Repair of large incisional hernias . To drain or not to drain . Randomized clinical trial

PURPOSE: To evaluate the occurrence of seroma and surgical wound infection after surgery. METHODS: A total of 42 individuals with large incisional hernias were subjected to onlay mesh repair. Following the mesh placement, the participants were randomly allocated to two groups. In group 1, closed-suction drains were placed in the subcutaneous tissue, while progressive tension sutures were performed in group 2. The participants were subjected to clinical and ultrasound assessment to detect seroma and surgical wound infection at three time-points after surgery. RESULTS: The occurrence of seroma at the early, intermediate or late assessments was respectively 19.0%, 47.6%, 52.4% in group 1 and 28.6%, 57.1%, 42.9% in group 2 and was not significantly different between groups (p 0.469; 0.631; 0.619). Surgical wound infection occurred 19% in group 1 and 23.8% in group 2, without a significant difference between the groups (p>0.999). CONCLUSION: The frequency of seroma and infection did not exhibit significant differences between individuals subjected to onlay mesh repair of large incisional hernias with drains or progressive tension sutures without drainage.


Introduction
In three to 26% of the patients subjected to surgical opening and closure of the abdominal wall, closure might fail, followed by late separation of the muscular-aponeurotic layers, which is known as incisional hernia 1 . Most incisional hernias require surgical repair, which is associated with a high incidence of complications, among which seroma formation and infection stand out 2 . Although drains are placed at the end of surgery as an attempt to prevent such complications, there is no concrete evidence in the literature demonstrating their actual benefits or whether they might actually increase the incidence of infection [3][4][5] . Other techniques are also used to prevent seroma formation, including progressive tension sutures, which are recommended by some authors for abdominoplasty [6][7][8] . A Cochrane systematic review on the prophylactic use of drains following incisional herniorrhaphy did not locate any study demonstrating their usefulness 9 . We conducted a randomised clinical trial to compare the incidence of seroma and surgical wound infection between patients subjected to large incisional hernia repair by means of the onlay technique, with one group being subjected to the placement of drains, while progressive tension sutures without drains were used in a second group.

Methods
The present randomised clinical trial was approved by the research ethics committees of School of Medicine, Universidade The study design and randomisation followed the Consolidated Standards of Reporting Trials (CONSORT) version 2010 10 .
The study was register in clinicaltrials.gov public site with the identifier NCT02163460.
All the participants read and signed an informed consent form during the preoperative assessment visit.

Inclusion and exclusion criteria
Individuals with primary or recurrent incisional hernia were assessed at HUOP, and those with longitudinal or transverse ventral hernia secondary to a previous surgical incision, measuring 5 to 15 cm after dissection of the hernial sac and classified as large or very large according to Chevrel's classification, were considered to be eligible 11 . In individuals with multiple defects, the length between the cranial margin of the most cranial defect and the caudal margin of the most caudal defect was considered 12 .
Individuals subjected to emergency surgery, with infection, immunosuppressed, younger than 18 or older than 80 years old, ASA III or IV, with a serum albumin concentration lower than 3.0 g/dl or who refused participation were excluded from the study.

Surgical technique
The participants were admitted to the hospital the night before surgery to perform or update the assessment of their surgical risk according to the American Society of Anesthesiologists (ASA) criteria, as well as for measurement of the serum albumin concentration.
Incisional herniorrhaphy surgery was performed following the group's technique systematisation by a resident physician supervised by one of four surgeons professors at the medical course of UNIOESTE and who the using the onlay technique as described by Chevrel 13,14 . Antibiotic prophylaxis was performed with a single 2g dose of cefazolin at the time of anaesthetic induction followed by a booster 1g dose when the surgery lasted more than three hours. Skin closure was performed with simple separate sutures at 1 cm intervals using 4-0 nylon monofilament suture in both groups. Before closing, the skin excess and the previous scar was removed.
The participants were requested to use the support girdles provided by the surgical staff at the hospital and at home during the first 30 days after surgery.
In group 1, the drains were removed when the drained volume was less than 40 ml/24 hours.

Sample size calculation
The sample size was calculated based on significance level alpha = 5% and 80% power. A two-tailed test for the comparison of the two proportions was used to compare the occurrence of seroma between the groups with drains (50.0%) or progressive tension sutures (10.0%). These references reflect the incidence of seroma in the literature with these techniques in case series and clinical trials and that we considered clinically relevant 4,8,17 .

Statistics
The initial statistical analysis of all the data collected in the present study was descriptive. In regard to the quantitative (numerical) variables, summary measures including mean, standard deviation, median, maximum and minimum values were calculated, and one-dimensional scatterplots were constructed.
The data corresponding to the qualitative (categorical) variables were assessed as absolute and relative (percent) frequencies.
Inferential analysis was performed to confirm or refute the evidence found in the descriptive analysis. For that purpose, Student's t-test for independent samples was used to compare the groups of participants.
In the inferential analysis, the significance level (α) was established as 5%. The statistical analyses were performed using software R version 2.15.2. in recurrent hernias and 62.5% for non-recurrent hernias. There was no significant difference between the cases recurrent or nonrecurrent in the development of seroma (p=0.451) or postoperative infection (p=0.660).

Results
The participants were randomised to receive subcutaneous drainage or progressive tension sutures. There was no loss of follow-up and all cases were analysed. No participant died or exhibited recurrence of hernia along the 30-day postoperative follow-up.
The average time elapsed from hernia diagnosis to surgery was 42 months, varying from three to 300 months.
Only five patients required relaxing incisions, two from group 1 and three from group 2. The results of the inferential comparison show that both group 1 (drains) and group 2 (progressive tension sutures) exhibited the same profile (Table 1).   The most widely used procedure to prevent seroma formation consists of the placement of drains in the subcutaneous tissue; however, several studies indicated that drains not only fail to prevent seroma formation but may even increase the risk of infection 3,4 . A Cochrane review on this subject did not find any evidence demonstrating a benefit of the use of drains 9 .
The fixation of the subcutaneous tissue to aponeurosis, which seemingly reduces the dead space and minimises the shear forces, was originally described by Baroudi and Ferreira in 1998 for abdominoplasty without drainage 6 . Further detail was added by Pollock 7 , and the technique was then reproduced by others [21][22][23] .
In 2012, Janis, from the University of Texas, suggested to using the progressive tension suture technique in large incisional herniorrhaphy procedures 24 . Some authors, such as Birolini C, highlights the importance of fixing the mesh to the aponeurosis with running sutures of absorbable polyglactin to prevent the formation of dead space and complications 25 .
In the present study, the frequency of seroma formation did not exhibit significant difference between the groups, and most seromas were detected at the intermediate assessment when all the drains had already been removed. These findings agree with the results reported by other authors, according to which the peak incidence of seroma formation occurs approximately two weeks after surgery, when prophylactic drains would be useless 6,21,26  The occurrence of surgical wound infection was high in the present sample (21.4%) and did not correlate with any of the assessed variables, nor did its incidence exhibit significant difference between the groups. That lack of correlation and differences might have been due to beta error, as the sample size had not been calculated for that outcome. In the study by Memmon 28 , the incidence of infection among individuals with a profile similar to that of the participants in the present study and subjected to the same surgical procedure was 21.67%. Most studies that reported on the occurrence of infection did not explain how the diagnosis was performed, and most of them are retrospective studies. For those reasons, we believe that our results exhibit less bias and are closer to the real situation in large surgical procedures performed with the onlay technique. In the study conducted by Barbaros 29 in 2007, the incidence of infection was reported as 0%; however, the mesh had to be removed in 17.3% of the cases, which can only be justified by the occurrence of infection. In a prospective randomised clinical trial, Misra 30 detected infection in 33% of the patients subjected to the onlay technique. In some retrospective case-series, the reported incidence of infection was 0%, which we believe not to be possible in this group of patients 13 . As a function of the discrepancy among the data available in the literature, we suggest that all studies employ the CDC criteria for the diagnosis of infection in a prospective manner 16 .

Conclusions
There was no significant difference in the incidence of seroma formation or surgical wound infection between the individuals who underwent placement of continuous suction drains in the subcutaneous tissue and those treated with the progressive tension suture technique. The incidence of both complications was high, and thus novel surgical techniques should be investigated for their prevention.