(a) Case of penetrating abdominal injury due to sniper rifle shot . Full thickness midline defect closed temporarily using a mesh which will be covered with a split thickness skin graft once there is adequate granulation tissue. (b) Inset of the meshed split thickness skin graft over the granulated wound bed. Images taken 2 months postoperatively show that the skin graft has taken well. (c) Images taken 1 year after injury post excision of the skin graft and definitive closure of the abdominal wall defect
Stage 2: Abdominal Wall Reconstruction
Optimal timing of abdominal wall reconstruction in blast injury is not straightforward. Composite defects are repaired immediately in a single-stage fashion unless the patient is unstable or there is significant bacterial contamination in the tissue . Immediate reconstruction is preferred because it is more cost-effective and less time-consuming in the medically stable patient with a clean wound bed and reliable reconstructive option . However, in the vast majority of blast injuries, patients are often unstable due to visceral and systemic injuries and may require repeated explorations .
During this period the abdominal contents are protected with alternate methods, such as packs, plastic bags , and VAC dressings. In some patients, when bowel edema and distension subsides, a delayed primary closure can be achieved at between 7 and 10 days . If it is not feasible to approximate the fascial edges at this stage, the wound bed is allowed to granulate and is subsequently covered by a split thickness skin graft . Definitive reconstruction can be planned and performed after a period of at least 6–12 months to give the scars sufficient time to mature as shown in Fig. 12.1c .
Role of Mesh
A mesh can be classified as absorbable or nonabsorbable. Absorbable crafts such as polyglactin (Vicryl and Dexon) are an option for staged reconstruction in the presence of contamination, infection, or compartment syndrome as they are inert and do not elicit antigenic reaction . Nonabsorbable synthetic grafts such as Prolene and Marlex are useful in clean wounds; thus, they are of limited value in the contaminated wounds encountered post abdominal blast injury. New synthetic grafts are made with both absorbable and nonabsorbable components . Bioprosthetics such as human acellular tissue matrix (Alloderm) , porcine acellular matrix , and porcine intestinal submucosa are derivatives of human or animal tissues, which may retain some original properties and allow good integration and remodeling . Bioprosthetic materials are preferred over synthetic materials for use in contaminated fields . However, bioprosthetic materials such as acellular dermal matrix cannot be placed in a grossly infected wound with large amounts of purulence or enteric contents, and even in contaminated wounds, meticulous debridement and generous irrigation still need to be performed .
A mesh can also be classified as meshed or non-meshed. Mesh grafts allow drainage of exudates and in growth of granulation tissue along the edges of the repair .
A mesh may be placed in intraperitoneal plane, anterior to the rectus muscle or posterior to it. Mesh placement is not free of complications, especially the synthetic ones which have an increased risk of infection, bowel adhesions, fistulization, ulceration, and extrusion .
In component separation , the external oblique aponeurosis is released lateral to the linea semilunaris, thus allowing advancement of the rectus abdominis medially while still attached to the internal oblique and transversalis muscles without denervation or devascularization of the abdominal musculature . This technique allows closure even in contaminated fields in which the use of synthetic materials is not recommended .
There have been modifications to this technique such as the minimally invasive component separation which uses tunnel incisions for external oblique aponeurosis release . The main aims of this modified technique is minimizing the subcutaneous dead space that can result from extensive tissue undermining and improving vascularity to the overlying skin by preserving the integrity of the rectus abdominis myocutaneous perforators .
This procedure advances tissues toward the midline for up to 10, 20, and 6 cm in the epigastric, umbilical, and suprapubic regions, respectively . The posterior rectus sheath may also be released to gain additional fascial advancement .
Tissue expansion of the abdominal wall can provide well-vascularized autologous skin, subcutaneous tissue, and/or abdominal fascia for the repair of large defects [26–28]. The tissue expanders can be placed suprafascially, expanding only the skin, or beneath the external oblique aponeurosis, expanding the fascia . However, tissue expansion carries the risks of rupture, extrusion, infection, patient intolerance, and expander failure .
Local and Regional Flaps
Upon planning for abdominal wall reconstruction, it is important to consider the position of the defect, its size, and the abdominal wall layers affected. The abdomen is divided by two horizontal planes into upper, middle, and lower abdominal regions and by two vertical planes into one central third and two lateral thirds. Thus, a defect could be localized into one of six subunits in the abdomen.
For lateral upper abdomen defects , if primary closure of the skin with local tissue is not possible, soft-tissue coverage can be provided with flaps based on the upper trunk (e.g., latissimus dorsi, serratus, thoraco-epigastric flap) . The central upper abdomen remains challenging for the reconstructive surgeon as only the less perfused distal part of trunk-based or thigh-based pedicled flaps tends to reach the upper abdomen .
The iliolumbar flap provides soft tissue coverage in the middle third of the abdomen , while the pedicled anterolateral thigh flap or the pedicled extended deep inferior epigastric artery perforator flap [29, 30] can be used for lower abdominal defects. The workhorse flap which can be used in all these areas is the myo-cutaneous rectus abdominis flap . Those pedicled flaps are useful and adequately address the reconstructive needs of most abdominal wall defects [31, 32]. However, they have certain inherent limitations, such as restricted reach, tip necrosis, limited size of defects that can be covered, and lack of a strong fascial layer within these flaps, except for the pedicled tensor fasciae latae flap, thereby necessitating the need for the use of alloplastic materials or a second donor site for the harvest of the free fascia lata graft .
As for isolated skin and subcutaneous tissue defects:
Defects less than 5 cm may be closed primarily
Defects 5–15 cm in size require local advancement or a split thickness skin graft
Defects more than 15 cm in size, local flaps (random or axial) or tissue expansion after temporary closure with a skin graft are the available options 
Free flaps are required for abdominal wall reconstruction when the defect is too large to be covered by local flaps or when local flaps are unavailable due to the extensive blast injury.
The lateral thigh is our “warehouse” donor site for a variety of reconstructive needs in abdominal wall reconstruction [34–36].
The lateral circumflex femoral system is versatile and allows the harvest of the tensor fasciae latae myocutaneous flap, anterolateral thigh flap, or anteromedial thigh flap either alone or in combination as conjoined flaps . An important advantage of the thigh is the presence of the strong deep fascia in the lateral thigh, including the iliotibial tract and fascia lata that can be used to reconstruct the musculofascial layer of the abdominal wall, thereby preventing postoperative hernia .
The anterolateral thigh fasciocutaneous flap has a large skin paddle extending from the level of the greater trochanter to just above the patella and it is supplied by the lateral femoral circumflex artery descending branch . Another option for free tissue transfer is the tensor fascia lata flap which is based on the transverse branch of the lateral femoral circumflex artery. When larger flaps are needed, adjacent flaps can be harvested together in a conjoined manner [37–39]. The tensor fasciae latae and the anterolateral thigh with or without the vastus lateralis muscle based on the lateral circumflex femoral artery system are prime examples of this .