Valero-Cuevas F J, Zajac F E, Burgar C G
Rehabilitation Research and Development Center, Veterans Affairs Palo Alto Health Care System, CA 94304-1200, USA.
J Biomech. 1998 Aug;31(8):693-703. doi: 10.1016/s0021-9290(98)00082-7.
Are fingertip forces produced by subject-independent patterns of muscle excitation? If so, understanding the mechanical basis underlying these muscle coordination strategies would greatly assist surgeons in evaluating options for restoring grasping. With the finger in neutral ad- abduction and flexed 45 degrees at the MCP and PIP, and 10 degrees at DIP joints, eight subjects attempted to produce maximal voluntary forces in four orthogonal directions perpendicular to the distal phalanx (palmar, dorsal, lateral and medial) and in one direction collinear with it (distal). Forces were directed within 4.7 +/- 2.2 degrees (mean +/- S.D.) of target and their magnitudes clustered into three distinct levels (p < 0.05; post hoc pairwise RMANOVA). Palmar (27.9 +/- 4.1 N), distal (24.3 +/- 8.3 N) and medial (22.9 +/- 7.8 N) forces were highest, lateral (14.7 +/- 4.8 N) was intermediate, and dorsal (7.5 +/- 1.5 N) was lowest. Normalized fine-wire EMGs from all seven muscles revealed distinct muscle excitation groups for palmar, dorsal and distal forces (p < 0.05; post hoc pairwise RMANOVA). Palmar force used flexors, extensors and dorsal interosseous; dorsal force used all muscles; distal force used all muscles except for extensors; medial and lateral forces used all muscles including significant co-excitation of interossei. The excitation strategies predicted to achieve maximal force by a 3-D computer model (four pinjoints, inextensible tendons, extensor mechanism and isometric force models for all seven muscles) reproduced the observed use of extensors and absence of palmar interosseous to produce palmar force (to regulate net joint flexion torques), the absence of extensors for distal force, and the use of intrinsics (strong MCP flexors) for dorsal force. The model could not predict the interossei co-excitation seen for medial and lateral forces, which may be a strategy to prevent MCP joint damage. The model predicts distal force to be most sensitive to dorsal interosseous strength, and palmar and distal forces to be very sensitive to MCP and PIP flexor moment arms, and dorsal force to be sensitive to the moment arm of and the tension allocation to the PIP extensor tendon of the extensor mechanism.
指尖力是由与个体无关的肌肉兴奋模式产生的吗？如果是这样，了解这些肌肉协调策略背后的力学基础将极大地帮助外科医生评估恢复抓握功能的选项。手指处于中立位外展，掌指关节（MCP）和近端指间关节（PIP）屈曲45度，远端指间关节（DIP）屈曲10度时，8名受试者试图在垂直于远节指骨的四个正交方向（掌侧、背侧、外侧和内侧）以及与远节指骨共线的一个方向（远端）上产生最大自主力。力的方向与目标方向的偏差在4.7±2.2度（平均值±标准差）以内，其大小聚为三个不同水平（p<0.05；事后两两重复测量方差分析）。掌侧力（27.9±4.1N）、远端力（24.3±8.3N）和内侧力（22.9±7.8N）最高，外侧力（14.7±4.8N）居中，背侧力（7.5±1.5N）最低。来自所有七块肌肉的归一化细钢丝肌电图显示，掌侧、背侧和远端力存在不同的肌肉兴奋组（p<0.05；事后两两重复测量方差分析）。掌侧力使用屈肌、伸肌和背侧骨间肌；背侧力使用所有肌肉；远端力使用除伸肌外的所有肌肉；内侧力和外侧力使用所有肌肉，包括骨间肌的显著共同兴奋。一个三维计算机模型（四个销关节、不可伸展的肌腱、伸肌机制和所有七块肌肉的等长力模型）预测的实现最大力的兴奋策略再现了观察到的使用伸肌和不使用掌侧骨间肌来产生掌侧力（以调节净关节屈曲扭矩）、远端力不使用伸肌以及背侧力使用固有肌（强大的掌指关节屈肌）的情况。该模型无法预测内侧力和外侧力中观察到的骨间肌共同兴奋，这可能是一种防止掌指关节损伤的策略。该模型预测远端力对背侧骨间肌力量最敏感，掌侧力和远端力对掌指关节和近端指间关节屈肌力矩臂非常敏感，背侧力对伸肌机制的近端指间关节伸肌腱的力矩臂和张力分配敏感。
