Design Innovation

Design of a Compliant Endoscopic Suturing Instrument

[+] Author and Article Information
James A. Cronin, Mary I. Frecker

Department of Mechanical and Nuclear Engineering, Pennsylvania State University, 326 Leonhard Building, University Park, PA 16802

Abraham Mathew

Department of Medicine, Penn State Milton S. Hershey Medical Center, Department of Gastroenterology, Hershey, PA 17033

J. Med. Devices 2(2), 025002 (May 30, 2008) (9 pages) doi:10.1115/1.2931551 History: Received December 14, 2007; Revised March 28, 2008; Published May 30, 2008

This paper describes the initial design and optimization of a compliant endoscopic suturing instrument. The emerging field of Natural Orifice Transluminal Endoscopic Surgery (NOTES) requires innovative instruments to meet the size limitations inherent in this type of minimally invasive surgery; using compliant mechanisms is proposed as one method of meeting this requirement. The compliant design was modeled and optimized to maximize the distal opening and provide a puncture force of at least 4.6N, while being small enough to fit within a 3.3mm working channel. The design utilizes contact for stress relief and intertwining parts for added deflection. ANSYS ® was used for finite element analysis including contact and nonlinear deformations. A prototype was fabricated from the optimized geometry and experimentally tested. The best geometry is predicted to have a distal opening of 14.6mm at the tips and supply a puncturing force of 4.83N. The force supplied at the tip was measured and was found to exceed the required 4.6N. The prototype successfully passed two complete sutures and qualitative results are provided. The results of the study will lead to further refinements and improvements in future designs.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Laparoscopic Endo Stitch™ passing a suturing needle between its arms

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Figure 2

Distal tip of flexible endoscope (59)

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Figure 3

Flexible endoscope in the stomach (28)

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Figure 4

Basic compliant instrument tip

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Figure 5

Segment 1 remains within the working channel and Segments 2 and 3 protrude from the end

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Figure 6

Design with cross-sectional cuts as the sheath progresses from left to right

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Figure 7

Cross section of sheath showing the needle-locking arms

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Figure 8

Two dimensional geometry of the design

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Figure 9

Displacement constraints “sliding” along the third segments

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Figure 10

Two dimensional view of instrument response once contact begins

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Figure 11

Graphical optimization

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Figure 12

Von Mises stress versus percent sheath closed for various instrument designs

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Figure 13

Puncture force versus percent sheath closed for various instrument designs

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Figure 14

Half opening sensitivity analysis

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Figure 15

Half segment 2 sensitivity analysis

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Figure 16

Solid model of the compliant suturing instrument (patent pending)

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Figure 17

Prototype of the compliant suturing instrument

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Figure 18

Experimental setup for closing/opening forces

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Figure 19

Starting the first suture on a porcine stomach

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Figure 20

Suturing thread successfully passed through both sides of the incision

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Figure 21

Finishing the second knot

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Figure 22

Tightening and finishing the first suture

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Figure 23

Tip force experimental setup

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Figure 24

Tip force experimental data and FEA prediction




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