Core Topics in General & Emergency Surgery: Companion to Specialist Surgical Practice (20 page)
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Authors: Simon Paterson-Brown MBBS MPhil MS FRCS
Aetiology
Incisional hernias are unique in that they are the only hernia to be considered iatrogenic. The cause of wound complications after laparotomy is multifactorial, conditioned by local and systemic factors and by preoperative, perioperative and postoperative factors. Several factors including advanced age, pulmonary disease, morbid obesity, malignancy and intra-abdominal infection are associated with impaired wound healing and predispose patients to serious wound complications such as wound dehiscence, wound infection and incisional herniation. It is always easy to blame the patient for complications! But surgeon or technical factors influencing wound complications include surgical technique and suture material choices.
What is the best way to close the abdominal wall? It is amazing that today we still don't know for sure. A recent review
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proposed mass closure (as compared to layered closure), continuous (as compared to interrupted sutures) absorbable monofilament (as compared to non-absorbable monofilament and absorbable multifilament) with a suture length to wound length ratio of 4:1. However, studies continue to challenge such doctrine. A recent randomised controlled trial (RCT)
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comparing polypropylene to polydioxanone demonstrated no significant difference, and the 4-year incisional hernia rate was 23.7% and 30.2 %, respectively. Another recent RCT
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demonstrated no significant difference between interrupted and continuous sutures. Controversy over the 4:1 ratio also exists. This ratio can be achieved by big bites far apart or small bites close together. A recent RCT
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reported a 50% reduction in wound infection and a 67% reduction in incisional hernia rates in the 2–0 polydioxanone 20-mm-needle small bite arm compared to more conventional closure techniques. Using such a suture technique, suture to wound length ratios greater than 4:1 were not associated with increasing wound complications.
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Further trials are in progress to evaluate this and other techniques in wound closure to minimise the risks of the burst abdomen (sometimes called an acute hernia or deep wound dehiscence), wound infection and incisional hernia. Indeed, incisional hernia is the commonest complication of a laparotomy. The development of an incisional hernia is inevitable if there is separation of the fascia by 12 mm at 12 weeks, so it is not difficult to see that the events that lead to an incisional hernia are determined early in the healing phase, and technical issues are likely to have a significant part to play.
Closure of a laparotomy wound to minimise incisional hernia formation includes:
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mass closure;
simple running technique;
absorbable monofilament;
suture length to wound length ratio of at least 4:1.
The diagnosis of an incisional hernia is usually easy except in the very obsese. However, computed tomography (CT) scanning is helpful to identify the size of the defect and the state of the adominal wall muscles (
Fig. 4.8
).
Figure 4.8
CT scan of a large incisional hernia demonstrating loss of domain. The gap between the medial ends of the left and right recti muscles on this slice is 25 cm.
The large number of surgical procedures described in the literature to repair incisional hernias illustrates that no single technique has stood out as being effective. While 50% of incisional hernias occur within 1 year after the primary operation, 10–18% are diagnosed more than 5 years later. Any study reporting re-recurrence rates following incisional hernia repair should therefore ideally have at least 5 years of follow-up data for analysis. Unfortunately, prospective randomised trials comparing different types of incisional hernia repair are lacking and the majority of studies are retrospective.
As a consequence of the disappointing data on mesh-free repair of incisional hernias, including the Mayo (‘vest-over-pants’) procedure, meshes were introduced to strengthen the abdominal wall repair. Several different techniques were developed: inlay, onlay and sublay (
Fig. 4.9
). Mesh implantation as an inlay does not achieve any strengthening of the abdominal wall and is essentially a suture repair at the muscle/fascia mesh interface. It has the highest recurrence rate of the three techniques. The results of randomised trials comparing mesh to suture repair demonstrate a clear advantage for mesh repair, even for small hernias.
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However, incisional hernia should be considered an incurable disease, mesh just increasing the time from repair to recurrence.
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Although suture repair is now rarely indicated, it might still have a role in young women who wish repair of an incisional hernia but are also contemplating further pregnancy.
Figure 4.9
Cross-sectional appearance of mesh position in incisional hernia repair.
Reproduced from Schumpelick V, Klinge V. Immediate follow-up results of sublay polypropylene repair in primary or recurrent incisional hernias. In: Schumpelick V, Kingsnorth AN (eds) Incisional hernia. Berlin:Springer-Verlag 1999; pp312-26. With kind permission of Springer Science + Business Media.
The onlay technique remains the commonest technique in the West, largely because it is relatively easy to perform. The technique is dependent on closure of the anterior abdominal wall and adequate fixation of the mesh to the fascia and a minimum overlap of 5–8 cm is recommended. If the connection between the mesh and the fascia is lost, a buttonhole hernia develops at the edge of the mesh. Good results can be reported with attention to detail, namely wide overlap of the mesh, and obliteration of large skin flaps with fibrin glue.
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However, for many surgeons the relatively high rate of hernia recurrence, seroma formation and mesh infection make this operation a poor option for the patient.
The sublay technique is the procedure favoured by the author. A mesh in the sublay position is not only sutured into position but is also held in place by the intra-abdominal pressure. Mesh in this position is therefore able to strengthen the abdominal wall both by mechanical sealing and by the induction of strong scar tissue. Several authors have compared the recurrence rate in a single institution where all three techniques have been used.
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Both these studies clearly demonstrate the superior results achieved by the sublay technique.
Open sublay repair:
The sublay operation begins by excising the old scar and performing a laparotomy. Adhesions tend to be maximal at the neck of the sac, so entering the abdominal cavity through the hernia sac is usually straightforward. It is helpful to mobilise adhesions off the underside of the anterior abdominal wall. It is not the author's routine practice to mobilise all the bowel adhesions unless there is a good history of recurrent episodes of obstruction. The sublay space is then developed, which is the space anterior to the posterior rectus sheath, although this becomes pre-peritoneal below the semi-arcuate line. Care should be taken to mobilise the inferior epigastric vessels up with the belly of the rectus muscle to minimise bleeding. It is also important to preserve as many of the intercostal nerves as possible to minimise muscle denervation (
Fig. 4.10
). The pre-peritoneal space can be developed behind the pelvis, akin to a TEP repair, especially if the hernia arises in a Pfannensteil incision. Superiorly, the sublay space can be developed behind the xiphisternum if necessary. The posterior rectus sheath is divided on either side close to the linea alba to expose the area known as the fatty triangle (
Fig. 4.11
). The posterior rectus sheath is approximated with an absorbable suture. The mesh is cut to size, aiming to have at least a 6-cm overlap in all directions. This mesh is sutured to the posterior rectus sheath with interrupted absorbable sutures, avoiding any obvious nerves. These sutures are purely to hold the mesh flat until it is encased in fibrous tissue. A suction drain is often left anterior to the mesh. Any further redundant skin and hernial sac is excised and the anterior rectus sheath closed with an absorbable suture, as is the skin, minimising any subcutaneous dead space. The cross-sectional appearance is illustrated in
Fig. 4.12
. If an abdominoplasty is performed at the same time, then further drains are placed to the subcutaneous space.
Figure 4.10
Fresh cadaveric dissection of the retromuscular space for sublay incisional hernia.
Used with permission of Dr J Conze, Aachen, Germany.
Figure 4.11
Fresh cadaveric dissection demonstrating the fatty triangle by division of the posterior rectus sheath as it attaches to the linea alba. This allows development of the sublay space behind the xiphisternum.
Used with permission of Dr J Conze, Aachen, Germany.
Figure 4.12
(a)
Cross-sectional appearance of peritoneum closure showing the sublay position of the mesh, which is fixed to the posterior sheath of the rectus muscle with an interrupted absorbable suture.
(b)
The anterior and posterior rectus sheath is closed continuously.
Laparoscopic repair:
The laparoscopic (intraperitoneal) approach has also been applied to incisional hernias. The laparoscopic approach has the advantages of shorter hospital stay, lower analgesic requirements, fewer wound complications and an earlier return to normal activities over open surgery. However, while the complication rate is lower overall when compared to surgery, there is concern that when complications do arise with the laparoscopic approach, they are more likely to be life threatening or require further surgery to deal with compared to open surgery.
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Furthermore, the cosmetic result for larger hernias may not be as good as there is no abdominoplasty component to the laparoscopic approach. Remember, the majority of patients wish surgery for their incisional hernia because of the cosmetic deformity rather than symptoms related to the hernia. The author reserves the laparoscopic approach for smaller incisional hernias, with a hernial neck size less than 10 cm and when cosmesis is not an issue. Two current controversies exist in the technique, related to (i) the method of fixation of the mesh and (ii) whether the hernia defect should be closed or not. The method of mesh fixation divides surgeons between those who believe transfascial sutures to be essential to prevent hernia recurrence and those who believe such sutures cause chronic pain post-surgery and their use should be avoided. The author prefers a double-crown tack technique (two rings of tacks around the hernia defect), although there is a lack of quality studies to make this an evidence-based decision. The recent introduction of absorbable tacks may reduce the risk of chronic pain and bowel adhesion to the tacks. Centring the mesh over the hernial defect is important to minimise hernia recurrence. The mesh can be centred with a central stitch,
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although two or four corner sutures are probably more accurate.
What about closure of the defect? Bridging of the defect is recognised to be a problem at open surgery, so why bridge with laparoscopic surgery? It is clear that once adhesions to the abdominal wall are taken down, inserting a mesh and tacking it in place are usually quick and easy. Closing the defect is thus not attractive to the majority of laparoscopic surgeons, introducing tension and perhaps increasing postoperative pain. However, many groups are talking about pseudo-recurrence
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– the redevelopment of a bulge at the hernia site several years after laparoscopic repair as the mesh slides into the hernia sac. Whether closing (either completely or partially) will reduce recurrence and pseudo-recurrence is still unknown but would seem likely.
One of the main long-term risks of the laparoscopic repair of incisional hernias is the placement of the mesh in direct contact with the intra-abdominal structures. As mentioned earlier, the use of meshes that have one side coated with a relatively non-adhesive material will help reduce (but not abolish) adhesion formation to the mesh. The other main risk is infection of the mesh, which is nearly always due to contamination from a bowel injury. Care should be taken with any adhesiolysis to minimise bowel injury with thermal sources such as diathermy and ultracision dissection kept to a minimum. The current consensus is that if the colon is injured, then it should be repaired, laparoscopically or open, according to the skills of the surgeon and no mesh inserted at this time. The patient can return in a number of months for a further attempt at repair. If the small bowel is injured with minimal contamination, then laparoscopic repair, washout and mesh insertion is acceptable. If there is significant small-bowel injury and risk of failure of the bowel repair, then no mesh should be inserted. The patient should be observed in hospital and if they remain well 4–5 days later, then it is appropriate to re-laparoscope the patient and if no continuing contamination/infection is observed, the laparoscopic mesh repair is completed. The use of antibiotic-impregnated mesh may allow a change to this policy with placement of such a mesh at the same time as bowel injury and repair.
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