此，正在使用不合标准的技术制定加强保护和改进防护设备的战略。有限元（FE）建模是一种对人体伤害、植入物和保护系统的结构力学的计算机模拟，是重要的工程工具，它使我们能够理解涉及伤害事件的机制，并以经济有效的方式开发新的和改进的评估标准、技术、材料和设计。随着计算能力的日益丰富，以优化设计为目的的有限元建模作为昂贵和劳动密集型实验的替代方案，在工业上是一个明确的战略方向。然而，影响人体反应有限元模型预测能力的一个关键参数是与人体组织的物质行为相关的输入数据的质量。这类数据，特别是与损伤相关的加载率数据，对于大多数人体组织来说是稀缺的；这绝对是椎间盘的情况。因此，该项目的目的是量化人体椎间盘在生理和损伤载荷率下的材料行为。目的是为植入物设计提供信息，并提高人体损伤有限元模型的准确性，以提高其模拟脊柱在载荷下反应的能力。

The intervertebral disc is the primary articulation between adjacent vertebral bodies in the human spine. Degenerative disc disease is the leading cause of pain and disability in the adult; replacing the diseased disc with an artificial material is becoming the treatment of choice in cases that require surgery. At the same time, injuries to the spinal column are common in incidents that are associated with high accelerations, such as falls, sports injuries, road traffic accidents, and acts of violence; these injuries are often associated with long term disability. Injury induced by road-traffic accidents alone is predicted to become the third leading cause for burden of disease by 2030 according to the World Health Organization. A comprehensive understanding of the mechanisms associated with injury to the spine is lacking, especially in high-energy trauma. Official NATO reports acknowledge the limitations of current injury criteria and lack of injury risk curves for the spine; these criteria and curves would allow us to evaluate vehicles and protection systems appropriately. Similarly, the human-like response of anthropometric test devices (or dummies) in predicting the response of the human spine under load is questionable. As a result, strategies to enhance protection and to improve protective equipment are being developed using sub-standard technologies. Finite element (FE) modelling - a type of computer simulation of the mechanics of structures - of human injury, of implants and of protective systems are important engineering tools that allow us to understand the mechanisms involved in an injurious event and to develop new and improved evaluation criteria, techniques, materials and designs in a cost-efficient manner. As computational power becomes more abundant, FE modelling for optimal design is a clear strategic direction in industry as an alternative to expensive and labour intensive experiments. A critical parameter, however, that influences the predictive ability of FE models of human response is the quality of the input data that are associated with the material behaviour of human tissue. Such data, particularly at loading rates relevant to injury, are sparse for most human tissues; this is definitely the case for the intervertebral disc. The aim of this project, therefore, is to quantify the material behaviour of the human intervertebral disc across physiological and injurious loading rates. The intention is to inform implant design and to increase the accuracy of FE models of human injury in order to improve their ability to simulate the response of the spine under load.