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陷的致残症状，颈椎矢状面排列不良与残疾和与健康相关的LIF评分质量差有关。本研究的目的是建立矢状位错位的放射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排列不良相关症状的机制，如颈部疼痛、肌肉疲劳和神经功能障碍，以改善治疗原理。我们的中心假设是，在存在颈椎矢状位错位的情况下，为了保持水平凝视而需要的颈椎节段的补偿性重排将：(1)增加对后部肌肉的力量需求，以维持头颈部姿势的平衡，并导致椎间盘和小关节负荷增加；以及(2)对孔隙和管腔产生不利影响。这一假说是基于我们使用一种新的颈椎矢状面失衡实验室模型进行的初步研究，该模型可以评估自变量对颈椎姿势和运动反应的影响。具体目标：(1)对于矢状位错位的每个自变量组合，测量每个颈椎的补偿角和平移重新定位，以保持水平凝视，以及维持头颈姿势平衡所需的力和力矩。(2)利用Aim 1中收集的基于CT的标本特异性模型和运动学数据，分析实验模拟的矢状排列错位对孔和椎管间隙的影响。(3)使用基于CT的标本特有的有限元模型分析模拟的矢状排列对颈椎骨骼和软组织中应力的影响，以及在Aim 1中量化的运动学和动力学边界条件。研究计划：我们将结合(1)人体身体颈椎标本的实验研究，(2)基于CT的标本特有的运动学模型和(3)基于CT的标本特有的有限元模型，来实现我们的目标。在55具新鲜的人身体颈椎标本(枕骨-T1)上的实验将模拟各种临床相关的矢状面错位。实验测量的量，即椎体的补偿性运动，以及标本末端的运动学和运动学边界条件，将作为标本特定运动学和有限元模型的输入，以评估每个矢状面对齐不良对管孔尺寸和小关节载荷的影响。这三个研究组成部分将根据以下结果变量共同定义颈椎力学：动力学：肌肉负荷和小关节和间盘的应力，与肌肉疲劳、椎间盘和小关节退变以及颈部疼痛有关；几何：孔隙和椎管间隙，与神经恶化有关。统计分析：55个样本中的每一个都将接受四个独立变量的不同组合测试，这四个独立变量定义矢状面排列不良，从而提供足够(80%)的力量来评估主要变量及其相互作用的影响。对于完整的脊柱和模拟融合的不同情况，结果变量的离散值将使用重复测量ANOVA进行分析。将进行多元回归分析，以评估自变量在影响结果中的相对重要性，并得出与因变量和自变量相关的预测方程。意义：这项研究的结果将为目前治疗颈椎不平衡的主观范式带来客观性提供合理的基础。结果将立即惠及所有医疗团队--管理颈部疼痛患者的成员，无论是保守的(内科医生、理疗师、脊椎按摩师)，还是那些实施侵入性干预的成员(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).