Abdominal wall closure

Intra-abdominal surgery necessitates access to the abdominal cavity. This can be achieved through a variety of different incisions, including median, paramedian, and transverse approaches. Use of the avascular linea alba is a fast way to gain access to the abdominal cavity, an important advantage in emergency settings. Furthermore, it affords access to all corners of the abdominal cavity and the incision can be lengthened if required, based on intraoperative findings. Abdominal surgery is associated with risk of incisional herniation, occurring in 13 per cent of patients at 2 years after surgery, although the incidence increases to 30 per cent in high-risk patients1–3. Surgical-site infection and fascial dehiscence are both independent risk factors for the development of an incisional hernia4,5. Avoiding the midline laparotomy, if possible, or a midline extraction site in the case of a laparoscopic procedure has been shown to considerably reduce incisional hernia rates6,7. An incisional hernia carries with it the subsequent risk of emergency presentation with bowel incarceration and bowel ischaemia. Furthermore, an incisional hernia can have a significant impact on a patient’s quality of life due to bulging, discomfort, pain, and cosmetic concerns8. A French study concluded that prevention of 5 per cent of incisional hernias would result in a reduction in healthcare costs of 4 million euros per year9. There has been a recent focus on the prevention of incisional hernias through improvements in the technical aspects of abdominal closure. This article discusses these technical aspects, providing a foundation for clinical practice. The mechanical physiology of the abdominal wall is complex due to its three-dimensional configuration and tissue composition. It can be roughly explained by the Laplace formula, assuming the abdominal cavity is a cylinder. The Laplace formula dictates that the stress applied on the abdominal wall is the product of intra-abdominal pressure and the radius of the cylinder10. Normal intra-abdominal pressure ranges from 16.7 to 20 mmHg when sitting and standing respectively11. Focusing on the linea alba, two directions of force are recognized, a transverse force and a longitudinal force, with the transverse force being considered greater than the longitudinal force10. These forces applied to the abdominal wall are enhanced by patient-related factors, such as obesity, ascites, pregnancy, and coughing associated with smoking, all of which are associated with incisional hernia occurrence12–16. So, it could be argued that preventing postoperative complications involving vomiting and coughing, such as small bowel obstruction, ileus, and pneumonia, would prevent high intra-abdominal pressure and reduce the risk of incisional herniation. Maximal healing of the fascia takes 1–2 years and closely resembles wound healing. This complex process is divided into four phases (the coagulation and haemostasis phase, the inflammation phase, the proliferation phase, and the remodelling phase)17. Only 50 per cent of the strength of the fascia is restored after 2 months and it needs a total of 4 months to regain most of its original strength18. Restoring the ability of the abdominal wall to withstand normal physiological forces as discussed earlier, is the goal of abdominal wall closure. Therefore, suture reinforcement should bridge the interval of at least 3 weeks up to 2 months needed for the fascia to heal and regain sufficient strength. The strength of the healed fascia is dependent on collagen deposition, in particular the collagen I/III ratio. During the proliferation phase, in the first 3 weeks after surgery, an extracellular matrix is formed together with collagen III, consisting of thin weak fibres. After 3 weeks, collagen III is converted into collagen I, a stronger and thicker type of collagen, in the following maturation phase19. The most important risk factor for disruption of the beforementioned process is smoking, but obesity, surgical-site infection, and congenital collagen disorders are also associated with divergent collagen deposition at a molecular level20. A decreased collagen I/III ratio, in general, increases the incidence of hernias and recurrence after hernia repair21. A wide range of suture materials for closing the abdominal wall are available. These can be categorized according to the characteristics of the material, such as absorbability and whether it is a monofilament or multifilament thread. Most of the fast-absorbable sutures that are used consist of polyglycolic acid (that is Dexon® or Polysorb®) or polyglactin (that is Vicryl® or Novosyn®) and all have a half-life tensile strength of around 2 weeks. Polyglyconate (that is Maxon®) and polydioxanone (that is PDS® or Monoplus®) have a half-life tensile strength of 3 and 6 weeks respectively and are considered slowly absorbable22. Based on the available evidence, no strong relationship between suture type and the incidence of incisional herniation has been established23,24. Considering the healing process of the fascia and the time needed to regain its load-bearing function, the strength of the abdominal wall is mostly dependent on suture reinforcement for the first 3–8 weeks. With this concept in mind, a slowly absorbable suture is the sensible choice for fascia closure and thus is supported by current guidelines25. The risk of using fast-absorbable sutures is that such sutures fail to support the abdominal wall until it is self-sufficient, especially in cases complicated by surgical-site infection. Non-absorbable sutures provide long-term support of the fascia, but can cause suture sinus and fistula formation and are therefore not recommended23,24. Besides absorbability, the structural make-up of the thread is an important characteristic of a suture. A single-thread suture is called a monofilament suture; this differs from a multifilament suture, which consists of multiple threads braided into one suture. The use of monofilament sutures for the closure of midline laparotomies decreases the risk of incisional hernia occurrence23. Multifilament sutures are thought to increase the risk of surgical-site infection, which is an independent risk factor for an incisional hernia. The capillarity and the ability for bacteria and fluids to pass through a multifilament suture is thought to increase the risk of surgical-site infection. However, in large meta-analyses, no differences in surgical-site infection after closure of the abdominal wall were found between monofilament and multifilament sutures23,24. The needle size should be considered when closing the abdominal fascia. Although evidence regarding the relationships between needle size and sharp-tip versus blunt-tip needles and incisional hernias is absent26, it is hypothesized that a large needle will result in a large hole in the fascia, which could negatively influence fascia strength. It is recommended to use a small single thread, size 2-0 to be specific, for closure of the abdominal fascia25. Using a looped suture would result in leaving more foreign-body material than necessary. Aiming to reduce surgical-site infection, and consequently incisional herniation, antimicrobial-coated sutures are available. Non-absorbable, slowly absorbable, and fast-absorbable sutures coated with a bactericidal agent called triclosan are beneficial in reducing surgical-site infection, especially in abdominal procedures27. The use of antimicrobial-coated sutures has not, however, been shown to decrease the incidence of incisional hernias25. Multiple techniques for abdominal wall closure have been described and the associated risk of incisional herniation has been studied. The techniques include interrupted and continuous suturing; the continuous technique has the advantage of being less time-consuming and leaves less foreign-body material in situ. In one meta-analysis, continuous suturing resulted in less incisional herniation28. However, comparing these two techniques in a meta-analysis is associated with the problem of heterogeneity, with fast-absorbable, slowly absorbable, and non-absorbable sutures as the main confounding factor. When only comparing the techniques when using the same suture material for both techniques, no significant differences were found between interrupted and continuous suturing23,29. Current guidelines recommend the use of a continuous suturing technique to minimize the presence of foreign-body material from multiple knots and to better divide tension along the suture line25. A mass closure technique incorporating fatty tissue and muscle in the suture is not recommended. High tension results in diminished perfusion of the incorporated tissue, resulting in possible ischaemia and necrosis of the tissue30. Subsequently, this leads to slacking of the suture and seroma formation, possibly giving rise to surgical-site infection. Therefore, it is recommended to use an aponeurosis-only closure technique, because the aponeurosis is far better equipped to withstand force25. The STITCH trial showed a reduction in incisional hernias, from 21 to 13 per cent respectively when comparing the large bites technique with the small bites technique31. The small bites technique consists of tissue bites of 5 mm, only involving the aponeurosis, with an inter-suture space of 5 mm. A suture length to wound length ratio of at least 4 can be achieved in this manner32 (Video S1). Monofilament sutures, in particular PDS 2-0 sutures, are recommended for closing the abdominal wall. However, a technical issue arises, as monofilament sutures are more difficult to tie and have a higher tendency to slip. The quality of the surgical knot starting and finishing the suture line is critical to the strength of the abdominal closure. The difficulties of knotting monofilament sutures are overcome by using self-locking knots. Sutures with traditional knots lose 40 per cent of their strength, compared with only 5–10 per cent when using self-locking knots33,34. The starting knot, or fishermen’s knot, is demonstrated in Video S2 and the finishing knot used (commonly referred to as the Aberdeen knot) is also used when closing the skin intracutaneously (demonstrated in Video S3). As surgical-site infection increases the risk of incisional herniation, optimal closure of the skin and possibly the subcutaneous tissue should be focused on to reduce hernia risk. The subcutaneous tissue should only be closed when a large dead space is left behind that could increase the risk of seroma and surgical-site infection. No difference in surgical-site infection has been found when either subcuticular sutures or staples are used to close the skin, but cuticular sutures result in less postoperative pain and a more favourable cosmetic outcome35. In addition, prophylactic or closed-incision negative wound pressure therapy is advised to decrease the occurrence of surgical-site infection after surgery, mainly by reducing the dead space. Low-quality evidence shows a significant reduction in surgical-site infection when using prophylactic negative wound pressure36. Based on current guidelines, research, and expert opinions, it is recommended to close the abdominal wall with a slowly absorbable suture, in a continuous fashion, using the small bites technique incorporating only the aponeurosis, starting and finishing with a self-locking knot. The authors have no funding to declare. Sebastiaan van Steensel (Conceptualization, Data curation, Writing—original draft, Writing—review & editing), Eva B. Deerenberg (Conceptualization, Resources, Writing—review & editing), and Marijn M. Poelman (Writing—review & editing). E.B.D. has received consultancy fees from Medtronic and Mellon Medical and has received a research grant from Ethicon. The authors declare no other conflict of interest. Supplementary material is available at BJS online.