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Grasp Force Assistance via Throttle-based Wrist Angle Control on a Robotic Hand Orthosis for C6-C7 Spinal Cord Injury

Joaquin Palacios, Alexandra Deli-Ivanov, Ava Chen, Lauren Winterbottom, Dawn M. Nilsen, Joel Stein, Matei Ciocarlie

TL;DR

The paper addresses the challenge of restoring hand function after C6-C7 spinal cord injury, where tenodesis yields limited grasp force and fatigue during prolonged use. It introduces MyHand-SCI, a wrist-angle controlled exotendon-powered orthosis that provides active grasp force via Throttle-based Wrist Angle (TWA) control, enabling users to modulate or hold grasp with moderate wrist extension. In a pilot study with a single participant, TWA improved Grasp and Release Test (GRT) performance and increased maximum grasp force while preserving the ability to modulate force, demonstrating intuitive ipsilateral control. The work lays the groundwork for broader testing and refinement of wearable assistive devices for SCI, with potential to reduce fatigue and enhance daily task performance.

Abstract

Individuals with hand paralysis resulting from C6-C7 spinal cord injuries frequently rely on tenodesis for grasping. However, tenodesis generates limited grasping force and demands constant exertion to maintain a grasp, leading to fatigue and sometimes pain. We introduce the MyHand-SCI, a wearable robot that provides grasping assistance through motorized exotendons. Our user-driven device enables independent, ipsilateral operation via a novel Throttle-based Wrist Angle control method, which allows users to maintain grasps without continued wrist extension. A pilot case study with a person with C6 spinal cord injury shows an improvement in functional grasping and grasping force, as well as a preserved ability to modulate grasping force while using our device, thus improving their ability to manipulate everyday objects. This research is a step towards developing effective and intuitive wearable assistive devices for individuals with spinal cord injury.

Grasp Force Assistance via Throttle-based Wrist Angle Control on a Robotic Hand Orthosis for C6-C7 Spinal Cord Injury

TL;DR

The paper addresses the challenge of restoring hand function after C6-C7 spinal cord injury, where tenodesis yields limited grasp force and fatigue during prolonged use. It introduces MyHand-SCI, a wrist-angle controlled exotendon-powered orthosis that provides active grasp force via Throttle-based Wrist Angle (TWA) control, enabling users to modulate or hold grasp with moderate wrist extension. In a pilot study with a single participant, TWA improved Grasp and Release Test (GRT) performance and increased maximum grasp force while preserving the ability to modulate force, demonstrating intuitive ipsilateral control. The work lays the groundwork for broader testing and refinement of wearable assistive devices for SCI, with potential to reduce fatigue and enhance daily task performance.

Abstract

Individuals with hand paralysis resulting from C6-C7 spinal cord injuries frequently rely on tenodesis for grasping. However, tenodesis generates limited grasping force and demands constant exertion to maintain a grasp, leading to fatigue and sometimes pain. We introduce the MyHand-SCI, a wearable robot that provides grasping assistance through motorized exotendons. Our user-driven device enables independent, ipsilateral operation via a novel Throttle-based Wrist Angle control method, which allows users to maintain grasps without continued wrist extension. A pilot case study with a person with C6 spinal cord injury shows an improvement in functional grasping and grasping force, as well as a preserved ability to modulate grasping force while using our device, thus improving their ability to manipulate everyday objects. This research is a step towards developing effective and intuitive wearable assistive devices for individuals with spinal cord injury.
Paper Structure (14 sections, 8 figures, 1 table)

This paper contains 14 sections, 8 figures, 1 table.

Table of Contents

  1. Introduction
  2. Related Work
  3. MyHand-SCI Assistive Device Design
  4. Throttle-based Wrist Angle Control
  5. Experiments
  6. Functional Performance Test
  7. Maximum Grasping Force Test
  8. Grasping Force Modulation Test
  9. Results
  10. Functional Performance
  11. Maximum Grasping Force
  12. Grasp Force Modulation
  13. Discussion
  14. Conclusion

Figures (8)

  • Figure 1: MyHand-SCI is a robot hand orthosis that is controlled via a Throttle-based Wrist Angle (TWA) control method.
  • Figure 2: Diagram of MyHand-SCI assistive device with labeled components.
  • Figure 3: Bioinspired tendon routing. Left: Simplified diagram with anatomical annular ligaments (tendon pulleys). Middle: Device diagram with anatomical analogues. Right: Device palmar side.
  • Figure 4: Experimental Protocol.
  • Figure 5: Instrumented object for measuring grasping force.
  • ...and 3 more figures