A novel upper-limb tracking system in a virtual environment for stroke rehabilitation

Kuan Cha,Yan Li,Jinying Wang,Longbin Shen,Zhuoming Chen,Jinyi Long

doi:10.1186/s12984-021-00957-6

Abstract

BackgroundThe transfer of the behaviors of a human’s upper limbs to an avatar is widely used in the field of virtual reality rehabilitation. To perform the transfer, movement tracking technology is required. Traditionally, wearable tracking devices are used for tracking; however, these devices are expensive and cumbersome. Recently, non-wearable upper-limb tracking solutions have been proposed, which are less expensive and more comfortable. However, most products cannot track the upper limbs, including the arms and all the fingers at the same time, which limits the limb parts for tracking in a virtual environment and may lead to a limited rehabilitation effect.MethodsIn this paper, a novel virtual reality rehabilitation system (VRRS) was developed for upper-limb rehabilitation. The VRRS could track the motion of both upper limbs, integrate fine finger motion and the range of motion of the entire arm and map the motion to an avatar. To test the performance of VRRS, two experiments were designed. In the first experiment, we investigated the effect of VRRS on virtual body ownership, agency and location of the body and usability in 8 healthy participants by comparing it with a partial upper-limb tracking method based on a Leap Motion controller (LP) in the same virtual environments. In the second experiment, we examined the feasibility of VRRS in upper-limb rehabilitation with 27 stroke patients.ResultsVRRS improved the users’ senses of body ownership, agency, and location of the body. The users preferred using the VRRS to using the LP. In addition, we found that although the upper limb motor function of patients from all groups was improved, the difference between the FM scores tested on the first day and the last day of the experimental group was more significant than that of the control groups.ConclusionsA VRRS with motion tracking of the upper limbs and avatar control including the arms and all the fingers was developed. It resulted in an improved user experience of embodiment and effectively improved the effects of upper limb rehabilitation in stroke patients.Trial registrationThe study was registered at the First Affiliated Hospital of Jinan University Identifier: KY-2020–036; Date of registration: June 01, 2020.

Highlights

Stroke is a common health-care problem that results in obvious muscle weakness on one side of the body [1]
Five of eight subjects agreed that the upper-limb behaviors of the avatar were authentic, as if the virtual upper limbs were parts of their bodies
We showed that the virtual reality rehabilitation system (VRRS) could elicit higher feelings of body ownership, agency, location of the body and system usability, which supports the above hypothesis

Summary

Introduction

Stroke is a common health-care problem that results in obvious muscle weakness on one side of the body [1]. It is estimated that 50% to 75% of stroke patients have persistent impairment of the affected upper limb and must undergo repetitive physical training to recover their motor function [2]. Cha et al Journal of NeuroEngineering and Rehabilitation (2021) 18:166 use of virtual environments (VEs) as a tool is gradually becoming popular in the field because it offers richness of experience and is interesting to patients [3]. Bortone et al [4,5,6] found that the use of a virtual environment and wearable devices offers a viable alternative to conventional therapy for improving upper extremity function in children with neuromotor impairments. The transfer of the behaviors of a human’s upper limbs to an avatar is widely used in the field of virtual reality rehabilitation. Most products cannot track the upper limbs, including the arms and all the fingers at the same time, which limits the limb parts for tracking in a virtual environment and may lead to a limited rehabilitation effect

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