Contributions to the design of circular surgical staplers for minimally invasive therapy

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Contributions to the design
of circular surgical staplers
for minimally invasive
therapy
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• A Doctoral Thesis. Submitted in partial fulfillment of the requirements
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Contributions
to the Design Circular Surgical Staplers for
of
Minimally Invasive Therapy
John McGuire
A Doctoral Thesis
for
Submitted in fulfillment the the
of requirements award of
partial
Doctor Philosophy Loughborough University
of of
June 1999
by J. McGuire 1999
kQD/
To
myjamily,
including James McGuire,
the
memory of myfather
Abstract
Circular
to join two hollow together from
staplers are used organs
within, a
known intraluminal A typical
procedure
as anastomosis. application
would
follow
from the food tract, two
an excision to be joined.
where ends need
A detailed from
technology
study of what surgeons want circular stapling
was
Generally, it found
that
undertaken. was surgeons want circular staplers
to
which can allow greater access awkward surgical sites, and which can
facilitate the development techniques
of surgical which are more minimally
invasive than those by instruments. The
permitted current specific
from this to design
conclusions study were refined produce a product
(PIDS) for ideal for invasive therapy
specification an circular stapler minimally
(MIT). Circular tissue together before joining it ("firing"
staplers approximate
the An MIT have to tissue fire the
stapler). version would approximate and
driver flexible Knowledge the to
stapling-cutting via a extension. of extent
tissue be inadequate. The firing force,
which might safely compressed was
limits the
which choice of remote actuation means, was also unknown.
A test designed to tests in
rig was allow which, conjunction with a materials
firing functions
the
testing
machine, could emulate approximation and and
intracellular
the loads both. A the
record of measure of expulsion of
from the intestines
potassium solution porcine used was also measured with
The load
the tissue tests. and potassium output
combined
compression
indicate that
porcine gut wall generally may experience
compression results
from 0.19
form mm/ mm compressive
around
some of mechanical yielding
the firing load identified
The and
of were
components
strain. various
1500 N
firing load
The biggest
recorded was approximately
recorded.
the data has led to the
of
The a clearer understanding
analysis of
resulting
be designed (both
generally
within which circular staplers should
constraints
for MIT), theoretical how the design
as well as a account of constraints
and
by the function be lessened. An design
imposed stapling may example of a
this knowledge is
utilises given.
which
Acknowledgments
I
like to thank Mr Joseph Leverment, the
would cardiothoracic surgeon whose
inspired this for the theatre introductions to
vision visits and
project, other
he the he in,
experts which arranged and many meetings which participated
Dr Ian Wright, helped believe in
and whose supervision and motivation me
light
the the the tunnel
at
end of
Special thanks due for the help by those from
are provided staff other
departments found themselves in handling
who my close proximity when
Mr Ray Owen (institute Polymer
unpleasant malodorous material.
of
Technology Materials Engineering)
to instruction
and gave me access and on
testing Mrs Nina Ladner her in Water
materials equipment. and colleagues
Engineering (Dept Civil Building Services Engineering)
of and gave me
to fume lab Their tolerant
access a cupboard, a cold room and equipment.
(often humorous)
to the test
response material was appreciated.
My is to: Dr Paul Lucas (Dept Chemistry), for his
gratitude also extended of
biochemical tissue Mr Alan Baggott, for
advice on aspects of compression;
help; Dr Jamal EI-Rimawi (Dept Civil Building
much and varied of and
Services Engineering), for discussing from
stapling a structural engineering
Mr Jagpal Singh (Dept Manufacturing Engineering), for his
perspective; of
help in the lab; Dr John Ascough, for his both
metrology advice on struts; and
Prof David Williams (Dept Manufacturing Engineering) Dr John Tyrer,
of and
for their
advice on plastic cutting.
Thanks due to Autosuture UK, the
are also who supplied most of stapling
for testing; to Partwell, kindly information
equipment who revealed received
to design
from to EMO,
a consultant; and who used specialised software an
unusualspring.
To Jon, Miles, Amanda, Maurice Janet, thanks for that last-minute help;
and
(and
friends from Loughborough, it's been
to the an education a
rest of my
privilege).
for
Most to Mahroo Sean, loved thanks
of all, and my much wife and son,
to Morag, thanks for kind love to
my mother, your and support,
waiting,
Denise, thanks for being there, to Allan, brother,
my sister, and my nyyyh.
funded
This by from the Department
work was a research scholarship of
Engineering,
Mechanical Loughborough University.
Contents
Page
Summary
Acknowledgements
Contents
iv
Nomenclature
ix
Chapter
1
1 Introduction
1
1.1 Background
2
Circular
1.1.1
3
surgical staplers
Other
1.1.2
6
surgical staplers
1.1.2.1 Linear
6
staplers
1.1.2.2 Linear
7
cutting staplers
1.1.2.3 Ligating
9
staplers
1.1.2.4 Skin 10
staplers
1.1.2.5 MIT 10
staplers
1.2 Current 12
methods and associated problems of anastomosis
techniques in the human digestive tract.
surgery of
1.2.1 The human digestive tract 13
1.2.2 Anastomoses 16
procedures
1.2.2.1 Hand-suturing 16
v stapling
1.2.2.2 Circular 18
stapling
1.3 Historical techniques 23
review of anastomosis and stapling
1.4 Surgical 27
applications
1.4.1 Oesophageal/ 28
gastric work
Gastrointestinal 29
1.4.2
work
Colonic 30
1.4.3
work
1.5 Minimally Invasive Therapy (MIT) 31
Surgical 31
1.5.1
advantages
1.5.2 Technological development 32
Current limitations disadvantages 34
1.5.3
and
1.5.4 A MIT 35
circular stapler-dependent procedure
Circular Currently 36
1.6
staplers- available models
Patent designs 40
1.7
search- alternative
1.7.1 Flexible 40
surgical stapler assembly
1.7.2 Gastrointestinal 41
staplescope
1.7.3 Surgical for delivering
the 42
apparatus
anvil of an
device
anastomosis
iv
flexible
1.7.4 Surgical 43
apparatus with shaft
stapler
for
1.7.5 Variable diameter 44
circular stapler surgical stitching
hollow
of organs
1.7.6 Compression device for the hollow 44
anastomosis of
organs
Chapter 2 Developing
project objectives
Clarified
2.1
46
objectives
Surgical
2.1.1
46
objectives- overview
2.1.2 Detailed
47
surgical objectives
2.1.2.1 Instrument 48
entry
Combined
2.1.2.2 49
entry
2.1.2.3 Securing lumen tissue to 51
stapler
2.1.2.4 Combined 52
approach- assembly connection
2.1.2.5 Approximation 53
of anvil and cartridge
2.1.2.6 Instrument firing 56
2.1.2.7 Anvil 56
withdrawal
2.1.3 A design for MIS 57
product specification a circular stapler
69
2.1.4 Engineering
objectives
69
2.1.4.1 Tissue
compression
2.1.4.2 Firing forces 71
2.1.4.3 Staple line 71
structure
72
2.2 Hypotheses
72
2.2.1 Hypothesis 1
73
2.2.2 Hypothesis 2
73
2.2.3 Hypothesis 3
74
Hypothesis 4
2.2.4
Chapter 3 Experiment Design
75
Experimental
3.1
requirements
75
Tissue
3.1.1
compression
77
Stapler firing
3.1.2
78
Selection
3.2 of apparatus and materials
78
Tissue
3.2.1
preparation
Staple head 78
3.2.2
selection
3.2.3 Test design 79
rig requirements/
Tests 83
3.3
Tissue
3.3.1 83
tests
compression
V
3.3.2 Stapler firing tests 83
Experimental 85
3.3.2.1
method
Chapter 4 Tissue Compression Tests
4.1 Objectives
88
4.2 Materials
89
4.3 Method
91
4.3.1 Gut Preparation
92
4.3.2 Tissue
93
compression and potassium sample collection
4.3.3 Potassium 97
measurement
4.4 Results 99
4.5 Discussion 105
of results
4.5.1 Tissue force 105
compression and compressive
4.5.2 Tissue 105
compression and potassium expulsion
Chapter 5 Firing tests
Objectives 107
5.1
108
5.1.2 Assumptions
109
5.2 Force
measurement
109
5.2.1 Materials
ill
Method
5.2.2
116
Results
5.2.3
118
5.3 Visual identification key firing
of stages
118
Staple deformation
5.3.1
118
Photographic investigation
5.3.1.1
119
Dimensioning
5.3.1.2
122
Results
5.3.1.3
122
Cutting Teflon
5.3.2
annulus
of
123
Microscopic
5.3.2.1
analysis
124
Results
5.3.2.2
125
Results
Discussion
5.4
of
Theoretical interpretation
Chapter 6 of results
129
firing
Stapler
6.1
129
Forming
6.1.1
a closed staple
129
6.1.1.1 Assumptions
6.1.1.2 Mechanical firing 135
analysis of staple
6.1-1.3 Summary forming 153
of staple
vi
6.2.2 Cleaving the teflon annulus with the circular knife 156
6.2.3 Tissue loads
penetration and cleaving 157
6.3 Stapler
161
approximation
6.3.1 Potassium
expulsion and compression 161
6.3.1 Correlation
164
of potassium expulsion
.1
and compression
6.3.2 Load
and compression 168
6.3.3 Summary
of the analysis of tissue compression tests 173
6.3.4 Discussion
174
Chapter 7A Circular Stapler for MIT
7.1 Introduction
176
7.2 An MIT head design
circular stapler 177
7.2.1 Design
177
overview
7.2.1.1 The
177
anvil assembly
7.2.1.2 The
178
cartridge assembly
7.2.1.2.1 Centre
178
shaft
7.2.1.2.2 Staple
180
cartridge
7.2.1.2.3 Firing 181
mechanism
7.2.1.2.4 Locking 182
mechanism
7.2.1.2.5 Release 184
mechanism
Casing
7.2.1.2.6 185
7.2.1.2.7 Overall design 185
concept
7.2.2 Firing force firing 185
and mechanism choice
7.2.2.1 Concept 186
selection
Spring 187
7.2.2.2
selection
7.2.2.3 Cam 188
and spring specification
7.3 Using the theory to improve the design 192
The firing load 192
7.3.1
Staple firing 192
7.3.1.1
Knife 198
7.3.1.2
cleaving
198
Tissue
7.3.2
approximation
Chapter 8 Conclusions 200
Discussion 201
8.1
8.2 Suggestions for further 202
work
8.2.1 Clinical trials 202
8.2.2 A development in 202
possible
understanding
post-operative
stricture
vii