Impact of Global and Regional Sagittal Malalignment on Cervical Spine Mechanics

描述（由申请人提供）： 目的：颈椎的生理矢状面排列，包括保持水平凝视的能力，对于维持日常生活活动中的功能至关重要。因此，由于颈部疼痛和神经功能缺损的致残症状，颈椎矢状位排列不良与残疾和与健康相关的生活质量评分差有关。本研究的目的是建立矢状面对线不良的影像学或临床测量与颈椎病理力学的客观测量之间的联系。假设：我们研究的长期目标是了解颈椎病相关症状颈部疼痛，肌肉疲劳和神经功能缺损的机制，以改善治疗原理。我们的中心假设是，在存在颈椎矢状位对线不良的情况下，为了保持水平凝视所必需的颈椎节段的补偿性重新排列将：（1）增加对后部肌肉的力需求，以保持头颈姿势平衡，并导致椎间盘和小关节的负荷增加;（2）对椎间孔和椎管空间产生不利影响。该假设是基于我们的初步研究，使用一种新的实验室模型的颈椎矢状面不平衡，允许评估颈椎姿势和动力学反应的独立变量的影响。具体目标：（1）对于矢状面排列不良的自变量的每种组合，测量每个颈椎的补偿性角度和平移重新定位，以保持水平凝视，以及保持头颈姿势平衡所需的力和力矩。(2)使用目标1中收集的基于CT的腰椎特定模型和运动学数据，分析实验模拟矢状面对线不良对椎间孔和椎管空间的影响。(3)使用基于CT的样本特定有限元模型（FEM）以及目标1中量化的运动学和动力学边界条件，分析模拟矢状面对线不良对颈椎骨和软组织应力的影响。研究计划：我们将结合使用（1）人类尸体颈椎标本的实验研究，（2）基于CT的标本特定运动学模型，和（3）基于CT的标本特定有限元模型，以实现我们的目标。55个新鲜的人类尸体颈椎标本（枕骨-T1）的实验将模拟各种临床相关的矢状面排列不良。实验测量的量，即，补偿椎骨运动，以及标本两端的运动学和动力学边界条件，将作为特定于腰椎的运动学和有限元模型的输入，以评估每个矢状面对线不良对椎管和椎间孔尺寸和小关节负荷的影响。这三个研究部分将共同根据以下结果变量定义颈椎力学：动力学：小关节和椎间盘中的肌肉负荷和应力，与肌肉疲劳、椎间盘和小关节退变和颈部疼痛有关;几何学：椎间孔和椎管空间，与神经功能恶化有关。统计分析：将对55个样本中的每一个样本进行定义矢状面对线不良的四个独立变量的不同组合的测试，为评估主要变量及其相互作用的影响提供足够的（>80%）功效。将使用重复测量ANOVA分析完整脊柱和不同模拟融合病例的结局变量的离散值。将进行多变量回归分析，以评估自变量在影响结局方面的相对重要性，并得出因变量和自变量相关的预测方程。重要性：本研究的结果将提供一个合理的基础，使客观的今天的主观范式治疗颈椎不平衡。结果将立即有利于所有管理颈部疼痛患者的医疗保健团队成员，无论是保守的（医生，物理治疗师，脊椎按摩师），还是那些进行侵入性干预的人（外科医生）。

DESCRIPTION (provided by applicant): Purpose: A physiologic sagittal alignment of the cervical spine, including the ability to maintain level gaze, is essential to maintaining functionality during activities of daily living. Consequenty, cervical sagittal malalignment has been linked to disability and poor health-related quality of lif scores due to disabling symptoms of neck pain and neurological deficit. The goal of this study is to establish the link between radiographic or clinical measures of sagittal malalignment and objective measures of cervical pathomechanics. Hypotheses: The long-term goal of our research is to understand the mechanisms responsible for cervical malalignment-related symptoms of neck pain, muscle fatigue, and neurological deficit so as to improve treatment rationale. Our central hypothesis is that in the presence of cervical sagittal malalignment, the compensatory realignment of cervical segments that is necessary in order to maintain horizontal gaze will: (1) increase force demands on posterior muscles to maintain the head-neck posture in equilibrium and cause increased loading of disc & facet joints; and (2) adversely affect the foraminal and canal spaces. The hypothesis is based on our preliminary studies using a novel laboratory model of cervical sagittal imbalance that allows assessment of the effects of the independent variables on cervical spine postural and kinetic responses. Specific Aims: (1) For each combination of the independent variables of sagittal malalignment, measure the compensatory angular and translational repositioning of each cervical vertebra such that horizontal gaze is maintained, and the forces and moments that are needed to maintain the head-neck posture in equilibrium. (2) Analyze the effects of experimentally simulated sagittal malalignments on foraminal and canal spaces using CT-based specimen-specific models and kinematic data collected in Aim 1. (3) Analyze effects of simulated sagittal malalignments on stresses in bony and soft tissues of the cervical spine using CT-based specimen- specific finite element models (FEM), and the kinematic and kinetic boundary conditions quantified in Aim 1. Research Plan: We will use a combination of (1) experimental studies on human cadaveric cervical spine specimens, (2) CT-based specimen-specific kinematic models, and (3) CT-based specimen-specific finite element models, to achieve our goals. Experiments on 55 fresh human cadaveric cervical spine specimens (occiput-T1) will simulate a variety of clinically relevant sagittal malalignments. Experimentally measured quantities, namely, compensatory vertebral motions, and kinematic and kinetic boundary conditions at the ends of the specimen, will serve as inputs to the specimen-specific kinematic and FE models to assess the effects of each sagittal malalignment on canal & foramen dimensions and facet loading. The three study- components together will define cervical spine mechanics in terms of the following outcome variables: Kinetic: loading of muscles and stresses in facets & discs, with implications to muscle fatigue, disc & facet degeneration, and neck pain; and Geometric: foraminal and canal spaces, with implications to neurologic deterioration. Statistical Analysis: Each of the 55 specimens will be tested for different combinations of the four independent variables that define sagittal malalignment, giving adequate (>80%) power for assessing the effects of the main variables and their interactions. Discrete values of the outcome variables for the intact spine and also for the different cases of simulated fusions will be analyzed using the repeated measures ANOVA. Multivariate regression analyses will be performed to assess the relative importance of independent variables in influencing the outcome and arrive at predictive equations relating dependent & independent variables. Significance: The results of this study will provide a rational basis for bringing objectivity to the present day subjective paradigms for treatment of cervical imbalance. Results will be of immediate benefit to all health care team-members who manage patients with neck pain, whether conservatively (physicians, physical therapists, chiropractors), or those who perform invasive interventions (surgeons).