Last updated: 03/04/21, 12 p.m.

Cochlear implant surgery involves insertion of the electrode into the cochlear, which is very fragile and is exposed to trauma. Currently, the insertion process is entirely dependent on surgeon dexterity. The aim of this project is to design a specialized forceps that can measure 3 DOF force intraoperatively to assist the surgeon in successful atraumatic insertion of the electrode into the cochlea.

• Students: Justin Kim
• Mentor(s): Dr. Deepa Galaiya, Dr. Pete Creighton, Dr. Iulian Iordachita

During a cochlear implant surgery, an electrode array is inserted into the cochlea following the the curvature of the inner membrane. The position of this electrode is crucial to overall performance of the implant, and improper insertion could also lead to trauma. However, currently there are no established methods for guidance, monitoring, or feedback to the surgeon and the insertion process is entirely reliant on surgeon dexterity.

From studies using 6 DOF force sensors to measure the electrode insertion force, the average force measured for atraumatic insertion is around 20 mN, while for traumatic insertion is around 60 mN (Seta, 2017). These forces are tiny and are outside the resolution of a surgeon. Lastly, an assessment conducted in 2017 reported that the trauma rate of the surgery was 17.6% (Hoskison, 2017). The goal of the project is to develop force-sensing forceps that can report force measurement intraoperatively, thereby facilitating successful and safe insertion procedure.

A modified version of the commercial forceps used for electrode insertion was designed, prototyped, and tested prior to this semester. The design consisted of a mechanically weakened region near the front end of the forceps. These regions deflect accordingly to the electrode insertion force, and a mounted strain gauge measured strain, which was converted to force. This design was met with two main challenges: 1) pinching the forceps also caused deflection in the weakened region, which added onto the insertion force, which is what we are actually interested in. The design failed the effectively isolate this noise from the force we are interested in. 2) Because we only mounted one strain gauge, the forceps could only measure 1 DOF force effectively. Because the orientation of the electrode relative to the forceps is inconsistent, 3 DOF force measurement is required.

Prior work strongly suggested a new design for the forceps is required. The new design will be based on a 3 DOF force-sensing forceps used for vitreoretinal surgery, developed by Dr. Iulian Iordachita. The design has two advantages: 1) a consistent actuation method allowing for better pinching force isolation method and 2) 3 DOF force sensing availability.

The ultimate goal of this semester is to design the new forceps and prepare a functional prototype.

Although there have been multiple attempts at measuring safe electrode insertion force, none were performed with a hand-held tool in-vivo. The design of this project can be used intraoperatively and can deliver more actual force measurements within actual clinical settings.

A successful design of force sensing forceps also has a potential for collaboration with Galen Robotics to produce a robot-assisted feedback mechanism. A possible auditory feedback to the surgeon can thereby facilitate successful atraumatic insertion of the forceps and overall improved cochlear implant performance.

• Minimum: (March 23rd)
  1. Completed final design
  2. Final CAD model
  3. Report of Finite Element Analysis results

• Expected: (May 4th)
  1. Fabricated prototype with sensors attached
  2. Preparation for calibration and test rig
  3. Plan for further tests

• Maximum: (TBA)
  1. Report of calibration data analysis
  2. More tests under different conditions
  3. Plan for design iteration and future work

There are multiple constraints that need to be taken under design consideration. First, the design must be ergonomic. This includes not only the most obvious as size and shape, but also should not obstruct the view of the surgical site and also should avoid new features or techniques that add onto the current surgery process. Surgeon should be able to use the forceps without too much training. Second, the design must have a feature to isolate pinching force from insertion force. Third, the design must have 3 DOF force sensing availability.

The basic geometry of the forceps should be determined by calculating expected deflection via beam deflection equation: δ_max=(Pl^3)/3EI ,where δ=deflection, P=pressure, l=length, E=Young^' s Modulus, I=second moment of inertia

Calculation should also be assisted with CAD and simulations of finite element analysis. Below is a current CAD model.

The schematic of the pinching mechanism is shown below.

Here, the jaws of the forceps are actuated by pinching the actuation legs. The legs are grounded in the front, so pinching results in pulling of the middle segment and closing of the jaw. Sensors will be attached in the cruciform region, measuring 3 DOF forces.

The cruciform design references a MEMS 6 DOF force measurement design. Here, the 4 connectors to the middle segment is subjected to both lateral and axial translation and also torque. For our purposes, the inner segment will not be directly connected to the lateral segment and will be subjected to pulling force from the actuation mechanism. The lateral segments will experience both axial and lateral forces, which will translate into the deformation of the connected cruciform region similarly to the above MEMS 6 DOF force measurement design. Finally, we are only interested in 3 DOF for our purposes and will not apply sensors to measure torque.

Extensive FEA was performed to simulate the force-strain relationship at the cruciform design. Optimal strain to be observed is on the order of tens of microstrain. Optimization study was performed by varying cruciform length, width, and thickness. Example of an optimization study is below.

Below is the table of observed strain by different directions and an example of FEA result

The design will then be prototyped. Depending on the geometry of the design, some parts will need to be produced via Electric Discharge Machining (EDM), CNC Milling, and rapid prototyping as needed. The plastic case for the forceps will most likely be 3D printed or even injection molded. Below is the bill of materials and manufacturing methods

Finally, calibration study and testing will be performed with Dr. Galaiya. For calibration study, a known weight will be lifted using the forceps and he strain will be recorded. The recorded data will be analyzed using Dewesoft X3 and MATLAB. Then, electrode insertion study will be performed using a plastic and acrylic cochlea model. The model will also be set on top of a scale, and force measurement from the scale will be used to compare the strain measurement collected with the forceps.

Some parts of the prototype is planned to be built in the campus. Some of the manufacturing is to be outsourced, and there was be a major time dependency based on their lead time.

If the prototype is functional, testing will need to accommodate to Dr. Galaiya’s availability and also will depend on school policy with maximum number of people in a single room (Mock OR). If maximum number of people is reached, some people may have to participate via Zoom.

Below table is the calculated estimated cost. The source for the budget is still under discussion and needs to be resolved. Dr. Deepa Galaiya is currently looking to allocate some budget, and this will be discussed during LCSR general meeting on February 24th.

1. Milestone name: Produce optimization study of cruciform strain based on forceps geomettry
   • Planned Date: February 18th
   • Expected Date: March 3rd
   • Status: 100%

1. Milestone name: Determine actuation mechanism
   • Planned Date: March 3rd
   • Expected Date: March 11th
   • Status: 100%

1. Milestone name: Produce final CAD design & FEA
   • Planned Date: March 11th
   • Expected Date: March 23rd
   • Status: 100%

1. Milestone name: Produce prototype (without sensors)
   • Planned Date: March 11th
   • Expected Date: April 8th
   • Status: 50% (jaw component finished prototyping)

1. Milestone name: Attach sensors
   • Planned Date: April 8th
   • Expected Date: April 20th
   • Status: 0% (will continue through summer & next year)

• Project Plan
  • Project plan presentation
  • Project plan proposal
• Project Background Reading
  • See Bibliography below for links.
• Project Checkpoint
  • Project checkpoint presentation
• Paper Seminar Presentations
  • here provide links to all seminar presentations
  • Paper Presentation
  • Paper Report
  • Design of 3-DOF Force Sensing Micro-Forceps for Robot Assisted Vitreoretinal Surgery
• Project Final Presentation
  • PDF of Poster
• Project Final Report
  • Final Report

• Fontanelli, G. A., Buonocore, L. R., Ficuciello, F., Villani, L., & Siciliano, B. (2017). A novel force sensing integrated into the trocar for minimally invasive robotic surgery. 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). doi: 10.1109/iros.2017.8202148

• Gonenc, B., Feldman, E., Gehlbach, P., Handa, J., Taylor, R. H., & Iordachita, I. (2014). Towards robot-assisted vitreoretinal surgery: Force-sensing micro-forceps integrated with a handheld micromanipulator. 2014 IEEE International Conference on Robotics and Automation (ICRA). doi: 10.1109/icra.2014.6907035

• Kobler, J.-P., Beckmann, D., Rau, T. S., Majdani, O., & Ortmaier, T. (2013). An automated insertion tool for cochlear implants with integrated force sensing capability. International Journal of Computer Assisted Radiology and Surgery, 9(3), 481–494. doi: 10.1007/s11548-013-0936-1

• Kratchman, L. B., Schuster, D., Dietrich, M. S., & Labadie, R. F. (2016). Force Perception Thresholds in Cochlear Implantation Surgery. Audiology and Neurotology, 21(4), 244–249. doi: 10.1159/000445736 • Nguyen, Y., Miroir, M., Kazmitcheff, G., Sutter, J., Bensidhoum, M., Ferrary, E., … Grayeli, A. B. (2012). Cochlear Implant Insertion Forces in Microdissected Human Cochlea to Evaluate a Prototype Array. Audiology and Neurotology, 17(5), 290–298. doi: 10.1159/000338406

• Schurzig, D., Labadie, R. F., Hussong, A., Rau, T. S., & Webster, I. R. J. (2012). Design of a Tool Integrating Force Sensing With Automated Insertion in Cochlear Implantation. IEEE/ASME Transactions on Mechatronics, 17(2), 381–389. doi: 10.1109/tmech.2011.2106795

• Seta, D. D., Torres, R., Russo, F. Y., Ferrary, E., Kazmitcheff, G., Heymann, D., … Nguyen, Y. (2017). Damage to inner ear structure during cochlear implantation: Correlation between insertion force and radio-histological findings in temporal bone specimens. Hearing Research, 344, 90–97. doi: 10.1016/j.heares.2016.11.002

• Sunshine, S., Balicki, M., He, X., Olds, K., Kang, J. U., Gehlbach, P., … Handa, J. T. (2013). A Force-Sensing Microsurgical Instrument That Detects Forces Below Human Tactile Sensation. Retina, 33(1), 200–206. doi: 10.1097/iae.0b013e3182625d2b

• Wade, S. A., Fallon, J. B., Wise, A. K., Shepherd, R. K., James, N. L., & Stoddart, P. R. (2014). Measurement of Forces at the Tip of a Cochlear Implant During Insertion. IEEE Transactions on Biomedical Engineering, 61(4), 1177–1186. doi: 10.1109/tbme.2013.2296566

• Zareinia, K., Maddahi, Y., Gan, L. S., Ghasemloonia, A., Lama, S., Sugiyama, T., … Sutherland, G. R. (2016). A Force-Sensing Bipolar Forceps to Quantify Tool–Tissue Interaction Forces in Microsurgery. IEEE/ASME Transactions on Mechatronics, 21(5), 2365–2377. doi: 10.1109/tmech.2016.2563384

• De Seta D, Torres R, Russo FY, Ferrary E, Kazmitcheff G, Heymann D, Amiaud J, Sterkers O, Bernardeschi D, Nguyen Y. Damage to inner ear structure during cochlear implantation: Correlation between insertion force and radio-histological findings in temporal bone specimens. Hear Res. 2017 Feb;344:90-97. doi: 10.1016/j.heares.2016.11.002. Epub 2016 Nov 5. PMID: 27825860.

• Gao, Anzhu, et al. “3-DOF Force-Sensing Micro-Forceps for Robot-Assisted Membrane Peeling: Intrinsic Actuation Force Modeling.” 2016 6th IEEE International Conference on Biomedical Robotics and Biomechatronics (BioRob), 2016, doi:10.1109/biorob.2016.7523674.

• Handa, James, et al. “Design of 3-DOF Force Sensing Micro-Forceps for Robot Assisted Vitreoretinal Surgery.” IEEE Engineering in Medicine and Biology Society, 2013, doi:10.1109/EMBC.2013.6610841.

• Hoskison E, Mitchell S, Coulson C. Systematic review: Radiological and histological evidence of cochlear implant insertion trauma in adult patients. Cochlear Implants Int. 2017 Jul;18(4):192-197. doi: 10.1080/14670100.2017.1330735. Epub 2017 May 23. PMID: 28534710.

• “Implant Programs - Mankato.” Mayo Clinic Health System, www.mayoclinichealthsystem.org/locations/mankato/services-and-treatments/audiology/implant-programs.

Here give list of other project files (e.g., source code) associated with the project. If these are online give a link to an appropriate external repository or to uploaded media files under this name space (2021-02).