Noninvasive measurement of intradiscal strains under dynamic loading

项目摘要 脊柱由椎间和椎体的重复单元组成。该光盘是一个 具有独特亚成分的复杂组织，包括明胶髓核(NP)，它是 周围是纤维环(AF)。房颤环状撕裂伤导致退行性改变 或突出，其中NP物质从椎间盘中挤出并撞击脊神经。不幸的是， 相对较少的研究测量了加载过程中的盘内变形，这使得很难 辨别应力如何在整个椎板上分布，以及应力分布的变化可能如何导致 组织损伤。 PI博士格雷斯·奥康奈尔使用的非侵入性成像和纹理相关技术已被用于 使用磁共振成像跟踪完整的人腰椎间盘内的组织移位。不过，这个 由于图像采集时间较长(~20)，该方法仅限于评估静态间盘机械性能 分钟)，不代表生理动态负荷(例如，行走、弯曲等)的时间范围。 克雷格·戈尔根博士(Co-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空间组织变形(即4D 变形)。已经收集了初步数据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，该提案的目标是集成先进的高分辨率 超声成像和纹理相关技术定量测量腰椎间盘内应变分布 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 结合了奥康奈尔和戈尔根实验室开发的技术。我们将衡量 健康完整的椎间盘在动态压缩过程中的内部AF应变。椎间盘内的菌株将被用于 验证能够描述粘弹性(时间相关)行为的有限元模型。在AIM 2，我们将评估糖胺多聚糖的酶消化组织降解的效果和 动态压缩过程中环状裂缝对房颤应变分布的影响。在整个提案中， 牛盘将用于开发和验证这项技术。然后，健康到中度退化 人体盘将被收集，以验证该技术在人体盘上的工作。 这一提议项目的成功完成将改变评估椎间盘内应变的方法 通过扩展以前在超声波和生物力学方面的进展。此外，一个经过验证的数学模型 该模型将为更复杂的动力加载研究和新NP的效果评估提供参考 通过提高我们对椎间盘损伤的认识，对房颤力学的治疗策略。

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.