Bioloch studies performed in phase 1 of the project Section for Minimally Invasive Surgery,...

Bioloch studies performed in phase 1 of the project

Section for MinimallyInvasive Surgery,University of Tübingen

Marc O. Schurr, Daniel Kalanovic

33 Colonic wall hazards of endoscopic BIOLOCH devices Colonic wall hazards of endoscopic BIOLOCH devices

22 Mesenteric hazards of endoscopic BIOLOCH devicesMesenteric hazards of endoscopic BIOLOCH devices

11 Applicational force pattern measurement: overview Applicational force pattern measurement: overview

44 Force pattern for walking devices Force pattern for walking devices

55 Force pattern for creeping devicesForce pattern for creeping devices






Parameters forwalking insidethe colon

• Forces• Wall elasiticity

Mesenteric hazards:

• Tears

• Ruptures

Paremeters forcreeping insidethe colon

• With tail• Without tail

Colonic hazards

• Perforation

Mesenteric resistance

Colonic wall resistance

Force / step ratio

Device advancement forcesForce pattern overviewForce pattern overview

Description of force parameters of the colonic tract in interaction with endoscopic devices and techniques

Different experimental series have been performed to describe the interaction of ttols and bowel.






Mesenteric hazards.

Forces resulting in mesenteric tears or perforation of the colon were studied.

Pulling on the mesentery

Force measurement gauge

Mesenteric damage Bowel perforation

Pushing against the bowel wall

0

2

4

6

8

10

12

14

16

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Minor tears

Ruptures

Determination of threshold forces causing damage to bowel and mesentery

Mesenteric lesions can be caused by excessive radial forces exerted on the bowel holding apparatus.

Formation of mesenteric tears as a result of radial forces






0

5

10

15

20

25

30

35

40

45

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

2.5 mm device

10 mm device

20 mm device

Perforation of colonic wall as a result of perpendicular device collision

Colonic wall hazards.

Depending on their size, components of an endoscopic device can perforate the colonic wallat relatively low forces. This implies, that precaution has to be taken in all self-locomoting mechanisms.






Force pattern for walking mechanisms.

In the measurements the force / step relationship was determined in context with bowel tissueelasticity .

Bowel wall displacement

At what force does a step of an imaginary walking instrument get ineffective ?


In the first series of experiments, only the mucosal layer was grasped („grasping leg“).

0

0,1

0,2

0,3

0,4

0,5

0,6

1 2 3 4 5 6 7 8 9 10

1 cm

1.5 cm

2 cm or below

Force / Step ratio, „grasping leg“, mucosal attachment


With mucosal attachment, grasping legs seem not to be able to transport sufficient loads (device weight and friction).


In the second series of experiments, also the muscular layer was grasped („grasping leg“).

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

1 2 3 4 5 6 7 8 9 10

1 cm

1.5 cm

2 cm

2.5 cm

Force / Step ratio, „grasping leg“, muscular attachment


With muscular attachment, grasping legs can transport multiples of the loads compared to mucosal attachment.


In the third series of experiments, mucosal suction („suction leg“) was used.

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

1 2 3 4 5 6 7 8 9 10

1 cm

1.5 cm

Force / Step ratio, „suction leg“, mucosal attachment


Suction legs did not yield more holding capabilites than mucosal grasping.

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1 2 3 4

Mucosal grasping

Muscular grasping

Suction grasping

1. 1 cm2. 1.5 cm3. 2 cm4. 2.5 cm

average values of 10 experiments

Force / Step ratio, comparison


In comparison the value of mucosal involvement into the locomotion process get clear.






Force pattern for creeping mechanisms.

A dummy of a creeping mechanism (20 X 80 mm, 100 g) was used to study the forces involved for passage of the different segments of the colon.

Set-up with animal tissue

Device dummy head pulled through the bowel

Two version: with and without „tail“

0

1

2

3

4

5

6

7

8

1 2 3 4 5 6

Device without tail

Device with tail

Comparison 20 x 80 mm device with and without tail

Forces related to the passage of a 20x80 mm device through the colon

Measurement results help to understand the bowel-device interaction better.

1. Anus2. Rectum3. Sigmoid4. Descending colon5. Transverse colon6. Ascending colon

average values of 20 experiments



0

1

2

3

4

5

6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Anus (model)

Rectum

Sigmoid

Descending colon

Transverse colon

Ascending colon

20 x 80 mm device pulled through the large bowel

0

1

2

3

4

5

6

7

8

9

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Anus (phantom)

Rectum

Sigmoid

Descending colon

Tranverse colon

Ascending colon

20 x 80 mm device with tail pulled through the large bowel



Conclusions

Initial conclusions to be drawn from the applicational force measurements.

1. Hazards for the colon wall and the mesentery start at 3 - 6 N, respectively, depending onthe size of the device.

2. To overcome the basic problem of inch-worm creeping devices, speed, walking may bean option. The mechanical restistance of the colonic wall allows to apply forces of about1 N to „at ground displacement of 2 cm“, provided, that the muscular layer is involved.

3. Mechanisms, that only involve the mucosal layer may be less effective.

4. The pulling force required to move a creeping dummy object through the colon can come up to 8 N. A „tail“ may easily double the force required to move the object.

Clearance of the colonic wall to minimize friction.

Walking legs for locomotion.

Date post:	03-Jan-2016
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Bioloch studies performed in phase 1 of the project Section for Minimally Invasive Surgery,...

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