Guidelines for laparoscopic treatment of ventral and incisional abdominal wall hernias (International Endohernia Society [IEHS])—Part III

Search terms: ‘‘Incisional Hernia,’’ ‘‘Ventral Hernia,’’ ‘‘Laparoscopic Incisional Hernia Repair,’’ ‘‘Laparoscopic Ventral Hernia Repair,’’ ‘‘Hernia Repair and Meshes,’’ ‘‘Meshes,’’ ‘‘Mesh Repair,’’ ‘‘Laparoscopic Ventral Hernia Repair and Meshes,’’ ‘‘Incisional Hernia Repair and Meshes.’’ A systematic search of the available literature was performed in July 2012 of Medline, PubMed, Cochrane Library, and relevant journals and reference lists using the above-listed search terms. The first search detected 78 relevant articles. In a second-level search, two articles were added. Twenty-six articles were thus used for this review.

fewer than 1,000 patients per group. Thus, postmarket surveillance of devices is always supplemented by documentation in clinical registries. These will not be able to confirm any superiority, but they at least will help identify devices with poor performance.
Adhesions after laparoscopic ventral hernia repair (LVHR) is a common phenomenon, the result of the trauma of surgery and a reaction to the mesh and/or fixation devices. No technique or device completely prevents the formation of adhesions.
Direct contact of visceral organs with polypropylene (PP) and polyester is followed by dense adhesions to the mesh, leading to significant risk of bowel injury requiring resection during revision operations and suspected to be followed by a higher risk for development of an intestinal fistula. This risk is decreased with use of films (expanded polytetrafluoroethylene [ePTFE]) or textile meshes made of polyvinyl difluoride (PVDF), PP, or polyester, but with an additional coating/barrier function of another material, such as titanium, collagen, cellulose, hyaluronic acid, or polydioxanon.
Any film barrier covering a textile will initiate a tissue response comparable to that of the pure filmlike device with encapsulation of the entire prosthesis. Because any damage to peritoneum heals within days, a temporary protection of the polymer surface should be sufficient. However, whether this provides a sufficient protection depends to the textile material, and some require a permanent barrier. Level 4 Laparoscopic ventral and incisional hernia repair can be performed with the use of ePTFE, PVDF, or composite meshes and is appropriate for use within the abdominal cavity There is no ideal mesh, but every mesh has to be considered as a compromise with regard to strength, elasticity, tissue ingrowth, and cellular response, with its specific advantages and disadvantages

Statements
Most devices demonstrate a lack of stretchability, so that folding or wrinkling of the fixed mesh after release of the pneumoperitoneum may be unavoidable When meshes are inserted intraperitoneally during laparoscopic intraperitoneal onlay meshes (IPOM), they must meet stringent requirements because they directly contact the intestines. Eriksen et al. [1] formulated the following characteristics for an optimal mesh to be used for laparoscopic repair of ventral and incisional hernias: • Minimal adhesion formation.
• No infection or fistula formation.
• No change in abdominal wall compliance.
• Easy to manipulate.
Typically, meshes are made of the basic materials PP, polyester, polyvinylidenfluoride, or PTFE. The use of pure PP meshes and polyester meshes are not recommended for laparoscopic IPOM [1][2][3]. It is accepted that PP and polyester meshes are coated either with a protective membrane or a protective film (absorbable or nonabsorbable) or with a titanium layer to protect the viscera. These composite meshes, as they are known, and ePTFE meshes are generally recommended for intraperitoneal use [1,2,4,5] (Table 1). It is assumed that the use of these meshes reduced few adhesion formation and hence lowered the risk of intestinal damage and fistula formation.
Clinical studies To date, there has been a paucity of clinical case series and only one randomized trial providing general recommendations for specific meshes. Only a few clinically important differences that could be deemed to be clinically relevant outcome parameters have been discerned in comparative studies between the meshes.
In a prospective randomized trial, Moreno-Egea et al. [6] compared in laparoscopic incisional hernia repair the use of a lightweight titanium-coated mesh (n = 51) with a collagen-polyester composite mesh (n = 51). The primary end points were pain and recurrence. The secondary end Modified after Eriksen et al. [1] points were morbidity and patient outcomes (analgesic consumption, return to everyday activities). The postoperative complication rates were similar for the two meshes. Pain was significantly less common in the titanium-coated mesh group at 1 month (p = 0.029). There was a significant difference between the two groups in the average use of analgesics in favor of the titanium-coated mesh group (p \ 0.001). The titanium-coated mesh group returned to everyday activities after 6.9 days versus 9.7 days for the collagen-polyester composite mesh group (p \ 0.001).
The rate of recurrence did not differ between the two groups at the 2-year follow-up evaluation. The authors concluded that the light titanium-covered PP mesh was associated with less postoperative pain in the short term, lower analgesic consumption, and a quicker return to everyday activities than the Parietex composite mediumweight mesh. In a retrospective comparative study, Colon et al. compared 116 patients who had undergone LVHR, 66 of whom received a polyester-based composite mesh and 50 a PTFE mesh [7]. No significant differences were noted in terms of recurrence rate, wound complications, meshrelated infections, or persistent pain with an average postoperative follow-up of 12 months. Chelala et al. [8] reported on the intraoperative findings of 85 reoperations after laparoscopic repair of ventral and incisional hernias with the polyester-based mesh Parietex Composite. They detected, after an average of 52 months, no adhesions in 47 % of cases, few adhesions in 42 %, and serosal adhesions in 11 %.
Wassenaar et al.
[10] presented a series of 65 patients who had a subsequent abdominal operation after more than 1 month after a laparoscopic ventral and incisional hernia repair (65 of 695; 9.4 %) with DualMesh. Only one patient required acute surgical intervention, which was due to a laparoscopic ventral and incisional hernia repair-related adhesion (0.15 %). Laparoscopy was performed in 83 % and laparotomy in 17 % of the patients. Adhesions to the implant were present in 83 % of patients; in 65 % the adhesions involved omentum only, and in 18 % the bowel was involved. The required adhesiolysis was uncomplicated, and there were no inadvertent enterotomies.
Heniford et al. [11] reported on a consecutive series of 850 cases of laparoscopic IPOM for ventral and incisional hernias with ePTFE (DualMesh). They identified a complication rate of 13.2 %. Ileus was seen in 3.0 % and longterm seroma in 2.6 %. A recurrence was noted in 4.7 % with an average follow-up of 20 months. Koehler et al.
Berger and Bientzle [13] reported on their experiences with 297 laparoscopic repairs of incisional hernias with PP/ polyvinylidene fluoride (DynaMesh). In that series, meshrelated infections occurred in 1 % but did not result in removal of the mesh. The rate of intestinal fistulas was 0.34 %. A recurrence rate of 0.6 % was found, but no longterm mesh-related complications were noted. As opposed to the good experiences reported by Berger and Bientzle [13] with DynaMesh, Fortelny et al. [14] reported a higher complication rate after laparoscopic IPOM repair of incisional hernias with DynaMesh. After a follow-up examination period of 1 year, adhesions necessitating reintervention occurred in 5 of 29 patients, and in 3 of 29 cases the mesh had to be explanted (an infection in one case required excision). At present, the above reports represent the only large clinical case series with use of defined ePTFE, PVDF, or composite meshes. There are a few scattered reports that pure PP mesh has been used without serious complications.
In 2000, Chowbey et al. [15] reported on 202 LVHRs with the use of pure PP meshes without a barrier material (the product was not named). In their series, there were two postoperative hernia recurrences at a mean follow-up of 2.9 years. The incidence of seroma formation postoperatively was 32 % in the first 3 years but declined to 18 % In a systematic review of the implants available for treatment of incisional and ventral hernias by Shankaran et al. [2], biological meshes are listed as a possible alternative. In this respect, biological meshes can be used in an extraperitoneal as well as an intraperitoneal position. The main advantage cited for biological meshes is their suitability for use in contaminated and infected surgical fields. Because biological meshes are revascularized and incorporated into the host tissue, they provoke a markedly less pronounced foreign body reaction compared to synthetic meshes. The relatively low concentration of inflammatory cells around a biological mesh may explain their successful use in a contaminated field. According to Shankaran et al., numerous studies have demonstrated that biological meshes can be used in contaminated fields. However, a study of the publications included in the clinical review by Shankaran et al. reveals that only six publications were actually truly evaluated for that review. All publications were retrospective case series. Only two publications explicitly focused on usage in a contaminated setting. The number of cases varied between 9 and 75. Overall, the patient cohort is so heterogeneous that extreme caution is advised when assessing the statement made by Shankaran et al. on the use of biological meshes in a contaminated situation.
Another systematic review from Bellows et al.
[26] shows that a paucity of high quality evidence exists in the peer-reviewed medical literature on the use of biological tissue grafts for incisional hernia repair. Although the rationale for using biological prosthesis for complex and contaminated incisional hernias is related to surgeons' concerns regarding the potential dire consequences of using permanent mesh in contaminated fields, there are yet any published prospective clinical trials justifying their preference over conventional mesh materials. Until such evidence is forthcoming, the use of biological prosthetics in complex incisional hernia repairs should proceed with caution. There may very well be a solid place for the use of these materials, but for them to add true value to complex hernia repair, better-designed and reported studies are necessary to help guide clinical practice.
Although most xenografts are used by surgeons in the setting of contamination, none of these biological meshes has received a US Food and Drug Administration (FDA) indication for use in this situation [27]. One particular interesting study reviewed the FDA database of adverse events associated with biological mesh. One hundred fifty adverse events were identified, with 80 % described as infection and 90 % necessitating reoperation [27,28].
Elective laparoscopic repair of incisional and ventral hernias with biological meshes in a noncontaminated field The LAPSIS study compared open retromuscular (mesh reinforcement technique) with laparoscopic repair (mesh bridging technique) in a prospective randomized trial. Here the non-cross-linked Surgisis Gold biological mesh was compared to a classic synthetic mesh. The defect sizes were between 4 and 10 cm. The number of cases calculated for the trial was 660. The primary target criteria were recurrence rate and reoperation rate. In a letter to the editor, the study directors announced the premature termination of the trial [29]. The reasons given for premature termination were too low a recruitment rate, incomplete trial data, and a higher recurrence rate in the group with the biological meshes. Four years after starting the trial, only 265 patients, i.e., 40.2 % of the total number of cases, had been recruited. For 257 patients, a 1-year follow-up was recorded. In the laparoscopic group, a recurrence rate of 19 % was noted for the biological mesh, and a recurrence rate of 5 % was noted for the group with the classic synthetic mesh. A similar result was also observed in the group comparing open retromuscular augmentation (11 vs. 3 %). No significant differences were found for any other end points.
The conclusion drawn by the authors was that caution should be exercised when using non-cross-linked biological meshes for elective laparoscopic bridging repair of incisional and ventral hernias if the alternative use of synthetic meshes was available. Likewise, in a contaminated setting, bridging of hernia defects with this type of a biological mesh should be avoided.
In a retrospective comparative study, Cobb and Shaffer [30] compared elective laparoscopic repair of incisional and ventral hernias using a bridging technique and a composite mesh made of PP and ePTFE (Bard Composix Mesh) with the biological mesh Permacol. Permacol is a cross-linked acellular porcine dermal collagen matrix. Eighty-four procedures were carried out using Bard Composix Mesh and/or Permacol in 55 cases by a single surgeon. In the Permacol group, 15 % of procedures were conducted because of recurrences, while in the composite group 20 % of procedures were for recurrences (p = 0.655). Postoperative wound infections occurred in 3.3 % of cases in the Permacol group and in 2.4 % of the composite group. Mean follow-up in the Permacol group was 14 months and was 31 months in the composite group. The recurrence rate in the Permacol group was 6.6 and 1.2 % in the composite group, and as such was not statistically different (p = 0.17).
The authors concluded that cross-linked acellular porcine dermal collagen was a safe alternative to composite meshes made of PP and ePTFE for elective laparoscopic repair of incisional and ventral hernias using a bridging technique.
Laparoscopic repair of incisional and ventral hernias with biological meshes in an infected or potentially contaminated field In a prospective trial with 116 patients, Franklin et al.
[31] reported on the use of the biological mesh Surgisis in potentially or grossly contaminated fields. All procedures were performed laparoscopically with two techniques: IPOM and two-layered sandwich repair. Once the defect was totally freed of adhesions and had been closed with no. 1 Tycra sutures whenever possible, the mesh was then introduced into the abdomen and stapled securely in place with an intracorporeal stapler. Most hernia repairs were performed by the IPOM technique, except for three patients in whom the two-layered sandwich technique was performed via laparoscopic and open implantation with reinforcement with Surgisis anteriorly and posteriorly by laparoscopy. Thirty-nine procedures were carried out in an infected field and the remaining in a potentially contaminated field. Ninety-one procedures were performed concurrently with a contaminated procedure. Twenty-five presented as intestinal obstruction and 16 as strangulated hernias; 17 required small bowel resection; 29 were inguinal hernias, 57 incisional hernias, and 38 umbilical hernias. In 13 patients, more than two different hernias were repaired. The mean follow-up was 52 ± 20.9 months. Eighty-five cases were followed up for 5 years, during which 7 recurrences (6 %), 11 seromas (all resolved), and 10 cases of mild pain were identified. Six second looks were performed, and in all cases except one, the mesh was found to be totally integrated into the tissue, with strong scar tissue corroborated macro-and microscopically.
The authors concluded that the use of small intestine submucosa mesh (Surgisis) in contaminated or potentially contaminated fields is a safe and feasible alternative to hernia repair with minimal recurrence rate and satisfactory results in long-term follow-up.
What happens to synthetic mesh after it is inserted into the body?
The search was performed in October 2011, and a total of two unique publications were returned from this search. Both were clinical studies. A secondary search revealed an additional 10 publications pertinent to this topic. Additional information on this topic was searched for on UpToDate.

Statements
Level 4 It appears that permanent synthetic (plastic) mesh used for hernia repair is not inert when placed in the patient's body

Recommendations
Grade D Because there is no way to predict the biologic interaction of each patient to each available hernia mesh, the patient should be informed of potential interactions and complications. The complexity and variability of the biologic interaction would also argue against the standardization of mesh within a hospital or outpatient surgery center, allowing surgeons and patients to have options between a variety of mesh choices Introduction Hernia repair is one of the most common surgical procedures currently performed. There are over 1 million hernias repaired in the United States alone each year, and of these, over 150,000 are for incisional hernias. The vast majority of hernias are repaired with a permanent synthetic (plastic) mesh material. We are now only beginning to realize the changes that occur to the mesh and the body after placing mesh into a dynamic biologic organism [32]. The potential advantages of synthetic mesh are that mesh is accessible (easy to manufacture and maintain), consistent (materials are reproducible), durable, and cost-effective (less expensive than biological materials). The first synthetic mesh was placed by Aquaviva in Marseille, France, in 1944, and then reported widely by Dr. Francis Usher [33, 34] in 1958. For over four decades, it was assumed that the mesh material remained inert after placement in the body. This analysis of current evidence will challenge that belief. Until recently, heavy-weight PP was by far the most commonly utilized mesh material. There are now a variety of PP-based meshes with varying densities and pore sizes as well as many meshes produced from other types of polymers. It should be noted that despite synthetic mesh reactions in the body based on current mesh explant analysis, most patients who have had mesh hernia repair have not developed mesh-related complications.
Research In the late 1990s and continuing into the last decade, mesh that had been explanted for a variety of reasons was studied by a number of techniques. Histological, scanning electron microscopic, and chemical analyses, infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and compliance testing have all been used to test and examine synthetic mesh, mostly from prior abdominal wall hernia repair, but also after pelvic floor reinforcement [35].
The meshes have been found to undergo changes as a result of the body's defense against foreign objects, as well as complex changes due to a chemical attack on the polymer structure [36]. There have also been many complications related to mesh hernia repair, and the result of this mesh-body interaction may be a contributing factor to these complications. Complications related to mesh interaction with the body include recurrence due to mesh contraction and/or migration, mesh erosion into viscera and/or through skin, chronic pain, functional issues resulting from lack of mesh compliance, acute and delayed mesh infection, acute and chronic inflammatory reactions including chronic active seroma, and rare systemic symptoms, such as flulike symptoms, potentially related to synthetic mesh. The variety of methods used to study mesh after explantation from the body are now presented.
Histology At the cellular level, the body will attempt to wall off, digest, or expel the foreign material. Cellular immunity is critical for survival, yet it creates problems in some (but not all) hernia patients. PP seems to have the greatest inflammatory reaction of the synthetic meshes, but this appears to decrease over time [37].
Neutrophils, lymphocytes, macrophages, and foreignbody giant cells are stimulated upon injury (surgery) and implantation of mesh material. These cells release enzymes and oxidants to degrade the foreign body-in this case, the mesh [38]. Study of mesh has shown oxidative breakdown in addition to encasement with inflammatory cells. Lymphocytes and foreign-body giant cells are present, and these can bathe the mesh in a continuous environment of oxidants while progressively encasing the mesh in a fibrous scar that can become increasingly rigid. This may be a contributing factor to chronic, and in some cases debilitating, pain [39].
The foreign-body response has been classified as having four distinct phases: acute inflammation, chronic inflammation, foreign-body reaction with development of granulation tissue, and fibrosis [38]. Heavy-weight PP meshes exhibit more collagen deposition and fibrosis, while lightweight meshes exhibit minimal fibrotic tissue with better neovascularization around the mesh [40].
The oxidants released by lysosomes can create superoxide anions as well as hydrogen peroxide and hypochlorous acid [41]. PP has been shown to undergo chain scission, and overall degradation with fissures, micro cracks, build-up of hydroxyl and carbonyl groups on the surface of the material, changes in thermal properties, and changes in mechanical properties such as embrittlement and reduced compliance.
There has also been discussion that the meshes generally shrink as a result of the above-listed changes. However, this contraction or shrinkage appears to be a complex and irregular process. Coda et al.
[42] studied multiple types of mesh and discovered that the explanted mesh pore sizes could have expanded up to 58 % as well as shrunk by 40 %.
Scanning electron microscopy Most micrographs have demonstrated changes to the PP mesh that include micro cracks in the transverse direction, as well as peeling of the top layer of fibers [40]. Other changes included superficial or deep flaking and fractures in the threads of varying lengths and depths [35]. Interestingly, polyethylene terephthalate did not appear degraded in two separate studies [35,43]. These findings are contrary to other reports on degradation of vascular grafts, and much more study of this complex biologic interaction is needed.
Fourier transform infrared spectroscopy Fourier transform infrared spectroscopy is a spectroscopic technique widely used to facilitate determination of chemical functional groups by their absorption frequency. In 2010, two studies examined multiple types of mesh [35,44]. These studies found that in virtually all types of synthetic mesh, peaks representing hydroxyl and carbonyl groups were present. This has even been noted in ePTFE, one of the meshes thought to be the least affected by alterations.
This indicated a chemical breakdown of the ''inert'' mesh that has potential implications for the strength of the polymer. Many of the hydrocarbon propylenes depend on van der Waals forces, and the alteration of the chemical groups can weaken these bonds. The overall effect may explain the changes in mesh seen in the tests mentioned below.
Differential scanning calorimetry This test measures melting temperature and heat of fusion in materials, and was tested in a variety of explanted meshes. This showed a shift toward lower melting temperature and broader melting peak. The clinical implication is not clear but demonstrates a change in the physical properties of the mesh.
Thermogravimetric analysis This measures weight loss of the material versus a pristine piece of mesh. This was lower for all mesh tested. This is now intuitive, as the material has been assaulted by the body, exposed to oxidative forces, and broken down chemically. This would also explain the mechanical failure of some lightweight meshes, which have been designed to lessen the host response with fibrosis and scarring, but sacrifice strength to achieve this.
Compliance testing This measures the mean value of work to bend the mesh in half using a constant force. Nearly all materials tested, even after removing all organic material, required more work and were less compliant than the pristine control mesh. However, this compliance testing revealed tremendous variability between explant samples [39,40].
Summary Since the early 1990, a diverse group of individuals, including materials engineers, chemical engineers, pathologists, device company representatives, and surgeons have made early attempts to begin to understand the changes that occur after mesh implantation in human beings. Animal experiments have not been able to show the long-term consequences of foreign-body implantation into biologic organisms. The host response is variable, and we have only begun to realize the individualization that will be needed to find the best mesh for a particular cluster of individuals. There will likely be groups of patients who will have a better outcome with certain types of mesh as well as certain groups of patients who will be at risk for increased mesh-related complications with certain types of mesh. To attempt to define these groups, an evolved understanding of clinical research based on principles of complex systems science will likely be needed.  The search produced 895 articles; with RCT (randomized controlled trial) filter 128 and Systematic Review filter, 39 papers resulted. Regarding open abdominal surgery and the indication for prophylactic mesh, six relevant publications were identified, whereas two level 2a, one level 2b, one level 3, three level 4, and one experimental study were stratified. For stoma surgery and indications for prophylactic mesh, four systematic reviews and one protocol for a Cochrane review were identified. There were 21 publications dealing with risk-reduction strategies to prevent incisional hernias.

Level 2
Prophylactic mesh placement reduces the rate of incisional hernia in risk groups with morbid obesity or aortic aneurysm Level 1 Prophylactic mesh placement in primary stoma formation reduces the rate of parastomal hernia without increasing morbidity, although this is based on small patient populations Level 2 There is no relevant difference between midline and transverse incisions regarding the incidence for incisional hernia formation The objective of this study was to find evidence for the use of prophylactic mesh to minimize the risk for incisional hernia. A small case series with a prophylactic mesh placed in the preperitoneal space after open AAA repair resulted in a low rate of incisional hernia after a median follow-up time of 47 months [58]. A well-conducted RCT with a 3-year follow-up showed a significant reduction of postoperative incisional hernia after AAA repair without increasing the rate of complications, although patients with previous abdominal surgery were not excluded [59].
The first RCT with long-term results after prophylactic mesh to prevent incisional hernia in obese patients did not reveal an advantage for the mesh group [60]. However, it must be noted that the study group used a resorbable polyglactin mesh.
A case series with 60 patients undergoing gastric bypass surgery and a midline incision closure with a nonresorbable PP mesh demonstrated an effective prevention of incisional hernia [61]. The same group conducted a RCT for the prophylactic use of a mesh with a mean follow-up of 28 months and found an incidence of over 20 % incisional hernia in the nonmesh group and none in the mesh group [62]. The strength of this research was weakened as a result of the lack of a blinded arm and the small number of patients. A prospective study without randomization of 100 high-risk patients (including neoplastic pathology, age over 70 years, respiratory failure, malnutrition, obesity, and smokers) also showed a significant reduction of the development of incisional hernia with the use of a prophylactic PP mesh [63] ( Table 2). In a two-institution nonrandomized prospective trial in which a biologic mesh was applied to one patient group compared to the nonmesh group at the other institution after gastric bypass, a reduction of the incidence of incisional hernia in the mesh group was revealed [64]. All these RCT studies show substantial weaknesses regarding the study design and methods, resulting in downgrading of their evidence level. An ongoing double-blind randomized controlled multicenter trial, PRIMA, includes both high-risk groups with patients being operated for AAA or other median laparotomies with a body mass index (BMI) of over 27 kg/m 2 [65]. The recruitment process is accomplished, and the publication of the trial is awaited. , included 27 patients scheduled for permanent end colostomy surgery in each group. This study had a median follow-up of 29 months. A hernia rate of 40.7 % was observed in the nonmesh group versus 14.8 % in the mesh group. This was significantly lower (p \ 0.05) and was not associated with any meshrelated complication.
Three other systematic reviews and one Cochrane review have been published; the latter includes the same three RCTs [76-79]. A total of 128 patients (mesh 64, nonmesh 64) were eligible and analyzed in the latest review by Shabbir et al. They concluded that despite a small patient population, it could be demonstrated that the use of a prophylactic mesh at the primary stoma operation reduced the incidence of parastomal herniation with a very low morbidity. A large RCT to focus on mesh material and anatomic location is needed to confirm these findings. Closure technique There is no consensus in the surgical community regarding wound closure techniques after laparotomies as shown in a cross-sectional cohort study [85]. Several RCTs are available that focus on this issue, and five systematic reviews pooled the available data without defining homogenous study populations and follow-up [47, 86-89].

Risk-reduction strategies
With precisely defined study populations and follow-up periods, the INLINE systematic review and meta-analysis revealed the highest available evidence [90]. The risk for incisional hernia after elective median laparotomy is significantly lower if the fascia is approximated with a continuous suture technique using slowly absorbable suture material. For emergency settings, the results of the randomized controlled multicenter trial, CONTINT, must be awaited [91].
Technical aspects of suture techniques are suture length and stitch width. In a prospective trial with 363 patients after midline laparotomy in elective and emergency settings, Israelsson and Jonsson [92] found an overall . Additionally, long stitch length was identified as an independent risk factor for surgical site infection The authors recommended the use of a 150 cm long 2-0 (USP) suture with a small needle to accomplish a suture length to wound length ratio of at least or more than 4. The small needle is suggested to prohibit be ability to achieve large bits of tissue. Gaining 1b evidence is the question of whether the ''small bite'' stitch technique is superior to the commonly used ''big bite'' technique in terms of costs and effectiveness. To further investigate this claim, a randomized controlled multicenter trial, STICH, was initiated and is currently active [101]. . In contrast to all other laparoscopic procedures, acute and chronic pain does not seem to be reduced after laparoscopic IPOM operations. The IPOM technique is performed with expensive composite meshes, the bowel-facing surface of which is covered with an adhesion preventing material or pure ePTFE. IPOM meshes have to be fixed securely with transfascial sutures, staples, or clips, which carry the risk of adhesion and/or acute and chronic postoperative pain. The long-term safety of IPOM meshes has not been proven in clinical studies.
Other potential disadvantages of the laparoscopic IPOM repair are as follows: in most cases, the hernia sac stays in situ, the defect is bridged, and the abdominal wall is not reconstructed; adhesions between the viscera and abdominal wall have to be taken down; and severe complications such as bowel injury appear to be more common.
For a further improvement of abdominal wall hernia repair, the advantages of the sublay repair and laparoscopic IPOM repair should be combined. The question is, can a preperitoneal ventral and incisional hernia repair be achieved with fewer complications and better long-term results?
The conclusions and recommendations on laparoscopic preperitoneal ventral and incisional hernia repair are based on a systematic review of the literature and a consensus conference on guidelines for the laparoscopic treatment of ventral and incisional hernias held in October 2011 Suzhou, China, during the fifth meeting of the International Endohernia Society (IEHS). In a prospective cohort trial with a control group, Schröder et al. (under review) report on a three-port laparoscopic transperitoneal sublay repair technique via the left flank. In 43 small-and medium-sized ventral and incisional hernias, medium-and large-sized pieces of standard PP mesh (15 9 15 cm up to 30 9 20 cm) were implanted. The follow-up rate was 92 % with a median of 16 months.

Statements
Compared to the open sublay repair group, there was less acute pain and the hospital stay was shorter. However, operating time was longer in the laparoscopic group. There were no differences in chronic pain and discomfort. In both groups, no recurrences or wound infections were noted. The authors concluded that laparoscopic transperitoneal sublay repair is a safe and effective method for the treatment of small-and medium-sized primary and incisional abdominal wall hernias combining the advantages of open sublay and laparoscopic IPOM repair.
Endoscopic total extraperitoneal preperitoneal abdominal wall hernia repair Three publications describing 17 cases of endoscopic total extraperitoneal mesh repair of Reinpold et al. (oral presentation, EHS Congress, Istanbul, 2010) developed a transhernial single-port TEP technique for the treatment of primary and incisional abdominal wall hernias. The hernia sac and midline defect are dissected through a 3-to 4-cm incision. The extraperitoneal space around the defect is enlarged by separation of the peritoneum from the fascia. Large hernia sacs are removed and defects of the peritoneum are closed. A single port with three 5-mm trocars is inserted into the defect. Using a pneumoperitoneal pressure of 10 mmHg, the circumference of the defect is dissected endoscopically. A standard PP mesh is inserted in the sublay position and fixed with sutures or tacks at the lateral border. Alternatively, a self-fixating mesh can be used. The midline defect is closed via the port incision. Twenty-four patients with an average defect size of 17 cm 2 (range, 9-61 cm 2 ) were operated on. The average mesh size was 232 cm 2 (range, 96-600 cm 2 ). Pain medication was stopped in all patients after a maximum of 4 days. Two small retromuscular hematomas were treated conservatively. After an average follow-up of 8 months (range, 2-15 months), there was no chronic pain, recurrence, or infection.
Conclusion Laparoscopic preperitoneal abdominal wall hernia repair via the TAPP and TEP techniques in smalland medium-sized primary and incisional abdominal wall hernias is feasible and has minimal morbidity. The advantages are: (1) access causes minimal trauma; (2) standard mesh with minimal fixation can be used; (3) the abdominal cavity is only minimally entered; (4) the hernia sac is removed from the abdominal wall; and (5) the hernia defect is closed and the abdominal wall is reconstructed anatomically. However, the technique is more demanding and takes longer to perform than standard procedures.

Level 3
The ECS is feasible with low morbidity [115] is as follows: below the costal margin and lateral of the rectus compartment, a bilateral 15-mm skin incision is created and a 10-mm balloon dilator is inserted. Blunt dissection is performed of the avascular space between the external and internal oblique muscle. Two trocars are inserted, CO 2 is insufflated, and further dissection is done of the space under camera vision. The fascia of the external oblique muscle is vertically incised lateral to the rectus compartment from the costal margin to the inguinal area.
The residual defect size after the removal of all prosthetics was 338 cm 2 (range, 187-450 cm 2 ). ECS enabled tension-free primary fascial reapproximation in all patients. There was one superficial surgical site infection. After an average follow-up period of 4.5 months, no recurrences were identified.
Harth incidence is not easy to establish because this problem is underestimated by both patients and physicians. The reported incidence rate ranges from 2.8 to 50 % [123] and appears to be directly related to the length of follow-up. Loop ileostomy has the lowest risk (0-6.2 %), followed by end ileostomy and loop colostomy, which has a similar risk of 28-30 %. End colostomy carries the highest risk for parastomal hernia of more than 50 %. Even though most hernias occur within the first 2 years after stoma construction, the risk of herniation extends up to 20 years [124]. Although many risk factors have been related to the development of a parastomal hernia, waist circumference, patient age, and stoma size are independent risk factors for the development of a parastomal hernia after a permanent colostomy [124,125]. Parastomal hernia is asymptomatic most of the time, but it may be associated with serious complications such as strangulation and perforation; elective repair is thus mandatory for many selected cases. The diagnosis is generally made by clinical examination. The computed tomographic scan is very useful to determine the content of the hernia, the size of the defect, and the existence of a concomitant hernia at the midline or other incisions.
Many different surgical techniques have been described for the treatment of parastomal hernias. Nonmesh techniques are known to have a high rate of recurrence (46-100 %) and should generally not be performed [126,127] because the mesh techniques offer significantly better results. Meshes could be placed as an onlay or sublay through a local incision close to the stoma. However, these techniques have an incidence of wound infection of up to 30 % [128, 129]. The underlay or IPOM position not only offers a decreased rate of wound infections but also affords the opportunity to repair a concomitant incisional hernia, if present. The laparoscopic approach achieves the advantages of a minimally invasive approach with the low incidence of infection and recurrence rate that the intraabdominal placement of a mesh offers.
A and known as the sandwich technique are used. The laparoscopic approach makes a peristomal incision unnecessary and also decreases the potential risk of mesh infection. Published series on laparoscopic mesh repair of parastomal hernia, however, are few, with relatively short follow-up.
There are two studies with level 3b evidence that compare the open approach with the laparoscopic techniques to repair parastomal hernias. Both papers are retrospective studies, but the one conducted by McLemore et al. [132] includes in the open group cases in which a suture repair was performed together with mesh techniques and relocation of the stoma (associated with differing rates of recurrence). On the other hand, this author also included a laparoscopic group of cases performed after the keyhole and the modified Sugarbaker technique. Both techniques are associated with a different rate of recurrence.
The most important message coming from the other study with level 3b evidence, conducted by Pastor et al.
[131], is that the morbidity rate of the laparoscopic approach was 15 %, while the complications after the open approach were up to 33 %. This same study showed a lower recurrence rate after the laparoscopic approach than after the open technique (33 vs. 53.8 %). It was noted that the time of the follow-up was different (13.9 vs. 21.4 months) in the two groups. Therefore, it was noted that the rate could increase with time.
In order to draw conclusions regarding recurrence, it is best to analyze the studies with level 4 evidence. Even though there are some cases series with high recurrence rates of up to 56 % [146], most of the studies report a recurrence rate below 10 % with the laparoscopic approach. This represents a much better recurrence rate than the results of the open approach. At present, none of the methods of open or laparoscopic mesh repair has proved superior. In spite of this, laparoscopic repair has gained increasing acceptance.
Does laparoscopic parastomal hernia repair have similar results when compared to laparoscopic ventral hernia repair?
Statements Level 4 Operative times for parastomal hernia repair are longer than a LVHR because the technique is more difficult, especially because of a more difficult process of adhesiolysis Intraoperative complications during laparoscopic repair of parastomal hernias are more frequent than during standard LVHR A high percentage of parastomal hernias are associated with an additional midline incisional hernia, which makes the surgical procedure more complex The rates of both recurrence and morbidity are higher after laparoscopic parastomal hernia repair than after LVHR

Recommendations
Grade C A laparoscopic approach of parastomal hernias should be considered a difficult technique with longer operating time, more intraoperative complications, and more difficult adhesiolysis than standard LVHR Results of laparoscopic repair of parastomal hernias could not be compared to the general results of LVHR because the rates of recurrence and morbidity are higher Laparoscopic repair of parastomal hernias is a more complex technique because a concomitant midline hernia present in a high percentage of patients must also be repaired Discussion If we compare the results of laparoscopic repair of parastomal hernias with the data published with level 1a evidence on LVHR, we observe that the surgical time associated with the laparoscopic repair of parastomal hernia is longer and the morbidity higher [157,158]. These data show that this technique seems to be more difficult than standard LVHR because of the presence of more dense adhesions and the frequent concomitant midline incisional hernias. It is also more challenging to separate the adhesions of the ostomy itself from the omentum and other intestines. Additionally, the rate of infection of a LVHR is close to zero, but the rate of postoperative infection or other late mesh-related complications is higher after laparoscopic parastomal hernia repair. It has been reported to be as high as 7-9.5 % [137, 141]. The conclusion of this comparison is that laparoscopic parastomal hernia repair is a more complex procedure than standard LVHR and should be performed by an expert surgeon.
A comparison between the data observed in different studies with different levels of evidence for the LVHR reveals that the overall recurrence rate of this technique is lower than the recurrence rate observed after laparoscopic repair of parastomal hernias. This can be explained by the complexity of the latter technique and by the relative early stage of its development; the best technique-keyhole, Sugarbaker, or sandwich-remains to be defined. There is an increasing amount of evidence that laparoscopic mesh repair is feasible and has a promising potential in the management of parastomal hernia.
Which is the best laparoscopic technique for repair of parastomal hernias?

Level 3b
Laparoscopic repair of parastomal hernias using a pure ePTFE mesh is associated with better results than the keyhole technique The same laparoscopic technique can be performed for a hernia occurring with a colostomy, ileostomy, or urostomy, or due to an ileal conduit Discussion Laparoscopic parastomal hernia repair has become a viable option to overcome the challenges that face the hernia surgeon. Most series suffer from a small sample size, and controlled trials are lacking. These limited data make it difficult to draw firm conclusions. Two laparoscopic techniques have emerged: the use of a mesh with a slit and a central keyhole and a mesh without a slit. The latter is often termed the modified Sugarbaker. A third option, the sandwich technique, has been also been described and consists of a combination of both techniques. Published series, however, are observational and often have a short follow-up. There is only one comparative study with level 3b of evidence: that of Muysoms et al. [133]. In this study, the authors show that the modified Sugarbaker technique offers significantly lower recurrence rates than the keyhole technique (72.7 vs. 15.4 %), although the follow-up of those cases performed following the Sugarbaker technique is shorter than the rest of the cases (30.7 vs. 14 months). Together with this study, Hansson et al.
[68] showed a very low recurrence rate (18 %) when the keyhole technique was used with shortterm follow-up (6 months). A later publications from the same author [138], with a follow-up of 36 months, demonstrated that the rate of recurrence with this technique was high (37 %). In these three studies, the mesh used was a pure ePTFE mesh. This would lead to the conclusion that one should avoid the keyhole technique if this material is chosen. The Sugarbaker repair should be performed instead.
Reported series using other meshes with the keyhole technique (ePTFE-PP mesh) show a low recurrence rate In summary, the quality of evidence for the various surgical techniques for parastomal hernia repair is low and precludes firm conclusions. RCTs would be ideal to compare the various techniques of parastomal hernia repair, as none has been reported to date.

Section 10: New technologic developments
From robotic surgery to NOTES and single-port surgery: Is there currently any role in ventral hernia repair?

Level 4
Robot-assisted ventral hernia is a feasible alternative to laparoscopic repair of ventral hernia Intracorporeal suturing under direct visualization allows stable suture fixation of the mesh Helicoid tackers and transabdominal sutures contribute to postoperative pain

Recommendations
Grade C More studies must be conducted on the feasibility, practicality, and success of robot-assisted ventral hernia repair Laparoscopic surgery requires a high degree of special resolution, dexterity, and technical skills as a result of the lack of depth perception, tactile sensation, and force feedback. New technologies have been developed to improve the ergonomics and the drawbacks of minimally invasive surgical robotic devices. In any surgical procedure, and especially in laparoscopic surgery, technical skills, experience, decision making, and manual skills are major predictors of outcome. If a surgical manipulator computer-controlled device can improve performance and outcome, patients will benefit [159, 160], especially in a procedure where the learning curve is steep like hernia repair [161,162]. Since the first successful laparoscopic repair in 1993 [163] and subsequently the advent of this surgical manipulator, many groups worldwide have tried to experience and the benefits of the use of robotic device in ventral hernia repair [164][165][166].
Comments Few studies have been published that analyze the benefits of robotic devices in ventral hernia repair. More studies must be conducted on the feasibility, practicality, and success of the robot-assisted ventral hernia repair. Schluender et al. [163] showed that the robotassisted laparoscopic repair of ventral hernia using intracorporeal suturing allowed for stable suture fixation under direct visualization and eliminated the need for tackers. Tayar et al. [164] confirmed the benefits of the da Vinci system for intracorporeal suturing in humans.  The actual benefits of NOTES, however, have yet to be proven because most research into this exciting new field is focused on small trials involving animal models [172]. Although substantial knowledge has been gained from these studies in a relatively short time, many safety issues have to be considered especially when challenging the time-honored basic surgical principles of the avoidance of unnecessary enterotomies by going beyond the natural borders of the mucosa [173]. Some human experience has been gained, but the technique is currently considered experimental; it has received much criticism and skepticism amid the enthusiasm [172]. A review of human NOTES experiences shows that so far, all have been performed under the guidance, assistance, or monitoring of concomitant laparoscopy in a hybrid setting. Multiple constraints in performance of NOTES have been identified [176]. Principally, present endoscopic systems are not designed with sufficient dexterity for NOTES procedures. Performing NOTES with today's endoscopic instrumentation is technically difficult as a result of the limited endoscopic field of visualization and considerable constraints in the ability to maneuver the instruments within the small confines of the peritoneal cavity. In NOTES, offaxis operation is often necessary. Tasks such as tissue approximation and dissection require independent coordination of two instruments approaching from different angles. However, the parallelism of standard endoscopic fixtures limits the degree of freedom for optimal surgical maneuvers and does not permit much triangulation of endoscopically deployed instruments to approach the surgical target. For these reasons, experimental NOTES in humans have thus far focused on technically less challenging procedures. Hypothetical benefits of NOTES include the following: the entire abdominal fascia at risk for herniation can be visualized; the chance of port-site hernias is reduced; the cosmetic result is better because of minimal or no scarring; and there is less pain [177].
Comments The platform and technology necessary to perform NOTES are still under development. Most of the reported surgical procedures are hybrid procedures. Comparisons should look at both simple and difficult procedures. Delivery of a foreign body (mesh) through a colonized natural orifice may increase chronic mesh infection compared to laparoscopic techniques. Results from studies drew different conclusions. Few studies reported an increased mesh infection rate in their subjects [178][179][180], while others [181][182][183] showed that bacterial contamination and intra-abdominal morbidities were not encountered during surgeries when using the transvaginal approach compared to the transgastric route. Ventral hernia repair using the NOTES approach seems to be safe and feasible in both experimental groups and in the few initial reports in humans [177][178][179][182][183][184][185][186].

Level 4
Single-port access ventral hernia repair appears to be safe for experienced endolaparoscopic surgeons. It may decrease parietal trauma and scarring in patients prone to incisional hernia and may be associated with a decrease in the rate of port-site hernia compared to multiport laparoscopy

Recommendations
Grade C Single-port access ventral hernia repair seems to be a safe and feasible alternative option to conventional laparoscopy in selected cases, but further RCTs are needed In the last few years, minimally invasive surgery has continued to develop by further reducing surgical injury and scars. This new approach (NOTES) has created a lot of enthusiasm, but several issues and challenges have arisen that need to be resolved before full clinical acceptance [187][188][189]. While improving on these procedures, the idea of reducing the number and size of ports, so-called single incision access surgery evolved. Through a small incision (1.5-2.5 cm), the single-port device can be inserted, which can then allow access of multiple sites for the laparoscope and instruments to carry out the surgery. Early reports of different procedures have been published. It appears that the cosmetic advantage offered by single-port endolaparoscopic surgery makes this approach an attractive option for patients who desire an additional benefit of cosmesis. Further clinical studies involving large series of patients are needed to confirm the benefits and advantages of single-port endolaparoscopic surgery over standard procedures. There have been a few case reports published on inguinal [190,191] and ventral hernia repair, with promising results [192][193][194][195][196].
Comments The literature reviewed demonstrates that the procedure is feasible, safe, and reproducible. No intraoperative complications were observed. Standard instruments were used. Patients were discharged on the first day after surgery.

Section 11: Lumbar and other unusual hernias
Are lumbar and other unusual hernias suitable for laparoscopic repair?

K. A. LeBlanc, R. H. Fortelny
Search terms: Flank hernia repair, flank hernia repair with mesh, lumbar hernia repair, lumbar hernia repair with mesh, unusual hernias of the abdominal wall, spigelian hernia, spigelian hernia repair, lateral incisional hernia, traumatic lumbar hernia, Grynfelt OR Grynfelt's hernia, Petit OR Petit's hernia; the above AND repair, the above AND laparoscopy, lumbar hernia AND lumbar muscles AND paralysis, lumbar hernia AND lumbar muscles AND paralysis AND bulge, lumbar hernia AND lumbar muscles AND paralysis AND nephrectomy, lumbar hernia AND nephrectomy.
Searching machines: PubMed, Embase, and Medline (2000-2011) were searched. The use of mesh to repair these hernias by both approaches is recommended. However, the laparoscopic repair is preferred because of lower postoperative morbidity and reduced length of hospital stay. This represents an ''upgraded'' recommendation because of the clear superiority of the use of mesh for these hernias Introduction These two types of hernias are rare.

Statements: Lumbar hernia
Although most surgeons will have an opportunity to repair a spigelian hernia within their careers, many will never see a true lumbar hernia throughout their working career as a result of its extreme rarity, although its incidence may be increasing because of the more frequent use of the lumbar approach for anterior fusion of the lumbar spine. However, many of these bulges are the result of intercostal nerve injury and subsequent paralysis of the flat muscles of the abdominal wall. The first suggestion of the existence of the lumbar hernias was by Barbette in 1672, but the first publication regarding these entities was by Garangeot in 1731. It is believed that the first surgical repair of a strangulated lumbar hernia occurred in 1750 by Ravaton. However, Petit and Grynfeltt's names are associated with these hernias rather than the other surgeons because they provided the first anatomic description of the inferior lumbar space (Petit in 1783) and the superior lumbar space (Grynfeltt in 1866). The boundaries of the inferior lumbar hernia are the latissimus dorsi muscle posteriorly, the external oblique muscle anteriorly, and the iliac crest inferiorly. The boundaries of the superior lumbar hernia are the 12th rib superiorly, the internal oblique muscle anteriorly, and the erector spinae muscle posteriorly.
Selby described traumatic acquired lumbar hernia in 1906, and Kelton noted incisional acquired lumbar hernia in 1939. In 1951, Kretchmer published the first study of 11 of these latter hernias after renal surgery [197]. The ratio of congenital and acquired hernias has remained stable over Level 2b Laparoscopic repair is superior because of reduced morbidity rates and length of hospital stay Currently there are many methods and meshes to repair all of these defects. Similar to the lumbar hernias, the name of the spigelian hernia is credited to someone who clarified the anatomic description of the entity, Adriaan van den Spieghel (1578-1625). This hernia occurs at the level of the semicircular line where the fascias of the oblique and transversus muscles begin to split to for the two separate layers of the abdominal musculature. Generally the overlying external oblique fascia remains intact, making this herniation interstitial and more difficult to diagnose. These entities are more common than that of the lumbar hernias.
Discussion In this account, we have dealt with lumbar and spigelian hernias separately because they are separate entities. We searched the PubMed and Embase databases as well as the Cochrane register using the search terms noted above for publications that appeared from 1960 to 2011. Not unexpectedly, few publications could be used for an evidence-based systematic review on the treatment of both types of hernias. The relevant publications consisted of case series that included at least five cases. We excluded single case reports.
We were also charged to investigate the unusual hernias that were located in other locations. With these we were able to identify 48 articles but all were either single case series or did not really deal with the repair of the hernia. Hence none could be used for the systematic review. The search culled 35 articles under ''flank hernia,'' but these were either case reports or did not address any aspect of hernioplasty. No articles were found that dealt with lateral bulging after a denervation injury after nephrectomy or anterior lumbar disc surgery. Seventy-nine publications were found that described lumbar hernias or their repair. Fourteen were case series of fewer than five cases. Two were solely anatomic descriptive articles, and one was a publication that duplicated already published data. We were able to include in the review 12 papers, which contained five or more patients and one prospective randomized study. No publication had level of evidence 1a, 1b, 2a, 2c, or 3.  [198]. From these reports, a total of 123 patients could be evaluated. In four patients, the method of repair could not be determined from the article. The methods of repair used in the other 119 patients are shown in Table 3.
Unfortunately, only 108 patients listed in Table 3 had adequate follow-up. These consisted of 28 patients with an open sutured repair, 31 with an open repair with mesh in any location, and 49 patients with a laparoscopic repair with mesh in any location. No recurrences were reported in any group of patients, but the length of follow-up varied from 1 to 40 months for the entire patient population. Given these results, it would appear that any method of repair for the lumbar hernia-sutured or with mesh placed by any method or location-appears to be an acceptable operation.
[211] performed a review of the literature and included two cases of their own. On the basis of this review and their experience, their conclusion was that a combined open and laparoscopic repair using transfascial sutures with or without bone anchors was the best method to treat these difficult hernias. Stumpf et al. [212] performed cadaver dissections to address the problem and concluded that mesh should be used and placed in the sublay position between the internal and external oblique muscles.
The spigelian search revealed 397 articles. Of these, spigelian hernia was noted in 391, but only 95 of these reported on repair of these defects with a sufficient number of patients. The ''spigelian hernia repair AND adult'' . In this small RCT, patients were randomized to either an open or laparoscopic repair arm, with 11 patients in each arm. All meshes were placed in the preperitoneal space except for three in the laparoscopic group, where the mesh was placed in the intraperitoneal space. The laparoscopic repair was accompanied by lower postoperative morbidity (p \ 0.05) and reduced length of hospital stay (p \ 0.001). The authors concluded that the laparoscopic extraperitoneal repair should be the preferred treatment for these hernias.
The majority of the level 4 evidence articles were series of patients with an open sutured repair. Several were identified that included the diagnosis and treatment of the hernia but could not be included because no morbidity or follow-up data were provided. Length of follow-up varied greatly among the series. The cumulative data are shown in Table 4. It is obvious that the use of mesh is preferred. In the three series that included patients who underwent repair without the use of a mesh, the recurrence rate was 4-14 %. There were no recurrences in any series that included mesh in the repair either with the open or laparoscopic technique. The mesh was placed in the intraperitoneal, extraperitoneal, or intra-aponeurotic locations without the development of a recurrence.

Section 12: Education
Education and training in laparoscopic ventral hernia repair
Searching machines: PubMed, Embase, and Medline (2000-2011) were searched. Medical education is undergoing a paradigm shift from the traditional experience-based model to a program that requires documentation of proficiency [228].
Laparoscopic surgery requires a high degree of special resolution, dexterity, and technical skills. An initial training period is usually required for the majority of surgeons to become proficient in complex procedures by continuous repetition of these tasks [229][230][231][232][233]. Clinical outcome and complication rates are dependent on operator experience in those procedures. Surgeons who are less experienced in laparoscopic surgery and in LVHR will have higher complication rates. These results will be demonstrated by smaller scars, less postoperative pain, shorter hospital stay, lower recurrence rates, fewer infectious complications compared to open repair, and lower overall cost.
Surgeons recognize technical issues, operative decision making, and manual skills as major predictors of outcome [160,234]. A learning curve for a specific procedure can be evaluated by means of operative times, but mainly the rate of conversions (for endolaparoscopic surgery) and complications. In the case of hernia repair, it is generally accepted that the learning curve for performing endoscopic inguinal hernia repair is longer than for open Lichtenstein repair, although the Lichtenstein technique also has a learning curve with respect to prevention of recurrence and chronic groin pain. However, this learning curve seems to be shorter than that for the endoscopic techniques [160,161]. This is especially the case for endoscopic TEP repair as a result of a limited working space and different appreciation of the usual anatomical landmarks seen from inside the peritoneal cavity or through an anterior approach. There appears to be a higher rate of rare but serious complications with laparoscopic repair, especially during the learning curve period. Adequate patient selection and training might minimize these risks of infrequent but serious complications in the learning curve period [235][236][237][238][239].
Similarly for ventral hernia, the surgical treatment has undergone a paradigm shift in terms of repair, from simple suture repair to mesh repair to the first successful laparoscopic repair in 1991 [163]. LVHR, like any other minimally invasive procedure, offers advantages but has its own challenges: the challenge of any other minimally invasive procedure, familiarity of new instruments (meshes, tackers, suture passers, etc.), and familiarity of laparoscopic anatomy (though minimal for an experienced laparoscopic surgeon) [163,[240][241][242]. The exact definition of the learning curve in laparoscopic procedures is unclear [234]. Possible factors that may influence the learning curve may include the surgeon's experience with other laparoscopic procedures and instrumentation, knowledge of laparoscopic anatomy, standardization of surgical technique, and reduction of operative time and complication rate. On the basis of limited or no data on training or on the learning curve of ventral hernia repair, we suggest that a minimal training of 15-20 cases is required by experienced laparoscopic surgeons to tackle the difficulties of the technique and to achieve comparable clinical outcome in terms of complications, operating time, and recurrence [162,[243][244]. Supervision by an experienced surgeon may help reduce the learning curve, as suggested in several studies for other procedures, including inguinal hernia repair [231,238,239].
Complex abdominal wall hernia repair should be performed in specialized centers. These centers seem to have better outcomes than general surgical units, especially for endoscopic repairs and complex inguinal hernia surgery (multiple recurrences, chronic pain, mesh infection, etc.), and such hernias should best be treated by a hernia specialist [230,247,248]. It is unclear whether subspecialty training, center volume, and/or surgeon volume are equally important to determine the outcome [245], but for many procedures, the observed associations between hospital volume and operative mortality are largely mediated by surgeon volume [246].
A structured laparoscopic training program in hernia repair improves operator outcomes in the operating room and surgical outcome because this allows the surgeon to learn directly from experts about the challenges encountered during the procedures and how to overcome them. This, followed by supervision and/or proctoring, can be useful in achieving good clinical results and to shorten the learning curve. Even a 1-day course may affect the surgeon's practice, especially regarding hernia repair [247,248].
In the era of information technology and computer simulation, training in ventral hernia has been positively influenced by these new devices [249][250][251]. Laparoscopic training by virtual reality simulators has shown a proven benefit in terms of improved operator performance in the operating room, even in LVHR [252-254].
or absorbable fixation. The ingrowth of the mesh and tissue also reveals the issue of abdominal wall preparation before the mesh will be placed and fixed (the so-called landing zone).
All of the above factors will aid in the future design of individual meshes for different hernia locations, its dimensions, fascial structure combined with anterior abdominal wall imaging (3D computed tomographic or magnetic resonance imaging models) and perhaps biological products used for mesh construction. We will perhaps realize the development of 3D printing and the use of this equipment for creation of ''personal'' mesh. The future exploration of our field should encompass the identification of the specific mesh types and methods to implant them on the basis of the clinical comorbidities of the patient who is being treated. For mesh repairs, we need to define the appropriate size of pores as well as determine the strongest product with the least risk of infection while providing a very low rate of recurrence; these await identification.
Clinical questions, based on our ongoing observations of outcomes, can only be answered if more clinical studies are performed: