Control strategies in FNS systems for the upper extremities.

The condition of the paralyzed patient is described, regarding both the primary paralysis and the secondary physiological changes in the upper limb resulting in abilities and disabilities in upper limb function. Although the review relates mainly to spinal cord injuries at the C4, C5, and C6 levels, other conditions are noted such as hemiplegia. Activation of muscle by functional neuromuscular stimulation (FNS) is discussed. The biomechanics of the FNS-activated paralyzed upper limb is analyzed for activation by both implanted and by surface electrodes, and a review is presented of open-loop strategies for systems in clinical use. Closed-loop strategies applied to the upper extremity are reviewed for analog and digital systems, and regimes developed for specific functional activities are outlined. Finally, adaptive control strategies are surveyed.