Abstract
Advances in preoperative care, surgical techniques and technologies have enabled surgeons to achieve primary closure in a high percentage of surgical procedures. However, often, underlying patient comorbidities in addition to surgical‐related factors make the management of surgical wounds primary closure challenging because of the higher risk of developing complications. To date, extensive evidence exists, which demonstrate the benefits of negative pressure dressing in the treatment of open wounds; recently, Incisional Negative Pressure Wound Therapy (INPWT) technology as delivered by Prevena™ (KCI USA, Inc., San Antonio, TX) and Pico (Smith & Nephew Inc, Andover, MA) systems has been the focus of a new investigation on possible prophylactic measures to prevent complications via application immediately after surgery in high‐risk, clean, closed surgical incisions. A systematic review was performed to evaluate INPWT's effect on surgical sites healing by primary intention. The primary outcomes of interest are an understanding of INPWT functioning and mechanisms of action, extrapolated from animal and biomedical engineering studies and incidence of complications (infection, dehiscence, seroma, hematoma, skin and fat necrosis, skin and fascial dehiscence or blistering) and other variables influenced by applying INPWT (re‐operation and re‐hospitalization rates, time to dry wound, cost saving) extrapolated from human studies. A search was conducted for published articles in various databases including PubMed, Google Scholar and Scopus Database from 2006 to March 2014. Supplemental searches were performed using reference lists and conference proceedings. Studies selection was based on predetermined inclusion and exclusion criteria and data extraction regarding study quality, model investigated, epidemiological and clinical characteristics and type of surgery, and the outcomes were applied to all the articles included. 1 biomedical engineering study, 2 animal studies, 15 human studies for a total of 6 randomized controlled trials, 5 prospective cohort studies, 7 retrospective analyses, were included. Human studies investigated the outcomes of 1042 incisions on 1003 patients. The literature shows a decrease in the incidence of infection, sero‐haematoma formation and on the re‐operation rates when using INPWT. Lower level of evidence was found on dehiscence, decreased in some studies, and was inconsistent to make a conclusion. Because of limited studies, it is difficult to make any assertions on the other variables, suggesting a requirement for further studies for proper recommendations on INPWT.
Keywords: Closed wounds, Incisional Negative Pressure Wound Therapy, Surgical incision, Surgical wound infection, Wound healing
Introduction
Incisional wound healing is an orchestra of biological and molecular events such as cell migration, proliferation and of extracellular matrix storing and remodelling. Certain pathophysiological and metabolic conditions can alter this healing milieu and thereby impair or delay healing.
The increase in number and the complexity of trauma and the improved techniques and technology that allow for surgical procedures on patients with a higher baseline risk of surgical site complications, have contributed to the escalating complexity of wounds, which surgeons are expected to manage 1. Often, the management of these patients remains challenging because of the high rate of post‐operative wound complications development.
Risk factors used to asses surgical wounds' post‐operative complications risk can be classified as trauma‐related (soft tissue injury or fracture, type) surgery‐related (incision placement, surgical site contamination, technique, operative time, estimated blood loss) or patient‐related (morbid obesity, multiple significant comorbidities, drugs, nicotine abuse).
Primary closed incisions with a high risk of complications include those from hip and knee arthroplasty 2, lower extremities bypass 3, abdominal laparotomy 4, 5, and cardiothoracic procedures 6, in particular those performed during the harvesting of bilateral internal mammary arteries 7. In addition, surgical defects such as an excessive suture tension or a protracted hospital stay may adversely affect incisional healing.
It has been shown that there is an increased risk of infection in patients presenting morbid obesity, diabetes mellitus, peripheral vascular disease or coronary artery disease, renal failure, severe chronic obstructive pulmonary disease, extended use of mechanical ventilation and preoperative malnutrition 8, 9, 10, 11. All these comorbidities in addition to risk factors like nicotine abuse, radiation or chemotherapy, and use of steroid or immunosuppressive drugs, present potential challenges in maintaining incision closure after an open surgical procedure 12, 13, 14.
Incisional closure complications can include post‐operative superficial surgical site infection (SSI) 15, 16, 17, 18, 19, 20, which accounted, as reported by Stannard et al., 15 for 17–22% of health care‐associated infections 16, 17, 18, wound cellulitis 21, surgical wound separation or fascial dehiscence that range from 0·25% to 3% (post laparotomies), 1·6% to 42·3% (post‐Caesarean incisions) and 0·5% to 2·5% (after sternal incisions) 15, 22, 23, 24, formation of haematomas or seromas, skin and fat necrosis, and can lead to delayed or impaired healing of the incision.
Methods to close an incision may range from sutures 25 to nitinol staples, adhesive strips, liquid skin adhesive 26 or a combination thereof. Wilkes et al. 27 demonstrated that in patients with a higher baseline risk of surgical site complications, the use of suture and staples induces elevated stress concentrations that can cause ischemia, fibrosis, or other tissue injury. The management of clean, closed surgical incisions diversify from preoperative prophylactic precautions as well as microbial sealants 28, intra‐operative devices like prophylactic gentamycin‐collagen sponges 29 to post‐operative measures. Post‐operative measures range from conventional dressing of sterile dry gauzes 5, debriding agents and topical antimicrobial dressing, to more advanced wound dressings in an effort to stimulate the proliferative phase of wound healing, including hydrocolloids 5, topical application of autologous blood products 30, growth factors 31, cultured skin 32 and Negative Pressure Wound Therapy (NPWT) 3, 6, 33. The evidence that supports the benefits of Negative Pressure Wound Vacuum Therapy in improving healing, as an adjunctive therapy, in the management of difficult open wounds, has been widely described in literature 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46; however, its application in closed incisions is not characterised so well. Since the introduction of this portable and practical device in clinical practise in the 1990s, the acute and chronic open wounds management's landscape has been dramatically revolutionised 44, 47, 48, 49, 50, 51. NPWT involves the controlled application of intermittent or continuous sub‐atmospheric pressure to the wound bed typically via a pressure‐manifolding dressing. Two main mechanisms are proposed to explain the accelerated rate of wound healing: a fluid‐based mechanism with the removal of the excessive interstitial fluid and toxic inflammatory mediators from the subcutaneous tissue and a wound surface's microdeformation mechanism, which is cited as a cellular proliferative mechanism 52. Besides, NPWT promotes a moist wound‐healing milieu, decreases bacterial colony counts, reduces the permeability of blood vessels and increases granulation tissue, cutaneous blood flow to the wound margins 53 and angiogenesis 54, 55, 56. The formation and organisation of the platelet plug between skin edges, is also enhanced, probably for the increased vascular perfusion 57. Besides, NPWT acts by stimulating cell‐mediated immune response and fibroblast viability, migration and proliferation already 48 hours after its application 58. Additionally, the mechanical friction of gauze (under negative pressure) on either side of the wound may contract and even act as a splint against tensile forces across the wound 57. This technology has been rapidly introduced into a wide array of conditions, such as open acute and chronic wounds, burns, pressure ulcers, skin grafts, large abdominal hernias and complex abdominal wall reconstruction 44, 47, 59. While NPWT technology is an established and accepted treatment for non‐healing wounds and open surgical incisions following infection or breakdown, a small but growing number of clinical studies have been published based on the hypothesis that negative pressure dressings improve healing of closed (sutured) wounds. These studies evaluated a novel application of NPWT immediately after surgery to high‐risk surgical closed incisions (Incisional Negative Pressure Wound Therapy, INPWT) as delivered by Prevena™ (Incision Management System, Kinetic Concepts Inc. USA, San Antonio, TX) and Pico systems (Smith & Nephew Inc, Andover, MA) as a prophylactic measure specifically designed to help prevent the development of wound healing complications like infection or dehiscence 15. Prevena™ Incision Management system consists of a vacuum therapy suction unit that is connected to a dressing tube by a canister for fluid collection, and a precut peel‐and‐place reticulated open‐cell foam dressing specifically designed for use over closed surgical incisions that are at high risk for post‐surgical complications. To provide flexibility for application to anatomical contours, the dressing has a plated non‐adherent layer surrounding the foam and a semi‐permeable adhesive drape. The dressing contains ionic silver (0·019%) to prevent bacterial growth and the system is supplied with a carrying case to minimise the effects on patient mobility. In particular, the use of Prevena™ intends to provide an innovative and effective negative pressure dressing to improve incisional healing by protecting the wound from external contamination through the maintenance of a closed and sterile environment, keeping the wound edges together, equalising the strain in the tissue and off‐loading midline tension on the skin incisions, thus diminishing resistance and tension on the wound overall as well as via the application of the beneficial effects of NPWT (removing fluids and components in these fluids by the application of negative pressure therapy preset at −125 mmHg, stimulation of cell proliferation, reduction of inflammatory mediators, increasing arterial and subcutaneous oxygen partial pressure, reduction of the wound stress), which have been already demonstrated over the past 15 years of clinical experience.
Pico systems is canister‐free, the pump generates an effective negative pressure of –80 mmHg (for 7 days of therapy) and is connected to a dressing that manages the fluid away from the wound or closed incision through a unique combination of absorbency and evaporation. Patients can be safely discharged with PICO in place.
Although the exact criteria for INPWT initiation are still being defined, patients with a clean, closed post‐operative incision and multiple surgical wound's post‐operative complications risk factors were however considered candidates for INPWT.
Previous reviews visited the topic: Webster et al. 60 evaluated the efficacy of INPWT on surgical incisions healing but due to the poor number of studies included and the small samples size, INPWT could not be considered to play an effective role in primary surgical wounds healing. Ingargiola et al. 61 have recently made a systematic review to evaluate the effect of INPWT on preventing surgical sites complications.
Both reviews measured the efficacy of INPWT basing it properly on the incidence of surgical site complications; however there were no primary clinical outcomes of interest from animal and biomedical engineering studies that provided a direct explanation of the possible mechanisms of action of INPWT, but no interest was direct to an explanation of INPWT possible mechanisms of action or to animal and engineering studies.
Besides, since the release of these review articles, several new studies have been published assessing the effect of INPWT on high‐risk surgical incisions so we considered it to be appropriate to re‐examine the topic. We performed a systematic review to evaluate the effect of INPWT on surgical sites healing by primary intention. The primary clinical outcomes of interest from animal and biomedical engineering studies are an explanation of the possible mechanisms of action of INPWT on surgical incision and of its potential benefits on healing milieu. Human studies have been investigated in order to evaluate the influence of INPWT not on the cosmetic appearance of the incisions, which was regarded as a subjective evaluation parameter, unreliable and not reproducible, but on the incidence of post‐operative complications (infection, dehiscence, seroma, hematoma, skin and fat necrosis, skin and fascial dehiscence or blistering) as well as on other variables (re‐operation and re‐hospitalization rates, time to dry wound, cost saving).
Materials and methods
Research methodology
A search was conducted for published articles in various databases including the Medline/PubMed (MeSH database), Google Scholar and Scopus databases from 2006 to March 2014. The search was performed in April 2014 using the key words ‘incisional negative pressure wound therapy’, ‘incisional wound therapy’, ‘Prevena’, ‘Pico’, ‘negative pressure wound therapy’, ‘vacuum therapy’, ‘negative pressure dressing’, ‘topical negative pressure’, ‘negative pressure therapy’, ‘VAC’, ‘vacuum‐assisted closure’, ‘vacuum pressure dressing’, ‘vacuum‐assisted closure therapy’, each one of these combined with ‘closed incision(s)’, ‘closed wound(s)’, ‘surgical incision(s)’, ‘wound healing’, ‘wound complication(s)’, ‘surgical wound dehiscence’, ‘surgical wound infection’, ‘surgical site infection’, ‘wound cellulitis’, ‘haematoma’, ‘seroma’, ‘skin necrosis’, ‘fat necrosis’ and ‘blistering’.
Further articles were collected for inclusion from conference proceedings.
Additional citations review and references' review of identified articles was performed and if a new article contained at least one key word from the above, it was included.
Inclusion and exclusion criteria, extrapolation data and quality valuation
The collected studies were reviewed and each study abstract and the full‐text version were evaluated for inclusion on the basis of set inclusion and exclusion criteria (Table 1).
Table 1.
Inclusion and exclusion criteria
| Inclusion criteria | Exclusion criteria |
|---|---|
|
|
NPWT, Negative Pressure Wound Therapy.
No filter was put on the design of study and on the model investigated (human, animal or engine) but data extraction was performed in a standardised and reproducible form, separating the articles on animal and engineering models from those on human models because the purpose of these types of studies were different. Otherwise, only articles in which INPWT was used as a preventive measure on a closed (sutured) incision and applied immediately in the post‐operative phase were included. If it was a human study, this had to have a sample of at least ten patients. Additional filters included articles in the English language from 2006 to March 2014. Non‐English language articles and articles published prior to 2006 were excluded.
Data items extrapolated from animal and biomedical engineering studies incorporated study design, model investigated, testers used to perform the simulations, clinical characteristics of the animals, surgical incision simulation, type of INPWT used and dressings used in the control group (CG), and an explanation of the possible mechanism of action of INPWT (Table 2).
Table 2.
Data item extrapolated from animal and biomedical engineering studies
| Publication date |
| Model investigated |
| Testers used to perform the simulations |
| Study design |
| Epidemiology (age, gender) |
| Intervention |
| Surgical incision simulation |
| NPWT type, time and pressure setting |
| Dressing configuration in the controls |
| Discontinuation criteria |
| Possible mechanisms of action of INPWT |
| Outcomes |
| Infection |
| Dehiscence |
| Seroma and hematoma |
| Skin breakdown (necrosis, blister) |
| Re‐operation |
| Time to dry wound |
INPWT, Incisional Negative Pressure Wound Therapy.
Data items extrapolated from human studies comprehended study design, epidemiology and patients' comorbidities, surgical viewpoint, INPWT type and standard dressings used in the CG, influence of INPWT on surgical wound complications and on potential cost savings (Table 3).
Table 3.
Data item extrapolated from human studies
| Publication date |
| Study design |
| Statistical test used |
| Epidemiology (age, gender) |
| Patient comorbidities |
| Obesity, diabetes mellitus, vascular or respiratory disorders, immunosuppression, nicotine abuse |
| Type of surgery, number and placement of surgical incisions |
| Intervention |
| INPWT type and pre‐setting |
| INPWT discontinuation criteria |
| Dressing configuration in CGs |
| Outcomes |
| Average follow‐up weeks |
| Total wound complications |
| Infection |
| Dehiscence |
| Seroma and hematoma |
| Skin breakdown (necrosis, blister) |
| Re‐operation, re‐hospitalization |
| Time to dry wound |
| INPWT potential cost savings |
| Contraindications |
| Complications of INPWT use |
INPWT, Incisional Negative Pressure Wound Therapy.
Results
Search results and study selection
The search was performed on April 2014 and, after application of filters of inclusion criteria and citation review of identified articles, a total of 18 studies remained: 1 biomedical engineering study (prospective cohort study 27), 2 animal studies (prospective cohort studies 57, 62) and 15 human studies (6 randomized controlled trials 3, 33, 63, 64, 65, 66, 2 prospective cohort studies 67, 68, 7 retrospective analyses 6, 69, 70, 71, 72, 73, 74). Study design and publication date of each study are reported in Table 4a for animal and biomedical engineering studies and in Table 5a for human studies.
Table 4.
Animal and biomedical engineering studies
| (a) | |||||||
|---|---|---|---|---|---|---|---|
| Reference (in publication order) | Publication date | Model investigated | Testers used to perform the simulations | Study design | Age range, mean (years) | Gender, % (male; female) | N 0 animals or engineering models/N 0 incisions |
| Wilkes et al. 27 | 2012 March | FEA‐1 (simulator of epidermis and adipose tissue), FEA‐2 (multiple layers of tissue that included the non‐linear mechanical behaviour of epidermis 0·2 mm, dermis 2·9 mm, fat layer above the fascial separation 9·9 mm, fat layer below fascial separation 10 mm, muscle 10 mm), Benchtop Modelling (mixture of room‐temperature‐vulcanized liquid silicone and PlatSil Gel 10 Deadener simulating 2 mm skin, 10 mm fat, 10 mm muscle) | Abaqus/Explicit version 6.7 and 6.9 (Dassault Systèmes Simulia Corp, Providence, RI) | PC | ND | ND | 3/3 |
| Meeker et al. 57 | 2011 December | Yorkshire Pig (weight range: 130–165 pounds) | Tensile strength testing performed by servohydraulic materials testing apparatus (MTS model 812, Eden Prairie, MN), data collected by an analog to digital conversion setup (Instron 8500 Plus, Norwood, MA), and ImageJ (National Institution of Health, Bethesda, MD) digital imaging software | PC | ND | Female | 6/56 (28 pairs) |
| Kilpadi and Cunningham 62 | 2011 September | Domestic Pig: 50% Great White, 25% Landrace, 25% Yorkshire (weight range: 35–45 kg) | ND | PC | ND | Female | 8/32 |
| (b) | ||||||
|---|---|---|---|---|---|---|
| Reference (in publication order) | Surgical incision simulation | INPWT type | MmHg presetting, Time of INPWT | Control group | Post‐op intervention group(s) (N 0 of incisions) | Possible INPWT's mechanisms of action |
| Wilkes et al. 27 | Open incision 25 mm deep × 2 mm wide in FEA‐1; vertical incision to the upper fat layer,2 mm wide by applying skin tension 0 to −150 kPa over 0·2 s to the dermis and epidermis exposures at the model sides in FEA‐2; incisions of 9 inches down to the muscle layer closed alternatively with sutures or staples in Benchtop model | Prevena™* | −125 in FEA‐1, ND in FEA‐1; −125 in FEA‐2, starting at 0·4 s and attaining target negative pressure at 1 s; −125 in Benchtop model, ND in Benchtop model | ND in FEA‐1; simulated closure of the incisions with suture without dressings in FEA‐2; simulated closure of the incisions with suture or staples without dressings in Benchtop model | ND | 50%↓ of the lateral stress around the incision and in the fat layer; normalisation of the stresses direction; ↑the force required to disrupt the incision by 43% to 51% as compared with closure alone |
| Meeker et al. 57 | Five pairs of elliptically shaped excisional incisions down to paraspinous muscular fascia; to simulate muscle injury and bleeding, a 3 cm long and 2 cm deep incision through the fascia and perpendicular to the fibers of the paraspinous muscle was made, the dermal edges was undermined 2 cm on both sides and 10·000 UI heparin was administered. Perpendicular to the longitudinal axis of the animal on each side of the midline of the spine, spaced from each other by at least 7 cm. | ND | −125; 3 days | Ordinary gauze dressing | ND | ↑ of 142% wound's tensile resistance for maximum load at failure (0·470 versus 0·348 of theCG); ↑ of 176% energy to failure (0·85 mj/mm in controls versus 1,128); ↑ wound appearance |
| Kilpadi et al. 62 | Two 5 cm incisions per side – cranial and caudal – on the abdomen abutting mammary tissue, 3–5 mm deep down to the level of underlying muscle, and creating underlying dead spaces. Incisions closed by simple interrupted sutures prior to the introduction of the nanospheres. | Prevena™ incision dressing* | −125; 4 days | SFD (Tegaderm™ Dressing, 3 M, St. Paul, MN) |
SFD (n = 16) INPWT (n = 16) |
Remodelling and enhancing macromorphological change of lymph structures resulting in an increased clearance |
| (c) | ||||||
|---|---|---|---|---|---|---|
| Reference (in publication order) | Infection, (%) | Dehiscence, (%) | Seroma; hematoma (%) | Skin necrosis; skin blistering, (%) | Re‐operation, (%) | Time to dry wound (days) |
| Wilkes et al. 27 | ND | ND | ND | ND | ND | ND |
| Meeker et al. 57 | ND | ND | ↓15% hematoma cross‐sectional areas (1·31 cm2 of controls versus 0·937 cm2 of NPWT) | ND | ND | ND |
| Kilpadi et al. 62 | ND | ND | 25 (mean) ± 8 g (SE) less hematoma/seroma (↓63% of hematoma/seroma mass: 15 ± 3 g versus 41 ± 8 g) | ND | ND | ND |
FEA, finite element analyses; ND, not defined; INPWT, Incisional Negative Pressure Wound Therapy; PC, prospective cohort; SFD, semipermeable film dressing; ↓, decrease; ↑, increase.
Prevena™ Incision Management System, Kinetic Concepts Inc., San Antonio, TX.
Table 5.
Human studies
| (a) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Reference (in publication order) | Publication date | Study design | Age range; mean, years | Gender, % (male; female) | Mean BMI (Kg/m2) | DM, % | PVD; CAD, % | Immunocompromised, % | Smoking; COPD, % |
| Lewis et al. 69 | 2014 March | R | ND | 0;531 | 35·9 (median 33·6)* | ND | ND; ND | ND | ND; ND |
| Condé‐Green et al. 70 | 2013 October | R |
CG 23–81; 55 INPWT 21–72; 54 |
22;33* |
CG 36·1 INPWT 36·4* |
21·1* | ND; 10·8* | 3·1 (immunosuppression drugs)* | 13·8*; 4·6* |
| Blackham et al. 71 | 2013 June | R |
CG ND; 57·1 ± 13·4 INPWT ND; 57·1 ± 12·7 P = 0·980* |
ND |
CG 26·8 ± 5·5 INPWT 28·3 ± 5·7 P = 0·072* |
CG n = 12 (14) INPWT n = 17 (16) P = 0·624* |
ND; ND | ND |
CG n = 22 (26) INPWT n = 16 (15) Ex‐smoker: CG n = 18 (21) INPWT n = 16 (15) |
| Grauhan et al. 63 | 2013 May | RCT |
CG 54–81; 67 INPWT 44–84; 68 P = 0·59 |
CG 32; 43 INPWT 26; 49 P = 0·40 |
CG 36 (30–45) INPWT 37 (30–62) P = 0·22 |
CG n = 40 (53) INPWT n = 41 (55) P = 0·25 |
ND; LVEF < 30%: CG n = 5 (7) INPWT n = 8 (11) P = 0·56 |
ND |
ND; CG n = 22 (29) INPWT n = 15 (20) P = 0·25 |
| Tauber et al. 72 | 2013 March | R | CG ND; 59·8 ± 10·4* INPWT ND; 60·5 ± 11·9* P = 0·891 | ND |
CG 26·5 ± 4·4* INPWT 28·9 ± 8·0* P = 0·486 |
ND | ND; ND | ND | ND; ND |
| Vargo 73 | 2012 December | R | ND; ND | ND | ND | ND | ND | ND | ND |
| Masden et al. 64 | 2012 June | RCT |
CG 38–86; 61·3* INPWT 40–101; 61·3* P = 0·98 |
P = 0·43 |
P = 0·63 |
CG 64·9* INPWT 79·6* P = 0·12 |
CG 54·0* INPWT 47·7* P = 0·57; CG 16·2* INPWT 11·4* P = 0·53 |
CG 8·1* INPWT 9·1* P = 1·00 |
P = 0·57; ND |
| Pachowsky et al. 65 | 2012 April | RCT | ND; CG 70·0 ± 11·01 INPWT 66·22 ± 17·83 | ND | ND | ND | ND | ND | ND |
| Stannard et al. 33 | 2012 January | RCT | 18–80; 43* | 65;35* | ND | 3·3 | ND; ND | ND | 52*; ND |
| Colli and Camara 67 | 2011 December | PC | 55–78; 66·2 | 5;5 | ND | n = 9 (90%) | n = 9 (90%); n = 8 (80%) | ND | ND; n = 3 (30%) |
| Howell et al. 66 | 2011 March | RCT | CG 55–73; 66 | CG 50;50 | CG 50% with BMI 30–40 INPWT 100% with BMI > 30 | CG ND INPWT0 | CG 90 INPWT ND; CG 100 INPWT ND | ND | ND; CG 30 INPWT ND |
| Goldstein et al. 68 | 2010 November | PC | 40–83; 59 | 60;40 | ND | 40 | ND; ND | ND | ND; ND |
| Reddix et al. 74 | 2009 September | R | 20–72; 41 | 21;79 | 48·7 | ND | ND; ND | ND | ND; ND |
| Atkins et al. 6 | 2009 June | R | ND; 60 | 89·5;10·5 | 35·3 | 54·4 | 21;100 | ND | ND; ND |
| Stannard et al. 3 | 2006 June | RCT | 19–78; 41 | 73;27 | ND | ND | ND; ND | ND | ND; ND |
| (b) | ||||||||
|---|---|---|---|---|---|---|---|---|
| Reference (in publication order) | N0 patient/ N 0 incisions | Area of surgical incision; Type of surgery | INPWT type | mmHg Pre‐ setting (type of suction), time of INPWT | CG | Average follow up (weeks) | Postoperative intervention group(s) (N 0 of incisions) | Statistical test used |
| Lewis et al. 69 | ND | Abdomen; laparotomy for endometrial cancer | Prevena™(Prevena™ Incision Management System, Kinetic Concepts Inc., USA, San Antonio, TX), Pico System© (Smith & Nephew Inc, Andover, MA) | ND, 7 days | Routine care | ND | ND | ND |
| Condé‐Green&& et al. 70 | 56/56 | Abdomen; abdominal wall reconstruction after initial (40% of patients), recurrent (58%) or incarcerated recurrent (1·5%) ventral hernia | Vac Therapy (KCI USA, Inc., San Antonio, TX) with non adherent dressing (Adaptic, Johnson & Johnson, New Brunswick, NJ) | −125, 5 days | Conventional dressing of dry gauze | 60 |
CG (n = 33) INPWT (n = 23) |
χ 2 for categorical variables, t‐test for continuous variables with statistical significance for p < 0·05 |
| Blackham et al. 71 | 189/191 | Abdomen; laparotomy for colorectal cancer, pancreatic cancer, or peritoneal carcinomatosis |
VAC system (Kinetic Concepts, Inc, San Antonio, TX) with nonadhesive, permeable Dressing (Adaptic, Johnson & Johnson) |
−125 (continuous), 4 days | Standard sterile dressing | ND |
CG (n = 87) INPWT (n = 104) |
t‐tests or Mann–Whitney U‐tests for continuous variables, χ 2 or Fisher exact tests for categoric variables |
| Grauhan et al. 63 | 150/150 | Sternum; median sternotomy for coronary artery bypass grafting or valve surgery in high‐risk group of obese patients | Prevena, KCI, Wiesbaden, Germany | −125, 6–7 days | Conventional sterile dry wound dressing | 12·8 |
CG (n = 75) INPWT (n = 75) |
Mann–Whitney U‐test and Fisher exact test for dichotomous data; freedom from infection by Kaplan–Meier analysis, log‐rank test to compare patient groups |
| Tauber et al. 72 | 24/45 | Groin; uni‐ or bilateral inguinal LND for penile cancer or cancer of the urethra‡ | Polyvinyl alcohol dressing (V.A.C.® White Foam Dressing, KCI Medizinprodukte GmbH, Wiesbaden, Germany) connected to ActiVAC | −100 (continuous, intensity +++), 7 days | Compression dressing | 11·7 |
CG (n = 30) INPWT (n = 15) |
t‐Tests†, Mann–Whitney U‐tests‡, Fisher's exact test§ with a significance level for α = 0·05 |
| Vargo 73 | 30/30 | Abdominal; Skin flaps after complex abdominal reconstruction | Vac Therapy (KCI USA, Inc., San Antonio, TX) | −75 (continuous), 5·6 days (range 5–7 days) | ND | 4 | ND | χ2 analysis |
| Masden et al. 64 | 81/81 | Abdomen, groin, trunk, back, lower extremities; Closure of vascular bypass wounds and Lower extremities amputations proximal to the forefoot‡ | V.A.C. KCI,San Antonio, Tx | −125, 3 days |
Standard dry dressingconsisting of a non adhesive silicone Layer (Mepitel, MỞlnlycke Health Care AB, GỞteborg, Sweden) and a bacterostatic single silver layer (Acticoat, Smith & Nephew, Hull, UK) |
16·1 |
CG (n = 37) INPWT (n = 44) |
χ2, Fischer |
| Pachowsky et al. 65 | 19/19 | Lower extremities; THA for osteoarthritis of the hip‡ | Prevena™ | −125, 5 days | Dry wound coverage | 1·4 |
CG (n = 10) INPWT (n = 9) |
Mann–Whitney U‐test |
| Stannard et al. 33 | 263/263 | Lower extremities; ORIF for lower extremities trauma reconstruction | ND | −125, 2 days | Standard dry dressing | ND |
CG (n = 122) INPWT (n = 141) |
ND |
| Colli and Camara 67 | 10/10 | Sternum; sternal surgical incision for CABG and/or AVR and/or MVR | Prevena™ | −125, 5 days | ND | 4 | INPWT (n = 10) | ND |
| Howell et al. 66 | 51/60 | Lower extremities; TKA | ND | −125, 2 days | Sterile gauze dressing | 48 |
CG (n = 36) INPWT (n = 24) |
ND |
| Goldstein et al. 68 | 10/17 | Lower extremities; local random fasciocutaneous flap for reconstruction of complex ankle wounds | ND | −125; 4 days | Standard dry dressing | 22 | INPWT (n = 17) | ND |
| Reddix et al. 74 | 19/19 | Lower extremities; ORIF acetabular fractures | ND | −75; ND | Standard dry dressing | 84 | INPWT (n = 19) | ND |
| Atkins et al. 6 | 57/57 | Sternum; CABG | ND | −125; 4 | Standard dry dressing | ND | INPWT (n = 57) | ND |
| Stannard et al. 3 | 44/44 | Lower extremities; ORIF for lower extremities trauma reconstruction | ND | ND; 2 | Standard dry dressing | ND |
CG (n = 24) INPWT (n = 20) |
ND |
| (c) | ||||||||
|---|---|---|---|---|---|---|---|---|
| Reference (in publication order) | Total wound complications (%) | Infection, (%) | Dehiscence, (%) | Seroma; hematoma, (%) | Skin necrosis; skin blistering, (%) |
Re‐operation; re‐hospitalization (%) |
Time to dry wound (days) | INPWT cost saving |
| Lewis et al. 69 | n = 134 (31), (36·9 among patients with BMI > 30; 41 among patients with BMI > 40) | n = 87 (64·9) | ND | ND; ND | ND; ND | n = 11;n = 16 | ND | Ata relative risk of wound complications of 0·5: $104 for the full cohort, $163 in the obese cohort and $203 in the morbidily obese cohort |
| Condé‐Green et al. 70 |
CG n = 21 INPWT n = 5 P = 0·020 |
CG n = 1 (4·3) INPWT n = 2 (6) |
CG n = 13 (39) INPWT n = 2 (8·7) P = 0·014 |
CG n = 4 (12) INPWT n = 0 P = 0·14; CG n = 0 INPWT n = 0 |
CG n = 6 (18) INPWT n = 2 (8·7); ND P = 0·45 |
CG n = 3 INPWT n = 1 P = 0·63; ND |
ND | ND |
| Blackham et al. 71 |
CG n = 31 (35·6) INPWT n = 25 (24·0) P = 0·050 OR 0·51, 95% CI 0·26–1·00 Among CCCs: CG n = 28 (45·2) INPWT n = 24 (24·0) P = 0·028 OR 0·46, 95% CI 0·23–0·92 |
Total CG n = 23 (26·4) INPWT n = 17 (16·3) P = 0·065, OR 0·48, 95% CI 0·22–1·05 superficial incisional SSIs CG n = 17 (19·5) INPWT n = 7 (6·7) P = 0·019, OR 0·29, 95% CI 0·11–0·81 Incisional SSIs CG n = 17 (19·5) INPWT n = 12 (11·5) P = 0·106 OR 0·48, 95% CI 0·20–1·17 Among CCCs: total CG n = 22 (35·5) INPWT n = 16 (16·0) P = 0·022 OR 0·40, 95% CI 0·18–0·87 superficial incisional SSIs CG n = 17 (27·4) INPWT n = 6 (6·0) P = 0·019 OR 0·23, 95% CI 0·08–0·66 incisional SSIs CG n = 17 (27·4) INPWT n = 11 (11·0) P = 0·048 OR 0·40, 95% CI 0·16–0·99 |
CG n = 24 (27·6) INPWT n = 17 (16·3) P = 0·043 OR 0·45, 95% CI 0·21–0·97 Among CCCs: CG n = 22 (35·5) INPWT n = 16 (16·0) P = 0·028 OR 0·41, 95% CI 0·19–0·91 |
CG n = 3 (3·4) INPWT n = 4(3·8) P = 0·867, OR 0·85, 95% CI 0·13–5·49 Among CCCs: CG n = 3 (4·8) INPWT n = 4 (4·0) P = 0·867, OR 0·85, 95% CI 0·13–5·50; CG n = 2 (2·3) INPWT n = 0 Among CCCs: CG n = 1 (1·6) INPWT n = 0 |
ND; ND | ND; ND | ND | ND |
| Grauhan et al. 63 | ND |
CG n = 12 (16) INPWT n = 3 (4) P = 0·026; OR 4·57; 95% CI, 1·23–16·94 G+: CG n = 10 INPWT n = 1 P = 0·009; OR 11·39; 95% CI, 1·42–91·36 |
CG n = 4 INPWT n = 2 P = 0·061; |
ND; ND | ND; ND |
CG n = 5 (7) INPWT n = 3 (4) P = 0·72; ND |
ND | ND |
| Tauber et al. 72 |
Fewer patients with INPWT experienced inguinal wound complications compared with CG. P = 0·032 |
ND | ND |
LPC: CG (62) INPWT (20) LPR: CG (45) INPWT (7) LPE: CG (46) INPWT (0); ND |
ND; ND |
CG n = 7/30 wounds (23) INPWT n = 1/15 wounds (7) P = 0·631; ND |
CG (25%‐Pe: 6; 50%‐Pe: 7; 75%‐Pe: 18) INPWT (25%‐Pe: 5; 50%‐Pe: 7; 75%‐Pe: 8) P = 0·631 |
ND |
| Vargo 73 | n = 2 (3) |
(0) P < 0·05 |
ND | n = 1 (3·3); ND | (0); ND | ND; ND | ND | ND |
| Masden et al. 64 |
CG n = 13 (35·1) INPWT n = 18 (40·9) P = 0·59 |
CG n = 5 (13·5) INPWT n = 3 (6·8) P = 0·46 (not statistically significant); no difference in the development time |
CG n = 11 (29·7) INPWT n = 16 (36·4) P = 0·53 (not statistically significant); no difference in the development time P = 0·45 |
ND; ND | ND; ND |
CG n = 8 (22) INPWT n = 9 (20·9) of the total wound complication P = 0·89; ND |
4·3 | ND |
| Pachowsky et al. 65 | ND | ND | CG n = 9 (90) mean volume 5·08 ml INPWT n = 4(44) mean volume 1·97 ml P = 0·021; ND | ND; ND | ND; ND | ND | ND | |
| Stannard et al. 33 | ND |
CG n = 23 (18·9) INPWT n = 14 (9·9) P = 0·049 |
CG n = 20 (16·5) INPWT n = 12 (8·6) P = 0·044 |
ND; ND | ND; ND | ND; ND |
CG n = 3 INPWT n = 2·5 |
ND |
| Colli and Camara 67 | 0 | 0 | 0 | ND; ND | ND; ND | 0;0 | 5 | ND |
| Howell et al. 66 | ND |
CG n = 1 (2·8) INPWT n = 1 (4·2) |
ND | ND; ND |
ND; CG n = 3 (12) INPWT n = 15 (63) |
CG 0 INPWT 0; ND |
CG 4·1 INPWT 4·3 |
ND |
| Goldstein et al. 68 | ND | 0 | n = 2 (11·8) | ND; ND | ND; ND | ND; ND | ND | ND |
| Reddix et al. 74 | 0 | 0 | 0 | ND; ND | ND; ND | ND; ND | ND | ND |
| Atkins et al. 6 | 0 | 0 | ND | ND; ND | ND; ND | 0;ND | ND | ND |
| Stannard et al. 3 | ND |
CG n = 3 (12·5) INPWT n = 3 (15) |
CG n = 4 (16·7) INPWT n = 4 (20) |
CG 4·8 days|| INPWT 1·8 days|| P = 0·02 |
ND; ND | ND; ND |
CG 3·1 INPWT 1·6 P = 0·03 |
ND |
AVR, aortic valve replacement; BMI, body mass index; CABG, coronary artery bypass graft; CAD, coronary artery disease; CCCs, clean‐contaminated cases; CG, control group; CI, confidence interval; COPD, chronic obstructive pulmonary disease; DM, diabetes mellitus; G+, gram‐positive skin flora; INPWT, Incisional Negative Pressure Wound Therapy; LVEF, left ventricular ejection fraction; LND, lymphadenectomy; LPC, lymphoceles; LPE, lymphoedema of the lower extremities; LPR, lymphorrhoea; MVR, mitral valve replacement; ND, not defined; OR, odds ratio; ORIF, open reduction internal fixation; P, P‐value; Pe, percentile; PC, prospective cohort; PVD, peripheral vascular disease; R, retrospective; RCT, randomized controlled trial; SSIs, surgical site infections; THA, total hip arthroplasty; TKA, total knee arthroplasty.
No significant difference between control group and INPWT group.
To compare treatment groups for symmetrically distributed quantitative data (age, body, BMI).
To compare treatment groups for duration of drainage and maximal drained fluid.
To compare binary data.
Days of drainage from incision greater than minimal (>2 quarter‐sized drops of drainage).
Study characteristics, intervention groups, and quality
In total, the systematic review investigated the outcomes of 1133 incisions on 2 Finite Element Analysis (FEA) models, 1 Benchtop model, 6 Yorkshire Pigs, 8 Domestic Pigs and 610 patients (see Table 4 for models investigated by animal and engineering studies).
The most common study designs were as follows: retrospective observational studies (38·8%) 6, 69, 70, 71, 72, 73, 74, Randomized Controlled Trials (RCTs) (33·3%) 3, 33, 63, 64, 65, 66 and prospective observational studies (27·7%) 27, 57, 62, 67, 68. 100% of the animal studies 57, 62, 100 % of the biomedical engineering studies 27 and 87% of human studies 3, 6, 33, 63, 64, 65, 66, 68, 69, 70, 71, 72, 74 have a control intervention group for comparison of outcomes with those from the INPWT group (Tables 4b and 5b).
Risk factors used to asses surgical wound's post‐operative complications risk can be associated with any of three factors such as trauma (soft tissue injury or fracture, type), surgical procedure (incision placement, surgical site contamination, technique, operative time, estimated blood loss) or patient‐related (morbid obesity, multiple significant comorbidities, drugs). Of these factors, INPWT use has been investigated most prevalently with respect to injury or fracture. Forty‐six percent of the human studies (n = 7) evaluated the effect of INPWT on lower extremity high‐risk incisions after reconstructive joint or fracture surgery 3, 33, 64, 65, 66, 68, 74. Twenty percent of the human studies (n = 3) evaluated the effect of INPWT on laparotomy for abdominal or genital malignancies 64, 69, 71. Two articles evaluated its use for abdominal incisions, one after abdominal wall reconstruction of recurrent ventral hernias 70 and the other after skin flaps for complex abdominal reconstruction 73. Three studies (20%) 6, 63, 67 used INPWT for sternal incisions after coronary arteries bypass grafting, and one experimented INPWT in the inguinal incision after lymphadenectomy for penile cancer or cancer of the urethra 72. Areas of surgical incision and type of surgery performed, are schematised in Table 5b for human studies.
In terms of the duration and pre‐setting of INPWT, animal experimental studies applied a negative pressure of −125 mmHg for a mean time of 3·5 days 57, 62 (Table 4b). Among human studies, seven applied INPWT for a predetermined 4–6 days at –125 mmHg and then removed the dressing 6, 63, 65, 67, 68, 70, 71. Two studies used INPWT for 7 days (one at −125 mmHg 63, the other at −100 mmHg 72) and one study for 3 days 64. In three studies 3, 33, 66 it was applied for 2 days and then removed and re‐applied for a length of time depending on the amount of drainage noted in the suction canister, and in one study, INPWT was at −75 mmHg and continued until there was no fluid suctioned into the canister for 12 consecutive hours (typically in place for 1–3 days) 74. Mean follow‐up ranged from 1·4 to 84 weeks. INPWT pre‐setting (mmHg, type of suction and time of application) and average follow‐up weeks of each study are reported in Table 4b for animal and biomedical engineering studies and in Table 5b for human studies.
Epidemiology and patients comorbidities
In total, 13 studies (72%) provided data regarding the sex ratio of the study population 3, 6, 33, 57, 62, 63, 64, 66, 67, 68, 69, 70, 74 and 13 studies reported mean age ranging from 54 to 70 years in the CGs and 41 to 68 years in the INPWT groups 3, 6, 33, 63, 64, 65, 66, 67, 68, 70, 71, 72, 74. Mean Body Mass Index (BMI), diabetes mellitus, coronary artery disease, peripheral vascular disease, immunocompromised status, nicotine abuse and chronic obstructive pulmonary disease were reported with variability. Post‐incision use of NPWT with respect to high‐risk factors, including obesity and diabetes, has been investigated by several studies 6, 67, 74. All epidemiological and clinical characteristic data for each study are reported in Table 4a for animal studies and in Table 5a for human studies. Nearly all human studies, except one 68, selected a sample of patients whose surgical incisions were considered by the investigators to be at high risk for complication because of both a large amount of comorbidities and/or by the type of the injury, incision placement, and known propensity for surgical site complications development.
Outcomes
Outcomes and complications are reported in Table 4c for animal and biomedical engineering studies and in Table 5c for human studies, with number and percentage rate listed by the study group.
Infection
Infection of the surgical incision was the commonly reported complication (72% of studies reviewed) 3, 6, 33, 63, 64, 66, 67, 68, 69, 70, 71, 73, 74. NPWT's rationale to prevent SSIs includes completely eliminating dead space, removing fluid and blood, improving blood flow and preventing the formation of subcutaneous seromas/hematomas that become secondarily infected. All the human studies included in the review investigated the incidence of SSIs except two 65, 72. Three of the 7 retrospective studies 6, 73, 74 and 2 of the 2 observational studies 67, 68 documented a 0% incidence of infection in their study population using INPWT. None of these studies had CGs to be compared with.
Stannard et al. 3 randomised 88 orthopaedic trauma patients with draining hematomas or high‐energy fractures to receive a standard dry dressing or INPWT over closed incisions. INPWT was associated with a shorter drainage time; however, there was no statistically significant difference in the rates of infections. A subsequent study from the same group 43 randomised 262 patients with high‐energy lower‐extremity fractures to standard dry dressings or INPWT and reported a lower incidence of SSIs (9·9% versus 18·9%, P value [P] = 0·049) with the use of INPWT. INPWT has also been associated with fewer SSIs compared with standard dry dressings (1·27 versus 6·15%, P = 0·5041) in patients who underwent acetabular fracture repair 75. In addition to the orthopaedic experience using INPWT, Atkins et al. 6 reviewed 57 high‐risk cardiac procedures in which NPWT was used on closed sternotomy incisions for 4 days. Based on the risk assessment model developed by Fowler, three post‐operative sternal wound infections were anticipated; however, none were observed. During the same time period, 213 patients who were not at high risk for sternal wound infections were treated with standard post‐operative wound care, and 1 patient in this group developed a sternal wound infection. They concluded that NPWT was well tolerated and may prevent sternal wound complications in high‐risk patients.
Blackham et al. 71 reported that NPWT was associated with fewer surgical site complications when compared with standard sterile dressing, in patients undergoing colorectal, pancreatic, or cytoreductive surgery (Table 5c): 16·3% versus 26·4% for global infection incidence, 6·7% versus 19·5% (P = 0·015) for superficial incisional SSIs incidence and 11·5% versus 19·5% for incisional SSIs incidence. In particular, clean‐contaminated operations appear to benefit the most from INPWT: 16·0% versus 35·5% for global infection incidence, 6·0% versus 27·4% for superficial incisional SSIs incidence and 11·0% versus 27·4% for incisional SSIs incidence.
Condé‐Green et al. 70 demonstrated no significant difference in the rate of infection between the INPWT (one infection, 4·3%) and the conventional dressing of dry gauzes (two infections, 6%) groups. In contrast with the previous studies, Howell et al. found a higher percentage of infections in the INPWT group (4·2%) versus sterile gauze dressing 66. In an RCT, Masden et al. demonstrated a lower incidence of infection in the INPWT group as compared with standard dry dressing but the results did not reach a level of statistical significance; no differences were noted in the infections development time between the two groups 64.
In a prospective study, Grauhan et al. 63 analysed the role of NPWT in median sternotomy in a high‐risk group of 150 consecutive obese patients (BMI ≥ 30). Three of 75 patients (4%) with continuous negative pressure wound dressing treatment had post‐sternotomy wound infections compared with 12 of 75 patients (16%) with conventional sterile wound dressing (P = 0·0266). The breakdown of skin sutures with subsequent seepage of bacteria into the deeper layers emerged as the key event in the development of the majority of wound infections after sternotomy, and Gram‐positive bacteria were the most commonly isolated organisms in up to 80% of cases 76, 77, 78. This pathogenesis may explain why the risk of wound infections is especially elevated in obesity, because shear and traction forces on skin sutures are high and there is ample scope for colonization of skin flora within skin folds. By considering wound infection by only Gram‐positive skin flora, infections were found in only one patient in the NPWT treatment group compared with ten patients in the CG (P = 0·0090; OR, 11·39; 95% CI, 1·42–91·36) indicating a considerable impact of prophylactic NPWT dressing treatment in reducing the likelihood of wound infection over clean, closed incisions for the first 6–7 post‐operative days. Besides, in the NPWT group, the incision was primarily closed in 71 of the 75 patients (95%) and not a single wound infection occurred during the further course, indicating that wound closure already represented a sufficient barrier to external infectious sources. Thus, the key event of most infectious complications, which was skin breakdown and subsequent seepage of skin flora into deeper layers, could be prevented in most cases by prophylactic NPWT 76, 77. In contrast, in the CG, 9 of 12 wound infections (75%) occurred beyond the first post‐operative week and up to post‐operative day 35. This indicated that with conventional wound dressing (in the CG) an adequate barrier to external infectious sources is considerably established later, which in turn underlined the positive impact of wound secretion drainage (hematoma, seroma) as well as the improved microcirculation during the course of wound healing that was observed with NPWT in previous studies 3, 43, 65.
Other investigators evaluated the efficacy of NPWT in preventing surgical site complications. Gomoll et al. used INPWT on 35 orthopaedic trauma patients who were at high risk for SSIs and reported that no SSIs developed 2.
Hematoma and seroma
Seroma development was the second most commonly reported complication (55% of studies reviewed) 3, 6, 53, 57, 62, 65, 70, 71, 72, 73. Hematomas and seromas result from the accumulation of blood and serum, respectively, in internal spaces. Even with an excellent surgical technique, bleeding and inflammation, and consequently serum extravasation, may occur, resulting in patient discomfort, increased probability of infection, slower healing, additional clinic visits and surgical re‐interventions.
Recent in vivo studies have provided evidence of improved fluid flow with four days of continuous INPWT (Prevena™ Incision Dressing) under −125 mmHg over clean, closed incisions, showing that its application, when compared with semi‐permeable film dressing (Tegaderm™ Dressing, St. Paul, MN, USA), significantly decreased the amount of porcine subcutaneous dead spaces beneath superficial closed incisions indicating reduced haematoma/seroma 62. Kilpadi and Cunningham 62 demonstrated that NPWT reduced the mass of hematoma/seroma by 63% in domestic pigs (NPWT: 15 ± 3 g, control: 41 ± 8 g, P = 0·002) with minimal, if any, removal of fluid into the canisters but through an increased lymph clearance from the subcutaneous dead space, as measured by the significantly greater incidence in peripheral lymph nodes of both 30‐ (P = 0·04) and 50‐nm (P = 0·05) neutron‐activated nanospheres from NPWT‐treated sites compared with control‐treated sites, and an enhanced macromorphological change of lymph structures. Meeker et al. 57 investigated the role of NPWT in post‐operative primary wound treatment and closure in a porcine model. They found that blinded measurements of wound hematoma cross‐sectional areas were 15% smaller for NPWT‐treated wounds as compared with controls (1·31 cm2 versus 0·937 cm2; P = 0·02) 57. Among human studies the RCT of Pachowsky et al. 65 found a significant reduction in the incidence and mean size of post‐operative seromas when measured by ultrasound with prophylactic INPWT (n = 4, 44%, 1·97 ml) versus conventional dry wound coverage (n = 9, 90%, 5·08 ml) to total hip arthroplasty incisions for osteoarthritis of the hip in 19 obese subjects (P = 0·021) 65. Stannard et al. 3 reported the incidence of minor to marked drainage from the surgical incision. Unfortunately, they did not specify if the drainage represented seroma or hematoma fluid; however, they found a substantial reduction in the number of days with greater than mild drainage from incisions with INPWT versus Standard dry dressing (1·8 versus 4·8 days, respectively; P = 0·02). Vargo, in his retrospective review of prospectively collected data in 30 patients with high‐risk wounds treated with NPWT after complex abdominal reconstruction, reported only one case of seroma (3·3%) 73. In addition, Timmers et al. reported data regarding the incidence of seroma 53. Tauber et al. 72 found in 24 lymphadenectomy for penile or urethra malignancies, that patients treated with conventional wound care showed a slight tendency to higher values of maximum drained fluid per day (25%‐percentile: 30 ml; median: 68 ml; 75%‐percentile: 200 ml versus 25%‐percentile: 35 ml; median: 55 ml; 75%‐ percentile: 78 ml; P = 0·632 with no statistical significance) and duration of drainage (25%‐percentile: 6 days; median: 7 days; 75%‐percentile: 18 days versus 25%‐percentile: 5 days median: 7 days; 75%‐percentile: 8 days; P = 0·496 with no statistical significance). While drainages had to be kept in place for more than 7 days in only 1/15 (8%) inguinal LND wounds treated with epidermal VAC, 15/30 inguinal conventional wound care treated wounds (50%) required a drainage time longer than 7 days. In comparison with only 1/8 (13%) patients of the VAC treated group, 4/16 (25%) patients of the CWC group were discharged with indwelling drainages (P = 0·631). Besides, Epidermal VAC treatment resulted in significantly fewer complications such as formation of lymphoceles (62% versus 20%), persistent lymphorrhoea (45% versus 7%) or lymphoedema of the lower extremity (46% versus 0%) (P = 0·032) 72.
Condé‐Green et al. 70 and Blackham et al. 71 were the sole authors to report the incidence of hematoma too. Condé‐Green et al. reported a zero occurrence of hematoma in both the INPWT group and the CG, and a zero occurrence of seroma in the INPWT group versus 12% (n = 4) in the CG 70. In contrast with the previous studies, Blackham reported three cases (3·4%) of seroma in the CG versus four cases (3·8%) in the INPWT group (P = 0·867, OR 0·85, 95% CI 0·13–5·49) while among clean‐contaminated cases they reported seromas in 4·8% (n = 3) for CG and in 4% (n = 4) in INPWT group (P = 0·867, OR 0·85, 95% CI 0·13–5·50). Incidence of hematoma was 2·3% (n = 2) in CG and 0 in INPWT group while among clean‐contaminated cases 1·6% (n = 1) in CG and 0 in INPWT group 71.
Dehiscence
Among studies reviewed, the rate of dehiscence ranged from 8·6% to 36·4% in the INPWT groups versus 16·5% to 39% in the CGs. Among the four studies with treatment and CGs that reported the incidence of dehiscence, two studies found a statistically significant difference 6, 67. Condé‐Green et al. 70 demonstrated an 8·7% (n = 2) dehiscence rate with INPWT compared with 39% (n = 13) with standard dry dressing (OR = 6·83, 95% CI: 1·3–34·1, P = 0·014) and Stannard et al. 33 demonstrated a 8·6% (n = 12) percent dehiscence rate with INPWT versus 16·5% (n = 20) with conventional dressing (Relative Risk = 1, 95% CI: 1·03–3·55, P = 0·044). According to the results of Grauhan et al., after median sternotomy one patient in the NPWT group and three patients in the CG had sternum dehiscence (P = 0·061). In the NPWT patient, the skin incision was closed after 7 days of NPWT, but sternum dehiscence was diagnosed after 3 weeks and sterile re‐osteosynthesis could be performed. In contrast, in the CG, 3 of 12 wound infections showed sternal bone involvement and skin flora as causative. One may surmise that these three infections could have been prevented by prophylactic NPWT 63. Blackham et al. 71 reported that NPWT was associated with fewer surgical site dehiscence in patients undergoing colorectal, pancreatic or cytoreductive surgery (Table 5c): in total, 24 patients (27·6%) required wound opening after being treated with standard sterile dressings, whereas 17 patients (16·3%) developed open incisions after receiving NPWT dressings (P = 0·043, OR 0·45, 95% CI 0·21–0·97). After adjusting for the demographic and clinical differences between the two groups, the rate of wound opening for any reason was significantly better after using NPWT (P = 5·043) 71.
Masden et al. 64 in an RCT demonstrated a higher incidence of skin dehiscence in the INPWT group (36·4%, n = 16) when compared with standard dry dressing (29·7%, n = 11) but results did not reach a level of statistical significance; no differences were noted in the dehiscence development time between the two groups, P = 0·45 64.
Skin necrosis/blistering
The incidence of skin necrosis and skin blistering was reported by one study 70. Condé‐Green et al. demonstrated no significant difference in skin necrosis between the INPWT and SDD (standard dry dressing) groups 70. Vargo reported no incidence of skin necrosis in the INPWT group 73. Howell et al. 66 experienced an increase rate of skin blistering with application of INPWT (63%) versus with sterile gauze dressing (12%). Blisters were described as linear at the junction between the sponge and adhesive tape, most likely due to friction. The authors mentioned no specific type of therapy or prevention of these blisters 66.
Re‐operation/re‐hospitalization
Eight studies provided data regarding the rate of re‐operation 6, 63, 64, 66, 67, 69, 70, 72 and two studies provided data regarding the rate of re‐hospitalization. In six of these studies, there was zero incidence of re‐operation with the application of INPWT 6, 53, 65, 66, 67, 68. Condé‐Green et al. experienced an increase in the number of patients who underwent re‐operation among conventional dressing group (n = 3) compared with the INPWT group (n = 1), P = 0·63 70. Masden et al. demonstrated no significant difference in the rate of re‐operation between the INPWT and standard dry dressing groups (20·09%, n = 8 versus 22%, n = 9 , P = 0·89) 64.
According to Tauber et al. the re‐operation rate reached about 23% (n = 7/30) in the CG and 7% (n = 1/15) in the INPWT group, P = 0·631 72. Grauhan et al. found a re‐operation rate of 7% (n = 5) in the CG and 4% (n = 4) in the INPWT group, P = 0·72 63.
Time to dry wound
Six studies reported data regarding the time of attainment of a dry wound, which ranged from 2·5 to 7 days in the INPWT groups as compared with 1·6 to 7 days in the CGs 3, 33, 64, 66, 67, 72. Tauber et al. 72 did not find any significant difference in the time to dry wound between the INPWT group and the CG, as shown in the following data: 25%‐Pe: 5, 50%‐Pe: 7 75%‐Pe: 8 and 25%‐Pe: 6, 50%‐Pe: 7, 75%‐Pe: 18, respectively (P = 0·63)s. Colli and Camara found an average time of 5 days to a dry sternal incision after coronary artery bypass graft (CABG) with application of INPWT 67. Among the RCTs, Masden et al. 64 reported a mean time to dry wound of 4·3 days, Stannard et al. 33 and Howell et al. 66 did not find any significant difference in the average time until attainment of a dry incision between the INPWT group (2·5 versus 3 days and 4·3 versus 4·1 days, respectively) 33, 66. A significant reduction in the time to attainment of a dry incision was demonstrated in the 2006 RCT by Stannard et al. 3 with application of INPWT to high‐risk lower extremity fractures after open reduction internal fixation (1·6 versus 3·1 days, P = 0·03) 3.
Pre‐setting and discontinuation criteria
An area of concern is the magnitude of suction that is to be used. Previous studies have reported ranges from 75 to 400 mmHg in closed wounds. 125 mmHg for the Prevena system is based on extensive work by Morykwas et al. 44 Concerns about the possibility of damage to the epidermis have been raised regarding the use of high‐suction magnitudes. The Pico System delivers NPWT at a single preset pressure of −80 mm Hg measured at the bottom of the wound bed. Malmsjö et al. 79 investigated the biological effects of the Pico system compared with the traditional NPWT in the porcine peripheral wound model. They found that the disposable, canister‐less PICO system functioned in the same manner as the traditional NPWT system with regard to fluid handling, pressure transmission to the wound bed (mean of −77·4 ± 1·04 mmHg of Pico system versus −77·6 ± 0·86 mmHg of NPWT recorded at the bottom of the wound by a saline‐filled pressure catheter), tissue contraction and changes in blood flow. Discontinuation criteria for INPWT have not been clearly defined and may vary according to the incision and the patient. INPWT must be continuously active with no additional intervention for a period between 3 and 5 days for up to 8 days. Reported duration of incisional therapy varies between 1 and 5 days in the literature 2, 6, 33, 65, 67, 74. Reddix et al. 74 reported discontinuation of INPWT at the point when no oedema fluid was evident in the canister for 12 hours, which is usually a time period of 24–72 hours after surgery. The Level 1 study by Stannard et al. 33 had specific discontinuation criteria that involved a surgical incision with minimal drainage. However, that study was started prior to the availability of home NPWT and small portable units. Study patients only used the NPWT for an average of 2·5 days because they were ready for discharge. Later studies have reported slightly longer duration of INPWT, which is likely due to the increasing use of home NPWT devices. Additional studies are necessary to identify the optimal discontinuation criteria for INPWT. Clearly, NPWT should be discontinued if the wound becomes infected, and the patient should undergo surgical treatment of their infection.
Contraindications
There are no specific contraindications for INPWT with respect to standard NPWT, except for sensitivity to silver, which is present in the interface layer for the sole purpose of helping control microbial growth in the layer. It should be avoided in case of ischemia, inadequate hemostasis or cellulitis of the incision area. INPWT should not be used to treat open or dehiscent surgical wounds or in patients with an incision that produces an excessive amount of exudate that may exceed the capacity of the Prevena™ canister (maximum capacity 45 ml).
Complications of INPWT use
Several studies have noted significant adhesive tape reactions 60, 80. In one study, 2/10 (20%) of patients experienced blistering of the skin due to adhesives, which resolved spontaneously after NPWT removal 52. No reports of pain or discomfort related to the NPWT at continuously high pressure were recorded. On the contrary, Prevena™ lowered patient anxiety and decreased the pain and discomfort of frequent dressing changes. There are no other complications of prophylactic NPWT reported in the literature; however, this will have to be confirmed with future study.
Discussion
The success reported on applying negative pressure wound vacuum on open wounds has led to the investigation of a novel approach of NPWT as a prophylactic measure placed over clean, closed surgical incisions immediately after surgery (INPWT), and recent studies evaluating the INPWT's clinical and scientific effects suggest that it might be useful as well. Closed incision management systems with negative pressure wound therapy technology (Prevena™ USA, Inc. and Pico Smith & Nephew Inc.) have been developed. One of the main aims of interest of this review was to focus on the mechanisms of the INPWT and to clarify the basis by which the INPWT confers improved surgical site outcomes and how it exerts its potential benefit on healing milieu. These data were extrapolated mainly from animal and biomedical engineering studies and the results are schematised in Table 4. A number of basic science and animal studies have determined that INPWT is associated with an increased microvascular blood flow 81, 82, 83, 84. Morykwas et al. 44 showed an increase in blood flow in full‐thickness excisional wounds in pigs at −125 mmHg, while Timmers et al. 53 confirmed increased blood flow with NPWT on closed intact skin of healthy human forearm. Horch et al. showed a significantly increased blood flow, a significantly higher oxygen saturation and post‐capillary venous filling compared with a baseline measurement before an NPWT device was added to healthy skin 85. This mechanism of action may prove beneficial for clean, closed surgical incisions. Kilpadi et al. 86 demonstrated that reduction in hematoma and seroma formation could be the result of a possible involvement of INPWT in remodelling and enhancing the macromorphological change of lymph structures and showed that the application of negative pressure to freshly created full‐thickness wounds in rabbits resumed sensitivity of the local microvasculature to vasodilators 86. Tissue distension and smooth muscle contraction that can be triggered by compression or stretch 87 may also allow fluid to reach the tissue regions more easily, where functional lymph structures are present. Lymph involvement may also explain the significant reduction in post‐surgical edema between suture throws demonstrated in a pilot study by Yaszay et al. 88 when negative pressure was applied for 3–5 days on sutured incisions over the spine in Yucatan pigs. The reason why a reduction of wound seroma occurs, is still not completely understood. Another interesting finding of the authors is the reduction of C Reactive protein between the fifth and tenth days, post‐operatively, in the INPWT group. The mean values decreased from 78·87 to 22·38 mg/l in comparison with 83·09 to 44·06 mg/l in the CG. This might be related to the reduced secretion of the wound and the better wound healing, but the reason for this finding is still unknown and needs further evaluation. Wilkes et al. 27 explored, by three independent models (two FEA models and a benchtop model), the effects of INPWT on the local biomechanical environment, in and around previously closed cutaneous incisions. They found that INWPT decreased the lateral stress concentrations in the incision by approximately 50% not only around the closed incision but also in the fat layer and also normalised the direction of the stresses to homeostatic levels and to a distribution typical of intact tissue. The reduction in magnitude and the normalisation of the distribution of the lateral tension and shear stress is the key to maintain interfacial tissue apposition and, thereby, the integrity of the incisional closure. The suboptimal contact can result in voids that lead to hematomas/seromas, which can further compromise the integrity of the overall incision site 27. The authors observed that the Prevena™ applied over a surgically closed incision increased the force required to disrupt the incision by 43–51% as compared with closure alone, suggesting that INPWT may help prevent wound dehiscence and scarring and may contribute to possible improvement in cosmetic outcome 27, 57. The advantages of INPWT were more evident when the incision was placed in the lower extremities or over joints, where the stresses are increased as a result of motion/movement or when the patient is morbidly obese 89, 90. Excessive mechanical load is known to be involved in the fibroblast to myofibroblast transition 91 and may contribute to the increased numbers of myofibroblasts and their activity in hypertrophic scars 92. Therefore, targeted therapies to decrease myofibroblast numbers in the healing tissue may potentially have an effect cosmetically and functionally. Meeker et al. 57 investigated the role of NPWT in post‐operative primary wound treatment and closure in a porcine model at 3 days. They found that the wound's tensile resistance for maximum load at failure (N/mm) in controls was 0·348 versus NPWT at 0·470 (P = 0·001); NPWT dressings were on average 176% as strong as in the controls. Energy to failure (mj/mm) in controls was 0·85 versus NPWT at 1,128 (P = 0·035). This study provided objective data that NPWT dressing applied to surgically closed wounds enhances the healing characteristics when compared with ordinary gauze dressings, especially when wounds are closed under tension, involve extensive soft tissue trauma, drain excessively or may be at risk of subdermal hematoma formation.
Human studies have been investigated in order to evaluate the impact of INPWT on the incidence of post‐operative complications (infection, dehiscence, seroma, hematoma, skin and fat necrosis, skin and fascial dehiscence or blistering) and on other variables (re‐operation and re‐hospitalization rates, time to dry wound, cost saving) which were regarded as objective evaluation parameters, reliable and reproducible (see Table 5c).
Infection of the surgical incision was the commonly reported complication (13 of the 15 human studies). Despite advances in aseptic technique and infection control practices, SSIs continue to be a major source of patient mortality and morbidity compared with uninfected patients and represent a substantial burden to health care costs (mean increase of 115%) 93 because patients who develop a SSI have longer and more expensive hospitalisations (mean increase of 176%) 93, have to undergo additional diagnostic tests and antibiotic therapies, incur home health expenses, require more re‐admissions, spend more time in the intensive care unit and occasionally need invasive procedures and/or re‐operation 94. SSIs are the third most common hospital‐acquired infections 95, 96 and account for 38% of nosocomial infections in surgical patients 97 with a global cost of $1·6 billion in hospital care costs per year in the United States 98. Three of the 7 retrospective studies 6, 73, 74 and 2 of the 2 observational studies 67, 68 documented a 0% incidence of infection in their study population when using INPWT even if none of these studies had CGs for comparison. Stannard et al., 43 Reddix et al., 75 Blackham et al., 71 Masden et al., 64 Grauhan et al., 63 Gomoll et al. 2 all reported a lower incidence of SSIs with the use of INPWT, when compared with standard dry dressing. In contrast with the previous results, Condé‐Green et al. 70 demonstrated no significant difference in the rate of infection between the INPWT and the conventional dressing of dry gauzes and Howell et al. found a higher percentage of infections in the INPWT group 66.
Seroma development was the second most commonly reported complication (8 of the 15 human studies). The RCT of Pachowsky et al., 65 Stannard et al., 3 Vargo 73, Tauber et al., 72 Conde‐Green et al. 70 found a significant reduction in the incidence of post‐operative seromas by applying prophylactic INPWT. Condé‐Green et al. 70 and Blackham et al. 71 were the sole authors to report the incidence of hematoma and they found a lower incidence in the INPWT group when compared with conventional dressing. In contrast with the previous studies, Blackham reported an increased number of cases of seroma in the INPWT group (P = 0·867) than in the CG but among high‐risk patients, the INPWT group showed a lower number of patients with seroma.
In six of these studies, there was zero incidence of re‐operation with the application of INPWT 6, 53, 65, 66, 67, 68. Condé‐Green et al., 70 Tauber et al. 72 and Grauhan et al. 63 experienced an increased number of patients who underwent re‐operation among the conventional dressing group compared with the INPWT group.
Among studies reviewed, the rate of dehiscence ranged from 8·6% to 36·4% in the INPWT groups versus 16·5% to 39% in the CGs. Only two studies 33, 70, 71 demonstrated a significantly lower dehiscence rate with INPWT compared with standard dry dressing and in an RCT, Masden et al. 64 demonstrated a higher incidence of skin dehiscence in the INPWT group even if the results did not reach a level of statistical significance. Further investigation is necessary before a definitive assessment about dehiscence can be made.
Because of limited studies, it is difficult to justify any strong assertion and recommendation regarding the effect of INPWT on the rate of skin necrosis and blistering and of time until attainment of dry wound.
In regard to the anatomic area and type of surgery, the majority of the studies in this review has evaluated the use of INPWT in orthopaedics 2, 99, 100, 101, which, incidentally, has a higher level of evidence (5 RCT). The first prospective, randomised, controlled study was published in 2011 and included 19 consecutive patients with the application of this new INPWT over closed incisions following total hip arthroplasty 65. Results showed a significant decrease in the development and volume of post‐operative seromas and lesser consumption of antibiotics (8·44 ± 2·24 versus 11·8 ± 2·82 days, P = 0·005) in the INPWT group. In a first case series of four patients with high‐risk wounds of developing post‐operative wound complications, epidermal vacuum therapy was safely and successfully applied on clean, closed surgical wounds 43. In a level 1 randomised prospective multi‐centre clinical trial of 263 patients comparing INPWT with standard post‐operative dressing used over high‐risk closed incisions following high‐energy trauma treated with open reduction and internal fixation (ORIF) of tibial plateau, pilon and calcaneus fractures, Stannard et al. 3, 33 recommended that NPWT should be considered for high‐risk wound following severe skeletal trauma. Reddix et al. 74 published on NPWT use for surgical incisions in 235 morbidly obese patients (BMI ≥ 40) who underwent ORIF of acetabular fractures. The reported rate of wound infections (1·3%) compared very favourably with the published infection rate of 4% and was significantly less than the authors' previously reported infection rate of 6·2% following surgical fixation of acetabular fractures 75.
In cardiac surgery, NPWT effects were explored by a retrospective review of Atkins et al. 6, which recommended its use for patients with an increased risk for sternal wound infections. However, this was not a randomised trial and there was no CG for comparison. Other recent small case series and studies had also shown successful use of this new INPWT in helping to reduce infection and other post‐operative complications of clean, closed surgical incisions. In 2011, Colli conducted the first prospective cohort study in cardiac surgery patients in Europe on this new class II device using Prevena™ Incision Management System on sternal closed surgical incisions in ten patients with a mean Fowler risk score of 15·1 (range 8–30) (average risk of infection of 6·4% (range 2·3–16·2%) 11. Wounds and surrounding skin showed complete wound healing at 30 days after surgery with the absence of skin lesions due to the negative pressure after removal of the Prevena™ dressing. No device‐related complications were observed. No wound complications such as infection occurred in this high‐risk group of patients until at least 30 days after surgery 43, 67, 102. However, the small number of patients is a limitation of the present evaluation process and the Prevena™ system could not be considered to be the only factor that could explain the observed favourable results.
Finally, the prophylactic NPWT may also be effective when used for abdominal incisions. Estimates of surgical site complication rates after open abdominal surgery range from 5% to 40%, and may approach 60% in the morbidly obese with an estimated cost of $180–500 million per year 103, 104, 105, 106. In their retrospective chart review, Condé‐Green et al. 70 analysed the outcomes in 56 patients treated post‐operatively with INPWT (group I) versus conventional dry gauze dressings (group II) following primary closure of abdominal wall for large ventral hernias. They found a statistically significant reduction in the rates of overall wound complications (22% versus 63·6 %) (P = 0·020) and in the rates of skin dehiscence (6·3 times less). Post‐bariatric plastic surgery in patients admitted for massive weight loss represents a high‐risk surgery. Especially, after abdominal dermolipectomy for bodycontouring, post‐operative complication rates, including seroma, bleeding and wound dehiscence, are described as being constantly high compared with other surgical interventions 107. The overall amount of complications after post‐bariatric abdominal dermolipectomy is about 37·4% 108 In a retrospective study of 23 obese subjects with an average body mass index of 32·8 kg/m2 who underwent post‐bariatric abdominal dermolipectomy, a high‐risk procedure for surgical site complications according to the literature 107, NPWT preset at −125 mmHg for 5 days significantly reduced post‐operative secretion volumes (100 ml versus 151 ml, P < 0·001) and decreased the average time to drain removal (10·8 days versus 5·1 days P < 0·001) when compared with standard dressings (Steri‐Strips and dry gauze) of the CG 80. The results of Dragu et al. 80 indicated that wide abdominal topical non‐circumferential negative pressure application on the ventral and lateral trunk following post‐bariatric abdominal dermolipectomy led to a significant reduction in exudate formation and enabled early drain removal decreasing length of hospitalisation, which in turn led to a reduction of costs. In addition, Dragu et al. 109 studied the spatial and temporal intraoperative micro‐perfusion patterns of the abdominal wall and abdominal wall oxygen consumption before and after 17 post‐bariatric abdominal dermolipectomies after massive weight loss. The results of this study showed that the infra‐umbilical region, the part of the abdominal fat typically resected during dermolipectomy had the lowest oxygen saturation before surgery, probably because it was compromised by previous obesity, which resulted in lax skin after massive weight loss. Further, the results corroborated the clinical impression that wound healing is mostly altered in the medial part of the mobilised abdominal skin flap, supporting the clinical practice wherein suture tension is placed more on the lateral parts of the wound edges: previously well‐oxygenated parts in the median line of a cranial wound margin underwent a significant decrease in oxygen saturation upon mobilisation and subsequent suturing, probably due to post‐operative tension, being predisposed for wound healing complications. On the contrary, the caudal wound edges showed an intra‐operative increase of micro‐perfusion parameters, especially in the mons pubis area. Moreover, this study highlighted the fact that the perfusion is impaired not only by dissecting nutritive vessels but also by post‐operative tension on the abdominal wall 109.
Vargo 73 conducted a retrospective review of prospectively collected data in 30 patients with high‐risk wounds treated with NPWT after complex abdominal reconstruction. The study concluded that NPWT applied to a closed, high‐risk surgical wound is safe (no NPWT skin‐related complications were detected), with no evidence of skin necrosis and a statistically significant decreased wound infection rate (P < 0·05) 73.
Blackham et al. 71, in their retrospective analysis of 191 operations for colorectal, pancreatic, or peritoneal surface malignancies, demonstrated the efficacy of INPWT in preventing SSIs, dehiscence and overall complications in high‐risk surgical oncology patients. In particular, clean‐contaminated operations appeared to benefit the most from INPWT. Tauber et al. 72 evaluated, in a retrospective approach, epidermal vacuum therapy (n = 8) versus conventional wound care (n = 16) for the prevention of wound complications following 24 inguinal lymph node dissections for penile cancer or cancer of the urethra. The study suggests that use of INPWT may decrease the rate of drained fluid, duration of drainage, formation of lymphoceles and persistent lymphorrhoea or lymphoedema of the lower extremity, and may reduce the re‐interventions rate (7% versus 23%)(P = 0·631) and the days of hospitalisation (9 days versus 10 days). Despite the low number of patients included, this difference was statistically significant (P =0·049) 72. However, other prospective studies had not demonstrated a significant difference in wound healing with the use of NPWT 110. A prospective study of 119 patients who underwent repair of ventral hernias found that subjects using NPWT experienced a 20% lower SSI rate than the controls, but this reduction was not statistically significant 111. A meta‐analysis of five trials with a total of 280 participants concluded that there was no evidence of the effectiveness of prophylactic NPWT when used on incisions that were expected to heal by primary intention; however, the accumulation of data was judged to be limited 60.
There is no valuable discussion regarding the cost of INPWT in the literature. Stannard et al. 3 estimated that the application of INPWT costs less than $500 for the mean 2·5 days of therapy per study patient. They concluded that INPWT is a cost‐effective intervention as cost savings from a shortened hospital stay and prevention of post‐operative SSI offsets the initial intervention cost. The Mullins and Paulos 112 theoretical health economic model generated on the Stannard data 3 calculated a potential cost savings of $5338 and $1586 per prevention of infection and dehiscence, respectively. Using data from a historical cohort and mathematical modelling, Lewis et al. 69 determined that the necessary reduction in risk of wound complications (at least 33%) would render the use of prophylactic negative pressure wound vacuum therapy (INPWT) cost saving compared with routine incision care following closed laparotomy incisions for endometrial cancer. Both potential cost savings and clinical benefit seem to be amplified in obese and morbidly obese patients who have higher baseline rates of wound complication. Considering that approximately 500 000 abdominal hysterectomies are performed annually in the United States, prophylactic NPWT could result in substantial cumulative cost savings 113.
Eighty percent of the human studies 3, 6, 33, 63, 64, 66, 67, 68, 69, 71, 73, 74 reviewed show a decrease in wound infection and 47% of the study 33, 64, 68, 69 71, 72, 75 examined show a decrease in wound dehiscence with use of INPWT, which suggests potential cost savings. A cost analysis was also discussed in the recent review by Horch 114; however, to date, there have been no comprehensive economic analyses of INPWT use.
Conclusion
Prevention of surgical wounds complications as part of efficient and cost‐effective health care is an active area of research: high morbidity, additional costs due to prolonged length of hospital stay and re‐admissions, return to operating room, additional medical and surgical procedures, home health services and a decreasing inpatient quality of life are all associated with complex healing wounds 115, 116, 117, 118, 119. Thus, preventive therapy may have a critical role in healing management. Negative‐pressure wound vacuum therapy (NPWT), an established treatment for open surgical incisions following infection or breakdown, has recently been the focus of new investigation in its use as a prophylactic measure to prevent complication via application to closed incisions immediately after surgery.
A carefully conducted and documented literature search was performed with the goal to developmethods that would be transparent, reproducible and with minimum bias. Nevertheless, only one reviewer performed the search and data extraction, and we cannot exclude the possibility that there may be trials outside of our search strategy that have not been included. Besides, we included only those articles in the English language, thereby creating a potential language bias. This review highlights several areas where future research is needed. Additional studies, especially prospective and randomized controlled clinical trials, are needed to further confirm the cost‐effectiveness and long‐term implications of this therapy on post‐operative wound healing complications. A comprehensive economic analyses of INPWT use is really needed. Given the ubiquitous shortage of money in today's health‐care systems, cost‐effective means of reducing surgical site complications rates are important and should be carefully considered for a larger clinical application. In addition, it would be important to look at a standard to compare results or compare different types of INPWT devices available and if complication results vary. Being aware of the rising popularity of this novel application of the traditional NPWT, the medical supply industry has responded to this emerging market by introducing different novel types of machines that are available. While the marketing of these products continues, a standardisation of their effectiveness is becoming increasingly important.
In conclusion, the preliminary results included in our review are encouraging, as it outlines INPWT as safe and potentially beneficial, especially for patients with a higher baseline rate of wound complications; however, data actually emerging in literature are insufficient at this moment to recommend widespread use of this technology.
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