Yamaguchi G T, Zajac F E
Rehabilitation R&D Center, Veterans Affairs Medical Center, Palo Alto 94304.
IEEE Trans Biomed Eng. 1990 Sep;37(9):886-902. doi: 10.1109/10.58599.
Functional neuromuscular stimulation (FNS) of paralyzed muscles has enabled spinal-cord-injured patients to regain a semblance of lower-extremity control, for example to ambulate while relying heavily on the use of walkers. Given the limitations of FNS, specifically low muscle strengths, high rates of fatigue, and a limited ability to modulate muscle excitations, it remains unclear, however, whether FNS can be developed as a practical means to control the lower extremity musculature to restore aesthetic, unsupported gait to paraplegics. A computer simulation of FNS-assisted bipedal gait shows that it is difficult, but possible to attain undisturbed, level gait at normal speeds provided the electrically-stimulated ankle plantarflexors exhibit either near-normal strengths or are augmented by an orthosis, and at least seven muscle-groups in each leg are stimulated. A combination of dynamic programming and an open-loop, trial-and-error adjustment process was used to find a suboptimal set of discretely-varying muscle stimulation patterns needed for a 3-D, 8 degree-of-freedom dynamic model to sustain a step. An ankle-foot orthosis was found to be especially useful, as it helped to stabilize the stance leg and simplified the task of controlling the foot during swing. It is believed that the process of simulating natural gait with this model will serve to highlight difficulties to be expected during laboratory and clinical trials.
对瘫痪肌肉进行功能性神经肌肉电刺激（FNS），已使脊髓损伤患者能够重新获得一定程度的下肢控制能力，比如在严重依赖助行器的情况下行走。然而，鉴于FNS存在局限性，特别是肌肉力量较低、疲劳率高以及调节肌肉兴奋的能力有限，FNS是否能够发展成为一种切实可行的方法，用以控制下肢肌肉组织，从而为截瘫患者恢复美观、无需支撑的步态，目前仍不明确。一项关于FNS辅助双足步态的计算机模拟显示，若电刺激的踝跖屈肌具有接近正常的力量，或通过矫形器增强力量，并且每条腿至少有七个肌肉群受到刺激，那么以正常速度实现平稳、不受干扰的步态虽有难度但仍有可能。采用动态规划与开环试错调整过程相结合的方法，为一个三维、八自由度的动态模型寻找维持一步所需的一组次优离散变化肌肉刺激模式。结果发现踝足矫形器特别有用，因为它有助于稳定支撑腿，并简化了摆动期控制足部的任务。人们认为，用该模型模拟自然步态的过程将有助于凸显在实验室和临床试验中可能遇到的困难。
