TRUNK AND LOWER EXTREMITY
CHAPTER 93 ABDOMINAL WALL RECONSTRUCTION
GREGORY A. DUMANIAN
Abdominal wall reconstruction (AWR) is a proving ground for the principles of plastic surgery. It requires a thorough knowledge of anatomy, an understanding of the physiology of the intra-abdominal viscera, the manipulation of multiple tissue types, the handling of alloplastic materials, and wound care. The quality of the reconstruction is judged both by the durability of the abdominal muscle repair and on the aesthetics of the final draping of skin and soft tissues over the abdominal wall. According to the Cochrane database, as many as 11% to 53% of all midline laparotomies will result in a hernia. Challenges facing surgical management of hernias include the obesity epidemic and the advent of minimally invasive procedures that have eroded the familiarity of other surgery disciplines with large open procedures and complex wounds.
This chapter attempts to provide the reader a framework for the management of all types of abdominal wall situations, including wounds, fistulae, and hernias. Management of the abdominal wall depends on:
1. An understanding of abdominal wall physiology and the forces on the abdominal wall that lead to hernia formation.
2. Strategies to deal with complex abdominal wall wounds and fistulae.
3. An appreciation of factors, such as prior surgical history, bowel issues, and nutrition, that play a role in the timing and sequence of operative procedures.
4. The attention to skin vascularity during hernia repair.
FORCES ON THE ABDOMINAL WALL
The abdomen can be conceptualized as a pressurized cylinder. The posterior one-third of the cylinder is rigid. With inspiration or for motion of the upper body and arms, a combination of diaphragm descent and abdominal wall muscle contraction causes an immediate rise in intra-abdominal pressure. In a healthy abdominal wall, the increased internal abdominal pressure is matched by an increase in the tone of the abdominal wall muscles. Where there is a local imbalance of intra-abdominal pressure and muscle tone, a bulge becomes apparent. Examples of bulges include the linea alba with the condition of rectus diastasis after childbirth and the lateral bulges seen not infrequently after flank incisions. What is important is the uniformity of the abdominal wall counterpressure. When this uniformity of abdominal wall counterpressure is lost, bulges and hernias emerge. Episodic high peaks of intra-abdominal pressure caused by chronic coughing and periodic lifting of heavy objects hasten the deformation of the weak area of the abdominal wall by the mobile internal viscera. Whereas bulges are comprised of some aspects of intact (though weakened, partially resected, or denervated) abdominal wall, true hernias are contained only by scar. The physiologic importance of this difference is understood by observing the cross-sectional appearance of bulges that are smooth curves, in comparison to the omega shape of ventral hernias. Bowel can become caught and strangulate on the lip of a hernia, while there are no risks of incarceration with bulges. While the medical indication to repair hernias is the prevention of bowel obstruction and the improvement of localized pain, the indication to repair bulges rests solely on the issues of pain that can occur with tissue stretching. Hernias typically expand with time, due to the tendency of scar to stretch and deform, and therefore often do not reach a steady state. Bulges, on the other hand, can reach a steady state in size when the inelasticity of the tissue is matched to the decrease in abdominal wall pressure that would accompany an increase in intra-abdominal volume.
Obesity plays a role in two ways—first, there is an increased amount of tissue inside the abdominal wall raising baseline intra-abdominal pressure. Second, the abdominal wall must support a greater amount of weight above the diaphragm, increasing both the intensity and number of peaks of high intra-abdominal pressure. Each peak of pressure causes stress at the suture–tissue interface.
ABDOMINAL MUSCLE PHYSIOLOGY
In a normal abdomen without a hernia, downward descent of the diaphragms and abdominal muscle contraction creates elevated intra-abdominal pressure. The Valsalva maneuver is but one example of the body using elevated intra-abdominal pressure to brace and make more rigid the torso for effective use of the upper body and arms for lifting. Abdominal muscle contraction in this instance is predominantly isometric—meaning that the muscle fibers increase their tone but without sarcomere shortening. In cases of large hernias, abdominal muscle contraction no longer increases intra-abdominal pressure, because the viscera can escape out into the hernia. The abdominal wall muscles now shorten (isotonic contraction) rather than simply increase in tension. This increases the work of the abdominal wall, because isotonic contraction consumes more energy than does isometric contraction. Additionally, the diaphragm and upper torso no longer can “push off” against a pressurized abdomen, creating dysfunction between the chest and abdominal compartments. The more massive the hernia, the larger the derangement of abdominal wall physiology.
Another concept useful in understanding the forces of the abdominal wall musculature and the utility of AWR is abdominal wall compliance. Compliance is measured by the change in volume for a given change in intra-abdominal pressure. As abdominal compliance increases, more volume can be accommodated for the same increase in pressure. If the compliance of the abdominal wall is improved, it follows that during a hernia repair, the contents of a hernia sac (volume “outside” the abdomen) can be more easily reduced back into the abdomen. Indeed, it has been shown that experimental hernia repairs are more successful when the abdominal wall is compliant than when it is stiff. Causes of abdominal wall stiffness include lateral incisions, large abdominal meshes from prior hernia repair, and intraperitoneal sepsis and scar formation.1 An emphasis on the forces on the abdominal wall is more important for surgically induced ventral hernias than for spontaneous abdominal wall defects, where deficiencies in extracellular matrix may play a prime pathologic role.2
The Effect of Repair on Abdominal Wall Forces
The goal of a hernia repair is to reestablish uniform abdominal wall counterpressure against the viscera, improving the counterpressure where it is weak, and if necessary, weakening the abdominal wall where it is strong. In suture repairs (also known as direct repairs), the abdominal wall is approximated primarily. There is no change in the abdominal wall compliance, and the greatest tension is at the site of the repair. “Unsupported” direct repairs (those without some type of mesh) rely solely on sutures to hold the abdominal wall. “Supported” direct repairs attempt to distribute the forces on the repair over a larger area by adding mesh to the repair site. Another type of hernia repair is with a piece of mesh that spans across an open defect of the abdominal wall. In these types of “bridged” repairs, sutured mesh acts like a cap or lid, replacing the weak area of the abdominal wall. This avoids an increase in focal forces on the abdominal wall where the tissues have previously failed. The strength of the mesh to resist outward deformation depends on the strength of the circumferential attachment of the mesh to the normally innervated abdominal wall. The larger the hernia, the further the mesh center is from innervated abdominal wall, and the greater will be the eventration.
The prime reason for hernia recurrence is suture pulling through the tissues over time like a wire cutting through ice. Improved force distribution over the hernia construct with decreased tension experienced by each stitch will lead to lower suture pull-through. Direct supported repairs use mesh as a load-sharing manner as opposed to a load-bearing manner for bridged repairs. Improved force distribution and decreased pull-through are the primary reasons that supported repairs have lower failure rates than primary repairs or bridged repairs. Obesity and lateral abdominal wall noncompliance increase the forces felt by each stitch—an explanation for higher failure rates in these situations.
A final manner of repairing the abdominal wall is with the components separation technique for midline defects. Releases of the external oblique muscle and fascia from its attachment to the rectus abdominis muscles allows for a repair of the rectus muscles in the midline while simultaneously improving the abdominal wall compliance on the sides. Components’ separation repairs can be either “unsupported” or “supported” depending on the clinical situation.
CLOSING THE WOUND
When patients are ill, wounds are inflamed, and nutrition is poor, open abdominal wounds should be treated with simple procedures that have high chances for success. Patients who are packed open after a laparotomy can often be closed primarily after bowel swelling has resolved. For those patients that cannot have their fascia closed due to persistent visceral swelling or intra-abdominal sepsis, early wound closure in the simplest manner possible provides multiple benefits, including patient comfort, ease of wound care, and a decreased incidence of enterocutaneous fistulae.3 To devise a wound closure plan, the following questions must be answered: Are the viscera “frozen,” and what are the chances for an evisceration? Do bowel contents need to be controlled? What are the location, size, and characteristics of the wound? Should the surrounding skin be modified to help achieve wound closure?
Open Wounds and Evisceration
Bowel found outside the skin are surgical emergencies that require immediate evaluation and thoughtful treatment in the operating room. Much depends on the cause of the loss of the abdominal wall integrity. Pure technical problems of broken suture and untied knots do occur, but are uncommon. When detected quickly, these patients at exploration have pristine wounds and can simply be reclosed. If sutures are noted to have torn out of weak fascia, the conversion to a direct supported repair or the use of retention sutures is successful without repeat disruption 55% of the time.4 Mass closures with retention sutures can be successful, but the sutures can cause skin and tissue necrosis.
More commonly, the patient has an ileus and the bowel is swollen. These are usually contaminated wounds and there is often an underlying septic intra-abdominal process. Therefore, the goal of surgery is to replace the intestines back into the abdomen and to prevent a second evisceration. Necrotic tissue is debrided, intra-abdominal fluid collections are allowed to drain, and a compartment syndrome from swollen bowel is avoided. For these sick patients, a temporary mesh—typically absorbable polyglycolic acid—is placed using a running absorbable monofilament suture to “close” the abdominal wall and to keep the viscera in their proper domain (Figure 93.1A). The bridging nature of the mesh across the fascial defect increases the intra-abdominal volume. Secondary dehiscence is unusual because the lateral abdominal muscles are now shortened and cannot generate a maximal contraction during coughing and movement. The porous nature of the closure allows intra-abdominal fluid to drain into the overlying gauze or a subatmospheric pressure dressing. When the patient has stabilized, skin closure is performed by delayed primary closure, by skin grafts, or by secondary intention. When the skin gapes widely and several months would be required for closure by secondary intention, skin grafting provides the simplest and most reliable closure as discussed below.
An alternative to closure with a temporary porous mesh is patching the open fascial defect with a human or porcine bioprosthetic mesh. Bioprosthetic meshes have been touted for their tolerance of inflamed fields, resistance to infection, and ability to restore abdominal wall continuity, at least temporarily. While this may be true, granulation of the bioprosthetic meshes may lead to a rapid loss of tensile strength of the biomaterial. Disadvantages of these products include their high cost, and relative impermeability to intra-abdominal fluid in comparison to polyglactin mesh. These disadvantages would be less important if a later AWR could be avoided, but this has not yet been borne out in the literature. Finally, repair of these fascial defects with permanent mesh was tried and abandoned in the earliest papers on AWR. The heavyweight polypropylene was associated with fierce adhesions, extrusions, enterocutaneous fistulae, and occasional mortality.
While eviscerations with exposed bowel require operative intervention, the treatment of open wounds after laparotomy requires a more thorough history, physical examination, and radiologic evaluation. Open wounds after laparotomy may represent simple skin wounds, but they may also harbor fascial defects with exposed viscera at their base. Clues for fascial dehiscence include loose abdominal sutures at the base of the wound, a history of a “seroma” (a clue that intra-abdominal fluid is emerging through the open abdominal wall), or a computed tomography (CT) scan demonstrating superficial bowel loops. The timing from the latest abdominal exploration is also a critical factor in the evaluation of a potential evisceration. Open wounds with a fascial dehiscence less than 1 week from the last exploration are at high risk for evisceration and should probably be explored to prevent an even larger dehiscence leading to a surgical emergency. Wounds with fascial dehiscence over 2 weeks from laparotomy usually have enough intra-abdominal adhesions to avoid an evisceration and can usually be managed as standard wounds. Wounds between 7 and 14 days require judgment to decide whether the exploration would have a higher chance of causing a bowel injury than it would prevent an evisceration. Patient factors such as age, previous presence of adhesions, and wound healing issues such as steroids play into the decision. Patients on steroids may require up to 3 weeks before adhesions between bowel loops are strong enough to avoid an evisceration.
For the patients with open wounds, unknown fascial integrity, and a low chance for evisceration, informed consent is important. Patients with open abdominal wounds after a laparotomy have a high incidence of later hernia formation. These patients should be informed that surgical treatment of open abdominal wounds have a risk of creating an enterocutaneous fistula, and that with or without treatment, there is a high risk of a ventral hernia. The patients are informed that “conservative” treatment with dressing changes is also not without risk, as the intense local inflammation may cause an opening at a bowel suture line or site of a previous serosal tear. All things considered, early wound closure increases patient comfort, reduces the chances for bowel injury, and is the first step in AWR. The most reliable method of wound closure is with skin grafts (Figure 93.1B and C). The “two-dimensional” healing of skin grafts is not dependent on the patient’s nutrition, unlike the “three-dimensional” healing required for sutured skin flaps, and may proceed despite suboptimal nutrition parameters.
FIGURE 93.1. Open abdomen after treatment for pancreatitis. A. Evisceration was prevented with PTFE mesh, which was sewn to the edges of the abdominal wall with running sutures. Intra-abdominal fluid drained easily onto the dressings, which can be seen overlying the mesh. B. Three weeks after the definitive laparotomy, the PTFE mesh was removed and the wound gently debrided. Skin grafts were placed for early wound closure. C. The skin grafted hernia defect with laterally displaced skin and rectus muscles.
Skin Grafting for Early Wound Closure—Technique
At the time of surgery, the overhanging skin edges are saucerized to create a flat surface for grafting. Skin bridges are divided. If polyglactin mesh had been used to prevent evisceration, a visual clue that the open abdomen is ready for skin grafting is that individual bowel loops are no longer discernable amidst the sea of granulation tissue. A second visual clue is that polyglactin mesh also wrinkles as bowel edema recedes. After removal of the polyglactin mesh, the thick layer of granulation tissue overlying the bowel is bluntly debrided using a large periosteal elevator. As long as only the surface of the bowel mass, and not individual bowel loops, is debrided prior to skin grafting, the loops stay matted to the undersurface of the abdominal wall and to each other. The grafts are fixed with lateral staples and central chromic sutures, and a moist dressing applied. Moist dressing changes on the graft itself are initiated 2 to 5 days after the placement of the graft. Unlike the base of the wound, the sidewalls take skin graft poorly, probably due to poor vascularity and significant motion on the sides of the skin flaps. Therefore, the side walls need not be grafted.
Every tube placed percutaneously into the bowel is a fistula. The difference between the controlled fistulae seen on a general surgery service and the fistulae in the midst of an open abdominal wound is a lack of overlying soft tissue. When a percutaneous tube is removed, the overlying integument contracts around the tract. When a fistula occurs in the center of a wound, there is no overlying soft tissue to help the fistula to seal. Bowel rest, nasogastric decompression, and octreotide help decrease the flow of succus entericus across the fistula and aid in wound management. Frustratingly, the granulation tissue surrounding the fistula prevents adherence of an ostomy device to catch the fluid. The way to stop the fistula is to perform a bowel resection and repair, but this type of patient is generally a poor candidate for an intra-abdominal procedure. The open abdominal wound, associated tissue edema, and friability are setups for difficult operations and recurrent fistula formation. An alternative is wound closure with skin grafts to convert the fistula into an ostomy, allowing for patient comfort and cleanliness, and to delay definitive surgery. Skin grafts take well on tissue surrounding the fistula, but it is essential to keep the surgical site free of succus for the first 24 to 48 hours after graft placement to encourage skin graft adherence. Suction is applied to a rubber catheter placed into the fistula to remove succus. Attention to detail is critical to keep this tube functioning early after surgery. After 48 hours, moist dressings are begun to the entire grafted area for cleanliness and to aid epithelialization. After 14 to 21 days, the skin graft is strong enough to withstand placement of an ostomy bag. Three to six months are usually required for inflammation to subside and the wound to soften before definitive reconstruction.5
Wound Shape and Location
In the infraumbilical area of the obese patient, some wounds are so deep and/or contain so much fat necrosis that local wound care will not achieve closure in a timely manner. In these selected patients, a panniculectomy encompassing the necrotic tissue is helpful to change the shape of the wound. Even if part of the wound is left open intentionally, a transversely oriented wound closes much more quickly than a vertically oriented wound. Prior to panniculectomy, a CT scan may be obtained to confirm the position of the bowel to avoid an iatrogenic injury.
RECONSTRUCTION OF THE ABDOMINAL WALL AND SOFT TISSUES
Much like fracture healing, healthy soft tissue coverage is required for primary healing after laparotomy. In the ideal case, the patient has a stable closed wound with soft pliable tissues over the hernia sac. If not, a plan to manage the soft tissues is just as important as the plan to repair the abdominal wall. The timing for AWR is also important. An easy rule to remember: if the hernia is expanding, it is ready for repair. An expanding hernia implies that bowel adhesions and scar attaching the bowel to the abdominal wall has significantly softened and will be straightforward to dissect.
Midline Abdominal Wall Defects with Stable Soft Tissues
When the skin and subcutaneous tissues are pliable, no wounds are present, and no gastrointestinal surgery is planned, many options exist for hernia repair. For small hernias less than 3 cm across, adirect suture repair is often performed. However, given the surprisingly high recurrence rate,6 mesh may be added to the fascial closure to achieve a direct supported repair. Laparoscopic mesh repairs can be ideal for hernias greater than 3 cm by CT scan. These repairs have been shown in the literature to have recurrence rate in the 3% to 4% range, low incidences of infections, short hospitalizations, and quick recoveries.7,8 The hernias should not have a neck greater than 6 to 8 cm to facilitate the placement and maneuvering of trocars and to avoid eventration of the central nonsupported aspect of the mesh. Other options for treatment of hernias with stable soft tissues include open mesh repairs and closure with the components separation technique.
In open hernia mesh repairs, the quality of the attachment of the mesh to the abdominal wall is paramount. When mesh repairs fail, it is typically due to lack of a durable attachment of the mesh to the abdominal wall. Compliance mismatches between the mesh and the lateral aspect of the abdominal wall stiffened over time by the presence of the hernia leads to high stress zones and possible failure/suture pull-through. Helpful techniques include placing the mesh intra-abdominally and ensuring an overlap of at least 3 cm between the mesh and the abdominal wall. Intra-abdominal mesh placement maximizes the attachment of the mesh to the abdominal wall because the pressure of the viscera pushes the mesh against the abdominal wall. A wide zone of contact greater than 3 cm smooths out compliance issues between the mesh and the abdominal wall. The “Goldilocks principle” guides the number of sutures required; enough are needed to prevent the herniation of a bowel loop between stitches, but too many can cause ischemic necrosis of the edge of the abdominal wall, and in turn lead to a poor mesh attachment. Components separation repairs of midline defects have certain advantages and will be discussed subsequently.
Types of Mesh
Mesh materials have distinctive properties and compositions that result in different complication profiles. Permanent mesh materials retain their properties over time and are generally formulated from either weaves of polypropylene, polyester, or expanded polytetrafluoroethylene (PTFE). These types of mesh are characterized by their porosity: the greater the porosity, the more the mesh is incorporated into the soft tissues. Mesh incorporation may be associated with a lower infection rate. Shrinkage can occur in some types of mesh material over time, so that the mesh no longer covers the same surface area of abdominal wall as when it was originally placed.9 PTFE meshes tend to become encapsulated rather than integrated into tissues, and this leads to a relatively high shrinkage rate.10. The tendency of the mesh to form adhesions to the viscera is another troublesome property. PTFE tends to form the fewest adhesions due to its smooth, nonporous nature. Coatings on the surface of permanent mesh are touted to decrease the chance of problematic adhesions to bowel. A general rule of thumb is that permanent meshes are incompatible with grossly contaminated wounds and are relatively contraindicated in mildly contaminated fields.
The physicomechanical properties of the mesh are important to its handling in the operating room, and the ease of placement without wrinkles. Wrinkled mesh may be a prime cause of extrusion (a pressure sore through the skin), adhesions, and enterocutaneous fistulae (caused by a pressure sore into the bowel).11 Commonly used heavy weight mesh is far stronger and stiffer than the native abdominal wall; lightweight and midweight polypropylene weaves have been developed to improve biomechanical compatibility with the soft tissues.
Bioprosthetic meshes are novel treatments of either human or porcine dermis that have initial strengths greater than the abdominal wall. Therefore, they may be ideal materials for abdominal wall repair. Comprised of the skeleton of dermis or fibrous submucosa of bowel, the materials allow for ingrowth of fibrous tissue and incorporation in a manner different from permanent mesh. As the materials are replaced by the body’s own tissues over time, they may be more resistant to infection, and therefore may tolerate mildly contaminated fields. Bioprosthetic mesh has been found to form fewer adhesions to bowel than permanent mesh in laboratory studies.12 The long-term durability of these materials is uncertain. There seems to be a relationship between the rate of bioprosthetic mesh incorporation and eventual loss of structural integrity, i.e., the more the integration, the greater the loss of integrity over time. Human dermis may be integrated more quickly than porcine products, leading to eventual loss of support of the abdominal wall. Enzymatic preparation of porcine mesh reduces antigenicity and permits fibrous ingrowth. However, collagen cross-linking of porcine dermis, designed to produce a longer-lasting material, may also limit ingrowth and cause encapsulation rather than integration of the bioprosthetic. Widely varying recurrence rates have been reported when biomaterials are utilized in direct supported repairs of the abdominal wall.13,14
Lateral Abdominal Wall Defects with Stable Soft Tissues
In contrast to midline hernias that tend to be large, lateral abdominal wall defects tend to be smaller and with good soft tissue cover. The hernia can typically be repaired using mesh, placed either laparoscopically or using the open technique. CT scans often demonstrate dehiscence of the transversus abdominis and internal oblique muscles, with continuity of the external oblique. These true hernias can be improved with direct supported repairs of the abdominal wall. On occasion, for larger non-midline hernias where there has been a mild loss of domain, a contralateral release of the oppositeexternal oblique (described in the following section) is performed to give the hernia contents more room in the abdominal cavity and to improve overall abdominal compliance.
More troublesome are the lateral bulges that are associated with some degree of denervation injury to the abdominal musculature. These bulges occur not infrequently after flank incisions for exposure of the spine and the retroperitoneum. Informed consent on operative management of these lateral bulges is critical, because surgery generally improves but does not completely resolve the bulge, and patients are generally not satisfied with “some improvement.” Exposure of the abdominal bulge with wide elevation of skin flaps, imbrication of the abdominal musculature while flexing the operating table to take tension off the sutures, and a large mesh overlay generally improve the bulge by only 50%.
Midline Defects with Unstable Soft Tissues and/or Contaminated Fields
When both skin and abdominal wall are deficient in the midline, the procedure of choice is AWR using bilateral myofascial rectus abdominis flaps. Referred to as “components separation” and “separation of parts,” the operation described by Ramirez moves the laterally displaced skin and rectus muscles toward the midline.15
The surgical procedure involves radical removal of tissue between the medial aspects of the rectus abdominis muscles. Thin atrophic hernia skin cover, wounds, infected mesh, draining stitch abscesses, and fistulae are removed, leaving only unscarred tissue for the eventual closure.16 The releases of the external oblique muscle and fascia may be performed through bilateral transverse 6 cm incisions located at the inferior border of the rib cage (Figure 93.2). Alternatively, the external oblique muscle may be visualized by elevating skin flaps from the midline incision. Tissues over the semilunar line are elevated by blunt dissection. The external oblique muscle and fascia are then divided under direct vision from above the rib cage to the level near the inguinal ligament. The inferior aspect of the release is completed under a small tunnel that joins the lower aspect of the midline laparotomy incision with the lateral dissection. The external oblique is then bluntly dissected off of the internal oblique, allowing the muscles to slide relative to each other. The use of the lateral skin incisions avoids wide skin undermining and preserves the blood supply to the skin from rectus abdominis muscle perforators. This approach has been shown to decrease wound healing problems that may occur with skin undermining. After approximation of the fascial edges, the midline closure is similar to a standard laparotomy incision. The significantly improved soft tissue vascularity gives the operative team the confidence to perform simultaneous bowel surgery without an increase in soft tissue infections.17
The hernia rate of an unsupported component release repair is approximately 24% at 10 months compared with 0% at 13 months for repairs supported by soft polypropylene mesh.18. The preservation of skin perforators decreases wound complications, but it also prevents the placement of large overlay meshes. However, an intra-abdominal mesh underlay can be used to augment the midline closure and to distribute tension away from the suture line (Figure 93.2B and C). Direct supported repairs using components separation augments the central strength of the repair, while simultaneously improving the lateral abdominal wall compliance. Lateral releases also serve to increase the intra-abdominal volume, and so reduce the chance of an abdominal compartment syndrome from the loss of domain found in these large hernias.19 The mesh, either prosthetic or bioprosthetic, may be placed intra-abdominally or immediately behind the rectus muscles (retrorectus), based on the preference of the surgeon.
An analysis of factors that make hernias easy or difficult to close is helpful when approaching a patient with a large hernia. Significant weight loss since the last laparotomy, a hernia centered on the umbilicus, no previous use of retention sutures, a compliant lateral abdominal wall from pregnancy, and the absence of previous stomas all make the hernia repair more straightforward. Conversely, an upper abdominal hernia, scarred rectus muscles, stomas, lateral abdominal wall stiffness due to previous lateral incisions, and a history of severe intra-abdominal sepsis all make the repair more difficult. Previous mesh repairs make the dissection more difficult, but make the repair easier, because the mesh typically keeps the rectus muscles medialized and the hernia small. By CT scan measurement, simple releases of the external oblique have allowed each of the rectus muscles to be moved 8 to 10 cm medially. In the majority of cases, releases of the external oblique muscle and fascia alone will allow the recreation of the linea alba without any bridging or spanning mesh in direct supported components release repairs. Releases of additional components of the abdominal wall, including the transversalis fascia or the internal oblique, can be performed, but run the risk of significant weakness along the semilunar line particularly if the rectus abdominus muscle is denervated. This maneuver is unnecessary and should generally be avoided.
FIGURE 93.2. (A–C) Components separation. A. Technique for components separation hernia repair with lateral incisions for the release. B. Direct supported repair with intra-abdominal midweight polypropylene mesh. C. Four years following the repair of a midline hernia with direct supported components separation technique.
Perforator preservation and medial mobilization of the rectus muscles will bring well-vascularized skin to the midline. Healthy soft tissue coverage allows for the radical excision of the scarred and contaminated midline hernia sac. It also provides protection of bridging mesh when used in truly massive hernias. This situation arises when, despite components separation, the rectus muscles do not meet in the midline and the underlying mesh is not completely covered by the muscle repair. With perforator preservation, the skin and subcutaneous tissue covering the mesh are more robust and there is a markedly reduced risk of mesh exposure.
Obese patients with large pannuses and infraumbilical hernias may be addressed through a panniculectomy incision.20 The panniculectomy addresses the heavy thick skin while simultaneously exposing the fascial edges of the hernia. Releases of the external oblique can be performed through narrow tunnels elevated from within the surgical wound. Increased complications, including hernia recurrence and wound complications, have been encountered with increasing body mass index, and when a “T”-shaped incision is employed to elevate tissues above the umbilicus.
Combined Non-Midline Abdominal Wall and Soft Tissue Defects
Patients with missing abdominal wall and overlying soft tissues due to tumor resection, chronic inflammation, necrotizing infection, and trauma represent true surgical challenges. Bowel fistula can be located in the center of these defects. Surgery planning rests on the decisions of two independent but related questions: How best to replace the abdominal wall and how best to replace the skin?
For repair of the soft tissues, decision making depends on the shape, size, and location of the defect. Narrow transverse defects of skin can often be repaired with wide undermining, flexion of the patient on the operating table, and closure like an abdominoplasty. A preoperative “pinch” test will determine the suitability of this plan. Narrow vertical defects are similarly treated, though the wide undermining required may lead to skin necrosis of the midline. Circular defects require more ingenuity and planning. Tissue expansion of good quality lateral tissue is one option. The largest size tissue expanders are placed, with access incisions oriented in the direction of the eventual movement of the tissue. Flaps based on periumbilical perforators are useful and moved as propellers (Figure 93.3). The location of these perforators can be seen on routine CT scans and confirmed by Doppler. The orientation of these flaps should be parallel to a line drawn between the umbilicus and the tip of the scapula. Lower abdominal defects can be covered with pedicled vastus lateralis/anterolateral thigh flaps. Increased reach of the flap is attained by passing the flap deep to the rectus femoris with division of the rectus pedicle to more generously cover the abdomen.21 This myocutaneous thigh flap may carry more soft tissue and be of greater width than the tensor fascia lata flap. In the upper abdomen, tissue expansion with the expanders located on the rib cage is effective. Upper abdominal soft tissues can be covered by stealing from the lower abdomen with rectus myocutaneous flaps. Perforator flaps based on external oblique or latissimus blood supply can cover the lateral abdominal wall. Free flaps are solutions for the largest circular defects not coverable using thigh- or latissimus-based flaps. If necessary, skin grafting of granulated bioprosthetic mesh can delay the final AWR to another day.
FIGURE 93.3. (A–C) Radiated inflamed hernia and associated enterocutaneous fistula that had failed two previous repairs through a midline incision. A. The star represents a periumbilical perforator from the left deep inferior epigastric artery. The large abdominal wall defect extends from near the right stoma to the level of this star. The proposed propeller flap is marked and will cover the circular soft tissue defect. B. After radical removal of scar and small bowel resection, the abdominal wall is repaired with a large sheet of bioprosthetic mesh. Bioprosthetic mesh is chosen due to the history of radiation, the presence of a bowel suture line, and the contaminated nature of the procedure. C. The healed wound 3 weeks after surgery.
The quality of the soft tissue repair and its dependability will dictate how the abdominal wall is reconstructed. A direct repair of the abdominal wall is unlikely when the soft tissues have wide defects. After components releases of the rectus muscles, the abdominal wall compliance will be improved, but the size of the defect may require bridging of the abdominal wall. A clean surgical field with minimal contamination, no serosal tears of the bowel, and reliable soft tissue flaps permits the use of prosthetic mesh to bridge the defect. Conversely, the presence of intraabdominal suture lines contamination, radiation, or persistence of inflamed tissue are all indications for bioprosthetic mesh. Should there be any concern for potential exposure of the abdominal wall repair due to the unpredictability of a reliable soft tissue envelope, a bioprosthetic mesh should be strongly considered.
Abdominal wall hernias are challenging and recalcitrant problems. Without a thoughtful preoperative strategy, recurrence and further morbidity is guaranteed. Understanding abdominal wall physiology and wound healing is essential. Whenever possible, scarred tissues should be discarded and healthy unscarred tissues mobilized for repairs. Individualizing the operative plan based on the unique features, hernia, soft tissues, and the overall health of the patient is required for success.
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