A neuroprosthesis for control of seated balance after spinal cord injury

Journal of NeuroEngineering and Rehabilitation, 2015 · DOI: 10.1186/1743-0003-12-8 · Published: January 21, 2015

Spinal Cord Injury Rehabilitation Biomedical

Simple Explanation

Individuals with spinal cord injury often desire to maintain a stable trunk while seated, which is crucial for daily activities. Functional neuromuscular stimulation (FNS) can restore function to paralyzed muscles by applying low-level currents to the nerves. A feedback control system was designed to maintain seated balance under external disturbances. The system uses a sensor to measure trunk tilt and activates hip and trunk extensor muscles via an implanted neuroprosthesis. Preliminary tests show that the controller can maintain trunk stability against perturbations. This indicates that trunk control with FNS is a promising intervention for individuals with SCI.

Study Duration

Not specified

Participants

Five individuals with paraplegia at different thoracic and cervical levels

Evidence Level

Level 4; Case Series

Key Findings

1
The controller could maintain trunk stability in the sagittal plane for perturbations up to 45% of body weight and for flexion thresholds as low as 0.7.
2
The mean settling time, or the time it took for the trunk to return to a stable position, varied across subjects from 0.5 to 2.0 seconds.
3
The mean response time of the feedback control system, or the time it took for the system to react to a disturbance, varied from 393 to 536 ms.

Research Summary

This study explores the potential of using Functional Neuromuscular Stimulation (FNS) to maintain seated balance in individuals with spinal cord injury (SCI). A feedback control system was designed to activate hip and trunk extensor muscles in response to external perturbations. The system was tested on five subjects with thoracic and cervical level SCI, using an implanted neuroprosthesis. The controller's effectiveness was evaluated based on its ability to maintain trunk stability against external forces, with varying perturbation magnitudes and flexion thresholds. Results indicate that the controller could maintain trunk stability for perturbations up to 45% of body weight. The findings suggest that FNS-based trunk control is a promising intervention for individuals with SCI, potentially improving their ability to perform daily activities.

Practical Implications

Enhanced Daily Living

The neuroprosthesis can enable individuals with SCI to maintain a stable trunk, facilitating activities like working, wheelchair propulsion, and driving.

Reduced Reliance on Restraints

The system reduces the need for restraining devices, increasing the user's workspace and freedom of movement.

Improved Rehabilitation Strategies

The findings support the development of FNS-based interventions for trunk control, offering a promising approach to rehabilitation for individuals with SCI.

Study Limitations

1
The muscle recruitment curves were assumed to be linear, which may not accurately reflect real muscle behavior.
2
Only motion in the sagittal plane was studied, limiting the system's ability to handle more complex, three-dimensional movements.
3
The control system primarily prevented trunk flexion, with extension movements limited by the chair's backrest, indicating a unidirectional control approach.

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