Reflex Contributions to Joint Stability

描述(申请人提供)：为了探索关节神经对关节稳定性的潜在贡献，我们建议研究关节传入在促进人类膝关节内侧向稳定性中的作用，并试图在良好控制的环境中表征基于关节传入的反射的输入-输出特性。选择膝关节内翻/外翻(v/v)作为模型是有利的，因为肌肉本体感受器在这些方向上促进反射激活的可能性较小，从而允许更直接地检查韧带/被膜机械感受器效应的输入/输出特性。根据我们的初步研究，拉伸关节韧带的机械扰动在横跨膝关节的肌肉中产生反射反应，这些反射的组织是为了选择性地补偿内翻外翻的负荷。因此，我们假设关节传入介导的肌肉激活可以通过对人膝关节施加机械v/v负载来引发，并且反射强度将是角度扰动大小的递增函数。我们还提出，内侧肌肉对横向扰动表现出更大的反射反应，而外侧肌肉对内侧扰动表现出更大的反应。这种反射反应将显著增加膝关节在v/v方向的僵硬程度。最后，我们假设这些基于反射的激活模式的空间分布使膝关节对外翻(或内翻)负荷的抵抗最大化。将在72名受试者中确定膝关节周围肌肉介导的反射激活的定量测量。坡道外翻位置扰动将通过伺服马达应用于受试者膝部。[将通过使用线性伺服马达系统在位置扰动期间对脚底施加轴向力来模拟承载条件。轴向力将用于增加关节压缩，并将以受试者S体重的百分比表示。]扭矩和肌电活动将被记录和分析在主要的膝关节肌肉。为了定量研究反射作用的机制，我们将基于10名受试者的完整膝关节磁共振成像，建立受试者特定的髌股关节和胫股关节的三维模型。在该模型中，每个肌肉的激活将被表示为一个分布函数，其均值和标准差由目标1中从同一受试者获得的反射激活模式限定。我们将使用该模型使用蒙特卡罗模拟来估计随机股四头肌激活模式的可能分布，该随机股四头肌激活模式可以响应于外翻负荷而产生内翻力矩。然后将这些基于模型的内翻矩与使用实验性肌肉激活时由模型计算的内翻矩进行比较(来自Aim 1的数据)。准静态和动态反射僵硬将分别使用斜坡和伪随机二进制v/v位置扰动应用于9名受试者进行量化。关节刚度和阻尼系数将使用延迟线性模型进行估计。在静态神经学和力学状态下获得的基于机械感受器的膝关节反射的输入/输出特性的识别将为未来的研究奠定坚实的基础，该研究将探讨关节传入在功能任务中的贡献。我们认为膝关节关节周围组织中的拉伸感受器在促进关节内侧向稳定性方面发挥着重要作用，这将对训练如何提高关节整体稳定性产生重大影响。

DESCRIPTION (provided by applicant): To explore the potential contributions of joint innervation towards joint stability, we propose to study the role of joint afferents in promoting medio-lateral stability of the human knee joint and seek to characterize the input-output properties of joint afferents-based reflexes in a well-controlled environment. The choice of knee varus/valgus (v/v) as a model is advantageous because there is less likelihood that muscle proprioceptors will contribute to reflex activation in these directions, allowing more straight-forward examination of input/output properties of ligament/capsular mechanoreceptor effects. Based on our preliminary studies, mechanical perturbations that stretch joint ligaments produced reflex response in muscles traversing the knee joint, and that these reflexes were organized so as to compensate selectively for varus-valgus loading. Accordingly, we hypothesize that joint afferents mediated muscle activation can be elicited by the application of mechanical v/v loading to the human knee, and that the reflex intensity will be an increasing function of the angular perturbation size. We also propose that medial muscles will show a larger reflex response to lateral perturbation, and lateral muscles will show a larger response to medial perturbations. This reflex response will significantly increase knee joint stiffness in the v/v direction. Finally, we hypothesize that spatial distribution of these reflex-based activation patterns maximize resistance to the valgus (or varus) loading at the knee. Quantitative measures of periarticular mediated reflex activation of knee muscles will be determined in 72 subjects. A ramp valgus positional perturbation will be applied at the subject knee via a servomotor. [Load bearing conditions will be simulated by the application of an axial force to the sole of the foot during positional perturbation using a linear servomotor system. The axial force will be used to increase joint compression, and will be represented as a percent of the subject s body weight.] Torque and EMG activity will be recorded and analyzed in major knee muscles. To examine the mechanics of reflex action quantitatively, a three-dimensional subject-specific patello-femoral and tibio-femoral joint model will be constructed based on complete knee MRIs of a subset of 10 subjects. In the model, each muscle activation will be represented as a distribution function with a mean and standard deviation bounded by the reflex activation patterns obtained from the same subject in Aim 1. We will use Monte Carlo simulations with this model to obtain estimates of the likely distribution of random quadriceps activation patterns that can generate varus moment in response to an applied valgus load. These model-based varus moments are then compared to the varus moment computed by the model when experimental muscle activations are used (data from Aim 1). A quasistatic and dynamic reflex stiffness will be quantified using ramp and pseudo-random binary v/v positional perturbation applied to the knee in 9 subjects, respectively. Joint stiffness and damping coefficients will be estimated using delayed linear models. Identification of the input/output properties of the mechanoreceptor-based knee joint reflexes obtained under static neurological and mechanical states will serve as solid basis for future studies, which will investigate joint afferents contributions during a functional task. We believe that stretch receptors in periarticular tissues of the knee joint play a major role in promoting joint medial-lateral stability, which will potentially have a major impact on how training may improve overall joint stability.