Hernia mesh

INTRODUCTION — For all groin hernias and all ventral hernias with a defect >1 cm in a clean field, a mesh repair is preferred over a nonmesh repair [1,2]. Mesh is a required element of all laparoscopic or robotic groin or ventral hernia repairs and has been shown to decrease recurrences after open repair of various types of ventral hernias [3-14].

Meshes used for hernia repair vary by material, location, and operative approach, which are dictated by clinical scenarios, surgeon expertise, and available resources. While the choice of operative approaches is dependent on hernia location and discussed in the respective topics (eg, inguinal or ventral hernia), the benefit and morbidities of hernia mesh and the choice of mesh material, location, size (overlap), and fixation methods are the focus of this topic.

The management of groin hernias and the techniques of open, laparoscopic, and robotic groin hernia repairs are reviewed separately. (See "Overview of treatment for inguinal and femoral hernia in adults" and "Open surgical repair of inguinal and femoral hernia in adults" and "Laparoscopic inguinal and femoral hernia repair in adults" and "Robotic groin hernia repair".)

The management of ventral hernias and the techniques of open, laparoscopic, and robotic ventral hernia repair are discussed elsewhere. (See "Management of ventral hernias" and "Laparoscopic ventral hernia repair" and "Robotic ventral hernia repair".)

Component separation is often used to repair large (width >10 cm) or complex ventral hernias (eg, loss of domain). Its indications and techniques are discussed elsewhere. (See "Overview of component separation" and "Open anterior component separation techniques" and "Open posterior component separation techniques" and "Robotic component separation techniques".)

MESH REPAIR OF GROIN HERNIAS — For most patients undergoing elective groin hernia repair, we suggest mesh repair rather than nonmesh repair. Compared with nonmesh techniques, mesh-based open groin hernia repair techniques have a lower recurrence rate; the risk of other postoperative complications is not clearly increased with the use of mesh [15]. For patients who refuse mesh or in contaminated wounds, a nonmesh repair is reasonable. (See "Overview of treatment for inguinal and femoral hernia in adults", section on 'Noncandidates for laparoscopic repair'.)

●Randomized trials of open nonmesh repair versus open and laparoscopic mesh repair – A 2018 Cochrane review and meta-analysis included 25 randomized trials that compared open nonmesh groin hernia repair with both open and laparoscopic mesh groin hernia repair [16]. Compared with nonmesh repair, mesh repair is associated with reduced rates of hernia recurrence (2 versus 4 percent, relative risk [RR] 0.46, 95% CI 0.26-0.80; 21 studies), neurovascular and visceral injuries (4 versus 6 percent, RR 0.61, 95% CI 0.49-0.76; 24 studies), hematoma (RR 0.88, 95% CI 0.68-1.13; 15 studies), and postoperative urinary retention (RR 0.53, 95% CI 0.38-0.73; eight studies) but increased rates of wound infection (3 versus 2 percent, RR 1.29, 95% CI 0.89-1.86; 20 studies) and seroma (RR 1.63, 95% CI 1.03-2.59; 14 studies). Postoperative and chronic pain were not compared due to variations in measurement methods and follow-up time.

●Randomized trials of open nonmesh repair versus open mesh repair – A 2012 Cochrane review and meta-analysis included six randomized trials that compared open nonmesh (Shouldice) repair with open (mostly Lichtenstein) mesh repair [17]. The Shouldice repair is widely regarded as the best nonmesh repair in terms of recurrence. In that study, the recurrence rate with Shouldice techniques was higher than that with mesh techniques (3.6 versus 0.8 percent, Peto odds ratio 3.65, 95% CI 1.79-7.47), and there were no significant differences in chronic pain, complications, or postoperative stay. Firm conclusions from these results are limited by the risk of bias in the included studies.

●Large cohort studies of open nonmesh repair versus open mesh repair – Large studies from the Danish Hernia Database also confirmed that recurrence rate after 96 months following open nonmesh repair was higher than after Lichtenstein repair (8 versus 3 percent) [18,19].

The European Hernia Society guidelines recommend that all adult male patients with inguinal hernia should be operated on using a mesh technique, either with open Lichtenstein or laparoscopic inguinal hernia techniques [20]. Similarly, the Danish Surgical Society, informed by the Danish Hernia Database, states that in any male patient with a groin hernia, a mesh repair should be undertaken, with no recommendation for nonmesh Shouldice, Bassini, or McVay techniques [21]. The 2018 international guidelines for groin hernia management contained a recommendation that a mesh-based repair technique be used for both elective inguinal and femoral hernia repairs [15].

However, postherniorrhaphy groin pain or discomfort has been at least in part attributed to the use of hernia mesh. (See "Post-herniorrhaphy groin pain".)

●In a single-center series of over 6387 mesh repairs of abdominal wall hernias (65 percent inguinal), 13 percent of patients reported bothersome mesh sensation at some point greater than six months from surgery, and 2.9, 3.3, and 4.4 percent reported severe or disabling symptoms at one, two, and five years, respectively [22].

●In another study of 459 patients who underwent laparoscopic inguinal hernia repair, 16 percent reported pain, 18 percent reported mesh sensation, and 10 percent reported movement limitation after a median follow-up of 23 months [23]. Severe or disabling mesh-related symptoms were present in 2 percent for the pain category, 3 percent for the mesh sensation category, and 3 percent for the movement limitation category.

Given that the absolute reduction in hernia recurrence rate with mesh is small (2 to 4 percent in most studies) and some of the mesh complications can be debilitating, the decision of mesh versus nonmesh open groin hernia repair may be made through shared decision making. The same 2018 international guidelines also suggested that a nonmesh repair can be used in cases where the patient refuses a mesh and/or after shared decision making [15].

MESH REPAIR OF VENTRAL HERNIAS — For most patients undergoing elective ventral hernia repair (>1 cm), we suggest mesh repair rather than nonmesh repair. The available evidence suggests that mesh reinforcement decreases the risk of hernia recurrence but may incur some mesh-related complications. For patients who do not accept mesh for fear of mesh-related complications or in contaminated wounds, a nonmesh (suture) open hernia repair can be performed after shared decision making to ensure that patients clearly understand that the expected recurrence rate is higher. (See "Management of ventral hernias".)

●Ventral incisional hernias – In a registry-based cohort study in Denmark, over 3000 patients underwent elective ventral incisional hernia repair and were followed for five years [24]. Of these patients, 1119 underwent open mesh repair, 366 had open nonmesh repair, and 1757 had laparoscopic mesh repair. Compared with nonmesh repair, mesh repair was associated with fewer reoperations for recurrences (open mesh 12.3 percent, laparoscopic mesh 10.6 percent, nonmesh 17.1 percent) but more reoperations for mesh-related complications (open mesh 6.1 percent, laparoscopic mesh 4.2 percent, nonmesh 0.8 percent). Given that 57 percent of nonmesh repairs in this study were performed for very small hernias (<2 cm), there was a selection bias against mesh repair, which likely underestimated its benefit in reducing recurrences while exaggerating its harm in causing complications [25]. Despite that, the study was still able to affirm that mesh reduced recurrence in incisional hernia repairs. The mesh-related complications reported by this study echo our caution of only using mesh for ventral hernias >1 cm. (See "Management of ventral hernias", section on 'Surgical management of ventral hernias'.)

●Primary ventral hernias – In a systematic review and meta-analysis of nine studies of primary ventral hernia repairs (n = 1782), the recurrence rates were 8.2 percent after suture repair and 2.7 percent after mesh repair, but the seroma (7.7 versus 3.8 percent) and surgical site infection rates (7.3 versus 6.6 percent) were also higher after mesh repair [4].

In a 2019 systematic review and meta-analysis of five trials [8], open mesh repair of small- or medium-sized umbilical hernias (1 to 4 cm in diameter) reduced the risk of recurrence (1.2 versus 2.5 percent, relative risk 0.28, 95% CI 0.13-0.58) without increasing the risk of infection, seroma, or hematoma formation, compared with sutured repair [26].

●All ventral hernias – A 2017 meta-analysis of 25 randomized controlled trials in ventral hernia repair concluded that mesh reinforcement in clean cases can decrease hernia recurrence (8.7 versus 21.3 percent, odds ratio [OR] 0.35, 95% CI 0.26-0.48) but increase risk of surgical site infection (8.6 versus 5.1 percent, OR 1.73, 95% CI 1.00-3.00) [27].

The 2019 guidelines from the European Hernia Society and American Hernia Society recommend that mesh be used for the repair of umbilical and epigastric hernias to reduce the recurrence rate [28]. Sutured repair can be considered in shared decision making and for small hernia defects of <1 cm. A 2017 expert consensus based on systematic reviews recommended mesh reinforcement in the elective repair of ventral incisional hernias and primary ventral hernias >2 cm in width when there is no contamination [29].

Mesh-associated morbidities — Despite the benefit of fewer recurrences, mesh repairs of ventral hernias are associated with a higher rate of wound complications, including infections, compared with nonmesh repairs [9,30-33]. However, it is often possible to treat the superficial wound infection with antibiotic therapy and avoid mesh removal, especially when mesh is placed in a sublay or underlay (intraperitoneal) position. (See "Wound infection following repair of abdominal wall hernia", section on 'Treatment'.)

●Mesh removal – Between 1.4 and 6.9 percent of meshes had to be removed because of infection [34-36]. Risk factors associated with mesh explantation include enterotomy or another abdominal procedure concomitant with the hernia repair, surgical site infection, and onlay position of mesh placement [34]. In a large administrative database study of over 600,000 patients who underwent at least one ventral hernia repair, 0.07 percent had mesh removed after a median of 346 days after initial surgery [37]. The median cumulative cost for patients who required mesh explantation was substantially higher than for those who did not require mesh removal (USD $21,889 versus USD $6983). (See "Wound infection following repair of abdominal wall hernia".)

●Bowel obstruction or fistulization – Additionally, synthetic mesh also provokes an inflammatory response so that intraperitoneal mesh has the potential for complications such as abdominal adhesion formation and late mesh erosion [3,30,32,33,38,39]. A systematic review reported an adhesive bowel obstruction rate of 1.1 to 3.7 percent and an enterocutaneous fistula rate of 0 to 4.8 percent after ventral hernia repair with intraperitoneal mesh placement [40].

●Difficulty with future abdominal surgery – It is also more difficult to reoperate through a mesh-reinforced abdominal wall. In a retrospective population study of patients undergoing abdominal surgery, over 3500 patients with prior incisional hernia repair with mesh were compared with similar numbers of propensity score-matched control patients [41]. Prior incisional hernia with mesh was associated with increased overall complications (41 versus 35 percent), surgical complications (34 versus 27.5 percent), wound complications (6.1 versus 3.7 percent), length of hospital stay (five versus four days), reoperations (3.7 versus 1.8 percent), and one-year unplanned readmissions (30 versus 25 percent).

For mesh hernia repairs, certain technical modifications may alleviate some of the mesh-related complications based on limited evidence or expert opinion.

●Lightweight mesh – For open and laparoscopic groin hernia repair, there is some evidence that associates lightweight meshes with less acute and chronic pain and foreign body sensation than heavyweight meshes [42,43], but not all studies agree [44,45]. For ventral hernia repair, however, lightweight meshes generally should not be used because of a higher recurrence rate. (See 'Mesh categories' below.)

●Flat mesh – A flat mesh configuration is preferred whenever possible. There is some evidence that a flat mesh is better tolerated than a preconfigured mesh. (See 'Mesh configuration' below.)

●Sublay mesh – Some mesh-related complications, especially major ones such as adhesions causing intestinal obstruction or erosion/fistulization, are attributable to the intra-abdominal position of the meshes despite the antiadhesive coating or layer. Thus, it is intuitive that if meshes can be placed in the sublay position, such complications may be avoided with the peritoneum positioned between the mesh and the viscera. It then stands to reason that repairs that place mesh in the sublay position (eg, open or robotic Stoppa repair or laparoscopic or robotic extended totally extraperitoneal repair) may have better results than intra-abdominal onlay mesh repairs with regard to complications.

However, a systematic review and meta-analysis of 11 nonrandomized studies (2320 patients) of minimally invasive ventral hernia repairs reported no statistically significant difference among patients who received intraperitoneal versus extraperitoneal mesh for outcomes of surgical site infection, seroma, hematoma, readmission, and recurrence [46]. Furthermore, the aforementioned cohort study from Denmark with five-year follow-up also found that laparoscopic repairs had fewer reoperations for mesh complications compared with open counterparts (3.7 versus 5.6 percent). Additionally, for open repairs with mesh complications, mesh position was not independently predictive of those events [24]. Finally, there is considerable morbidity in accessing the sublay space, which can predispose to neurovascular injuries of the abdominal wall. (See 'Mesh location' below.)

MESH MATERIAL — Commercially available hernia meshes generally fall into one of three categories: synthetic, biologic, and biosynthetic. When available, the choice of a mesh from a particular category is primarily determined by hernia location and the surgical wound classification (table 1).

Mesh categories — The three general categories of mesh used in the repair of ventral hernias are (see "Reconstructive materials used in surgery: Classification and host response"):

●Synthetic – Synthetic meshes are either woven from an extruded monofilament (eg, polypropylene or polyester) or created from expanded polytetrafluoroethylene and can be subcategorized by weight/density (ultra-lightweight to super-heavyweight) as well as by material; composition; pore characteristics; and mechanical parameters, including tensile and burst strength, elasticity, and stiffness [29,47]. (See "Reconstructive materials used in surgery: Classification and host response", section on 'Synthetic materials'.)

For elective ventral hernia repair, lightweight meshes generally should not be used; although a lightweight mesh can be associated with less postoperative pain than medium-weight mesh [48], it is also associated with a higher rate of hernia recurrence [9,27]. Some studies favor medium-weight mesh to light- or ultra-heavyweight meshes [49], although a patient-blinded randomized trial found similar clinical outcomes between medium-weight and heavyweight polypropylene mesh in open retromuscular ventral hernia repair, with no difference in mesh sensation at one year [50].

●Biologic – A variety of biologic meshes derived from human or animal tissues (eg, porcine, bovine, equine) are also available for abdominal wall reconstruction [51]. Biologic tissue is rendered nonimmunogenic by a washing process that is designed to remove cellular debris without damaging the connective tissue scaffold, which functions as an acellular biologic matrix into which the recipient's native tissue grows, eventually replacing it [51]. (See "Reconstructive materials used in surgery: Classification and host response", section on 'Allograft processing' and "Reconstructive materials used in surgery: Classification and host response", section on 'Xenograft processing'.)

We suggest using biologic mesh only as a reinforcing layer, rather than as a fascial replacement [52,53]. Because biologic mesh gradually resorbs over time, bridged repairs with biologic or bioabsorbable mesh are associated with high rates of recurrence [54-57]. As an example, in the Laparoscopic and Open Ventral Hernia Repair (LAPSIS) trial, 253 patients with an abdominal wall hernia of 4 to 10 cm underwent repair with synthetic or biologic (Surgisis) mesh [58]. Compared with synthetic mesh, biologic mesh resulted in more major complications after both open (23 versus 10 percent) and laparoscopic repair (27 versus 11 percent). This trial was terminated prematurely due to a very high rate of hernia recurrence after biologic mesh repair, especially laparoscopically (23 versus 3 percent synthetic mesh).

●Biosynthetic – Long-acting resorbable meshes are synthetically derived products with resorption profiles between 6 and 36 months. This time frame theoretically allows for native collagen deposition to account for wound strength and durability without the concern of chronic mesh infection often affiliated with permanent synthetic alternatives. Clinical data exist for three long-acting resorbable synthetics: TigrMatrix (TM), Gore Bio-A, and Phasix [59].

•TM is made of several polymers that begin degrading at 14 days but are not fully resorbed until 36 months [60]. Clinical data for TM are limited to only two small series published. One reports its use in 40 open inguinal hernia repairs with a 20 percent three-year recurrence rate, 16 percent incidence of chronic pain, and 10 percent incidence of mesh sensation [61]. The other series included 16 patients at high risk for fascial dehiscence with TM placed as an onlay. No fascial dehiscences occurred [62]. Given the paucity of clinical data available, the performance of TM in the context of ventral hernia repair is unknown.

•Gore Bio-A is a copolymer of poly(glycolide-trimethylene carbonate) that is fully resorbed by six months. Prospective clinical data exist from the Complex Open Bioabsorbable Reconstruction of the Abdominal Wall (COBRA) study, which included 104 ventral hernia repairs >9 cm² in a contaminated setting (Centers for Disease Control [CDC] surgical wound class II to IV (table 1)) [63]. While two-thirds of patients required a component separation, all patients achieved fascial closure with mesh in the retromuscular (90 percent) or intraperitoneal (10 percent) position. With 84 percent follow-up at two years, 17 percent of patients had a recurrence. While there was no comparator arm, these data suggest that use of Bio-A in a contaminated setting is safe with reasonable outcomes. Bio-A is unique in that the COBRA trial included the use of Bio-A in cases where infected mesh was removed and could be classified as CDC wound class IV.

•Phasix is a naturally derived monofilament poly-4-hydroxybutyrate polymer produced by Escherichia coli K12 bacteria through transgenic fermentation techniques and is fully resorbed at 12 to 18 months [64]. One study prospectively studied 120 ventral hernia repairs >10 cm² in patients with "high-risk" medical comorbidities. At 18 months, 79 percent of patients had a 9 percent recurrence rate [65]. At three years, 68 percent of patients in the initial trial had an 18 percent recurrence rate [66]. While these outcomes demonstrate the safety of Phasix with acceptable outcomes, they were achieved in clean cases (CDC class I) and must ultimately be compared with permanent synthetic meshes more commonly used in this setting.

Wound classifications — Often, the choice of a hernia mesh class is affiliated with the surgical wound classification (table 1).

Clean wound — For both groin and ventral hernia repairs in clean wounds (CDC surgical wound class I), we recommend using a synthetic mesh rather than another type of mesh. In clean wounds, synthetic mesh is associated with fewer hernia recurrences but no more complications than nonsynthetic meshes, even in patients with "high-risk" medical comorbidities [58,67].

●In the clean subgroup analysis of the Preventing Recurrence in Clean and Contaminated Hernias (PRICE) trial, the polypropylene mesh group had a lower rate of hernia recurrence at two years versus the porcine biologic mesh group (28 versus 34 percent; p for interaction = 0.041), while the two groups had similar postoperative complication rates [67].

●In the LAPSIS trial (elective ventral hernia repair with synthetic or biologic mesh in clean wounds), the use of biologic mesh resulted in significantly more recurrences (18 versus 5.6 percent), reoperations (17 versus 7.2 percent), and similar numbers of mesh infections (1.5 versus 1.5 percent) compared with synthetic mesh [58].

Contaminated wound — For ventral hernia repairs in clean-contaminated or contaminated wounds (CDC surgical wound class II/III), biologic meshes are traditionally used [68]. However, several trials have reported equivalent or better outcomes utilizing synthetic mesh in clean-contaminated or contaminated fields compared with biologic meshes [54,63,69,70].

●As an example, in the contaminated subgroup analysis of the PRICE trial, the polypropylene mesh group had a lower rate of hernia recurrence at two years versus the porcine biologic mesh group (5.9 versus 50 percent; p for interaction = 0.041), while the two groups had similar postoperative complication rates [67].

●Similarly, in another randomized clinical trial that followed 253 patients for two years after an open retromuscular ventral hernia repair in a clean-contaminated or contaminated field, the synthetic mesh group had a lower rate of hernia recurrences than the biologic mesh group (5.6 versus 20.5 percent), while the two groups had similar rates of surgical site occurrences requiring another procedure (including infectious complications) and similar quality-of-life outcomes [71].

As a class, biosynthetic mesh has not been compared against synthetic mesh in any randomized trials. However, retrospective comparative studies between the two have been reported.

●To address the heterogeneous cohorts in the studies of biosynthetic meshes and account for the absence of a control arm in either prospective trial for Bio-A and Phasix, an Abdominal Core Health Quality Collaborative (ACHQC) analysis was done to compare propensity-matched groups of long-acting resorbable and polypropylene mesh ventral hernia repairs in CDC class II/III wounds. Interestingly, biosynthetic mesh repairs had higher rates of surgical site infections (22 versus 11 percent, p = 0.03), surgical site occurrences requiring a procedural intervention (24 versus 13 percent, p = 0.049), and reoperation rates (14 versus 4 percent, p = 0.009) than polypropylene mesh repair [72].

●In another ACHQC study, 2484 patients who underwent elective ventral hernia repair in class II (64 percent) and III wounds (36 percent) were compared with propensity score matching [73]. At one year, there was no significant difference in surgical site occurrence (permanent mesh 16 percent, biosynthetic mesh 15 percent, biologic mesh 21 percent; p = 0.13), surgical site infection (12, 14, 12 percent; p = 0.64), and surgical site occurrence requiring procedural intervention at 30 days (12, 15, 17 percent; p = 0.1), but the recurrence rate was significantly lower in the permanent mesh group (23, 40, 32 percent; p = 0.029). Approximately 80 to 90 percent of the meshes were placed in a sublay position.

These results seem to support the use of synthetic mesh over biologic or biosynthetic mesh in CDC II/III cases [58,69], especially given the lower cost associated with synthetic meshes [74]. Nevertheless, high-level evidence to guide decision making is limited, and the use of a biologic or biosynthetic mesh in CDC II/III wounds is still viewed as reasonable by most surgeons [75].

Additionally, surgeons should be aware of the specific context in which these results were achieved: open, nonemergency cases, with retromuscular mesh placement and fascial closure, done by surgeons who perform retromuscular repairs at a high volume. Often, if surgeons are not comfortable with a retromuscular repair, the question should not be what kind of mesh to use but whether a concomitant repair should be done at all. In many contaminated scenarios (eg, bowel resection, stoma reversal, cholecystectomy), the hernia should be primarily repaired, to be followed by a staged mesh repair in a clean setting.

For groin hernias in clean-contaminated wounds (eg, in the presence of bowel strangulation and/or a concomitant bowel resection), a synthetic, monofilament, large-pore mesh can be used to repair the hernia. However, in contaminated wounds (eg, in the presence of bowel perforation and/or abscess formation), no mesh should be used to repair the hernia. Once source control has been achieved, the groin hernia can either be repaired without mesh or left unrepaired, depending on the clinical condition of the patient. This is not based on data but expert opinion and common sense. (See "Overview of treatment for inguinal and femoral hernia in adults", section on 'Complicated hernia'.)

Dirty wound — For ventral hernias in dirty infected wounds (CDC surgical wound class IV), primary closure or planned "staged" repair is safe and often the wise decision [76]. Alternatively, a biosynthetic or biologic mesh can be used. While no mesh has an indication in a contaminated setting, Bio-A (biosynthetic) has prospective data available demonstrating its safety in CDC class IV wounds (including concomitant excision of infected mesh) at the time of ventral hernia repair. (See 'Mesh categories' above.)

For groin hernias in a dirty infected wound, no mesh should be used. Once source control has been achieved, the hernia can either be repaired without mesh or left unrepaired, depending on the clinical condition of the patient. (See "Overview of treatment for inguinal and femoral hernia in adults", section on 'Complicated hernia'.)

MESH LOCATION — For ventral hernia repair, the mesh can be placed above the fascia (onlay), between the rectus muscles and peritoneum/posterior rectus sheath (sublay), below the peritoneum (underlay or intraperitoneal onlay), or in between fascial edges (inlay) (figure 1) [77].

●Onlay – Onlay mesh repair of ventral hernias is performed with an open approach, in which the hernia sac is dissected and either inverted or resected. The fascial edges are approximated with sutures in a fashion similar to that of a simple suture repair. Thereafter, a piece of mesh is placed anterior to the fascia overlying the repair and affixed to the anterior abdominal wall fascia using sutures, tacks, or adhesives.

Although onlay mesh placement was historically associated with a high wound complication rate, it is technically easier to perform than the other techniques and is possible to perform without entering the peritoneum. The onlay technique pioneered by Chevrel [78] is again gaining popularity, especially in European countries [79,80]. In a contemporary case-matched study in low-risk patients, patients who underwent ventral hernia repair with onlay mesh affixed with bioadhesive did not have more wound complications than matched patients who had sublay mesh placed [81].

●Sublay (retrorectus) – Sublay mesh repair of ventral hernias can be performed with an open or robotic approach. The open technique, first described by Rives and Stoppa and bearing their names, involves first isolating and excising the hernia sac. The plane between the posterior rectus sheath and rectus muscle is developed and carried to the lateralmost extent of the rectus muscle to completely mobilize the posterior sheath, which is then sutured to the opposing sheath, and a large sheet of mesh is placed anterior to the posterior rectus sheath and posterior to the rectus muscle. Sutures are passed through the lateral abdominal wall and tied above the anterior fascia with the knots buried in the subcutaneous tissue. Depending upon the amount of tension encountered, the anterior rectus sheaths can be reapproximated and sutured together in the midline or sutured to the mesh (see "Open posterior component separation techniques", section on 'Rives-Stoppa retrorectus dissection'). The robotic technique, which is often combined with a transverse abdominis release, is described elsewhere. (See "Robotic component separation techniques", section on 'Robotic Rives-Stoppa retrorectus dissection'.)

●Underlay (IPOM) – The underlay method, also referred to as the intraperitoneal onlay mesh (IPOM) method, places the mesh in an underlay or intraperitoneal location and can be performed with any surgical approach. If an underlay mesh is placed via the open approach, most surgeons either suture the mesh to the posterior sheath/peritoneum or use a suture passer to place transfascial sutures. The anterior fascial sheath is then closed over the mesh. Laparoscopic ventral hernia repair typically involves placement of a mesh in an underlay position (see "Laparoscopic ventral hernia repair"). Robotic ventral hernia repair can place a mesh in an underlay or sublay position depending on technique. (See "Robotic ventral hernia repair", section on 'Intraperitoneal onlay mesh'.)

●Inlay – The inlay technique, which bridges the fascial defect with mesh, is used only when the fascial defect is too large to primarily close with any other techniques.

For open ventral hernia repair, where one has a choice of onlay, sublay, or underlay techniques, we prefer sublay placement of the mesh. This is consistent with expert consensus opinion [29].

●Based on a network meta-analysis of 21 studies, sublay placement of mesh was associated with the lowest risk for recurrence (odds ratio [OR] 0.218, 95% CI 0.06-0.47) and was the best of the four treatment modalities (onlay, inlay, sublay, underlay) assessed (Prob [best] = 94.2 percent). Sublay was also associated with the lowest risk for surgical site infection (SSI; OR 0.449, 95% CI 0.12-1.16) and was the best of the four treatment modalities assessed (Prob [best] = 77.3 percent) [82]. In a multicenter, risk-adjusted observational study of 447 open ventral hernia repairs from the Ventral Hernia Outcomes Collaborative (VHOC), sublay repair was associated with fewer recurrences than underlay repair (hazard ratio 0.4, 95% CI 0.2-0.8) and no difference in SSI [83].

●A propensity score-matched study of over 9000 open incisional hernia repairs from the Herniamed registry reported greater incidence of pain on exertion (17.1 versus 13.7 percent; p = 0.007), pain at rest (10.4 versus 8.3 percent; p = 0.040), and chronic pain requiring treatment (8.8 versus 5.8 percent; p<0.001) after open IPOM repairs than after open sublay mesh repairs [84].

For laparoscopic ventral hernia repairs, it is standard to place the mesh in an underlay (IPOM) position. For robotic repair, the mesh is placed in either sublay or underlay position depending on the technique used.

For groin hernia repair, the mesh location is dictated by the surgical approach. Open techniques such as Lichtenstein repair use onlay mesh, while laparoscopic and robotic repairs use preperitoneal mesh. (See "Overview of treatment for inguinal and femoral hernia in adults", section on 'Surgical repair'.)

MESH SIZE/OVERLAP — The mesh used for ventral hernia repair should be sufficiently large to permit >2 cm overlap for open repair of small primary ventral hernias (<1 cm in diameter), >3 cm overlap for open repair of medium primary ventral hernias (1 to 4 cm in diameter), >5 cm overlap for open repair of large primary ventral hernias (>4 cm in diameter) or ventral incisional hernias [28], and >5 cm overlap for all laparoscopic repairs [85]. For laparoscopic repair, other guidelines suggest that the radius of the mesh should be four times the radius of the fascial defect being addressed [2,86].

Meshes used to repair groin hernia are generally precut commercially to fit the inguinal anatomy. If a precut mesh is not available, meshes should be cut to 15 cm x 9 cm for open repair [87] and 15 cm x 10 cm for laparoscopic or robotic repair. (See "Laparoscopic inguinal and femoral hernia repair in adults", section on 'Mesh placement and fixation'.)

MESH CONFIGURATION — Hernia meshes are commercially available as either flat sheets or "patches" designed to ease placement or fixation. In a randomized trial of 352 patients with a primary small umbilical or epigastric hernia, repair with a flat polypropylene mesh in the preperitoneal location resulted in fewer complications (22 versus 33 percent) and reoperations (4 versus 11 percent) than repair with a Proceed ventral patch [88]. There was no difference in hernia recurrences. However, this trial has been criticized for a high loss to follow-up and possible issues with the Proceed patch.

Mesh plugs have higher risks of extensive fibrosis and are more likely to stimulate an intense inflammatory reaction when compared with flat meshes [89,90]. The lifetime risk for mesh erosion is higher with plugs than with flat mesh; the risk of mesh movement is reduced by the use of large, flat mesh in a tension-free setting. However, there is no detectable difference in the clinical outcomes of the plug and patch versus Lichtenstein or Prolene hernia system repair of inguinal hernias, according to several meta-analyses of randomized trials [91-93]. It is possible that mesh-related complications are not captured or occurred rarely in the source trials.

MESH FIXATION — To avoid migration or shrinkage, mesh can be fixated using sutures, tacks, or tissue glue, or it can be self-gripping. The decision to fix mesh and the fixation method are typically determined by surgeon preference but can be influenced by the hernia location and surgical approaches as well.

Groin hernia repair — In open groin hernia repair, meshes can be fixed with sutures, tacks, or tissue glue, or the mesh could be self-fixing. Surgeons should choose a mesh fixation method based on their experience. All fixation methods have been associated with similar wound infectious complications and hernia recurrence rates. Although tissue glue (fibrin sealant or cyanoacrylate) has been associated with less early postoperative and chronic pain than sutures in some studies, the available data are far from conclusive [15]. (See "Open surgical repair of inguinal and femoral hernia in adults", section on 'Mesh fixation'.)

In laparoscopic and robotic groin hernia repair, although some support nonfixation of mesh, most surgeons continue to fix the mesh into place using staples, tacks, sutures, or fibrin glue, each of which appears to have similar outcomes with regard to the risk of recurrent hernia. Tacks or staples should not be placed below the iliopubic tract lateral to the spermatic cord and the epigastric vessels to minimize the chance of damaging nerves and vascular structures [94]. (See "Laparoscopic inguinal and femoral hernia repair in adults", section on 'Mesh placement and fixation' and "Robotic groin hernia repair", section on 'Mesh fixation'.)

Ventral hernia repair — In open ventral hernia repair, mesh fixation depends on mesh location. Underlay (ie, intra-abdominal onlay mesh) and sublay meshes are typically fixated to the anterior abdominal using transfascial sutures. Onlay meshes, which are used infrequently, are fixated to the anterior fascia using sutures or tissue glue. If anterior component separation has been performed, the onlay mesh can also be fixated to the cut edge of the external oblique muscle with a running suture. (See "Open anterior component separation techniques", section on 'Mesh placement and closure'.)

In laparoscopic ventral hernia repair, meshes can be fixated to the anterior abdominal wall with transfascial sutures, tacks, or a combination of the two. If no transfascial sutures are placed, two rows of permanent tacks should be used to fixate the mesh; if transfascial sutures are used, one or two rows of either absorbable or permanent tacks may be placed at the surgeon's discretion. (See "Laparoscopic ventral hernia repair", section on 'Mesh fixation'.)

In robotic ventral hernia repair, mesh fixation depends on technique. If an underlay mesh is used (ie, intraperitoneal onlay mesh), it is fixated with either transfascial sutures or tacks, similar to the laparoscopic technique. If a sublay mesh is used (eg, in a Stoppa repair with or without transverse abdominis release or an extended totally extraperitoneal repair), a large piece of mesh is typically placed in the retrorectus/preperitoneal space with either no fixation or only a few holding sutures. (See "Robotic ventral hernia repair", section on 'Surgical techniques' and "Robotic component separation techniques", section on 'Robotic TAR'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Ventral hernia".)

SUMMARY AND RECOMMENDATIONS

●The role of mesh in hernia repairs – Mesh is a required element of all laparoscopic or robotic groin or ventral hernia repairs and is only optional in open groin or ventral hernia repairs for defects larger than 1 cm. (See 'Introduction' above.)

●Mesh repair of groin hernias – For most patients undergoing elective groin hernia repair, we suggest mesh repair rather than nonmesh repair (Grade 2C). Compared with nonmesh techniques, mesh-based open groin hernia repair techniques have a lower recurrence rate; the risk of other postoperative complications is not clearly increased with the use of mesh. For patients who refuse mesh or in contaminated wounds, a nonmesh repair is reasonable. (See 'Mesh repair of groin hernias' above.)

●Mesh repair of ventral hernias – For most patients undergoing elective ventral hernia repair (>1 cm), we suggest mesh repair rather than nonmesh repair (Grade 2C). The available evidence suggests that mesh reinforcement decreases the risk of hernia recurrence but may incur some mesh-related complications. For patients who do not accept mesh for fear of mesh-related complications or in contaminated wounds, a nonmesh (suture) open hernia repair can be performed after shared decision making to ensure that patients clearly understand that the expected recurrence rate is higher. (See 'Mesh repair of ventral hernias' above.)

●Mesh material – Commercially available hernia meshes generally fall into one of three categories: synthetic, biologic, and biosynthetic. When available, the choice of a mesh from a particular category is primarily determined by hernia location and the surgical wound classification (table 1). (See 'Mesh material' above.)

•Clean wound – For both groin and ventral hernia repairs in a clean wound (Centers for Disease Control [CDC] surgical wound class I), we suggest using a synthetic mesh rather than another type of mesh (Grade 1B).

•Clean-contaminated or contaminated wound – For ventral hernia repairs in a clean-contaminated or contaminated wound (CDC surgical wound class II/III), synthetic, biologic, and biosynthetic mesh have all demonstrated acceptable outcomes. Surgeons concerned about chronic mesh infection can use biologic or biosynthetic mesh.

For groin hernias in a clean-contaminated wound (CDC surgical wound class II; eg, in the presence of bowel strangulation and/or a concomitant bowel resection), a synthetic, monofilament, large-pore mesh can be used to repair the hernia. However, in a contaminated wound (CDC surgical wound class III; eg, in the presence of bowel perforation and/or abscess formation), no mesh should be used to repair the hernia.

•Dirty infected wound – Ventral hernia repair in a dirty infected wound (CDC surgical wound class IV) is not standardized. Most often, these cases are staged first with a primary repair followed by a subsequent mesh repair in a lower wound class. Alternatively, a biosynthetic or biologic mesh can be used. 

Groin hernias are either repaired without mesh or left unrepaired in a dirty infected wound.

●Mesh location – For open ventral hernia repair, we suggest sublay mesh placement rather than another mesh location (Grade 2C). Sublay meshes are associated with the lowest risk of hernia recurrence and surgical site infection among onlay, inlay, sublay, and underlay repairs. (See 'Mesh location' above.)

For laparoscopic ventral hernia repair, it is standard to place the mesh as an underlay mesh. Robotic repair places mesh at either the sublay or intraperitoneal location, depending on technique.

For groin hernia repair, mesh location is dictated by surgical approach. Open techniques use onlay mesh, while laparoscopic and robotic repairs use preperitoneal mesh. (See "Overview of treatment for inguinal and femoral hernia in adults", section on 'Surgical repair'.)

●Mesh size/overlap – The mesh used for ventral hernia repair should be sufficiently large to permit >2 cm overlap for open repair of small primary ventral hernias (<1 cm in diameter), >3 cm overlap for open repair of medium primary ventral hernias (1 to 4 cm in diameter), >5 cm overlap for open repair of large primary ventral hernias (>4 cm in diameter) or ventral incisional hernias, and >5 cm overlap for all laparoscopic repairs. (See 'Mesh size/overlap' above.)

Most meshes used to repair groin hernia are precut commercially to fit the inguinal anatomy. If a precut mesh is not available, meshes should be cut to 15 cm x 9 cm for open repair and 15 cm x 10 cm for laparoscopic or robotic repair.

●Mesh configuration – For most patients, we suggest a flat mesh rather than a preconfigured mesh (eg, mesh plug) (Grade 2C). In theory, the latter may be associated with greater risk of mesh-related complications such as migration and erosion. (See 'Mesh configuration' above.)

●Mesh fixation – To avoid migration or shrinkage, hernia meshes can be fixated using sutures, tacks, or tissue glue, or they can be self-gripping. The decision to fix mesh and the fixation method is typically determined by surgeon preference but can be influenced by hernia location and surgical approaches as well. (See 'Mesh fixation' above.)