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Year : 2019  |  Volume : 17  |  Issue : 1  |  Page : 96-102

Comparative study between onlay and sublay repair of ventral hernia

Department of General Surgery, Faculty of Medicine for Girls, Al Azhar University, Cairo, Egypt

Date of Submission26-Mar-2019
Date of Acceptance02-Jun-2019
Date of Web Publication12-Sep-2019

Correspondence Address:
Radwa M Mohamed
Lecturer of General Surgery, Department of General Surgery, Faculty of Medicine for Girls, Al-Azhar University for Girls, 65356
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/AZMJ.AZMJ_60_19

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Background Ventral hernia is one of the most common surgical operations performed all over the world. Surgical repair is done using prolene mesh and can be placed over anterior rectus sheath (onlay) or in preperitoneal space. However, the debate still continues about the superiority of each technique over the other.
Aim To study operative time, easy of procedure, early postoperative complications, duration of hospital stays, recurrences, and outcomes of the onlay versus sublay mesh repair.
Patients and methods One hundred patients with paraumbilical, epigastric, and supraumbilical incisional hernias were included in this study and were managed at Al Zahra Hospital. Patients were divided into two main groups: group A underwent onlay mesh repair and group B sublay mesh repair. The patients included were evaluated for operating time, postoperative seroma formation wound infection, drain duration, postoperative hospital stay, and recurrence of symptoms.
Results A total of 100 patients were operated in our study: 50 patients were in group A and 50 patients in group B. The mean operative time in group B was 70±18.50 min and in group A was 50±12. The duration of hospital stay was on an average 1–3 days in group B, and average hospital stay was 2–4 days in group A. In the group B, the drain was removed after 2–3 days, and in some patients with small defect, there was no need for putting a drain, but in group A, the drain was removed after 2–5 days, except for one patient with large supraumbilical incisional hernia, where drain was removed after 10 days. Postoperative complications like a seroma and wound infection were comparable in both groups.
Conclusion Sublay mesh repair is a better technique with less incidence of seroma formation, a lower rate of postoperative compilations like infection and wound edge necrosis, no recurrence rate, and minimal mesh related-compilations.

Keywords: mesh plasty, mesh repair, onlay, sublay, ventral hernia

How to cite this article:
Mohamed RM, Rabie OM. Comparative study between onlay and sublay repair of ventral hernia. Al-Azhar Assiut Med J 2019;17:96-102

How to cite this URL:
Mohamed RM, Rabie OM. Comparative study between onlay and sublay repair of ventral hernia. Al-Azhar Assiut Med J [serial online] 2019 [cited 2021 Jun 14];17:96-102. Available from: http://www.azmj.eg.net/text.asp?2019/17/1/96/266738

  Introduction Top

Ventral hernias are commonly encountered in surgical practice. The estimated incidence of ventral hernia is 15–20%, and the implantation of prosthetic mesh remains the most efficient method of dealing with a ventral hernia [1].

Abdominal wall hernias occur only at the site where aponeurosis and fascia are not covered by striated muscles, that is, inguinal, femoral, umbilical area, linea alba, a lower portion of semilunar line, and sites of previous incisions [2]. In developing countries, such hernias are not treated on a priority basis because of their benign nature in general and owing to economic reasons. Among the common ventral hernias, incisional and paraumbilical hernias constitute ∼85% of the overall ventral abdominal hernias [3].

To avoid recurrence, a variety of materials were tried to reinforce the repair via fascial autographs, prosthetic materials, a mesh of various types, and the technique of placements including onlay and sublay, but the best position for inserting the mesh has not been conclusively established. The preperitoneal (sublay) mesh hernia repair was first described by Renestopa, Jean Rives, and George Wantz. This technique is considered by many surgeons to be the gold standard for the open repair of ventral hernia [4].

Repair of ventral hernia is an ongoing challenge in surgical practice, and the two operative techniques most frequently used in the repair of ventral hernia are onlay and sublay through either direct suture technique or use of various type of mesh for strengthening of muscle fascial tissue to avoid recurrence, and it remains unclear which technique is superior [5].

Onlay repair is believed to be easily performed and has less time of operation, but sublay repair is most efficient regarding lower recurrence rate [6].

  Patients and methods Top

The study was carried out on 100 patients with ventral hernia admitted to the Department of General Surgery at Al Zahra University Hospital from July 2016 to July 2018, excluding patients with uncontrolled diabetes and recurrent and very large incisional hernia, with defect more than 6 cm. The study is approved by the ethical committee of Faculty of Medicine, Al-Azhar University for Girls, Egypt. Patients were divided into two groups:
  1. Group A: onlay mesh over the external oblique (50 cases).
  2. Group B: sublay mesh preperitoneally (50 cases).


Inclusion criteria

All patients with ventral hernia, including paraumbilical, epigastric, and incisional, except with defect more than 6 cm, between 20 and 65 years of age without sex discrimination were included.

Exclusion criteria

The following were the exclusion criteria:
  1. Patients under the age of 20 years.
  2. Groin hernia and complicated hernia.
  3. HIV, HBSAO, HCV, and immunocompromised patients.
  4. Pregnancy.
  5. Recurrent hernia.
  6. Incision hernia with defect more than 6 cm.
  7. Patients with liver cirrhosis and end-stage liver disease.
  8. Patients with abdominal malignancy.
  9. Chronic obstructive pulmonary disease.


  1. Preoperative: these data were collected at the time of admission, for example, the name, age, sex, address, and phone number. Preoperative counseling was done. Fully informed written consent was taken. The clinical features and their duration, time of initial operation, and the interval between the first surgery and appearance of incisional hernia were asked from the patients and recorded in the data in cases of incisional hernia. Preoperative assessment included evaluation of patients for general anesthesia and routine laboratory tests, including complete blood count, kidney functions tests, liver function tests, prothrombin time, international normalized ratio, electrolytes, blood group, chest radiography, ECG, echocardiography, and respiratory function tests if needed.

  2. Operative technique: an abdominal incision was made according to the type and site of hernia defect. In group A, the skin and subcutaneous layers were incised, and the hernia sac was identified. The sac after that was opened, and if there were any adhesions, they were released. Dissection was done over rectus sheath all around with excision of the sac, and closure of the defect was done with nonabsorbable polypropylene sutures, and then polypropylene mesh was placed above musculoaponeurotic layer (onlay) and fixed with prolene 2/0 sutures. Hemostasis was done with putting of suction drain in the subcutaneous plane ([Figure 1],[Figure 2],[Figure 3]).
    Figure 1 Dissection with excision of sac in group A.

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    Figure 2 Closure of the defect with prolene.

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    Figure 3 Mesh placed over rectus sheath (onlay).

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  3. The principles of the preperitoneal or retromuscular mesh repair include mesh placement deep to the recti muscles, peripheral suture fixation, mesh extension well beyond the hernia defect, and closure of the fascia over the mesh. Fibrous tissue ingrowth in the mesh pores consolidates the abdominal wall and widely disperses intraabdominal pressure to prevent recurrence. This technique involves the placement of prosthetic mesh (Polypropylene) in a preperitoneal plane ([Figure 4],[Figure 5],[Figure 6],[Figure 7],[Figure 8]).
    Figure 4 The skin incision was placed directly over the hernial defect.

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    Figure 5 Incision with appearance of defect.

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    Figure 6 Creation of plane between posterior sheath and the rectus muscle before putting mesh.

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    Figure 7 Prolene mesh is placed in the plane created behind the recti creation of plane between posterior sheath and the rectus muscle.

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    Figure 8 After closure in group B.

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  4. Postoperative: early postoperative evaluation involved early mobilization with early oral nutrition. Usage of NSAIDs as a pain killer was initiated. The hospital stay of the patients was recorded. Wound site was checked for infection in all patients in the early postoperative period in both groups.

Late postoperative: monthly follow-up was done till 1 year, thereafter every 3 months, then every 6 months, and then annually to detect the rate of recurrence. One year follow-up revealed no recurrence in the group B.

In our study, 15 cases of incisional hernia with defects less than 6 cm, 25 case of paraumbilical hernia, and 10 cases of epigastric hernia were managed by onlay mesh repair, and 17 cases of incisional hernia, 23 cases of paraumbilical hernia, and 10 cases of epigastric hernia and 17 patients with incisional hernia were managed by sublay mesh repair ([Table 1]).
Table 1 Types of hernia in the studied patients (N=100) of both groups

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Observation in both groups was made regarding duration of surgery, postoperative complication like seroma formation and wound infection, placement and duration of the drain, hospital stay, and recurrences. Follow-up was done every 3 months for 12–24 months to see late wound complications like sinus, neuralgia, and recurrence. All patients were given cefotaxime 1 gm intravenous on induction; thereafter, intravenous antibiotics were continued for 2 days postoperatively and changed to oral twice daily for the next 5 days.

  Results Top

The total of 100 patients was operated in this study, comprising 35 men and 55 women. The mean age of our study patients ranged between 25 and 65 years. In group B ([Table 2]), the operative time was 70±18.50 min compared with 50±12 min in group A. A suction drain was put in all cases of incisional hernias repair in sublay group and was removed after 2–3 days, and in some cases, there was no need for putting a suction drain, which is considered one of the main advantages of sublay repair, which is not done in onlay repair, where the only drain was put in all cases of incisional, paraumbilical, epigastric hernia and was removed after 2–7 day ([Table 3]).
Table 2 Demographic data of the studied patients (N=100) in both groups

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Table 3 Duration of the operation, size of the defect, and hospital stay in studied patients of both groups

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Postoperative complication like a seroma and wound infection were comparable in both groups in sublay group. Seroma was seen in 2% (one patient only), wound infection in 2% (one patient only), and no septic mesh was removed.

In the onlay group, seroma formation was 16% (eight patients). Most of the seroma occurred in large incisional hernia. Wound infection was 6% (three patients), and two (4%) patients had septic mesh, which was removed.

In the sublay group, recurrence was 0%, and in the onlay, the recurrence rate was 4% (two patients). Wound edge necrosis occurred in two (4%) cases of the onlay repair, which was managed by excision of necrotic edge and primary suture, and no cases of flap edge necrosis were seen in the sublay group ([Table 4]).
Table 4 Early and late postoperative complications (N=100) in both groups

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  Discussion Top

The repair of ventral hernias varies from primary closure only, primary closure with relaxing incisions, primary closure with onlay mesh reinforcement, onlay mesh placement only, inlay mesh placement, and intraperitoneal mesh placement. Primary closure techniques are usually performed for small fascial defects less than 5 cm in greatest diameter [6].

Ventral hernia either de novo or recurrent is a common surgical problem, encountered in surgical practice, accounting for 15–20% of all abdominal wall hernias and refers to a fascial defect in the anterolateral parietal abdominal wall fascia and muscles through which intermittent or continuous protrusion of intraabdominal or preperitoneal contents occurs [7].

Mesh repair is an excellent method of repair, preferred for patients with a large defect in the anterior abdominal wall, especially with more than 4-cm size detect. An excellent method that had been used is called Rives-Stopa technique, where mesh was placed between the peritoneum and abdominal wall or rectus muscle and posterior rectus sheath [8].

The reinforcement of sublay technique decreased the recurrence rates and gave a better outcome, concluding it to be the standard of care of ventral hernia [9].

In our study, we evaluated 100 patients who were followed up for 12–24 months. They were treated by two methods: 50 patients treated by sublay technique and 50 patients were treated by onlay technique. Overall, 32 patients had incisional hernia with defect less than 6 cm, 48 patients had paraumbilical hernia, and 20 patient had epigastric hernia. The studied patients comprised 35 (35%) males and 65 (65%) females, with age range between 25 and 65 years.

The main advantage of preperitoneal mesh repair is less chance of mesh infection and erosion through the skin because the graft lies in a preperitoneal plane between posterior rectus sheath and peritoneum, avoids adhesions, bowel obstruction, enterocutaneous fistula, and erosion of mesh, and has minimal morbidity. The main disadvantages are more time consumption, extensive preparation of preperitoneal plane, and surgical experience [10].

The mean duration of surgery in patients treated with onlay mesh repair was 50±12 min and duration of surgery in patient treated with sublay mesh repair was 70±18.50 min. In the study conducted by Gordara et al. [11], the mean time for surgery in the onlay group was 49.35±8.29 min (30–90 min) compared with 63.15+15 min (36–96 min) in the sublay group.

The length of hospital stays in our study in patient treated with onlay technique was 8±2 days and in patients treated with sublay was 7±1 days, whereas in the study by Godara et al. [11], mean duration of hospital stay was 6.8±1.50 days in sublay and 4.6±1.30 days in onlay group. Moreover, Voeller and Mangiante [12] reported mean hospital stay of ∼5.8 day in sublay group and 4.5 in onlay group.

The study by Saber et al. [13] found the mean operative time for onlay repair was 67.09±13.19 min (range, 45–90 min), whereas for sublay was 93.26±24.94 min (range, 60–140 min).

In our study, the mean operative time was longer in sublay than onlay group owing to the time consumed to create the preperitoneal tunnel. Our data are in agreement with other reported studies.

As the operative time in sublay group patients was much longer than in the onlay technique, our study shows postoperative seroma formation in onlay technique occurred in eight (16%) patients and in sublay technique occurred only in one (2%) patient. Seroma formation is a common complication after repair of abdominal wall hernia.

The predisposing risk factors in both groups that resulted in hernia formation were benign prostatic hyperplasia in 10 (10%) cases, chronic constipation in nine (9%) cases, obesity in 25 (25%) cases, and smoking in 15 (15%) cases ([Table 5]). Most patients had multiple risks for developing ventral hernia, but obesity is considered one of the main risk factors of both groups.
Table 5 Risk factors in the studied patients (N=100) in both groups

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Other studies reported that the rate of seroma formation in sublay repair is much less than onlay repair [13].

Numerous studies were done to understand the hernia mechanism and the methods of repair. All studies stressed on managing hernia defects as a part of the generalized abdominal wall problem [14].

The postoperative wound infection occurred in onlay group was three and in the sublay group was one, which is lower than occurred with onlay group. Another study reported that infection occurred in 11.6% of cases in the onlay group, which is more than our study, and reported 3% in sublay group [15].

Gordara et al. [10] reported 22.5% of the case in the only group developed wound infection and 4% cases in the sublay group, which is higher than reported by Kohler et al. [16], which reported that 2.5% of cases in onlay group had wound infection.

Moreover, the mesh implanted in the preperitoneal space unites and consolidates the anterior abdominal wall. The mesh also adheres to the posterior rectus sheath and renders it inextensible allowing no further herniation.

In our study, we reported a lower incidence of wound infection in sublay group patients when compared with onlay group, and we had followed up all patients after discharge monthly until 1-year duration, and after that every 3 months.

There is no recurrence of hernia noticed in patients with sublay repair but the recurrence in case of the onlay repair was two patients, which are the same result reported by Hameed et al. [17], Godara et al. [11], and Kohler et al. [16], with no recurrence occurred in patients with sublay technique and minimal difference in onlay repair.Another study reported high incidence of recurrence of ∼30–50% after anatomical repair and 1.5–10% following prosthetic mesh repair [18].

The study by Saber et al. [13] reported recurrence rate of 8% in the onlay group and 3% in sublay group all over the follow-up period. The retromuscular space already exists in anatomical plane requiring no dissection, and the bare posterior surface of the rectus muscles is rich in lymphatic, which is capable of absorbing any collecting seroma [19].

The implantation of prosthetic mesh remains the most efficient method for dealing with any ventral hernia especially sublay technique as it has several advantages, and one of the most important is not transmitting the infection from subcutaneous tissues to the mesh, as it lies deep in the preperitoneal space [20].

  Conclusion Top

Sublay mesh repair is a good alternative to onlay mesh repair. This study advocates this method of ventral hernia repair, as it is applicable to all sites of ventral hernia. The mesh is mostly hidden and anchored behind the rectus sheath, the complication rate is low, and there is low recurrence rate. Finally, we suggest carrying out more trials on the sublay mesh repair technique to include bigger number of cases and longer period of follow-up.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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