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Disclaimer—This paper partially fulfills a writing requirement for first year (freshman) engineering students at the University
of Pittsburgh Swanson School of Engineering. This paper is a student, not a professional, paper. This paper is based on publicly
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ELECTROMYOGRAPHIC DEVICES: THE LINK BETWEEN PATIENT AND
PROSTHETIC
Joseph Sukinik, [email protected], Mahboobin 10:00, Alexander Meek, [email protected], Mena 3:00
Abstract—Currently 25-50% of all prosthetic limbs are
rejected by the user because they turn out to be more of a
burden than a blessing, and approximately 29% of limb loss
victims experience some symptom of significant depression.
In this paper, our focus will be the method of signal
transduction within the electromyographic (EMG) interface
of a prosthetic hand. EMG is required to carry out tasks such
as motor control and sensory perception in a way that feels
analogous to the user’s original hand. The EMG interface
works through electrodes placed on the surface of the skin
and aligned with the forearm flexor and extensor muscles.
The electrode detects action potentials from the nervous
system through varying degrees of muscle flexion, then
delivers a signal to the prosthetic, generating an action
ranging from wrist rotation to gripping objects. The interface
also receives stimuli from the prosthetic, which it returns to
the electrode as a new electrical stimulus to be relayed to the
brain as a sensation. A specific example of EMG technology
explored in this paper is the Mobius Bionics LUKE arm, the
first prosthetic arm to be approved by the FDA. This
technology will open new avenues for engineers and
researchers to learn how the human brain interacts with
muscles, and therefore allows us to design artificial limbs that
truly mirror the human body. Through this analysis, we hope
to demonstrate the ways in which EMG interface technology
in prosthetics can relieve amputees of their stress and pain,
and thereby offer them hope, independence, and a higher
quality of life.
Key Words— Electrode, Electromyography, Interface, Limb
loss, LUKE arm, Motor control, Prosthetic
ELECTROMYOGRAPHY AND THE ERA
OF ADVANCED PROSTHETICS
In the United States alone, there are about 1.7 million
people living with limb loss, and 185,000 additional
amputations occur each year according to the journal Amputee
Coalition [1]. Due to this vast number of amputees, interest in
prosthetics has also increased and what was once science
fiction is now becoming a reality. Over the course of the past
few decades, the field of rehabilitation engineering has begun
University of Pittsburgh, Swanson School of Engineering 1
Submission Date 03.31.2017
to flourish, with many incredible technological advancements
being created.
Bioengineers are striving to develop a prosthetic limb
that can function as capably as a natural limb – one that will
be able to grasp objects with varying tension while allowing
the user to feel sensation. Electromyographic (EMG) devices,
products that measure and interpret the brain’s electrical
signals through muscle tissue, offer an opportunity to make
this improvement a reality. Currently, prosthetics merely
serve to allow some semblance of a normal life; they are often
solid metal bars without any form of neural control. Without
sensation or function, current prosthetics often lead to
disappointment and disuse, sometimes causing the users to
develop depressive symptoms. EMG is a promising concept
due to the growing research on the human nervous system the basis of EMG technology. The goal of EMG devices is to
create a prosthetic limb that amputees will be eager to use by
increasing comfort, increasing control, and generating
sensation. The engineers behind the design of EMG
technology seek to provide a sustainable advancement within
the field of rehabilitation engineering, specifically for
prosthetic limbs. EMG will allow amputees to lead the same
lives that they did before the amputation, revolutionizing the
field of rehabilitation engineering and prosthetic devices,
reversing the negative effects of limb loss.
THE FOUNDATIONS OF EMG
TECHNOLOGY IN FOREARM
PROSTHETIC DEVELOPMENT
Redefining the Prosthetic
The field of rehabilitation engineering seeks to develop
better and more efficient methods and models to give injured
and disabled people their lives back. Prosthetic devices make
up one of the largest components of the field, including not
just limbs, but also cochlear implants and bionic eyes. For
decades, the general design of a prosthetic limb has remained
relatively constant, with most improvements being applied to
the materials of the limbs to make them stronger, more
durable, more comfortable, and more cost-effective. The first
prosthetic limbs, made from wood, date back as far as 300
Joseph Sukinik
Alexander Meek
BC. Over time, better and more durable materials like bronze,
iron, and steel were used in increasingly advanced designs,
improving the lives of limb loss victims [2].
However, the first truly modern prosthetic limb was not
created until the 1950’s, soon after the Artificial Limb
Program (a national initiative to design better prosthetics for
amputees) was founded in 1945 [2]. This prosthetic included
hydraulic systems that used pressure to generate motion in
joints. Today, prosthetics have a similar overall design,
however instead of wood and copper as in Figure 1 below,
they now use stronger mass-produced materials such as
aluminum, titanium, or even 3D-printed plastic polymers as
seen in Figure 2.
device. Implantable electrodes are placed surgically beneath
the skin, directly onto the nerves or onto the muscles,
providing direct contact to the source of the electrical signal
[5]. Each version has both advantages and disadvantages,
each designed to provide the highest quality of life such that
the technology can be sustainable in the long run. Implantable
electrodes can generate more accurate results than superficial
versions. This results in more precise motions for the
prosthetic, however they require surgical procedures, which
in turn demands high fees, increases potential health concerns
including tissue damage and infection, and requires future
surgeries to remove faulty electrodes [6]. EMG devices do not
have the same high efficiency of signal measurement and
interpretation; however, they do not require the high fees of
surgery or have the same health concerns, and are easily
removable.
Within the category of superficial electrodes, there are
two divisions: wet and dry. Wet electrodes that use Ag/AgCl
solution, such as those used clinically, are typically better at
conducting the electrical impulses from the nervous system
due to the high electrolyte concentration, and adhere very well
to the skin. However, despite decades of research, they lose
effectiveness over time, need to be constantly replaced, and
are quite uncomfortable when the use is mobile. On the
contrary, dry electrodes lie directly on the surface on the skin
without any type of conducting intermediary. As stated
previously, it is again not as efficient at signal reception, as it
registers slightly more “noise” from the surrounding tissue,
and is difficult to keep in one location, thus needing
“mechanical solutions” to keep it in place. Yet, traditionally
the dry electrodes provide more comfort and do not need to
be replaced [6]. Keeping all these comparisons in mind, this
paper will be focusing on EMG devices that utilize dry
electrodes for neural action potential reception for the forearm
prosthetic device.
FIGURE 1 [3]
Wooden prosthetic hand (1916)
THE UNDERLYING PROCESSES AND
MATERIALS OF EMG TECHNOLOGY
FIGURE 2 [4]
Modern prosthetic hand by BeBionic in England
Electromyographic devices depend on several key
bodily processes in order to function properly. These
processes can be narrowed down to two main body systems,
the nervous system, and the muscular system.
TheScientist.com defines electromyography as the reception,
measurement, and interpretation of electrical signals as
portrayed through muscle contraction and relaxation [5]. To
properly explain how EMG devices function, both processes
must be assessed in extreme detail, then apply them to the
specific materials used in EMG devices. This context will
then allow for the introduction of an example of an application
of EMG devices, the LUKE arm.
Neural interfacing is the most recent major development
in prosthetic development because it incorporates the user’s
own nervous system, utilizing electrical neural signals from
the brain to control the prosthetic instead of an external
source, such as a computer. By incorporating the brain into
the design of prosthetics, the user can finally treat the
prosthetic as their own.
Neural Interfacing: The Good, the Bad, and the Ugly
A superficial electromyographic (EMG) device is one
way to harness the user’s neural impulses. However, there are
other recent developments, such as implantable electrodes
that also allow for wireless neural interfacing for a prosthetic
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Joseph Sukinik
Alexander Meek
potential reaches the end of the neuron’s axon it releases
neurotransmitters that then drift across the gap and bind to
receptor proteins. These proteins change their orientation,
making gaps for sodium to flow in and reestablish an action
potential [12]. There are also types of neurotransmitters that
inhibit the transmission of the signal, preventing the signal
from traveling to the wrong location in the body. This ensures
that the impulses designated to move the muscle arrive only
at the muscle and initiate the action specified. Neuronal
transmission of electrical impulses drive muscle contraction,
and thus will drive the motion of the prosthetic.
Action Potential Development and Transmission
Every process in the body - the heartbeat, talking,
thinking, sensation, perception, digestion, breathing, and
motion – is controlled by the brain. Every single time a person
moves a muscle, that action must be processed by the central
nervous system (the brain and the spinal cord) before the
message can be sent to the muscle. Motion control is typically
centered in the cerebellum, the section at the base of the
occipital region of the brain [8]. It is here that action potentials
are typically developed to move each part of the body. An
action potential is an electrical impulse developed by a
chemical imbalance within a cell or series of cells. Each
neuron, while in equilibrium, is at resting potential and has
large quantities of potassium ions within the cell and sodium
ions outside the cell’s membrane. In order for an action
potential to be generated and maintained there must be an
imbalance of these ions. After a stimulus such as touch, sight,
or smell initiates an action potential, the cell membrane of a
neuron is depolarized, causing an influx of sodium ions,
further increasing the potential until it crosses the threshold
voltage. After the action potential passes, the cell’s resting
potential must be reestablished before another action potential
can be generated, thus there is a refractory period where no
other action potentials can be propagated. Figure 3
demonstrates the entire passage of an action potential by
graphing voltage vs time. It illustrates the effect that action
potentials are “all or nothing responses” and it is thus the
timing of the action potentials and the number of them that
determine the strength of the response in the muscle [9].
FIGURE 4 [11]
Diagram of a neuron
Myoelectric Contraction
Electromyography is the analysis of electrical impulses
produced by the nervous system through the muscles. In the
normal human body, muscles will receive hundreds of
impulses every second, causing it to contract or relax in very
small amounts constantly, regardless of whether the
movement is conscious or unconscious. Each and every
contraction is determined by an electrical impulse, the more
frequent the impulses, the more intense the contraction.
Intensity of muscle contraction also depends on the number
of signals, meaning that the higher the number of neurons
touching the muscle, the greater the contraction. In Figure 5,
a colored photo of the microscopic neuromuscular junction is
shown, depicting how each muscle cell is in contact with at
least one neuronal synapse.
Neuron
FIGURE 3 [10]
Action Potential diagram, independent variable is time,
dependent variable is voltage
The potential generated by the central nervous system then
begins to travel along the neurons (as seen in Figure 4),
jumping between synapses due to release of a
neurotransmitter called acetylcholine, which is also the
neurotransmitter that will later bridge the gap between the
nervous system and the muscular system. When the action
Muscle Cell
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Joseph Sukinik
Alexander Meek
The entire sEMG process hinges on being able to
seamlessly read and transfer signals from muscles underneath
the skin, and the key to this is maintaining “conformal
contact” between the electrode mesh and the skin. The mesh
must therefore be very thin such that it can morph to fit the
intricacies of the surface of skin, optimal levels have been
found to be between five and twenty-five micrometers thick.
Fibers of this size are printed directly onto the skin via a
stamp, as opposed to the conventional method of using flat
adhesive pads with conductive gels. However, since the EES
is more “exposed” in this method, it requires the use of
“biocompatible, non-corrosive, electrochemically stable
materials that resist surface oxidation” [16]. Gold, therefore,
works very well and is the standard material of choice for use
in signal translation.
Surface EMG sensors must integrate hard electrode
materials and softer supporting materials to be able to
function successfully despite the flexing and stretching of the
surface of human skin. Because of this requirement, the
materials and structure of the sensor becomes integral to the
success of the prosthetic device.
Beyond the material component of the electrode,
engineers also need to consider where electrodes should be
located on the user to achieve optimal signal reception and
interpretation. Generally, hand motions can be broken up into
four pairs of motions: “grasp-release, left-right, up-down, and
rotate” [17]. In order for a prosthetic hand to function as well
as the original hand, it needs to be able to perform each
motion, meaning that each of the muscles that cause these
actions must be accounted for. In the table below, Figure 6,
each muscle in the forearm is identified, as well as the action
it is responsible for performing.
FIGURE 5 [13]
Visual of neurons directly interacting with muscle cells.
When the action potentials arrive at the muscle cell, they
must first bridge the synapse between neuron and muscle cell
via acetylcholine, the same neurotransmitter that allowed the
signal to jump between neurons. When acetylcholine reaches
the cell membrane of the muscle, it binds to post-synaptic
proteins, allowing an influx of sodium ions, which generates
an electrical imbalance inside of the muscle cells [14]. As the
electrical signal travels down the length of the muscle,
portions of the current will diverge down the rows of muscle
cells in order for the signal to reach the entirety of the muscle.
Each row of muscle cells contains thick protein bundles called
sarcomeres. Each sarcomere contains protein filaments called
actin and myosin, the proteins that will subsequently generate
a muscle contraction. Myosin is a thick protein strand (also
called a filament) that when electrically stimulated, begins to
pull thinner actin proteins together, a process deemed the
Sliding Filament Theory of Muscle Contraction. Nature
Journal describes the Sliding Filament Theory as if one was
“given the task of bringing two bookcases together, [but are]
limited to using only [their arms] and two ropes” [15]. Muscle
contraction occurs a very small portion at a time, and
depending on the strength of the electrical signal, the myosin
will continue to cycle through pulling actin, releasing, and
pulling again. Microscopic contractions occur throughout the
entire muscle, and by adding every tiny contraction then
overall a muscle contraction would be developed. If the
electrical signal is consistently reapplied then the contraction
is sustained, however, if the action potentials are ceased, then
the myosin can detach from the action and the muscle will
quickly relax and elongate.
The goal of myoelectric devices is to register the
frequency and number of action potentials, and then interpret
them in the same way that sarcomeres do. EMG devices aim
to replicate muscle contraction and relaxation such that there
is virtually no difference in the motion of a prosthetic limb
and a human limb.
1
2
3
4
Muscle
Brachioradialis
Extensor carpi ulnaris
Pronator teres
Electrodes: How to Make Them and Where to Put Them
5
Extensor communis
digitorum
Flexor carpi radialis
Due to the very sensitive nature of myoelectric
sensation, many factors influence the transmission of accurate
signals from the electromyographic sensors to the prosthetic
and back again. Issues like electrical noise and crosstalk
contamination are magnified in surface electromyographic
(sEMG) interpretation, so designers must therefore pay even
more attention to defining features of sensor design like
electrode size, shape, and layout. EMG sensors employ a class
of technology referred to as epidermal electronic systems
(EES) to interface with the skin and read and amplify the
recorded signal. The interface is a system of very thin
interconnected mesh of gold wires and electrodes that are
placed in direct contact with the skin and surrounded with
polyimide to “mitigate bending stresses in the metal” [16].
6
Anconeus
7
Pronator quadratus
Function
Forearm flexion
Extension of arm at wrist
Forearm rotation and elbow
flexion
Finger and wrist extension
Hand flexion and rotation at
wrist
Resistance of forearm
rotation
Initiates rotation
FIGURE 6 [17]
Table of forearm muscles and their functions
EMG electrodes must be placed on each of these
muscles to ensure that the prosthetic carries out the designed
actions to the same extent that the original hand would have.
Additionally, a study conducted by the Institute of Electrical
and Electronics Engineers (IEEE) determined that as the
number of electrodes increased, the clarity of the signal also
increased; however, there is a limit to how close these sensors
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Joseph Sukinik
Alexander Meek
can get without picking up conflicting signals [17]. If they are
placed too close together, the crosstalk could cause an
inaccurate pressure signal to be transferred to the prosthetic,
which might then cause the hand to crush a delicate egg, or
drop a heavy hammer. The most responsive and accurate
prosthetics must combine sensitive electrode design, such as
gold nanofiber mesh, with precise electrode placement to
achieve the highest level of superficial electrical signal
reception.
react to get feedback, they can make quicker adjustments to
their original input, allowing for greater precision. This
method demonstratively outperformed the force feedback
method in the German study when it came to applying an
appropriate grasping force to an object [19].
The Future is Now: The LUKE arm
The Mobius Bionics LUKE arm, funded by the Defense
Advanced Research Projects Agency’s (DARPA)
Rehabilitation Research and Development Service and
formulated by DEKA Research Group, is one of the most
advanced upper arm prosthetics in the industry today, as seen
in Figure 7. It is the first upper arm prosthetic to be approved
under the FDA’s new category for integrated prosthetic arms
and offers users a variety of ways to control the arm’s 10
powered degrees of freedom [20,21].
Creating a Capable Prosthetic
While it can be difficult to read and interpret electrical
signals from upper arm muscles, it can be nearly as
complicated to design a prosthetic arm device that can
perform the complex motions necessary to carry out everyday
tasks. Even something as simple as turning a doorknob
involves a complicated array of finger positions and grasping
strengths. It is therefore critical that the patient can control the
prosthetic to a high degree of precision and accuracy. Sensory
feedback is widely regarded as the avenue by which this
necessary level of control can be attained [18,19].
Sensory feedback is the concept of relaying electrical
impulses from the fingers of a prosthetic device back to the
brain as perceived touch, thereby giving the user a heightened
sense of control and feel for the amount of force they are
applying through the prosthetic. There are multiple ways to
generate this signal, namely contact-driven feedback or
“control input” feedback. A study by a team of German neurorehabilitation researchers demonstrated that the “control
input” method offered improved grasping performance over
force feedback.
The force feedback loop relies on force sensors on the
tips of fingers in the hand for the sensation of touch, giving
feedback in the form of electrical impulses about how firmly
the prosthetic is grasping an object. This method, while
successful, is limited because the user can only make proper
adjustments to grip strength once the hand has made contact
with the object. Some prosthetic researchers have tried to
couple force sensation feedback with a velocity or position
sensor to give the user more information about the action of
the device, but these methods have been found to be
inconsistent and restrictive [19]. Essentially, a prosthetic that
employs the force based sensory feedback system will be
favored over a system with no feedback, but the user will still
have to tediously monitor the motions and closing speeds of
their hand while grasping and picking up objects.
On the other hand, the EMG interface can be used to
provide feedback in a more predictive manner. Instead of a
signal being relayed when the prosthetic makes contact with
an object, the EMG feedback transmits signals that convey the
user’s input strength, which allows the user to predict how
strongly the prosthetic will react to their input. This method is
considered “out of the loop” of the prosthetic because it does
not consider the actions of the prosthetic, only the input of the
user. Since the user does not have to wait for the prosthetic to
FIGURE 7 [21]
LUKE arm holding a grape
This arm’s control system is fairly unique in the way that
it can incorporate multiple sensors and pieces of equipment to
offer the best control for the patient. The hand can be oriented
to preset positions using a foot inertia sensor if desired,
however the main control still operates through the EMG
electrodes, and the fully realized EMG sensor is what makes
this arm the most capable on the market for wounded warriors
and amputees alike. Users can control the flexion and force of
individual fingers and an opposable thumb, allowing them to
create grip orientations that fit the object they are trying to
pick up, move, or turn [21]. This technological development
is a huge step towards eliminating the restrictions and
limitations that amputees face daily in everyday tasks.
Although this device has yet to be released for purchase,
initial reviews by trial amputees have been very positive, with
one user saying simply, “It works the way the patient thinks”
[22]. This device is the closest developers have come to
creating an arm equally as capable as a human arm. For this
reason, the military has placed its funding behind the LUKE
arm’s development, realizing the importance of restoring a
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sense of being and self-sufficiency to limb-loss victims,
hoping to serve those their soldiers just as they served their
nation, giving them back their lives and happiness [23].
Losing one’s independence can be devastating, however with
this new development in prosthetic design, many amputees
may finally be able to get that independence back.
have traumatic injuries might be seen as fortunate or lucky”
[25]. Those who can afford the surgeries for new prosthetic
limbs will do so, to be better than they were before. The future
of neural prosthetic limbs has its potential drawbacks,
however, in the short run, the benefits for those suffering from
limb loss far outweigh the drawbacks.
THE ETHICS OF PROSHETICS
HOW EMG IS MAKING AN IMPACT ON
THE AMPUTEE COMMUNITY
A Luxury Item
A Sustainable Solution
When discussing a new technology, it is imperative to
assess how the technology could have negative consequences
in the future. For neural prosthetics, those negative
consequences include high costs and a potential for personal
improvement. When a new product enters a market, or a
product considered to be a luxury item, the price is typically
high until the product can be mass-produced. Neural
prosthetics that allow for brain-interfacing run the risk of
being priced very high. One man, Bertolt Meyer, received the
newest technology, however he realized he was one of the
lucky ones, stating:
“Soldiers who lose limbs while serving get the latest
technology, but civilians who lose an arm in a car accident
only receive my pre-2009 version through their insurance. A
14-year-old one-armed boy who had his application for [a
new prosthetic] turned down by the NHS recently ended up
offering the surface of his prosthesis as advertising space to a
Formula 1 racing team to obtain funding” [24].
As the current model for the prosthetic arm is updated,
the potential for appealing to a single social class becomes
more likely, as seen with the fourteen-year-old boy. This
demonstrates the potential for prosthetics to develop new
social classes within the amputee population. People who
cannot afford the newest technology would be forced to use
older versions, meaning they would have a lower quality of
life.
Sustainability is crucial for all engineering fields, as it
weighs both the benefits and consequences of designing a new
technology and then providing it to the public. For medical
devices, sustainability directly refers to an increase in quality
of life. The goal of designing a neural prosthetic device, as
opposed to non-interfaced prosthetics, is to improve the
quality of life for those living without one or more limbs. In
this sense, EMG will be sustainable in the market due to its
inherent ability to give back use of a limb. The positive effects
include decreasing pain, increasing mental health, and
increasing physical prowess.
An important aspect to consider when evaluating the
value of a prosthetic model is how well the actual amputees
receive the technology. There are several components to
address when designing a prosthetic for upper-arm amputees,
from phantom limb pain to range of motion, and the better the
prosthetic can meet these needs, the more likely it is to be
well-received by the amputee. An ideal neural prosthetic
device should allow an amputee to do simple and complex
tasks just as well as anyone else, giving them the opportunity
to live the lives they led previously, subsequently with a
higher quality of life. High quality prosthetics like the LUKE
arm are designed to mimic the function and feel of an actual
human limb as closely as possible, and EMG represents a
great avenue to do this.
Stronger, Faster, Better
Relieving Invisible Pain
What happens when prosthetics begin to outperform the
body? As prosthetics continue to be able to read the neural
impulses better and better, prosthetic devices grow closer and
closer to functioning the same as the original. What if in the
pursuit of perfection, engineers develop prosthetics that
ultimately work better than the natural body? While this may
sound extreme, it is comparable to modern plastic surgery,
where those who have money can use cosmetic technology to
improve their appearance beyond natural standards.
When this point is reached, there is a possibility that
people may begin to seek personal augmentation, meaning
self-improvement through prosthetics. The Institute for Ethics
and Emerging Technologies (IEET) discusses how if this
occurs, people may elect to amputate their own limbs to
receive a new prosthetic. They also consider how “those who
One of the most common afflictions for amputees is
phantom limb pain, which affects up to 45% of all amputees
[18]. Phantom limb pain occurs when a person feels pain in
an absent limb due to a neurological nerve error, and it is very
hard to treat with therapy or painkillers. When a limb is
severed, the nerve center in the brain that was responsible for
that limb becomes inactive. Dr. Thomas Weiss, who led an
EMG research study at Friedrich-Schiller University, stated
that “these areas take over the processing of sensory stimuli
from other body parts, especially the arm stump and the face”
which leads to the intensified sensations of phantom limb pain
[18]. EMG technology helps address this complicated issue
by allowing for bio-sensory feedback to be parlayed from the
prosthetic to the brain in a way that was impossible before,
which re-establishes a sensory connection with the inactive
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Alexander Meek
areas of the brain. The conclusion of the Friedrich-Schiller
study states that a “prosthesis with a feedback function
appears to be a promising therapeutic tool to reduce phantom
limb pain and to increase functionality in everyday tasks”
[18]. By establishing this connection and relieving the
amputee of their pain, more of the world is open to them, they
can go out and do more without the fear of being crippled by
pain.
struggle to live a normal lifestyle. The field of rehabilitative
prosthetics is trying to find a way to restore independence and
confidence to these amputees. Prosthetic arms that integrate
electromyographic sensors seem to be a viable way to do this.
EMG’s ability to connect patient and prosthetic
neurologically is vital to a successful integration of the
prosthetic into the amputee’s lifestyle. The contractions of
forearm muscles are read by carefully placed electrodes on
the surface of the amputated limb, and translated into
corresponding motions of the prosthetic. A key component of
this system is the magnitude of the grasping force of the
prosthetic hand, which can be monitored and adjusted by the
user based on the sensory feedback that is relayed back
through the EMG sensor. This feedback is also a critical part
of making the prosthetic feel more like an actual arm, which
then increases the rate of retention among users. Through the
process of neural interfacing, EMG can produce sustainable
solutions to phantom limb pain and mental diseases such as
depression, granting those with neural prosthetics an
opportunity for a better life, one that they want to live, for an
even longer period of time. Prosthetic arms have developed
from being immobile, wooden stand ins to becoming nearly
full-functioning replacement limbs, and they are only getting
more advanced. EMG and research groups like DEKA, with
the LUKE arm, are paving a golden age of prosthetics, and
shining a light that will surely brighten the lives of amputees
everywhere.
Restoring Touch, Restoring Life
Being able to perform everyday tasks without too much
added difficulty is extremely important in amputees’ efforts
to live normal lives. Sensory feedback plays a large role in
restoring this normal because of how important relative grip
strength is to picking up and grasping objects. Providing
feedback to the subject through the surface EMG interface
during the process of grasping an object (online closed-loop
force control) significantly increases their ability to apply the
appropriate amount of force through the prosthetic and make
real-time adjustments to this applied force [19]. FriedrichSchiller’s study describes exactly why this is such an
important detail for the amputee:
“Subjects developed significant skills for manipulating
soft or fragile objects with the prosthesis and reached several
personal goals in the use of the prosthesis. The study results
underline the principle that a myoelectric prosthesis providing
sensory feedback about grip strength might be
advantageous… The somatosensory feedback of our
prosthetic system might ease the usage of prostheses in
everyday life, which, in turn, might lead to a higher
acceptance of wearing prostheses on a long-term basis. The
increased bilateral use of both upper extremities might also
reduce the load on the non-amputated body side. Reducing
excessive strain on the healthy side of the body may lead to
less pain in the non-amputated limb and in the back” [18].
With 35% of the 1.7 million amputees in the US
currently suffering from Major Depressive Disorder (MDD,
national rate 6.7%), it is vital that every possible step is taken
to improve their mental state [26,27,28]. Many factors
contribute to this elevated rate of depression, including the
inability to find work, a dislike of increased dependency, and
a decrease in social interaction. EMG technology cannot
completely absolve the issue [26]. However, a prosthetic that
is able to model a human arm significantly better than past
models can be a meaningful step forward for those suffering
from a lowered sense of self-importance due to their
disability.
SOURCES
[1] “Limb Loss Statistics.” Amputee Coalition. 2017.
http://www.amputee-coalition.org/limb-loss-resourcecenter/resources-by-topic/limb-loss-statistics/limb-lossstatistics/. Accessed 2.27.2017.
[2] “Atlas of Limb Prosthetics.” Digital Resource Foundation
for the Orthotics and Prosthetics Community. 1992.
http://www.oandplibrary.org/alp/. Accessed 2.22.2017.
[3] M. Bellis. “A Brief History of Prosthetics.”
About.com.
http://inventors.about.com/od/timelines/fl/ABrief-History-of-Prosthetics.htm. Accessed 2.23.2017.
[4]
“The
Hand.”
beBionic.
2017.
http://bebionic.com/the_hand. Accessed 2.23.2017.
[5] E. Leuthardt. “Neuroprosthetics.” The Scientist.
11.1.2014.
http://www.thescientist.com/?articles.view/articleNo/41324/title/Neuroprost
hetics/. Accessed 1.9.2017.
[6] E. Klein, J. Ojemann. “Informed consent in implantable
BCI research: identification of research risks and
recommendations for development of best practices.” IOP
Science Journal of Neural Engineering. 6.1.2016.
http://iopscience.iop.org/article/10.1088/17412560/13/4/043001/meta. Accessed 2.24.2017.
[7] Y. Chi, T. Jung, et al. “Dry-Contact and Noncontact
Biopotential
Electrodes:
Methodological
Review.”
2010.
ELECTROMYOGRAPHY: A SECOND
CHANCE AT NORMAL
Whether they lost a limb traumatically or were born
without it, amputees lead a difficult life. Many suffer from
depression, often require assistance with basic tasks, and
7
Joseph Sukinik
Alexander Meek
force.” IOP Science Journal of Neural Engineering.
8.22.2016.
http://iopscience.iop.org/article/10.1088/17412560/13/5/056010/meta;jsessionid=83FDE47C4FA7DFF94
5E2677E9445819A.c1.iopscience.cld.iop.org.
Accessed
2.26.2017.
[20] “Mobius Bionics bringing DEKA’s LUKE prosthetic
arm to market.” Today’s Medical Developments. 7.12.2016.
http://www.todaysmedicaldevelopments.com/article/mobiusbionics-deka-luke-prosthetic-arm-dean-kamen-71216/.
Accessed 2.26.2017.
[21]
“LUKE
Arm.”
MOBIUS
bionics.
http://www.mobiusbionics.com/the-luke-arm.html. Accessed
2.26.2017.
[22] R. Boyle, B. Draxler. “DEKA “LUKE” ARM.” Popular
Science. 2014. http://bestofwhatsnew.popsci.com/deka-lukearm. Accessed 2.26.2017.
[23] N. Hines. “Mobius Bionic's LUKE Arm Is Straight Out
of 'Star Wars'.” Inverse Innovation. 7.11.2016.
https://www.inverse.com/article/18100-mobius-bionicsluke-sprosthetic-arm-commercially-available-approved-forsale-darpa. Accessed 2.26.2017.
[24] B. Meyer. “Bertolt Meyer: 'Ethical questions are looming
for
prosthetics'.”
Wired.
8.30.2013.
http://www.wired.co.uk/article/now-we-need-to-talk-aboutour-bionic-future. Accessed 3.1.2017.
[25] J. Niman. “Prosthetic Technology and Human
Enhancement: Benefits, Concerns and Regulatory Schemes
Pt3.” Institute for Ethics and Emerging Technologies.
5.9.2013. http://ieet.org/index.php/IEET/more/niman201305
09. Accessed 3.1.2017.
[26]
“Amputation
and
Depression.”
LifeTips.
http://disability.lifetips.com/tip/150808/amputee/amputee/a
mputation-and-depression.html. Accessed 2.26.2017.
[27] “Amputation Statistics.” Statistic Brain Research
Institute. 9.2.2016. http://www.statisticbrain.com/amputeestatistics/. Accessed 2.26.2017.
[28] “Depression Statistics.” Depression and Bipolar Support
Alliance.
6.2005.
http://www.dbsalliance.org/site/PageServer?pagename=educ
ation_statistics_depression. Accessed 2.26.2017.
http://www.isn.ucsd.edu/pubs/rbme10.pdf.
Accessed
2.24.2017.
[8] “Anatomy of the Brain.” American Association of
Neurological
Surgeons.
2006.
http://www.aans.org/Patient%20Information/Conditions%20
and%20Treatments/Anatomy%20of%20the%20Brain.aspx.
Accessed 2.25.2017.
[9] S. Saddow. “Silicon Carbide Biotechnology: A
Biocompatible Semiconductor for Advanced Biomedical
Devices
and
Applications.”
2012.
https://books.google.com/books?id=NLLr5vxm_MC&pg=PA283&lpg=PA283&dq=neural+reception+b
y+interface&source=bl&ots=aRNoWG4h6l&sig=YcZc6ZR
FCAybRUEZJptPAW0X47k&hl=en&sa=X&ved=0ahUKE
wiCpo3Kh7jRAhWBhZAKHfacB5cQ6AEIHDAA#v=onep
age&q=neural%20reception%20by%20interface&f=false. A
ccessed 2.7.2017.
[10] “Neurons, Brain Chemistry, and Neurotransmission.”
National
Institutes
of
Health.
https://science.education.nih.gov/supplements/nih2/addiction
/guide/lesson2-1.html. Accessed 2.24.2017.
[11] “Neuron Anatomy.” Arizona State University.
https://askabiologist.asu.edu/sites/default/files/resources/arti
cles/neuron_anatomy.jpg.
[12]
“Synapses.”
McGill
University.
http://thebrain.mcgill.ca/flash/i/i_01/i_01_m/i_01_m_ana/i_
01_m_ana.html. Accessed 2.24.2017.
[13]
“Histology
@Yale.”
Yale
University.
http://medcell.med.yale.edu/histology/muscle_lab/neuromus
cular_junction.php. Accessed 2.28.2017.
[14] B. Hughes, L. Kusner, et al. “Molecular architecture of
the neuromuscular junction.” National Institutes of Health.
4.2006. https://www.ncbi.nlm.nih.gov/pubmed/16228970.
Accessed 2.24.2017.
[15] J. Krans. “The Sliding Filament Theory of Muscle
Contraction.”
Nature.
2010.
http://www.nature.com/scitable/topicpage/the-slidingfilament-theory-of-muscle-contraction-14567666. Accessed
2.25.2017.
[16] J. Jeong, W. Yeo, et al. “Materials and Optimized
Designs for Human-Machine Interfaces Via Epidermal
Electronics.”
Advanced
Materials.
9.25.2013.
http://onlinelibrary.wiley.com/doi/10.1002/adma.201301921
/full. Accessed 1.24.2017.
[17] P. Shenoy. “Online Electromyographic Control of a
Robotic Prosthesis.” Bioengineering Department. University
of
Washington.
3.2008.
http://homes.cs.washington.edu/~rao/emg-08.pdf. Accessed
1.10.2017.
[18] C. Dietrich, K. Walter-Walsh, et al. “Sensory feedback
prosthesis reduces phantom limb pain: Proof of a principle.”
ScienceDirect
Neuroscience
Letters.
http://www.sciencedirect.com/science/article/pii/S03043940
11014807. Accessed 2.26.2017.
[19] M. Schweisfurth, M. Markovic, et al. “Electrotactile
EMG feedback improves the control of prosthesis grasping
ADDITIONAL SOURCES
B. Darnall, P. Ephraim, et al. “Depressive symptoms and
mental health service utilization among persons with limb
loss: Results of a national survey.” Science Direct. Archives
of Physical Medicine and Rehabilitation. 4.2005.
http://www.sciencedirect.com/science/article/pii/S00039993
04013164?np=y Accessed 1.9.2017
“Once more, with feeling.” The Economist. 10.11.2014.
http://www.economist.com/news/science-andtechnology/21623580-artificial-limbs-feel-real-thing-aregetting-closer-once-more Accessed 1.9.2017.
8
Joseph Sukinik
Alexander Meek
H. Uliam Kuriki, F. Micolis de Azevedo, et al. “The
Relationship Between Electromyography and Muscle Force.”
Univ.
Estadual
Paulista.
2012.
http://cdn.intechopen.com/pdfs/25852.pdf.
Accessed
1.23.2017.
ACKNOWLEDGMENTS
We would like to thank our co-chair Mikayla Ferchaw
for peer-reviewing our paper throughout the writing process
and for providing critical feedback that guiding our writing
efforts. We would also like to thank Janet Zellmann for
providing extensive feedback on each of our submissions that
helped shape our paper and grow as writers and engineers. We
would also like to thank the members of Floor three
Sutherland West for proof-reading and offering their support
during the writing process.
9