Mesh and plane selection: a summary of options and outcomes

Introduction

Defects in the anterior abdominal wall with a resulting ill-defined bulge are both aesthetically displeasing and are associated with musculoskeletal and gastrointestinal dysfunction. The field of abdominal wall reconstruction is a complex topic that comprises a large practice approached by both plastic and reconstructive surgeons and general surgeons. Over one-quarter of all individuals have or will develop a hernia in their lifetime^[1]. Although the true incidence of incisional hernias is difficult to ascertain, approximately 348,000 hernia repairs were performed in the United States in 2006^[2]. Ventral hernias are an encapsulating term referring to anterior abdominal wall hernias that include the following: epigastric, umbilical, spigelian, parastomal, and most incisional hernias. In the United States alone, over 3.4 billion dollars are spent on the management of hernias^[1]. The standard approach to ventral hernia repair and the realm of abdominal wall reconstruction is that of repair of the fascial defect with reinforcement of the abdominal wall with mesh. There are many facets to the completion of a ventral hernia repair, including approach to repair, mesh type selection, and mesh plane selection. The approach to the repair can be completed open or through minimally invasive techniques. Presently, minimally invasive techniques utilize both laparoscopic and/or robotic platforms. The selection of the mesh can be that of a prosthetic or biologic variety. Finally, the location in which the selected mesh is placed is crucial to the integrity of the repair. The focus of this review is the latter of these three facets: the choice of mesh and the anatomic location of mesh.

Mesh location

The ideal anatomic location for mesh placement during the repair of ventral hernias or abdominal wall reconstruction has been debated; however, the most common anatomic locations include: onlay, inlay, sublay-retromuscular, sublay-preperitoneal, and sublay-intraperitoneal [Figure 1]. Numerous single-institution studies, reviews, and meta-analysis have been completed on this topic, still without clear consensus on the ideal location of mesh. The anatomic location of the mesh has an influence on how the mesh is incorporated with the tissues, the tensile strength of the repair and the abdominal wall, and finally the immune reaction between the mesh and the tissue^[3]. We strive to summarize the advantages and limitations of these locations to make an argument for the ideal mesh plane for ventral hernia repair in abdominal wall reconstruction.

Figure 1. Abdominal wall demonstrating mesh planes

Onlay mesh placement is the placement of mesh on the anterior fascia and is sometimes referred to as a premuscular location of mesh^[4]. This technique, popularized by Chevrel in 1979, is typically approached in an open fashion with the placement of mesh over the anterior fascia following closure of the fascial defect. The key tenets of this approach include the reapproximation of the linea alba and fixation of mesh to the anterior fascia, which requires the creation of lipocutaneous flaps and the sacrifice of the periumbilical umbilical perforator vessels. The key to the onlay mesh is based on Chevrel’s exploration of human cadavers anterior and posterior rectus sheaths. In his 1997 study on cadaveric specimen, Chevrel describes the burst strength of the anterior rectus sheath above the arcuate line to be the strongest portion of the abdominal wall which forms the basis for the onlay approach. He suggests that the strongest reinforcement for the abdominal wall is the combination of the native strength of the anterior rectus sheath in combination with the strength of polypropylene mesh^[5].

The inlay (or interposition) technique, as defined by Parker et al.^[6], is characterized by an approach that places the mesh within the hernia/fascial defect with the mesh fixated to the edges of the neck of the hernia. By definition, the inlay placement of mesh requires a bridging mesh regardless of where the mesh is fixated. If the fascial defect closure is not achieved, this is also considered an interposition mesh. This approach can be completed open, as well as via a minimally invasive approach.

The sublay-retromuscular technique describes mesh placed posterior to the rectus muscle and anterior to the posterior rectus sheath. This plane continues below the arcuate line as the plane between the rectus abdominis muscle and the transversalis fascia^[6]. This approach was originally described by Rives and Stoppa, and is characterized by opening the rectus sheath and defining the retrorectus plane posterior to the rectus abdominis muscle. The unique characteristics of this repair include the placement of mesh in the well vascularized retrorectus plane. The opening of this plane allows for the medialization and restoration of the linea alba, which results in offloading of tension on the suture line. The posterior fascia is approximated and the mesh is placed anteriorly in the plane between the rectus abdominis muscle and the posterior rectus fascia^[3]. While this was previously exclusively an open approach as originally described, the sublay-retromuscular approach is now being increasingly performed via a minimally invasive approach. These approaches include combined endoscopic/open procedures as described by Schwarz et al.^[7] in the endoscopic mini/less open sublay repair. Additionally, this sublay-retromuscular approach has now been extensively described as the extended totally extraperitoneal repair, and can be performed both laparoscopically and robotically^[8]. Belyansky et al.^[9] reported on this novel approach in 2018 and its advantages, including extraperitoneal suture closure of defects, wide mesh coverage in the sublay-retromuscular position with the use of minimal fixation, and an anecdotal appreciation for decreased pain associated with the repair. The sublay-preperitoneal technique describes mesh placement in the plane behind all of the abdominal wall muscles in front of the peritoneum. This technique is more often performed on the robotic platform, given its technical challenge in a laparoscopic approach^[10]. The sublay-intraperitoneal technique describes mesh placement behind the abdominal wall muscles including the parietal peritoneum^[11]. If done in an open fashion, the mesh is secured posteriorly to the posterior rectus sheath and the parietal peritoneum of the anterior abdominal. In a minimally invasive approach, both laparoscopically and robotically, the hernia sac is identified and its contents reduced. Although the fascial defect is more often closed in the robotic approach, the defect can also be closed in the laparoscopic approach^[12]. Regardless of defect closure, the mesh is then secured in place underlying fascia^[13,14].

Advantages and current data

The topic of mesh selection has been an ongoing debate in the surgical community and will not serve as the focus of this review. However, regardless of mesh selection, the optimal location remains up for debate. Mesh implantation has been reported with both prosthetic and biologic varieties; however, multiple factors such as hospital contracts, surgeon experience, and cost drive the decision for mesh selection^[13,14]. In Sosin et al.’s^[15] 2018 meta-analysis of ventral hernia repairs, 6227 patients undergoing ventral hernia repair with mesh were aggregated in a total of 51 studies. The overall recurrence rate for all comers was 8.9% regardless of location of mesh. Notably, there was a statistically significant difference in recurrent rates that was dependent on the location of mesh. The lowest recurrence rate in this meta-analysis was in mesh placed in the sublay-retromuscular plane, with a 5.8% hernia recurrence rate (P = 0.023). Recurrence rates in the sublay-intraperitoneal and sublay-preperitoneal (summarily referenced as underlay in Sosin et al.’s^[16] metanalysis) mesh placement were 10.9% and 12.9%, respectively. The highest hernia recurrence rate of 21.6% was observed in patients who underwent an inlay mesh placement^[8,9]. Additionally, on repeated meta-analysis performed by Holihan et al.^[16,17], the sublay-retromuscular repair demonstrated a lower risk of recurrence and surgical site infection, when compared to onlay, inlay, and sublay-intraperitoneal or sublay-preperitoneal mesh approaches (range: OR: 0.45-0.79). The sublay-retromuscular repair was given a moderate recommendation of being the best approach when considering recurrence rate and surgical site infections^[16]. When evaluating mesh location specific to synthetic versus biologic mesh placement, these distinctions did not remain. Specifically, in all patients who underwent synthetic mesh placement, mesh location was not a statistically significant predictor for recurrence rates (P = 0.95)^[16].

When evaluating overall complication rates, Sosin et al.’s^[15] review highlights similar overall complication rates observed in ventral hernia repairs, which ranged from 32.6% to 39.1%, regardless of mesh location with no statistically significant difference (P = 0.738). While the onlay approach is generally considered the least technically challenging approach to mesh placement, it has fallen out of favor due to the reported increased wound and mesh infection complications^[18] with approximately 7.6% of hernia repairs as of 2018 being performed in this plane. This is compared to greater than 65% of meshes being placed in the sublay-intraperitoneal, preperitoneal plane, or retromuscular plane in their pooled analysis of reported ventral hernia repairs^[15]. The mean infection rate in the onlay subgroup was 14%. The mean hematoma/seroma complication rate was found to be 17.4%, the highest amongst the four subgroups. However, the differences amongst complications in different mesh planes was not significant. The onlay approach’s largest disadvantage is the mesh’s direct contact with the environment during revision of the wound, which can lead to the subsequent wound complications observed in these studies^[19].

The inlay technique, which requires a bridging mesh, is performed when the fascial defect cannot be closed. Laparoscopic repair was the dominant approach for this mesh placement accounting for 72.6% vs. 27.4% for open repairs. Infection rates in this approach was 12% and mean hematoma/seroma rate was 12.2%, which did not significantly differ among the four techniques. Hernia recurrence was the highest in this subgroup, with a 21.6% hernia recurrence rate. The sublay-retromuscular approach to mesh placement can be achieved both via an open surgical approach or through minimally invasive techniques. The open approach remains the dominant surgical approach in Sosin et al.’s^[15] analysis, with 94% accounting for an open repair. The mean infection rate was 10.4% and mean hematoma/seroma rate was 11%. This subgroup had the lowest rate of hernia recurrence, at only 5.8% (P = 0.023). The closure of the rectus muscles over prosthetic mesh in a well vascularized plane has proven to result in decreased wound infection rates. The sublay-intraperitoneal technique was achieved both laparoscopically (63%) and through an open surgical technique (37%). The mean infection rate in this group was the highest in Sosin et al.’s^[15] analysis, at 17.7%. This compares to only 10.2% in the sublay-retromuscular cohort; however, in this analysis, these were not found to be statistically significant. Mean hematoma/seroma rate was recorded as 11.5%. Hernia recurrence in this group was 10.9%, the second lowest rate based on anatomic mesh placement^[15]. These data are summarized in Table 1. These data corroborate previously reported outcomes by Holihan et al.^[16], who found the lowest odds of developing a surgical site infection in those with a sublay-retromuscular approach (OR: 0.449; 95%CI: 0.12-1.16) when compared to onlay mesh placement. The sublay-intraperitoneal or sublay-preperitoneal was almost double the odds (OR: 0.878; 95%CI: 0.29-1.99). Notably, infection rates are significantly different when evaluating open versus laparoscopic approach. This is demonstrated in Table 2. In Gokcal et al.’s^[10] single institution comparison of robotic preperitoneal and intraperitoneal ventral hernia repair, perioperative outcomes at three months were similar. Extremely short-term outcomes at three weeks demonstrated higher surgical site occurrences in the intraperitoneal cohort when compared to the preperitoneal cohort (14% vs. 5.3%, P = 0.042).

Mesh selection

Mesh selection is a multifaceted dilemma based on what is familiar to the surgeon, what is available to the surgeon based on institutional contracts and cost, and the approach to repair selected. However, at the core of selection are the properties of the mesh and these in general fall into two categories: biologic and synthetic. Similar to the lack of strong consensus on the optimal location for mesh placement, there remains lack of strong consensus on what type of mesh to use. While there is general consensus on the use of a reinforcement material in the management of ventral/incision hernias, the composition of the reinforcement continues to be debated.

Conclusion

Half a million patients undergo ventral hernia repair annually in the United States as a result of incisional hernias, failed repairs, de novo abdominal wall defects, and abdominal catastrophes. Although the standard approach of hernia repair has been well studied, the ideal anatomic location of mesh placement is still highly debated. Sosin et al.’s^[15] systematic review of mesh placement found that anatomic location can change outcomes in hernia recurrence. Analysis of 51 articles showed that, of the four mesh techniques, namely onlay, interposition, sublay-retromuscular, and sublay-preperitoneal/sublay-peritoneal, the sublay-retromuscular approach is associated with the lowest recurrence rate, whereas the interposition technique is associated with the highest recurrence rate. There was no statistical difference in other complication rates among the four groups, which included postoperative infection, hematoma/seroma formation, mesh explantation, and mortality. Overwhelmingly, the inlay placement of mesh is the least favored and should be avoided if possible. In the minimally invasive approach, both robotically and laparoscopically, the sublay-preperitoneal/sublay-intraperitoneal repair has proven very useful with similar perioperative complications and recurrence rates. In regards to mesh selection, in accordance with the recommendations of the VHWG, we recommend that all ventral hernias be reinforced with mesh regardless of whether the midline fascia can be reapproximated^[22]. While strong recommendations for the use of synthetic versus biologic mesh are unclear in patients with VHWG Grades 2 and 3, biologic mesh’s benefit is clear in grossly contaminated wounds and synthetic mesh is recommended in VHWG Grade 1 patients.