Noninvasive measurement of intradiscal strains under dynamic loading

项目摘要 脊柱由椎间盘和椎体的重复单元组成。该盘是 具有独特亚成分的复杂组织，包括凝胶状髓核（NP）， 被纤维环（AF）包围。通过瓣环撕裂损伤AF导致退行性变化 或脑疝，其中NP材料从椎间盘突出并撞击脊神经。不幸的是， 在加载过程中测量椎间盘内变形的研究相对较少， 辨别应力如何分布在整个椎间盘，以及应力分布的变化如何导致 组织损伤 PI博士Grace O'Connell使用的非侵入性成像和纹理相关技术已用于 使用磁共振成像跟踪完整的人类腰椎间盘内的组织位移。但这 由于图像采集时间较长（约20 分钟），不代表生理动态负荷的时间帧（例如，行走、弯曲等）。 博士克雷格Goergen（合作PI）拥有丰富的经验，使用高频超声成像跟踪三个- 心血管和肌肉骨骼组织随时间的三维组织变形（即，4d 变形）。初步数据已收集，以确定测量椎间盘内应变的可行性 在动态载荷条件下。因此，本提案的目标是集成先进的高分辨率 超声成像和纹理相关性来量化椎间盘中的椎间盘内应变分布 动态加载条件 在第一个目标中，我们将开发一个框架，用于测量和建模整个4D变形 通过结合O'Connell和Goergen实验室开发的技术来治疗椎间盘。我们将测量 健康完整椎间盘动态压缩过程中的内部AF应变。椎间盘内菌株将用于 验证能够描述粘弹性（时间相关）行为的有限元模型。在aim中 2，我们将通过酶消化糖胺聚糖和 动态压缩过程中环形裂隙对AF应变分布的影响。在整个提案中， 牛圆盘将用于开发和验证该技术。然后，健康到中度退化 将收集人类椎间盘以验证该技术对人类椎间盘的作用。 该项目的成功完成将改变评估椎间盘内应变的方法 通过扩展先前在超声波和生物力学方面的进步。此外，一个有效的数学 该模型对于研究更复杂的动力加载和评价新型NP的效果具有一定的参考价值 通过提高我们对椎间盘损伤的理解，制定AF力学的治疗策略。

Project Summary The spine is comprised of repeating units of intervertebral discs and vertebral bodies. The disc is a complex tissue with unique subcomponents including the gelatinous nucleus pulposus (NP), which is surrounded by the annulus fibrosus (AF). Injury of the AF through annular tears leads to degenerative changes or herniation, where NP material extrudes out of the disc and impinges on the spinal nerves. Unfortunately, there are relatively few studies that have measured intradiscal deformations during loading, making it difficult to discern how stresses are distributed throughout the disc, and how changes in stress distribution may lead to tissue damage. Noninvasive imaging and texture correlation techniques used by PI Dr. Grace O’Connell have been used to track tissue displacements within intact human lumbar discs using magnetic resonance imaging. However, this approach was limited to only assessing static disc mechanics due to long image acquisition times (~20 minutes), a timeframe that is not representative of physiological dynamic loading (e.g., walking, bending, etc.). Dr. Craig Goergen (Co-PI) has extensive experience using high frequency ultrasound imaging to track three- dimensional tissue deformations of cardiovascular and musculoskeletal tissues over time (i.e., 4D deformations). Preliminary data has been collected to determine feasibility of measuring intradiscal strains under dynamic loading conditions. Thus, the goal of this proposal is to integrate advanced high-resolution ultrasound imaging and texture correlation to quantify intradiscal strain profiles in the intervertebral disc under dynamic loading conditions. In the first aim, we will develop a framework for measuring and modeling 4D deformations throughout the intervertebral disc by combining techniques developed in O’Connell and Goergen’s labs. We will measure internal AF strains during dynamic compression of healthy intact discs. Intradiscal strains will be used to validate a finite element model that will be capable of describing viscoelastic (time-dependent) behavior. In Aim 2, we will evaluate the effect of tissue degradation through enzymatic digestion of glycosaminoglycans and the effect of annular fissures on AF strain distributions during dynamic compression. Throughout the proposal, bovine disc will be used to develop and validate the technique. Then, healthy to moderately degenerated human disc will be collected to validate the technique works with human discs. Successful completion of this proposal project will transform approaches for assessing intradiscal strains by extending previous advancements in ultrasound and biomechanics. Moreover, a validated mathematical model will be useful for the study of more complex dynamic loading and evaluating the effect of new NP treatment strategies on AF mechanics by improving our understanding of disc injury.