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Year : 2015  |  Volume : 28  |  Issue : 1  |  Page : 11-16

Comparative study between 'onlay' and 'sublay' hernioplasty in the treatment of uncomplicated ventral hernia

1 Department of General Surgery, Faculty of Medicine, El-Menoufia University, El-Menoufia, Egypt
2 Department of General Surgery, Tala General Hospital, El-Menoufia, Egypt

Date of Submission07-Jul-2014
Date of Acceptance16-Nov-2014
Date of Web Publication29-Apr-2015

Correspondence Address:
Mostafa Mahmoud Mohamed Heikal
20 El Gomhoriya Street, Tala, El-Menoufia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1110-2098.155904

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The aim of the study was to compare between two techniques of mesh placement in uncomplicated ventral hernias, onlay (mesh on external oblique) versus sublay (mesh in the retromuscular space), to establish the standard technique for treatment of such cases.
Ventral hernias are commonly encountered in surgical practice. The estimated incidence of ventral hernia is 2-10%. Despite the high frequency of surgical repair, the optimal approach for abdominal ventral hernias is still under discussion.
Patients and methods
This prospective study included 40 consecutive adult patients with uncomplicated ventral hernia, either primary or secondary. The patients were divided into two groups. Group A (n = 20) was operated upon following the onlay mesh repair technique and group B (n = 20) was operated upon by means of the sublay mesh repair technique. All patients were evaluated as regards operative time and postoperative complications. Results were documented and statistically analyzed.
In this study, sublay use of the mesh in the treatment of ventral hernia significantly reduced the time to remove the drains (which was longer in the onlay mesh group; P = 0.001), seroma formation after drain removal (which was significantly higher in the onlay mesh group; P = 0.010), and wound infection (which was significantly higher in the onlay mesh group; P = 0.010) in comparison with onlay mesh repair.
We conclude that retromuscular (sublay) mesh repair is the ideal technique for ventral hernia repair.

Keywords: Mesh, onlay, retromuscular, sublay, ventral

How to cite this article:
Ibrahim AH, El-Gammal AS, Mohamed Heikal MM. Comparative study between 'onlay' and 'sublay' hernioplasty in the treatment of uncomplicated ventral hernia. Menoufia Med J 2015;28:11-6

How to cite this URL:
Ibrahim AH, El-Gammal AS, Mohamed Heikal MM. Comparative study between 'onlay' and 'sublay' hernioplasty in the treatment of uncomplicated ventral hernia. Menoufia Med J [serial online] 2015 [cited 2020 Feb 28];28:11-6. Available from: http://www.mmj.eg.net/text.asp?2015/28/1/11/155904

  Introduction Top

Ventral hernia of the anterior abdominal wall, either primary or secondary, is a common surgical problem and is defined as any fascial defect of the anterolateral parietal abdominal wall, through which intermittent or continuous protrusion of intra-abdominal or preperitoneal contents occurs [1].

These hernias are of various types and can be categorized into either congenital or acquired. They can also be categorized according to location into primary ventral hernias (true ventral, nonincisional hernias) and secondary ventral hernias (acquired, incisional, recurrent hernias); they occur at the site of a previous surgical scar. Both have two subtypes: lateral ventral hernia and midline ventral hernia [2].

Ventral hernia can also be categorized according to their characteristics into reducible, irreducible or incarcerated, strangulated and recurrent ventral hernia [3].

The cause of a primary ventral hernia is far from completely understood, but it is undoubtedly multifactorial. Familial predisposition plays a role with increasing evidence of connective tissue disorders [4].

They are considered as a leading cause of abdominal surgery and account for 2-10% of all abdominal wall hernias [5].

Most studies now support the theory that acute fascial separation occurs early in the postoperative period, leading to the delayed clinical development of abdominal wall incisional hernias [6],[7].

Clinical data show that 52% of incisional hernias occur within 6 months postoperatively as a result of excessive tension and inadequate healing of a previous incision. Obesity, advanced age, malnutrition, ascites, pregnancy, and conditions that increase intra-abdominal pressure are factors that predispose to the development of an incisional hernia [8].

The history of prosthetic repair in abdominal wall hernias began in 1844 with the use of silver wire coils placed on the floor of the groin to induce an inflammatory fibrosis augmenting the repair [9].

Many prosthetic materials have been tried in hernia repair, but the two most common in current use are polypropylene mesh and expanded polytetrafluoroethylene [10].

The repair of ventral hernias varies from primary closure only, primary closure with relaxing incisions, primary closure with an onlay mesh reinforcement, onlay mesh placement only, inlay mesh placement, and intraperitoneal mesh placement [11].

Primary closure techniques are usually performed for small fascial defects less than 5 cm in greatest diameter. Even for small hernia defects, recurrence rates in excess of 50% have been reported [12].

An onlay, usually of polypropylene mesh, is sutured to the anterior rectus sheath after the fascial defect has been closed primarily. This type of repair has the potential advantage of keeping the mesh separated from the abdominal contents by full abdominal muscle fascial wall thickness. The disadvantages of this repair include repair under tension, large subcutaneous dissection that allows for seroma formation, and mesh infection when the surgical wound becomes infected [12].

The sublay (retrorectus) placement of a mesh, more commonly known as the Stoppa technique, became popular in the 1990s. The recurrence rates with this repair have been stated to be less than 10% [11].

The aim of our study was to compare between two techniques of mesh placement in uncomplicated ventral hernias, onlay (mesh on external oblique) versus sublay (mesh in the retromuscular space), with respect to the operative technique and postoperative complications.

  Patients and methods Top

This is a prospective study carried out on 40 adult patients who had uncomplicated ventral hernia, either primary or secondary, and had been admitted to the Department Of Surgery at Menoufia University Hospital from October 2012 to October 2013. Informed consent was obtained from all patients included in the study, which was approved by the local ethics committee. The patients had to fulfill the following inclusion criteria: they had to have no other serious disease/illness, including hemorrhagic disorders; they had to have uncomplicated ventral hernias only; and they should have agreed to undergo surgery following either onlay mesh repair or sublay (retromuscular) mesh repair. The exclusion criteria were having inflamed, obstructed, or strangulated ventral hernias and very large ventral hernia defects that need special consideration before surgical interference, such as component separation technique, tissue expansion-assisted closure, and vacuum-assisted closure therapy.

All included patients were subjected preoperatively to the following: medical history (personal, present illness, past history, and family history); physical examination (general and local - inspection, palpation, percussion, auscultation, and per-rectal examination); preoperative investigations (complete blood count, ALT, AST, urea, creatinine, blood sugar, PT, and serum albumin); and radiological investigations such as abdominal ultrasonography to exclude any intra-abdominal copathology, ECG, and plain chest radiography in case of previous history of smoking, bronchial asthma, or clinical signs of chest troubles. Informed consent was then taken from each patient following ethical and legal research guidelines at El-Menoufia University Hospitals.

The patients were divided randomly by means of the closed envelope method into two groups according to the surgical technique used for the treatment of the uncomplicated ventral hernia: group A and group B. Group A patients (onlay mesh repair, 20 patients) were operated upon by placing the mesh superficial to the anterior rectus sheath and the external oblique muscle. Group B patients (sublay mesh repair, 20 patients) were operated upon by placing the mesh in the retromuscular space.

All operations were carried out under general anesthesia with intubation or under spinal anesthesia in both groups, with a prophylactic dose of antibiotic, cefotaxime sodium 2 g intravenous, given at induction of anesthesia.

The operative technique included the following steps: in group A (onlay mesh repair) a skin incision was made directly over the hernia defect for primary ventral hernia, but for secondary ventral hernia skin the incision was made by removing the old scar in and just equal to the size of the defect. Dissection was performed at the subcutaneous plane 4-6 cm around the defect or according to each type. The sac was dissected, the contents were reduced back into the abdomen, and the sac was excised for anatomical repair. The anterior abdominal wall aponeurosis was closed using continuous polypropylene with repeated interrupted sutures. The mesh was stretched over the whole dissected abdominal aponeurosis until 5-7 cm around the defect and was fixed to the anterior rectus sheath with a polypropylene 2/0 suture. The sutures were taken with good bites of the aponeurosis and the mesh. Multiple scattered simple sutures were used for fixation of the mesh. A suction drain was left in front of the mesh. The subcutaneous tissue was closed with vicryl 3/0. The skin was closed either with subcuticular polypropylene 3/0 or interrupted silk 3/0, and the drain was removed when the amount of drainage reached less than 30 ml/day.

Group B underwent sublay 'retromuscular' mesh repair (the Rives-Stoppa technique). The skin incision was made in the same manner as in onlay repair for ventral secondary hernias, but for primary ventral hernias we performed longitudinal or transverse incision. The hernial sac was opened during excision of the overlying skin, and any concomitant procedure, which would not entail any risk of infection, was carried out at the time of hernia repair. The redundant hernial sac was excised and the peritoneal defect was closed without tension using continuous sutures of vicryl. If there was insufficient tissue to close this layer, it was buttressed from behind with the omentum to keep autogenous tissue between the posterior surface of the mesh and the underlying bowel to prevent adherence and the risk of fistula. Once the hernial sac had been dealt with, the plane for eventual placement of the mesh was entered by palpating and exposing the medial edge of the rectus muscle, making an anterior release through the anterior rectus sheath, exposing the medial edge of the rectus muscle. The preperitoneal space was then developed by both blunt and sharp dissection laterally to the midclavicular line up to the lateral edge of the rectus muscle on one side and then on the other side for large hernial defects. The cranial and caudal extent of the dissection should extend 4-6 cm above and below the margin of the hernial defect.

The mesh was then tailored in the required dimensions and placed in the space. The force of abdominal pressure holds the prosthesis against the deep surface of the muscle, thereby achieving a sort of 'suture by apposition'. Fixation of the mesh to the overlaying muscle and fascia was carried out with 2/0 polypropylene interrupted sutures. A suction drain was placed in front of the mesh. An attempt was made to close the anterior rectus sheath over the mesh, even if it required external tension at the suture line; this was done to place another layer of autogenous tissue between the anterior surface of the mesh and the subcutaneous tissue. Complete closure may not be possible in large hernias, but the defect eventually heals well. A second suction drain was placed in the subcutaneous plane in all cases, and was removed when the drainage reached less than 30 ml/day. Intravenous antibiotics were given to all patients on the first day. Antibiotic therapy was extended only if infection was encountered according to culture and sensitivity.

The two techniques were evaluated on the basis of the following parameters: age and sex distribution, obesity (BMI), type of ventral hernia, duration of operative procedure (from incision to skin closure), amount of intraoperative blood loss (using gravimetric measurements by measuring irrigation fluid and weighing surgical sponges), duration of drainage (until it reached <30 ml/day), incidence of seroma formation after drain removal, wound infection, postoperative hospital stay, and recurrence rate.

The follow-up data were obtained during return visits at 3, 6, and 12 months after the operation, or when the patient had a complaint.

  Results Top

Out of 40 patients, 25 (62.5%) were female and 15 (37.5%) were male (P = 0.441). Their ages ranged from 22 to 64 years with a mean age of 43.5 years and median age of 45 years (P = 0.225). The female to male ratio was 1.6 : 1 [Table 1]. The different types of ventral hernias seen in this study are summarized in [Table 2]. The mean total time taken to perform surgery in the onlay group was 75-90 (83.41 ± 10.24) min compared with 80-100 (89.52 ± 7.25) min in the sublay group (P = 0.324). Suction drain was kept in all cases of onlay and sublay meshplasty.
Table 1: Demographic data of the studied cases

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Table 2: Hernia distribution in the studied cases

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The drain in group A was removed after a period of 4-9 (5.63 ± 2.14) days, whereas the drain in group B was removed after a period of 2-6 (4.51 ± 0.95) days (P = 0.001). After removal of the drain in group A, three (15%) patients developed wound seroma. In group B only one (5%) patient developed wound seroma (P = 0.010). They were treated with repeated aspiration of the seroma under complete aseptic conditions. In group A, wound infection occurred in three (15%) patients but in group B wound infection occurred only in one (5%) patient (P = 0.010); these patients were treated conservatively with broad-spectrum antibiotics. The amount of blood loss in group A ranged from 50 to 100 (74.2 ± 12.36) ml, whereas in group B it ranged from 50 to 120 (77.95 ± 15.6) ml (P = 0.639).

Mean duration of hospital stay in the onlay group ranged from 3 to 9 (4.63 ± 0.35) days, whereas it was 1-4 (2.62 ± 0.74) days in the sublay group (P = 0.063). Patients were followed up for a period of 12 months; only one (5%) patient of group A developed hernia recurrence within the first 4 months after operation because of mesh removal; there was only one (5%) case of recurrence in group B during the follow-up period of 6-12 months (P = 0.096) [Table 3].
Table 3: Operative and postoperative complications

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Statistical analyses

Statistical presentation and analysis of the present study was conducted using statistical package for the social sciences (SPSS, version 20; SPSS Inc., Chicago, Illinois, USA) on an IBM compatible computer.

Two types of statistics were determined: descriptive statistics and analytic statistics.

Descriptive statistics included percentage, mean value (X0-), and SD.

Mean value (X-) is the sum of all observations divided by the number of observations:

where å is the sum and n is the number of observations.

SD measures the degree of scatter of individual values around their mean:

Statistical analysis

Analysis of variance was performed for comparison among different times in the same group for quantitative data, using the computer program SPSS for Windows.

The c2 test was based on the hypothesis that the row and column variables are independent, without indicating strength or direction of the relationship. Pearson's c2 and likelihood ratio c2 were determined. Fisher's exact test and Yates' corrected c2 test were used for 2 × 2 tables.

The c2 test was used for comparison between two groups as regards qualitative data:

where ∑ is the summation and O is the observed value.

All these tests were used as tests of significance at P value less than 0.05.

  Discussion Top

Numerous studies have been conducted to understand the hernial mechanism and the methods of repair. All studies stressed on managing hernial defects as a part of generalized abdominal wall disorders [13]. Careful evaluation of the patient who presents with an abdominal defect reveals predisposing factors for herniation either for primary or for secondary ventral hernia, including inadequate local fascial and muscular layers due to prior tissue loss, muscle denervation or vascular insufficiency due to prior irradiation, wound infection, obesity, chronic pulmonary disease, malnutrition, sepsis, anemia, corticosteroid dependency, and/or current malignant process. All patients in this series demonstrated one or more risk factors that predispose to problems with abdominal closure [14],[15].

Repair of ventral hernia is an ongoing challenge in surgery. A wide spectrum of surgical techniques have been developed and recommended, ranging from direct suture techniques to the use of various types of prosthetic mesh. All of them aim to close the defect and strengthen the musculofascial tissues to avoid recurrence [16]. Local repair without the use of a mesh results in many recurrences. The abdominal wall is destroyed and weakened further, making future attempts at repair more difficult. Many surgical techniques have been advocated. However, there is still doubt about the ideal and best method that provides the least incidence of recurrence and high patient satisfaction [17].

The use of sheets of nonabsorbable mesh prosthesis placed across the defect and fixed to the abdominal wall has rendered most of the older types of operations obsolete. The use of a surgical mesh leads to a dramatic reduction in the incidence of recurrence, reaching 1.8% in some studies [18]. Various prosthetic materials are available; the most popular is the monofilament polypropylene mesh. A series of laboratory and clinical investigations have reported that polypropylene stimulates a strong fibroblastic response and has a dramatic resistance to infection [19].

In this study there was no statistically significant difference as regards age, sex, and type of ventral hernia between the two studied groups. The duration of surgery in patients treated with onlay mesh repair (group A) ranged from 75 to 90 min, which is longer than that reported by other studies, in which the duration of surgery ranged from 30 to 90 min. We recorded the duration of surgery in patients treated with retromuscular mesh repair (group B) as ranging from 80 to 100 min, which is slightly longer than that reported by previous studies. This was attributed to the relatively difficult dissection at the retromuscular plane.

In our study the amount of blood loss in group A ranged from 50 to 100 ml, which is slightly less than that in group B, which ranged from 50 to 120 ml, probably because of the extent of dissection. The drain was removed in patients treated with onlay mesh repair (group A) after a period of 4-9 days, which is slightly longer than that reported by previous studies, in which the period of drainage ranged from 2 to 7 days. However, in patients treated with retromuscular mesh repair (group B), the drain was removed after a period of 2-6 days, which is comparable to that reported by other previous studies, in which the period of drainage ranged from 2 to 5 days.

Seroma is one of the most common complications following the open technique and is particularly likely to occur when large skin flaps are developed during the surgical procedure. Although small seromas frequently resolve within 6-8 weeks without sequelae, a large symptomatic or persistent seroma occasionally requires multiple aspirations with subsequent increased risk for secondary infection [20].

In this study, seroma formation after drain removal was observed in three (15%) patients treated with onlay mesh repair (group A), which is similar to that reported by previous studies, in which 15% of cases developed wound seroma. In group B patients, seroma formation after drain removal occurred in only one patient, which amounted to 5% of cases. This proportion is higher than that reported by previous studies, in which seroma occurred only in 2% of patients, although the number of patients was again one. This may be attributable to the relatively small number of cases in our study.

Obesity, wide areas of dissection, and presence of devitalized tissues are conditions favoring infection, which is a real threat to successful repair. When suppuration occurs in the wound, drainage and proper antibiotics are essential [21]. Among patients treated with onlay mesh repair (group A), three (15%) patients developed wound infection, which is lower than that reported by other studies, in which wound infection occurred in 23% of cases. Among patients treated with retromuscular mesh repair (group B), one (5%) patient developed minor wound infection, which is lower than that reported by other studies, in which infection occurred in 11.6% of cases.

The length of hospital stay following treatment of ventral hernia by onlay mesh repair (group A) was 3-9 days, which is longer than that reported by other studies, which showed a mean hospital stay of 2 days. In contrast, following treatment of ventral hernia by retromuscular mesh repair (group B), the length of hospital stay was 1-4 days, which was lower than that reported by previous studies, in which the mean hospital stay was about 5.8 days.

Hernia recurrence is distressing to the patient and embarrassing to the surgeon. Tension-free repair using a prosthetic mesh has decreased recurrence to a negligible proportion [22]. In patients treated with onlay mesh repair (group A), only one (5%) patient developed hernia recurrence (after about 11 months following operation), amounting to 5% of the group, which is lower than that reported by other studies, in which the recurrence rate was about 10%. This may be attributable to the shorter period of follow-up in our study. In patients treated with retromuscular mesh repair (group B), although only one patient developed recurrence(during the period of follow up that ranged from 6 to 12 months), the proportion was 5%, which is higher than that reported by other studies, in which recurrence was 1% [19].

Previous studies have shown that 70-75% of recurrences develop within 2 years and 80-90% develop within 3 years [19]. Our follow-up, therefore, is probably not long enough and we advise longer duration of follow-up in subsequent studies.

  Conclusion Top

Sublay (retromuscular) 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 a low recurrence rate. We suggest carrying out more trials on retromuscular mesh repair, with the inclusion of a larger number of cases and a longer period of follow-up.

  Acknowledgements Top

Conflicts of interest

None declared.

  References Top

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  [Table 1], [Table 2], [Table 3]


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