Development and Testing of a Modular Upper Extremity Exoskeleton

for Infants

Tariq Rahman

, Cole Galloway

, Elena Kokkoni

and Michele Lobo

Department of Biomedical Research, Nemours/A.I. duPont Hospital for Children, Wilmington, Delaware 19899 U.S.A.

Department of Physical Therapy, University of Delaware, Nerwark, Delaware 19716 U.S.A.

Keywords: Orthosis, Upper Extremity, Exoskeleton, Motor Control, Infants.

Abstract: A passive upper extremity exoskeleton has been developed for people with neuromuscular weakness. The

WREX (Wilmington Robotic EXoskeleton) has been used successfully for a number of years by people

with disabilities such as muscular dystrophy and arthrogryposis. This paper describes the modification of

the WREX to be fitted with infants. The Pediatric WREX Plus (P-WREX+) can selectively assist or resist

antigravity arm movements based on the needs of each individual. It consists of a 3-D printed device that

can be mounted to a jacket or a chair and allows infants more access to their environment by augmenting

anti-gravity arm movement. The target population is infants born with brain injuries and at high risk for

significant neuro-motor impairments. The paper describes the development of the device and testing with an

infant with arthrogryposis over a 6-month period.

1 INTRODUCTION

Bioengineered devices for the arms have made

significant advances in the rehabilitation of adults

with nervous system injury. There is a surprising

lack of adaptation of these devices for use in

pediatric populations. This is especially troubling

given the importance of early intervention and

rehabilitation for optimal neurological and

behavioral development. This paper describes the

development of a novel upper extremity orthosis that

is based on the WREX, which is a passive upper

extremity orthosis.

One version of the WREX, figure 1, is a

mechanical linkage that can be attached to a

wheelchair and is powered by elastic bands

(Haumont 2011, Rahman 2007). The device moves

alongside the arm and makes anti-gravity

movements effortless. This is particularly useful for

people with muscular dystrophy and spinal muscular

atrophy where weakness in larger proximal muscles

is evident while distal muscles are less affected. The

WREX allows them to navigate their hand in front

of them and perform activities of daily living. The

WREX comes in one size and can be adjusted to

accommodate different sized individuals and the

number of elastic bands can be changed depending

on the weight of the individual.

A second version of the WREX is made for

smaller children, figure 2. A 3-D printer is used to

fabricate the parts resulting in a lighter and custom

fitted device. Some of the children are able to

ambulate independently therefore require a body-

mounted WREX. We modified a

thoracolumabarosacral orthosis (TLSO) commonly

used for scoliosis treatment.

The WREX has been used successfully in

children older than 2 years of age but has not yet

been used in infants. This paper describes the

experience of using the P-WREX+ for wear and

intervention with an 8-month-old infant with

arthrogryposis multiplex congenita (AMC). Infants

with AMC are born with joint contractures and

muscle tissue fibrosis in more than one region of the

body. Typically the biceps and deltoid muscles are

weak preventing performance of key activities

against gravity.

We wanted to provide this technology in

coordination with intervention to advance the

exploratory and learning abilities of this infant with

special needs. Exoskeletons such as the WREX

advance movement and function in older children

and adults with neuro-motor impairments (Iwamuro

2008, Hesse 2003).

This study is the first to systematically test the

effects of a similar device on reaching ability in an

infant with significant arm movement impairments.

316

Rahman T., Galloway C., Kokkoni E. and Lobo M..

Development and Testing of a Modular Upper Extremity Exoskeleton for Infants.

DOI: 10.5220/0004938003160319

In Proceedings of the International Conference on Biomedical Electronics and Devices (TPDULL-2014), pages 316-319

ISBN: 978-989-758-013-0

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

2 P-WREX+ DEVELOPMENT

The WREX is 4 degrees of freedom, 2-link

mechanism, fig 2, that supports the weight of the

arm for all positions in 3-D space. It is passively

actuated by elastic bands placed on the forearm and

the upper arm links. A four bar mechanism on the

upper arm provides a vertical member at the elbow

during the entire vertical excursion. The stiffness of

elastic bands, and end points are chosen according to

Figure 1: WREX attached to wheelchair.

The P-WREX+ was scaled down in size to fit a 3-8

month old infant. The jacket was also made smaller

and lighter, Fig 3. All the parts of the P-WREX+

were made with ABS plastic. It is inexpensive,

lightweight, portable, adaptable, and easy to use. It

is fabricated by a small, in-house 3-D printer

(Dimension 1200, Stratasys, Eden Prairie, MN)

analysis described in (Rahman, 1995). The resulting

motion provides identical equilibrium for all

position of the arm. This allows an individual to

perform activities of daily living such as eating in a

gravity-free environment. The number of bands can

be varied according to the weight of the subject and

Figure 2: Joint layout of the wrex.

the link lengths can be adjusted for different sized

subjects.

Figure 3: p-wrex+.

3 EXPERIMENTAL PROTOCOL

Participant: We followed an 8-month-old infant

diagnosed with AMC for a 6-month period.

Although he was born with joint contractures, he had

functional passive range of motion at all joints of the

upper extremities at the time he entered the study.

This was the result of early intervention and daily

stretching. His muscle strength for raising his upper

extremities (shoulder flexion) against gravity while

sitting was poor minus. He could perform less than

10 degrees of shoulder flexion against gravity and

only partial range of motion with gravity eliminated.

The assessments were video recorded and later

coded by trained and reliable (>85% reliability)

coders. They recorded times the infant was

contacting the object and times he was looking at the

object

During the baseline period, the infant did not use

the P-WREX+ outside of the brief assessment

periods. During the intervention period, the infant

wore the P-WREX+ daily for an hour while

performing prescribed play activities aimed at

promoting reaching and object manipulation

abilities. During the post-intervention period, the

child kept the P-WREX+ and wore it daily as during

the intervention period but he was no longer

provided the prescribed play activities while wearing

the device

Data Analysis: Results were analyzed via visual

inspection of charted data.

Hand

Shoulder

DevelopmentandTestingofaModularUpperExtremityExoskeletonforInfants

317

Figure 4: Graph showing the time the toy was contacted by the subject with the WREX.

4 RESULTS

There are several important findings from this

preliminary study. First, the infant was able to safely

and comfortably wear the P-WREX+ daily,

suggesting this and similar devices can successfully

be incorporated into the lives of families with infants

and young children.

Second, the infant was almost always better able

to interact with objects while wearing the P-

WREX+. Interaction with objects is important for

early language, perceptual-motor, social, and

cognitive development and is a precursor for future

essential life skills such as dressing and feeding.

Therefore, devices like the P-WREX+ may be useful

in advancing global development and upper

extremity function.

Third, intervention in combination with use of

the device was more effective at advancing behavior

than was use of the device alone.

This suggests devices like the P-WREX+ have

strong potential to advance development and

function when paired with play activities prescribed

by an early intervention expert.

Finally, the infant showed improved ability to

interact with objects, figs 4,5, throughout the study

even when he was not wearing the device. This

suggests devices like the P-WREX+ are not only

successful assistive devices that improve function

when worn, but that they may also be successful

rehabilitation tools that result in behavioral advances

even after they are doffed.

Future goals for this research program include:

1) determining the impact of the P-WREX+

for infants, children, and adults with a variety of

1 4 7 1013161922

PercentTime

WeekinStudy

TotalTimeContactingtheToy

P‐WREX+ON

P‐WREX+OFF

Intervention

Post‐

Interventio

Baseline

BIODEVICES2014-InternationalConferenceonBiomedicalElectronicsandDevices

318

Figure 5: Graph showing the time the toy was contacted while looking at it by the subject with the WREX.

diagnoses impacting arm movement, such as brain

injury, brachial plexus palsy, and stroke, and, 2)

exploring both low-tech and high-tech future

adaptations of the device.

ACKNOWLEDGEMENTS

We would like to thank Mr Whitney Sample for

construction of the p-WREX+ and the Nemours

foundation for funding.

REFERENCES

Iwamuro, B.T., Cruz E.G., Connelly L.L., Fischer H.C.,

Kamper D.G., 2008. Effect of a Gravity-Compensating

Orthosis on Reaching After Stroke: Evaluation of the

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Hesse S., Schmidt H., Werner C., Bardeleben A. 2003.

Upper and lower extremity robotic devices for

rehabilitation and for studying motor control. Current

Opinion in Neurology. Dec;16(6):705-710.

Haumont T., Rahman T., Sample W., King M., Church C.,

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exoskeleton: a novel device to maintain arm

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Rahman T., Sample W., Seliktar R., Clark A.., Scavina

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