Ergonomic Laparoscopic StaplerClient: Dr. Amy Liepert

Advisor: Professor Mitchell TylerBME 402 | Department of Biomedical Engineering

University of Wisconsin – Madison

Powered surgical staplers are used to simultaneously cut and seal tissue during laparoscopic surgeries. Minimally invasive surgeries like laparoscopic surgeries have increased in popularity because of the reduced amount of blood loss, scarring, and recovery time with respect to traditional surgeries. However, current laparoscopic stapler devices are bulky and fail to ergonomically accommodate 66% of the surgeon population. The two largest opportunities for improvement are the wrist angle of the surgeon and clamping lever reach distance. The force needed to grip and control the stapler also puts excess stress on the tendons in the wrist and hand of the surgeon. This project aims to increase population of both female and male surgeons who can comfortably grip and control the device, as well as reduce tendon stress when clamping down on the stapler with the fingers.

Testing and Results

Abstract

● iDrive Ultra Powered Stapling System by Medtronic○ Powered by a battery pack and is controlled via three buttons○ Configuration and the weight of the device not ideal○ Lacks the clamping control - safety concern

● No laparoscopic surgical staplers on the market that utilize an inline handle design

Leader: Jamie SpellmanBSAC: Emkay SrinidhiBPAG: Connor SheedyBWIG: Yaniv SadkaCommunicator: Kelsey Linsmeier

[1] Restyanszki, Besser, Fugate, Anderson. Final Paper, BME Design Spring 2017.[2] DOME Medical Technologies Inc. (2017). Laparoscopic Surgery. [online] Available at: http://domemedical.com/laparoscopic-surgery/[3] Liepert, Amy: personal correspondence, 1/30/2017 [4] "Hand assisted laparoscopic surgery (HALS) stapling to create gastric tube – Art as Applied to Medicine", Medicalart.johnshopkins.edu, 2017. [Online]. Available: http://medicalart.johnshopkins.edu/portfolio-item/hand-assisted-laparoscopic-surgery-hals-stapling-to-create-gastric-tube/.[5] "Ethicon echelon Endopath Stapler, 60mm," in Medex Supply, 2017. [Online]. Available: https://www.medexsupply.com/surgical-supplies-surgical-instruments-skin-staplers-removers-ethicon-echelon-endopath-stapler-60mm-x_pid-63191.html?pid=63191&gclid=CPaYuMrZmNICFVq1wAodjKEOHw. Accessed: Feb. 18, 2017. [6] Jiangsu Baichang Pharmaceutical Co. LTD, ECHELON FLEX Powered ENDOPATH Stapler. 2017.[7] "IDrive™ ultra powered stapling system," in Medtronic Covidien Products, 2017. [Online]. Available: http://www.medtronic.com/covidien/products/surgical-stapling/idrive-ultra-powered-stapling-system. Accessed: Feb. 16, 2017.[8] "Amy E. Liepert, MD," in UW Health Find a Doctor, UW Health, 2016. [Online]. Available: http://www.uwhealth.org/findadoctor/profile/amy-e-liepert-md/9451. Accessed: Feb. 15, 2017.[9] ETHICON, Surgical Stapling Grip. 2017.[10] Aastha Health care, Laparoscopic Cholecystectomy. 2017.[11] PhysioSupplies. (2017). Hand Dynamometer Hydraulic Jamar. [online] Available at: https://www.physiosupplies.eu/hand-dynamometer-hydraulic-jamar [Accessed 10 Oct. 2017].[12] Snook, S. and Vaillancourt, D. (2007). Psychophysical studies of repetitive wrist flexion and extension. Ergonomics, 38(7).[13] “3DSSPP: Background Information,” Center for Ergonomics, 2017. [Online]. Available: https://c4e.engin.umich.edu/tools-services/3dsspp-software/3dsspp-background-information/. [Accessed: 23-Apr-2017].

● Fabricate the gears out of steel and ensure clamping mechanism works● Engineer the new trigger fire mechanism● Engineer the new articulation mechanism● Conduct a focus group with more surgeons to gather quantitative and qualitative

feedback on the new ergonomics○ Use feedback to continue iterating new models

● Meet with WARF to discuss intellectual property potential● Meet with industry representatives to discuss licensing potential

Motivation● The pistol grip configuration of the device forces the posture of the surgeon to be

inopportune while in surgery● Dimensions of the stapler grip are too large to comfortably fit 66% of the surgeon population● Women, who on average have hands 1” shorter than men, have become more than 33% of

the surgical population from 1994 to 2004.● Force needed to grip and control the stapler puts excess stress on the tendons in the wrist

and hand of the surgeon - especially when held below elbow height ○ This stress can cause musculoskeletal disorders

Problem Statement

Competing Designs

Background

Design Goals

Final Prototype

Ergonomic Testing

Future Work

Acknowledgements

References

Mechanical Testing

Shown on the right is a surgeon demonstrating how they would hold the stapler during an appendectomy procedure. The tension in their wrist is apparent and they are forced to bear the weight of the device mostly on the muscles of the forearm. They are unable to grip the device as it was designed, and consequently are forced to choke to the very top or rotate their wrist in order to operate.

Figure 1 (above): Schematic of surgeon holding the current model of the surgical stapler. Figure 2 (below): The BME 301 design

Previous DesignA BME 301 design team conceptualized and 3D printed an ergonomic inline handle design, pictured right. Although the ergonomic aspects are optimized such that 89% of the surgeon population would be accommodated, the size of the handle was not feasible mechanically. This semester the current design team worked to insert its linearized drive system into a linear ergonomic casing.

Figure 9: Hand posture required to operate the Echelon Flex (left) and the final prototype design (right)

Figure 10: 3DSSPP model of posture for Echelon Flex (left) and the final prototype design (right)

● Redesign the surgical stapler into a linear design for improved ergonomics○ Linearize all components without sacrificing usability and put all linearized mechanical

elements into a casing the maximizes the percent of surgeons accomodated

Horizontal Drive Bar & Gear Reconfiguration● Enables the gear system to interface

with the drive bar in a horizontal orientation

● First bevel gear caps the existing vertical gear atop the motor

● Second bevel gear is attached to the gear that drives the drive bar

3DSSPP Static Strength

Anthropometric Accommodation

Linear Drive Bar & Gear System currently at 90deg, need to redesign at 180deg

Manual Closing Trigger currently at 90deg, need to redesign at 180deg

Battery Pack reconfigure to reduce width

Figure 3 (right): The internal mechanical components of the Ethicon stapler, labeled and described.

Ethicon Echelon Flex Model Proposed Model

Dynamic System Model: Dynamic System Model:Block Diagram Model: Block Diagram Model:

ResultsThe angular acceleration of the gear at the interface of the drive bar for each system is equivalent.

ConclusionThe overall mechanical function of the system will not be sacrificed.

Thank you to Professor Mitch Tyler for advising us throughout the project and to Dr. Amy Liepert for proposing the project and answering questions throughout the semester.We would also like to acknowledge the previous design groups who began this project: Fall 2016 BME 200/300 (Madelyn Goedland, Justin DeShaw, Gregory Wolf, Alexander Babinski, Jacob Andreae), Spring 2017 BME 301 (Andrew Fugate, Albert Anderson, Ellen Restyanszki (and F17), Therese Besser (F17)).

Figure 13: Anthropometric trigger reach distance

It was assumed that comfortable operation of the device requires that the first knuckle of the fifth digit can reach the trigger. This prototype accommodates 86% of the surgeon population, up from the Echelon Flex’s 34% accommodated. The increase in accommodation is a result of decreasing the distance from the device to the trigger. Accommodation percentages were calculated using the US Army Anthropometric Database.

Figure 5: Exposed bevel gear system

Equation of Motion:

Figure 12: Summary table of anthropometric and accommodation calculations

The inline grip design increased the percent of females accommodated from 11% to 71%, and the percent of males accommodated from 50% to 95%. Figure 11: Summary of results from 3DSSPP models

Figure 7: Dynamic system and block diagram model of Ethicon Echelon Flex Model

Clamping Lever Mechanism● Utilizes a Whitworth quick-return

mechanism to close the jaws of the stapler

● The grip handle serves as the crank wheel

● Generates the translational force required to close the jaws of the device.

Figure 8: Dynamic system and block diagram model of Proposed Model

Equation of Motion:

Final Encased Design● 3D printed using the FormLabs 2 resin printer● Form-fitted to the mechanical system to minimize wasted space to maximize the

percent of surgeons accomodated● Reduces clamping mechanism reach distance and strain on the wrist

Figure 6: Final ergonomic prototype

Figure 6: Mechanism converts rotational motion into translational motion