A postoperative ventral abdominal wall hernia, more commonly termed incisional hernia, is the result of a failure of fascial tissues to heal and close following laparotomy. Such hernias can occur after any type of abdominal wall incision, although the highest incidence is seen with midline and transverse incisions.41 Postoperative ventral hernias following paramedian, subcostal, McBurney, Pfannenstiel, and flank incisions have also been described in the literature. Laparoscopic port sites may also develop hernia defects in the abdominal wall fascia.
As the approximated fascial tissue separates, the bowel and omentum herniate through the opening, covered by a peritoneal sac. These hernias can increase in size to enormous proportions, and giant ventral hernias can contain a significant amount of small or large bowel. At the extreme end of the ventral hernia spectrum is the giant incisional hernia that leads to loss of the abdominal domain, which occurs when the intra-abdominal contents can no longer lie within the abdominal cavity.
Incisional hernias have been reported in up to 20% of patients undergoing laparotomy. Modern rates of incisional hernia range from 2% to 11%.42–44 It is estimated that approximately 100,000 ventral incisional hernia repairs are performed each year in the United States alone. The incidence seems to be lower in smaller incisions so that laparoscopic port site hernias are much less common than hernias following large midline abdominal incisions. While it was once believed that the majority of incisional hernias presented within the first 12 months following laparotomy, longer-term data indicate that at least one-third of these hernias will present 5–10 years postoperatively.
Multiple risk factors exist for the development of an incisional hernia. Some of these risks are under the control of the surgeon at the initial operation, while many others are patient specific or related to postoperative complications. Patient-specific risks for postoperative ventral hernia include advanced age, malnutrition, presence of ascites, corticosteroid use, diabetes mellitus, cigarette smoking, and obesity.41,45–47 Emergency surgery is known to increase the risk of incisional hernia formation. Wound infection is believed to be one of the most significant prognostic risk factors for development of an incisional hernia.41,48 It is for this reason that many surgeons advocate aggressive and early opening of the skin closure to drain any potential infection at the fascial level. Postoperative sepsis has also been identified as a risk for subsequent incisional hernia.
Technical aspects of wound closure likely contribute to incisional hernia formation. Wounds closed under excessive tension are prone to fascial closure disturbance. Therefore, a continuous closure is advocated to disperse the tension throughout the length of the wound. In this way, 1 cm bites of fascia on either side of the incision are taken with each pass of the suture and the suture is advanced 1 cm at a time along the length of the incision. The type of incision may affect hernia formation. Studies have shown that transverse incisions are associated with a reduced incidence of incisional hernia compared to midline vertical laparotomies, although the data are far from conclusive.46,49
The patient with an incisional hernia will complain of a bulge in the abdominal wall originating deep to the skin scar. The bulge may cause varying degrees of discomfort or may present as a cosmetic concern. Symptoms will usually be aggravated by coughing or straining as the hernia contents protrude through the abdominal wall defect. In large ventral hernias, the skin may present with ischemic or pressure necrosis leading to frank ulceration. Presentation of the incisional hernia with incarceration causing bowel obstruction is not uncommon. This may be associated with a history of repeated mild attacks of colicky dull abdominal pain and nausea consistent with incomplete bowel obstruction.
On examination the hernia is usually easy to identify and the edges of the fascial defect can often be defined by palpation. The entire abdominal wall along the length of the incision should be inspected and palpated carefully, as multiple hernias are often present in the setting of an incisional hernia. In the obese patient with a suspected incisional hernia that cannot be confirmed on examination, computed tomography of the abdomen is the best way to visualize intra-abdominal contents within the hernia sac. In extreme instances, laparoscopy may be required to diagnose a hernia defect that only intermittently contains intra-abdominal contents.
The treatment of ventral incisional hernia is operative repair, and three general classes of operative repair have emerged in the modern era. These techniques include primary suture repair of the hernia, open repair of the hernia with prosthetic mesh, and laparoscopic incisional hernia repair. The major sequela from operative repair of the incisional hernia is hernia recurrence, and there are convincing data that placement of mesh to repair the hernia defect has decreased the high recurrence rate historically associated with primary suture repair to less than 25%.50,51 Many advocates of the operation believe that laparoscopic incisional hernia repair will have the lowest rate of hernia recurrence and definitive studies are underway to assess this question.
In general, primary repair of incisional hernias can be performed for hernia defects less than 4 cm in diameter with strong, viable surrounding tissue. For larger hernias or hernias associated with multiple small defects, mesh repair is indicated. Even with mesh repair, hernia recurrence remains a significant complication. In one multicenter trial, for example, 200 patients were randomly assigned to suture or mesh repair of a primary hernia or a first recurrence of hernia at the site of a vertical midline incision.52 The 3-year cumulative rates of recurrence among patients who had suture or mesh for repair of a primary hernia were 43% and 24%, respectively. The rates of second recurrence were 58% and 20%, respectively.
The operation is best performed with the patient under general anesthesia to achieve full relaxation of the abdominal wall musculature. The skin is opened through the previous incision and dissection is performed through the subcutaneous tissues. Care should be taken as the level of the anterior rectus sheath is approached since portions of the sac and its contents may lie at this level. The sac is identified and cleared of its attachments to the fascia using electrocautery. In this way, any peritoneal attachments to the anterior abdominal wall in the vicinity of the hernia are taken down and the sac is fully reduced into the abdominal cavity. The fascia is then cleared of soft tissue both anteriorly and posteriorly for at least a 3–4 cm margin. This allows for a margin of healthy fascia to bring together in the midline with suture closure.
The fascia is then closed using an interrupted layer of nonabsorbable suture by taking large bites of the clean fascia on both sides of the defect. The sutures are usually placed sequentially and then tied after the entire layer of suture has been placed. The fascia is then inspected to confirm that no additional defects are present and that the repair sutures are not pulling through the tissue due to excessive tension. The skin is closed over the fascia using either staples or a running subcuticular layer. If the hernia contents have created a large pocket in the soft tissue above the anterior fascia, placement of a closed suction drain for evacuation of early seroma fluid can be considered.
If there is tension upon attempted closure of the abdominal wall, a separation of components can be performed in order to mobilize the fascia toward the midline (Fig. 7-17). This technique begins with the mobilization of the skin and soft tissue off of the underlying fascia. The fascia of the external oblique is then incised lateral to the rectus abdominis and the external oblique is dissected free from the internal oblique in a relatively avascular plane. This alone allows for significant mobilization of the abdominal wall toward the midline. Should additional mobilization be required, the posterior rectus sheath can be incised in a longitudinal fashion to allow the overlying rectus abdominis and anterior rectus sheath to slide even further toward the midline.53 This technique allows for closure of complex or infected abdominal wounds without the need for implantation of any foreign material.
Separation of components of the abdominal wall to mobilize the fascia toward the midline.
Over the last 10–15 years, the introduction of component separation as a method for repairing ventral hernias has gained increasing popularity due to its conceptual purity and its overwhelming success. Recent series including those by Ko54 has reported his experience in 200 patients who underwent this procedure over the course of slightly over 1 decade. The overall recurrence rate was 21%. Supportive polypropylene mesh was employed to cover the defect. In the process of performing this procedure, bilateral releases of the external oblique muscle are performed and the fascia is mobilized, thereby allowing medial movement of the rectus muscle. This brings the rectus muscle closer to the midline and achieves a muscular closure of the midline which can be reinforced or strengthened by the placement of either biologic or manufactured mesh. Mesh is not a necessary portion of the component separation technique although it is frequently used. The variety of different types of mesh includes polypropylene, polyester, and other both biologic and nonbiologic materials. Primary repair using no mesh but using the component separation technique had a 22.5% recurrence rate, while recurrence rates using cadaveric biomesh were 33.3%. Those in whom low-weight polypropylene was used had a 0% recurrence rate. Part of the study looked at demographic factors and noted that elevated body mass had a significant risk of recurrence. This was true at less than a p value of 0.005 and also notable most commonly in patients with a BMI of greater than 25.
The use of sheets of nonabsorbable prosthetic mesh placed across the incisional hernia defect and sutured to the abdominal wall is routinely employed in the modern era. It is associated with a low incidence of perioperative complications and lower rates of recurrence than open, nonmesh repairs.
Many variations of mesh repair for the incisional hernia have been described (Fig. 7-18). The mesh is cut to the shape of the hernia defect with a margin added circumferentially around the mesh to suture to healthy surrounding fascia. The mesh is sutured to the fascial layer either deep to the peritoneum or between the peritoneum and the abdominal wall. Alternative techniques have been described that suture pieces of mesh to fascia from both intra- and extraperitoneal planes.
Variations of prosthetic mesh repair for incisional hernia. A. Underlay graft. B. Inlay graft. C. Overlay graft. D. Combined overlay and underlay grafts. E. Large underlay graft. F. Large overlay graft. G. Combined large overlay and underlay grafts. H. Reinforcing onlay and underlay strips of mesh. I. Wrap-around mesh reinforcement of wound edges. J. Two sheets of mesh sutured to abdominal wall, then sutured to each other to draw together the edges of the wound.
The operation is performed under general anesthesia. The old scar is incised and the soft tissue dissected down to the level of the anterior rectus sheath. Here the defect is identified and the fascia is cleared of surrounding soft tissue attachments to allow a 3–4 cm rim of healthy fascia circumferentially. The sac is then freed from the fascia in order to reduce the hernia contents and prevent recurrence. This portion of the operation is often technically challenging, as significant adhesion formation may have occurred following the initial operation. It is often impossible to stay in an extraperitoneal plane in this situation, and dissection within the abdominal cavity may be necessary to fully excise the sac and reduce its contents. The mesh can now be placed either anterior to the fascia or posterior from within the intra-abdominal cavity. Effort should be made to protect the bowel from direct contact with the mesh patch, and a layer of omentum can often be placed between them. The mesh is sutured in an interrupted fashion in multiple sites throughout the entire circumference of the patch to ensure that any tension is distributed throughout the entire area of the repair. Large, nonabsorbable suture is used to affix the mesh to the fascia layer.
There are currently a variety of mesh products readily available for use in the repair of ventral incisional hernias. In general, these products can be grouped into those that are composed of synthetic materials and those that are composed of biologic materials. The synthetic meshes frequently incorporate either polypropylene or expanded polyfluorotetraethylene (ePTFE) in combination with some form of barrier to prevent adhesions to the bowel. While both polypropylene and ePTFE are used in the treatment of ventral hernias, they have significantly different properties. Polypropylene meshes are macroporous and allow for ingrowth of native tissue into the mesh, leading to incorporation. Conversely, ePTFE meshes are more microporous and do not promote as much ingrowth. This leads to less adhesions to ePTFE meshes, but also requires that there is adequate fixation in order to prevent disruption and thus recurrence. Biologic meshes are based on acellular dermal matrices from human, porcine, and fetal bovine sources. While the long-term outcomes for these meshes are currently being studied, the biologic meshes have been shown to be more resistant to infection than their synthetic predecessors and are more appropriate for use in infected or contaminated fields.55
Biologic grafts derive from two basic materials. The first is human tissue and the second is animal tissue. Their use in hernias is confined primarily to dirty or contaminated fields in which placement of a prosthetic mesh might increase the chance of infection. It is well recognized that primary closure of incisional hernias carries a high recurrence rate and that removal of prosthetic mesh in an infected field and attempts to primarily close these defects will invariably lead to recurrence. As a result, enthusiasm has recently grown for the use of biologic grafts that may enhance the repair, decrease the chances of infection, and provide a bridge to a clean wound. If recurrence subsequently develops, it can be managed with a prosthetic material. The biologic grafts have different characteristics depending on the tissue of origin. Grafts can be based on dermis, either human or porcine, or on submucosa. The dermis-based grafts are prepared in such a way as to allow collagen and elastin to remain within the matrix. Although these materials have excellent resistance to infection, they do have the distinct disadvantage of weakening over time because of elastin breakdown. This can lead to eventration, recurrence, or the possibility of pseudorecurrence, which can occur as a result of the weakening of the elastin, increased compliance, and softening of the graft. Methods that are utilized to improve the durability of these grafts are the use of glutaraldehyde and hexamethylene diisocyanate, cross-linking agents which make the material, whether it is human or porcine, more resistant to breakdown by enzymatic degradation. This leads not only to greater durability but also to increasing the susceptibility of these grafts to microbiologic attack. Cross-linking limits the ability of the host to incorporate the graft and make it essentially a part of the native tissue.
The evolution of ventral hernia repair has advanced from open mesh repair to the application of mesh repair to the laparoscopic approach. In this technique, the defect is repaired posteriorly and no dissection within the scarred layer of anterior fascia is required. The laparoscopic approach may also allow for identification of additional hernia defects in the anterior abdominal wall during the repair.
One of the challenging aspects of laparoscopic repair is port access into a peritoneal cavity that has been previously operated upon. In general, access can be obtained for needle insufflation via the left upper quadrant, placing the port along the anterior axillary line to avoid injury to the more laterally positioned spleen. Once insufflation has been achieved and instruments have been inserted, the next challenge is the extensive laparoscopic lysis of adhesions that is often necessary to gain exposure to the entire hernia defect. The goal of the adhesiolysis is to provide a 3–4 cm circumferential area of overlap for the mesh patch beyond the edge of the ventral hernia defect.
After the appropriate adhesions have been taken down and the fascial edges of the defect confirmed, the sac is retracted and excised from within the hernia. The outline of the defect is then drawn on the anterior abdominal wall. Edges of the defect at the skin level can be confirmed from within the abdominal cavity using the laparoscope. The mesh is then cut to fit this defect with a margin of 3–4 cm on each side to provide adequate coverage and to minimize tension. Nonabsorbable sutures are placed around the circumference of the mesh and tied, but not cut. The mesh is rolled so that the anterior surface lies inside the roll, and the mesh is inserted into the abdomen through a large 10- or 12-mm port.
Once inside the abdominal cavity, the mesh is unrolled and positioned. A transfascial suture passer can be introduced through small stab incisions placed around the marked border of the defect. The suture passer retrieves the long ends of the suture that has been previously placed in the mesh, and the ends are tied at the skin level at 4–6 points around the repair and buried with the subcutaneous tissue in the stab incision. This affixes the mesh patch to the fascia layers around the circumference of the patch. After all sutures have been tied and cut, laparoscopically placed tacks or staples can be used to further fasten the mesh to the anterior abdominal wall. Whether the strength of the repair is imparted by the transfascial sutures or the tacks or both remains controversial.
The major complication from open, nonmesh incisional hernia repair is recurrence. Rates of recurrence in this type of repair have approached 30–50% in some series. The risk of recurrence is likely related to the tension placed on the repair in large hernias, and for this reason, incisional hernias with a diameter greater than 4 cm should be repaired with mesh.
Open incisional hernia repairs using mesh can also suffer from hernia recurrence, although the risk is far less than that of the nonmesh technique. Several studies have shown that the risk of recurrence in incisional hernia repair with mesh is approximately 10%. Recurrence in this setting is usually secondary to the appearance of an additional, unrecognized hernia site or an improperly placed prosthesis that pulls away from the fascia edge of the repair. Hematoma or seroma formation may occur in the cavity left behind following a hernia repair. For this reason, closed suction drains may be placed if a large amount of dead space remains following the repair. The drains should be managed judiciously, however, since they may be placed in proximity to the prosthetic mesh, thereby increasing the chance of secondary infection. Wound infection and infection of the mesh can be grave complications, often necessitating removal of the mesh and application of an allogenic tissue graft. Wound infection in open mesh repairs is thought to approximate 5%.
The laparoscopic approach to incisional hernia repair shares the general complications of laparoscopy, including the potential for port-site herniation, vascular injury from trocar placement, and inadvertent bowel injury during laparoscopic adhesiolysis. The mesh placed during laparoscopic repair can also be prone to infection, although the incidence of mesh infection appears to be lower in laparoscopic than open mesh techniques. This may be related to the extensive tissue dissection required to place the mesh in the open procedure. Several nonrandomized studies have shown that the laparoscopic approach is associated with a low incidence of hernia recurrence, in the range of 0–11%.56 Seroma formation in the retained sac above the mesh may occur but usually resolves spontaneously.
There are numerous prospective studies that provide data for the individual techniques, but data are scarce in the comparison between open and laparoscopic mesh repairs for incisional hernia. Nonrandomized, retrospective studies have provided ample evidence that the laparoscopic approach is associated with fewer postoperative complications, a lower incidence of wound and mesh infections, a lower rate of recurrence in long-term follow-up, and shorter in-hospital stays.57 A recent meta-analysis pooled results from five separate randomized controlled trials comparing laparoscopic and open incisional hernia repairs.58 The authors found no significant differences in recurrence rates between the two groups, but the open repair was associated with significantly longer length of stay and postoperative complications compared to the laparoscopic group. Clearly, more studies are required to definitively determine which procedure is optimal; however, at this time both open and laparoscopic techniques appear to be safe and effective in the treatment of incisional hernias.