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J.L. Pons et al. (Eds.): Converging Clinical & Engi.
Research on NR, BIOSYSROB 1, pp. 255258. DOI:
10.1007/978-3-642-34546-3_40 Springer-Verlag Berlin Heidelberg
2013
Design of a Pediatric Exoskeleton for the Rehabilitation of the
Physical Disabilities Caused by Cerebral Palsy
Marina Canela1, Antonio J. del Ama2, and Jos Luis Pons1
1 Bioengineering Group of the Spanish National Research Council,
Madrid, Spain mcr1088@gmail, [email protected] 2 Biomechanics and
Technical Aids Department National Hospital for Spinal Cord Injury,
Toledo, Spain
Abstract. Exoskeletons for lower limbs represent a tool to
assist gait training on patients with impaired mobility resulting
from spinal cord injury or cerebral palsy, among other pathologies.
The exoskeleton designs proposed so far are generally oriented to
adult patients. In this work, we propose a new exoskeleton
specifically focused on children with cerebral palsy in the age
range of 7 and 17. Its design and development process is here
presented and future application proposed.
Keywords: exoskeleton, cerebral palsy, pediatrics,
rehabilitation, design.
1 Introduction
Cerebral palsy (CP) is the term to define a group of disorders
of movement and/or posture that results from a permanent injury of
the central nervous system, causing ultimately a physical
disability. There are different types of CP, which can be
classified by predominant motor disorder, anatomical distribution
and functional status. Every type of CP requires different
rehabilitation strategies. Furthermore, the same pathology may
result in different clinical features, requiring more customization
in the design of the rehabilitation management.
An exoskeleton is an artificial external structure that assists
the natural skeleton of the user in the performance of usual tasks
like moving or carrying weights. These devices can also be used in
the rehabilitation of children with impaired locomotion such as in
CP.
Like in other disorders, musculoskeletal problems caused by CP
can be improved if they are treated in initial stages.
Consequently, it is crucial to offer to this type of patients the
available rehabilitation technology at earlier ages.
In this paper we present the process and results of the
mechanical design of a pediatric exoskeleton for the rehabilitation
of the physical disabilities caused by CP. The starting points of
this methodology are, on the one hand, the anthropometric
requirements needed to fit to a majority of users, and on the other
hand, a previous adult version of the device, which has been
adequately adapted to meet the cited necessities.
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256 M. Canela, A.J. del Ama, and J.L. Pons
2 Materials and Methods
The design of the pediatric exoskeleton for the rehabilitation
of physical disabilities caused by CP consisted in two fundamental
stages. First, the specifications of the users were obtained from a
preliminary study of the target population. After that, the design
of the exoskeleton was developed.
2.1 Definition of Users Specifications and Device Requirements
The exoskeleton is focused to a child population, aged between 7
and 17 years old. From public anthropometric data [1][2], including
tibial and femoral lengths in children, and an estimation of the
ankle height performed at the laboratory, it was possible to
calculate the height range of the three articulations involved in
the design of the exoskeleton.
A variety of exclusion criteria for the target users must be
taken into account in order to guarantee a correct operation of the
device: epilepsy, arthrodesis, anatomical anomalies, anatomical
dysmetria, high pelvic obliquity (> 10), spasticity (> 2 in
the Modified Ashworth scale), injuries and fractures and
obesity.
2.2 Design of the Exoskeleton The pediatric exoskeleton has been
developed from a previous adult version developed in the context of
the EU funded projects Hyper [3], and Gait [4]. Independent legs
compose the adult exoskeleton. Each leg is constituted by two
segments (tibial and femoral) and a foot support. These three parts
are articulated by three joints and are adjusted to the body by
means of several belts. This base configuration has evolved with
modifications and ended up in a pediatric version. Specifically,
the tibial segments has been replaced by telescopic bars of three
interchangeable sizes (Table 1), allowing to fit a larger
population.
Table 1 Corresponding articulation heights for each tibial
telescopic system size
The rest of the components, including electric motors, reducers
(Table 2), belts and fixations, have been resized to meet the force
requirements of a child, which are lower than in an adult.
Tibial telescopic
bar size
Ankle height range (mm)
Knee height range (mm)
Hip height range (mm)
Small 95.0 100.0 219.4 266.0
489.5 536.0
Medium 100.0 110.0 266.0 313.0
536.0 620.0
Large 110.0 110.5 313.0 359.6
520.0 666.5
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Design of a Pediatric Exoskeleton for the Rehabilitation of the
Physical Disabilities 257
Table 2 Components of the actuator system in the pediatric and
adult version. Both adult and pediatric version reducers are
harmonic drive and remain the same. Notice that only the hip motor
of the adult version had to be resized to meet the pediatric
version needs.
The exposed knowledge and modifications were taken into account
and incorporated into the design performed with the 3D
computer-aided design (CAD) tool for solid modeling Pro/Engineer
(Parametric Technology Corp., Needham, Massachusetts, USA) that
yielded the pediatric exoskeleton final design.
3 Results and Conclusions
Results of the design process are shown in Figures 1 to 3. The
render of a single leg of the pediatric exoskeleton is shown in
Figure 1 from two different perspectives.
Fig. 1 Render of the 3D model of the left leg of the pediatric
exoskeleton from two points of view
In figure 2, the three exoskeleton articulations are shown,
detailing the main components that form them.
A view of the smallest size of the pediatric exoskeleton model
is represented in Figure 3, including the segments and
articulations measures.
In this article the methodology used to design and develop a
pediatric exoskeleton capable of assisting the rehabilitation of
the locomotor effects of the CP has been discussed. Prior to the
design tasks, anthropometric requirements of child population have
been considered. After that, the mechanical system has been
designed from a previous adult version of the exoskeleton. In a
near future a series of experiments will be held in patients to
validate the usefulness of the device during the
rehabilitation.
Joint Adult version motor
Pediatric version motor
Reducer
Ankle EC-45 70W 24V EC-45 70W 160/1 Knee EC-45 70W 24V EC-45 70W
160/1 Hip EC-90 90W 24V EC-45 70W 160/1
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258 M. Canela, A.J. del Ama, and J.L. Pons
Fig. 2 Schematics for the three articulations, including its
main components
Fig. 3 The small size version of the exoskeleton model. Mean
height of the 7-year-old children is compared to the mean adult
height.
References
[1] Ha, J.H.: Distribution of lengths of the normal femur and
tibia in Korean children from three to sixteen years of age.
Journal of Korean Medical Sciences 18(5), 715721 (2003)
[2] Anderson, M.: Distribution of Lengths of the Normal Femurand
Tibia in Children from One to Eighteen Years of Age. Journal of
Bone and Joint Suregery American 46, 11971202 (1964)
[3] del Alma, A.J.: Actuadores multimodales para compensacin de
la marcha de personas con patologa neurolgica. XXXII Jornadas
Automtica, Vigo
[4] Cullell, A.: Biologically based design of an actuator system
for a kneeanklefoot orthosis. Mechanism and Machine Theory 44,
860872 (2009)
Design of a Pediatric Exoskeleton for the Rehabilitation of the
Physical Disabilities Caused by Cerebral PalsyIntroductionMaterials
and MethodsDefinition of Users Specifications and Device
RequirementsDesign of the Exoskeleton
Results and ConclusionsReferences
