INTRODUCTIONINTRODUCTION

“GASTROSEAL” ENDOLUMINAL CLOSURE DEVICEMaking Natural Orifice Transluminal Endoscopic Surgery Possible

Braham K. Dhillon1, Alice R. Hales1, Laura E. Mattaliano1, John P. Sticklen1

Advised by Mike Holzman2, M.D., M.P.H., Gus Attwell, M.D., and Paul King1, Ph.D.Vanderbilt University, 1Department of Biomedical Engineering, 2Department of Surgical Science – General Surgery, 3Department of Medicine – Gastroenterology

FINAL DESIGN – “GASTROSEAL”FINAL DESIGN – “GASTROSEAL” DESIGN PARAMETERSDESIGN PARAMETERS

BACKGROUNDBACKGROUND

RECOMMENDATIONS AND CONCLUSIONRECOMMENDATIONS AND CONCLUSION

DESIGN PROCESSDESIGN PROCESS

PurposeThe purpose of this project is to design a device that will seal a hole in the stomach wall by means of a typical endoscope.

NOTES SurgeryCurrently, most surgeries for disorders in the peritoneal cavity are performed using an incision in the abdomen. However, recently there has been the development of a technique called “natural orifice transluminal endoscopic surgery” (NOTES). With the NOTES procedure, a flexible endoscope, normally used for surgeries within the gastrointestinal tract, is used to electrosurgically make an incision in the stomach wall to gain access to the peritoneal cavity. The problem then is the question of how to seal the incision once the surgery is complete. Currently there is no reliable technique for this task. The purpose of this project is to design a device that will work through the operating port of common endoscopes to stitch, clamp, staple, or otherwise reliably seal the incision and allow it to heal quickly.

Part Component Material Dimensions

Outer Umbrella (1) Frame/spokes Nitinol 1.5cm center to tips

Spines Nitinol 1mm pointing inward

Center tip Nitinol ~4mm in length, 1mm at widest part of tip

Covering Surgisis ~7.0 cm2 surface area

Guiding wire Plastic ~150cm

Inner Umbrella (2) Frame/spokes Nitinol 1.5cm center to tips

Spines Nitinol 1mm pointing outward

Center ring Nitinol 0.8mm in diameter

Covering Surgisis ~7.0 cm2 surface area

Packaging Sleeves (3 and 4) NA Plastic 4 cm in length, 2.9mm OD, ~2.8mm ID

Pushing/Guiding Tube (5) NA Plastic ~2.6mm OD, ~2.5mm ID

BIOMATERIALSBIOMATERIALS

A B C D

Device Details

The GastroSeal Components:

1. Outer umbrella (a) deployed (b) packaged

2. Inner umbrella (a) deployed (b) packaged

3. Outer umbrella packaging sleeve

4. Inner umbrella packaging sleeve

5. Pushing/guiding tube

Device Procedure

A. Outer umbrella (blue) is pushed out of packaging sleeve by the pushing/guiding mechanism (green) and down the operating port. Umbrella unfolds as it emerges from the end of the endoscope and into the stomach.

B. Outer umbrella is positioned on the outside of the stomach wall. Pushing mechanism is removed from operating port. Inner umbrella (red), folded inside packaging sleeve is slipped onto the guiding wire. It is pushed out of packaging sleeve and down the operating port by the pushing mechanism. Umbrella unfolds as it emerges from the end of the endoscope.

C. Inner umbrella is positioned on the inside of the stomach wall. Umbrellas are drawn close together using simultaneous pressure from the pushing mechanism and tension from the guiding wire. Umbrellas clip in place as the center tip of the outer umbrella compresses enough to travel through the center ring of the inner umbrella.

D. Pushing mechanism is removed from operating port. Scissors are used to clip off the guiding wire from the outer umbrella as close as possible to the center tip. Guiding wire and scissors are removed from the operating port.

Initial Design Ideas

Surgical Parameters• Stomach wall thickness ~ 3-5 mm• Incision length ~ 2 cm• Incision will seal completely in 7-14 days

Schematic Theory AnalysisNitinol Coil:

Wire coil would wrap around incision, similar to a notebook binding. Tip of coil would be sharp enough to pierce tissue.

Idea was abandoned because the tip of the coil would be too difficult to control from outside the endoscope. Also, no way to ensure coil stays in place.

EndoCinch® (Bard): Suturing device attaches to end of endoscope. Tissue pinched by suction, and sutures are made by a needle.

Idea was abandoned because suction would not be feasible for use over incision. Also, a design that works through the operating port was preferable.

Umbrella Seal:

Dual umbrella design, one on each side of stomach wall. Umbrellas lock together to seal incision.

This idea was chosen for launch. The design was simple and feasible. The device would be similar to heart-patch devices already on the market that work on the same principle.

1 2 3

4 5

Design Development

Design Concern Modification FigureEndocsope port too small to accommodate spines that pierce thickness of stomach wall.

Instead of using spines that traverse stomach wall to clip together, use short spines to dig into stomach wall to keep device in place.

Need a mechanism for opening umbrellas from folded position.

Use biomaterial Nitinol; it may be folded to fit in endoscope port then spring back into open position upon release.

Need a method to rigidly guide umbrellas in place, then release for implantation.

Outer umbrella attached to flexible guiding wire, then pushed into place by a more rigid tube surrounding the guiding wire.

Need a mechanism for clipping umbrellas together once in place.

Outer umbrella equipped with center spine that will clip into inner umbrella. Clipping to be accomplished by guiding wire and pushing tube.

Need a material for umbrella covering that will effectively seal the incision.

Use biomaterial Surgisis®; it will cover the hole to prevent leakage, then eventually become built into stomach wall for extra stability.

The Stomach• Stomach wall incision made in the body of the stomach in order to avoid damaging the pacesetter cells in the fundus or the muscular antrum.• Mucosa thickness: 1030 ± 130 μm to 1640 ± 80 μm • Wall thickness: 2.8 ± 0.12 mm to 4.23 ± 0.03 mm.

Social Impact and Market Potential• The development of this device would make NOTES procedures possible, eliminating scarring on the abdomen for simple procedures. NOTES might also decrease recovery time.

• About 29% of all surgeries worldwide are performed endoscopically.

• There are about 80,000 abdominal surgeries performed each year in the United States.

Ethical ConcernsDo the benefits of NOTES procedures outweigh the risks? In order to make NOTES procedures ethically feasible, the closure device must be reliable enough to reduce the risk of NOTES to that of laparoscopic procedures.

Procedures that could be performed using NOTES:

• Tubal Ligation• Cholecystretomy• Hysterectomy• Splenectomy• Appendectomy• Gastroenterostomy

NitinolNitinol is a combination of nickel and titanium and is a commonly used biocompatible material. Nitinol has the unique property of thermal shape memory; it becomes very flexible when cooled, and then returns to its original shape when warmed. This property makes Nitinol very useful for devices such as stents and heart patches.

Surgisis®Surgisis® (Cook Group, Inc.) is a biomaterial used for soft tissue grafts. It is a paper-like material that is a matrix of acellular collagen. It is often used for hernia repair. When implanted, Surgisis® acts as scaffolding for new tissue to grow over for remodeling.

Safety Parameters• Device must seal incision completely with no leakage• Stability – device must stay in place where implanted • Materials must be biocompatible• Durability – device must withstand acidic environment

Instrumentation Parameters• Endoscope length: 100-120 cm• Operating port diameter:

d = 2.2-4.2 mm for one port scope

d = 2.8/3.2 mm for two-port scope

For references and citations please see final report, Appendix F, of For references and citations please see final report, Appendix F, of “Gastroseal” Endoluminal Closure Device” by B. Dhillon, A. Hales, “Gastroseal” Endoluminal Closure Device” by B. Dhillon, A. Hales, L. Mattaliano and J. Sticklen.L. Mattaliano and J. Sticklen.

• To-scale model: We were unable to develop a to-scale model because of time constraints and lack of resources. For future work, a to-scale model should be developed by contracting the manufacturing to a company who has the equipment needed to build such a small device. • Testing of our device: Due to time constraints, we were unable to test our device. The next step of the design process would be the development of a working model for testing on animals. Once this has been accomplished, it can then be tested within a clinical trial on humans.• Biobsorbable Material: Our current design is a permanent implant; by using bioabsorbable materials instead of Nitinol, more patients and doctors might be willing to use it. Currently, Guidant is testing a bioabsorpable drug eluting stent that they have developed. If this material proves to be successful in this application, if could be used within the design of the second generation Gastroseal.

We have developed a device that would work with the specified sizes of the endoscope and the incision and that would be biocompatible, durable, and feasible. We feel that with further investigation into bioabsorbable materials and testing, our device could be very marketable and fill the void that currently exists in the development of the NOTES procedure. Ultimately, our design provides the opportunity for NOTES to become a very successful and popular surgery in medicine around the world.

Final Prototype Photos