A Closed-Loop Self-Righting Controller for Seated Balance in the Coronal and Diagonal Planes Following Spinal Cord Injury

Med Eng Phys, 2020 · DOI: 10.1016/j.medengphy.2020.10.010 · Published: December 1, 2020

Simple Explanation

This study explores using functional neuromuscular stimulation (FNS) to help people with spinal cord injuries (SCI) maintain their balance while sitting. The system uses a sensor to detect when someone is leaning and then stimulates specific muscles to help them return to an upright position. The controller was tested for restoring upright sitting from forward, lateral or diagonal leaning without a chest strap.

Study Duration

Not specified

Participants

Five individuals with mid-thoracic or higher SCI

Evidence Level

Not specified

Key Findings

1
The control system successfully restored upright sitting from forward, lateral or diagonal leaning without a chest strap.
2
Response and recovery times varied widely among subjects in the coronal and diagonal planes.
3
The percent maximum deviation from erect was of the order of 40% or less for 9 out of 10 cases in the coronal plane and 5 out of 6 cases in diagonal directions.

Research Summary

The study designed and deployed a real-time self-righting feedback controller for restoration of trunk posture in the coronal and diagonal planes in individuals with various levels of SCI using FNS of their paralyzed muscles. The results showed that the self-righting feedback controller successfully restored posture to erect in all the subjects from trunk angles that were impossible to restore with baseline stimulation alone automatically and without use of the arms. The ability to restore the trunk to erect from fairly large angles of lean indicates the future potential for users of seated balance neuroprostheses to deploy their trunk to larger regions around their wheelchairs, thus enabling them to undertake ADLs in ways that would be impossible without a feedback control system.

Practical Implications

Improved Seated Stability

The system can improve seated stability for individuals with SCI, ensuring safety during ADLs such as driving and wheelchair propulsion.

Hands-Free Functionality

The controller has the potential to allow users to maintain seated balance hands-free, expanding their workspace and ability to perform ADLs.

Reduced Need for Restraints

The system may obviate the need for restrictive chest belts and straps, increasing comfort and freedom of movement.

Study Limitations

1
All the synergistic muscles for a given plane were recruited to act simultaneously.
2
Trunk axial rotation was ignored in the analyses, which focused primarily on lateral bending and forward flexion/extension.
3
Only a small subset of possible leaning postures was examined in the current study, so future work should concentrate on generalizing the system for any arbitrary direction.

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