Mechanistic Characterization of Shoulder Function and Tissue Loading

肩关节功能对人类活动至关重要。在现代社会中，肩部组织经历的负荷和情况往往会导致损伤，生活质量下降，生产力下降。超过一半的加拿大人在他们的一生中会有肩部损伤。拟议研究计划的指导目标是系统地改善肩关节组织机械暴露、失效容限及其相互作用的量化，以更好地了解健康肩关节功能及其对人类生活的影响。 肩膀和人类是复杂的、共生的机械系统。肩部令人难以置信的灵活性允许各种能力，但以低机械关节稳定性为代价。人群中的生物学变异性进一步使肩关节评价复杂化。我提出的研究将通过三个相互关联的目标来解决肩部力学中至关重要的基本不确定性。 目标1：表征多尺度群体变异性对组织暴露的影响-计算机模拟：将五个主要指标视为现有肩关节模型中的可变参数，以定义哪个指标对组织反应影响最大。这些因素包括：1）组织组成，2）盂肱稳定性，3）肩关节节律，4）节段运动学和5）任务要求。 目标二：量化肩部肌肉疲劳对运动学反应的影响-在体内：肩部必须在存在许多压力源的情况下发挥作用。肌肉疲劳是改变正常肩部力学的主要因素之一。我们将使用多维符号运动段表征，以确定实验疲劳进展。这些数据将用于改进概率模型的动态疲劳响应（目标1），并指导组织耐受性试验方案（目标3）。 目标三：定义组织对实际机械载荷的耐受性-体外：生理冈上肌腱载荷与肩部难以置信的姿势灵活性密不可分，这会导致未经测试的复杂肌腱变形。将使用能够施加复杂载荷分布的新型局灶性组织系统对样本进行测试，获得关于扭转、局灶性和纵向暴露联合影响的先进数据，以帮助阐明冈上肌腱失效机制（目标1）。 总之，肩关节力学-从骨运动到特定组织载荷和失效模式-将采用生物力学领域的综合尖端方法进行评估。数据驱动的概率模型将超过目前描述人类肩部力学的尝试，提供反映人类可变性的肩部行为描述。最终，这些对肩部功能的基本见解将为维持和开发上肢无与伦比的潜力提供指导。

Shoulder function is crucial for human activities. In the modern world, shoulder tissues experience loads and scenarios that often cause damage, decreases in quality of life, and reduced productivity. Over half of Canadians will have shoulder damage in their lifetimes. The guiding objective of the proposed research program is to systematically improve quantification of shoulder tissue mechanical exposures, failure tolerances, and their interactions to better understand healthy shoulder function and its implications for human life. Shoulders and humans are complex, symbiotic mechanical systems. The incredible flexibility of the shoulder allows diverse capabilities, but comes at the cost of low mechanical joint stability. Biological variability across the human population further complicates shoulder evaluation. My proposed research will resolve crucial fundamental uncertainties in shoulder mechanics through three linked objectives. Objective 1: Characterize the influence of multi-scale population variability on tissue exposures - in silico: Five major metrics will be treated as variable parameters within my existing shoulder model to define which metric(s) influence tissue response the most. These are: 1) tissue composition, 2) glenohumeral stability, 3) shoulder rhythm, 4) segmental kinematics, and 5) task demands. Objective 2: Quantify the effects of shoulder muscle fatigue on kinematic responses - in vivo: The shoulder must function in the presence of many stressors. Muscular fatigue is one of the primary factors that alters normal shoulder mechanics. We will use multi-dimensional symbolic motion segment characterization to identify experimental fatigue progression. The data will be used to improve the dynamic fatigue response of the probabilistic model (Obj. 1) and to guide tissue tolerance testing protocols (Obj. 3). Objective 3: Define tissue tolerances to realistic mechanical loads - in vitro: Physiological supraspinatus tendon loading is inseparable from the shoulder's incredible postural flexibility, which causes untested complex tendon deformation. Specimens will be tested with a novel focal tissue system capable of applying complex load profiles, yielding advanced data on the influences of combined torsional, focal, and longitudinal exposures to help clarify supraspinatus tendon failure mechanisms (Obj. 1). In summary, shoulder mechanics - from bone movement to specific tissue loads and failure modes - will be assessed with integrative, cutting edge approaches from across the field of biomechanics. The data-driven probabilistic model will exceed current attempts to describe human shoulder mechanics, providing descriptions of shoulder behavior that reflect human variability. Ultimately, these fundamental insights into shoulder function will provide guidance on methods to maintain and exploit the incomparable potential of our upper limbs.