Robotic Mirror Therapy System for Functional Recovery of Hemiplegic Arms

Summary

We developed a real-time mirror robot system for functional recovery of hemiplegic arms using automatic control technology, conducted a clinical study on healthy subjects, and determined tasks through feedback from rehabilitation doctors. This simple mirror robot can be applied effectively to occupational therapy in stroke patients with a hemiplegic arm.

Abstract

Mirror therapy has been performed as effective occupational therapy in a clinical setting for functional recovery of a hemiplegic arm after stroke. It is conducted by eliciting an illusion through use of a mirror as if the hemiplegic arm is moving in real-time while moving the healthy arm. It can facilitate brain neuroplasticity through activation of the sensorimotor cortex. However, conventional mirror therapy has a critical limitation in that the hemiplegic arm is not actually moving. Thus, we developed a real-time 2-axis mirror robot system as a simple add-on module for conventional mirror therapy using a closed feedback mechanism, which enables real-time movement of the hemiplegic arm. We used 3 Attitude and Heading Reference System sensors, 2 brushless DC motors for elbow and wrist joints, and exoskeletal frames. In a feasibility study on 6 healthy subjects, robotic mirror therapy was safe and feasible. We further selected tasks useful for activities of daily living training through feedback from rehabilitation doctors. A chronic stroke patient showed improvement in the Fugl-Meyer assessment scale and elbow flexor spasticity after a 2-week application of the mirror robot system. Robotic mirror therapy may enhance proprioceptive input to the sensory cortex, which is considered to be important in neuroplasticity and functional recovery of hemiplegic arms. The mirror robot system presented herein can be easily developed and utilized effectively to advance occupational therapy.

Introduction

For patients with stroke, dysfunction of a hemiplegic arm has debilitating effect. The ability to perform bimanual activities is essential for daily life, but functional deficit of a hemiplegic arm often remains even a few years after stroke onset. Among various training programs in the hospital, an exercise to increase the range of motion or passive repetition of simple tasks have little effect on functional recovery of a hemiplegic arm. For this reason, training of meaningful tasks related to activities of daily living (ADLs) has been applied to occupational therapy in hospitals.

The effects of mirror therapy were proven by previous studi....

Protocol

 All of the procedures were reviewed and approved by the Institutional Review Board of Seoul National University Hospital.

1. Mirror Therapy Tasks

1. Examples of 2-dimensional mirror therapy tasks (Figure 3)
   1. Freely move the healthy arm while looking in the mirror about 5 min for warm-up exercise.
      NOTE: One may utilize a metronome so that the patient can exercise the motion of the healthy arm in a rhythmic manner.
   2. On healthy side, dribble and place a small ball into the chosen hole similar to billiards for about 5 min ("Ball in holes" task). Dribble and place a small ball into a goal similar to soccer for ab....

Results

Six healthy subjects conducted a 'pen marking task' (touching the two small boards alternately with a pen attached on the healthy hand as shown in Figure 17) 10 times which took on average 106 sec per subject. No adverse event was observed, and robotic mirror therapy was proven to be feasible.

In addition, a clinical study on rehabilitation doctors was conducted. We requested expert opinions to determine appropr.......

Discussion

The primary purpose of this study was to develop a real-time mirror robot system for functional recovery of a hemiplegic arm using an automatic control algorithm. The effect of robot-assisted therapy on long-term recovery of upper-limb impairment after stroke was proven beneficial in previous studies¹², and various kinds of arm robots have been introduced^13-20. However, previous studies of upper extremity robots that realized bilateral arm movement applied mechanical connections without using a mirr.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
LabVIEW	National Instruments		System design software
24 V power supply	XP Power	MHP1000PS24 24V	Any 24 V power supply should do
AHRS sensor receiver	E2box	EBRF24GRCV
AHRS sensors	E2box	EBIMU-9DOFV2	You will need total 3 sensors. Any AHRS sensors will do
EC90 flat motor module	Maxon	323772 + 223094 + 453231	Any geared motor with higher than 30 Nm should do. (For our custom machined parts, you will need these particular flat motor and gear module, but the gear ratio and encoder may vary)
EC45 flat motor module	Maxon	397172	Any geared motor with higher than 10 Nm should do (For our custom machined parts, you should use the same gear module but the gear ratio, motor, and encoder may vary)
EPOS2 70/10 controller	Maxon	375711	This can be replaced with EPOS 24/5 controller
EPOS2 24/5 controller	Maxon	367676
Connector and cable set	Maxon	381405 + 384915 + 275934 + 354045	You can also make these cables. Connectors and corresponding wire info can be found in "300583-Hardware-Reference-En.pdf" and "300583-Cable-Starting-Set-En.pdf"
Coupling- Oldham, Set Screw Type	Misumi	MCORK30-10-12	Type may vary
Coupling- High Rigidity, Oldham, Set Screw Type	Misumi	MCOGRK34-12-12	Type may vary
Shaft Collars	Misumi	SCWDM10-B	You will need 4 sets
Shaft Collars	Misumi	SDBJ10-8	You will need 2 sets
Precision Linear Shaft	Misumi	PSSFG10-200	Any straight 10 mm diameter shaft with at least 200 mm length should do
Bearings with housings	Misumi	BGRAB6801ZZ
Elbow motor force dispersion shaft	custom machined	3D CAD
Lower elbow support	custom machined	Part Drawings
Elbow rooftop frame	custom machined	Part Drawings
Support wall	custom machined	Part Drawings	You will need 2 frames.
Elbow coupling hollow cylinder cover	custom machined	Part Drawings
Wrist motor force dispersion shaft	custom machined	Part Drawings
Wrist rooftop frame	custom machined	Part Drawings
Upper wrist coupling hollow cylinder cover	custom machined	Part Drawings
Lower wrist coupling hollow cylinder cover	custom machined	Part Drawings
Joint movement limiter	custom machined	Part Drawings
Handle	3D printed	Part Drawings
Upper elbow support	3D printed	Part Drawings
Friction reduction ring	3D printed	Part Drawings
Acrylic mirror	custom laser cutting	Part Drawings
Task table	custom machined	Part Drawings
Silicone sponge
DOF limiter	3D printed	Part Drawings
DOF limiter lid	3D printed	Part Drawings
Healthyarm handle	3D printed	Part Drawings
Ball rollers - Press fit	Misumi	BCHA18
Goalpost	3D printed	Part Drawings
Circle trace	3D printed	Part Drawings
Angled assist	3D printed	Part Drawings	Optional
Curved assist	3D printed	Part Drawings	Optional
Plain assist	3D printed	Part Drawings	Optional
Task board	custom laser cutting	Part Drawings