1 Surgical Anatomy

A clear understanding of the anatomy of the abdominal wall is critical when performing a component separation operation. The two vertically oriented rectus abdominis muscles, with their overlying anterior rectus sheaths should normally lie side by side in the midline. In between the rectus muscles is the tendinous linea alba, which functionally is actually the tendinous insertion of the fascial extensions of the six lateral abdominal wall muscles (bilateral external oblique, internal oblique, and transverses abdominis). A midline incisional hernia is caused by a disruption of the linea alba, which in turn leads to unopposed contraction of the lateral abdominal wall muscles. It is this constant unopposed pull from the lateral muscles in combination with intraperitoneal pressure that leads to the gradual increase in size of these hernias and ultimately loss of abdominal domain. The position of the arcuate line is also important to understand. The arcuate line lies approximately three fourths of the way from the pubis to the umbilicus, or to use a bony anatomic landmark, approximately 2 cm cephalad to a line drawn between the two anterior superior iliac spines. Below this line there is no posterior rectus sheath (Cunningham, 2004). There is also a small triangular muscle called the pyrimidalis that overlies the most inferior portion of the rectus muscles just as they attach onto the pubis. This muscle is not relevant clinically.

The main blood supply to the rectus abdominis muscles is from the superior and inferior epigastric arteries, with the inferior epigastric being more dominant. The entire muscle can easily survive however on either blood vessel. There are additional vascular contributions from the intercostal arterial branches that come in laterally in a segmental fashion. The blood supply to the lateral musculature comes from intercostal branches that travel deep to the internal oblique muscle in the so-called neurovascular plane. In this plane are also the nerves to the abdominal wall that are branches of the lower six thoracic and the first lumbar segmental nerves.

2 Preoperative Considerations

The preoperative evaluation should include a complete medical history that includes any operative reports from previous operations. In cases where there have been previous hernia repairs, it is important to know what type of mesh repairs have been done, including the specific brand of mesh and the plane in which the mesh was placed and whether or not a component separation has been previously attempted. It should be noted in the history whether or not there were wound complications or infections after any of the previous operations.

Certain comorbidities are associated with higher rates of complications, and if any of these comorbidities can be managed before the surgery, every effort should be made to do so. Examples include losing weight, controlling diabetes, quitting smoking, maximizing nutritional status, maximizing a patient’s cardio/pulmonary health, and taking appropriate prophylactic measures for thromboembolic disease.

It should be noted that in many circumstances, although patients can be quite miserable, incisional hernia repairs can be categorized as elective surgery. Those patients with hernia defects with a very wide base are at a low risk for bowel strangulation and obstruction. In patients like this, with non–life-threatening hernias, where the extent of their comorbidities carry an unacceptably high mortality risk, surgery should be avoided. One particular comorbidity, that of being super-obese (body mass index [BMI] >45), in addition to other general morbidities, carries a very high risk of hernia recurrence, reported to be as high as 50% (Vargo, 2008). In these patients, the risk-to-benefit scale is certainly tilted toward risk, and a serious effort at weight loss should be attempted before opting for elective surgery.

3 Operative Steps

The first step in performing a component separation is lysis of adhesions from the bowel to the undersurface of the abdominal wall. This allows for a good underlay of any mesh that may be used but also helps to untether the abdominal wall musculature and allow it to advance toward the midline. The next step is identification of the healthy fascial edges. This is performed by undermining the skin and subcutaneous fat until healthy rectus abdominis anterior fascia is identified. It is important to do this very carefully and avoid getting underneath the anterior rectus fascia. It is also important not to confuse dense scar tissue from healthy fascia, which is a common mistake that leads to recurrence over time as that dense scar tissue slowly remodels and ultimately gives way. In the case of skin graft or secondarily healed scar on top of bowel there are two options. One option is to remove the skin graft or scar completely with sharp dissection. This can sometimes be difficult and may lead to enterotomies. If it becomes clear that this technique is too risky, then another option is to leave the skin graft or scar on the bowel and simply de-epithelialize it. This is done with a number 10 scalpel blade by tangentially shaving off the epidermis, leaving what is left of the dermis or the scar tissue behind. At the periphery, the normal skin and subcutaneous fat can be undermined in the usual fashion until healthy fascia is identified.

Once the fascia is identified, undermining should continue until the lateral edge of the rectus abdominis is identified. This often can be visualized; however, a better way to find it is to pinch the abdominal wall musculature by placing the hand and fingers intraperitoneally with the thumb above the fascia and feeling for the thickening of the edge of the rectus muscle while the hand is slid medially. Some descriptions of open component separation describe continuing to undermine the skin all the way to the anterior axillary line. In my opinion this is not necessary and only leads to more risk for wound complications. I believe the undermining of the skin should end just at the point of where the external oblique fascia is divided.

A small nick in the external oblique fascia should then be made just 1 cm lateral to the lateral aspect of the rectus abdominis muscle. If the surgeon notices that there are still vertically oriented muscle fibers under the fascia, then the nick has been made too medial and another nick should be made a centimeter or so more laterally. Once the incision in the external oblique fascia is made, it is important to carry this incision all the way to just below the hernia defect (stopping short of the inguinal ligament) and all the way up over the costal margin superiorly. Generally, when going over the costal margin, the surgeon is dividing not only the fascial aponeurosis, but the actual muscle fibers of the external oblique muscle itself. It is important to completely transect these external oblique muscle fibers high up at the level of the costal margin. This allows for a much easier closure in the epigastric area. Figure 8-1 shows the division of the external oblique fascia just lateral to the lateral edge of the rectus abdominis muscle. Figure 8-2 is an intraoperative photograph showing the division of the external oblique fascia. In this photo, the rectus abdominis muscles have already been sutured together.

Figure 8-1

Figure 8-2

Once the external fascia is divided on both sides, the surgeon should assess the tension on the closure and whether or not the fascia will actually come together in the midline. A few additional maneuvers can then be attempted if there is still more advancement required to get a closure without undue tension. The next maneuver is to actually undermine the external oblique fascia/muscle all the way to the anterior axillary line. One must be careful to stop short of the blood vessels supplying the external oblique. If this is not enough, the last maneuver is to enter the medial edge of the rectus sheath and lift the muscle off of the posterior rectus sheath. This last step is only minimally effective in most cases, adding perhaps 1 to 2 cm of advancement on each side, with the exception of those cases where the rectus abdominis muscles have become tubularized.

In those cases where the rectus muscles will come together in the midline, I then proceed with performing a running closure with a #1 size loop suture made of monofilament slowly resorbable material (polydioxanone). In those situations where the fascial edges do not come together (which occurs less than 15% of the time in my practice), then a fascial bridge must be performed with some sort of mesh placed as an underlay. In this circumstance, the mesh must be placed in the intraperitoneal position, underneath the fascia and all the way to approximately the lateral edge of the rectus abdominis. Synthetic mesh should be avoided in circumstances where there is bacterial contamination or infection and also in those patients where comorbidities put the patient at an unacceptably high risk for developing a surgical site infection or wound breakdown. For those patients where synthetic mesh is undesirable, a biologic material should be used. It is important to note that there is a large and at times overwhelming variety of synthetic and biologic materials available to surgeons today, many of which have little in the way of data to support their use. Surgeons should obviously base their decision for material selection on the best available data at the time of use.

When the muscles do reach together in the midline, and are able to be closed primarily, a reinforcing material (synthetic or biologic as discussed in the previous paragraph) should be placed either as an underlay or as an overlay to reduce the risk for recurrence. It is my preference to place the material as an overlay. I prefer the overlay because it allows me to reinforce not only the midline repair, but the lateral areas of the abdominal wall where the external oblique has been divided. I run the material along the cut lateral free edge of the external oblique fascia. I then pull the material taught across the midline and suture it with another running suture to the cut lateral edge of the opposite external oblique fascia under physiologic tension. It is important that this be under some tension and not completely loose so that it will off-load some of the tension on the midline repair. This added layer reinforces not only the midline but also the two lateral areas where the external oblique has been cut. Furthermore, by placing the material under some tension it re-medializes the two external oblique muscles that otherwise retract laterally and become useless. By effectively reinserting the two external muscles across the midline to one another it allows these muscles to continue to act as functional muscle units. It is important to quilt the material down to the anterior abdominal wall (Figs. 8-3, 8-4, and 8-5). This is done with size 0 polydioxanone suture. These quilting sutures must be placed only over the top of the rectus abdominis muscles because they are placed in a blind fashion. The needle is placed through the onlay material, then placed in a skiving fashion through the anterior rectus fascia and then brought back up through the implant material. This is safe as long as the rectus muscle is present. Laterally, the abdominal wall may be too thin to safely place these sutures without risk of entering the peritoneal space. The quilting sutures are important to place because they further offload tension from the midline by further distributing the tension and they prevent seroma formation between the implant material and the fascia, allowing vascular ingrowth into the material more readily. Our group has recently reported a 7% recurrence rate with a mean follow-up of 1 year in 60 consecutive patients using this technique (Stromberg, 2010).

Figure 8-3

Figure 8-4

Figure 8-5

One of the negatives of performing the open component separation technique is the risk of wound complications; however, several techniques can be used to minimize wound breakdown. Already mentioned is limiting the undermining of the skin and fat to only just lateral to the rectus abdominis muscle. Additional maneuvers include excision of any redundant skin and fat. Sometimes this requires a formal panniculectomy, and sometimes it is simply a matter of removing a few centimeters of skin and fat from each side of the incision. Next, for the remaining skin flaps, it is important to remove any sub-Scarpa fat. This is particularly important in patients with thick subcutaneous layers. This deeper fat is generally ischemic, and leaving it puts the patient at risk for fat necrosis and therefore at risk for seromas and wound infections. Next is the suturing down the skin flaps to the abdominal wall. These quilting sutures reduce dead space and help reduce the risk for seromas. Perhaps most important is the liberal use of drains. I put at least two but up to four 19-French round fluted drains. I never remove them during the patient’s hospitalization and never sooner than 1 week after the procedure. After 1 week, I like to see <30 mL/drain/24-hour period for at least 2 days in a row before pulling out the drain. Typically, drains are removed in the 2- to 4-week range, but sometimes the drains are left in as long as 6 weeks.

A final maneuver that has helped with wound breakdown in my practice is the use of negative pressure therapy over the top of my closed incision. I perform an intradermal or subcuticular closure with resorbable sutures and then place a nonadherent porous dressing over the top of the suture line. On top of that I place the foam and the adhesive layer and place the dressing on negative 125 mm Hg suction. This dressing draws away any drainage from the suture line, but more importantly, it draws blood flow to the wound edges and reduces edema while mechanically pulling together the skin edges and stabilizing the suture line. This dressing is left in place for the patient’s entire hospitalization (up to 8 days). This has remarkably improved outcomes in even the most challenging large panniculectomy incisions.

4 Postoperative Considerations

Postoperatively, I do not tend to use abdominal binders until after the drains are removed. I am concerned that a binder being placed two tightly may interfere with skin perfusion, may irritate the suture line as well as the drain exit sites. Once the drains are removed, I have the patient wear the binder at all times (except when showering) for a period of 6 weeks. After this I tell the patients to continue to wear the binder whenever they are doing anything even moderately strenuous for the rest of their lives.

Patients are instructed to not lift anything heavier than their shoes for 6 weeks post operatively. After that, I explain to patients that they always have a risk of recurrence and so they should alter their lifestyles if they want to help reduce that risk. I recommend that they avoid heavy lifting if at all possible, even if that means changing occupations. They can resume moderate aerobic type exercise such as walking or bicycling, however they should never perform sit-ups or weight lifting.

5 Pearls and Pitfalls

One major pitfall is failure to identify the healthy medial edge of good fascia. Scar tissue, although it may seem strong at the time, will ultimately fail and lead to recurrence. Excessive undermining of the skin and fat also is a pitfall than can lead to ischemic skin edges and fat and wound complications. Finally closing the fascia under too much tension is another key pitfall. It is tempting to force together the fascial edges when they are very close but in time this will often lead to a recurrence. It is better to leave the edges apart and use an underlay technique to bridge the gap then to truly force together the fascial edges. Unfortunately the question of how tight is too tight is only answerable at this time with surgical judgment that comes from experience. One pearl that has given me additional fascial advancement when needed is the maneuver of undermining the external oblique fascia laterally, all the way to the anterior axillary line. Keep in mind that the fascia stays attached to the overlying fat to avoid devascularization of the fat. Also, a considerable amount of medial advancement of the fascia in the epigastric area can be achieved by carrying the division of the external oblique fascia over the costal margin. Finally, many of the potential negatives of the open component separation technique, such as wound problems and seromas, can be mitigated by proper management of the skin flaps. A summary of this management includes minimizing skin undermining to just lateral to the rectus muscles, excision of redundant skin and fat before closure, removal of sub-Scarpa fat from the remaining skin flaps, liberal use of drains, quilting down the Scarpa fascia to the abdominal wall, and the use of negative pressure therapy on top of the closed incision. With these techniques, the wound complications and seroma problems have become minimal in my practice.

Disclosure Statement

Dr. Silverman is the Chief Medical Officer and Sr. Vice President of KCI Corporation, of which LifeCell Corporation is a division. Elsevier does not endorse any products or services of KCI Corporation.