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Official Journal of the
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ISSN: 1983-991X
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| Original Article « PDF file » |
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Evaluation of Intraperitoneal Adhesions Associated with the Double Layer Mesh PTFEe/Polypropylene in the Ventral Hernia Repair - An Experimental Study in Rats
Náthalie Scheeffer Konarzewski1, André Bigolin2, Juliano Montes2, Bárbara Lambert2, Caroline Kist2, João Vicente Grossi, Leandro Totti Cavazzola3
1 Medical Student at University Luterana do Brasil (ULBRA), Canoas, RS; 2 Medical Students at University Luterana do Brasil (ULBRA), Canoas, RS. 3 Master of Science and Doctor of Philosophy in Surgery - UFRGS; Mentor of the General Surgery Internship Programm at ULBRA; Professor of the Medical School ULBRA; PostDoctoral at Case Western Reserve University - Cleveland, Ohio.
ABSTRACT
OBJECTIVE: To compare adhesion formation in two groups of albine rats that underwent intraperitoneal plaement of polypropylene or expanded polytetrafluoroethilene (ePTFE). MATERIALS AND METHODS: Twenty-six female Wistar rats were randomized into three groups. All animals were anesthetized before surgical procedure and were submitted to opening of abdominal cavity for placement of a prosthesis. In group 0 there was no placement of any mesh, in group 1, it was placed polypropylene mesh and in group 2, it was placed ePTFE/polypropylene mesh. All animals were killed 21 days after the procedure and evaluated through organs involved in adhesions, degree of adhesion, percentage of mesh compromised by adhesion and strength needed to rupture these adhesions. RESULTS: Group 1 and 2 had 100% adhesion on prosthesis surface. Group 1 presented 60% adhesion type 1 or 2 and 40% type 3, and group 2 presented 90% type 1 or 2 and 10% adhesion type 3. Both meshes presented the same percentage of surface covered with adhesions, 60% of each type of mesh had surface compromised in less than or 50% and 40% of each kind compromised over than 50% surface of the mesh. Only ePTFE presented 30% adhesion when excluding border adhesion and polypropylene had 100% adhesion. CONCLUSION: Both meshes presented similar behavior regarding the evaluated parameters. However, in an isolated analysis ePTFE has showed to be better than polypropylene as it depictes lower adhesions rates.
Key words: Ventral hernia, ePTFE, Polypropylene, Mesh, Adhesion, Marlex®, Composix®.
Bras. J. Video-Sur, 2009, v. 2, n. 4: 002-010
| Accepted after revision: May, 15, 2009. |
INTRODUCTION
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ore than 2 million abdominal surgeries are
performed annually in the United
States3. Incisional hernia is the most common
complication observed in 11% of the patients submitted to
this surgery and in 23% of the patients who
develop postoperative wound
infection2,5. Repairing incisional hernia corresponds to a hundred thousand
new surgeries every year2,5.
Incidence of incisional hernias after surgical procedures varies from 3% to
40%1. In cases where primary incisional hernia repair occurs
recurrence rates vary from 25% to
52%1,2,3. Complications such as intestinal obstruction and enterocutaneous
fistula depict the necessity to avoid adhesion formation
which causes the procedure to be safe, as 41% to 44%
of the intestinal obstruction due to adhesion need
surgical repair and overall mortality rate reported in
the literature is of 11.4%4.
Due to this elevated rate it is necessary to search high quality synthetic material in order
to improve long-term results of surgical intervention.
The objective of the current study is to compare
adhesion formation between two groups of albine rats
submitted to ventral herniorrhaphy with
intraperitoneal polypropylene or expanded
polytetrafluorethilene/mesh.
MATERIALS AND METHODS
This current study is an experimental study developed in the Biotherium of the
Lutheran University of Brazil (Universidade Luterana do
Brasil-ULBRA) approved by the Research and Ethics Committee of the Lutheran University of
Brazil under the protocol number 2008-004 of this committee.
This research involves 26 female Wistar albine rats which were initially maintained in a
cage with 4 or 5 animals and they were feeding
according to the rules of the research that was being
developed. The size of the sample was calculated according
to literature data21,22,23,24,25,26.
The animals were anesthetized with intramuscular xylazine(0,1ml of 2% solution diluted
in 0,2ml of 0,9% saline solution) at a dose of 5mg/kg
and intramuscular ketamine (0,35ml solution at
50mg/ml) at a dose of 50mg/kg. After an adequate
anesthetic induction was obtained, it was performed an
abdominal tricotomy at the operative field and antisepsis
with 2% alcoholic solution of chlorhexidine in the
same region.
The animals were randomized in three groups. In six animals of the group 0, it was performed a 3
to 4 cm median incision with dissection of the subcutaneous tissue and the peritoneal cavity
was opened through the Alba line. In this group mesh
was not implanted, the abdominal wall was closed and
skin was suture using 3-0 Prolene®.
In ten animals of the group 1, it was performed a 3 to 4 cm median incision
with dissection of the subcutaneous tissue and the peritoneal cavity was opened through the Alba
line. After the cavity was exposed a 2 x 2 cm polypropylene mesh was implanted (Figure 1).
To fix the mesh to the abdominal wall a
transfixing suture in the four quadrants of the mesh
was performed with 4-0 Prolene (Figure 1/2). After
this, the abdominal wall was closed and the skin
was suture with 3-0 Prolene®.
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Figure 1 - Propylene mesh fixation. |
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Figure 2 - Intraperitoneal placement of the polypropylene mesh. |
In 10 animals of the group 2, it was performed a 3 to 4 cm median incision with displacement of
the subcutaneous tissue and the peritoneal cavity
was opened through the Alba line. After the cavity
was exposed a 2x2cm ePTFE/polypropylene mesh was implanted. To fix the mesh to the abdominal wall
a transfixing suture in the four quadrants of the
mesh was performed with 4-0 Prolene. After this, the
abdominal wall was closed and the skin was suture
with 3-0 Prolene® (Figures 3 e 4).
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Figure 3 - ePTFE mesh fixation. |
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Figure 4 - Intraperitoneal placement of the ePTFE/polypropylene
mesh. |
When the procedure finished, all animals were with subcutaneous administration of 0,5ml of
0,9% saline solution and they were placed separately in
a warm room to recover. When the animals were completely awaked they were transferred to their
original cages where food and water were served to
all animals (Figure 5).
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Figure 5 - Organogram of the procedure performed. |
After the procedure and complete postoperative recovery the animals were
daily monitored to evaluate complications to the procedure.
All animals were euthanized in a closed chamber with carbon dioxide on the 21st
postoperative day. Abdominal tricotomy was performed once
again, as well as an "U" incision along the abdominal
wall. The imperfection of the abdominal wall was
repaired in both sides and the abdominal wall was elevated
to evaluate the rate of adhesion, viscera involved in
the adhesion, percentage of the mesh covered with
the adhesion and its rupture strength. The
classification of the adhesion occurred according to table 1.
 |
The evaluation of tension traction was performed using a milimetric ruler with a
5N dynamometer. A repair was placed in the viscus involved and the dynamometer was carefully
pulled, when the adhesion burst it was evaluated the
necessary strength for its rupture.
The dead animals were wrapped and kept under refrigeration according to the rules of
the Biotherium of the Lutheran University of Brazil.
All the data collected were registered in Excel to posterior statistical analysis.
Statistical analysis was performed by Mann-Whitney nonparametric test for the
quantitative variables; Wilcoxon nonparametric test will be
used for comparison (cross frequency and graphics
of columns) of categorical variables (presence or not
of adhesion) analyzed for each type of structure
(Epiplon, Liver, Small Intestine and Round Ligament) and
for comparison of initial and final weight. The
tests presented results of p < 0.05 (5% significance)
for the magnitude of the differences they were
considered statistically significant. SPSS (Statistical Package
for Social Science) version 14.0 was used to analyze data.
RESULTS
In group 0, one animal died due to anesthesia. None of the animals depicted abdominal adhesion
in this group (Figure 6). Only one animal presented
the great omentum suture at the abdominal wall and
it was considered a consequence to the surgical procedure.
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Figure 6 - Animal of the Grupo 0 without adhesion. |
All animals were weighed before the surgical procedure and after their death. The
analysis evaluating the animals weight before and after
surgery was performed through the Wilcoxon test with
5% significance and we could observe that there is
a significant difference between the mean of the
initial and final weight for both types of
mesh(polypropylene and ePTFE/polypropylene), a significant gain of
weight occurred for both type of mesh(p = 0,005). Table
2. This show us that the procedure did not
compromise the animals.
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In the evaluation of the incidence of adhesion by the type of mesh we observed that
polypropylene mesh presented 100% of adhesion (Figure 7) in
which 100% involved the epiplon (Figure 10), 30% the
liver, 30% the small intestine and 60% the round
ligament of the liver. The ePTFE/polypropylene mesh
equally presented 100% of adhesion (Figures 8), in which
90% involved the epiplon, 20% the liver, 30% the
small intestine (Figure 9) and 50% the round ligament
of the liver. There was no significant statistic
difference for these variables as it is observed in table 3.
 |
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Figure 7 - Marlex® mesh adhesion. |
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Figure 8 - Composix® mesh adhesion. |
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Figures 9 and 10 - Adhesion of the bowel loops to the ePTFE mesh. |
It was performed analysis of the maximum strength of rupture of each viscus that constitute
the adhesion process in the meshes. The mean
strength of rupture of each viscus may be observed in table
4. Through the Mann-Whitney nonparametric test
using significance of 5%, we can conclude that there is
no significant difference between the mean of the maximum strength of rupture of the visceras that
were adhered to the polypropylene and ePTFE/polypropylene meshes.
 |
When the degree of adhesion with meshes were evaluated, it was observed that
the polypropylene mesh presented 60% of adhesions
of first and second degree and 40% of adhesions of third degree. The ePTFE/polypropylene
mesh presented 90% of first and second degree
adhesions and 10% of third degree adhesions. Through
the Fisher exact test(p=0,303) at 5% significance
level there was no association between type of mesh
and degree of adhesion. Table 5.
 |
We evaluate the percentage of the area of the mesh affected by the adherence process.
This variable was categorized in two groups (< or equal
to 50% of the surface affected by adhesion in the
mesh or > 50% affected by adhesion). It was observed
that 60% of the polypropylene mesh depicted adhesion
that affected less than or equal to 50% of the surface
of the mesh and 40% depicted adhesion that
affected more than 50% of the surface of the mesh. In
the ePTFE/polypropylene mesh group, it was also observed that in 60% of the meshes, the
adhesions affected a surface less than or equal to 50% and
that 40% depicted adhesion that affected more than
50% of the mesh surface. Through the Fisher exact
test (p=1,000) at 5% significance level, there was
no association between the type of mesh and the percentage of mesh affected by adhesions. Table
6.
 |
We analyzed the ePTFE/polypropylene mesh regarding adhesion at the edges, at the part
exposed to polypropylene and at the center of
the mesh, containing ePTFE. The expanded polytetrafluoroethylene obtained 30% of adhesion,
in which 20% in the epiplon and 10% in the small intestine. The polypropylene showed 100% of
adhesion, in which 50% were in the epiplon, 27,8% in the
round ligament, 11,1% in the small intestine and 11,1% in
the liver. Table 7. Through the Wilcoxon test, at
5% significance level, we can report that there is
significant difference between the adhesions found in the
surface of the mesh containing ePTFE and the ones found
at the edge of the mesh, where the polypropylene
is exposed. In this mesh, the adhesion were predominantly in the part with polypropylene (p=0,005).
 |
Finally, we compared the adhesion found in the center of the ePTFE mesh (excluding from this analysis the adhesion at the edges) with the ones found in the polypropylene mesh. The first presented 30% of adhesion (IC: 0,06 -0,065) while the second presented 100%. As the polypropylene mesh has depicted this rate it was not possible to calculate the upper limit of the confidence interval; however, its lower limit was 0,69. These values are not found in the interval calculate to the ePTFE/polypropylene mesh, proving that this difference is statistically significant to a 95% confidence interval.
DISCUSSION
Approximately 50% of all incisional hernias develop in the first two years after the procedure
and 74% within three years
postsurgery6,7,8,9. It is hypothesized that its formation start from
acute subclinical fascial separations that early occur in
the postoperative setting6,7. During the first 30 days
after surgery, the tensile strength of the suture
decreases resulting in a heavy dependence upon its integrity
to avoid early separation of the
tissues6. Among the symptoms caused by these hernias, we observed
mild abdominal discomfort and pain, as well as
strangulation, incarceration and bowel
obstruction10.
The rate of incisional hernia formation ranges from 3% to 20% after open surgery
repair27. Its recurrence after surgical repair is described in
the literature in the range of 31 to 54% due to
extensive dissection of the tissues for the placement of the
mesh and its large incision27. Polypropylene mesh is the
most commonly used mesh in this situation and the
technique is the placement of a pre-peritoneal
prosthesis retromuscular. The introduction of this type of
mesh in the sixties have represented a significant
decrease in hernia recurrences.
Currently, it is known that hernias formations is due to a biological failure that provokes instability
in the healing process. Therefore the use of
prosthesis is the method of choice in the surgical repair of hernias.
In spite of presenting good tissue integration and little degradation after fixation the
prolypropylene mesh presents some disadvantages that limit its
use, such as the association with adhesion and
fistula formation when in direct contact with the
abdominal cavity. Franklin et al., who have
performed laparoscopic ventral hernia repair with a
polypropylene prosthesis and reported strong adhesions in at
least one-third of the patients who underwent
re-laparoscopy28.
Because of this, there is a necessity of development of a prosthesis that could be
used laparoscopically with satisfactory tissue
integration biologically inert and that could not
produce intraperitoneal adhesions.
Currently laparoscopic repair of these hernias have been evidenced as the best surgical
treatment as it presents shorter hospital day, early return to
daily activities and word, less postoperative pain and
mainly less complications due to the procedure. After
an extensive literature review Cassar e Munro
described recurrence rates to repair incisional hernia
through suture, open repair with prosthesis collocation
and laparoscopic repair of 49%, 10% and until 9%, respectively
.29 Carbajo et al, in 1999
evaluated hernias recurrence in laparoscopy or laparotomy
with prosthesis collocation. The first group did not
depicted recurrence and the second depicted 7% after
27 months29.
Although several studies confirm this superiority, the collocation of prosthesis in
the peritoneal cavity is not yet a standard procedure
in surgery. This is due to the high tendency of
these materials to develop intraperitoneal adhesion,
bowel obstruction and enterocutaneous
fistulas30.
We found in the literature several manuscripts describing the use of polypropylene and
ePTFE/polypropylene prosthesis28,30.
Zigren et al compared the intraperitoneal adhesion between Prolene
and Vypro in pigs and they did not found differences in
the adhesions degree or in its incidence.
BardComposix® mesh is composed of nonabsorbable, hydrophobic,
microporous fluoropolymer of ePTFE bonded to
macroporous prolypropylene. Theoretically, it reduces
adhesion formation at the visceral side of the prosthesis
and increases the percentage of mesothelialization.
It was not observed in the present study difference between the types of adhesions
involved. Both meshes presented epiplon, round ligament of
the liver, small intestine and liver as a consequence of
the adherence process. The incidence of these
adhesions were also similar in both groups, as well as
the maximum strength of rupture of each viscus,
the percentage of the surface of the mesh affected
by the adhesion and the degree of adhesions.
When the exclusive analysis of the mesh composed of ePTFE and polypropylene
was performed we could observe that the adhesions
were predominantly at the edge of the prosthesis,
presenting a percentage of 30% to the ePTFE and 100% to
the polypropylene of this same mesh, as it has been
already described in the literature30.
We presumed that the reason for these findings should be because of the direct contact
of the part composed of polypropylene with the
abdominal cavity. This is due to the fact that in order to
use the prosthesis in the surgical procedure, it should
be cut so it is exposed. It is worthy to emphasize
that these findings do not reflect long-term
consequences of intraperitoneal placement of the prosthesis and
long-term studies should be performed.
CONCLUSION
The two groups were statistically indifferent to all the parameters evaluated. When the ePTFE
is analyzed separately, the Composix mesh depicts as
a suitable option to repair laparoscopically
incisional hernias, due to its potential ability to incorporate
the subjacent tissue provided by the polypropylene
layer and its anti-adherence potential supplied by the ePTFE.
Further studies are necessary to evaluate the long-term consequences of intraperitoneal contact
and to define its real use in the surgical field.
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Correspondence address:
Náthalie Scheeffer Konarzewski
Rua Onze de Junho 1045/204
Novo Hamburgo, RS - Brasil
CEP 93315-130
Email: natikon@brturbo.com.br