Efficacy of prophylactic negative pressure wound therapy after open ventral hernia repair: a systematic review meta-analysis

Ventral hernia (VH) is a common complication after abdominal surgery. About 10 to 23% of patients develop incisional hernias [1]. The United States of America (USA) spends more than $3.2 billion per year on surgical treatment of adult ventral hernia [2]. Compared to low body mass index (BMI), patients with obesity have a higher incidence of abdominal wall hernias, larger hernia defects, poorer prognosis, and a higher risk of hernia recurrence. Open ventral hernia repair (OVHR) is favorable for large and complex anatomy due to advantages, such as clear anatomy, low operation difficulty, low effect of obesity, short anesthesia time, and low impact on intestinal function [3]. However, the potential dead space and mesh after OVHR can easily lead to surgical site occurrence (SSO), including surgical site infection (SSI), wound dehiscence, seroma, hematoma, skin necrosis, and hernia recurrence [4]. SSIs and other complications may further lead to extended hospital stays, delayed recovery, increased psychological stress, and higher treatment costs [5]. Some factors associated with SSI include weakened immunity, poor nutrition, advanced age, diabetes, use of corticosteroids, and incarcerated hernia. Therefore, breakthrough techniques in surgery are a priority for patients with high-risk factors for SSI.

Negative pressure wound therapy (NPWT) is a widely used wound care technology, mainly for soft tissue trauma and fracture [6]. NPWT includes a drainage system involving the wound dressing and its connected device. By applying negative pressure ranging from − 75 mmHg to − 150 mmHg, any wound and tissue fluid drawn from the area is collected into the vacuum device [7]. Negative pressure suction devices can be used in several ways. Their advantages include removing wound exudates, promoting apposition of the skin edges, changing the microenvironment and stimulating the formation of granulation tissue, and new blood vessel formation [8]. NPWT has been shown to reduce the incidence of complications in various primary closures [9]. However, the efficacy of NPWT after OVHR is unclear. The main purpose of our systematic review is to highlight the effect of prophylactic negative pressure wound therapy (pNPWT) in preventing SSO. The secondary outcome was the incidence rate of other complications.

Overall, a total of 476 studies were identified from the databases. Fifty full texts were then shortlisted based on title and abstract analysis, of which 15 articles finally met the inclusion criteria. The specific inclusion process flowchart is shown in Fig. 1. A total of 1666 patients were included in the selected articles, of which 821 patients underwent pNPWT.

The general characteristics of the articles included in the meta-analysis are shown in Table 1. The sample size of these studies ranged from 35 to 180 and the maximum follow-up duration varied from 30 days to 38.5 months. Most of the studies were retrospective cohort analyses and only 2 were RCTs. PREVENA was the most widely used pNPWT device for OVHR. PREVENA was used and described in eight articles. The negative pressure applied to the incision varied from − 75 mmHg to − 125 mmHg.

VHR is a common surgical procedure, with more than 400,000 surgeries performed in the USA alone annually [26]. Laparoscopic VHR is becoming a general trend due to its lower perioperative complication rate, shorter hospital stays, and lower postoperative readmission rate [27]. Regardless of the surgical method (whether open or endoscopic), postoperative complications remain a challenge for surgeons. Without a doubt, the outcomes could be extremely complex, leading to increased medical costs to patients and hospitals.

NPWT is commonly used to treat open wounds in the abdomen in combination with lavage, debridement, and bowel resection as indicated [28]. Since its introduction in 1997, NPWT has been shown to be effective in both open and postoperative closed wounds [29]. However, the efficacy of pNPWT in wound healing after OVHR is unclear and data are contradictory in the literature [30]. In the earliest RCT in 2020 including 150 patients, Bueno-Lledó et al. showed that the incidence of SSO in the control group (standard dressing; 22/74, 29.8%) was significantly higher than that in the NPWT group (12/72, 16.6%, P < 0.05) after 30 days of postoperative follow-up [31]. Deldar et al. found that NPWT had no effect on the prevention of SSO (23.2% vs 26.3%, P = 0.663) [23]. In addition, the two RCTs to date have different results in the SSI study [11]. The existing related studies were mostly retrospective cohort studies or case series. We analyzed 15 articles and the results of the meta-analysis from all included studies showed that pNPWT significantly reduced the risk of SSO, SSI, wound dehiscence, and the rate of hernia recurrence (P < 0.05). Meanwhile, there was no significant difference in seroma, hematoma, and skin necrosis with pNPWT compared to standard wound dressings.

It is worth noting that with the addition of a recent RCT, we obtained the same results for SSO as in the previously published meta-analysis articles [32]. Nevertheless, a high degree of heterogeneity (I² = 87%) is seen in the SSO results. Further subgroup analysis suggested that the heterogeneity stemmed from differences in dressings and the quality of studies. The probable reason for the difference in the test results is variations in the diagnostic methods and surgeon-dependent definition of SSO and operation level. However, due to the small number of studies, we did not use the traditional funnel plot for analysis of publication bias. Also, Egger’s test results revealed no publication bias in SSO. No high heterogeneity was found in the analysis of SSI, seroma, hematoma, wound dehiscence, skin necrosis, and hernia recurrence.

NPWT has been shown to have a crucial role in scar healing following OVHR [33]. NPWT can enhance wound drainage, eliminate bacterial byproducts, discharge secretions efficiently, and clear necrotic tissue [34]. Under the mechanical traction of negative pressure, the differential pressure between the inner and outer capillaries and the endothelial cell space of lymphatic capillaries increases, resulting in elevated levels of blood supply and lymphatic reflux [35‐37]. Compared with conventional dressings, a negative pressure provides effective and sustained support for local wound circulation, thereby reducing the risk of seroma and hematoma [11, 38]. Furthermore, continuous negative pressure extracts interstitial fluid from the wound, fosters growth of capillaries and granulation tissue, improves blood circulation, and accelerates scar healing [39, 40]. Through these mechanisms, NPWT lowers wound healing time and enhances scar recovery significantly. Additional studies are required to further understand the mechanism of NPWT in OVHR.

However, NPWT may entail certain complications, such as skin blisters [33], which typically resolve spontaneously within approximately a week [41]. Improper usage of NPWT has the potential to result in more severe complications, including skin necrosis, bleeding, and allergic reactions [42, 43]. It is imperative to discontinue NPWT in case these complications occur. Nevertheless, studies indicate that there is no noteworthy increase in the incidence of wound-related adverse events associated with NPWT when compared to standard dressings [44]. Appropriate preventive measures may help mitigate adverse events [45].

There are some limitations of this meta-analysis. First, most studies involved in this meta-analysis were retrospective and only two RCTs were included, which may introduce a selection bias in the process [46]. Second, the definition of SSO was different among articles. Most authors defined SSO as surgical site infection (SSI), wound dehiscence, skin necrosis, seroma, and hematoma. Seaman et al. believed that enterocutaneous fistula, mesh infection, hernia recurrence, and/or 30-day bulge are considered when detecting SSO [30], which is bound to make a difference to the SSO results. Third, there is a lack of standard diagnostic criteria and follow-up time for complications occurring in these studies. For example, seroma was diagnosed clinically or using ultrasound, with significantly different incidences. Further, the shortest follow-up period was 1 month, while the longest follow-up period was 38.5 months. Fourth, most of the articles did not report any recurrent hernias or emergency hernias, which might also affect the occurrence of SSO. Finally, there was no standard for the defect range in the included articles. Only a few studies used the defect size or European Hernia Society (EHS) classification. The guidelines of the International Endohernia Society (IEHS) also clearly state that abdominal wall defects are closely related to postoperative SSO and the recurrence of hernia [47]. This also requires newer studies to further verify how large a defect is suitable for placing pNPWT.

Certainly, if only the device cost is considered, the cost of closing surgical wounds with NPWT is higher than that with traditional dressings. In the study by Clare et al., after accounting for postoperative complications and hospitalization costs, a cost-benefit analysis showed an estimated total cost reduction of €170,944.00 in 100 people treated with closed incision negative pressure therapy (ciNPT) compared to standard wound care [15]. Svensson-Björk et al. concluded that NPWT can reduce the incidence of SSI, which was more cost-effective than standard dressings; the average cost increase was €1853 after following patients for 90 days following open inguinal vascular surgery [48]. Considering the cost of analgesics, antibiotics, hospitalization, and morbidity, Condon et al. concluded that the cost of satisfactory healing in people who received NPWT was lower compared to conventional dressing for the treatment of wounds due to diabetic foot [19].

Our review concludes that the use of pNPWT after OVHR can reduce the incidence of SSO and SSI, wound dehiscence, and hernia recurrence simultaneously. Prophylactic NPWT has no obvious effect on other complications, such as seroma, hematoma, and skin necrosis. However, the large heterogeneity of studies regarding SSO is a limitation of the review, possibly due to differences in article quality and NPWT techniques. There is an urgent need for higher quality, better-designed RCTs with consistent standards to further verify the efficacy of pNPWT following OVHR.