Cochrane in CORR®: Negative Pressure Wound Therapy for Surgical Wounds Healing by Primary Closure

Importance of the Topic Despite ongoing advances in medicine, postoperative complications continue to burden patients and the healthcare system. The incidence rate of surgical site infections (SSIs), in particular, remain similar to those seen in 2018, when we first wrote about SSIs in this space [9], and is a leading cause of morbidity and mortality. As such, it is evident that management of such complications remains challenging. With improving infection control protocols (such as prophylactic antibiotics) [15], SSI rates can be expected to remain stable or decrease. However, with the rise in antibiotic-resistant pathogens, these infection control protocols may be insufficient. Should SSI rates remain at today’s level, or even begin to rise, more aggressive intervention is needed. Traditionally in orthopaedic surgery, postoperative wound care consists of placing a nonadherent or silver-impregnated material on the surgical site, followed by gauze and abdominal pads [14]. More recently, negative pressure wound therapy (NPWT) has entered the picture. Previously, NPWT has been used to manage complex and nonhealing wounds, such as those accompanying open fractures, by creating a closed, negative-pressure system using vacuum suction at the wound surface that is meant to promote healing [7, 13, 18]. Having been found to be effective in expediting wound healing by secondary intention through improved local blood flow and wound contraction [13], there remains a question regarding its utility in prophylactic management of wound healing by primary intention, where skin edges are approximated and secured. While such wounds tend to heal faster [20], this can be complicated by patient factors (obesity, chronic obstructive pulmonary disease) [11, 12] and technical factors (sutures breaking, cutting through tissue) [1]. Therefore, there is a question of whether challenging wounds healing by primary intention may be augmented by NPWT. Still, a 2018 Cochrane review found no substantial difference in the rates of wound complications between commercial NPWT and standard postoperative dressings [9]. The current updated Cochrane review, the fourth one on this topic, included 18 new randomized clinical trials and one economic study to further evaluate the impact of NPWT on surgical wound healing, which provide new findings to guide decision-making [16]. In the most recent update, NPWT was compared to standard dressings (gauze, tape) across a total of 62 studies (13,340 patients). With moderate certainty, the authors found a lower risk of SSI based on 44 trials totaling 11,403 patients (risk ratio [RR] = 0.78 [95% CI 0.63 to 0.85]), and, with low certainty (due to high risk of bias and inconsistency), they found a higher risk of skin blister formation based on 11 trials totaling 5015 patients (RR = 3.55 [95% CI 1.43 to 8.77]) when using NPWT compared with standard dressings. There were no notable differences in mortality, wound dehiscence, hematoma formation, wound-related readmission, or pain levels when comparing NPWT to standard dressings. Based on small or no-difference findings in subgroup analyses, NPWT has a low likelihood of being cost-effective compared to standard dressings. Upon Closer Inspection At first glance, the pooled results reveal that with moderate certainty, there is a reduction in the risk of SSI (95% CI 0.65 to 0.85) with NPWT. But further subgroup analyses found that the effectiveness of NPWT may be limited to preventing superficial SSI (95% CI 0.52 to 0.92), while it did not reliably prevent deep SSI (95% CI 0.76 to 1.18), as the CI overlapped 1.0. Deep SSIs typically result in surgical debridement, while superficial SSIs are usually managed medically and typically resolve without sequelae [8, 14]. Considering the difference in overall impact between the two types of SSI, it is important to differentiate between them when considering the overall utility of NPWT as cost-effectiveness may be affected by SSI severity. Additionally, when considering subgroups by type of surgery alone, orthopaedic procedures did not demonstrate a considerable reduction in SSI when using NPWT following hip/knee arthroplasties (95% CI 0.32 to 1.49) or lower limb fracture surgery (95% CI 0.61 to 2.20). The Cochrane reviewers rated down the quality of evidence for imprecision, high risk of bias in various domains, and inconsistency across domains, with approximately half of the studies using methods likely to introduce error. Additionally, a number of studies were terminated prematurely due to skin blistering [8, 19] and futility (low chance of a positive result, although not a negative result) [10, 17, 19]. These studies were included for analysis and may skew the overall findings. Although an intention-to-treat analysis may mitigate some of this error, it is important to recognize that termination due to skin blistering may suggest poor utility of NPWT in the real world. Three studies were terminated due to poor enrollment and no apparent treatment effect [4], the principal investigator leaving the institution [3], and the sponsor pulling funding [5], though these studies were not further analyzed. Therefore, the certainty in results was downgraded for imprecision, risk of bias, or a combination of these, and we believe they are being appropriately cautious. Take-home Messages Previously, NPWT was not found to considerably impact wound complication rates when compared to standard dressings [9]. This updated review suggests that NPWT for surgical wound healing by primary intention reduces SSI incidence overall, but the effect may be limited to superficial SSIs alone, and there is no specific benefit in prevention for orthopaedic procedures such as hip or knee arthroplasties or lower limb fracture surgery. Furthermore, NPWT may increase the incidence of skin blistering but has little or no effect on mortality, reoperation, readmission, and seroma formation with uncertain effects on pain and hematoma formation. Estimates of cost-effectiveness are difficult to generalize across specialties. While some effectiveness is seen in particular surgical indications, given that NPWT is not effective in reducing SSI following fracture surgery and knee arthroplasty, the cost-effectiveness of NPWT in these cases cannot be accurately determined. The trials were concentrated in only a few surgical indications, making it difficult to draw generalizable conclusions regarding NPWT usage following surgical procedures. Further research should take care to include the classification of SSI severity using recognized scales (Szilagyi classification) to better examine the role and differential effects of NPWT in SSI reduction. There continues to be a need for well-conducted randomized controlled trials that examine cost-effectiveness and utility of NPWT across more surgical indications to determine whether small clinical differences have any impact on overall care costs related to avoiding complications. Given that this Cochrane review found no benefit for NPWT in hip/knee arthroplasties and lower limb fracture surgeries, we recommend against its use in those contexts outside of well-designed trials meant to fill the remaining gaps in our knowledge. There continues to exist a need for high-quality studies across other orthopaedic procedures to examine the role and utility of NPWT in the orthopaedic population [2, 6].

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