Bioloch studies performed in phase 1 of the project
Marc O. Schurr, Daniel Kalanovic
Section for Minimally
Invasive Surgery,
University of Tübingen
1
Applicational force pattern measurement: overview
2
Mesenteric hazards of endoscopic BIOLOCH devices
3
Colonic wall hazards of endoscopic BIOLOCH devices
4
Force pattern for walking devices
5
Force pattern for creeping devices
1
Applicational force pattern measurement: overview
2
Mesenteric hazards of endoscopic BIOLOCH devices
3
Colonic wall hazards of endoscopic BIOLOCH devices
4
Force pattern for walking devices
5
Force pattern for creeping devices
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:
• Tears
• Ruptures
Parameters for
walking inside
the colon
• Forces
• Wall elasiticity
Mesenteric resistance
Force / step ratio
Force pattern overview
Colonic wall resistance
Colonic hazards
• Perforation
Device advancement forces
Paremeters for
creeping inside
the colon
• With tail
• Without tail
1
Applicational force pattern measurement: overview
2
Mesenteric hazards of endoscopic BIOLOCH devices
3
Colonic wall hazards of endoscopic BIOLOCH devices
4
Force pattern for walking devices
5
Force pattern for creeping devices
Mesenteric hazards.
Forces resulting in mesenteric tears or perforation of the colon were studied.
Mesenteric damage
Bowel perforation
Force
measurement
gauge
Pushing
against the
bowel wall
Pulling on the
mesentery
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
16
14
12
10
Minor tears
8
Ruptures
6
4
2
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
1
Applicational force pattern measurement: overview
2
Mesenteric hazards of endoscopic BIOLOCH devices
3
Colonic wall hazards of endoscopic BIOLOCH devices
4
Force pattern for walking devices
5
Force pattern for creeping devices
Colonic wall hazards.
Depending on their size, components of an endoscopic device can perforate the colonic wall
at relatively low forces. This implies, that precaution has to be taken in all self-locomoting
mechanisms.
Perforation of colonic wall as a result of perpendicular device collision
45
40
35
30
2.5 mm device
25
10 mm device
20
20 mm device
15
10
5
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
1
Applicational force pattern measurement: overview
2
Mesenteric hazards of endoscopic BIOLOCH devices
3
Colonic wall hazards of endoscopic BIOLOCH devices
4
Force pattern for walking devices
5
Force pattern for creeping devices
Force pattern for walking mechanisms.
In the measurements the force / step relationship was determined in context with bowel tissue
elasticity .
At what force does a step of an imaginary walking instrument get ineffective ?
Bowel wall
displacement
Force pattern for walking mechanisms.
In the first series of experiments, only the mucosal layer was grasped („grasping leg“).
Force pattern for walking mechanisms.
With mucosal attachment, grasping legs seem not to be able to transport sufficient loads
(device weight and friction).
Force / Step ratio, „grasping leg“, mucosal attachment
0,6
0,5
0,4
1 cm
0,3
1.5 cm
2 cm or below
0,2
0,1
0
1
2
3
4
5
6
7
8
9
10
Force pattern for walking mechanisms.
In the second series of experiments, also the muscular layer was grasped („grasping leg“).
Force pattern for walking mechanisms.
With muscular attachment, grasping legs can transport multiples of the loads compared to
mucosal attachment.
Force / Step ratio, „grasping leg“, muscular attachment
1,8
1,6
1,4
1,2
1 cm
1
1.5 cm
2 cm
0,8
2.5 cm
0,6
0,4
0,2
0
1
2
3
4
5
6
7
8
9
10
Force pattern for walking mechanisms.
In the third series of experiments, mucosal suction („suction leg“) was used.
Force pattern for walking mechanisms.
Suction legs did not yield more holding capabilites than mucosal grasping.
Force / Step ratio, „suction leg“, mucosal attachment
0,45
0,4
0,35
0,3
0,25
1 cm
1.5 cm
0,2
0,15
0,1
0,05
0
1
2
3
4
5
6
7
8
9
10
Force pattern for walking mechanisms.
In comparison the value of mucosal involvement into the locomotion process get clear.
Force / Step ratio, comparison
1,4
1,2
1
0,8
Mucosal grasping
Muscular grasping
0,6
Suction grasping
0,4
0,2
1. 1 cm
2. 1.5 cm
3. 2 cm
4. 2.5 cm
0
1
2
3
4
average values of 10 experiments
1
Applicational force pattern measurement: overview
2
Mesenteric hazards of endoscopic BIOLOCH devices
3
Colonic wall hazards of endoscopic BIOLOCH devices
4
Force pattern for walking devices
5
Force pattern for creeping devices
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
Two version: with and
without „tail“
Device dummy head
pulled through the bowel
Forces related to the passage of a 20x80 mm device through the colon
Measurement results help to understand the bowel-device interaction better.
Comparison 20 x 80 mm device with and without tail
8
7
6
5
Device without tail
4
Device with tail
3
2
1. Anus
2. Rectum
3. Sigmoid
4. Descending colon
5. Transverse colon
6. Ascending colon
1
0
1
2
3
4
5
6
average values of 20 experiments
Forces related to the passage of a 20x80 mm device through the colon
Measurement results help to understand the bowel-device interaction better.
20 x 80 mm device pulled through the large bowel
6
5
Anus (model)
4
Rectum
Sigmoid
3
Descending colon
Transverse colon
2
Ascending colon
1
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
Forces related to the passage of a 20x80 mm device through the colon
Measurement results help to understand the bowel-device interaction better.
20 x 80 mm device with tail pulled through the large bowel
9
8
7
Anus (phantom)
6
Rectum
5
Sigmoid
4
Descending colon
Tranverse colon
3
Ascending colon
2
1
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20
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 on
the size of the device.
2. To overcome the basic problem of inch-worm creeping devices, speed, walking may be
an option. The mechanical restistance of the colonic wall allows to apply forces of about
1 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.