Hand Research Laboratory, Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, USA.
J Neuroeng Rehabil. 2013 Mar 2;10:28. doi: 10.1186/1743-0003-10-28.
Precision grip by the thumb and index finger is vulnerable to sensorimotor deficits. Traditional biomechanical parameters offer limited insight into the dynamical coordination between digits during precision grip. In this study, the thumb and index finger were viewed as "coupled systems", and a cross recurrence quantification analysis (CRQA) was used to examine the changes of interdigit dynamics and synchronization caused by peripheral median nerve block.
Seven subjects performed a precision grip by holding an instrumented handle before and after median nerve block at the wrist. The forces and the torques at each digit-handle interface were recorded with two six-component transducers. For CRQA, the percentage of recurrence rate (%RR), percentage of determinism (%DET), longest diagonal line (Lmax) and percentage of laminarity (%LAM) were computed for the force, torque and center of pressure (COP) signals. Phase synchronization of the thumb and index finger was examined based on the τ-recurrence rate. Paired t-tests and Wilcoxon signed-rank tests were used for statistical comparisons. The twin-surrogate hypothesis test was used to examine phase synchronization.
Nerve block led to significant increases (p < 0.05) for %DET, Lmax and %LAM in all components of force, torque, and COP. Only the normal force met the conditions of phase synchronization for all successfully completed pre- and post-block grasping trials. The probability of synchronization with larger time lags (τ > 0.1 s) increased after nerve block. The percentage of trials that the thumb led the index finger increased from 52% (pre-block) to 86% (post-block).
Nerve block caused more deterministic structures in force, torque and COP when the thumb interacted with the index finger. A compensatory mechanism may be responsible for this change. Phase synchronization between the opposite normal forces exerted by the thumb and index finger would be an essential dynamical principle for a precision grip. The nerve block resulted in an increased interdigit phase delay and increased probability that the thumb leads the index finger. The CRQA provides an effective tool to examine interdigit coordination during precision grip and has the potential for clinical evaluation of hand dysfunction.
拇指和食指的精准握力容易受到感觉运动功能障碍的影响。传统的生物力学参数对精准握力中手指之间的动态协调性提供的信息有限。在这项研究中，拇指和食指被视为“耦合系统”，并使用交叉递归定量分析（CRQA）来检查周围正中神经阻滞引起的指间动力学和同步性的变化。
七名受试者在手腕正中神经阻滞前后，用仪器手柄进行精准握力。用两个六分量换能器记录每个指-手柄界面的力和扭矩。对于 CRQA，计算力、扭矩和压力中心（COP）信号的重现率（%RR）、确定性（%DET）、最长对角线（Lmax）和层流性（%LAM）。根据 τ-重现率检查拇指和食指的相位同步。使用配对 t 检验和 Wilcoxon 符号秩检验进行统计比较。双随机假设检验用于检验相位同步。
神经阻滞导致所有力、扭矩和 COP 分量的 %DET、Lmax 和 %LAM 显著增加（p<0.05）。只有正常力在所有成功完成的预阻滞和后阻滞抓握试验中都满足相位同步的条件。神经阻滞后，具有较大时间滞后（τ>0.1s）的同步概率增加。拇指领先食指的试验比例从 52%（预阻滞）增加到 86%（后阻滞）。
当拇指与食指相互作用时，神经阻滞导致力、扭矩和 COP 中出现更确定的结构。一种代偿机制可能是造成这种变化的原因。拇指和食指对向的正常力之间的相位同步将是精准握力的一个基本动力学原则。神经阻滞导致指间相位延迟增加，拇指领先食指的概率增加。CRQA 为检查精准握力中的指间协调性提供了一种有效的工具，并有可能用于手部功能障碍的临床评估。
