Polypropylene material is one of the most commonly used synthetic meshes. It is nonabsorbable and popular for its macroporous structure. It is advantageous because of better fibrovascular ingrowth and immune cell penetration. It also leads to stronger scar formation, creating a more durable apposition with the fascial edge [5]. These meshes create a stiff scar due to the lack of pliability. This can be useful to cover large defects of the abdominal wall where there is little support. The ­macroporous structure also allows for neutrophil and macrophage migration into the mesh, thereby allowing clearance of bacteria [1, 4]. More common complications include mesh extrusion or erosion into bowel.

PTFE/ePTFE (Gore-Tex, W.L. Gore, Newark, DE) is another nonabsorbable mesh. It is stronger than polypropylene but also flexible. The expansion process of PTFE creates a material that is relatively inert when implanted. The small pore size accounts for a minimal foreign body reaction compared to polypropylene and accounts for its advantages and disadvantages [5]. There is less risk of the mesh erosion through the skin or viscera due to its microporous structure and can be placed directly over the exposed bowel. The small pore size does predispose this implant to seroma formation, as this fluid cannot adequately egress through the mesh. Similarly, formation of fluid can increase the risk of abdominal compartment syndrome [6] . It also allows smaller bacteria (1 µ in size) to migrate into the mesh but does not allow entry of inflammatory cells, such as macrophages (greater than 50 µ). This, along with the lack of fibrovascular ingrowth, predisposes the implant to infection , which would ultimately mandate mesh removal.

Alternative options include polyglactin-based meshes (e.g., Vicryl, Ethicon; Dexon, Davis & Geck, Sugarland, TX) which are absorbable. Their primary advantage is use as a temporary solution in grossly contaminated wounds. Polyglactin-based options retain their strength in the short term, have a decreased risk of fistula formation, and allow fluid drainage. They are usually not used for long-term or permanent reinforcement as a result of progressive loss in tensile strength over time.

Composite meshes (e.g., Vypro I/II, Ultrapro, Proceed, Ethicon, Somerville, NJ; Sepramesh and Composix, Bard, Murray Hill, NJ) are also available for repair of abdominal wall defects. The primary advantage of composite meshes is that one side of the mesh prevents adhesions to adjacent bowel, while the other provides strength and support to the abdominal wall. These meshes offer a great option for the abdominal wound with exposed viscera; however, the anti-adhesive layer can develop marginal breakdown, leading to adhesions. Also, the permanent materials in these prostheses can become infected if bacterial seeding occurs.

The major drawbacks to the use of synthetic mesh are infection and seroma formation. Seroma formation is common and is usually the result of extensive dissection and creation of dead space. Seromas of the abdominal wall are typically managed with observation; however, if drainage is necessary, it is imperative to obtain a fluid culture. Observed in large series of laparoscopic ventral hernia repair experience, aspiration of seromas has the risk of introducing bacteria, resulting in infection and the recurrence of the hernia. Usually, expectant management is all that is required. Hematomas can also occur and are treated in the same fashion. Hematomas require treatment if actively bleeding, expanding, or infected.

Infection is the most feared complication and usually necessitates prosthetic explantation. This is most commonly due to surgical wound infection that tracks the underlying mesh, resulting ultimately in mesh extrusion. Every attempt should be made to cover the mesh with well-vascularized tissue to decrease the incidence of these complications.