Cecorraphy in single layer using polypropylene and poliglecaprone 25 threads . Comparative study in rats

PURPOSE: To compare sutures with polypropylene and poliglecaprone 25 after partial cecotomy in rats. METHODS: Thirty six rats divided into two groups, A and B, of 18 animals; each group was also divided into three subgroups of six animals sacrificed at 4th, 7th and 14th days after surgery. Were studied the mortality, morbidity, complications attributable to sutures, macroscopy, optical microscopy and measurement of hydroxyproline at the level of the suture. RESULTS: There were no deaths or wound complications such as hematoma, seroma, abscess, evisceration or eventration. On microscopic evaluation reepithelization, coaptation and inflammation in both groups did not differ significantly. The average rate of tissue hydroxyproline found in the samples on the 4th day after surgery, was 21.38 mg/g tissue for group A and 16.68 mg/g for group B; on day 7 after surgery, the average was 15.64 mg/g tissue for group A and 26.53 mg/g for group B; on day 14, the average was 8.09 mg/g tissue for group A and 25.07 mg/g for group B. CONCLUSION: There were no differences on clinical evolution, macroscopic aspect, microscopic data and hydroxyproline concentration on both sutures.


Introduction
The digestive suture represents fertile field of medical research.The large intestine, due to its content and its peculiar conditions -such as the presence of large amounts of bacteria in its lumen and the absence of peritoneal lining in some segments -is more prone to anastomotic dehiscence compared to stomach and small intestine [1][2][3][4][5][6][7][8] .
Among the factors reported as associated with large intestine anastomotic dehiscence and septic complications are: bad preparation of the colon for surgery, bad patient's nutritional status, associated diseases, suture in diseased intestine, intestinal ischemia, tension on the suture line, inadequate points of suture, trauma, perforation, use of drains and construction with anastomosis below the peritoneal reflection 1,3,9,10 .
The occurrence of anastomotic dehiscence appears to be most frequent in surgery of the colon in contrast to the small intestine, where this complication is rarely mentioned.Anastomotic dehiscence rates in the large intestine reported in the literature range from 0% to 35% 10 .
Several authors agree that an ideal anastomosis should have no foreign body, be easy, fast and safe, even in cases of increased intraluminal pressure 1,11 .
The sutures had significant evolution over the past 50 years.Initially available as catgut, cotton, silk, linen and steel, nowadays is offered with many different threads.Until the 70s, the only absorbable suture was the catgut obtained from the intestine of animals, rich in collagen fibers.However, even the chromic catgut, is absorbed with an intense inflammatory process and variable absorption time.Were precisely these features -variable absorption time, intense inflammatory process for absorption and the fact that the thread was based on animal proteins -, which led researchers to look for new synthetic absorbable ones 12 .
The polypropylene threads are characterized by being synthetic, nonabsorbable monofilament.It features excellent maneuverability, safety in the knots and low inflammatory tissue reaction.For these good qualities, the suture is widely used in surgery 23,24 .
The aim of this study was to compare the suture with polypropylene and poliglecaprone 25 after partial cecotomy in rats

Methods
Were used 36 rats Rattus norvegicus albinus -Wistar EPM-1, males, weighing between 250 and 328 grams.The animals were housed during an observation period of 15 days, where they were fed with balanced feed for the species and had free access to water.At the end of this period they were submitted to surgery with 12 hours fasting time prior the procedure, but with free access to water.
The rats were anesthetized using ether inhalation and prepared for surgery in the routine way.It was not use bowel preparation or antibiotics.
An abdominal median xiphopubic incision with a scalpel 15 was done interesting all layers of the parietal wall.After inspecting the abdominal cavity and revision of the hemostasis, was identified the cecum, vermiform appendix and ileum.
Cecotomy included the entire anterior surface of the cecum at the site of implantation of the vermiform appendix.Was also identified the posterior wall of the cecum, and proximal and distal ends of the lumen (Figure 1).Cecorraphy in single layer using polypropylene and poliglecaprone 25 threads.
Comparative study in rats Acta Cirúrgica Brasileira -Vol.27 (3) 2012 -253 The cecorraphy was done identically in both groups.Was used continuous suture leaving the fixation knots outside the cecum and producing an overlapping on cecal wall edges, 2 mm from the borders.Abdominal closure was realized with an aponeurotic continuous suture with 5-0 nylon thread with cylindrical needle of 1.5 cm.The skin was approximated with a continuous 5-0 nylon intradermal suture.
In group A the cecum wall was sutured with 5-0 polypropylene using cylindrical needle of 1.5 cm.In group B the same suture was done with poliglecaprone 25.
During the postoperative period, the animals were maintained in box with six rats, identified with the day of surgery and which suture was used.
The animals were examined daily, morning and evening, observing the conditions of the wound and its complications.
The animals in each group were divided into three subgroups of six animals; in group A they were named as subgroups A1, A2, A3, and group B, named B1, B2, B3.The ones in subgroups A1 and B1, A2 and B2, A3 and B3 were sacrificed at 4 th , 7 th and 14 th day after the operation, respectively.They were sacrificed by administering a lethal dose of inhaled ether.
The abdominal cavity was opened far from the surgical incision, removing the operated intestinal segment in a single block.Was observed the presence of abdominal wall seroma, hematoma and integrity of the suture.In the peritoneal cavity, was evaluated the presence of infection, peritoneal adhesions, the integrity of the suture in the cecum and the presence/absence of fistula.Structures or organs that adhered to the cecal suture and/or wall of the cecum, were also removed en-bloc.
The specimen was opened by the middle of the posterior wall of the cecum, and was observed the presence of macroscopic changes in the suture on luminar surface (Figure 2).Before placing the specimens in formaldehyde, was removed a fragment of 0.5x0.5 cm of cecal wall to be used in hydroxyproline dosage.Then, the fragments were processed by usual histological technique for hematoxylin-eosin.From each paraffin block were obtained two slides for histological examination studying the coaptation and inflammation of the tunica serosa, muscle, submucosa and mucosa (Figure 3).

Results
All animals recovered well from anesthesia.During the postoperative course there was no mortality and no wound complications, such as hematoma, seroma, abscess, evisceration or eventration.
The weight variation preoperatively and on the respective dates of sacrifice had no differences.
Microscopic assessment studying separately the serous and muscular coats, mucosa and submucosa according to the criteria of re-epithelialization, inflammation and coaptation, showed similar results (Figure 4).Note: An acute moderate inflammatory process is present in both.
Regarding the dosage of hydroxyproline, the average rate found in tissue samples on the 4 th day after surgery, was 21.38 mg/g tissue for group A and 16.68 mg/g tissue for group B; on day 7 after surgery, the average was 15.64 mg/g tissue for group A and 26.53 mg/g tissue for group B; on the 14 th day after surgery the average was 8.09 mg/g tissue for group A and 25.07 mg/g tissue for group B. After comparative calculations by applying the analysis of variance by ranks of Kruskal-Wallis the results were not statistic different between the groups.Applying the Mann-Whitney test to compare to the subgroups of group A with group B, also no differences were found among all groups (Table 1).

TABLE 1 -Dosage of hydroxyproline in sutures with
polypropylene and poliglecaprone 25.

Discussion
The period of 15 days of preoperative observation was necessary for animals to get used to the environment and food testing.It also served as an observation period to check whether the animals were healthy.It was established no use of bowel preparation and antibiotics due to the fact that rats are successfully resistant to surgical contamination.
Although the good development of intestinal suture in recent years, the large intestine maintain the highest rates of complications (such as fistulas), when compared with small intestine or stomach 3,10 .
The suture of the intestine with the polypropylene is safe, ease to be done and have low inflammatory reaction.These qualities put it near the ideal suture.One of its features that is not consistent with this proposition is that it is nonabsorbable and, therefore, remains indefinitely in the suture line when it is not eliminated in the bowel lumen.
Among the absorbable threads, the catgut was used before the Christian era.It is animal in origin, characterized by large inflammatory response during absorption, which is highly variable in time.The synthetic absorbable polyglycolic acid and polyglactin 910 have absorbable time more uniform, less inflammatory reaction during its absorption, but are multifilament and, so, have the possibility to host bacteria among fibers, a fact that may contribute to the formation and/or maintenance of microabscesses.The absorbable polydioxanone/poligliconate is monofilament and need long absorption time 12,27 .
Was chosen the 4 th , 7 th and 14 th days after surgery to have the evaluation because the inflammatory process is particularly acute in these phases and the overall rate of degradation of collagen is greater than the rate of synthesis, mainly by the 5 th postoperative day.The 7 th postoperative day was chosen because it is around this period of time that occur most enterocutaneous fistulas.In 14 days high collagen rates happen almost similar to the ones in pre-operative period, and also in this period all complications that might exist, occur 10,13,14,15,17,21,33 .
The amount of hydroxyproline follows the collagen presence during the healing process.It is observed that around the 4 th day after surgery its rate get the lowest point, with a tendency for growing from the 7 th day after surgery 6,10,28 .

Conclusion
There were no differences on clinical evolution, macroscopic aspect, microscopic data and hydroxyproline concentration on both sutures using polypropylene and poliglecaprone 25 threads.

Animal number Hydroxyproline
Animal number Hydroxyproline They were operated at the Institute of Medical Research (IPEM) from Post-Graduate Program in Principles of Surgery of the University Evangelic Hospital/Evangelic Faculty of Paraná, Curitiba-PR, Brazil.The animals were divided into two groups of 18, with group A (animals 1 to 18) defined as the control group and group B (animals 19 to 36) experimental group.The surgical procedures were identical in both groups: partial cecorraphy at the same level.The suture were different using in group A polypropylene and in group B poliglecaprone 25.

FIGURE 3 -
FIGURE 3 -Photomicrography of coaptation of the mucosa and submucosa.

FIGURE 4 -
FIGURE 4 -Photomicrograph on the 7 th postoperative day. A. Polypropylene.B. Poliglecaprone 25.Note: An acute moderate inflammatory process is present in both.