Keywords

These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

FormalPara Highlights

  • No definitive evidences exist on the biological prosthesis in abdominal wall reconstruction after open abdomen; dedicated studies are needed.

  • Biological prosthesis seems to be a valid option for abdominal wall repair minimizing mesh-related complications, especially in contaminated surgical fields.

  • In managing great abdominal wall defects, the positioning of a biological prosthesis as a bridge to close the abdomen seems to be the best and most obvious solution to solve the acute problem.

  • Biological prosthesis seems to be associated with a high rate of hernia recurrence in long-term follow-up.

20.1 Introduction

Early definitive closure is an important goal in open abdomen treatment; there are some evidences showing better outcomes associated with early closure [1]. Primary fascial closure is the ideal solution to restore the abdominal closure, but sometimes the open treatment, particularly if prolonged, results in fascial retraction consequently in large abdominal wall defects that require complex abdominal wall reconstruction. Moreover the situation is often complicated by a contaminated surgical field with high risk of infections and wound complications, such as wound infections, seromas, fistula formation, recurrence of the defect, and mortality [2, 3]. Primary fascial closure failure in open abdomen has been reported ranging from 22 to 39% in a meta-analysis [4].

For these complex and troublesome situations, several techniques have been proposed and discussed comprehending the component separation techniques, flaps transpositions, and mesh repair. The abdominal wall defect that could result from an open abdomen treatment could be treated and managed with the aforementioned different techniques and with different timings. Depending on the center and surgeon’s preference and expertise, combined with patient’s conditions, open abdomen could result even in a planned ventral hernia, allowing the wound to granulate with or without skin grafting for the immediate closure and with a later planned abdominal wall reconstruction.

The aim of the present chapter is to give an overview of the use of biologic mesh in abdominal wall’s reconstruction after open abdomen treatment, both in immediate “acute mesh repair” or in delayed planned ventral hernia repair.

20.2 The Rationale

Open abdomen, above all if prolonged, may result in fascial retraction and abdominal wall defects. The fascial defect could be closed with a mesh as a bridge. The main used nonabsorbable synthetic materials (i.e., polypropylene mesh) reinforce the fascial repair by a combination of mechanical tension and intense inflammatory reaction, resulting in the entrapment of the mesh into scar tissue. However synthetic meshes are generally not recommended on such situations [5]. The persistent inflammatory response may induce local side effects such as adhesions, erosions, and fistula formation, particularly when mesh is directly in contact with viscera [6,7,8]. Moreover in the presence of bacterial contamination, their use could result in a larger number of complications such as mesh infection and the need for mesh removal with related morbidity and mortality [9]. Among difficulties in the management of the open abdomen, there is the bacterial contamination. A recent paper reported that almost 80% of the patients with open treatment had a positive bacterial and fungal culture from the abdominal cavity [10]. All bacteria, whether in an acute or chronic wound or in a contaminated versus a colonized wound, produce virulence factors (e.g., exotoxins, endotoxins), with deleterious effects to wound healing [11, 12].

Because of the limitations of nonabsorbable synthetic meshes, surgeons have started to explore the use of biological materials in abdominal wall reconstruction. Biological prosthesis has been designed to perform as permanent surgical prosthesis in abdominal wall repair, minimizing mesh-related complications. There are several types of biological materials, derived from allogenic or xenogenic tissue, such as bovine pericardium, human cadaveric dermis, porcine small intestine submucosa, porcine dermal collagen, and bovine dermal collagen. For each material, several treatments are processed in order to remove hair, cells, cell components, and antigens present in the tissue, leaving only a highly organized collagen scaffold with the surrounding extracellular ground tissue [13]. After the implantation, biological responses lead to implant degradation and resorption with tissue remodeling in which the implanted material is repopulated by local fibroblasts and a new vasculature that together support the generation of a new, metabolically active, strong tissue [14].

The rationale of their usage in open abdomen is that the implantation of a biological material triggers a cascade of events leading to a new healthy tissue deposition and prosthesis remodeling. One of the most important aspects is that the collagen scaffold, repopulated with new tissue and blood vessels, allows blood, growth and pro-/anti-inflammatory factors, and drugs to reach the surgical field during the first phases of healing process. The presence of vital tissue allows therefore preventing mesh infection and abscess formations, maintaining mechanical characteristics of a synthetic mesh with a sufficient mechanical strength to withstand the physiological and anatomic stresses of the human abdominal wall.

20.3 Prosthesis Choice and Position

Natural cross-links exist in native collagen, and their function is to stabilize the structure of the collagenic proteins, giving mechanical strength and protection from collagenase. Biomaterials, during the preparation phase, could be treated with the use of chemical cross-linking agents modulating the characteristics of the prosthesis and giving additional strength to the collagen scaffold. The presence of cross-links between the collagen chains seems to further reduce the bacterial and host collagenase enzymes activity, slowing the degradation process of the prostheses. Therefore cross-linked prosthesis is partially remodeling, whereas non-cross-linked prosthesis is completely remodeling. Despite each prosthesis which permits and encourages host tissue ingrowth, the differences in remodeling times should be kept in mind when considering the choice of the best prosthesis. Even though it has been demonstrated in animal models that the tensile strength is different between cross-linked and non-cross-linked meshes during the first months after the implant, both type of materials show similar values after 12 months with no changes over time in the strength of the repair sites [9, 15,16,17]. The choice of biological materials in contaminated fields is recommended by the Ventral Hernia Working Group and the WSES guidelines on emergency abdominal wall repair [5, 18]. In literature a decisional model proposed by “The Italian Biological Prosthesis Work Group (IBPWG)” is available also in order to standardize and to facilitate the choice between the different types of BP [19]. The proposed model combines the tissue loss’ dimension and the contamination of the surgical field resulting in a score that indicates the necessity to use either a cross-linked or a non-cross-linked BP (Table 20.1, Figs. 20.1 and 20.2).

Table 20.1 IBPWG score = infection score × tissue loss score
Full size table
Fig. 20.1
figure 1

Decisional diagram of IBPWG based on infection and tissue loss. Reproduced with permission from [20]

Full size image
Fig. 20.2
figure 2

Decisional model based on IBPWG score (on the x-axis) (Reproduced with permission from [20])

Full size image

No good quality data exists on prosthesis position in closure of the abdominal wall. Moreover available evidences evaluate each prosthesis’ position combined with various and heterogeneous prosthesis (synthetic and biological) in heterogeneous patients. A recent retrospective study on porcine cross-linked dermal prosthesis with a long follow-up showed better results with sublay position compared with onlay (2.4 versus 18.9% recurrence, p < 0.0001), but data were not specific on an open abdomen [21]. Two meta-analysis confirmed that the sublay position results in a lower infection rate and recurrence rate compared to onlay, inlay, and underlay [20, 22], but it should be stressed that included data were not specific on biological prosthesis and open abdomen and the heterogeneity among patients and indications was very high, giving a poor level of evidence.

Discordant data have been published about the use of BP to bridge wide defect of the abdominal wall. Few studies, nonrandomized, and with small number of cases and heterogeneous patients, have been published reporting recurrence rate ranging between 0 and 100% [15, 16, 23,24,25].

In closing the open abdomen, the mesh is often required not only to reinforce the abdominal wall and to prevent incisional hernia but also as a bridge to close the absent/retracted fascia. No studies dedicated specially on this issue are available in literature right now, and data could be only extrapolated from larger studies. A large study on the use of acellular porcine dermal collagen in hernia with high risk for infections reported an overall recurrence rate of 66% [26]. When the meshes were positioned as a bridge, the reported recurrence rate was >80%. A study by Booth and colleague compared primary fascial closure with mesh reinforcement with the use of the mesh as a bridge and demonstrated a higher recurrence rate (56% versus 8%, p < 0.001) [25]. A randomized controlled trial compared the traditional bridged mesh repair (with both synthetic and biologic meshes) with the component separation technique with biologic mesh reinforcement [27]: the trial demonstrated that recurrences were lower with the component separation plus mesh reinforcement technique (13.2 versus 37.5%, p = 0.02). Component separation plus reinforcement was also associated with a lower infection rate (0 versus 23% in the bridged group, p = 0.002), but it should be noticed that in the traditional bridged mesh repair group, synthetic meshes were also included and all the infective events occurred within this subgroup.

20.4 Results

As aforementioned lots of studies about the use of biological prosthesis in abdominal wall reconstruction exist in literature with different and contrasting results [24, 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44]. A great lack of evidence exists on the long-term results. A retrospective study by Rosen et al. [45] included 128 patients with ventral hernia and a contaminated field treated with a biological prosthesis. They showed a rate of complicated wound of 47%, and they demonstrated a recurrence rate of 31% after a mean follow-up of 21 months. Great limitations of the study were the utilization of different kinds of prostheses in different positions (inlay, onlay, etc.) and with the combination of the component separation technique.

A meta-analysis of 2012 reported data with a comparison among different types of meshes [46]: the recurrence rate was similar for cross-linked and non-cross-linked porcine dermis (10% versus 8%) but was significantly higher for allogenic human dermis (recurrence rate 20%). Wound complications were similar among the three different types of meshes.

A systematic review by Bellows et al. [47] reported data of 1212 patients. With a mean follow-up of 13 months, the reported weighted recurrence rate was 15.2%. Among the complications, postoperative infection and seroma were the most common with a weighted incidence of 16.9% and 12%, respectively. The removal of the prosthesis was reported in 2% of the cases due to poor mesh incorporation in the majority of cases. Cross-linked porcine meshes result in similar recurrence rate (11% versus 10%) and lower infection rate (9% versus 18%) compared to non-cross-linked meshes.

A meta-analysis by Lee et al. [36] investigated biologic meshes compared with synthetic meshes in abdominal wall reinforcement in contaminated fields. Short-term results as wound infection, prosthetic explantation, and enterocutaneous fistula were comparable in the two groups; biologic meshes were associated with a higher incidence of hernia at follow-up.

A recent meta-analysis by Sharrock and colleagues investigated the management and closure of open abdomen in trauma patients [48]. Among the included studies, the point estimate recurrence rate of ventral hernia after 1 year of biologic mesh positioning was 51%. However, the authors highlighted the small number of included studies and their poor quality, suggesting great caution in interpreting this result.

A systematic review and meta-analysis by Atema et al. [49] investigated the utilization of biological material in abdominal wall reconstruction; the poor quantity and quality of available data strongly limits the results. Biological materials in infected fields had a recurrent hernia rate of 30% compared with 7% of synthetic materials, but data were derived from a single study and do not justify the use of synthetic materials, especially as a bridge position after open abdomen.

Available evidences are really weak: all the cited meta-analysis included especially poor-quality retrospective case series. There is also a great heterogeneity among indications for mesh implantation, mesh position, and type of mesh. This further weakens the quality of the evidences. Actually there is no randomized trial comparing different types of meshes or the indication to mesh positioning. Moreover no good quality comparative studies dedicated on closure of open abdomen are available. Several randomized controlled trials are ongoing to assess the safety and long-term results of biological prosthesis in abdominal wall reconstruction even if none of them is dedicated exclusively to open abdomen [50,51,52,53,54,55,56,57,58].

Conclusion

No definitive evidence-based conclusions could be obtained right now from the literature, and no clear indications in specific situations could be defined for the use of biological prosthesis in abdominal wall repair. Biological prostheses have been designed to perform as a valid option for abdominal wall repair minimizing mesh-related complications, especially in contaminated surgical fields. In managing great abdominal wall defects, especially after open abdomen, biological prosthesis are a fundamental part of the armamentarium of our surgical practice and remains “the only option” in some troublesome situations despite the lack of robust evidences. The need for consensus on the role of biologic mesh in abdominal wall reconstruction is evident. Randomized trials are difficult to conduct, especially in open abdomen, and so prospective studies or large registries are needed with uniform definitions and inclusion. At the moment, the positioning of a biological prosthesis as a bridge to close the abdomen seems to be the best and most obvious solution to solve the acute problem, keeping in mind the possibility to hernia recurrence in long-term follow-up.