Incisional Hernia Prevention By Modication of The Abdominal Wall Closure Technique: Systematic Review And Meta-analysis

Background: Incisional hernia (IH) is the main complication after laparotomy. The objective of this meta-analysis was to evaluate the effectiveness of closure technique modication (CTM) for reducing the incidence of IH to provide objective support for its recommendation. Methods: A meta-analysis was performed according to the PRISMA guidelines. The primary objective was to determine the incidence of IH, and the secondary objective was to determine the incidence of acute evisceration and postoperative complications. Only published clinical trials were included. The risk of bias was analyzed, and the random effects model was used to determine statistical signicance. Results: Nine studies comparing 2,612 patients were inclued. The incidence of IH was signicantly lower in the CTM group than in the control group, with an OR of 0.39 (95% CI 0.26-0.57). The incidence of acute postoperative evisceration was also reduced, with an OR of 0.46 (95% CI 0.23-0.92). Associated complications, including hematoma, seroma, and postoperative pain, could not be analyzed; however, CTM did not increase the risk of surgical site infection. Conclusion: CTM for midline laparotomy signicantly reduces the incidence of IH compared to conventional closure. Limitations of the analysis included differences in follow-up, patient selection, diagnostic methods, and the reporting of postoperative complications among the studies.

complication (1,(16)(17)(18)23,26); however, no closure modi cations have obtained reductions in IH like those obtained with the use of mesh. The objective of this meta-analysis is to evaluate the safety and e cacy of modi ed closure techniques for reducing the incidence of IH and decreasing acute postoperative evisceration and to describe the complications associated with the implementation of these techniques to provide objective support for their recommendation.

Methods
This study was conducted and reported according to the PRISMA 2020 guidelines (19). It was prospectively registered in the PROSPERO database on February 13, 2021, under registration number CRD42021231107.

Data sources and search terms
An electronic search was performed until February 26, 2021, using 8 databases: Web of Science, PubMed, Cochrane Library, SCOPUS, ScienceDirect, Proquest, MEDLINE and Google Scholar. The following terms were used in the search strategy: "abdominal wall closure technique" OR "suture technique for abdominal wall closure" OR "laparotomy closure" OR "midline laparotomy closure" OR "closure of abdominal wall" OR "prevention of incisional hernia" OR "prophylactic of incisional hernia" OR "prevent incisional hernia" OR "adjuvant to abdominal wall closure" OR "prevent fascial dehiscence" OR "prophylaxis of incisional hernia" OR "abdominal closure hernia prevention" AND "randomized clinical trial" NOT "mesh" NOT "prophylactic mesh reinforcement".

Study selection, data extraction and quality assessment
The title and abstract of the studies were analyzed to determine their eligibility. This analysis was performed by 3 independent reviewers. After this rst review, the full text of considered studies was evaluated, and only clinical trials were included. The methodological quality of the studies was evaluated using the Scottish Intercollegiate Guidelines Network (SIGN) guidelines, and the risk of methodological bias of the studies was assessed using the Cochrane Collaboration tool (20). The following aspects were analyzed: random sequence generation; allocation concealment; blinding of patients, staff, or assessors; blinding of researchers; incomplete outcome data; selective reporting of results; and other sources of bias. The evaluation of the methodological quality and risk of bias was performed by 3 independent reviewers, and the studies were identi ed as having a low or high risk of bias. Any disagreement regarding the selection of a study was resolved by consensus.
Only controlled and randomized clinical trials that met the following inclusion criteria were included: patients older than 15 years, elective or emergency surgery, midline laparotomy only, high, or low risk of IH, regardless of the cavity characteristics during the intraoperative period (clean, clean-contaminated, contaminated, or dirty), and modi cation of the typical abdominal wall closure technique. The primary objective of the review was to determine the incidence of IH, as de ned in each study. The secondary objective was to determine the incidence of acute postoperative evisceration (wound dehiscence), and the third was to determine the presence of complications associated with each type of closure: surgical site infection, hematoma, and seroma. There was no language restriction, and only results from published studies were included.
A table was created that synthesized the included articles that were identi ed in the search. The table included the following information: study characteristics (author, year of publication and number of patients included), inclusion/exclusion criteria, details of the technique modi cation and control group, outcomes, IH diagnostic method and follow-up time.

Statistical analysis
A meta-analysis was performed in which the results of the analyzed studies were grouped. A sensitivity analysis was performed to reduce the risk of bias of the primary objective reported in the studies; additionally, a subgroup analysis was performed to evaluate the incidence of acute evisceration and complications. The odds ratio (OR) and its 95% con dence interval (CI) were calculated with a random effects model, and the effect was considered statistically signi cant if the 95% con dence interval did not include 1. The I 2 statistic was calculated to evaluate heterogeneity.
The bias analysis was reported using funnel plots and the Egger's test was used to assess publication bias. These analyses were performed using Review Manager software (RevMan version 5.3), and a p-value less than 0.05 was considered statistically signi cant.

Results
A total of 552 articles were identi ed as potentially eligible in the different databases. After duplicate articles were removed, the title and abstract were reviewed, studies that did not meet the inclusion criteria were removed, 25 articles were chosen. After the full text was read, 16 articles were excluded: 8 because they compared different types of suture material; 2 because they included different types of incisions in addition to midline incisions; 4 because they were protocols of ongoing studies; and 2 because they were protocols of published studies ( Figure 1). In total, 9 clinical trials met the inclusion criteria (1,(16)(17)(18)(21)(22)(23)(24)(25)(26). Their risk of bias was analyzed and is reported in Figures 2 and 3.
A total of 2,612 patients were included in the 9 analyzed clinical trials, and the study and patient characteristics are shown in Table 1 Figure 4 shows these techniques.
The general inclusion criteria were as follows: undergoing midline laparotomy, emergency, or scheduled surgery; patients older than 15 years; and modi cation of the laparotomy closure technique. The individual inclusion criteria were diverse and included emergency or scheduled surgery, generalized peritonitis, incision longer than 10 cm, malnutrition, emergency surgery or contaminated surgery, use of steroids, hemodynamic instability, hemoglobin <10 mg/dL, prediction of postoperative abdominal distension (ascites or ileus), bilirubin >3, diabetes, rectal cancer surgery or a score >6 on the Rotterdam scale. Table 1.
The control group: in six studies were standardized to large-bite closure at 1 cm from the wound edge with 1-cm advancements (1,16,18,21,23,25). Two studies do not clearly describe the procedure used for the control group, but both used nonabsorbable or slowly absorbable no. 1 suture, and most used continuous suturing (22,26) Only one study used interrupted fascial closure in the control group (24). Table 1.

Outcome measurement
The main outcome evaluated was the incidence of IH. The follow-up duration was not uniform and ranged from 6 months to 3 years. Only studies that had a minimum follow-up of one year were included in the analysis of the primary outcome, thus ve articles were included in the global quantitative analysis of this outcome, and the risk of bias was evaluated (1,16,18,23,25). The meta-analysis showed a statistically signi cant reduction in IH in patients who underwent modi ed closure compared to patients who underwent conventional closure (OR 0.39, 95% CI 0.26-0.57) ( Figure 5a). The funnel plot showed high asymmetry, with an I 2 of 24% and a p-value of 0.26, which indicates a low risk of bias ( Figure 5b).
The secondary outcomes were the presence of wound dehiscence and complications associated with the closure type.
Regarding wound dehiscence, 9 articles were included in the quantitative analysis. The global meta-analysis showed a statistically signi cant difference in the reduction of the incidence of evisceration with the use of a modi ed closure technique compared with conventional closure (OR 0.46, 95% CI 0.23-0.92) (Figure 6a). The funnel plot showed low asymmetry, with an I 2 of 47% and a p-value of 0.06, which indicates a high risk of bias ( Figure 6b).
Regarding complications associated with the closure type, there was not su cient data to compare the presence of seroma, hematoma and pain or quality of life (Table 2). One study did not report this complication. Only the presence of surgical site infection could be compared; the meta-analysis showed that there was no signi cant difference between patients who underwent modi ed closure compared to patients who underwent conventional closure (OR 0.83, 95% CI 0.66-1.05) (Figure 7a). The funnel plot showed high asymmetry, with an I 2 of 0% and a p-value of 0.48, which indicates a low risk of bias (Figure 7b).

Discussion
The present study showed that modi cation of the closure technique for midline laparotomy signi cantly decreases the incidence of IH compared to conventional closure. This signi cant effect was identi ed for 3 techniques: small bites, RTL, and retention sutures. The use of retention sutures showed a decrease in the occurrence of IH; however, the retention sutures were removed at 3 or 4 weeks, and after the 4th day, greater pain was reported for this group than for the control group; other studies have used this type of closure with contradictory results, and it has been suggested that it should only be used in high-risk patients (27).
The small bites technique is currently the one with the most scienti c evidence of its effectiveness for reducing the incidence of IH. The EHS recommends its use in low-risk patients, and efforts are being made to make its use widespread (28-30). In both studies in which the small bites technique was used (1,23), it was applied in patients with different degrees of IH risk, the follow-up time was 1 year, and no bene t was found for reducing the incidence of postoperative evisceration; however, it should be noted that the incidence of this complication was very low, and thus, the usefulness of the technique cannot be objectively determined. The RTL technique was used in 2 studies (18,26) that demonstrated its usefulness for reducing the incidence of IH; it was performed in high-risk patients, in 1 study the follow-up time was 3 years, and both studies found that its usefulness for reducing the incidence of postoperative evisceration was good.
The meta-analysis also showed that modi cation of the closure technique is safe and does not increase the risk of surgical site infection; however, this relationship could not be con rmed for other complications.
The limitations of this meta-analysis include the great variety of techniques used for closure of the abdominal wall, which makes it di cult to recommend a single technique. There was low heterogeneity regarding the presence of IH, but the analysis of the presence of evisceration and/or eventration showed very high heterogeneity resulting from the variability in the closure techniques used and the selection of study subjects, as previously stated.
A great variety of techniques were used to modify the conventional closure technique, and the suture length/wound length ratio (SL/WL) and compliance with the Jenkins rule were only reported for the small bites and RTL techniques; hence, adherence to the appropriate closure method in the control groups was not clear. Only the RTL and retention suture techniques showed e cacy for reducing both complications -IH and evisceration -but the use of retention sutures had the disadvantage of associated postoperative pain.
Another limitation in the nal analysis was the duration of follow-up for reporting the incidence of IH, as the range was very wide, six months (1), one year (22)(23) or three years (18). The selection of participants also differed for all the studies, and there was no standardization of high or low risk, similar studies examining the use of other closure techniques, such as mesh.
In most of the studies, only clinical follow-up was used to determine the presence of IH, and only 2 studies reported the use of ultrasound and computed tomography. Hence, the use of imaging techniques could increase the number of patients diagnosed with subclinical IH and provide a more accurate estimate of the effect of these interventions on decreasing this complication.
When the overall outcome of IH was analyzed, the group that underwent a modi ed closure technique had an IH incidence of 9.5%, compared to 20% in the patients who underwent conventional closure. Both rates are like the results reported with the use of mesh. Currently, there are ongoing studies comparing the use of these modi ed closure techniques with the use of mesh, and in the future, these studies may provide objective support for the use of one technique over another.
Another important issue is de nition of the criteria used to determine which patients should be considered high-risk.
The studies included in this meta-analysis had highly varied inclusion criteria and considered different factors when determining this risk. Only one study used a validated scale, (although this validation was for wound dehiscence a not for IH) (18) to de ne high and low risk. However, there is still no consensus in the literature on any useful scale for predicting which patients should be considered high or low risk.

Conclusions
This meta-analysis showed that modi cation of the closure technique for midline laparotomy signi cantly decreases the occurrence of IH compared to conventional closure.
The results showed that only the small bites, RTL and retention suture techniques decrease the presence of IH, and that only RTL and retention suture techniques decrease the incidence of postsurgical evisceration, but retention suture technique present greater postoperative pain when compared with the usual technique and in other non-randomized studies and not included in this meta-analysis present controversial results.
Due to the great variety of techniques used and the differences in the inclusion criteria for the control group, a technique of choice cannot be established. At this time, different studies are being conducted to compare the effectiveness of these techniques with the use of meshes, which should lead to an objective recommendation. abdominal fascia (except peritoneum) on each side. The rst retention suture was placed 5 cm above the lower end of the incision and repeated every 10 cm toward the upper part of the incision (Figure 4).

Abbreviations
Control group: the fascia was sutured continuously using a running looped #1 nylon string located 1 cm from the edge of the linea alba with 1-cm intervals. The running suture was locked intermittently every 5 cm to divide the long continuous suture into multiple smaller sections. Subcutaneous tissue was not sutured, and skin was closed using interrupted suture of 3-0 nylon.

Deerenberg 2015
Patients aged 18 years or older, elective abdominal surgery. Excluded patients with a history of incisional hernia or fascial dehiscence after midline laparotomy, those who had undergone abdominal surgery through a midline incision within the past 3 months, those who were pregnant, or those who had participated in another intervention trial.
The suture technique was applied with tissue bites of 5 mm and intersuture spacing of 5 mm. In all cases the stitch incorporated the aponeurosis only and incorporation of fat or muscle tissue was avoided ( Figure 4). Smead-Jones closure technique of far-near and near-far suturing was interrupted. But we proposed continuous farnear and near-far suturing technique as modi ed Smead-Jones technique, which was used for midline fascial closure in the study group. In this technique suturing was done with points 'A' and 'D' being 1.5 cm away from the edge of the fascia and points 'B' and 'C' being 0.5 cm away from the fascial edge. The distance between two successive continuous sutures was not more than 1 cm. There was one 2 x 1 x 1 x 1 surgical knot at each end of laparotomy wound (Figure 4).
In the controlled arm, midline closure was done with interrupted sutures 1.5 cm away from the cut margin/edge of fascia tied every time with 2 x 1 x 1 x 1 surgical square knots. Again, distance between two consecutive sutures was not more than 1 cm.

Supplementary Files
This is a list of supplementary les associated with this preprint. Click to download. PRISMA2020checklist.docx