Abstract
Objective:
To estimate the effectiveness of prophylactic negative pressure wound therapy in patients undergoing laparotomy for gynecologic surgery.
Methods:
Randomized controlled trial. Eligible, consenting patients of regardless of BMI undergoing laparotomy for presumed gynecologic malignancy were randomly allocated to standard gauze or negative pressure wound therapy. Patients with a BMI ≥40 kg/m2 and benign disease were also eligible. Randomization, stratified by BMI, occurred after skin closure. The primary outcome was wound complication within 30(+/−5) days of surgery. A sample size of 343 per group (N=686) was planned.
Results:
From 3/1/2016-8/20/2019, we identified 663 potential patients; 289 were randomized to negative pressure wound therapy (254 evaluable cases) and 294 to standard gauze (251 evaluable cases), for a total of 505 evaluable patients. Median age of the entire cohort was 61 years (range, 20-87). Four hundred ninety-five patients (98%) underwent laparotomy for malignancy. The trial was eventually stopped for futility after an interim analysis of 444 patients. The rate of wound complications was 17.3% the NPWT group and 16.3% in the gauze group, absolute risk difference 1% (90% CI: −4.5-6.5%; P=0.77). Adjusted odds ratio (OR) controlling for estimated blood loss and diabetes was 0.99 (90% CI: 0.62-1.60). Skin blistering occurred in 33 patients (13%) in the negative pressure wound therapy group and 3 (1.2%) in the gauze group(P<0.001).
Conclusions:
Negative pressure wound therapy after laparotomy for gynecologic surgery did not lower the wound complication rate but did increase skin blistering.
Precis
Negative pressure wound therapy did not lower the wound complication rate in patients undergoing laparotomy for gynecologic surgery.
Introduction
Surgical site infections (SSIs), which lead to increased postoperative symptom burden, recovery time, hospital stay, readmissions and mortality, are one of the most common and costly types of hospital-acquired infections.1,2 According to a study by the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP), the most common reason for unplanned readmission after surgery among 498,895 operations was SSI.3
Superficial SSIs involve only the skin and subcutaneous tissue; deep SSIs involve the fascial and muscle layers; and organ–space SSIs involve anything deeper.4 The overall SSI rate after laparotomy for gynecologic malignancies ranges from 1-37%.5–10 This high variation is due to the retrospective nature of published results, heterogeneity in the complexity of cases, and the use of SSI reduction bundles. The rates of only superficial SSIs are difficult to extrapolate from these publications due to the heterogeneity of SSI definitions, as well as patient and procedure variability. In obese and morbidly obese women, the rate of wound complications (i.e., superficial SSIs) after laparotomy for benign or malignant indications is 27-33%.11,12
Negative pressure wound therapy is a non-invasive, superficially placed therapy that exerts a mechanical vacuum force on tissue, which theoretically leads to accelerated healing.13 Negative pressure wound therapy, commonly used to manage acute and chronic wounds, despite limited data,14 are now also FDA approved as a preventative intervention for closed surgical incisions.15 A meta-analysis of randomized and non-randomized trials suggested a reduction in SSI rates but not seroma or wound dehiscence for closed laparotomy incisions with the use of negative pressure wound therapy.16 A recent Cochrane report of only randomized trials among various surgical incisions and procedures, however, failed to demonstrate a reduction in SSIs or other wound complications.17
The primary objective of our study was to evaluate whether prophylactic negative pressure wound therapy for laparotomy closure reduces the incidence of postoperative wound complications in patients who have undergone gynecologic surgery .
Methods
This investigator-initiated, open-label randomized controlled trial was approved by the Institutional Review Board of Memorial Sloan Kettering Cancer Center (MSK) and was conducted at 4 centers within the MSK Cancer Alliance (NCT02682316).
Eligible patients included women aged ≥18 years irrespective of body mass index (BMI) who were planning to undergo laparotomy for either a confirmed or presumed gynecologic malignancy. Women with a BMI ≥40 kg/m2 undergoing laparotomy for a benign indication were also eligible. Exclusion criteria included those with laparotomy incisions left open for any reason or laparotomy incisions unable to be closed primarily due to tissue or fascial damage. Eligible women were randomized intraoperatively after the skin had been completely closed to either standard gauze or an FDA-approved negative pressure wound therapy system used for the healing of clean or clean-contaminated, closed surgical incisions (Prevena™ Customizable Incision Management System; KCI/Acelity; San Antonio, TX). The system consists of a self-adhesive foam dressing with a configuration that allows the clinician to alter the dressing to cover closed surgical incisions of different sizes and shapes. It is connected to a V.A.C. ULTA™ Therapy Unit (KCI/Acelity) to maintain a constant pressure of negative 125 mm Hg. The randomization sequence was computer generated by the Department of Epidemiology and Biostatistics at MSK using randomly permuted blocks stratified by BMI >40kg/m2 regardless of whether planned surgery was for malignancy or benign disease. Sequentially numbered, sealed, opaque, non-resealable envelopes containing the randomization assignment were used and opened intraoperatively by the surgical team only after skin closure.
Per institutional protocol all women received prophylactic antibiotics within 60 minutes of skin incision. Of note, all 4 participating sites had adopted SSI reduction bundles and Enhanced Recovery after Surgery (ERAS) protocols prior to the initiation, and independent, of this study. Specific skin preparations were left to institutional standards and were not protocol mandated. Skin layer closures was with surgical staples. Intraperitoneal, subcutaneous drains (or both) were allowed at the surgeon’s discretion.
Women randomized to the control group had the gauze removed on postoperative day (POD) 2. The negative pressure wound therapy system was removed at the time of discharge or POD 7, whichever came first.
The primary outcome of the study was the development of a wound complication within 30 (+/−5) days of surgery, which was a composite endpoint inclusive of any of the following alone or in combination: wound infection, wound separation, wound seroma, or wound hematoma. Secondary outcomes consisted of the individual types of wound complications. The tertiary outcome was the development of skin blistering and/or contact dermatitis and wound pain. Wound pain was determined using standard visual analog scale (VAS). Evaluations for wound complications were performed using a provider-completed assessment and data form.
Based on institutional data showing a wound complication (as defined above) rate of 7.6%, we chose a baseline wound complication rate of 10% to account for an error rate in the institutional database as well as differing rates among the 4 sites. With a baseline rate of 10%, we chose a 50% decrease in the rate of wound complication as clinically significant. To achieve 80% power with a type I error of 10% (2-sided test), it was determined we would need to enroll 686 evaluable patients (343 per group).
The primary analysis of our study was performed via a two-sample test for binomial proportions to compare the difference in wound complication proportions between the two groups. Univariate and multivariate logistic regression were performed to test for differences in wound complications between groups after controlling for other variables. The distributions of patient demographic and clinical factors between the two groups were tested by applying Fisher’s exact test for categorical and Wilcoxon Rank-Sum test for continuous variables. The secondary analysis of each separate type of wound complication, namely wound infection, separation, and formation of hematoma or seroma, was performed in separate logistic regression models in which the outcome was the presence or absence of the wound complication and the covariate of interest was the treatment group (control or experimental). This secondary analysis was hypothesis-generating, and p values were not adjusted for multiplicity. Fisher’s exact test was used to analyze the tertiary objective of the incidence of skin blistering and contact dermatitis between groups. Complications were assessed and graded as per published MSK Secondary Surgical Events (SSE) system.18 In brief, the MSK SSE system grading is as follows: grade 1 requires only bedside care or oral medications; grade 2 requires intravenous medications or transfusion; grade 3 requires radiologic, endoscopic, or operative interventions; grade 4 leads to chronic disability or organ resection; and grade 5 is death.18 Blinding was not possible due to nature of interventions. However, the principal investigator (MMLJr) was blinded as to the composite results of primary outcome of wound complications throughout trial conduct.
The study was terminated early after an interim analysis demonstrated low probability of showing a difference between the two groups at the end of the study. For the interim analysis (n=444 of 684 planned patients for enrollment), the Z-test statistic was 0.328 (with P=0.797 by adjusting for second look). A post-hoc design with two planned interim analyses provided a first-look futility boundary of +/−0.29 and a second-look futility boundary of +/−0.61. The z of 0.328 fell within the second-look futility boundaries. Also, the conditional power,19 which calculates the probability that the final results at n=684 would be statistically significant given the data observed at n=444, was 3.9%. A complete description of study methods, including statistical design, can be found in the protocol (Appendix I).
Results
Of 663 screened patients, 289 were randomized to negative pressure wound therapy (254 evaluable cases) and 294 to standard gauze (251 evaluable cases), for a total of 505 evaluable patients (Figure 1). Reoperations within 30 days of surgery were all performed to manage a postoperative complication unrelated to the laparotomy wound. Baseline patient demographics, as well as clinical and perioperative factors, were generally well balanced (Table 1).
Figure 1.
CONSORT (Consolidated Standards of Reporting Trials) protocol flow diagram.
Table 1.
Baseline Characteristics of the 505 Evaluable Cases
| Characteristic | NPWT (n=254) | Standard Gauze (n=251) |
|---|---|---|
| Age, years | 60 (20-85) | 61 (23-87) |
| BMI, kg/m2 | 26 (18-60) | 26 (17-56) |
| Medical Comorbidities | ||
| Hypertension | 85 (34) | 86 (35) |
| Diabetes | 36 (14) | 0 (8) |
| Vascular disease | 7 (2.8) | 12 (5) |
| Pulmonary disease | 22 (9) | 23 (9) |
| Liver disease | 4 (1.6) | 2 (0.8) |
| Kidney disease | 1 (0.5) | 1 (0.5) |
| Smoking status | ||
| Never | 143 (57) | 152 (61) |
| Current | 10 (4) | 11 (4) |
| Former | 97 (39) | 87 (35) |
| No data | 4 | 1 |
| Prior abdominal surgery | 175 (70) | 168 (68) |
| Current alcohol use (any) | 116 (47) | 124 (50) |
| Prior radiation therapy exposure | 7 (2.8) | 8 (3.2) |
| Prior chemotherapy exposure | 85 (34) | 79 (32) |
| Indication for current laparotomy | ||
| Ovary/fallopian tube/peritoneal cancer | 203 (80) | 207 (82) |
| Uterine cancer | 37 (15) | 32 (13) |
| Cervical cancer | 4 (1.6) | 2 (0.8) |
| Other | 5 (2) | 5 (2) |
| Benign | 5 (2) | 5 (2) |
| Preoperative hemoglobin, g/dL | 12 (7.6-15) | 12 (7.5-16.4) |
| Preoperative serum albumin, g/dL | 4.1 (0.9-4.9) | 4.1 (1.6-5.3) |
| Presence of ascites | 49 (20) | 40 (16) |
| Bowel resection at current laparotomy | 92 (37) | 92 (37) |
| Estimated blood loss, mL | 400 (5-3200) | 300 (5-3300) |
| Transfusion given | 46 (18) | 31 (12) |
| Operative time, min | 291 (56-701) | 256 (60-786) |
| Wound classification | ||
| Clean | 16 (6) | 11 (4) |
| Clean-contaminated | 229 (91) | 236 (94) |
| Contaminated/Dirty | 6 (2.4) | 3 (1.2) |
Continuous variables are presented as medians (range) and tested with Fisher’s exact test.
Categorical variables are presented as n (%) and tested with Wilcoxon Rank-Sum test. For yes/no variables, only “YES” counts shown.
NPWT=negative pressure wound therapy; BMI=body mass index
The rate of wound complications was 17.3% (n=44) in the NPWT group and 16.3% (n=41) for the gauze group, for an absolute risk difference of 1% (90% CI: −4.5-6.5%; P=0.77). (Table 2). The diagnosis of wound complication was made after hospital discharge in 78 (92%) of the 85 patients who developed a wound complication (42 [95%] of 44 in the NPWT group and 36 [88%] of 41 in the gauze group). The number and severity of wound complications was also similar between groups; the majority of patients had only one type of wound complication and a grade 1 complication. No patient required surgical intervention for a wound complication. A multivariate logistic regression model was used to account for the statistical difference in diabetes and median EBL between the groups in which the association of treatment group with rate of wound complication remained non-significant (OR, 0.99; 95% CI: 0.62-1.60).
Table 2.
Wound complication rates (primary endpoint) and number/grade of complication subtypes (secondary endpoints)
| NPWT (n=254) | Standard Gauze (n=251) | P | |
|---|---|---|---|
| Overall wound complication | 44 (17.3) | 41 (16.3) | 0.77 |
| Inpatient* | 2 | 5 | |
| Outpatient** | 42 | 36 | |
| Number of wound complication subtypes per patient | 0.49 | ||
| 1 | 33 (13) | 27 (11) | |
| 2 | 7 (2.8) | 12 (5) | |
| 3 | 4 (1.6) | 2 (0.8) | |
| No complication | 210 (83) | 210 (84) | |
| Maximum wound complication grade*** | 0.80 | ||
| 1 | 35 (14) | 36 (14) | |
| 2 | 5 (2) | 3 (1.2) | |
| 3 | 4 (1.6) | 2 (0.8) | |
| No complication | 210 (83) | 210 (84) | |
Inpatient based on assessment while inpatient until discharge or POD 7, whichever came first
Outpatient based on assessment from discharge/POD7 until POD 30 (+/−5 days)
Per MSK Secondary Surgical Events System18
Data represented as counts n (%)
NPWT=negative pressure wound therapy; POD=postoperative day; MSK=Memorial Sloan Kettering Cancer Center
The individual rates of wound infection, separation, seroma, and hematoma (secondary endpoints) were similar between the groups (Appendix 1, available online at http://links.lww.com/xxx). In the group of women with a BMI ≥40 kg/m2, 7 (47%) of the 15 randomized to the NPWT group compared to 6 (35%) of the 17 in the gauze group developed a wound complication (P=0.51). In the NPWT group only, the median LOS was 5 days (range, 3-43 days) in those who developed a wound complication compared to 6 days (range, 2-26) in those who did not (P=0.95).
Skin blistering occurred in 33 patients (13%) in the NPWT group and 3 (1.2%) in the standard gauze group (P<0.001) (Table 3). Contact dermatitis occurred in 6 (2.4%) and 4 (1.6%) patients, respectively (P=0.75). The rate and severity of wound pain was low overall and similar between groups (P=0.29). All other complications and serious adverse events were not related to the negative pressure wound therapy device or gauze.
Table 3.
Wound dressing specific events (tertiary endpoint)
| NPWT (n=254) | Standard Gauze (n=251) | P | |
|---|---|---|---|
| Skin blistering | 33 (13) | 3 (1.2) | <0.001 |
| Contact dermatitis | 6 (2.4) | 4 (1.6) | 0.75 |
| Wound pain* (yes) | 6 (2.4) | 2 (0.8) | 0.29 |
| VAS pain level | |||
| 4 | 1 (0.4) | 0 (0) | |
| 5 | 1 (0.4) | 1 (0.4) | |
| 6 | 2 (0.8) | 0 (0) | |
| 8 | 1 (0.4) | 1 (0.4) | |
| 10 | 1 (0.4) | 0 (0) | |
Using VAS - highest value captured at either the inpatient or outpatient assessment form
Data represented as counts n (%)
NPWT=negative pressure wound therapy; VAS=visual analog scale
We performed additional post-hoc exploratory analyses to test the association of various clinicopathologic factors with the primary outcome of wound complication (Appendix 2 available online at http://links.lww.com/xxx, and 3, available online at http://links.lww.com/xxx). The median BMI was 26 kg/m2 (range, 17-60 kg/m2) for those who did not develop a wound complication and 32 kg/m2 (range, 17-56 kg/m2) for those who did (P<0.001). A wound complication occurred in 13 (41%) of those with a BMI ≥40 kg/m2 and 72 (15%) of those with a BMI <40 kg/m2 (P<0.001).
On multivariate analysis, only increasing BMI (unit of 1) was independently associated with the development of a wound complication (aOR, 1.10; 95%CI: 1.06-1.14; Appendix III). Multivariate logistic regression to predict wound complication for only BMI and trial group showed an aOR of 1.11 (95% CI: 1.07-1.14) for BMI and an aOR of 0.99 (95% CI: 0.60-1.61) for gauze vs. negative pressure wound therapy).
DISCUSSION
The results of our randomized trial do not support the routine use of prophylactic negative pressure wound therapy at the time of laparotomy incision closure in women undergoing surgery for gynecologic malignancies or morbidly obese women undergoing laparotomy for benign indications. The trial was appropriately terminated based on futility, with resulting wound complication rates of 17% for the NPWT group and 16% for the standard gauze group. Exploratory analyses showed that only increasing BMI was associated with the development of a wound complication, which is in line with the known risks of increasing BMI and overall surgical morbidity. Even after adjusting for BMI, negative pressure wound therapy did not lower the rate of wound complications.
A recent meta analysis of 44 randomized clinical trials among a wide range of surgical specialties and procedures using various available negative pressure wound therapy systems reported a reduction in overall SSI, wound dehiscence, and wound seroma but not wound hematoma or skin blistering.22 A statistically significant pooled 40% reduction in SSI risk was reported. The type of negative pressure wound therapy system used was not reported in many of the studies, there was concern for significant biases, and some used patient-based assessments of primary outcome. The authors concluded that the overall evidence for SSI use was moderate. A Cochrane analysis reported negative pressure wound therapy systems may reduce the rate of SSIs but not wound dehiscences,17 which seems somewhat counterintuitive since these devices are superficially placed, mechanical, non-drug devices. One would expect to see the most benefit in superficial SSIs or wound dehiscence rates. The authors concluded the available evidence was of low or very low certainty for all outcomes, with very serious risk of bias and imprecision.17
Our findings are also consistent with two recently published, large, well-designed and conducted randomized clinical trials. Hussamy and colleagues randomized 441 morbidly obese women undergoing cesarean delivery to standard dressing or negative pressure wound therapy.23 This study was designed to find a 50% reduction in the wound complication rate, not overall SSI, similar to our study. The overall wound complication rate was 17% in the NPWT group and 19% in the standard group (P=0.54).23 Costa and colleagues recently reported the results of their randomized trial of 1548 patients undergoing surgery for lower limb fractures in whom the skin was closed.24 They too reported that negative pressure wound therapy did not reduce the rate of wound complications.24 Furthermore, a recent randomized trial evaluating prophylactic negative pressure wound therapy compared with standard dressing immediately after cesarean delivery was also terminated early after a planned interim analysis demonstrated increased adverse events among the former group, as well as futility for the primary outcome – rate of superficial or deep SSIs.25
A key strength of our study is that randomization occurred only after full skin closure. Randomization at the last possible moment is critical to further ensure a significant reduction in clinician bias. Of note, the other two recent negative trials also randomized after skin closure.23,24 Another strength of our study is that primary outcome assessments were performed directly by trained professionals. Additionally, the principal investigator was blinded to the overall composite rate of the primary outcome during the enrollment and conduct of the trial. The majority of patients enrolled in our study were at high risk for wound complications, since the vast majority underwent extensive cytoreductive surgeries for ovarian cancer, and nearly 40% also underwent a concurrent bowel resection.
One of the limitations of our study is that the number of morbidly obese patients was low (n=32). Therefore, the generalizability to the morbidly obese patient undergoing laparotomy is limited. We did not note an obvious benefit within this small subgroup, but this analysis is limited. Another potential limitation is that we chose a composite endpoint of wound complication and we did not look at fascial or organ-space SSI rates. We also were not able to blind surgeons or patients to the randomization group due to the nature of the interventions used (gauze vs negative pressure wound therapy system).
Negative pressure wound therapy systems may be useful in certain settings, such as in the management of wounds left open primarily or complex disrupted postoperative wounds. The associated cost and material waste, however, is not merited as a prophylactic intervention to reduce wound complications after incision closure, as it did not reduce the rate of wound complications in our study. Furthermore, there was significantly more skin blistering with the negative pressure wound therapy system.
Supplementary Material
Acknowledgments
Funding: The protocol was supported in part by KCI/Acelity. This research was supported in part by through the NIH/NCI Cancer Center Support Grant P30 CA008748.
Role of the Funding Source
The protocol was supported in part by KCI/Acelity. The authors had access to relevant aggregated study data and other information (such as study protocol, analytic plan and report, validated data table, and clinical study report) required to understand and report research findings. The authors take responsibility for the presentation and publication of the research findings, have been fully involved at all stages of publication and presentation development, and are willing to take public responsibility for all aspects of the work. All individuals included as authors and contributors who made substantial intellectual contributions to the research, data analysis, and publication or presentation development are listed appropriately. The role of the sponsor in the design, execution, analysis, reporting, and funding is fully disclosed. The sponsor reviewed the manuscript and provided general funding for research purposes. The authors’ personal interests, financial or non-financial, relating to this research and its publication have been disclosed.
Financial Disclosure
Dr. Leitao reports personal fees from Intuitive Surgical, Inc. and JNJ/Ethicon; Dr. Jewell reports personal fees from Covidien/Medtronic; Dr. Chi reports personal fees from Bovie Medical Co., Verthermia Inc. (now Apyx Medical Corp.), C Surgeries, and Biom ‘Up, as well as previous stock ownership in Intuitive Surgical, Inc. and TransEnterix, Inc. Dr. Abu-Rustum reports grants from Stryker/Novadaq, Olympus, and GRAIL. Dr. Iasonos reports personal fees from Mylan. Dr. Martino is a patient safety consultant for Intuitive, Surgical, Inc., JNJ, Medtronic, and CMR; as well as an education speaker for GlaxoSmithKline; and peer reviewer for UpToDate. Dr. Lambrou is a consultant for Ethicon and Intuitive Surgical, Inc. Dr. Diaz is a speaker and has research grant support from Merck and AstraZeneca, and he is a consultant for ConMed. Dr. Cosin is a consultant for Medtronic. All other authors have no conflicts of interest to declare. The other authors did not report any potential conflicts of interest.
Footnotes
Presented at the Society of Gynecologic Oncology 2020 Annual Meeting on Women’s Cancer, March 2020. Available at https://sgoannualmeeting.org/.
Clinical Trial Registration: ClinicalTrials.gov, NCT02682316.
PEER REVIEW HISTORY
Received October 1, 2020. Received in revised form November 4, 2020. Accepted November 12, 2020. Peer reviews and author correspondence are available at http://links.lww.com/xxx.
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