Negative pressure wound therapy (NPWT) probably results in fewer surgical site infections (SSIs) than standard dressings in people with closed wounds after surgery.
NPWT probably makes no difference to the proportion of people with wound reopening (dehiscence) after surgery and may make little or no difference to the number of people who die.
NPWT may increase the number of people with skin blistering after surgery but may make little or no difference to other outcomes.
The cost-effectiveness of NPWT and how certain we are about this depends on the type of surgery.
What are surgical wounds healing by primary closure?
Surgical wounds healing by primary closure are incisions created by surgery where the edges have been brought together, usually by using stitches or staples. Most surgical wounds heal in this way. A potential complication of surgery is SSI, an infection at the site of a surgical wound. The proportion of people who develop an SSI after surgery can be as high as 40%. An SSI can cause pain and discomfort, as well as increasing a person’s length of hospital stay and cost of treatment.
What did we want to find out?
NPWT is a sealed wound dressing attached to a vacuum pump which sucks fluid away from the wound. This may assist with wound healing and reduce risk of infection. We wanted to find out whether NPWT was better compared with standard wound dressings (usually gauze and tape) for treating people who had had surgery and had wounds which had been closed. We were interested in complications including SSI; wound reopening (dehiscence) and death for any reason. We also looked at several other outcomes including the need for another operation, the need to be admitted to hospital again, pain, quality of life, as well as some specific types of complications (haematoma (an accumulation of blood under the skin), seroma (an accumulation of clear fluid under the skin), skin blisters).
We also wanted to find out whether NPWT was cost-effective for treating people who had closed surgical wounds.
What did we do?
We searched for randomised controlled trials (clinical studies where the treatment people receive is chosen at random). This type of study design provides the most reliable evidence about the effects of a treatment. We searched for studies that compared any type of NPWT with standard dressings in people who had had surgery and had a wound which had been closed. We compared and summarised their results, and rated our confidence in the evidence.
What did we find?
We found 62 studies which compared NPWT with standard dressings and looked at surgical site complications. A variety of NPWT systems was used. A total of 13,340 people have been included in this review. A wide variety of surgeries was included such as knee and hip operations, caesarean sections, operations for broken bones and abdominal surgeries. There were more women than men included in the review because several large trials included only women having caesarean sections. Most of the people included in the review live in North America, Europe or Australasia.
Eleven studies (6384 people) reported on risk of death and found that there may be a lower risk with NPWT compared with standard dressings but this is not clear. Forty-four studies (11,403 people) looking at SSI were combined, and found that NPWT probably reduced the risk of SSI compared with standard dressings. Twenty-three studies (8724 people) found that there is probably little or no difference in wound reopening between NPWT and standard dressings. For most other outcomes, the evidence showed that there may not be clear differences between the treatments, or that we are uncertain about the true effect of the treatments. The exception was skin blistering where NPWT may increase the proportion of people who experience this after surgery.
Six cost-effectiveness studies were included in the review. These studies looked at women who had had caesarean sections, people with lower limb fractures, knee and hip surgeries, vascular surgery and heart surgery. All these studies used clinical information from trials included in this review. NPWT is probably cost-effective for caesarean section wounds in obese women and probably not cost-effective for fracture surgery wounds but we are less sure about its cost-effectiveness in the other types of surgery.
What limited our confidence in the evidence?
Our confidence in the evidence was limited by different reasons for different outcomes. Given the small number of people who died, the results for death are likely to change with more evidence. For SSI, approximately half the people were in studies using methods likely to introduce errors. For wound reopening and most other outcomes, our confidence was reduced by a combination of these reasons. For skin blistering, our confidence was reduced by differences between the studies as well as study methods.
How up to date is this review?
This review is up to date to January 2021.
People with primary closure of their surgical wound and treated prophylactically with NPWT following surgery probably experience fewer SSIs than people treated with standard dressings but there is probably no difference in wound dehiscence (moderate-certainty evidence). There may be a reduced risk of death after surgery for people treated with NPWT compared with standard dressings but there is uncertainty around this as confidence intervals include risk of benefit and harm (low-certainty evidence). People treated with NPWT may experience more instances of skin blistering compared with standard dressing treatment (low-certainty evidence). There are no clear differences in other secondary outcomes where most evidence is low or very low-certainty. Assessments of cost-effectiveness of NPWT produced differing results in different indications. There is a large number of ongoing studies, the results of which may change the findings of this review. Decisions about use of NPWT should take into account surgical indication and setting and consider evidence for all outcomes.
Indications for the use of negative pressure wound therapy (NPWT) are broad and include prophylaxis for surgical site infections (SSIs). Existing evidence for the effectiveness of NPWT on postoperative wounds healing by primary closure remains uncertain.
To assess the effects of NPWT for preventing SSI in wounds healing through primary closure, and to assess the cost-effectiveness of NPWT in wounds healing through primary closure.
In January 2021, we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In-Process & Other Non-Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries and references of included studies, systematic reviews and health technology reports. There were no restrictions on language, publication date or study setting.
We included trials if they allocated participants to treatment randomly and compared NPWT with any other type of wound dressing, or compared one type of NPWT with another.
At least two review authors independently assessed trials using predetermined inclusion criteria. We carried out data extraction, assessment using the Cochrane risk of bias tool, and quality assessment according to Grading of Recommendations, Assessment, Development and Evaluations methodology. Our primary outcomes were SSI, mortality, and wound dehiscence.
In this fourth update, we added 18 new randomised controlled trials (RCTs) and one new economic study, resulting in a total of 62 RCTs (13,340 included participants) and six economic studies. Studies evaluated NPWT in a wide range of surgeries, including orthopaedic, obstetric, vascular and general procedures. All studies compared NPWT with standard dressings. Most studies had unclear or high risk of bias for at least one key domain.
Eleven studies (6384 participants) which reported mortality were pooled. There is low-certainty evidence showing there may be a reduced risk of death after surgery for people treated with NPWT (0.84%) compared with standard dressings (1.17%) but there is uncertainty around this as confidence intervals include risk of benefits and harm; risk ratio (RR) 0.78 (95% CI 0.47 to 1.30; I2 = 0%). Fifty-four studies reported SSI; 44 studies (11,403 participants) were pooled. There is moderate-certainty evidence that NPWT probably results in fewer SSIs (8.7% of participants) than treatment with standard dressings (11.75%) after surgery; RR 0.73 (95% CI 0.63 to 0.85; I2 = 29%). Thirty studies reported wound dehiscence; 23 studies (8724 participants) were pooled. There is moderate-certainty evidence that there is probably little or no difference in dehiscence between people treated with NPWT (6.62%) and those treated with standard dressing (6.97%), although there is imprecision around the estimate that includes risk of benefit and harms; RR 0.97 (95% CI 0.82 to 1.16; I2 = 4%). Evidence was downgraded for imprecision, risk of bias, or a combination of these.
There is low-certainty evidence for the outcomes of reoperation and seroma; in each case, confidence intervals included both benefit and harm. There may be a reduced risk of reoperation favouring the standard dressing arm, but this was imprecise: RR 1.13 (95% CI 0.91 to 1.41; I2 = 2%; 18 trials; 6272 participants). There may be a reduced risk of seroma for people treated with NPWT but this is imprecise: the RR was 0.82 (95% CI 0.65 to 1.05; I2 = 0%; 15 trials; 5436 participants). For skin blisters, there is low-certainty evidence that people treated with NPWT may be more likely to develop skin blisters compared with those treated with standard dressing (RR 3.55; 95% CI 1.43 to 8.77; I2 = 74%; 11 trials; 5015 participants). The effect of NPWT on haematoma is uncertain (RR 0.79; 95 % CI 0.48 to 1.30; I2 = 0%; 17 trials; 5909 participants; very low-certainty evidence). There is low-certainty evidence of little to no difference in reported pain between groups. Pain was measured in different ways and most studies could not be pooled; this GRADE assessment is based on all fourteen trials reporting pain; the pooled RR for the proportion of participants who experienced pain was 1.52 (95% CI 0.20, 11.31; I2 = 34%; two studies; 632 participants).
Six economic studies, based wholly or partially on trials in our review, assessed the cost-effectiveness of NPWT compared with standard care. They considered NPWT in five indications: caesarean sections in obese women; surgery for lower limb fracture; knee/hip arthroplasty; coronary artery bypass grafts; and vascular surgery with inguinal incisions. They calculated quality-adjusted life-years or an equivalent, and produced estimates of the treatments' relative cost-effectiveness. The reporting quality was good but the evidence certainty varied from moderate to very low. There is moderate-certainty evidence that NPWT in surgery for lower limb fracture was not cost-effective at any threshold of willingness-to-pay and that NPWT is probably cost-effective in obese women undergoing caesarean section. Other studies found low or very low-certainty evidence indicating that NPWT may be cost-effective for the indications assessed.