Abdominal Wall Reconstruction

The management of complex abdominal wall defects has challenged both general surgeons and reconstructive surgeons since the turn of the last century. Formerly the domain of the general surgeon, the increasing complexity of abdominal wall defects and the development of techniques involving manipulation and mobilization of muscle and myocutaneous flaps have drawn on the expertise of the plastic surgeon. Regardless of the surgeon’s background, the goals of the reconstructive surgeon in managing complex abdominal wall defects are to restore the structural and functional continuity of the musculofascial system and to provide stable and durable wound coverage.

Prior to discussing an approach to repair, it is helpful to appreciate the magnitude of the problem posed by incisional hernias and other abdominal wall defects. From 2008-2009, approximately 381,000 cases of incisional hernia repair were reported, with an expected increase in case volume of 1-2% annually.[1] This increase has been attributed to the growing age of the population, increasing rates of obesity and diabetes, improved survival from intra-abdominal cancers, and improvements in care of the critically injured patient, yielding greater survival of patients following abdominal catastrophe. These factors have produced a large subset of medically complicated patients with structurally complex abdominal wall defects.

Prompted by the increasing complexity of the ventral hernia patient, interest in understanding the pathophysiology for hernia formation has increased. Likewise, surgical techniques have evolved to emphasize restoration of abdominal wall function as well as structure. Abdominal wall defects are no longer characterized as “holes,” but as chronic wounds that result in a complex neuromuscular deformity. Clinical and animal studies exploring the mechanisms underlying hernia formation have implicated both mechanical and biologic factors. Preclinical studies exploring the biology of hernia formation have demonstrated a preponderance and persistence of type III collagen in laparotomy wounds that go on to develop hernias. While type III collagen is found in the provisional matrix of a healing wound, it is the failure of this type III collagen to be replaced by mature type I collagen that has led many to consider a hernia a “chronic wound.”

Supporting the biologic etiology of hernia formation are preclinical studies that demonstrate divergent genetic patterns displayed by laparotomy wounds that heal and those that herniate. This is also consistent with the recognition of aneurysmal disease and connective-tissue disorders as significant risk factors for hernia formation.[2]

From a mechanical standpoint, greater understanding of the abdominal wall as a dynamic musculotendinous structure has led to characterization of a laparotomy incision within the linea alba as a tendon injury, akin to laceration of an upper extremity tendon. The laparotomy, as tenotomy, leads to myocyte replacement with fibrotic connective tissue and disordered arrangement of sarcomere structure, manifesting as a decrease in abdominal wall compliance that predisposes the abdominal wall to further injury.

The concept of optimal tension has also been extrapolated from the hand surgery literature and applied to an understanding of hernia biology. The resulting shift from a “tension-free repair” to a repair under “physiologic tension” has led to changes in surgical technique, with a greater preference for lighter-weight prosthetic materials and more widespread use of components separation, a procedure designed to improve abdominal wall compliance.

The abdominal wall serves to protect the abdominal organs, maintain upright posture and support the spine, and assist in bodily functions that require generation of Valsalva, such as coughing, urination, or defecation. There is also a suggestion that the absence of an intact abdominal wall results in loss of the mechanical endpoint of satiety, leading to unintentional weight gain. Indications for reconstruction can be both symptomatic and structural, with goals ranging from pain relief to prevention of incarceration. That said, while large abdominal wall defects can be plagued by significant herniation of intra-abdominal contents, the size of the fascial defect puts them at low risk for incarceration. Defects that ultimately require reconstruction may stem from trauma, tumor extirpation, previous abdominal procedures, and surgical management of severe infection.

The rate of incisional hernia following celiotomy ranges from 3-20%. Factors associated with the formation of an incisional hernia include wound infection, immunosuppression, malnutrition, morbid obesity, previous abdominal operation, patient age, and medical conditions (eg, prostatism) that may cause an increase in intra-abdominal pressure postoperatively.[3] Other biologic risk factors that have become known in recent years include connective-tissue disorders such as Ehlers-Danlos syndrome, a history or family history of aneurysmal disease, or lathyrism, an acquired inhibition of collagen cross-linking due to a diet high in certain legumes (eg, chick peas).[4]

Of the various benign tumors that develop within the abdominal wall, desmoid tumors are the most common. These lesions are histologically benign but locally invasive. Treatment consists of full-thickness abdominal wall resection. Local recurrence rates remain approximately 40%, and it usually occurs within 2 years, despite aggressive treatment. Adjuvant radiotherapy may be required when margins are inadequate.[5]

Treatment of malignant tumors of the abdominal wall requires aggressive resection of involved skin and subcutaneous tissue, as well as the myofascial component if it is violated by the tumor. Sarcomas are the most common and require both aggressive resection and radiotherapy. Intra-abdominal tumors can also involve the abdominal wall, either from contiguous or hematogenous spread. Reconstruction of the abdominal wall in these cases is usually directed by the extent of resection and the possibility of further surgical intervention (see case example images below).

Abdominal wall defects associated with traumatic abdominal injuries are commonly a result of penetrating injury. These abdominal wounds may be grossly contaminated from simultaneous bowel injuries and require delayed reconstruction in multiple stages.

Abdominal wall soft tissue infections are rare except as a complication of a prior mesh repair of abdominal fascia. However, cases of necrotizing fasciitis following inadvertent bowel injury during abdominal liposuction have been reported. Abdominal wall mesh infections commonly present as draining sinuses over the abdomen. Mesh infections are resistant to wound care and antibiotics. Often, successful treatment of the abdominal infection requires removal of the infected mesh and staged abdominal reconstruction.

Regardless of the indication for repair, it is important to have clearly defined goals and objectives when proceeding with abdominal wall reconstruction. In some cases, the complexity or contaminated nature of the case may preclude definitive reconstruction in a single stage. In these situations, it may be prudent to cover or close the wound first, and defer management of the fascial defect until the patient’s status and operative conditions can be optimized. Attempts to treat both the wound and the fascial defect simultaneously may compromise the durability of the fascial repair or unnecessarily predispose the patient to complications such as infection or fistula formation.

Anterior abdominal wall anatomy

The anatomical layers of the abdominal wall include skin, subcutaneous tissue, superficial fascia, deep fascia, muscle, extraperitoneal fascia, and peritoneum. This anatomy may vary with respect to the different topographic regions of the abdomen. The major source of structural integrity and strength of the abdominal wall is provided by the musculofascial layer. The main paired abdominal muscles include the external oblique muscles, internal oblique muscles, transversus abdominis muscles, and rectus abdominis muscles and their respective aponeuroses, which are interdigitated with each other, and provide core strength and protection to the abdominal wall viscera. The integrity of the abdominal wall is essential not only to protect the visceral structures but also to stabilize the trunk and to aid trunk movement and posture.

Skeletal system

Early 19th century anatomist August Rauber described the large gap in the skeletal system between the lower edges of the thorax and the upper edge of the pelvis as the lacuna sceleti sternopubica. This gap is closed by the abdominal muscles and their aponeuroses. The skeletal system, which is relatively fixed, provides attachment points for the soft tissue and muscles of the abdominal wall. The skeletal anatomy of the abdomen consists of the xiphoid process, the costal cartilages of ribs 7-10, the floating ribs 11 and 12, the L1-L5 vertebrae, the iliac crests, the anterior superior iliac spine (ASIS), the pubic tubercle/pubic crest, and the pubic symphysis. The abdominal wall musculoaponeurotic structure is attached to the ribs superiorly, the bones of the pelvis inferiorly, and the vertebral column posteriorly.

Superficial fascia

The superficial fascia of the abdominal wall is divided into a superficial and a deep layer. It may be as thin as half an inch or less or as thick as 6 inches or more. Above the umbilicus, the superficial fascia consists of a single layer. Below the umbilicus, the fascia divides into 2 layers: the Camper fascia (a superficial fatty layer) and the Scarpa fascia (a deep membranous layer). The superficial epigastric neurovascular bundle is located between these 2 layers. The abdominal subcutaneous fat, which is separated by the Scarpa fascia, is highly variable in thickness. The clinical relevance of this anatomy is appreciated when designing superficial inferior epigastric artery (SIEA) flaps. The SIEA flap has been used as a pedicled flap for hand reconstruction or as a free flap in breast reconstruction.

Deep fascia

The deep fascia is a thin, tough layer that surrounds and is adherent to the underlying abdominal muscles. Each abdominal muscle has an aponeurotic component that contributes to the deep fascia. The individual abdominal muscles are described below.

Subserous and peritoneal fascia

The subserous fascia is also known as extraperitoneal fascia and serves to bind the peritoneum to the deep fascia of the abdominal wall or to the outer lining of the gastrointestinal tract. It may receive different names depending on its location (eg, transversalis fascia when it is deep to that muscle, psoas fascia when it is next to that muscle, iliac fascia). The peritoneum is a thin (one-cell thick) membrane that lines the abdominal cavity. It is useful in reconstructive efforts because it provides a layer between the bowel and mesh. In addition, studies have demonstrated the utility of the thin, pliable, peritoneal-lined rectus flap in vaginal wall reconstructions.

Musculofascial layer

The abdominal wall includes 5 paired muscles (3 flat muscles, 2 vertical muscles). The 3 flat muscles are the external oblique, internal oblique, and transversus abdominis. The 3-layered structure, combined with extensive aponeuroses, works in a synkinetic fashion not only to protect the abdominal viscera but also to increase abdominal pressure, which facilitates defecation, micturition, and parturition. The 2 vertical muscles are the rectus abdominis and pyramidalis. Fusion of the fascial layers of these muscles forms 3 distinct fascial lines: the linea alba and 2 semilunar lines. The linea alba is formed by the fusion of both rectus sheaths at the midline, while the semilunar lines are formed by the union of the external oblique, internal oblique, and transversus abdominis aponeuroses at the lateral borders of the rectus abdominis muscles.

External oblique

The external oblique muscle is the largest and thickest of the flat abdominal wall muscles. It originates from the lower 8 ribs, interlocks with slips of latissimus dorsi and serratus anterior, and courses inferior-medially, attaching via its aponeurosis centrally at the linea alba. Inferiorly, the external oblique aponeurosis folds back on itself and forms the inguinal ligament between the ASIS and the pubic tubercle. Medial to the pubic tubercle, the external oblique aponeurosis is attached to the pubic crest. Traveling superior to the medial part of the inguinal ligament, an opening in the aponeurosis forms the superficial inguinal ring. The innervation to the external oblique is derived from the lower 6 thoracic anterior primary rami and the first and second lumbar anterior primary rami.

Internal oblique

The internal oblique muscle originates from the anterior portion of the iliac crest, lateral half to two-thirds of the inguinal ligament, and posterior aponeurosis of the transversus abdominis muscle. The internal oblique fibers run superior-anteriorly at right angles to the external oblique and insert on the cartilages of the lower 4 ribs. The anterior fibers become aponeurotic at around the ninth costal cartilage.

At the lateral border of the rectus abdominis muscle and above the arcuate line, the aponeurosis splits anteriorly and posteriorly to enclose the rectus muscle to help form the rectus sheaths. However, below the arcuate line, the internal oblique aponeurosis does not split, resulting in an absent posterior rectus sheath. The inferior aponeurotic fibers arch over the spermatic cord, pass through the inguinal canal and then descend posterior to the superficial ring to attach to the pubic crest. The most inferior medial tendinous fibers fuse with the aponeurotic fibers of the transversus abdominis muscle to form the conjoint tendon, which also inserts on the pubic crest.

Transversus abdominis

The transversus abdominis muscle is the innermost of the 3 flat abdominal muscles. The fibers of the transversus abdominis course predominantly in a horizontal orientation. It has 2 fleshy origins and 1 aponeurotic origin. The first fleshy origin is from the anterior three fourths of the iliac crest and lateral third of the inguinal ligament, while the second origin is from the inner surface of the lower 6 costal cartilages where they interdigitate with fibers of the diaphragm. Between the 2 fleshy origins is the aponeurotic origin from the transverse processes of the lumbar vertebrae. These fibers course medially to the lateral border of the rectus muscle. From about 6.6 cm inferior to the xiphoid process to the arcuate line, the insertion is aponeurotic and contributes to the formation of the posterior rectus sheath.

Rectus abdominis

The rectus abdominis muscles are paired, long, straplike muscles that are the principal vertical muscles of the anterior abdominal wall. The rectus abdominis is interrupted throughout its length by 3-4 tendinous inscriptions, all of which are adherent to the anterior rectus sheath and separated by the linea alba. These inscriptions can be visualized externally in a well-developed individual secondary to fasciocutaneous ligaments.

The medial tendon of the rectus abdominis originates from the pubic symphysis and the lateral tendon of the rectus abdominis originates from the pubic crest. It inserts to the anterior surfaces of the fifth, sixth, and seventh costal cartilages and xiphoid process. The lateral border of each rectus muscle and its sheath merge with the aponeurosis of the external oblique to form the linea semilunaris. The rectus abdominis muscle functions as a tensor of the abdominal wall and flexor of the vertebrae. Additionally, this muscle helps to stabilize the pelvis during walking, protects the abdominal viscera, and aids in forced expiration.

The rectus sheath is a strong, semifibrous compartment that houses the rectus muscles, the superior and inferior epigastric vessels, and the inferior 5 intercostal and subcostal nerves. It is formed by interlacing aponeurotic fibers from the 3 flat abdominal muscles. The anterior rectus sheath is the union of the external oblique aponeurosis and the anterior layer of the internal oblique. The posterior rectus sheath is composed of the posterior layer of the internal oblique aponeurosis, the transversus abdominis aponeurosis, and the transversalis fascia. Superior to the costal margin, the posterior rectus sheath is absent because the internal oblique muscle is attached to the costal margin and the transversus abdominis courses internal to the costal cartilages.

Pyramidalis

The pyramidalis is a small triangular muscle located anterior to the inferior aspect of the rectus abdominis; the pyramidalis is absent in about 20% of the population. The pyramidalis originates from the body of the pubis directly inferior to the insertion of the rectus abdominis and inserts into the linea alba inferior to the umbilicus to assist in stabilization of the lower midline.

Arcuate line

Above the arcuate line, the anterior rectus fascia exists anterior to the rectus muscle, and the posterior rectus fascia is posterior to the rectus muscle. Below the arcuate line, the 3 aponeuroses merge together to form exclusively the anterior rectus sheath, with little or no posterior sheath. The arcuate line is generally located 2 fingerbreadths from the umbilicus to midway between the umbilicus and pubis. However, some reports in the literature state that the arcuate line is closer to 75% of the distance between the pubic crest and the umbilicus or 1.8 cm superior to the ASIS.

Linea alba

The linea alba is the fusion of the anterior and posterior rectus fascia; it is located in the abdominal midline, between the rectus muscles, from the xiphoid to the pubis. The linea alba is a 3-dimensional composition of tendon fibers from abdominal wall muscles. Midline insertions of these fibers play a significant role in stabilizing the abdominal wall. The cranial aspect is attached to the xiphoid process, while, caudally, it inserts at the pubic symphysis.

Linea semilunaris

The linea semilunares can be seen as a pair of linear impressions in the skin that correspond with the most lateral edges of the rectus abdominis. These lines are visible in a person who is physically fit but obscured in a person who is obese. They are formed by the band of aponeuroses of the external oblique, the internal oblique, and the transversus abdominis muscles.

Vascular supply and innervation

The plane between the internal oblique muscle and transversus abdominis muscle contains the neurovascular structures that supply the abdominal muscles. The superior and inferior deep epigastric vessels enter the rectus muscle superiorly and inferiorly. Transperitoneal vessels enter the rectus in the periumbilical region. The abdominal wall receives its blood supply from direct cutaneous vessels and musculocutaneous perforating vessels.[6] The 2 subdivisions of perforators course medially and laterally. The lateral branch is usually the dominant branch and contains most of the perforator vessels.[7] The lateral fasciocutaneous perforators pierce the aponeuroses of the internal and external oblique muscles. They may pass through the linea alba and emerge on the lateral aspect of the rectus abdominis.[8, 9]

El-Mrakby et al performed microdissections to analyze the vascular anatomy of the anterior abdominal wall. They concluded that the musculocutaneous perforators are the main providers of blood supply to the anterior abdominal wall.[10] In addition, the vessels were further categorized into large (direct) or small (indirect) perforators. The indirect perforators generally have diameters less than 0.5 mm and terminate in the deep layer of the subcutaneous fat.[10] Conversely, the direct perforators have diameters greater than 0.5 mm and course into the subdermal plexus to supply the superficial subcutaneous fat and skin.[10] In addition, El-Mrakby et al described the area lateral and inferior to the umbilicus as the area with the richest concentration of perforator vessels.[11] This vascular network allows multiple flap designs that may incorporate one or several perforator vessels.

A study by Huger et al classified the vascular blood supply of the abdominal wall into 3 simple zones for abdominoplasty.[12]

Zone I is defined by the mid abdomen and is supplied primarily by the deep epigastric arcade. As the internal thoracic artery passes behind the costal cartilages to enter the abdominal wall, it gives rise to the superior epigastric artery. This vessel then enters the abdomen and travels underneath the surface of the posterior rectus sheath. The superior epigastric artery joins the deep inferior epigastric artery through a series of choke vessels within the rectus above the umbilicus.

Zone II is defined by the lower abdomen and is supplied by branches of the epigastric arcade and the external iliac artery. Blood supply superficial to the fascia is provided by the superficial epigastric and superficial pudendal arteries. Both of these arteries originate from the femoral artery. The deep iliac circumflex artery originates from the external iliac and runs deep to all abdominal muscles to provide blood supply to the area of the anterior iliac spine; it also pierces all 3 muscles of the lateral abdominal wall and provides a sizable musculocutaneous perforator.

Zone III comprises the flanks and lateral abdomen. Blood supply to this area comes from the intercostal, subcostal, and lumbar arteries. The intercostal vessels leave the rib cage and enter the abdominal wall between the transversus abdominis and internal oblique muscles, where they anastomose with the lateral branches of the superior epigastric artery and deep inferior epigastric artery.

Sensory innervation to the abdomen is derived from the roots of the nerves T7 to L4. These nerves travel in the plane between the internal oblique and transversus abdominis muscles. Motor innervation is provided by the intercostal, subcostal, iliohypogastric, and ilioinguinal nerves. These nerves must be preserved during abdominal wall reconstruction in order to maintain abdominal wall sensation and muscular function.

See Regions and Planes of the Abdomen for more information.

True contraindications to hernia repair are rare. A subset of minimally symptomatic or asymptomatic patients with very large hernias at very low risk for incarceration may benefit from observation rather than attempted repair. Additionally, in some patients, the cardiopulmonary stress or bleeding risk associated with major surgery may preclude operative management of their abdominal wall defect. Given the risk factors associated with the development of a ventral hernia, many of the potential candidates for repair have significant medical comorbidities. It is incumbent on the reconstructive surgeon to maintain an awareness of these comorbid conditions, as well as the alterations in physiology caused by the hernia defect or its repair.

Patients with conditions such as chronic obstructive pulmonary disease (COPD), heart disease, or liver failure must be preoperatively screened. Postoperatively, patients with COPD may be difficult or impossible to wean from the ventilator. Intra-abdominal operations involve large fluid shifts and may cause significant cardiovascular stress intraoperatively and postoperatively, with intravascular return of third space volume in the early postoperative period. In addition, patients with liver failure have high morbidity and mortality rates with operations that require general anesthesia and should not undergo elective abdominal wall reconstruction. The risk of such a major operation for patients with the above comorbid conditions must be defined, as these risks may outweigh the benefit of abdominal wall reconstruction.

Relative contraindications to elective abdominal wall reconstruction/ventral hernia repair include preexisting conditions that may increase the risk of recurrence (ie, smoking, mild COPD, obesity, diabetes, ascites, cancer, multiple hernia recurrences, a noncompliant patient). For more information on these conditions, visit the following Medscape Resource Centers: Smoking, COPD, and Diabetes.

Preoperative preparation

Preoperative preparation for abdominal wall reconstruction, as with any other surgical procedure, involves a thorough patient history and physical examination. Appropriate laboratory studies should be reviewed, as well as chest radiographs and ECG for patients older than 35 years. Furthermore, patients with a history of pulmonary problems such as COPD should undergo pulmonary function tests and a baseline arterial blood gas analysis. Patients with a history of diabetes or chest pain should undergo an appropriate cardiac risk evaluation with ECG and stress testing.

Once the decision has been made to proceed with operative intervention, it is advantageous for the patient to receive a bowel preparation, both in case of enterotomy during repair as well as for simple decompression of the bowel to facilitate manipulation and closure. For most ventral hernia repairs, preoperative imaging should be obtained to assist in surgical planning. A CT scan (with oral contrast) assists in determining the size and location of fascial defects, as a clinically evident bulge may not always be representative of the size and location of the fascial defect. Moreover, in the patient presenting for reoperation following hernia recurrence, preoperative imaging allows the surgeon to determine the location of any previously placed prosthetic material and associated scarring. Finally, in patients with complicated abdominal histories including ostomies and/or dysmotile bowel, preoperative CT scans may be invaluable in coordinating bowel procedures with abdominal wall reconstruction.

In the perioperative period, patients should receive prophylactic antibiotics and mechanical and pharmacologic prophylaxis for venous thromboembolic (VTE) disease. Consideration should be given to preoperative pharmacologic VTE prophylaxis in patients defined as high risk by the American College of Chest Physicians.[13]

Preoperative considerations

The initial assessment of a patient with a complex abdominal wall defect should focus on which structures are present, absent, or distorted with respect to each anatomical layer of the abdominal wall. Previous scars should be taken into consideration during preoperative planning. Incision design and knowledge of the vascular supply to the skin and soft tissue can be crucial, particularly in patients who have had multiple abdominal procedures. For example, a paucity of well-vascularized skin and subcutaneous tissue may jeopardize the reconstructive outcome. This becomes particularly important if prosthetic material is required to replace or reinforce an area of the musculofascial layer. Patients with actively infected wounds and/or systemic infections are poor candidates for reconstruction with prosthetic materials.

The importance of an accurate assessment of postoperative infection risk is highlighted by pay-for-performance initiatives being proposed at all levels of healthcare reform. These reform measures would withhold or refuse reimbursement for complication-related re-admission in the early postoperative period. Increased 30-day re-admission rates were observed in patients with multiple prior abdominal operations, active infection at the time of repair, and the presence of an enterocutaneous fistula. With regard to wound infections, COPD, steroid use, smoking, low preoperative serum albumin (< 2), and coronary artery disease have all been shown to be independent risk factors for the development of a postoperative wound infection. Wound infections not only increase patient discomfort, healthcare costs, and rates of re-admission, they have also been associated with significantly higher rates of long-term hernia recurrence.[14]

In an attempt to assist the reconstructive surgeon in better defining preoperative risk, the Ventral Hernia Working Group stratified cases into a 4-tier grading system based on risk of developing a surgical site complication (see figure below). Technique and material preferences varied based on case grade, with the Ventral Hernia Working Group expressing a stronger preference for bioprosthetic materials with increasing case grade and ultimately recommending staged or delayed repair in grade 4, actively infected, cases.[14]

The timing of reconstruction depends on several factors. Bowel edema, gross contamination, or patient instability may preclude definitive abdominal wall reconstruction. Wound preparation and control of infection are 2 key principles for successful reconstruction of the abdominal wall. If a patient has a contaminated wound with necrotic tissue, irrigation and debridement should be the first line of therapy. Once a clean wound has been achieved, wound coverage with occlusive dressings, vacuum-assisted wound closure (VAC) devices, absorbable prosthetic material, or a split-thickness skin graft over fully adhesed and granulated intra-abdominal contents may serve as a temporizing solution.

This method of wound coverage with delayed fascial repair allows for stabilization of the patient until definitive reconstruction can be performed. Similar considerations apply to patients with acute abdominal wall defects secondary to trauma or fascial suture-line dehiscence; efforts are made to render the abdomen “frozen” (eg, with absorbable mesh material followed later by skin grafting) before proceeding with definitive reconstruction.[15]

Decision tree

Attempts to develop a simplified, algorithmic approach to abdominal wall reconstruction have proven difficult. Evidence-based recommendations regarding the optimal approach to abdominal wall reconstruction are lacking due to significant variability in technique, prosthetic material, patient characteristics, and lack of long-term follow-up in the literature. Generally, laparoscopic techniques have demonstrated fewer wound and total complications when compared with open repairs. They have also shown shorter lengths of hospital stay and lower rates of recurrence. However, laparoscopic repair is plagued by a higher rate of unplanned enterotomy and there is a size limitation to what can be repaired laparoscopically.[16, 17]

Emphasizing the role of abdominal wall compliance in hernia management, components separation techniques have gained increased popularity in recent years (see below). Despite differences of opinion in the literature currently, one point of agreement is the finding that rates of recurrence increase substantially with each attempt at reconstruction, with recurrence increasing 10-20% with each successive repair.[14] This underscores the importance of developing a sound surgical plan, with the goal of providing a durable and definitive reconstruction.

Regardless of the specific technique or material used, a surgical approach to abdominal wall reconstruction should consider all of the following:

• Establishment of diagnosis

• Perioperative condition of patient

• Definition of defect and relevant anatomy

• Knowledge of and indications for prosthetics/bioprosthetics

• Wound preparation

• Control of infection

• Timing of reconstruction

• Technical competence

• Pathophysiology of foreign body reaction

• Management of complications of procedure or prosthetics

Below is a video of an abdominal wall reconstruction with components separation, a technique that has seen increasing use since its initial description, in 1990.

Grafts

Grafts can be used in reconstructing the fascia when ample overlying skin and subcutaneous tissue are present. Autogenous fascial grafts have been used to repair abdominal fascial defects. Hamilton described a recurrence rate of 6.4% in the treatment of 47 ventral hernias with free nonvascularized fascial grafts.[18] These free nonvascularized fascial grafts have been demonstrated to maintain their structural integrity.[19, 20] Moreover, if adequate soft tissue coverage is present, the free tensor fascia lata (TFL) graft can be used in place of the pedicled TFL for fascial reconstruction because circumferential suturing of the fascia to the defect probably interferes with the delivery of blood to the fascia from the pedicle. The fibers of the TFL graft are directed in one direction. Thus, the fibers may separate and result in graft weakness. Use of TFL grafts is currently being replaced by bioprosthetic materials (see below).

Prosthetics

Following the first randomized, controlled trial comparing suture repairs to mesh reinforcement of incisional hernia repairs, the standard of care has been to use mesh to produce a supported repair of virtually all abdominal wall defects.[21]

Since that publication in the New England Journal of Medicine in 2000, improvements in synthetic mesh and the development of bioprosthetic meshes have led to a bewildering number of studies comparing one product to its competitor. These investigations were at least partly driven by the development of laparoscopic hernia repair, which inherently requires mesh to be placed directly on the bowel. In general, the advantages of using prosthetic materials include availability, absence of donor site morbidity, and added strength of the prosthetic material. Obvious disadvantages are susceptibility to infection (which may necessitate explantation), fistula formation secondary to bowel erosion, adhesion formation, extrusion, and seroma formation.

Given surgeon preference for one mesh or another, there are very few high-level clinical studies comparing one mesh with another in a scientifically rigorous manner. Thus, the reconstructive surgeon is left to extrapolate the advantages and disadvantages offered by a particular mesh from the large volume of retrospective reviews, preclinical animal studies, and industry-biased information that is available. Fortunately, the clinical performance of the most commonly used prosthetics can largely be inferred from its structure and composition.

Owing to its low cost, favorable handling, and presence on the market since the late 1950s, polypropylene is probably the most commonly used synthetic prosthetic material for abdominal fascial repair. A study by Bender of 538 patients with ventral incisional hernias (292 with primary hernias and 246 with recurrent hernias) who underwent open retrofascial repair with polypropylene mesh found the procedure to have low rates of recurrence and complications. The recurrence rates were 2.7% (primary hernias) and 4.1% (recurrent hernias), with 43 patients (8.0%) developing a wound complication; one death occurred.[22]

The latest variations in polypropylene mesh design feature a lightweight, macroscopic pore structure designed to encourage incorporation while minimizing foreign body reaction. Polypropylene is most suitable for clean wounds with adequate soft tissue coverage, as much of the literature implicating polypropylene in fistula formation or extrusion stems from its use in full-thickness defects with poor soft tissue coverage.[23, 24]

The superior tensile strength provided by polypropylene stems from its ready incorporation into surrounding tissue. However, this same capacity to be incorporated also serves as the basis for adhesion formation. In light of this, direct intraperitoneal placement of polypropylene material onto uncovered bowel has largely been discouraged. While seemingly sound in theory, much of the literature supporting the concern for fistula formation and adhesive bowel disease caused by intraperitoneal polypropylene is anecdotal and has recently been challenged.[25, 26]

Developed in response to concerns over the adhesions observed with polypropylene, expanded polytetrafluoroethylene (PTFE, Gore-Tex) mesh was designed with unique physical properties and a microporous structure with the goal of minimizing adherence. Initial studies in animal models revealed no acute host inflammatory reaction to the material. However, the lack of adherence has also been met with poor fibrovascular incorporation of the material, leading to platelike scar formation and high rates of infection and seroma formation. The tendency for expanded PTFE to encapsulate leads to insufficient anchorage of the mesh patch at the interface with the fascia and has resulted in high recurrence rates.[27]

While still used as a component of a composite mesh (discussed below), expanded PTFE has largely fallen out of favor for use in abdominal wall reconstruction. Recently, a condensed variant of PTFE has emerged onto the US market, after seeing increased use in Europe. This macroporous, condensed PTFE (MotifMESH) has been designed to minimize the susceptibility to infection observed in the microporous expanded PTFE and has demonstrated increased incorporation compared with its predecessor, theoretically resulting in decreased rates of shrinkage or seroma formation.[28, 29]

As an absorbable mesh, polyglactin 910 (Vicryl) has been found to be inert, nonantigenic, and nonpyrogenic. It has a high tensile strength, with material retention of 60% at day 7, 35% at day 14, and only 5% at day 28. Polyglycolic acid is completely hydrolyzed in 90-120 days. Vicryl mesh is a tightly woven broadcloth that is thick and flexible, though not elastic. In a contaminated operative field, placement of absorbable prosthetic material provides temporary coverage and abdominal wall support until wound contamination resolves. Absorbable material is often used in staged-reconstructive procedures.

A split-thickness skin graft can be placed directly on the granulated base of this prosthetic material for temporary closure. Subsequent hernia formation is expected after the absorption of the prosthetic material, thus absorbable materials have a limited role in the definitive reconstruction of large abdominal wall defects. That said, there is currently a considerable industry-led initiative to develop and promote synthetic, bioabsorbable mesh constructs (Bio-A, TigR matrix) that aim to combine the benefits of synthetic and biologic prosthetics.

Composite mesh material

Driven by laparoscopic repair and the complications seen with traditional synthetic materials, composite products have been designed to combine nonabsorbable materials with absorbable coatings or nonadhesive barrier materials. Numerous composite products are available in current practice, including Composix (Duval, Inc; Cranston, RI); Sepramesh (Genzyme; Cambridge, Mass); and Proceed, Ultrapro, and Vypro I/II (Ethicon, Inc; Somerville, NJ). Regardless of the material used or design structure, mechanical data on the abdominal wall after mesh implantation have evoked an interest in developing prosthetic materials that better mimic the physiology of the native abdominal wall tissues. As mentioned previously, none of these products has been able to demonstrate a clinically significant and reproducible advantage over the other commonly used prostheses.

Bioprosthetics

While synthetic mesh has dramatically improved the problem of hernia recurrence, when used in contaminated or in emergent cases, it has been plagued by high rates of infection. Based on the success of autologous grafts such as the TFL, the search for a strong, infection-resistant material contributed to the introduction of bioprosthetics. These biological meshes are derived from human or animal sources and are all composed of a preserved extracellular matrix that has been decellularized to mitigate an immune response. Cross-linking and other processing of these bioprostheses must balance durability with tissue ingrowth, in order to facilitate repopulation of the matrix with autologous cells. The ultimate aim of bioprosthetic design is to foster regeneration and remodeling over inflammation and a foreign body response.

Abdominal wall reconstruction with bioprosthetic material has gained wide popularity over the past several years, largely attributable to its application for use in contaminated surgical fields or in conjunction with concomitant bowel surgery. Three major types of bioprosthetics are being used in current practice: acellular human dermis, porcine small intestinal submucosa (SIS), and acellular porcine dermis. While an effective alternative to synthetic mesh in the face of contamination, routine use of a bioprosthetic in an elective setting should be balanced by a consideration of the high cost of the material. Available literature also suggests a higher rate of recurrence compared with synthetics when used in a supportive fashion, as well as reports of eventration when used as fascial replacement (ie, bridged technique).[30]

The great interest in bioprosthetics has fueled a large volume of active research into the underlying biology and clinical performance of these materials, which should help to more clearly define the optimal role of bioprosthetics in the management of abdominal wall defects.

Components separation

Since its original description by Ramirez et al in 1990,[31] the technique of components separation, or “separation-of-parts,” has been increasingly used as a means of restoring the dynamic properties of the abdominal wall. The technique relies on lateral release of the external oblique muscles and the creation of sliding myofascial flaps to allow reapproximation of the rectus abdominis muscles at the midline. In contrast to bridging mesh repair or other autogenous techniques that achieve closure through the use of the hernia sac itself, the components separation repair creates a more compliant abdominal wall and eliminates unhealthy, scarred tissue at the midline. Massive ventral hernias as large as 35-40 cm in transverse dimension have been successfully repaired using this method.[32] Hernia recurrence rates have been favorable, in the range of 10-20% over the long term.[33]

While high rates of postoperative wound infection and dehiscence have been reported in some studies, these complications can be significantly reduced by preservation of the periumbilical rectus abdominis perforating vessels. The use of lateral subcostal incisions to access the external obliques can obviate the need for wide undermining of skin flaps, thereby preserving the periumbilical perforators.[34]

The classic components separation technique involves the following:

1. The longitudinal release of the medial edge of the external oblique aponeurosis (approximately 1.5-2 cm lateral to the linea semilunaris), followed by blunt separation of the external oblique muscle from the internal oblique muscle in an avascular plane out to the anterior axillary line

2. Separation of the rectus abdominis muscles from the underlying posterior rectus sheath

Release of the external oblique at the linea semilunaris and the consequent advancement of the rectus abdominis muscle toward the midline is schematized in the figure below. Note that the second step, release of the rectus muscles from the posterior sheath, may not be necessary in many cases to achieve closure.

Important to note is that the current literature on components separation features a number of variations in technique without significant, high-level, evidence-based support for any one technique in particular. Long-term follow up greater than 1 year is lacking among the majority of published studies. As mentioned, consensus now appears to exist with regard to the importance of sparing the periumbilical perforators to preserve the integrity of the skin and soft tissue overlying the fascial repair. How to approach the fascial repair itself, however, is the subject of much disagreement.

Some investigators prefer the use of mesh underlay to provide support for the midline fascial repair, whereas others prefer the sole use of autogenous tissue without any prosthetic or bioprosthetic material. The choice of underlay mesh has also been debated. The largest reported series of components separation repairs (200) from Northwestern University has shown that soft polypropylene mesh underlays, in combination with components separation, yields the lowest rate of long-term hernia recurrence (0% in this series). A higher rate of recurrence was seen for bioprosthetic-reinforced repairs (33%) relative to components separation repairs with no reinforcement (23%), leading to the conclusion that bioprosthetic materials be reserved only for contaminated cases in which mesh use would best be avoided.[35]

Nonetheless, new bioprosthetic materials (eg, Strattice; LifeCell, Branchburg, NJ) are now available in large sheets with different biomechanical properties from first-generation acellular dermal matrices (eg, AlloDerm; LifeCell, Branchburg, NJ), and these agents have yet to be reported upon in large-scale ventral hernia studies.

A study by Criss et al indicated that in ventral hernia repair, moving the rectus muscles back to the midline in order to retain the linea alba restores native abdominal wall function and improves patient quality of life. In the study, dynamometric analysis was performed on 13 patients before they underwent open ventral hernia repair with midline restoration and again at 6 months postsurgery. Dynamometric evaluation showed improved isometric and isokinetic measurements during abdominal flexion. Associated improvement was found in patient quality of life at 6 months, as measured using the HerQLes survey.[36]

In a study by Maloney et al of 775 components separations, multivariate analysis indicated that the risk of wound complications is greater in the anterior version of the technique (involving external oblique muscle release with posterior rectus sheath release) than in posterior components separation (involving transversus abdominis muscle and posterior rectus sheath release), the odds ratio being 1.660.[37]

Tissue expansion

Tissue expansion has been extensively used to recruit skin and soft tissue to cover fascial repairs when available skin is sparse or unhealthy and scarred.[38, 39] Tissue expansion has been described for expansion of fascia in the treatment of abdominal wall reconstruction[40, 41, 42] ; however, this application is not commonly performed. Using tissue expansion for the skin has several advantages, including color match, contour match, and minimal donor deformity. However, tissue expansion requires at least one extra operation and possibly more, if a complication such as expander extrusion occurs.

Flaps

Myocutaneous flaps can provide skin, soft tissue, and fascia in the reconstruction of full-thickness abdominal wall defects. Myocutaneous flaps are also the preferred reconstructive option in contaminated wounds for which nonabsorbable prosthetic mesh cannot be safely used. Furthermore, myocutaneous flaps are used to reconstruct clean wounds after tumor resection to provide skin and soft tissue coverage over fascial repairs with mesh.

The rectus abdominis muscle is the workhorse in abdominal wall reconstruction. The rectus abdominis can be used with or without a skin paddle to reconstruct wounds in the upper and lower quadrants of the abdomen as well as the suprapubic and umbilical area.[43] The only area in which this flap is less suitable is the epigastrium. The rectus abdominis muscle can be based cephalically on the deep superior epigastric artery or caudally on the deep inferior epigastric artery. The rectus muscle averages 25 X 6 cm and can provide large transverse or vertical skin components.

The TFL flap is the next option for reconstruction of the umbilical, suprapubic, and lower quadrant abdominal areas.[43] The TFL flap is a myocutaneous flap based on the lateral femoral circumflex artery. The TFL muscle is 13 cm long, 3 cm wide, and 2 cm thick. The TFL muscle originates from the anterior superior iliac spine (ASIS) and the iliac crest and inserts into the iliotibial tract. The skin paddle is harvested 10 cm in width and designed over the muscle along an axis from the ASIS to the lateral tibial condyle. The inferior limit of the cutaneous territory can be extended to 6 cm above the knee and 25-35 cm in length. The lateral femoral circumflex artery can be found approximately 6-8 cm inferior to the ASIS.

The flap can be made to be sensate by designing it to include the T12 dermatome; this is done by fashioning the flap to include the area 6 cm posterior to the ASIS.[44] The rotation arc of the pedicled flap reaches the costal margin if the tensor muscle is completely detached from its origin and raised as an island flap. However, the TFL flap is not useful to reconstruct defects of the upper abdomen because the distal third of the skin paddle is less reliable.

The rectus femoris can provide muscle and fascial coverage to the lower quadrant, umbilical, suprapubic, and epigastric areas. Dibbell described the mutton-chop modification with medial fascial extension to reach this difficult area.[45] The rectus femoris muscle originates from the anteroinferior iliac spine and inserts on the patellar tendon. The rectus femoris is supplied by the lateral femoral circumflex vessels entering the muscle 6-8 cm below the ASIS or at the level of the pubic tubercle. A cutaneous paddle of 11 X 30 cm can be reliably harvested with this muscle and still allow primary closure of the donor site. The primary function of this muscle is the terminal 20° of knee extension. This flap is easier to dissect than the TFL flap but has been suggested to cause weak knee extension, which can be avoided by suturing the vastus medialis and lateralis muscles to the cut rectus femoris tendon.

Several other muscle flaps have been reported as useful in the reconstruction of abdominal defects, including the anterolateral thigh, external oblique, and the distally based internal oblique, gracilis, vastus lateralis, and latissimus muscles. Other flaps that have been used to reconstruct abdominal defects include the omentum, thigh, and groin flaps.

Vacuum-assisted closure therapy

The vacuum-assisted closure (VAC) device has revolutionized the management of wounds over approximately the past decade. The wound VAC has been shown to decrease infection, decrease wound edema, and stimulate neovascularization of the wound bed.[46] Depending on the depth of the wound and the extent of the defect, wound VAC has been used to accelerate healing by secondary intention and wound preparation prior to reconstruction with flaps and/or grafts. It is frequently used as a bridge between initial wound care and final-stage, definitive wound closure.

In a commonly used reconstructive algorithm for acute abdominal wall defects, absorbable mesh may be used to render the abdominal contents “frozen.” Following this, a VAC device may be placed to allow a bed of granulation to accumulate over the absorbable mesh, after which time split-thickness skin grafting can be performed. After several months with a stably covered wound, definitive abdominal wall reconstruction can be performed via components separation.[15]

The VAC device has also been used to control enterocutaneous fistulas. Enterocutaneous fistulas cause the adjacent wound to be exposed to succus entericus, which contains acids and enteric enzymes that hinder wound healing. The VAC device can be used to remove these secretions and promote ingrowth of granulation tissue that ultimately contracts and epithelializes but may still require skin grafting. A general surgeon should assist in treating an abdominal wound that communicates with the intestine or colon.

The list of possible complications to abdominal wall reconstruction is extensive and includes hernia recurrence, infections, dehiscence, donor site complications, ileus, enterotomy, loss of umbilicus, renal failure, respiratory failure, pneumonia, and failure of implanted prosthetic and bioprosthetic materials.

One important complication of definitive abdominal wall repair is the potential for a sudden, sharp increase in intra-abdominal pressure with the return of visceral contents to the peritoneal cavity. Intra-abdominal pressure greater than 20 mm Hg constitutes intra-abdominal hypertension (IAH). IAH can have far-reaching systemic consequences, including a decrease in cardiac output secondary to caval compression, elevated intrathoracic pressure with associated ventilatory difficulties, reduced hepatorenal perfusion with organ dysfunction, and a rise in intracranial pressure with a risk of cerebral ischemia. In its most severe form, IAH gives way to abdominal compartment syndrome (ACS), a condition requiring emergent abdominal decompression. This generally occurs when intra-abdominal pressure exceeds 25 mm Hg and can quickly progress to multiorgan failure and death if not promptly recognized and addressed.[47, 48]

The risk of ACS following definitive abdominal wall repair remains especially significant for those patients with a history of recurrent small bowel obstructions. Ventral hernias may cause frequent episodes of mechanical obstruction, each of which may take days, if not weeks, to resolve with conservative measures. Over time, chronic dysmotility of the bowel may develop. This contributes to elevated intraluminal pressure with resultant smooth muscle dilation, impaired microcirculation with resultant bowel wall edema, and bacterial overgrowth with a risk for translocation and sepsis.[48] An overall rise in intra-abdominal pressure accompanies these effects. It follows that any surgical attempt to reduce the size of the abdominal cavity might further raise the intra-abdominal pressure and incite a vicious cycle that leads to ACS. Resection of adynamic small bowel in combination with components separation may be a viable strategy to both prevent ACS and restore bowel function.[49]

A study by McGuirk et al indicated that independent risk factors for surgical site infection following complex abdominal wall reconstruction include prior abdominal infection, higher body mass index (BMI), and an increased length of hospital stay. The infection rate in the study’s 240 patients was 16.3%.[50]

The management of complex abdominal wall defects continues to evolve. Successful abdominal wall reconstruction relies on careful perioperative planning, thorough technical execution, close follow-up, and appropriate selection of synthetic or bioprosthetic material, when indicated.

Smaller defects can be reconstructed with local or regional tissue rearrangement procedures. Larger defects of the abdominal wall, which may have resulted from trauma or tumor extirpation, may require the use of myocutaneous flaps, synthetic or bioprosthetic material, or both. These reconstructions can be performed in either 1 or 2 stages. Posttraumatic abdominal wall reconstruction may require a 2-stage reconstruction.

The reconstructive surgeon must be well informed about the indications, properties, and complications associated with the use of these important biomedical tools in order to improve the quality of the lives of the patients being treated for these complex defects.

Defect size, location, depth of involvement, contamination, and comorbidity all are considerations that influence the management of abdominal wall defects. Because the potential for complications with abdominal wall reconstruction is significant, patients with comorbid conditions must be appropriately evaluated and screened. However, with meticulous planning, application of operative techniques that incorporate the principle of reconstruction with appropriate tension, and diligent postoperative care, abdominal wall reconstruction can be achieved with reasonable functional and cosmetic outcomes, patient satisfaction, and acceptable complication rates.