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Verma 1
Ankush Verma
IR/3/10H3/27/2017
3D PRINTED PROSTHETICS: A NEW GENERATION
ABSTRACT
3D Printing and Robotics have the ability to revolutionize the medical industry if they are
combined together. A foot prosthetic that combines both 3D printing and Targeted
Muscle Reinnervation is the pivoting point for this idea to occur. Indubitably, this
prosthetic can be used to solve issues in low-income areas, as it would be relatively
inexpensive. The robotics portion of the prosthetic is able to develop with a child, similar
to how a normal foot would. This eliminates the issue of multiple prosthetics over the
course of multiple years, as limbs change. This would be done through a simple Java
program that automatically extends a metal piece out, expanding the length and width of
the foot.
MAIN BODY
Robotics has made a huge impact in the medical industry. There have been
major breakthroughs within this industry, for example, surgery with robotics as well as
robotic prosthetics, 3D printing, 3D printed prosthetics, which has been around for quite
a long time. Many prosthetists have created expensive robotic arms that have movable
fingers and others have created cheaper, 3D printed arms which have movable fingers.
The issue is the integration of both ideas, as many issues can branch off based on the
price of the prosthetic or whether the prosthetic would work or not. A innovative solution
would be to create a prosthetic for the foot, as that is an area that is currently not being
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extensively researched upon, which can move around; develop along with the child,
effectively lowering the cost; and combine both 3D printing and robotics.
There has been an issue regarding the price of the prosthetic for a foot. This has
been solved for the hand. A few years ago, a group of college students set out to create
a robotic arm, formally named the “Cyborg Beast,” for those who lacked a prosthetic.
The contraption created was inexpensive and could perform the assigned job of a hand,
as that is what prosthetics are made for. Two mechanisms that were used were ones
that would easily move the fingers and the 3D printed parts. The prosthetic was created
in a Computer Aided Design (CAD) program and printed on a MakerBot. The students
also described how the Targeted Muscle Reinnervation functions were high on
maintenance, as it is a robotic piece and can be destroyed easily, especially in a low-
income area where the conditions are not well. This resulted in the exclusion of it from
the project (Zuniga et. Al. 2015).
The mechanism for the fingers were an elastic cord. They are low-cost and easy
to manage, as well as they can sustain longer than a rubber band. This user-friendly
design makes it an indispensable apparatus to be included in any cheap prosthetic. An
example of the cord is shown in FIG 1. The prosthetic had the ability to switch parts at
ease if one were to break.
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FIG 1: E-NABLE created a 3D prosthetic hand that is very much comparable to
the prosthetic created by the students.
For a place to attach the rubber band mechanism, the 3D printed parts must be
designed and printed. The CAD program used to design the prosthetic was called
Blender. It is quite difficult to use for CAD purposes, as the interface is not as
straightforward compared to traditional programs and it is generally used for animations.
A better alternative would be an open-source program named Libre-CAD. Libre-CAD is
a straightforward conceptual designer used to design 3D parts, as well as it is designed
for CAD creation only. The limiting factor of the CAD program is that the creation of any
corporeality in the program must be able to convert to a .STL file, which is the most
common file for 3D printers. (Zuniga et. Al. 2015)
The students who created this project chose to exclude the Targeted Muscle
Reinnervation, which deals with the rerouting of nerve cells to allow for movement of the
limbs (See page 4), idea completely as it would be difficult to manage, as the living
conditions are low-end. These types of prosthetics do not have anything protecting it,
causing the item to be destroyed easily if not managed properly, as the conditions in
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poor areas are not great. A strong 3D printed carbon fiber prosthetic casing must be
used for greater durability. Another issue would be the high cost of a replacement as
certain parts cannot be taken apart, rather the whole conceptually designed article must
be removed. The solution to this would be to minimize the TMR idea to a small space
and make most of the prosthetic out of 3D printing. This allows for the ease of
modularity, which makes the prosthetic significantly, or eloquently, cheaper.
The problem with prosthetics, including the Cyborg Beast, is that they cannot
develop, or grow the way a human foot grows. For this to happen, the prosthetic must
be able integrate Targeted Muscle Reinnervation and an array that is to be attached,
which would be coded with a coding language called Java. Java is a field that scientists
argue should be well-taught and generalized in this current era (Vee). It is important to
implement it into such an article for outcome of teaching people Java and coding
overall. Since the focus of the research deals with the foot, not the hand, at ages 5-10, it
will be required that there is a mathematical formula in the code that can determine how
much the prosthetic foot should extend over a certain period. For example, at the age of
5, the foot “will grow rapidly” and there will be a ½ size increase every 4 months.
Afterward, there will be a difference in the growth, either growing at a faster or slower
rate. This would require the formula to determine the certain length based on the age,
gender, and current size. It will be straightforward in the implication that the width will
stay proportional to the length. Essentially, the Java code will be setup and the numbers
must be plugged in. A more visual aspect of the growth and proportionality is shown in
FIG 2. The formula would be created using the chart mentioned below.
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FIG 2: The CDC released a graph of child growth from ages 2-20, where the
focus would be from 5-10 years of age.
From thereon, the code will be installed on an array. The “experimental field
programmable analog array” (Toreyin and Bhatti 2013) would be installed within the
Targeted Muscle Innervated part itself. This portion will be both 3D printed and metal,
as the TMR requires metal, to make it both cheap and effective. The array would
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process the information and move the motors, to indispensably create a real-life
situation of a growing foot in a robotic format.
It is a stipulation that such a code and array would be added. The child needs to
initiate and instigate the prosthetic at age 5 as that is when the foot begins growing
expeditiously. The prosthetic can also maintain a cheap functioning motor for a long
interval, therefore saving the prosthetic and making it last.
The part that the array for coding purposes would be attached to is the TMR. The
Prosthetic will be split up into two different parts, one for the TMR portion which allows
for coding to be possible and plausible, and the other being the 3D printed part, which
makes the prosthetic cheaper compared to metal.
Targeted Muscle Reinnervation, created by Dr. Todd Kuiken in the early 2000s,
is a relatively new way to create advanced prosthetics. It deals with rerouting a nerve
cell of an amputated limb, which has been dysfunctional, to another spot. The nerve
cells would be fired thereafter and it would be sent to the TMR prosthetic. The process
can be summed as the “[transferring of] residual arm nerves to alternative muscle sites”
(Kuiken et. Al. 2009). This part of the prosthetic would allow for the child to move their
foot and toes. To make the prosthetic grow, it must be programmed. Programming will
be achieved through an array installed within the Targeted Muscle Reinnervation portion
of the foot. An experimental field programmable analog array must be installed to make
this work. There would be a “signal processing circuitry [which] generates a non-linear
signal that codes angular velocity into a pulse rate for a single SCC” (Toreyin and Bhatti
2013).
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One of the 3D printed portions is the socket for the prosthetic itself. For this to
occur, the residual ankle muscle must be scanned using “3D laser scanning…combined
with rapid prototyping” (Mavriodis et. Al 2011). The 3D scanner scans and creates a
socket for the residual ankle for the Prosthetic to be attached to, with space for the TMR
part to be attached. Through this, the child can seem comparably normal when walking.
This idea would be important as prosthetic hooks “have a high rejection rate, in part due
to an unacceptable cosmetic appearance” (Zuniga et. Al. 2015).
Unequivocally, 3D printing must be integrated into another portion of the TMR
prosthetic, rather than the socket part itself. Through this, the price can effectively be
decreased. If the two parts are kept separate, the price will be much higher than before.
An example to support this is if the 3D Printed Part costs $40 and the TMR part costs
$40 by themselves rather than half and half of both parts. Past prosthetic models have
chosen to either be 3D printed or made from metal. The prosthetic should be
inexpensive as well as develop, include the TMR and the array attached to it. This is
where the 3D printing and TMR combination arises, as the example above details that
the price would significantly decrease.
How the Prosthetic Functions ( See FIG 2 for CAD Example)
This Prosthetic will function differently compared to traditional prosthetic, as there is the
combination of both 3D printing and TMR included within this part itself, the amputated
area will be scanned and measured to find the right size for the socket. The socket of
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the prosthetic is where the prosthetic itself can easily be attached and changed in case
something was to happen to the part overall. The Prosthetic will have a socket, the part
that attaches to the socket, and the ankle as 3D printed. The rest of the part, from the
ankle to the toes, will be a combination of 3D printing and Targeted Muscle
Reinnervation. The toes, for example, would be 3D printed as it would cost a great
amount of money to apply a motor for each.
FIG 2: 3D CAD Example (Created in Microsoft 3D Builder)
Experimental Procedure
The procedure for the experiment is as follows:
1. Create a 5 in (127 mm) Carbon Fiber foot prosthetic parts in Autodesk inventor, begin with toes, then the toe mounds, the metatarsals, and the remaining foot from the front of the foot to the ankle/socket. Leave open areas on the side and the front so the foot can extend its length and width
2. Assemble 3D printed parts together in an Inventor Assembly, with the extra space inside of it for the mock Targeted Muscle Reinnervated part.
3. Use Stress analysis that measures displacement to identify how strong the pros-thetic is
4. Apply weights ranging from 0 Newtons to 100 Newtons5. Record the data regarding whether the prosthetic could handle the weight, and
the measurements of displacement of the prosthetic. 6. Repeat steps 4-5. 7. Analyze this data in paragraph and graph format.8. Write a Conclusion ending the experiment.
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9. Present the Data and Experiment to classmates as well as a prosthetist. Record Critiques or feedback.
10.Repeat the experiment per the Critiques or feedback received. If continuing, 3D print a full scale prosthetic prototype as well as work on a Bluetooth version of Targeted Muscle Reinnervation.
*Note-This is only a prototype and is simulated in a Computer Aided Design Pro-gram
There were also certain parameters that were required to be followed for this
experiment. These parameters are:
Must be able to develop employing the use of a Targeted Muscle Reinner-
vation system to control the prosthetic foot and the toes.
The foot will stay proportional to the height of the prosthetic. The average
child would grow from 100 cm to 130 cm during the ages of 5-10 and the
ratio of height to foot is 16.764 cm :2.54 cm of foot growth
For the experiment, the height of the foot will be measured to ensure that
the prosthetic is strong enough to carry a certain amount of weight
The prosthetic will be tested on the amount of damage it can withstand,
the development of the length and width of the foot itself, and whether it
can hold the weight of a child.
On April 1st, 2017, this experiment was followed and completed in Autodesk
Inventor. FIG. 3 reveals how the carbon fiber prosthetic handled the force applied. The
prosthetic managed to have minimal movement and was strong enough to withstand
such a strong force.
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FIG 3. The Graph above is derived from the data from the Inventor Simulation
Conclusion
The results were impeccable: the prosthetic could withstand around 100 Newtons
of force, which means that the prosthetic can have all the required hardware inside
without any issues. This is a necessary objective since the child must keep the
prosthetic for quite an approximate amount of time. With the future in 3D printing and
robotics, such a prototype would be a huge breakthrough in the prosthetics industry.
Although this product may take some time, this would be a life-long investment for
parents and the betterment of those less fortunate children at a young age. This idea
requires support from workers in the biomedical field to achieve, as it may be costly
timewise.
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REFERENCES (APA)
Burck, James et al. “Developing the World's Most Advanced Prosthetic Arm Using Model-Based Design.” Developing the World's Most Advanced Prosthetic Arm Using Model-Based Design - MATLAB &Amp; Simulink, Johns Hopkins Applied Physics Lab, www.mathworks.com/company/newsletters/articles/developing-the-worlds-most-advanced-prosthetic-arm-using-model-based-design.html. Accessed January 19th 2017
Constantinos Mavroidis, Richard G Ranky, Mark L Sivak, and Benjamin L Patritti. “Patient Specific Ankle-Foot Orthoses Using Rapid Prototyping.” JOURNAL OF NEUROENGINEERING AND REHABILITATION, 2011. Accessed January 29th 2017
Fasel, Jean H. D., Diego Aguiar, Daniel Kiss-Bodolay, Xavier Montet, Afksendiyos Kalangos, Bojan V. Stimec, and Osman Ratib. “Adapting Anatomy Teaching to Surgical Trends: A Combination of Classical Dissection, Medical Imaging, and 3D-Printing Technologies.” Springer, November 9, 2015. Accessed December 18th 2016
“Growth Charts - Clinical Growth Charts.” Accessed February 19, 2017. https://www.cdc.gov/growthcharts/clinical_charts.htm.
Kuiken, Todd A., Guanglin Li, Blair A. Lock, Robert D. Lipschutz, Laura A. Miller, Kathy A. Stubblefield, and Kevin Englehart. “Targeted Muscle Reinnervation for Real-Time Myoelectric Control of Multifunction Artificial Arms.” JAMA : The Journal of the American Medical Association, February 11, 2009. Accessed January 29th 2017 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3036162/.
Töreyin, Hakan, and Pamela Bhatti. “A Field-Programmable Analog Array Development Platform for Vestibular Prosthesis Signal Processing.” IEEE transactions on biomedical circuits and systems 7.3 (2013): 319–325. PMC. Web. Accessed 18 Dec. 2016.
Vee, Annette. "Understanding Computer Programming as Literacy." University of Pittsburgh. Accessed January 29th 2017
Zuniga, Jorge, Dimitrios Katsavelis, Jean Peck, John Stollberg, Marc Petrykowski, Adam Carson, and Cristina Fernandez. “Cyborg Beast: A Low-Cost 3d-Printed Prosthetic Hand for Children with Upper-Limb Differences.” BMC Research Notes 8 (2015): 10. doi:10.1186/s13104-015-0971-9. Accessed January 29th 2017
“3d Printing | Roboticsfinder.” Accessed January 29, 2017. https://roboticsfinder.com/cate-gory/3d-printing/.
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