An Intuitive, Bidirectional, and Adaptive Functional Electrical Stimulation System for Hand Rehabilitation.

Area of Science:

• Neuroscience
• Rehabilitation Engineering
• Biomedical Engineering

Background:

• Neuromotor injuries like stroke and spinal cord injury (SCI) significantly impair hand function, reducing patient independence and quality of life.
• Functional electrical stimulation (FES) therapy shows promise for recovery, but its clinical use is limited by complex setup and lack of specialized systems.
• Existing FES systems require lengthy setup times, hindering widespread adoption in hand therapy settings.

Purpose of the Study:

• To develop and validate a closed-loop, bidirectional FES system tailored for grasping rehabilitation.
• To utilize an adaptive local model of muscle activation dynamics for precise grip force control.
• To assess the system's performance, ease of use, and adaptability to muscle fatigue and patient-specific conditions.

Main Methods:

• A novel closed-loop, bidirectional FES system was designed, employing a first-order adaptive local model to control FES amplitude for grip force modulation.
• The system's control accuracy was compared against an autotuned PID controller using 12 healthy participants.
• System validation included testing with a C5 spinal cord injury participant and assessing performance during fatiguing contractions and setup time by untrained users.

Main Results:

• The adaptive controller demonstrated superior accuracy in grip force control compared to the autotuned PID controller in healthy participants.
• The FES system effectively controlled grasping in a participant with C5 spinal cord injury exhibiting upper motor neuron spasticity.
• The controller successfully adapted to muscle fatigue during prolonged use, with model parameters correlating strongly with fatigue, enabling real-time fatigue measurement.
• An untrained user could set up the FES system in under 5 minutes.

Conclusions:

• Adaptive models offer significant benefits for FES control, leading to more accurate and responsive grasping rehabilitation.
• The developed FES system is user-friendly, adaptable to fatigue, and effective for patients with neuromotor injuries, including SCI.
• This work provides a foundation for designing more effective and clinically translatable FES systems for hand therapy.