1. RESEARCH POSTER PRESENTATION DESIGN © 2012
www.PosterPresentations.com
INTRODUCTION
• Create a device within dimension
constraints that provides
instantaneous feedback (buckling) to
a surgeon during insertion of
electrode array.
• Prevent any possible damage to a
membrane when used in operation.
Cochlear membrane yield forces
range 100mN to 250mN.
• Current prong devices have rods with
thickness 0.6-0.8mm and length 6-
8mm to work with the small
environment of the middle ear.
Dr. Wendell Todd, an experienced
cochlear implantation surgeon at Emory,
helped us create these objectives.
OBJECTIVES
By manipulating Euler’s formula for
buckling with expected threshold forces of
the cochlear membranes, we can find
values of Young’s Modulus for the rod
Euler’s formula:
𝐹𝑚𝑎𝑥 =
𝜋2×𝐸 ×𝐼
(𝑘 ×𝑙)2
𝐼 =
𝜋 × 𝑑4
64
l = length of rod
E= Young’s Modulus of material
Fmax = threshold forces to cause buckle
d = diameter of rod
I = area moment of inertia for cylindrical rod
k = effective length constant (k=0.5 for rod of
two fixed ends)
With given dimension constraints, we seek
material with Young’s Moduli of
approximately 6MPa
Currently there is no standard for insertion
forces and speeds during cochlear implantation
surgery and such forces are not reliably
visualized during implantation which can damage
fine structures, such as the cochlear
membranes.
The proposed 3D printed device will provide
direct tactile feedback when too much force is
applied in electrode array insertion—the rod of
the device will buckle. Designed for the range of
yield forces of the membrane of the cochlea, the
prong material will have a calculated Young’s
Modulus in a to buckle before damaging cochlear
membranes. These properties be achieved by
adjusting the dimensions and material of the
rod.
By creating a specific threshold gauge, the
insertion of the cochlear implant electrode array
can become a more scientific surgery.
DESIGN
PRINT RESULTS
DISCUSSION
• Printers today can achieve the
resolution of intricate surgical devices
needed for cochlear implantation today,
and the prints we made of the models
show that.
• 3D printer materials can be mixed
together to create an ink with desired
Young’s Modulus as calculated to give us
the force thresholds desired.
• Prints can be practically tested against
force sensors to ensure proper force
thresholds
• Several devices can be printed with 50
mN of difference in force thresholds
• Surgeons can “practice” their electrode
array insertion with progression of force
thresholds to create a more trained
surgery with plexiglass and cadaveric
cochlea
• Eventually, these devices can be used in
surgery as an extra prevention of
membrane damage.
REFERENCES
Francis X. Creighton Jr., N. W. Todd. (2011). Force Threshold Gauge
in Ear Surgery.
Rajan, G. P., Kontorinis, G., & Kuthubutheen, J. (2013). Audiol
Neurootol, 18(1), 17-22.
Scott A. Wade, et. al. (2014). Measurement of Forces at the Tip of a
Cochlear Implant during Insertion, IEEE Transactions on Biomedical
Engineering, 61(4), 1177-86
How [the cochlear implant] works. (n.d.). Retrieved April 18, 2014,
from www.cochlear.com
ACKNOWLEDGEMENTS
Dr. Wendell Todd, Dr. Pamela Bhatti,
Kevin Pham, James Steinberg, Diana Jarvis,
Stratasys, Invention Studio,
School of Electrical and Computer
Engineering,
School of Biomedical Engineering
Sponsored in part by the National Science
Foundation awards 0927103, 105580
Biomedical Engineering
BioSystems Interface Laboratory, School of Electrical and Computer Engineering
Samir Jain
Creating a Cochlear Implantation Training Device for Surgeons Using 3-D Printing
Original
Surgical Claw
Initial model
Print to test 3D printing resolution and capabilities
Prong Design
Prong is stiff, and has
to be at similar
dimensions to original
surgical claw.
These models show
iteration stages.
Stratasys Objet print of initial model.
Rod tip was not structurally stable to stay
straight
Invention Studio Objet print of
tilted prong model.
Cochlea
Cochlear Implants
overcome sensorineural
hearing loss through direct
electrical stimulation to
auditory nerve fibers via
the cochlea.Electrode
Array