Biomechanical Mechanisms of Facet Whiplash Injury & Pain

描述（改编自申请人的摘要）：颈部扭伤及其相关综合征仍然是最常见的和使人衰弱的非致命性损伤之一。小关节已经被确定为在挥鞭样损伤过程中颈部运动可能会发生亚失效机械损伤。此外，其神经生理解剖结构表明其能够在极端负荷下产生疼痛。然而，很少有人知道这些局部关节力学的影响，如在挥鞭样损伤中经历的张力和压缩，疼痛症状或信号机制。 拟议研究的目的：本申请的长期目标是定义导致持续性疼痛症状的动态小关节负荷的机械条件，并将行为结果与脊髓中的细胞反应性相关联。机械阈值将为制定指南以减少普通人群中疼痛性挥鞭样损伤的发生率提供基础。他们还将指导对汽车和乘员使用习惯的修改，以减少这些伤害的风险。 研究方法：在拟议的研究计划中，将整合生物力学，行为测试仪器和生化分析，将疼痛途径与颈椎小关节的机械负荷联系起来。使用本实验室开发的一种新的微机械装置，研究人员将对小关节施加受控的牵引和压缩，并研究大鼠分级持续性疼痛反应的发生。假设：1）在挥鞭样损伤模拟中观察到的动态小关节牵引模仿将产生持续的行为超敏反应; 2）产生囊夹的小关节压缩足以引发持续的疼痛;以及3）对于高于产生疼痛的阈值的损伤状况，将产生并维持脊髓中的伤害感受和神经胶质激活的细胞反应性应答。 对预防的影响：通过实现研究的特定目标，研究人员将直接将小关节的初始机械条件与CNS中的疼痛通路联系起来。反过来，他们将定义由于动态关节运动引起的持续疼痛的病因，从而为未来的设计干预和行为修改提供发展和建议，以防止这些损伤。 相关性：颈部扭伤是一个巨大的公共卫生问题，也是车辆乘员的常见伤害，每年都会带来惊人的社会和经济负担。这项研究计划将定义颈部疼痛性小关节损伤的机械阈值，并研究生物力学风险因素（如加载方向）对加剧疼痛的影响。这些损伤和症状的生理相关性也被表征为指导未来颈痛预防和治疗的发展。

DESCRIPTION (adapted from applicant's abstract): Whiplash and its associated syndromes continue to be ranked among the most common and debilitating nonfatal injuries. The facet joint has been identified as having the potential to undergo subfailure mechanical injury for motions the neck experiences during whiplash. Also, its neurophysiologic anatomy suggests its ability to generate pain for extreme loading. However, little is known about the effects of these local joint mechanics, such as tension and compression that are experienced in whiplash, on pain symptoms or signaling mechanisms. Purpose of Proposed Research: The lonq-term objective of this application is to define the mechanical conditions for dynamic facet joint loading that cause persistent pain symptoms, and to correlate behavioral outcomes with cellular reactivity in the spinal cord. Mechanical thresholds will provide the foundation to develop guidelines to reduce the incidence of painful whiplash injuries in the general population. They will also guide modifications to the automobile and occupant-use habits to reduce risks for these injuries. Methods: In the proposed research plan, there will be integration of biomechanics, behavioral test instruments and biochemical assays to link pain pathways with mechanical loading of the cervical facet joint. Using a new micromechanical device developed in this laboratory, the investigators will apply controlled distraction(s) and compression(s) of the facet joint and study the onset of a graded persistent pain response in the rat. It is hypothesized that: 1) dynamic facet joint distraction mimicking that observed in whiplash simulations will produce persistent behavioral hypersensitivity; 2) facet joint compression producing capsule pinch is sufficient to initiate persistent pain; and 3) for injury conditions above the threshold for producing pain, cellular reactivity responses of nociception and glial activation in the spinal cord will be produced and sustained. Implications for Prevention: By accomplishing the specific aims of the research, the investigators will directly link the initial mechanical conditions of the facet joint to pain pathways in the CNS. In turn, they will define the etiology for persistent pain due to dynamic joint motions, leading to the development and recommendations for future design interventions and behavioral modifications to prevent these injuries. Relevance: Whiplash is a tremendous public health problem and a common injury for vehicle occupants, with staggering annual societal and financial burdens. This research proposal will define the mechanical thresholds for painful facet injuries in the neck and investigate the effects of biomechanical risk factors, such as loading direction, on exacerbating pain. Physiologic correlates of these injuries and symptoms are also characterized for guiding future development of preventions and treatments for neck pain.