Effectiveness of Negative Pressure Wound Therapy in Patients With Challenging Wounds: A Systematic Review and Meta-analysis (original) (raw)

Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis

Kylie Sandy-Hodgetts, BSc, MBA 1{ }^{1}
Robin Watts, AM, PhD, MHSc, BA, DipNEd, RN, FRCNA 1,2{ }^{1,2}

1. School of Nursing and Midwifery, Curtin University, Western Australia
2. The Western Australian Group for Evidence Informed Healthcare Practice: an Affiliate Center of The Joanna Briggs Institute

Corresponding author:

Kylie Sandy-Hodgetts
kylie.sandy-hodgetts@curtin.edu.au

Executive summary

Background

The treatment of post-surgical wound complications, such as surgical site infections and surgical wound dehiscence, generates a significant burden for patients and healthcare systems. The effectiveness of negative pressure wound therapy has been under investigation but to date no systematic review has been published in relation to its effectiveness in the prevention of surgical wound complications.

Objectives

To identify the effectiveness of negative pressure wound therapy in the prevention of postsurgical wound complications in adults with a closed surgical incision compared to standard surgical dressings.

Inclusion criteria

Types of participants

Male and female adults who have had negative pressure wound therapy applied to their surgical incision following a procedure in one of the following areas: trauma, cardiothoracic, orthopedic, abdominal, or vascular surgery.

Types of intervention

The intervention of interest was the use of negative pressure wound therapy directly over an incision following a surgical procedure; the comparator was standard surgical dressings.

Types of studies

Both experimental and epidemiological study designs, including randomized controlled trials, pseudo-randomized trials, quasi-experimental studies, before and after studies, prospective and retrospective cohort studies, case control studies, and analytical cross sectional studies were sought.

Types of outcomes

The primary outcome was the occurrence of post-surgical wound infection or dehiscence as measured by the following: surgical site infections - superficial and deep; surgical wound dehiscence; wound pain; wound seroma; wound hematoma.

Search strategy

Published and unpublished studies in English from 1990 to 2013 were identified by searching a variety of electronic databases. Reference lists of all papers selected for retrieval were then searched for additional studies.

Methodological quality

Papers selected for retrieval were assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument.

Data collection

Data were extracted from the included papers using a standardized data extraction tool from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument. In addition to study results, the data extracted included details of the study population, setting, intervention and author’s conclusion.

Data synthesis

Where appropriate, data were pooled using Comprehensive Meta-Analysis software. Metaanalyses were performed for three outcomes. In cases of heterogeneity between studies a narrative summary of results was undertaken.

Results

Eight studies were included in the review. Meta-analyses revealed a statistically significant difference in favor of the use of negative pressure wound therapy as compared to standard surgical dressings was found for surgical site infections. Conflicting results were found for wound dehiscence and seroma.

Conclusions

Given the small number of studies, mostly retrospective comparative cohort in design, no definitive conclusions can be reached as to the effectiveness of the use of negative pressure wound therapy in the prevention of surgical wound complications. However, there was a demonstrated association between the use of negative pressure wound therapy and reduction in surgical site infection.

Implications for practice

Negative pressure wound therapy in preference to standard postoperative dressings, for example dry gauze, may be considered for closed surgical incisions in adults assessed as high-risk for surgical site infections.

Implications for research

The focus of further research on this topic should be level one studies (randomized controlled trials) on patients identified as ‘at risk’ in the preoperative period.

Keywords

Negative pressure wound therapy; topical negative pressure; wound healing; prevention of wound complications; wound dehiscence; surgical site infection

Background

The worldwide volume of surgery is considerable, with an estimated 234.2 million major surgical procedures carried out every year across the globe. 1{ }^{1} In Australia during 2010-11, 2.4 million admissions involved a surgical procedure. 2{ }^{2} Wound healing by primary intention following surgery is assisted by the use of sutures, staples, glue, adhesive tape wound dressings or negative pressure wound therapy (NPWT), and healing commences within hours of closure. 3{ }^{3} Failure of the wound to heal may be due to a number of reasons: patient related factors, for example age, cardio-vascular disease; 4,5{ }^{4,5} technical reasons of suture breakage or knots slipping; 6{ }^{6} infection or dehiscence 4,5,7,8{ }^{4,5,7,8} or compromised immunity.

Currently there are differences in the reporting of surgical wound dehiscence, primarily due to the type and frequency of the classifications used. As a result, attempts at determining the incidence of surgical wound dehiscence (SWD) on a local and global level are often thwarted. Surgical wound complications are often reported as a surgical site infection (SSI) and/or more seriously a wound breakdown (also known as wound dehiscence), which is where the wound has separated at the margins within a 30-day period following surgery. This may be due to infection, patient-related or mechanical factors such as those described above. However, SWD is also defined by the Centers of Disease Control and Prevention (CDC) 9{ }^{9} as a deep SSI, and is the most widely referred to classification by clinicians. Surgical wound breakdown in this context is known as a deep or organ space infection, and this definition only accounts for microbial causes for the wound breakdown, not non-microbial causes such as patient-related factors. The CDC definition is not consistently used by all when reporting surgical wound complications and this complicates the process in determining incidence and prevalence of SWD.

In the United Kingdom, SSI constitutes 20% of all health care related infections, and at least 5% of admitted patients will develop an SSI. 10{ }^{10} In North America, the fiscal estimate of SSI is reportedly USD 10 billion annually in direct and indirect medical costs. 11{ }^{11} The estimated costs attributable to SSI in Europe range from 1.47 to 19.1 billion Euros. 10{ }^{10} In Australia, estimated costs associated with SSI are AUD60 million per year. 12,13{ }^{12,13} Estimating the economic impact of SWD is speculative at best, as for each of these geographical areas it is difficult to ascertain how many surgical site infections are superficial or deep, or a wound dehiscence. However, further additional costs associated with delays in healing and reduced quality of life for the patient, family, and the wider community is also difficult to

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1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

ascertain from a fiscal point of view. More importantly, the use of an optimal therapy to improve wound healing outcome following surgery and prevent wound complications remains to be determined.

Negative pressure wound therapy has been in use since the 1990s. 14−16{ }^{14-16} This review considers studies that evaluate the use of NPWT following surgery and the occurrence of wound complications, such as SSI and SWD. Research into the use of NPWT has determined that its therapeutic effects include reduction in edema, increase in skin perfusion 17−19{ }^{17-19}, and increased granulation tissue formation. 20{ }^{20} NPWT is a mode of therapy used in wound care and consists of a device (pump) attached to a dressing via tubing placed over a wound using a packing material (either foam or gauze), and the device generates a negative pressure (suction) force at the wound bed interface. The packing material is covered by a drape which creates a closed healing system. The delivery of negative pressure to the wound site ranges from 50 mmHg to 125 mmHg .

Negative pressure wound therapy is now widely used around the world to treat a number of wound indications, and has been extensively researched. In 2011, Krug et al. 22{ }^{22} estimated that over 1000 peer reviewed articles reporting on studies of chronic wounds examining the clinical effectiveness and safety of NPWT were published. In the last five years, there have been a number of systematic reviews conducted of published studies on NPWT. 21−23{ }^{21-23} Several of these reviews had the specific objective of working towards building an international consensus on the use of NPWT, and developed evidence-based recommendations for this purpose. In 2007, Kanakaris et al. 23{ }^{23} examined the efficacy of NPWT in the management of wounds resulting from lower extremity trauma or burns. The authors concluded that the effectiveness of NPWT was comparable to standard dressing and wound coverage methods in the acute phase of blunt, penetrating and/or thermal trauma in this region.

Two systematic reviews used to build consensus were published in 2011. Birke-Sorensen et al. 24{ }^{24} focused on treatment variables: different pressure settings, wound fillers, use of a wound contact layer, and the impact of NPWT on bacterial bio-burden. Although 14 recommendations were developed, the expert panel concluded there was relatively weak evidence on which to base these recommendations. Two hundred and eight papers met the inclusion criteria established for the review and from this base, 12 proposed recommendations were developed. This was not a systematic review that required the critical appraisal process but rather a consensus method used by the panel following an assessment of selected papers using the Scottish Intercollegiate Guidelines Network (SIGN), and reached the 80%80 \% agreement level with practicing clinicians. The findings indicated that the evidence base was strongest for the use of NPWT on skin grafts, while it was weakest for primary treatment in burns.

Despite the extensive research on this topic to date, a search of relevant databases did not elucidate a published systematic review that focused on the use of NPWT in preventing complications in postsurgical wounds. It was the objective of this systematic review to address that knowledge gap. More specifically, the aim of this review is to identify whether NPWT, as a mode of therapy, is effective in the prevention of post-surgical wound dehiscence and/or infection. The primary outcome measure was whether or not the patient incurred a post-surgical wound infection or dehiscence. The objectives, inclusion criteria, and methods of analysis for this review, were specified in advance and documented in a protocol (PROSPERO CRD42013006298). 25{ }^{25}

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1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

Objectives

The aim of this review was to identify the effectiveness of NPWT in the prevention of post-surgical wound complications.

More specifically, the objective was to identify the effectiveness of NPWT for post-surgical wound complications, as measured by the prevention of post-surgical site infections for closed surgical incisions, wound dehiscence, hematoma, seroma, in adults compared to standard surgical dressings (SSDs).

Inclusion criteria

Types of participants

This review considered studies that included male and female adults over the age of 18 who have had NPWT applied to their closed surgical incision following a procedure in one of the following areas, but not confined to: trauma, cardiothoracic, orthopedic, general or vascular surgery.

Patients with existing wound complications were excluded. Obstetric studies were excluded.

Types of intervention

The review considered studies that evaluated the use of NPWT directly over a closed surgical incision, following any procedure in trauma, cardiothoracic, abdominal, vascular, or orthopedic surgery.

The comparator was the standard form of incisional care (SSD) used by the clinician including but not limited to dry dressings, foams, silicone, gauze, hydrocolloids or hydrofibres.

Types of studies

The review sought both experimental and epidemiological study designs, including randomized controlled trials, pseudo-randomized trials, quasi-experimental studies, before and after studies, prospective and retrospective cohort studies, case control studies, and analytical cross sectional studies for inclusion.

Types of outcomes

The primary outcome was post-surgical wound complication/s as measured by the following:

• Surgical site infections - superficial and deep
• Surgical wound dehiscence
• Wound pain
• Wound seroma
• Wound hematoma
• Length of hospital stay.

Search strategy

The search strategy aimed to find both published and unpublished studies in humans only. A threestep search strategy was utilized in this review. An initial limited search of MEDLINE and CINAHL was undertaken, followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe the article. A second search using all identified keywords and index terms was then undertaken across all included databases. Thirdly, the reference list of all identified reports and

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1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/10.11124 / bisnir-2015-1687 ↩︎

articles was searched for additional studies. Studies published between 1990 and 2013 were considered for inclusion in this review, 1990 marking when research on the use of NPWT in humans and the consequent academic reporting of this research began to proliferate.
The databases searched include:

• MEDLINE
• CINAHL
• EMBASE
• Scopus
• TRIP
• Google Scholar
• Medscape

The review included grey literature and unpublished material such as conference papers, research reports and dissertations which were sourced wherever possible. The sources searched to locate unpublished studies included:

• Clinical trials.gov,
• World Health Organization (WHO) International Clinical Trials Registry Platform,
• Australian and New Zealand Clinical Trials Registry,
• Current Controlled Trials,
• Cochrane Central Register of Clinical Trials
• Conference Proceedings Citation Index- Science (CPCI-S)

Only studies in English were included as translation services were not available. See Appendix I for details of search strategies.

Method of the review

Following removal of duplicate records, the articles were screened and those that were not studies, i.e. discussion papers, or not related to the topic, were discarded. The abstracts or, if necessary, the full articles of those records remaining were then assessed to determine if they met the inclusion criteria regarding type of study, participants, intervention and outcomes (see Appendix II for screening tool). The remaining studies were then assessed for methodological quality.

Assessment of methodological quality

The eligible papers were assessed by two independent reviewers for methodological validity prior to inclusion in the review using the standardized critical appraisal instruments from the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI). 25{ }^{25} (Appendix III). Any disagreements that arose between the reviewers were resolved through discussion.

Data collection

Two independent reviewers extracted data from the papers included in the review using the standardized data extraction tool from JBI-MAStARI 25{ }^{25} (Appendix VI). The data extracted included specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. The data extracted are detailed in Appendix V (Table of

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included studies). Of the six outcomes listed in the protocol, wound healing parameters and wound pain were not addressed by any included study. Any differences between the reviewers’ data extraction were resolved through discussion.

Data synthesis

Quantitative data were, where possible, pooled in a statistical meta-analysis using Comprehensive Meta-Analysis software. 26{ }^{26} The Mantel-Haenszel meta-analytical method using a fixed effect model was employed to calculate odds ratios. The basis for selecting this method and model was that all the outcome data in the pooled studies were dichotomous, and the numbers of studies involved were small, as were the number of participants in some of the studies.

Pooling of data from two or more studies was possible in respect to three outcomes: infection, wound dehiscence and seroma, with a sub-group analysis also conducted for the infection outcome. All results were subject to double data entry. Effect sizes expressed as odds ratios (for categorical data) and their 95%95 \% confidence intervals were calculated for analysis (see Figures 2 to 5).

The results of three studies 27−29{ }^{27-29} could not be pooled for several reasons. These included lack of other studies with the same study design addressing the outcome of interest or, although having the same study design, participants were treated for markedly different clinical conditions or different outcomes were addressed. In these cases the outcomes have been presented in narrative form.

Results

Description of studies

Following screening of 2968 records, 103 studies were identified as potentially relevant to the review. The abstracts of these studies were screened against the review’s inclusion and exclusion criteria (see Appendix II). Eighty-two studies reporting on the use of NPWT in the treatment of existing wound complications or those that did not meet the inclusion criteria were excluded. The full text of 21 articles required more detailed examination for eligibility resulting in a further 13 being excluded (Figure 1 and Appendix VI). After critical appraisal of the quality of the eight remaining studies assessing the effectiveness of NPWT in preventing wound complications in closed surgical incisions all eight were included in the review. Figure 1 shows the outcomes of stages of the screening and the study selection process for inclusion in the review.

The studies included in the review were conducted in two countries in tertiary level hospitals. Six of these studies were conducted in the USA 29−34{ }^{29-34} and two in Germany. 27,28{ }^{27,28}

Sample sizes

The number of participants in the included studies ranged from 192819^{28} to 27030270^{30} with a total of 1277 participants. Two of the studies 31,35{ }^{31,35} also included the number of incisions, given more than one incision was required in some cases. Blackham et al 31{ }^{31} included an additional two procedures while Matatov et al recorded an additional 25 incisions.

Study design

The most common study design was retrospective medical notes/chart audit with five studies 30−34{ }^{30-34} adopting this approach. The three remaining studies were randomized or pseudo-randomized trials. 27−{ }^{27-} 29{ }^{29} All of the studies included had a control or comparison group.

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1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

Participants

Two studies 28,31{ }^{28,31} focused on patients who underwent cardiac surgery (median sternotomy), whilst others investigated colorectal surgery, 32{ }^{32} abdominal wall reconstruction for ventral hernias, 33{ }^{33} vascular (groin) surgery, 35{ }^{35} total hip replacement, 29{ }^{29} and lower limb fractures following trauma and requiring stabilization. 30{ }^{30}

In one study 33{ }^{33} the number of male patients exceeded female patients. In one of the cardiac surgery studies, 3189.5%{ }^{31} 89.5 \% of the participants were male, and in the study 30{ }^{30} involving lower limb fractures the number of females were half that of the male patients. Only in one study Conde-Green 34{ }^{34} involving patients undergoing repair of ventral hernias, did the percentage of females exceed that of males ( 59%59 \% versus 41%41 \% ). The mean age of participants in the studies was 50 and above, the only exception being the lower limb fracture stabilization study Stannard 30{ }^{30} in which the mean age was 43 years. Most of these fractures resulted from vehicle accidents and falls. Patients undergoing surgery for cardiovascular problems, cancer and hip replacements fell into the older age groups.

A number of the studies involved high-risk patients with a significant number of co-morbidities. Of particular concern were patients at high-risk of infection due to diabetes mellitus and/or obesity. In two studies 31,32{ }^{31,32} this was the basis on which patients were allocated to comparison groups (high-risk versus low-risk of SSIs).

Figure1: Study selection flow diagram
From: Moher D, Liberati A, Tetzlaff J, Altman DG, The PRISMA Group (2009). Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement. PLoS Med 6(6): e1000097. doi:10.1371/journal.pmed1000097

Interventions

All studies used a single intervention: NPWT over the surgical incision directly following a surgical procedure. Six of the eight included studies detailed the application method of the NPWT which was similar across the studies; a thin layer of non-adhesive dressing over the incision covered by a thin strip of foam, then sealed with an occlusive dressing and suction applied. All eight included studies indicated the trade name of the NPWT device. The devices were obtained from one of two companies; three studies 27,28,34{ }^{27,28,34} using one produced in Europe while the other five studies 29−33{ }^{29-33} used a device from a USA company. Two different NPWT devices were used in the studies reporting infection rates - one by four studies 29−31,33{ }^{29-31,33} and the other by the remaining two studies. 27,34{ }^{27,34} Four studies 28,30,32,34{ }^{28,30,32,34} used −125mmHg-125 \mathrm{mmHg} pressure, one 33−75mmHg{ }^{33}-75 \mathrm{mmHg} and two 31,35{ }^{31,35} did not report pressure levels. There was only one difference in the application of the device. In Atkins et. Al. 31{ }^{31} the foam strip placed over the non-adhesive covering of the incision was impregnated with silver which is assumed to reduce bacterial counts. The period of application of the device ranged from two-and-a-half to seven days.

The control/comparison group in seven of the studies 28,29,31−35{ }^{28,29,31-35} received a ‘standard’ dressing cover to the incision variously described as ‘occlusive’, ‘dry’ or ‘surgical’. The remaining study, Stannard 30{ }^{30} only reported ‘standard post-operative wound care’ with no details of the type of wound dressing.

Outcomes

Six outcomes relevant to the objective of the systematic review were addressed in the included studies (overall wound complications, infection, wound dehiscence, seroma, hematoma, length of hospital stay). The latter two outcomes had not been specifically identified in the review protocol and were only addressed by single studies so no comparisons could be made. No studies collected specific data on two of the outcomes intended to be investigated in this review: wound pain or wound healing parameters.

Of the studies that addressed infection as an outcome, three 28,32,33{ }^{28,32,33} drew on the Centers of Disease Control and Prevention (CDC) definitions to distinguish superficial and deep SSIs. 9{ }^{9} Grauhan et al. 28{ }^{28} also employed El Oakley and Wright’s 37{ }^{37} criterion for this purpose. The El Oakley and Wright classification comprises of four grades with Grade I to Grade IV, with Grade IV requiring surgical intervention. Matatov et al. 35{ }^{35} used the Szilagyi 38{ }^{38} classification, which encompasses three grades specific to vascular surgery to describe SSIs in their study (Grade I: cellulitis involving the wound, Grade II: infection involving subcutaneous tissue and Grade III: infection involving vascular prosthetic). One study 30{ }^{30} did not employ an internationally accepted standardized definition but did use a set of clinical signs and symptoms together with related laboratory results (blood tests and wound cultures) for confirmation. The remaining two retrospective studies 31,34{ }^{31,34} which obtained their data from chart reviews did not report how infection was defined. It was assumed that the clinician’s charted observation of infection being present was accepted.

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Methodological quality

Of the eight studies that met the eligibility criteria for inclusion in the review, all achieved or exceeded the minimum requirement of 60%60 \% of applicable criteria on the relevant MAStARI checklist (Appendices 2 to 4 ).

Table 1: Number of studies included and excluded on quality

The major weakness related to methodological quality was the lack of information on the measurement of outcomes, specifically the use of objective criteria and the reliability of the measurement. These weaknesses were more common in the retrospective studies (Table 3). This is not surprising as the data collected for those studies came from chart reviews, where collecting and recording of data would not have been subject to the control of a prospective study.

Table 2: Quality assessment results for cohort studies

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1. *Number of applicable criteria met ↩︎

Table 3: Quality assessment results for randomized studies

• Two parts to criterion

**None withdrew
***Number of applicable criteria met
Based on the reported method of randomization in the study by Grauhan et al. 28{ }^{28} this study was classified as a pseudo-randomized trial (Level of Evidence 1d), that is the assignment to treatment groups was not truly random (Q1). Nor was allocation of participants to treatment groups concealed from the allocator (Q3). Of the remaining two studies one 30{ }^{30} identified the study design as a prospective randomized clinical trial and the other 29{ }^{29} as a prospective randomized evaluation study but neither provided details of their method of randomization so this was graded as ‘unclear’ (Q1).

Given the nature of the intervention it was not possible to blind the participants to treatment allocation (Q2), nor those assessing the outcomes (Q5), hence these questions were graded as ‘Not Applicable’. In two studies 29,30{ }^{29,30} no participants were withdrawn so Q4 was not applicable to those studies. In Grauhan et al, 28{ }^{28} six of the 156 included patients were withdrawn from the study. Three of these required reopening of the thorax due to post-operative bleeding and three died from causes unrelated to wound complications. These six were not included in the analysis. Thus only one of the two sections of this criterion (Q4) was met.

All but one study 31{ }^{31} provided data on the comparability of the NPWT and the control/comparison group. In most of the studies, data were collected on a large number of demographic and clinical

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1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

variables. Despite the number of variables involved, with the exception of one study, 32{ }^{32} the groups within each study were statistically comparable on all but one or two variables at most.

Findings of the review

Results of meta-analyses

Of the eight included studies it was determined that five studies 31−35{ }^{31-35} met the requirements (they were comparable in study design, intervention and outcomes), to be included in one or more meta-analyses involving three outcomes of interest; wound infection (plus a sub-group analysis), wound dehiscence and seroma. Although there were two studies that provided data on overall wound complications, a trial meta-analysis indicated heterogeneity between the studies ( p<0.1p<0.1, confidence interval [CI] 0.7 ), therefore these studies were not pooled. The complication of hematoma was reported in one study only.

Infection

Five studies 31−35{ }^{31-35} contributed data on infection to a meta-analysis (Figure 2), with pooling of the data being supported by a pp value of 0.409 when testing for heterogeneity. The odds ratio generated by the fixed effects model was 0.407 ( 95%95 \% CI0.243 - 0.683), with a statistically significant (p 0.001) reduction of 59%59 \% in the likelihood that patients whose surgical incisions are treated with NPWT will experience post-operative wound infection. The robustness of the results of this meta-analysis is indicated by the sensitivity analysis; both the random and fixed effects models produced the same effect size.

Meta Analysis

Figure 2: Rate of Infection

It should be noted that Bonds et al. 33{ }^{33} recorded any opening of the wound as wound infection as a strategy to minimize interpreter bias inherent in retrospective data collection on surgical wound infection rates. When Bond’s study was excluded from the meta-analysis, the odds ratio generated by the fixed effects model with the remaining four studies included was 0.47 ( 95%95 \% CI 0.237−0.7700.237-0.770 ) and a p value of 0.005 . In respect to heterogeneity, p=0.277\mathrm{p}=0.277 and the I squared value was 22.286 indicating the data could be pooled.

In addition to comparing the total infections between the NPWT and the standard dressing groups, Blackham et al. 32{ }^{32} examined the rate of superficial only incisional infections. The lower occurrence in the NPWT group ( 6.7%6.7 \% ) compared to the standard surgical dressing group (19.5%) was statistically significant ( p=0.019p=0.019 ).

A sub-group analysis was performed on the two studies 32,33{ }^{32,33} investigating the rates of infection in elective cases only (Figure 3). The test for heterogeneity ( p=0.491p=0.491 ) allowed for pooling of the data from these two studies. The odds ratio generated by the fixed effects model was 0.475 ( 95%95 \% CI 0.263 -0.859 ) with a statistical significance ( p=0.014p=0.014 ) in favor of NPWT.

Two additional studies 28,30{ }^{28,30} included infection as a study outcome but due to differing study designs the data could not be pooled with those from the studies above. The results therefore are presented in narrative form. The findings of these two studies 28,30{ }^{28,30} support the results of the meta-analysis. Stannard et al. 30{ }^{30} analyzed the infection data on the basis of open and closed fractures and closed only fractures in their randomized study of the use of NPWT in lower limb fractures resulting from blunt high energy trauma. In both analyses the use of NPWT resulted in a statistically significant difference between the groups in favor of NPWT ( p<0.05p<0.05 ).

In Grauhan’s pseudo-randomized trial, 28{ }^{28} three (4%) of the NPWT group developed an incisional infection compared to 12 (16%) of the control group. This was statistically significant ( p=0.027p=0.027 with an odds ratio of 4.75 ( 95%CI,1.42−91.3695 \% \mathrm{CI}, 1.42-91.36 ). The other statistically significant finding was the difference between groups in the superficial infections caused by gram positive skin flora, with 13%13 \% of the conventional wound dressing group being infected compared to 1.3%1.3 \% of the NPWT group ( p=0.009p=0.009; odds ratio 4.57,95%4.57,95 \% CI 1.23-16.95). There was also a difference in the time at which the infections occurred. In the NPWT group all three infections occurred prior to the removal of the NPWT (prior to day 6/7 postoperatively). In contrast, in the control group nine of the 12 infections (75%) occurred past the first postoperative week and up to day 35 ( p=0.016p=0.016 ). It was noted that in the NPWT group at the time of device removal at day 6/76 / 7, wound closure had already occurred in 95%95 \% of the patients. The authors suggested that this difference in the timing of the occurrence of infection was due to the rate of surgical incision healing, with the closure of the wound aided by improved drainage of wound secretions by the NPWT.

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1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

Meta Analysis

Model Effect size and 95% interval Test of null (0 Tall) \quad Heterogeneity

Figure 3: Rate of infection in elective cases only
All but one study 35{ }^{35} selected high-risk patients, and in two studies 31,32{ }^{31,32} the intervention group and the control group were assessed as low risk for infection. Five of the studies 28,31,34{ }^{28,31,34} employed similar criteria for high-risk. These focused on age, obesity (BMI ≥30\geq 30 ), diabetes mellitus and other comorbidities such as chronic obstructive pulmonary disease (COPD). The fourth study, 30{ }^{30} given its topic of interest of lower extremity fractures, had a different set of criteria. In this study the definition of highrisk was based on the type of fracture sustained (tibial plateau, pilon or calcaneal) as a result of a high-energy mechanism of injury. The remaining study 35{ }^{35} did not include high-risk participants.

Grauhan et al 28{ }^{28} reported that one patient ( 1.3%1.3 \% ) in the NPWT group developed a superficial sternal infection and two patients ( 2.6%2.6 \% ) from that group were diagnosed with a deep sternal infection. Based on the risk analysis undertaken by Atkins et al. 31{ }^{31} it was estimated that at least three sternal wound infections (mediastinitis) would occur post operatively in their study. However, in the NPWT group no deep or superficial infections occurred in the 57 patients. Twelve-and-a-half per cent of the NPWT group had an incisional infection compared to the control group of 19.5%19.5 \%. Reports of infection rates in colorectal surgery patients cover a wide range from 12.6%12.6 \% to as high as 45%.32,3345 \% .{ }^{32,33} Twelve-and-a-half per cent of colorectal patients in the intervention group in Bonds et al’s 33{ }^{33} study developed an infection, compared to 29.3%29.3 \% in the control group. Matatov et al. 35{ }^{35} reported 6%6 \% of patients with only a superficial infection in the intervention group compared to 30%30 \% of the control group who had subcutaneous or arterial graft infections.

Wound dehiscence

Four studies addressed wound dehiscence: two retrospective cohort studies 32,34{ }^{32,34} using chart audits, plus a randomized 30{ }^{30} and a pseudo-randomized trial. 28{ }^{28} The data from the two retrospective cohort studies were pooled in a meta-analysis (Figure 5). The results of the meta-analysis were not statistically significant ( p=0.066p=0.066 ). The odds ratio generated by the fixed effects model was 0.26 ( 95%95 \% CI 0.062−1.0950.062-1.095 ). It is noted that the Blackham et al. 32{ }^{32} study only reported one case of wound dehiscence out of 191 patients in the NPWT group compared to none in the control group.

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Meta Analysis

Figure 4: Wound dehiscence
The Conde-Green et al. 34{ }^{34} study, when examined individually, concluded that NPWT was associated with a decreased incidence of wound dehiscence (NPWT group 2/23 vs comparison group 13/33 ( p=0.019p=0.019 )), which is statistically significant. However, due to the low sample size, extrapolations of these findings to the clinical setting may be obfuscated.

The randomized trial conducted by Stannard et al. 30{ }^{30} demonstrated a statistically significant difference between the NPWT and the control group in favor of the NPWT. Twelve cases of dehiscence (9%) occurred in the NPWT group post-discharge while the complication occurred in 20 (17%) participants in the control group ( p=0.04p=0.04 ). However, Grauhan et al. 28{ }^{28} did not report a statistically significant difference between the two groups in terms of wound dehiscence ( p=0.62p=0.62 ).

All four studies employed a negative pressure of 125 mmHg . Three studies used the same device 30{ }^{30}, 32,34{ }^{32,34} while the fourth applied a device manufactured by another company. 28{ }^{28} The method of application and securing of the device was similar in all cases. The period of application varied between each study: 2.5 days, 304{ }^{30} 4 days, 325{ }^{32} 5 days 34^{34} and 6−7286-7^{28} days.

All four studies 28,30,32,34{ }^{28,30,32,34} included only high-risk patients in their sample. The parameters used in the assessment of high-risk for these studies are the same as were employed in assessing participants for risk of infection, based on the association of infection and wound dehiscence. In summary the evidence for reduction of wound dehiscence is limited due to small sample sizes across the studies. However one study 34{ }^{34} indicates that there is a reduction in dehiscence following the use of NPWT.

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Seroma

Blackham et al. 32{ }^{32} Conde-Green et al. 34{ }^{34} and Pachowsky et al. 29{ }^{29} documented the occurrence of seroma. Pooling of the data from studies by Blackham et al. 32{ }^{32} and Conde-Green et al. 34{ }^{34} was supported by the test for heterogeneity result ( p=0.22p=0.22 ). The odds ratio generated by the fixed effects model was 0.726(95%0.726(95 \% CI 0.187−2.817)0.187-2.817) and there was no statistically significant difference between the groups for the outcome of seroma ( p=0.06p=0.06 ), see Figure 5.

In contrast, a prospective randomized evaluation of NPWT by Pachowsky et al. 29{ }^{29} (n=19), demonstrated a difference in the occurrence of seroma following total hip arthroplasty between the NPWT group ( 44%44 \% ) and the standard wound dressing group ( 90%90 \% ). Also a significant difference was found in the mean volume of the seroma between these two groups by the 10th 10^{\text {th }} post-operative day ( p=0.021p=0.021 ), favoring NPWT. Pachowsky was excluded from the meta-analysis for seroma as the study population (orthopedic) differed from the study sample of Blackham et al 32{ }^{32} and Conde-Green et al34\mathrm{al}^{34} (abdominal) therefore the combining of these three studies would result in a heterogeneous population. Therefore results from Pachowsky et al 29{ }^{29} is included here in the narrative form.

Meta Analysis

Figure 5: Occurrence of wound seroma
The incidence of seroma reported in Pachowsky et al 29{ }^{29} was markedly higher in both the intervention and control groups than in the other two studies. The incidence of seroma identified by Conde-Green et al. 34{ }^{34} was 0%0 \% and 12%12 \% in the intervention and control groups, respectively, while in Blackham et al 32{ }^{32} at ≤30\leq 30 days postoperatively the incidence was 3.8%3.8 \% (NPWT) versus 3.4%3.4 \% (control group). In summary the results are inconclusive for seroma due to small sample sizes, although an effect was observed by the studies 32,34,29{ }^{32,34,29} further larger studies are required.

Hematoma

Blackham et al. 32{ }^{32} and Conde-Green et al. 34{ }^{34} also reported on the occurrence of hematomas, but their findings give no guidance as to the efficacy of NPWT in preventing this complication. Conde-Green et al. 34{ }^{34} found no hematomas in either the NPWT or the comparison group. In the other study, 32{ }^{32} two patients ( 2.3%2.3 \% ) in the comparison group developed a hematoma while none were found in the NPWT

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group. The NPWT device employed, application and amount of negative pressure applied were the same in both studies.

Overall wound complications

Two studies 32,34{ }^{32,34} provided data on overall wound complications following the use of NPWT versus standard wound dressings. Blackham et al. 32{ }^{32} reported that 24%24 \% of patients receiving NPWT experienced some type of wound complication compared to 35.6%35.6 \% of the control group. This was statistically significant ( p=0.05p=0.05 ) with an odds ratio of 0.52 ( 95%95 \% CI 0.26−1.000.26-1.00 ). The result found by Conde-Green et al. 34{ }^{34} was also statistically significant ( p=0.02p=0.02 ). Twenty-two percent of the NPWT group experienced wound complications compared to 63.6%63.6 \% of the control group (odds ratio 6.3, 95% CI 1.37 - 34.14).

Length of stay

The data on length of stay (LOS) were sparse. Two studies 30,31{ }^{30,31} provided data on hospital LOS with only one 30{ }^{30} comparing intervention and control groups. The average LOS for the NPWT group in this study was 2.5 days compared to 3 days for the standard dressing group. The difference was not statistically significant ( p=0.103p=0.103 ), although from a clinical standpoint this translates to the patient spending less time at hospital. Atkins et al. 31{ }^{31} reported the average LOS of 9.8±109.8 \pm 10 days and a median of 7 days. Differences between the intervention and control group were not reported.

Discussion

This review was conducted to determine the efficacy of negative pressure wound therapy in the prevention of surgical wound complications. It is clear from the type of evidence published that this field is in its formative years with rigorous testing yet to be done. For maximum clinical impact, Level 1evidence is required to support the case for any indicated use of an interventional therapy. The use of NPWT is no exception to this rule. Unfortunately this review has demonstrated that much of the reported research falls short of the quality expected for evidence-based clinical practice.
The majority of the included studies 31−35{ }^{31-35} are JBI Level 3 evidence (retrospective cohort studies/chart reviews) and as such are burdened with the inherent issues and limitations faced with this type of evidence. What these studies have highlighted is that there may be a positive effect from the use of NWPT, however, more work is needed. Future high-quality studies should ideally identify patients at risk of wound complications prior to surgery. If one is to test for efficacy of an intervention ideally this should be done during recruitment in the preoperative period, rather than retrospectively, albeit following an ‘ad hoc’ approach. To make the assumption that the intervention has worked following a retrospective ‘at risk’ identification as some studies have done 31−35{ }^{31-35} renders the work questionable in testing the efficacy of a therapy. Nevertheless the studies in this review have alluded to associated risk factors with wound complications and have reported an effect when using NPWT.

Of the randomized studies examined, two 29,30{ }^{29,30} imply a reduction in infection when using NPWT compared to those patients that received standard surgical dressings. Again, small sample sizes make it difficult to consolidate a valid clinical indication for the use of NPWT as a prophylactic measure in preventing surgical wound complications. Other studies 28,32{ }^{28,32} have demonstrated a lack of significant difference in the occurrence of surgical wound dehiscence between groups (NPWT vs SSD), whereas others 30,34{ }^{30,34} demonstrated a significant difference between those that received NPWT compared to SSD, in favor of NPWT. The discourse within this particular clinical quandary is still underway.

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Complications generate costs of varying kinds at the individual, family and organizational level. In addition to the impact of morbidity and mortality, there are the financial costs. Decreasing the occurrence of complications can have significant benefits. Conde-Green et al 34{ }^{34} reported that patients with standard post-operative dressings were 6.3 times more prone to develop wound complications than those treated with NPWT. In discussing the use of NPWT in patients undergoing repair of ventral hernias, the authors pointed out the benefits of NPWT in achieving primary closure, reduced postoperative complications and recovery time for both the patient and the healthcare system. Atkins et al. 31{ }^{31} estimated that in the USA, if one severe case and three to four cases of superficial sternal wound infection were prevented each year, the costs of NPWT would be covered for approximately 100 cases a year. 31{ }^{31} Matatov et al. 35{ }^{35} reported that the cost for the long hospitalization and treatment of one of the patients in the non-NPWT group who developed a post-operative infection in the arterial graft (Szilagyi Grade III) was USD45,000. The authors compared this to the USD25,740 cost of the 52 NPWT devices required for the study. The half day decrease in average length of stay for the NPWT group when compared to the control group more than offset the cost of hospitalization. From these findings it would appear that NPWT may play a role in the reduction of infection which can offset the cost of the device and reduce the burden on the hospital system. Further studies are required to demonstrate this assumption.

This review has highlighted that there may be a positive effect from the use of NPWT following a surgical procedure; however, due to the lack of high powered studies it is difficult to measure the effect in an empirical manner. It is certain that more research needs to be carried out.

Conclusion

The primary objective of this systematic review was to determine whether the use of NPWT is effective for reducing surgical wound complications compared to standard dressings. It is clear that this field of research is in the formative years, with most of the studies being retrospective in nature to attempt to establish whether there are differences between intervention and controls groups. In and of its own merits, retrospective analysis can provide a measure of the occurrence of a condition and assist in determining the incidence, prevalence and rates of the condition being investigated. What remains to be identified is whether NPWT is effective as a prophylactic therapy in the prevention of wound complications in patients that are “at risk” or have multiple comorbidities. This review has highlighted that the results of retrospective studies, when pooled, favor NPWT over the control group in the following outcomes; infection and wound dehiscence. The evidence for seroma appears to be inconclusive. However, given the nature of the evidence and lack of high powered studies it is difficult to provide evidence based clinical recommendations in the use of this therapy as a preventative measure for wound complications following surgery.

Implications for practice

Recommendation: Negative pressure wound therapy in preference to standard postoperative dressings, for example dry gauze, may be used over closed surgical incisions in adults assessed as high-risk to reduce the occurrence of surgical site infection. (Grade B recommendation). 39{ }^{39}

Accurate identification of ‘high-risk’ patients is required when implementing this recommendation to ensure resources are used as efficiently as possible. The use of appropriate and validated risk assessment tools should guide clinical decisions on the use of these devices.

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Implications for research

The following recommendations are made for further research:

• The focus of further research on this topic should be RCTs with sample sizes determined by power calculations. Given the relatively low incidence of some wound complications in surgical incisions (e.g. seroma and hematoma), multi-center trials would be needed to address these outcomes.
• Given the marked under-representation of women in studies on this topic to date, where appropriate, efforts should be made to increase the number of females in study samples.
• Future studies should employ valid methods of randomization and control for potentially confounding variables.
• Studies should use widely accepted criteria or definitions for measurement of outcomes to facilitate comparison of results.
• Studies should follow up participants for at least 30 days postoperatively to ensure all complications that occur are reported.
• Full reporting of study methods is required in order to assess the quality of the study e.g. blinding to group allocation, methods of assessing outcomes, inter-rater reliability where appropriate.
• Aspects of the topic which need to be examined in more detail are cost-effectiveness, length of stay and comparison of the various negative pressure wound therapy systems in respect to their effectiveness in preventing surgical wound complication.

Conflict of interest

The authors of this systematic review declared no conflicts of interest.
An author (fourth of five authors) of one 33{ }^{33} of the eight included studies reported a financial disclosure.

Acknowledgements

This research was funded by a CRC Wound Innovation Management Project Grant 3.13. The authors would like to acknowledge Professor Keryln Carville and Professor Gavin Leslie for reviewing the paper. The authors would also like to acknowledge the JBI reviewers for taking the time and effort to provide constructive feedback. The authors would like to acknowledge the West Australian Centre for Evidence Informed Health Care Practice (Curtin University), and the JBI Wound Node for funding assistance.

References

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2. Australian Institute of Health and Welfare. Australian Hospital Statistics 2010-11 - Chapter 10 Surgery in Australian Hospitals. Canberra: AIHW; 2012.

3. Rodero M, Khosrotehrani K. Skin wound healing modulation by macrophages. Int J Clin Exp Pathol. 2010;3:643-53.

4. Webster C, Neumayer L, Smout R, Horn S, Daley J, Henderson W, et al. Prognostic models of abdominal wound dehiscence after laparotomy. J Surg Res. 2003;109(2):130-7.

5. van Ramshorst G, Nieuwenhuizen J, Hop W, Arends P, Boom J, Jeekel J, et al. Abdominal wound dehiscence in adults:development and validation of a risk model. World J Surg. 2010;34(1): 20-27.

6. Baronski S, Ayello A, editors. Wound Care Essentials: Practice and Principles. 3rd ed. Philadelphia: Wolters Klewor Health/Lippincott Willams & Willams; 2012.

7. Riou J, Cohen J, Johnson HJ. Factors influencing wound dehiscence. Am J Surg. 1992;163(3):324-30.

8. Ridderstolpe L, Granfeldt H, Ahlfeldt H, Rutberg H. Superficial and deep sternal wound complications: incidence, risk factors and mortality. Eur J Cardiothorac Surg. 2001;20:1168-75.

9. Horan T, Adrus M, Dudeck M. CDC/NHSN surveillance definition of health care associated infection and criteria for specific types of infections in the acute care setting. 2013; Available from: http://www.cdc.gov/nhsn/acute-care-hospital/ssi/.

10. Leaper D, van Goor H, Reilly J, Petrosillo N, Geiss H, Torres A, et al. Surgical site infection a European perspective of incidence and economic burden. Int Wound J. 2004;1:247-73.

11. Urban J. Cost analysis of surgiclal site infections. Surg Infect. 2006;7(Supp 1):S19-22.

12. Mclaws M, Irwig L, Mock P, Berry G, Gold J. Predictors of surgical wound infection in Australia - a national study. Med J Australia. 1988;149(11-12):591-5.

13. Mclaws M, Taylor P. The Hospital Infection Stanardised Surveillance programme: analysis of a two year pilot J Hosp Infect. 2003;53:259-67.

14. Fleischmann W, Kinzl L. Vacuum sealing technique stimulates soft tissue proliferation. Langeng Arch. 1995(Supp):256-60.

15. Fleischmann W, Russ M, Marquardt C. Closure of defect wounds by combined vacuum sealing with instrumental skin expansion. Unfallchirurg. 1996;99:970-4.

16. Fleischmann W, Lang E, Russ M. Treatment of infection by vacuum sealing. Unfallchirurg. 1997;100:301-4.

17. Fleischmann W, Strecker W, Bombelli M, Kinzl L. Vacuum sealing as treatment of soft tissue damage in open fractures. Unfallchirurg. 1993;96:488-92.

18. Argenta L, Morykwas M. Vacuum-assisted closure: a new method for wound control and treatment: clinical experience. Ann Plast Surg. 1997;38:563-76.

19. Morykwas M, Argenta L. Nonsurgical modalities to enhance healing and care of soft tissue wounds. J South Orthop Assoc. 1997;6:279-88.

20. Morykwas M, Argenta L, Shelton-Brown E, McGuirt W. Vacuum-assisted closure: a new method for wound control and treatment: animal studies and basic foundation. Ann Plast Surg. 1997;38:553-62.

21. Morykwas M, Argenta L. Use of negative pressure to increase the rate of granulation tissue formation in chronic open wounds. Faseb J. 1993;7(3):A138-A.

22. Krug E, Berg L, Lee C, Hudson D, Birke-Sorensen H, Depoorter M, et al. Evidence-based recommendations for the use of negative pressure wound therapy in traumatic wounds and reconstructive surgery: steps towards an international consensus. Injury. 2011;42(Suppl 1):S1-12.

23. Kanakaris N, Thanasas C, Keramaris G, Kontakis G, Granick M, Giannoudis P. The efficacy of negative pressure wound therapy in the management of lower extremity trauma: review of the clinical evidence. Injury. 2007;38(Suppl 5 9-18).

24. Birke-Sorensen H, Malmsjo M, P R, Hudson D, Krug E, Berg L, et al. Evidence-based recommendations for negative pressure wound therapy: treatment variables (pressure levels, wound filler and contact layer) - steps towards an international consensus. J Plast Reconstr Aesthet Surg. 2011;64(Suppl):S1-16.

25. Sandy-Hodgetts K, Watts R. Effectiveness of topical negative pressure /closed incision management in the prevention of post-surgical wound complications: a systematic review protocol. The JBI Database of Systematic Reviews and Implementation Reports. 2013; 11(9):12-23.

26. Joanna Briggs Institute. Reviewers’ Manual. Adelaide: Joanna Briggs Institute; 2014.

27. Borenstein M, Rothstein H. Comprehensive meta-analysis: A computer program for research synthesis. [1 March 2014]; Available from:

http://www.meta-analysis.com/index.phh?gclid=CKt\_rp7dmL0CFcLvpAo.
28. Grauhan O, Navasardyan A, Hofmann M, Muller P, Stein J, Hetzer R. Prevention of poststernotomy wound infections in obese patients by negative pressure wound therapy. J Thorac Cardiovasc Surg. 2012;145:1387-92.
29. Pachowsky M, Gusinde J, Klein A, Lehrl S, Schulz-Drost S, Schlechtweg P, et al. Negative pressure wound therapy to prevent seromas and treat surgical incisions after total hip arthroplasty. Int Orthop. 2012;36:719-22.
30. Stannard J, Volgas D, McGwin G, Stewart R, Obremskey W, Moore T, et al. Incisional negative pressure wound therapy after high-risk lower extremity fractures. J Orthop Trauma. 2012;26(1):37-42.
31. Atkins B, Wooten M, Kistler J, Hurley K, Hughes G, Wolfe W. Does negative pressure wound therapy have a role in preventing poststernotomy wound complications? Surg Innov. 2009;16(2):140-6.

1. Blackham A, Farrah J, McCoy T, Schmidt B, Shen P. Prevention of surgical site infections in high-risk patients with laparaotomy incisions using negative-pressure therapy. Am J Surg. 2013;205:647-54.
2. Bonds A, Novick T, Dietert J, Araghizadeh F, Olson C. Incisional negative pressure wound therapy significantly reduces surgical site infection in open colorectal surgery. Dis Colon Rectum. 2013;56:1403-8.
3. Conde-Green A, Chung T, Holton L, Hui-Chou H, Zhu Y, Wang H, et al. Incisional negative pressure wound therapy versus conventional dressings following abdominal wall reconstruction: a comparative study. Ann Plast Surg. 2013;71:394-7.
4. Matatov T, Reddy K, Doucet L, Zhao C, Zhang Y, Wang H, et al. Experience with a new negative pressure incision management system in prevention of groin wound infection in vascular surgery patients. J Vasc Surg. 2013;57(3):791-5.
5. Moher D, Liberati A, Tetziaff J, Altman D. Preferred reporting style for systematic reviews and meta-analyses. The PRISMA statement. PLoS Med. 2009;6(6: e100097).
6. El Oakley R, Wright J. Postoperative mediastinitis:classification and management. Ann Thorac Surg. 1996;61(3):1030-6.
7. Szilagyi D, Smith J, Ellliot J, Vrandecic M. Infection in arterial reconstruction with synthetic grafts. Ann Surg. 1972;176(3):321-33.
8. The Joanna Briggs Institute Levels of Evidence and Grades of Recommendations Working Party. Supporting document for the Joanna Briggs Institute Levels of Evidence and Grades of Recommendations The Joanna Briggs Institute. 2014; Available from: http://joannabriggs.org/jbiapproach.html#tabbed-nav=Levels-of-Evidence.

Appendix I: Search strategy and results

Medline (OVID) 1990- present

Searched 15/8/14
Search Results =1659=1659

S1 exp negative pressure wound therapy
S2 topical negative pressure.mp.
S3 vacuum assisted closure.mp.
S4 (negative pressure wound therapy or vacuum assisted closure).mp. or topical negative pressure.tw.

S5 1 or 2 or 3 or 4
S6 exp postoperative complications/
S7 exp Surgical Wound Infection/
S8 exp Surgical Wound Dehiscence/
S9 exp Wound Healing/ or exp Wound Closure Techniques/
S10 exp hematoma/ or exp seroma/ or exp wound dehiscence/
S116 or 7 or 8 or 9 or 10
S125 and 11
S13 limit 12 to (humans and yr=“1990 - 2013”)

Embase

Searched 15/8/14
Search Results =191=191

S1 exp vacuum assisted closure/
S2 topical negative pressure.mp.
S3 negative pressure wound therapy.mp.
S4 S1 or S2 or S3
S5 exp postoperative complication/
S6 surgical infection/
S7 wound healing/
S8 exp hematoma/ or exp seroma/ or exp wound dehiscence/
S9 S5 or S6 or S7 or S8
S10 S4 and S9
S11 limit S10 to (human and yr=“1990 - 2013”)
S12 limit S11 to exclude medline journals

CINAHL 1982 - current

Searched 15/8/ 14
Search Results =103=103

MH Negative Pressure Wound Therapy
S1"topical negative pressure"
S2"vacuum assisted closure"
S3"vacuum assisted closure and “vacuum assisted closure”
S4(MM “Surgical Wound Infection”) OR (MM “Surgical Wound”) OR (MM
“Surgical Wound Dehiscence”) OR (MM “Surgical Wound Care”)
S5MM Hematoma
S6MM Postoperative Complications
S7MM Wound Healing
S5 OR S6 OR S7 OR S8
S10 S4 and S9
S11 S10 Limiters - Published Date: 19970101-20131231
S12 S11 Limiters - Exclude Medline records

Scopus database

Searched 8th 8^{\text {th }} April 2013
Search results =588=588

Search strategy

((TITLE-ABS-KEY(negative pressure wound therapy) OR TITLE-ABS-KEY(npwt) OR TITLE-ABSKEY(vacuum assisted closure) OR TITLE-ABS-KEY(vac) OR TITLE-ABS-KEY(topical negative pressure)) AND SUBJAREA(mult OR medi OR nurs OR vete OR dent OR heal) AND PUBYEAR > 1989 AND PUBYEAR < 2014) AND ((TITLE-ABS-KEY(closed incision manag*) OR TITLE-ABSKEY(surgical site infection) OR TITLE-ABS-KEY(wound dehiscence) OR TITLE-ABS-KEY(wound healing) OR TITLE-ABS-KEY(wound closure technique*) OR TITLE-ABS-KEY(seroma) OR TITLE-ABS-KEY(hematoma)) AND SUBJAREA(mult OR medi OR nurs OR vete OR dent OR heal) AND PUBYEAR > 1989 AND PUBYEAR < 2014) AND NOT INDEX(medline)

TRIP Database

Searched: 8th 8^{\text {th }} April 2014
Search results =495=495

Search strategy

PICO “(post surgical adults) (negative pressure wound therapy) (standard wound care) (fewer wound complications)”, by quality
“effectiveness OR efficacy topical negative pressure prevent* surgical wound infect*” 10
(title:vacuum assisted closure) (title:post-surgical or postoperative) from:1990 to2013"
(title:negative pressure wound therapy) (title:post-surgical or postoperative) from:1990 to2013"
“preven* surgical site infection* negative pressure wound therapy” 10
from:1990 to:2013
“negative pressure wound therapy closed wound incision*” 10
“vacuum assisted closure surgical wound infection*” 10
“topical negative pressure surgical wound infect*” 10
“topical negative pressure prevent* surgical wound infect*” 10

Google Scholar

Searched : 8th 8^{\text {th }} April 2014
Search results =77=77

Search Strategy

Allinarticle:prevent* surgical site infection* “vacuum assisted closure” yr = 19902013

Allinarticle:prevent* surgical site infection* “negative pressure wound therapy” yr =1990−2013=1990-2013

Allinarticle:prevent* surgical site infection* “topical negative pressure” yr = 19902013

Allinarticle:Prevent* postoperative wound complication* “topical negative pressure” yr = 1990-2013

Allinarticle:Prevent* postoperative wound complication* “vacuum assisted closure” yr = 1990-2013

Allinarticle:Prevent* post-surgical wound complication* “topical negative pressure” yr = 1990-2013

Allinarticle:Prevent* post-surgical wound complication* “vacuum assisted closure”

Allintitle:Effectiveness topical negative pressure closed incision management

Medscape References search

Searched 11th 11^{\text {th }} April
Search results =167=167

Keywords: vacuum assisted closure AND post-surgical wound complications

Grey Literature Search

Clinical Trials.gov

http://www.clinicaltrials.gov/ct2/search/advanced
Searched 11th 11^{\text {th }} April
Search results =1=1

Keywords

vacuum assisted closure AND prevention of post surgical wound complications | Adult

Topical negative pressure closed incision | Adult
negative pressure AND closed incision | Adult
vacuum assisted closure AND prevention surgical site infection

World Health Organization International Clinical Trials Registry

http://www.who.int/ictrp/search/en/
Searched 11th 11^{\text {th }} April 2014
Search results =34=34

Keywords

vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevention post-surgical site infection vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND closed incision vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevention postoperative wound complications

Australian and New Zealand Clinical Trials Registry

http://www.anzctr.org.au/TrialSearch.aspx
Searched 11th 11^{\text {th }} April 2014
Search results =0=0

Keywords

vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevention post-surgical site infection vacuum assisted closure
topical negative pressure

Current Controlled Trials

http://www.controlled-trials.com/isrctn/
Searched: 13th 13^{\text {th }} April 2014
Search results =5=5

Keywords

vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevention post-surgical site infection vacuum assisted closure
topical negative pressure
Negative pressure wound therapy
vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevent* postoperative wound complication*

Cochrane Central Register of Clinical Trials

http://onlinelibrary.wiley.com/cochranelibrary/search
Searched: 13th 13^{\text {th }} April 2014
Search results =110=110

Keywords

vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevention post-surgical site infection(Title, Abstract, Keywords)
vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevent* postoperative wound complication*

Negative pressure wound therapy(Title, Abstract, Keywords)
vacuum assisted closure (Title, Abstract, Keywords)
“topical negative pressure therapy” (Title, Abstract, Keywords)

Web of Science

Conference Proceedings Citation Index- Science (CPCI-S) --1990-present
Searched: 13th 13^{\text {th }} April 2014
Search results =96=96

Keywords

vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy [topic]
vacuum assisted closure OR topical negative pressure OR negative pressure wound therapy AND prevent* postoperative wound complication*
vacuum assisted closure AND surgical site infection[topic]
vacuum assisted closure AND surgical-site infection
postoperative wound infection OR post-surgical site infection

Appendix II: Study screening tool

Title:

Author(s):
Year:

Appendix III: JBI Critical Appraisal instruments

JBI Critical Appraisal Checklist for Randomised Control / Pseudo-randomised Trial

Comments (Including reason for exclusion)

JBI Critical Appraisal Checklist for Comparable Cohort/ Case Control

Comments (Including reason for exclusion)

Appendix IV: JBI Data extraction instruments

JBI Data Extraction Form for Experimental / Observational Studies

Study results

Dichotomous data

Continuous data

Appendix V: Table of included studies

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1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

| Blackham AU, et al. 2013322013{ }^{32} | Oncology -
colorectal,
pancreatic or
peritoneal surface
malignancies
N=191 procedures
on 189 patients: 2
groups
NPMAT: n=104\quad \mathrm{n}=104
cases
Multiple risk factors
for SSI’s
Comparison group:
n=87\mathrm{n}=87 cases
Assessed as low
risk for SSI’s
(Study specific
criteria used for
assessment)
Comparability of
groups:
Groups comparable
on demographic
variables but
differed on 6
perioperative clinical
variables statistically adjusted
for this.
Exclusions:
Infected cases CDC
contaminated | Group A: NPMAT
Negative pressure discontinued on 4th postoperative day
Pressure 125 mmHg
Group B:
surgical dressing removed 2 days post-op - no other details provided
Pre-op SSI
prevention measures were standardized for both groups.
No prophylactic antibiotics postop | ‘Composite’
outcomes i.e. ≤\leq
30days +>30days<br>Infection−deeporsuperficial<br>(CDCdefinitionsused)<br>SuperficialincisionalSSI:<br>GroupA:7/104+>30days
Infection - deep or superficial
(CDC definitions used)
Superficial incisional SSI:
Group A: 7/104 (6.7 %)<br>GroupB:17/87
Group B: 17/87 (19.5 %)<br>
\mathrm{p}=0.019$
OR =0.29(0.11−=0.29(0.11- 0.81)
All incisional SSI:
Group A: 12/104 (11.5%)(11.5 \%)
Group B: 17/87 (19.5%)(19.5 \%)
p=0.106\mathrm{p}=0.106
OR =0.48(0.20−=0.48(0.20- 1.17)
All SSI:
Group A: 17/104 (16.3%)(16.3 \%)
Group B: 23/87 (26.4%)(26.4 \%) | Findings suggest that NPMAT may decrease SSIs in high-risk patients undergoing major abdominal surgery for malignancy. |
| :–: | :–: | :–: | :–: |

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

| Germany | N=1502 groups (6 withdrawn from original 159 - reasons reported) \begin{aligned} & N=150 \quad 2 \text { groups } \\ & \text { (6 withdrawn from } \\ & \text { original } 159 \text { - } \\ & \text { reasons reported) } \end{aligned}
Inclusion criteria:
≥18yrs\geq 18 y r s
Obese - BMI ≥30\geq 30
Legal competence
Absence of preoperative signs of inflammation
NPWT: n=75n=75
Control: n=75n=75
Method of randomization
Alternate assignment according to time of operation. Patients with diabetes mellitus allocated half and half to groups with priority.
Comparability of groups
There were no statistically significant differences in any preoperative characteristics, co-morbidities or procedure related | removed after Day 6-7
Pressure
125 mmHg
Group B:
Conventional
wound
dressings
Changed initially on 1st 1^{\text {st }} or 2nd 2^{\text {nd }} day postoperatively | changed/ removed up to discharge for healing and signs of infection
Patients contacted by phone at 90 days to ascertain if any infection post discharge
Pre and postoperative days 1, 2, 4, 7 and day of discharge leucocyte and C-reactive protein determined. If infection suspected, measured on an ad-hoc basis.
CDC and Oakley& Wright’s criteria used to categorize level of infectionssuperficial and deep
Infection
Group A: 3/75 (4%)
Group B: 12/75 (16%)
p=0.0266\mathrm{p}=0.0266
OR =4.57(95%Cl=4.57(95 \% \mathrm{Cl}
1.23-16.94)
Gram +ve skin flora | clean, closed incisions for the first 6 to 7 postoperative days reduces the likelihood of postoperative wound infection after median sternotomy in a high-risk group of obese patients. |

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

Appendix VI: Excluded studies

Studies excluded at full-text review:

Colli A. First experience with a new negative pressure incision management system on surgical incisions after cardiac surgery in high risk patients. J Cardithorac Surg. 2011; 6:160.

Reason for exclusion: Case series ( n=10n=10 ) - no comparator group
Canonico S. Therapeutic possibilities of portable negative pressure wound therapy: initial multidisciplinary observations with the negative pressure therapy device. Acta Vulnologica. 2012;10(2):57-66.

Reason for exclusion: Case series ( n=22n=22 ) - no comparator group
DeCarbo WT, Hyer CF. Negative pressure wound therapy applied to high-risk surgery. J Foot and Ankle Surg. 2010; 49:299-300

Reason for exclusion: Article describing technique and application in surgical specialization Goldstein, JA, Iorio ML, Brown B, Attinger, CE. The sue of negative pressure wound therapy for random local flaps at the ankle region. J Foot Ankle Surg. 2010; 49: 513-6.

Reason for exclusion: Complex wounds some required debridement before surgery.
Gomoll AH, Lin A, Harris MB. Incisional vacuum-assisted closure therapy. J Orthop Trauma. 2006; 20:705-9.

Reason for exclusion: Case report - no comparator group
Haghshenasskashani A, Varcoe RL. A new negative pressure dressing (Prevena TM { }^{\text {TM }} ) to prevent wound complications following lower limb distal arterial bypass. Br J Diabetes Vasc Dis. 2011; 11(1): 21-4.

Reason for exclusion: Case report ( n=1n=1 ) - no comparator group
Howell RD, Hadley S, Strauss, E, Pelham FR. Blister formation with negative pressure dressings after total knee replacement. Curr Ortho Prac. 2011; 22(2): 176-9.

Reason for exclusion: Study discontinued prior to predetermined number for statistical significance being reached (due to 63%63 \% of patients developing skin blisters)

Hudson DA, Adams KG, Van Huyssten A, Martin R, Huddleston EM. Simplified negative pressure wound therapy: clinical evaluation of an ultraportable, no-canister system. Int Wound J. 2013: doi: 10.1111/wj.1208010.1111 / \mathrm{wj} .12080

Reason for exclusion: Did not meet all inclusion criteria ( 20%20 \% of patients did not have a closed surgical incision and outcomes focused on testing of device)

Hurd T, Chadwick P, Cote J, Cockwill J, Mole TR, Smith JM. Impact of gauze-based therapy applied to high-risk surgical incisions. Int Wound J. 2010;7:448-455.

Reason for exclusion: Non-comparative study and did not meet inclusion criteria (included patients with chronic wounds and intervention of interest gauze-based NPWT)

Lopez-Cano M, Armengol-Carrasco M. Use of vacuum-assisted closure in open incisional hernia repair: a novel approach to prevent seroma formation. Hernia. 2013;17:129-31.

[1]

1. Sandy-Hodgetts and Watts. Effectiveness of negative pressure wound therapy/closed incision management in the prevention of post-surgical wound complications: a systematic review and meta-analysis © the authors 2015 doi: 10.11124/jbisrir-2015-1687 ↩︎

Reason for exclusion: No comparator group and outcomes reported on not relevant to review.
Marsden D, Goldstein j, Endara M, Xu K, Steinburg J, Attinger C. Negative pressure wound therapy for at-risk surgical wound closures in patients with multiple comorbidities. Annals Surg. 2012; 255: 1043-7.

Reason for exclusion: Sample included patients with chronic wounds and delayed primary closure

Moues CM, van den Bemd GJ, Heule F, Hovius SE. Comparing conventional gauze therapy to vacuum-assisted closure wound therapy: a prospective randomized trial. J Plast, Reconstruct & Aesthet Surg. 2007;60:672-81.

Reason for exclusion: Treatment followed debridement of wounds
Pauli EM, Krpata DM, Novitsky YW, Rosen KJ. Negative pressure therapy for high risk abdominal wall reconstruction incisions. Surg Infection. 2013; 14(3):270-4.

Reason for exclusion: Existing wound complications