Clinical Evaluation of a Tongue-Controlled Wrist Abduction-Adduction Assistance in a 6-DoF Upper-Limb Exoskeleton for Individuals with ALS and SCI

2026-04-22

AI Summary

This study evaluates the clinical utility of wrist abduction–adduction degrees of freedom in the tongue-controlled six-degree-of-freedom upper-limb exoskeleton EXOTIC2 for individuals with amyotrophic lateral sclerosis (ALS) and spinal cord injury (SCI) during activities of daily living such as drinking and scratching. By comparing conditions with and without this wrist motion enabled, and integrating kinematic analysis, task success rates, and user-reported usability questionnaires, the work provides the first validation of its effectiveness within a tongue-operated exoskeletal system. Results demonstrate that enabling wrist abduction–adduction reduced task spillage from 77.8% to 22.2% and placement failure from 66.7% to 16.7%, without compromising user comfort and with significantly improved subjective performance ratings, underscoring the clinical importance of functional range of motion over maximal joint excursion.

Technology Category

Intelligent Robots: ManipulationHumans and AI: AI for AccessibilityApplication Domains: Mobility, Driving & Flight

Application Category

Responsible Web: Machine-in-the-loop, human agency and autonomyUser Modeling, Personalization and Recommendation: Metrics for user behavior and evaluating successSearch and Retrieval-Augmented AI: Multilingual and cross-lingual Web search

Abstract

Upper-limb exoskeletons (ULEs) have the potential to restore functional independence in individuals with severe motor impairments; however, the clinical relevance of wrist degrees of freedom (DoF), particularly abduction-adduction (Ab-Ad), remains insufficiently evaluated. This study investigates the functional and user-perceived impact of wrist Ab-Ad assistance during two activities of daily living (ADLs). Wrist Ab-Ad assistance in a tongue-controlled 6-DoF ULE, EXOTIC2, was evaluated in a within-subject study involving one individual with amyotrophic lateral sclerosis and five individuals with spinal cord injury. Participants performed drinking and scratch stick leveling tasks with EXOTIC2 under two conditions: with and without wrist Ab-Ad assistance. Outcome measure included task success, task completion time, kinematic measures, and a usability questionnaire capturing comfort, functional perception, and acceptance. Enabling wrist Ab-Ad improved task success rates across both ADLs, with consistent reductions in spillage (from 77.8% spillages to 22.2%) and failed placements (from 66.7% to 16.7%). Participants utilized task-specific subsets of the available wrist range of motion, indicating that effective control within functional ranges was more critical than maximal joint excursion. Questionnaire responses indicated no increase in discomfort with the additional DoF and reflected perceived improvements in task performance. In conclusion, wrist Ab-Ad assistance enhances functional task performance in assistive exoskeleton use without compromising user comfort. However, its effectiveness depends on task context, control usability, and individual user strategies. This study provides clinically relevant, user-centered evidence supporting the inclusion of wrist Ab-Ad in ULEs, emphasizing the importance of balancing functional capability with usability in assistive device design.

Problem

• wrist abduction-adduction
• upper-limb exoskeleton
• activities of daily living
• motor impairment
• functional assistance

Innovation

• wrist abduction-adduction
• tongue-controlled exoskeleton
• upper-limb exoskeleton
• activities of daily living
• user-centered design