Universidad Nacional de Chimborazo
NOVASINERGIA, 2020, Vol. 3, No. 1, diciembre-mayo, (54-61)
ISSN: 2631-2654
https://doi.org/10.37135/ns.01.05.06
Research Article
Rehabilitation system based on an electronic splint for recovery of wrist
and radial nerve injuries
Sistema de rehabilitaci
´
on basado en una f
´
erula electr
´
onica para recuperaci
´
on de
lesiones de mu
˜
neca y nervio radial
C
´
esar Palacios
1
*, Jos
´
e Jinez
2
, Mar
´
ıa Jos
´
e L
´
opez
1
, Diana Guananga
2
, Angel Vinueza
2
1
Signal Theory and Communications Department, Universitat Polit
`
ecnica de Catalunya, Barcelona, Spain, 08034
2
Facultad de Ingenier
´
ıa, Universidad Nacional de Chimborazo, Riobamba, Ecuador, 060150; jjinez@unach.edu.ec;
maria.jose.lopez.montero@upc.edu.ec; dguananga@fie.unach.edu.ec; avinueza@fie.unach.edu.ec
* Correspondence: cesar.augusto.palacios@upc.edu
Recibido 02 abril 2020; Aceptado 20 mayo 2020; Publicado 01 junio 2020
Abstract:
In this work, a rehabilitation system based on an electronic splint for people that have
suffered radial nerve injuries is presented. The system is composed of two parts: the
electronic splint and the electrostimulator. Electrostimulation is performed utilizing
controlled electric current at a frequency from 18 to 83 Hz with a triangular pulse train
with 7 mA of amplitude. The splint has been made using surgical steel and textile
materials to make it more comfortable for the patient. The splint moves from top to
bottom and left to right by servo motors controlled by Matlab. The information of
the rehabilitation system is stored in a database to be analyzed, even remotely, by a
physiotherapist.
Keywords:
Electronic splint, electronic stimulation, radial nerve injuries, rehabilitation process,
wrist injuries.
Resumen:
En este trabajo, se presenta un sistema de rehabilitaci
´
on basado en una f
´
erula
electr
´
onica para personas que han sufrido lesiones del nervio radial. El sistema
se compone de dos partes: la f
´
erula electr
´
onica y el electroestimulador. La
electroestimulaci
´
on se realiza utilizando corriente el
´
ectrica controlada a una
frecuencia de 18 a 83 Hz con un tren de pulsos triangular con una intensidad de
7 mA. La f
´
erula se ha realizado con acero quir
´
urgico y materiales textiles para que
sea m
´
as c
´
omoda para el paciente. La f
´
erula se mueve de arriba a abajo y de izquierda
a derecha mediante servomotores controlados por Matlab. La informaci
´
on del sistema
de rehabilitaci
´
on se almacena en una base de datos para ser analizada, incluso de
forma remota, por un fisioterapeuta.
Palabras clave:
Electroestimulaci
´
on, F
´
erula Electr
´
onica, Lesiones de Mu
˜
neca, Lesiones de Nervio
Radial, Rehabilitaci
´
on
1 Introduction
One of the five major branches of the brachial
plexus is the radial nerve, it provides the arm and
forearm with motor and sensory innervation (Lowe
et al., 2002). Figure 1 sketches the nerve extension.
Radial nerve palsy is one common injury to this
nerve, symptoms can include pain, weakness, and
http://novasinergia.unach.edu.ec
loss of sensation along the back of the arm, forearm,
and hand (Bumbasirevic et al., 2016). In general,
paralysis hinders the mobility and extension of the
wrist and fingers. Therefore, this disease is called
“dropped hand” (Pi
˜
na-Garza & James, 2019). After
suffering a radial nerve injury, a person should
always be subjected to arm rehabilitation to recover
the mobility and operability (Niver & Ilyas, 2013).
Figure 1: Radial nerve extension.
(Barton, 1973) and (Parry et al., 1981) highlight
the importance of splinting to ease flexion of
the fingers; there are a number of splinting
solutions for the radial nerve palsy problem. The
biggest challenge is to prevent over-stretching the
denervated muscles and substitute the extensor
muscle, effectively. Static splint stabilizes the wrist
(Pearson, 1984) allowing the transmission of force
to the flexors for power grip. Immobilization of the
wrist only accentuates the inability of the fingers
and thumb to open out of the palm (Colditz, 1987).
In the relevant literature there are several studies
dealing with this problem. In (Willand, 2015),
authors performs some experiments about daily
muscle stimulation paradigm in rats, following
nerve injury. Results show that re-innervation
of muscle and functional behavioral metrics
are enhanced with daily stimulation with the
up-regulation of intramuscular neurotrophic factors
as a potential mechanism. In (Rodrigues et al.,
2016), the evaluation of several subjects on carpal
tunnel syndrome (CT S) is carried out, to whom
fulfill the criteria; a recovery method based on
action potentials is applied. The response to
electrical stimulation is faster than conventional
methods.
In Ecuador, there are some investigations about
rehabilitation, many of them for diverse sorts of
injuries and different splint construction methods.
In Universidad Cat
´
olica Santiago de Guayaquil,
was built a robotic hand controlled by the foot
(Espinoza Mor
´
an, 2014). In the same way, students
from Chimborazo proposed a prosthesis for the
leg replacement (Romero Erazo, 2016), and
posteriorly, it was presented a prototype by using
a 3D printer (Andrade Holgu
´
ın, 2016). Most of
the investigations in Ecuador are focused on the
prosthesis construction but not in conjunction with
the rehabilitation process. This work is one of the
first about radial nerve palsy treatment.
In recent years, the rehabilitation process has been
improved, however, there are some non-favorable
issues related to rehabilitation; most centers require
daily attendance and payment of the patient; for an
extended period. On the one hand, some patients do
not have the financial resources and mobilization
that permits a successful rehabilitation process, and
on the other hand, the technology of the public
therapy centers limits the number of patients that
can be treated at the same time (V
´
elez, 2017).
Conventional methods are currently performed
manually; that is, the physiotherapist performs
manual movements to the patient’s wrist for some
time according to the level of recovery.
This paper presents an autonomous rehabilitation
system based on an electronic splint, capable of
helping people who have suffered wrist and radial
nerve injuries by mean of electric stimulation. The
electronic splint is part of a system, assembled
to collect information during the rehabilitation
process, and storing into a database to be studied
and analyzed by a physiotherapist, in order to
make decisions about the routines that must be
implemented in the splint, in terms of application
time, operating frequency, current level, types of
movements, and other configurable parameters.
The remainder of the paper is organized into four
sections. Section 1 presents the introduction of
the work. Section 2 describes the methodology;
it is divided into two subsections; subsection 2.1
exposes the electronic devices and configurations,
and subsection 2.2 explains the software used in the
rehabilitation system. The evaluation and results are
presented in section 3. Finally, section 4 concludes
the paper.
2 Methodology
The rehabilitation system has been developed in
Matlab, under an academic license. Matlab
processes the data from sensors located in the
electronic splint, trough a serial communication
(RS232 protocol) and implements a database. The
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communication between the electronic splint and
Matlab was done with the Arduino Uno board.
In figure 2 is presented a general scheme of the
rehabilitation system.
Figure 2: General process for rehabilitation system.
2.1 Electronic Splint Systems
The splint was designed using an arm immobilizer
divided in two parts; one to support the forearm and
other to move the hand. Considering the comfort of
the patient, textile materials and surgical steel, were
used. The two parts of the immobilizer were joined
by servo motors, so that the wrist is free to be moved
in the rehabilitation process. Figure 3 shows the
initial prototype, and figure 4 shows the prototype
under testing processes.
Figure 3: Electronic splint design.
Electrical stimulation enhances nerve regeneration
and helps in the functional recovery of the wrist and
radial nerve injuries (Asensio-Pinilla et al., 2009),
but it must be controlled and applied according to
the patient recovery.
The electrostimulator consists of a flex sensor,
a MPC41010 Single/Dual Digital Potentiometer
(Microchip, 2003) and a servo-motor connected to
the Arduino Uno board. The flex sensor controls the
hand position, when the hand drops down, a signal
is sent to the Arduino Uno to action the servo motor
and restore the hand position. At the same time a
Figure 4: Electronic splint prototype.
1:12 voltage transformer is used to have the signal
current, through the electrodes, that is applied at the
patient. To couple the current signal between the
digital potentiometer and the voltage transformer, a
NPN transistor has been placed. Figures 5 and 6,
shows a general view of the setup.
Figure 5: Actuator connected to Arduino Uno board.
Figure 6: Flex sensor connected to Arduino Uno.
The digital potentiometer MCP41010 controls the
current intensity, in order to have safe levels. It
needs one byte for control and one byte for data.
Resistance can change from 180 to 255 Ω. The
http://novasinergia.unach.edu.ec 56
MCP41010 is connected to Arduino Uno board
through the serial peripheral interface (SPI), pins 5
and 7 are connected to 5 v supply.
The relation of conversion of the voltage
transformer is 1:12, connecting 3 v in the input it
raises voltage up to approximately 40 v. Now, if a
600 Ω resistor is connected, the intensity current
should be equal to 60 mA. For the 83 Hz signal with
a period of 12 ms; finally the high pulse is 7 mA,
approximately.
The electric current signal, used for muscles
stimulation, must be controlled in frequency,
intensity and duration of impulses, accordingly to
(Pombo et al., 2004), to maintain the recommended
levels for human rehabilitation. Low frequency
relaxes the muscles and by contrast, high frequency
contributes to the rehabilitation. To control the
frequency, the duty cycle of the current intensity
signal was changed. For 83 Hz, the period of the
signal was 12 ms, so, the time in high level was 1 ms
and the low level was 11 ms, according to equation
1. Figure 7 shows the 83 Hz signal with T = 12 ms.
Finally, by changing the high and low levels to 5 ms
and 50 ms, respectively, the signal of 18 Hz was
generated.
Figure 7: Signal of 83Hz.
f =
1
T
=
1
(t
h
+t
l
)
(1)
where:
f =frequency,
T = period,
t
h
= on time,
t
l
= off time.
The movements of the electronic splint were
controlled by two servomotors of 20 Kg, placed
vertically on top of each other, as illustrated in
figure 8, one servomotor controls up and down
movement and the other right and left movement.
Servomotors are commanded by a pulse-width
modulation (PWM) signal from Matlab. Next
section explains the software used for the system.
Figure 8: Arrange of servomotor.
2.2 Software to control the
rehabilitation system
The software for the rehabilitation system,
previously shown in figure 2, implements some
components, among them, graphical interface,
database, and serial communications. The
components were implemented by using Matlab,
under an academic license. Arduino Uno libraries
must be installed into Matlab, in order to control
the board through a serial communication. Matlab
sends commands to move servomotors according
to the information received by the flex sensor.
The installation of Arduino Uno libraries, was
made from the Matlab interface, first clicking the
Add-Ons icon, then choosing the “Get Hardware
Support Package” option, and finally, selecting the
Arduino Uno option.
An important issue of the rehabilitation system
is the database. The graphic user interface was
also designed using Matlab, called TherapyCenter.
The interface initially presents a form to capture
data patients, for example, patient photography,
personal information, injuries causes, diagnosis and
treatment, allergies, and other medical observations
about the injury. The software allows exportation,
of the information, to an Excel spreadsheet where a
code is assigned for each patient and the exact time
and date of access to the rehabilitation system is
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recorded.
The program also provides three levels for selecting
the severity of the injury, which are, minimal,
normal, and severe. According to the selected
injury level, the time of treatment fluctuates from
one week, one month or six month of application,
respectively. The system is accessed through
credentials, for medical personnel and patients.
3 Results
In this sections are presented the results of the
rehabilitation system, among them, the software
results, the electronic splint under test, and the
electrostimulator results.
3.1 Data base storing
Therapycenter allows inserting the information of
the patient and exporting to an excel spreadsheet.
Figures 9 and 10 depict the user interface and the
exported file. The program automatically assigns
a unique identification code for each patient, that
is also used as password to access to the software.
This guarantees access of authorized users to the
information.
Figure 9: Registration window of therapy center.
3.2 Electronic splint testing
The system was evaluated in the laboratories
of the Physiotherapy department of National
University of Chimborazo. It was then tested
in a patient who initially had 10% of wrist
mobility. The rehabilitation process consisted of
five daily sessions with different duration for eight
consecutive days. The progress was evaluated by
Figure 10: Exported spreadsheet.
mean of the daily variation of the movement angle
of the wrist.
To establish a reference system that allows
evaluating the progress in the rehabilitation, two
perspectives are used. Figure 11(a) shows the
system for hand movement from bottom to top.
Whereas, figure 11(b) shows the reference system
for the movement from left to right, both uses the
normal position of the hand in 90 degrees.
(a) Up to down (b) Left to right
Figure 11: Reference system for hand movements.
Once, the reference systems have been established,
the electronic splint was tested for eight days. A
person, who suffered a low level palsy, with 10%
of hand mobility, used the rehabilitation system.
According to figure 11(a), the position of the hand
in ninety degrees represents the 100% of mobility,
it means that a person with 10% of mobility, can
only move the hand from 0 to 9 degrees.
Tables 1, 2, and 3 report the time, duration and the
results of day one, four and eight, respectively, also
the angles of application and the recovery progress,
are reported. Angles are measured from the turn of
the servo motor applied to raise up the hand. The
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recovery percentage is computed according to the
degrees measured after the rehabilitation session,
the patient, manages to raise up and move laterally
the hand, by himself, until approaching the 90
degrees.
Table 1: Data collected on the first day for 2 minutes.
Time
Up-Down
Angle(degree)
Left-Righ
Angle(degree)
Progress(%)
08:00 71.42 11.00 11.36
11:00 78.70 7.50 10.77
14:00 83.47 2.00 12.66
17:00 86.85 0.60 10.40
20:00 89.08 1.40 11.76
Table 2: Data collected on the fourth day for 1 minute.
Time
Up-Down
Angle(degree)
Left-Righ
Angle(degree)
Progress(%)
08:00 77.52 9.70 40.45
11:00 79.20 11.70 45.20
14:00 83.07 0 59.25
17:00 82.95 -0.40 50.85
20:00 88.28 -0.60 48.09
Table 3: Data collected on the eighth day for 15 seconds.
Time
Up-Down
Angle(degree)
Left-Righ
Angle(degree)
Progress(%)
08:00 75.05 12.80 95.52
11:00 75.55 12.10 94.36
14:00 82.92 3.20 96.21
17:00 87.23 4.70 98.21
20:00 89.07 -3.80 99.12
First day, the five sessions were of 2 minutes,
obtaining a rehabilitation progress of 11 % around.
The fourth day, the progress was near of 50 %, the
wrist can move 45
o
. The eighth day, the movement
of the hand was almost complete, and the progress
was 96.68 %. The hand reached the 90
o
of mobility
and held horizontal position.
During the rehabilitation process, the data were
collected in real time. Figure 12 shows the
minimum and maximum angles of movement and
elevation. The objective was to held the hand in
horizontal position, when the rehabilitation process
had been completed; it is presented in figure 13.
The data of the rehabilitation process was stored
in the GUI of Matlab, after exported to an
excel spreadsheet, that is a basic package of
Figure 12: The curve shows that the movements are not
stable.
Figure 13: The curve shows a horizontal stabilization in
the hand.
office software. The information allows the
physiotherapist personnel to have full control of
the process and statistic information in a format
that could be easy to analyze, and export to other
common formats.
3.3 Electrostimulator
The most important parameter that have to
be controlled, is the current signal for the
electrostimulator. The amplitude of the current
was controlled varying the value of the resistance
of the digital potentiometer. The electrostimulator
is formed by the flex sensor, the electric
system, electrodes and the communication with the
computer. Sensor flex is located in the superior
face of the wrist, as illustrated in figure 14(a), a
flexion changes the resistance in the terminals of the
sensor and an electrical signal is sent through the
electrodes, placed on the forearm, as illustrated in
figure 14(b).
The electrostimulator operates in three different
modes depending on the level of injury. Level one
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(a) Flex sensor in the wrist (b) Electrodes
placement
Figure 14: Flex sensor and electrodes placement.
can operate without the electronic splint, while
levels two and three operate along the splint.
Level one is used for relaxing the muscle at 18 Hz
frequency and for contracting the muscle with
83 Hz. In this mode the flex sensor sends the signal
to rise up the hand if it drops down. Level two and
three act during the rehabilitation session helping
muscles to contract and relax while the splint
moves the hand. The difference between level two
and three is the amplitude of the current signal.
Level tree is used for strong injuries. Stimulation
is a pulse train signal with amplitude and duration
according to recommendations for neuromuscular
recovering (Marqueste et al., 2004). Figure 15
illustrates the value of the control resistance for
controlling the amplitude of the signal.
Figure 15: Amplitude, resistance, and impulse train.
4 Discussion
Most of conventional methods for rehabilitation of
the radial nerve are based on daily sessions assisted
by a physiotherapist for relative long periods of
time. Other options include orthopedic splint or
surgery. The results of the conventional methods
have shown to be successful, however they take
a long time and could be expensive for the daily
payment that frequently occurs.
Today the advancement and demand for technology
is high, this encourages the use of telemedicine
and biomedical systems. The rehabilitation system
presented here, is an interesting option, which
presents four advantages in comparison with
conventional methods:
• The physical therapist personnel is not required
all time,
• The system consist of a portable splint,
• The payment is not daily,
• The complete rehabilitation implies lower time.
An advantage worth mentioning is that the recovery
time is reduced. Although, it is not a significant
difference, it has been possible to decrease the
number of sessions in comparison to conventional
methods. Figure 16 shows a comparison between
the angle of mobility reached by a person using the
proposed splint versus another with conventional
methods.
Figure 16: Benefits of use electronic splint.
A disadvantage of the system is ergonomics, since
it has been designed for a single treatment. And the
dimensions cannot be attached to anyone.
5 Conclusion
From the conducted study, it can be concluded
that it is possible to build a rehabilitation system
using low-cost electronic elements, with results
comparable to traditional methods. A patient
using the proposed system may have more stability
http://novasinergia.unach.edu.ec 60
on the hand than a person with conventional
methods considering the similar duration of the
rehabilitation.
Matlab programming software is an essential tool
in the development of multi-platform systems, due
to the compatibility and availability of libraries
it was possible to carry out the Arduino-Matlab
communication.
The rehabilitation system presented in this work
allows the remote monitoring of the progress of the
rehabilitation. The database stores the information
of each patient and the results that are updated for
each new session.
Acknowledgment
Authors would like to thank Prof. Luis Poalas
´
ın,
who provided insight and expertise in physical
therapy.
Interest Conflict
Authors declare that there is no conflict of interest
in this research.
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