Abdominal wall hernias are one of the most commonly performed operations in the United States, with over 350,000 operations performed every year. Despite improvements in surgical techniques and technology, the quest for the ideal technique for hernia repair continues. Primary repair of abdominal hernias is associated with a high recurrence rate ranging from 24 to 54% [1–4]. The use of mesh repair, however, has been widely popularized and has replaced primary repairs. Results from a prospective, randomized, multicenter trial in which suture repair was compared with mesh repair demonstrated that mesh repair was more effective and associated with a significantly lower recurrence rate even in patients with small size defects [2]. A significant proportion of ventral hernias are “complex” and the management of these patients remains particularly challenging. With the increasing number of trauma patients undergoing major abdominal procedures and the expanding utility of damage control surgery beyond trauma patients, the need for complex abdominal wall reconstruction appears to be increasing.

The goal for management of patients undergoing complex abdominal wall reconstruction is the restoration of the gastrointestinal continuity and the reconstruction of a strong resistant “neo-abdominal wall.” Classically, a multi-staged approach has been utilized for these patients [3, 4]. In cases of previous operation complicated by infection of the mesh, the initial operation is performed to remove the infectious source. Since the use of synthetic grafts in patients with infected wounds is known to be associated with high re-infection rate, no mesh repair is performed during this stage. Once the infection is cleared, a definitive repair to reconstruct the abdominal wall is performed several months later. This definitive repair requires several techniques and utilizes both native tissue and biologic or synthetic mesh.

The more recent introduction of biologic mesh has shifted the paradigm towards a “single-staged” approach and repair for contaminated abdominal wall hernias [5]. Several studies have demonstrated that biologic mesh is more resistant to infection compared with synthetic mesh. Biologic mesh promotes the ingrowth of neo-vasculature and cells which may be responsible for this resistance [6, 7]. Studies have also demonstrated anti-microbial activity with the use of biologic mesh. Therefore, when the risk of abdominal infection is high, the surgeon may consider the use of biologic mesh in place of a synthetic mesh. In fact, the use of biologic mesh in contaminated fields has now become the standard of care for hernia repair [8, 9]. Repairs with biologic mesh may remain intact even with active infections and do not require removal of the mesh when infected. Another advantage offered by biologic mesh is that these patients can be managed non-surgically even when the wounds become infected [10, 11].

The selection of mesh will be discussed in more detail elsewhere in this book. In this section we will touch briefly. What kind of mesh we should use depends on clinical situation and surgical history of the patient. Suffice to say that the risk of infection is significantly higher with the use of synthetic mesh, particularly, in a contaminated field. Once infected, this requires removal of the infected mesh and may also lead to other complications such as new fistulas. As all hernias with fistulas and stomas are contaminated by default they should only undergo repair with biologic mesh . Several types of biologic mesh exist which can be broadly classified into human derived and porcine derived. There is lack of level I evidence to suggest if one is better than the other in preventing infection or recurrence. We compared the outcomes of human derived and porcine derived acellular dermal matrix at our center over a six-year period. Our series demonstrated a significantly higher hernia recurrence rate of 22.5% for patients with porcine-derived mesh compared with a 2.9% recurrence rate for patients with human derived mesh placement with a mean follow-up time of 16 months. However, there was no difference in the rates of infections, reoperations, or mesh explantation between the two groups. Our data from a small study showed that the overall wound related complication rate in patients undergoing biologic mesh was 29.5% with the most common complication being superficial SSI. In another study, we evaluated the long-term outcomes of 60 patients undergoing complex abdominal wall reconstruction with acellular dermal matrix (Alloderm: 38; Strattice: 18). Of these, 9 patients had concomitant ECF or EAF fistulas. Our study showed that there was no difference in overall complications, infectious complications, or recurrence rates in patients with or without concomitant fistulas. Overall 35 patients had contaminated fields, of which 26 had grade 4 infections.

Our experience suggests that the use of acellular dermal matrix biologic mesh in patients with clean contaminated or dirty wounds is a viable option for a single staged approach to complex abdominal wall reconstruction. Our experience has been mostly limited to Alloderm (human-derived) and Strattice (porcine-derived). Although the recurrence rate has been lower in our experience with Alloderm, this may be due to a selection bias. The overall complications and infectious complications appear to be similar between the two mesh types.

Several techniques exist for the placement of mesh during reconstruction of complex abdominal wall defects and an appropriate technique must be considered to achieve successful outcomes. When choosing between the best anatomic location for mesh placement, the surgeon must consider a number of factors, all of which affect long-term outcomes. First, mesh-tissue integration and greater overlap of mesh and host tissue reduce long-term recurrence. Second, wound complications, such as wound infections, increase the risk of recurrence exponentially. Thus, techniques that do not result in the development of devascularizing flaps, provide tissue coverage, and minimize exposure to the external environment and intra-abdominal contents, should be preferred. The most commonly used techniques in our practice have been underlay, onlay, and bridge mesh placement (see Chap. 7 for illustrations). Other techniques also include the retrorectus approach. Each of these techniques has its pros and cons and the choice of approach should be tailored to the clinical scenario and surgeon’s experience. These techniques can be performed either openly or laparoscopically; however, owing to the complexity of the defects, open surgical approach is more commonly utilized especially in patients with coexisting fistulas.

In this technique, the mesh is placed above the primary fascial closure to provide reinforcement and this may be preferred in certain cases. Once the hernia is repaired and the fascia is closed with non-absorbable continuous or interrupted sutures, the mesh is placed over the anterior rectus sheath and covers it. We prefer fixing the mesh to the fascia using non-absorbable sutures, either interrupted or continuous. An important element of this technique is fixing the mesh both laterally and on each side of midline to reduce the risk of seroma formation under the mesh. We use three to four large, closed-suction drains (19 French) under the subcutaneous tissue and keep them in until the individual drain output is less than 25 mL over a 24 h time period.

The onlay technique is the easiest to perform. This technique prevents contact between the mesh and the underlying abdominal viscera. Despite these advantages, this technique is associated with a high morbidity and recurrence rate [12]. With the onlay technique, skin flaps must be created, which increase the risk of mesh infection and wound complications [13, 14]. For these reasons, this technique is not used very often these days.

In our practice, underlay graft placement has now become the main technique of mesh placement in all high-risk and complex ventral hernia defect reconstruction. It is more involved, but once it is learned and perfected, it does not add significant operative time. In the underlay placement technique, repair material is sutured deep to the primary repair or fascial edges. There are two types of underlay techniques: intraperitoneal underlay technique and the extraperitoneal underlay technique.

The intraperitoneal underlay technique was first described by McCarthy et al. in 1981 [15]. When this technique was introduced, polypropylene mesh was used intraperitoneally; however, the intraperitoneal use of polypropylene mesh caused adhesions to the bowel and was, therefore, abandoned. The use of intraperitoneal polypropylene mesh is also associated with bowel injuries, mesh dislocation, bowel erosions, and the development of enterocutaneous fistulas. Over time, intraperitoneal polypropylene mesh was replaced by the use of a laminar polytetrafluoroethylene (ePTFE) mesh or bilayer composite prosthesis (PTFE and polypropylene) in order to avoid adhesions with the intra-abdominal viscera [16], and eventually by biologic mesh. The key element of this technique is freeing the abdominal wall from any adhesions as far laterally as possible. Placement of sutures can be technically challenging and requires that the sutures be placed close to one another in order to prevent the intra-abdominal contents from sliding and herniating between the mesh and the abdominal wall [14]. Placement of the interrupted sutures should ensure complete stretching of mesh once sutures are tight. Suture placement techniques vary but we use the “parachuting” technique and direct vision at all times [17]. This technique minimizes the potential for bowel injury during fixing of graft on the abdominal wall. If lateral component release is used, we prefer placing sutures in the anterior abdominal wall as far laterally as possible to include the medial edge of the external oblique fascia. Doing so is an important technical step: It prevents bulging laterally at the release component site, and the patient might think bulging is a new hernia [18].

Underlay placement offers several mechanical advantages. When the mesh is placed under abdominal wall, the intra-abdominal pressure presses the mesh against the wall, helping with better incorporation. In contrast, with an onlay mesh placement, increase in intra-abdominal pressure forces the mesh away from the defect therefore increasing the likelihood of recurrence [19]. According to Pascal’s law , any pressure exerted on an enclosed fluid is transmitted equally and undiminished in all directions. Therefore, with an underlay placement as the intra-abdominal pressure increases, equal amounts of force are exerted across the mesh which helps in preventing recurrence [12]. Moreover, an underlay placement also reduces the exposure of mesh to the environment which helps prevent infectious complications. One recent meta-analysis compared the outcomes between onlay and underlay mesh placement and found underlay mesh placement had a lower risk for recurrence [0.59 (0.069–1.504)] and surgical site infection (SSI) [0.878 (0.291–1.985)] compared to onlay [14]. This approach has been regarded as the gold standard for ventral hernia repair by the American Hernia Society [20].