Custom Built Device for Spasticity Evaluation Associated to Spinal

Cord Injury

A Redundant Signal to Electrogoniometer in Pendulum Test

Renata Manzano Maria

1,2

, Karina Cristina Alonso

Eliza Regina Ferreira Braga Machado de Azevedo

, Renato Varoto

and Alberto Cliquet Jr.

1,2

Department of Electrical Engineering, University of São Paulo (USP), São Carlos, Brazil

Department of Orthopedics and Traumatology, University of Campinas (UNICAMP), Campinas, Brazil

Keywords: Spasticity, Pendulum Test, Biomedical Engineering, Electrogoniometer, Goniometry, Accelerometer, Spinal

Cord Injury, Clinical Evaluation.

Abstract: The proposal of this project was the development of a more objective system to evaluate spasticity,

dysfunction often presented by spinal cord injured people. As result, it will be possible to follow patient’s

progress in moments before and after any treatment, drawing comparisons through the acquired data. One

accelerometer was added to the original pendulum test, providing redundant and alternative signal to the

electrogoniometer, even in critical situations. Also, tests were performed in patients during treatments, what

confirmed the feasibility of the present system in this method of evaluation.

1 INTRODUCTION

There are many causes of spinal cord injuries.

Among them are: automobilist accidents, fire guns

and diving into shallow waters. Non-traumatic

causes, as nervous system diseases, can also lead to

injury.

When spinal cord injury occurs, communication

between the brain and body is affected,

consequently, conduction of motor and sensory

information is impaired.

1.1 Spinal Cord Injury Levels

Injury can be complete, when there is an absence of

sensory and motor function in the lowest sacral

segments; or incomplete, when there is preservation

of any sensory and/or motor function below the

neurological level that includes the lowest sacral

segments (Kirshblum et al., 2011).

Paraplegia refers to impairment or loss of motor

and/or sensory function in the thoracic, lumbar or

sacral (but not cervical) segments of the spinal cord,

consequent to the damage of neural elements within

the spinal canal. With paraplegia, upper limb

function is preserved, but, depending on the injury

level, trunk, lower limbs and pelvic organs may

present functional losses (Kirshblum et al., 2011).

Tetraplegia term refers to motor or sensory

dysfunctions of spinal cord cervical segments due to

damage of neural elements within the spinal canal.

Tetraplegia results in impairment of function in

upper limbs as well as typically in trunk, lower

limbs and pelvic organs (Kirshblum et al., 2011).

Certain time after the occurrence of the spinal

cord injury, movement disorders tend to appear,

what hinders these people’s lives and can induce

pain.

This study focus on one of these disorders: the

spasticity.

1.2 Muscle Tone and Spasticity

Each motoneuron, that originates from spinal cord,

innervates many muscle fibers. As the muscle fibers

do not contract themselves without the existence of a

real action potential to stimulate them (except in

some pathological situation), skeletal muscle tone is

totally dependent of nervous impulses originated

from spinal cord. Muscle tone is a state of partial

tension of the muscle at rest that allows the

contraction to start immediately after receiving a

nervous impulse, besides of defining the strength

with that the muscle resists to being strained. These

120

Manzano Maria R., Alonso K., Ferreira Braga Machado de Azevedo E., Varoto R. and Cliquet Jr. A..

Custom Built Device for Spasticity Evaluation Associated to Spinal Cord Injury - A Redundant Signal to Electrogoniometer in Pendulum Test.

DOI: 10.5220/0004234001200126

In Proceedings of the International Conference on Biomedical Electronics and Devices (BIODEVICES-2013), pages 120-126

ISBN: 978-989-8565-34-1

 2013 SCITEPRESS (Science and Technology Publications, Lda.)

impulses are controlled in part by impulses

transmitted by the encephalon to the correspondent

motoneurons and in part by impulses originated

from muscle fuses localized in the proper muscle

(Guyton, 1997).

The increase of muscle tone characterizes the

spasticity. In physical exam, spastic limbs present an

increased resistance to passive movement, which is

more accentuated with the increase of the amplitude

and speed imposed. The increased resistance to

stretching is greater at the beginning of the

movement, and decreases thereafter. (Leitão et al.,

2006).

As spasticity affects the quality of spinal cord

injured people’s lives, since it causes functional

difficulties, besides pain and contractures, some

specific treatments can decrease these effects in

some muscle groups. Treatment is often considered

essential to prevent deformities, improve function

and release stressing symptoms (Miyazaki et al.,

2008).

1.3 Rehabilitation

Some treatments are more used in rehabilitation

programs, aiming the reduction of patient incapacity.

Kinesiotherapy, Locomotor Treadmill Training,

Functional Electrical Stimulation, use of orthoses

and medication treatments are examples with

satisfactory results (Lianza et al., 2001).

According to Dietz (2008), complete spinal cord

injured individuals are beneficiated by gait training,

mainly by atrophy prevention and spasticity

reduction.

Patients can perform treadmill gait training

associated to neuromuscular electrical stimulation

(NMES). They are assisted by partial body weight

support (BWS) (30-50%, to allow heel strike), and

by physiotherapists that help them move their legs.

During treadmill gait (at 0.14-0.39 m/s), the 4-

channel electrical stimulator is also used to provide

NMES to aid the stance gait phase (through

quadriceps muscle activation) and the swing phase

(stimuli to the fibular nerve) (Carvalho et al., 2006;

Abreu et al., 2009).

1.4 Existent Evaluation Methods

The increase of new methods in spasticity treatment

has driven forward new mechanisms to quantify its

degree, measuring progression and success of these

methods. In fact, there is a trend towards more

objective measurements in order to make possible

more precise and exact analysis.

In spasticity assessment, quantitative and

qualitative indicators are used. They are used to

identify intensity and influence on functional

performance, being useful for indication of

therapeutic interventions and analysis of assessment

results (Leitão et al., 2006).

Scales are common clinical measures of muscle

tone, among them are Ashworth Scale, Modified

Ashworth Scale and Spasm Frequency Scale.

Besides the patient’s influence, scales are also a very

subject grading method and do not allow smaller

degrees identification.

The use of tonus as a resource to establish

neurological diagnoses is possible through pendulum

test that evaluates muscle tonus of the quadriceps.

Data obtained in this test present minimum

variability and high precision, require minimum

patient cooperation and, the most important, they

have significantly correlation with clinical results.

This test has been used to evaluate spasticity in

patients that presents hemiplegia, multiple sclerosis

and spinal cord injury and also to evaluate the

efficacy of antispastic drugs and muscle training

(Salmela et. al., 2002).

Electrogoniometers and tachometers were used

as instrumentations to pendulum test of spasticity

(Bajd and Vodovnik, 1984).

Procedure involving computerized video motion

analysis was applied as an alternative to goniometer

in pendulum tests (Stillman and McMeeken, 1995).

Linear accelerometers were used as an

alternative strategy to measure knee joint angle,

what allows unlimited movements of the patient

(Yakamoto et al., 2012).

Accelerometer was also combined to gyroscope

in the development of a motion sensor system, in

order to estimate joint moments in human dynamic

analysis (Liu et al., 2010).

Alternative tests are available also to upper limb,

as the use of a hand-held myotonometer for

measuring tone, elasticity and stiffness of the muscle

simultaneously, by applying a brief mechanical

impulse, followed by a quick release to the muscle

through acceleration probe (Chuang et al., 2012).

This project applies a common sensor (used in

motion analysis) to the original pendulum test: the

accelerometer. It provides information of thigh

tremor during the test execution.

As redundancy, one electrogoniometer is also

positioned in the patient to measure knee angle

during the balance.

CustomBuiltDeviceforSpasticityEvaluationAssociatedtoSpinalCordInjury-ARedundantSignaltoElectrogoniometer

inPendulumTest

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2 DEVELOPMENT

2.1 Transducers

2.1.1 Accelerometer

A piezoelectric accelerometer was chosen to

quantify thigh tremor. The ACH-04-08-05

Accelerometer Analog Test PCB (Measurement

Specialties, Inc., Norristown, PA, USA) used in this

system, presents adequate features for this

application. This unit consists of the ACH-04-08-05

accelerometer with thermal shield, a low-power

operational amplifier, resistors and capacitors that

provide signal conditioning (Figure1) (Measurement

Specialties, Inc., 2001).

Figure 1: ACH-04-08-05 Accelerometer Analog Test

PCB.

The accelerometer contains three cantilever

beams composed of a metal substrate with a

piezoelectric polymer element affixed to one side.

The beams are oriented to simultaneously measure

acceleration in three orthogonal, linear axes (X, Y

and Z). The X and Y axes are at a 45

angle relative

to the accelerometer package. Each beam is

supported at one tip while the opposite tip is free to

flex in response to acceleration. This flexion strains

the piezoelectric material that generates a charge

proportional to the applied acceleration. The

accelerometer responds over a frequency range from

0.3 Hz to 5.0 kHz, as a result of the integrated

electronics and the damped sensing elements. The

sensitivity of axes is 1.8 mV/g (Measurement

Specialties, Inc., 1998); (Measurement Specialties,

Inc., 1999).

The ACH-04-08-05 Accelerometer Analog Test

PCB provides three simultaneous analog outputs,

one for each axis. Moreover, the circuit has a gain of

47.8, a high-pass filter (0.34 Hz) and a low-pass

filter (185 Hz). The entire circuit requires +5 V

power supply and drains 13 μA for all three axes

(Measurement Specialties, Inc., 1998);

(Measurement Specialties, Inc., 2001).

Tremors, as vibration signal, are usually

composed of many frequencies that occur

simultaneously. Vibration amplitude can be

quantified in many ways: peak-to-peak level, peak

level and root mean square (RMS). RMS value was

chosen as an indicator because it shows the mean

energy contained in the vibration movement. It is

calculated according to the equation 1.

x...xx

RMS





(1)

RMS

is the effective value of the vector analyzed,

...x

are its values and N is the vector size.

2.1.2 Electrogoniometer

Goniometry is one of the most used techniques by

cinemetry, which allows the assessment of joint

range of motion, and the description and

comprehension of adjacent segments movement,

providing a quantitative analysis about pathology

and functional capacity rehabilitation (Esteves et al.,

2007).

The S700 Joint Angle SHAPE SENSOR

(Measurand, Inc., Fredericton, NB, Canada) was

used to measure joint angle. This transducer has one

degree of freedom and it consists of two cases

attached to both tips of a 200 mm vinyl-covered

metal cantilever (Figure 2). The cantilever has

plastic optical fiber along the length on both sides,

and the fiber is treated on one side to lose light

proportional to bending. Thus, the angle between the

two cases determines the amount of light traveling

through the fiber.

Figure 2: Electrogoniometer Shape Sensor S700 Joint.

One case contains the electronic circuit that

converts the light signal from the sensor to an

electrical output. The transducer output is centered

on 2.5 V (sensor is straight, for +5 V power supply

and 5 mA of current draw) and it is linear and usable

without further processing. The output range is ±1.0

V for an angle range of ±90

. The other case is used

for mounting (Measurand, Inc., 2001).

2.2 Hardware

Hardware was built based on data acquisition

BIODEVICES2013-InternationalConferenceonBiomedicalElectronicsandDevices

122

through a microcontroller responsible also for

analog to digital signals conversion, as well as their

transmission to a computer through serial

communication.

Figure 3: Global system diagram. Analog signal acquired

from the transducers is converted to digital signal by the

microcontroller and sent through serial communication to

the software in the computer.

Basically, the data acquisition unit consists of

PIC18F258 microcontroller (Microchip Technology,

Inc., Chandler, AZ, USA), MAX232 dual

driver/receiver (Texas Instruments, Inc., Dallas, TX,

USA), 9V battery as power supply with 5V voltage

regulator and support circuit for PIC (crystal and

capacitors).

An alternative way to the serial port

communication, not always available in many

computers, is the use of a USB-Serial converter

cable.

Figure 4: Complete system. Transducers, serial cable and

equipment.

2.3 Firmware and Software

The microcontroller acquires data from transducers,

realizes analog to digital conversion and sends these

data to computer via serial communication.

Libraries, corresponding to the PIC, USART, Timer,

A/D converter and delays, were defined in the

program of microcontroller; ports used and their I/O

functions were also set up, and timing and clearing

USART buffer functions were declared.

The software built to user interface was

developed in LabVIEW 8.6 (National Instruments,

Austin, TX, USA) platform, using graphical

programming called G language.

Figure 5 shows the data acquisition screen.

Transducers data are shown in real time during test.

Figure 5: Data acquisition screen.

The data is stored by an identification given to

the patient at the capture moment. Figure 6 shows

the screen where the user can see historical data.

Figure 6: Historical data screen.

The electrogoniometer can also be calibrated. To

this project, 180º corresponds to the leg completely

extended, and 90º to the end of the balance. A linear

equation is created using values acquired by the

system, making a relation to determine the angle.

Other way to calibrate is setting the coefficients

A and B of the equation. This mode is indicated

when the calibration equation of the transducer is

already known.

The accelerometer data are not converted to

engineering units because they are just used to

quantify the intensity of fractionated movement

patterns.

3 METHODS

Tests were performed at Laboratory of

CustomBuiltDeviceforSpasticityEvaluationAssociatedtoSpinalCordInjury-ARedundantSignaltoElectrogoniometer

inPendulumTest

123

Biomechanics and Rehabilitation of the Locomotor

System – UNICAMP, with spinal cord injured

patients (SCIs).

The SCIs volunteers are integrants of the

rehabilitation group that realizes treadmill gait

training with NMES. Tests were performed by two

patients (both legs), as presented in Table 1.

Table 1: SCIs volunteers characteristics.

Patient 1 2

Gender

Male Male

Neurological Lesion Level

C5 T3

Asia Scale

AIS C AIS A

The patient is positioned in supine position, in a

way that his leg may have free balance when

released. A triangular lumbar support (45°) is placed

under the patient to not induce spasticity.

As shown in Figure 7, the electrogoniometer is

positioned laterally to the patient’s leg and the

accelerometer, above the leg (quadriceps direction).

Figure 7: Sensors position.

At the beginning, the physiotherapist extends the

leg and released it, letting it falls freely until it stops.

Data are acquired and stored by the software.

Tests were performed three times consecutively

for each leg, before and after the treadmill gait

training with NMES.

4 RESULTS

For reference purpose, signals from healthy

volunteer were acquired (Figure 8). First graph

refers to the electrogoniometer signal, similar to a

damped pendulum movement during the balance,

presenting no abrupt signals or interruptions. Signals

from three axis of the accelerometer can be also

observed in Figure 8.

As a more quantitative way of interpretation,

RMS from each repetition is calculated. The mean of

the 3 axis are shown in Table 2. Values indicate few

thigh tremor during the balance.

Figure 8: Data from control patient.

Table 2: RMS values of reference signals.













0,16 0,16 0,07

SCIs test results are shown in Figure 9, before

training, and in Figure 10, after training.

Mean of the three repetitions (

RMSx





RMSy



, RMSz



)

of each leg was extracted in both

moments, before and after. Then the difference

between these two moments was calculated (Table

3).

Table 3: Differences of RMS mean values corresponding

to instants before and after treadmill gait training.

Patient Leg

∆



∆



∆



Left

2,22 1,23 2,44

Right

1,39 0,86 1,95

Left

18,63 10,86 8,03

Right

1,86 2,89 0,69

It is possible to observe that there is a

significantly decrease of RMS value in the three

axis signals of the accelerometer, when both instants

are compared.

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124

Figure 9: Data before training.

Figure 10: Data after training.

Measuring in three axis are made to improve the

spatial sense compared with the electrogoniometer.

Figures 11, 12 and 13 allow a visual

understanding of these data and make possible the

evaluation the redundance of the sensors when used

in pendulum test.

Besides that, it is possible to notice that instants

after the training, the movement tends to be similar

of a pendulum one, as occurs with the control signal

obtained initially. This means that the spasticity has

decreased significantly.

Figure 11: Angle x Vibration – Control signal.

Figure 12: Angle x Vibration – Before training signal.

Figure 13: Angle x Vibration – After training signal.

5 CONCLUSIONS

Along the study, the feasibility of the accelerometer

use in spasticity quantification was verified, since

the tremor is certainly present during the pendulum

test. Besides, it was possible to obtain RMS values

as parameters to quantify spasticity.

Electrogoniometer, usually used in pendulum

test, maintains its functionality as a redundant and

complementary signal.

However, in severe spasticity, as the

electrogoniometer signal does not allow parameters

calculation, due to irregular signal shape, the use of

signal provided by accelerometer is more

appropriate.

Future works are encouraged by adding new

accelerometers in different positions, proportioning

not only acceleration values, but also, velocity and

position.

CustomBuiltDeviceforSpasticityEvaluationAssociatedtoSpinalCordInjury-ARedundantSignaltoElectrogoniometer

inPendulumTest

125

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