Use of incisional vacuum-assisted closure in the prevention of postoperative infection in high-risk patients who underwent spine surgery: a proof-of-concept study

Bailey A. Dyck Combined Orthopaedic and Neurosurgical Spine Program, London Health Sciences Centre;
Department of Surgery, Schulich School of Medicine and Dentistry, University of Western Ontario; and

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Christopher S. Bailey Combined Orthopaedic and Neurosurgical Spine Program, London Health Sciences Centre;
Lawson Health Research Institute;
Department of Surgery, Schulich School of Medicine and Dentistry, University of Western Ontario; and

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Chris Steyn Combined Orthopaedic and Neurosurgical Spine Program, London Health Sciences Centre;
Department of Surgery, Schulich School of Medicine and Dentistry, University of Western Ontario; and

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Julia Petrakis Combined Orthopaedic and Neurosurgical Spine Program, London Health Sciences Centre;
Arthur Labatt School of Nursing, University of Western Ontario, London, Ontario, Canada

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Jennifer C. Urquhart Combined Orthopaedic and Neurosurgical Spine Program, London Health Sciences Centre;
Lawson Health Research Institute;

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Ruheksh Raj Combined Orthopaedic and Neurosurgical Spine Program, London Health Sciences Centre;
Lawson Health Research Institute;

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Parham Rasoulinejad Combined Orthopaedic and Neurosurgical Spine Program, London Health Sciences Centre;
Lawson Health Research Institute;
Department of Surgery, Schulich School of Medicine and Dentistry, University of Western Ontario; and

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OBJECTIVE

This proof-of-concept study was conducted to determine whether negative-pressure wound therapy, through the use of incisional vacuum-assisted closure (VAC), is associated with a reduction in surgical site infections (SSIs) when compared to standard wound dressings in patients undergoing open posterior spinal fusion who have a high risk of infection.

METHODS

A total of 64 patients were examined; 21 patients received incisional VAC application (VAC group) versus 43 diagnosis-matched patients who received standard wound dressings (control group). Patients in the VAC group were prospectively enrolled in a consecutive series between March 2013 and March 2014 if they met the following diagnostic criteria for high risk of infection: posterior open surgery across the cervicothoracic junction; thoracic kyphosis due to metastatic disease; high-energy trauma; or multilevel revision reconstructive surgery. Patients in the VAC group also met one or more comorbidity criteria, including body mass index ≥ 35 or < 18.5, diabetes, previous radiation at surgical site, chemotherapy, steroid use, bedridden state, large traumatic soft-tissue disruption, or immunocompromised state. Consecutive patients in the control group were retrospectively selected from the previous year by the same high-risk infection diagnostic criteria as the VAC group. All surgeries were conducted by the same surgeon at a single site. The primary outcome was SSI. All patients had 1 year of follow-up after their surgery. Baseline demographics, intraoperative parameters, and postoperative wound infection rates were compared between groups.

RESULTS

Patient demographics including underlying comorbidities were similar, with the exception that VAC-treated patients were malnourished (p = 0.020). VAC-treated patients underwent longer surgeries (p < 0.001) and required more postoperative ICU admissions (p = 0.039). The median length of hospital stay was not different between groups. In total, 9 control patients (21%) developed an SSI, versus 2 VAC-treated patients (10%).

CONCLUSIONS

Patients in this cohort were selected to have an increased risk of infection; accordingly, the rate of SSI was high. However, negative-pressure wound therapy through VAC application to the postoperative incision resulted in a 50% reduction in SSI. No adverse effects were noted secondary to VAC application. The preliminary data confirm the authors’ proof of concept and strongly support the need for a prospective randomized trial.

ABBREVIATIONS

ASA = American Society of Anesthesiologists; BMI = body mass index; LOS = length of hospital stay; NPWT = negative-pressure wound therapy; RCT = randomized controlled trial; SSI = surgical site infection; VAC = vacuum-assisted closure.

OBJECTIVE

This proof-of-concept study was conducted to determine whether negative-pressure wound therapy, through the use of incisional vacuum-assisted closure (VAC), is associated with a reduction in surgical site infections (SSIs) when compared to standard wound dressings in patients undergoing open posterior spinal fusion who have a high risk of infection.

METHODS

A total of 64 patients were examined; 21 patients received incisional VAC application (VAC group) versus 43 diagnosis-matched patients who received standard wound dressings (control group). Patients in the VAC group were prospectively enrolled in a consecutive series between March 2013 and March 2014 if they met the following diagnostic criteria for high risk of infection: posterior open surgery across the cervicothoracic junction; thoracic kyphosis due to metastatic disease; high-energy trauma; or multilevel revision reconstructive surgery. Patients in the VAC group also met one or more comorbidity criteria, including body mass index ≥ 35 or < 18.5, diabetes, previous radiation at surgical site, chemotherapy, steroid use, bedridden state, large traumatic soft-tissue disruption, or immunocompromised state. Consecutive patients in the control group were retrospectively selected from the previous year by the same high-risk infection diagnostic criteria as the VAC group. All surgeries were conducted by the same surgeon at a single site. The primary outcome was SSI. All patients had 1 year of follow-up after their surgery. Baseline demographics, intraoperative parameters, and postoperative wound infection rates were compared between groups.

RESULTS

Patient demographics including underlying comorbidities were similar, with the exception that VAC-treated patients were malnourished (p = 0.020). VAC-treated patients underwent longer surgeries (p < 0.001) and required more postoperative ICU admissions (p = 0.039). The median length of hospital stay was not different between groups. In total, 9 control patients (21%) developed an SSI, versus 2 VAC-treated patients (10%).

CONCLUSIONS

Patients in this cohort were selected to have an increased risk of infection; accordingly, the rate of SSI was high. However, negative-pressure wound therapy through VAC application to the postoperative incision resulted in a 50% reduction in SSI. No adverse effects were noted secondary to VAC application. The preliminary data confirm the authors’ proof of concept and strongly support the need for a prospective randomized trial.

In Brief

This study evaluates the impact of negative-pressure wound therapy on the incidence of surgical site infection in spine surgery, and determines the associated risks. The findings of this study demonstrate that negative-pressure wound therapy application in patients undergoing high-risk spine surgery is safe and reduces surgical site infection. These preliminary data strongly support a role for prophylactic negative-pressure wound therapy in spine surgery, although further research is required.

Surgical site infections (SSIs) place a significant burden on the patient and society following spine surgery. SSIs are associated with significant morbidity, prolonged antibiotic use, increased length of hospital stay (LOS), and increased resource utilization.13

Certain patient populations are at an increased risk of SSI, including those with diabetes, obesity, and disseminated malignancy.17,19 Other risk factors for spinal SSI include spinal trauma, prolonged multilevel instrumented surgery, thoracic spine surgery, and spine surgery after radiation.3 Numerous prophylactic strategies have been reported to mitigate spinal SSI; one such measure is negative-pressure wound therapy (NPWT) applied to the postoperative incision.17

The use of NPWT through vacuum-assisted closure (VAC) is an established means of decreasing infection rates and surgical complications when applied to clean, closed surgical incisions.17 Unlike the more commonly recognized practice of using VAC for secondary wound closure, this technique uses NPWT following primary wound closure. NPWT is believed to decrease infection rates by protecting incision sites from external infectious sources, removing fluid and infectious material from the surgical site, increasing wound microcirculation and tissue oxygen saturation levels, decreasing lateral wound tension, and increasing incisional apposition.8

Use of incisional VAC in orthopedic surgery has been shown to provide a variety of benefits. Literature on primary and revision hip arthroplasty has demonstrated decreased seroma formation, improved wound edge apposition, and decreased SSI.1,4–6,14,15 These results have been corroborated through decreased rates of infection and dehiscence following high-energy fracture fixation for tibial plateau, distal tibia, and calcaneus fractures, as well as in acetabular fracture fixation in obese patients.16,17 A recent prospective study by Stannard et al.17 showed nearly a 50% decrease in wound complications when incisional NPWT is used in the management of calcaneus fractures.

To date, there have been no studies that examine the efficacy of NPWT in treating and preventing SSI in spine surgery. A recent systematic review of NPWT for spinal wound infection therapy highlighted the potential for benefit in this population, as well as the need for further study examining the role of VAC as prophylactic treatment to prevent SSI.13 We believe that patients at increased risk of SSI would most benefit from the use of NPWT. Therefore, the purpose of this pilot study was to explore whether there is a difference in the incidence of SSI in patients undergoing spine surgery who are at high risk for postoperative wound infection and who are treated with NPWT through the use of incisional VAC. In addition, we sought to determine if there are any significant risks associated with this new wound closure modality. This is a proof-of-concept paper that may hopefully lead to a randomized controlled trial (RCT).

Methods

Study Design and Participants

This retrospective cohort study was conducted based on a single surgeon’s clinical practice at a tertiary care hospital. For the present study, patients were identified who underwent open posterior spinal fusion during 2012 through 2014. Approval was obtained from our institutional research ethics board.

Two groups of spine surgery patients at high risk for postoperative wound infection were recruited: 1) patients who received incisional NPWT treatment through VAC application to the postoperative incision (VAC group); and 2) diagnosis-matched patients treated with conventional primary incisional closure and standard postoperative wound dressings (control group). The VAC group was composed of a consecutive series of patients who were prospectively selected between March 2013 and March 2014, who met the following diagnostic criteria for high risk of infection: posterior open surgery across the cervicothoracic junction; thoracic kyphosis due to metastatic disease; high-energy trauma; or multilevel revision reconstructive surgery. These patients also possessed one or more of the following comorbidity criteria: body mass index (BMI) ≥ 35.0 or < 18.5; immunocompromised state (diabetes mellitus, renal failure, liver failure, HIV, neutropenia [white blood cell count < 3.0], or use of biological agents or chemotherapy); previous radiation treatment to the location of operation; preoperative steroid use; bedridden state; or associated large, traumatic, soft-tissue disruption. Patients in the control group were a consecutive series of patients retrospectively identified from the same surgeon’s local spine surgery database from the year prior (March 2012–March 2013). Control patients had the same high-risk infection diagnostic criteria as the VAC group. However, control patients were not matched to the comorbidity criteria. Exclusion criteria for both groups included patient age < 18 years, < 6 weeks of clinical follow-up, incomplete follow-up notes, and anterior surgical approach.

Data Collection

Baseline characteristics obtained for all patients included age, sex, BMI, and functional status (bedbound versus ambulatory). Comorbidity characteristics, including active cancer, current smoker status, immunocompromised state, steroid use, nutritional status (malnourished was defined as a BMI < 18.5 kg/m2 or pathological weight loss), and hypoalbuminemia, were also recorded. Procedural characteristics included American Society of Anesthesiologists (ASA) class, number of operative levels, duration of operation, estimated blood loss, and LOS including ICU admission. Data were determined from the patient hospital records.

Surgical Technique, Incisional VAC Placement, and Postoperative Care

All patients received the same pre- and perioperative antibiotic protocol, which included administration of preoperative antibiotics 1 hour before surgical incision but no later than 15 minutes prior to incision, and a second dose of antibiotics intraoperatively at the 4-hour mark if the surgery lasted longer than 4 hours. Cefazolin (1 g) was used in the majority of cases unless the patient had reported an allergic reaction, in which case vancomycin (1 g) was used. Both groups underwent the exact same technique for closure and ultimately only differed in whether standard dry gauze was used or an incisional VAC was placed (Fig. 1). In both groups, the deep layer was closed using a 1-0 Vicryl Rapide suture in a running-stitch fashion to close fascia only. Meticulous suturing technique was carried out in order to ensure a watertight closure. The subcutaneous layer was closed using a running 2-0 Vicryl Rapide suture, and finally the skin was closed using staples and interrupted vertical mattress 1-0 Prolene sutures. A secondary (10-Fr) deep drain was placed in both groups. After complete closure, both wounds were cleaned using saline-soaked gauze and dried in the control group with standard dry gauze and Mefix self-adhesive fabric tape under sterile conditions. The dressing was changed according to standard nursing technique for our institution at 3 days after surgery. In cases in which the dressing was saturated, a dressing change was completed at an earlier interval as necessary.

FIG. 1.
FIG. 1.

Flow diagram of the wound closure paradigm.

In our study group, an incisional VAC dressing was used according to the manufacturer’s recommendations in addition to primary wound closure. This involved protecting the exposed skin edges of the clean, closed incision and surrounding wound area with a VAC Drape, followed by placement of 1-inch × 1-inch VAC Granufoam cut to fit the size of the incision, and finally coverage with a VAC Drape and SensaT.R.A.C. Pad over the incision and surrounding wound area to make an airtight wound seal. Negative pressure was applied using a standard KCI Prevena V.A.C. device at 75 mm Hg (all VAC devices and materials obtained from KCI/Acelity). The NPWT was continued for a total of 5 days (Fig. 2). A secondary (10-Fr) deep drain was placed outside of the VAC dressing.

FIG. 2.
FIG. 2.

Incisional VAC application (VAC devices and materials obtained from KCI/Acelity). A: Primary closure. B: Exposed skin edges of the clean, closed incision are covered with a VAC Drape. C: A 1-inch × 1-inch piece of VAC Granufoam is cut to fit the size of the incision. D: A VAC Drape and SensaT.R.A.C. Pad cover the incision and surrounding wound area to make an airtight seal. Negative pressure is applied using a KCI Prevena V.A.C. device at 75 mm Hg. Asterisks mark a secondary (10-Fr) deep drain that is placed outside of the VAC dressing. Figure is available in color online only.

A standard absorbent dressing, identical in both groups, was applied after the 5th postoperative day in accordance with current hospital protocol. An identical postoperative standard-of-care protocol for mobilization was implemented in both groups. This involved continuation of the patients’ own medications as well as administration of 24 hours of intravenous antibiotics for infection prophylaxis and use of deep venous thrombosis prophylaxis (Fragmin, 5000 IU daily) in those with spinal cord injury. The patients all engaged in activity as tolerated and if possible were mobilized with the aid of physiotherapy on postoperative day 1. They were encouraged to sleep and rest in any position that was comfortable for them. The patients did not receive any adjunctive treatment for infection prophylaxis such as povidone-iodine wash or intrawound vancomycin powder. Patients were discharged as per routine hospital policy, and follow-up occurred at 6 weeks, 3 months, 6 months, and 12 months.

Diagnostic Assessment

All patients were monitored for the development of wound complications such as wound dehiscence and postoperative SSI, which was defined as either superficial or deep. The Centers for Disease Control and Prevention definitions were used to make this diagnosis.7 In brief, deep SSI occurred within 1 year of surgery and involved at least one of the following: purulent drainage from deep tissues; a deep incision that spontaneously dehisced or was deliberately opened by a surgeon and was culture positive or not cultured when a fever, localized pain, or tenderness was present; an abscess or other evidence of infection involving the deep incision was found on direct examination during reoperation or with histopathological or radiographic examination; or a diagnosis by a surgeon. All deep infections were treated with irrigation and debridement as well as intravenous antibiotics.

Statistical Analyses

Baseline demographics, intraoperative variables, and postoperative details were categorized from patients’ medical records. Data were analyzed by means of 2-tailed t-test or Mann-Whitney test (continuous data) and chi-square test or Fisher’s exact test (categorical data) by using JASP software. LOS was right-skewed, and there were 9 patients who were discharged to another facility for ongoing or long-term care in whom we could not determine the total length of stay in a hospital setting. Therefore LOS was converted to a categorical variable as defined by quartiles, and these patients were grouped in the highest quartile. The only instances of missing data pertained to BMI, preoperative albumin, and estimated blood loss. For these variables complete case analysis was used, and the number of cases included is indicated in the corresponding results table.

Results

Baseline Characteristics

Among patients undergoing surgery during 2013–2014, 21 were identified as at high risk for postoperative infection based on our defined criteria, and underwent postoperative incisional VAC application. Retrospective review of the same surgeon’s database from the year prior identified 43 patients with similar high-risk diagnoses; comorbidities were not matched. These patients served as the control group. Specific details of diagnosis, etiology, procedure indication, and anatomical level for each patient receiving VAC can be found in Table 1. All patients had 1 year of follow-up after their surgery.

TABLE 1.

Surgical details in 21 VAC-treated patients who underwent open posterior spinal fusion

Case No.DiagnosisEtiologyProcedure
1T4 metastatic cancer w/ secondary thoracic myelopathyMetastatic lung adenocarcinomaT4 intralesional tumor excision, T2–7 decompression, stabilization, posterolat partial corpectomy, & anterior column reconstruction
2Cervical myelopathyFall from ladderC7–T1 decompression, C6–T2 posterior fusion
3C6–7 fracture w/ 3-column instabilityFall down stairsC5–T2 posterior fusion
4T9 metastatic cancer w/ cord compressionMetastatic lung adenocarcinomaT9 tumor resection & corpectomy, decompression, & T7–12 posterior fusion
5T2–4 metastatic cancer w/ thoracic myelopathy & pathological fracture/dislocation of T2–3Metastatic lung adenocarcinomaT2–4 intralesional tumor excision, decompression, stabilization, posterolat partial corpectomy, & anterior column reconstruction
6T5–6 metastatic cancer w/ complete SCIMetastatic breast cancerTumor debulking, T3–9 decompression, stabilization, & T5–6 right-sided vertebroplasty
7T4 metastatic cancer w/ cord compression & thoracic myelopathyMetastatic renal cell cancerT4 intralesional tumor excision, T2–7 decompression, stabilization, posterolateral T4 corpectomy, & anterior column reconstruction
8T7 3-column fractureHit by bull (ankylosing spondylitis)T5–9 posterior stabilization & fusion
9L2–3 fracture dislocation, L5 burst fracture, cauda equina injuryFall from height (polytrauma)L1–3, L4–S1 realignment & decompression, T11–ilium instrumentation, traumatic dural tear
10T9 pathological burst fracture w/ thoracic myelopathyOsteoporosis (RA)T7–11 decompression, stabilization, & fusion
11T3–4 fracture dislocation w/ incomplete SCIMotorcycle accidentT1–6 decompression, T3–4 fracture realignment, & stabilization
12C7–T1 instability post C2–7 fusion (for spinal stenosis w/ myelopathy)Snowmobile accident (years prior)C5–T3 revision, decompression, instrumentation, & C7–T1 left-sided foraminotomy
13Thoracic plasmacytoma w/ incomplete SCIAnterior thoracic plasmacytoma (multiple myeloma)Intralesional tumor debulking, T3–4, T11–12 decompression, T3–12 stabilization
14C7–T1 instability post C2–7 fusion (for spinal stenosis w/ myelopathy)Pain w/ spondylolisthesis C7–T1Extension of fusion C7–T2
15T11 metastatic cancer w/ secondary pathological fracture, spinal stenosis, & complete SCIMetastatic renal cell cancerT12 intramarginal tumor debulking, T11–L1 decompression, T10–L2 stabilization, & partial bilat corpectomy
16T11 metastatic cancer w/ secondary pathological fracture & incomplete SCIMetastatic breast cancerIntralesional tumor debulking, T10–12 decompression, partial bilat corpectomy, T9–L1 stabilization, & anterior column resection
17C6–7 fracture dislocationFallC4–T2 posterior stabilization & fusion
18C5–6 fracture in an ankylosed spineFallC4–T2 posterior stabilization & fusion
19T4 3-column fractureFallT3–4 decompression, T1–7 stabilization, & fusion
20C6–7, C7–T1, T5–6, T6–7 fracture dislocations; T6 burst fracture; complete SCIMotor vehicle crashC5–T9 stabilization & fusion, traumatic dural tear repair
21C7 3-column fracture in ankylosing spondylitisMotor vehicle crashC4–T4 stabilization & fusion

RA = rheumatoid arthritis; SCI = spinal cord injury.

Baseline demographic characteristics are shown in Table 2. The control and VAC groups were similar in average age (58.9 vs 59.5 years; p = 0.892), sex distribution (35% female vs 38% female; p = 0.801), and mean BMI (24.9 vs 26.1 kg/m2; p = 0.466). Likewise, patients were largely similar in underlying comorbidities. Specifically, there was no difference in previously diagnosed diabetes (16% control vs 24% VAC; p = 0.469), active malignancy (37% vs 48%; p = 0.426), previous surgical site radiation (26% vs 38%; p = 0.304), and functional status (7% bedbound vs 5% bedbound; p = 0.731). There was a propensity toward meeting the diagnosis of immunocompromised in VAC patients, defined as previous diagnosis of diabetes, renal failure, liver failure, cardiac failure, HIV, neutropenia, or active use of biological medications or chemotherapy; however, this was nonsignificant (42% vs 67%; p = 0.062). Significantly more VAC-treated patients were malnourished (7% control vs 29% VAC; p = 0.020) (Fig. 3A).

TABLE 2.

Baseline demographic characteristics of 64 patients who underwent open posterior spinal fusion

CharacteristicControl Group, n = 43VAC Group, n = 21p Value
Age, yrs0.892
 Mean ± SD58.9 ± 16.259.5 ± 16.5
 Range19–8521–83
 95% CI52.0–65.852.4–66.5
M/F (% female)28/15 (35%)13/8 (38%)0.801
BMI, kg/m2*0.466
 Mean ± SD24.9 ± 4.926.1 ± 4.7
 Range16.5–37.118.5–35.0
 95% CI22.91–27.0524.07–28.11
Malnutrition3 (7%)6 (29%)0.020
 Preop albumin in g/L, mean ± SD*36.4 ± 6.835.3 ± 6.00.591
Diabetes7 (16%)5 (24%)0.469
Cancer diagnosis16 (37%)10 (48%)0.426
Previous radiation to surgical site11 (26%)8 (38%)0.304
Preop steroid use14 (33%)9 (43%)0.420
Immunocompromised18 (42%)14 (67%)0.062
Smoking status*
 Current12 (28%)5 (25%)0.768
 Previous26 (60%)10 (50%)0.375
Bedbound preop3 (7%)1 (5%)0.731

Unless otherwise indicated, values are expressed as the number of patients (%). Boldface type indicates statistical significance.

Totals were lower due to missing data for the following variables: BMI, total of 25 available in control group and 18 in VAC group; preoperative albumin, total of 32 available in control group and 14 in VAC group; smoking status, total of 42 available in control group and 20 in VAC group.

Immunocompromise was defined by the diagnosis of any of the following: diabetes, renal failure, liver failure, cardiac failure, HIV, neutropenia, or use of biological medications.

FIG. 3.
FIG. 3.

Bar graphs showing significant differences between control and VAC-treated patients. A: Significantly more VAC-treated patients were malnourished at baseline. Values are percents ± SE. B: Average length of surgery was significantly longer for VAC-treated patients. Values are mean ± 95% CI. C: Significantly more VAC-treated patients required postoperative ICU admission. Values are percents ± SE. *p < 0.05; **p < 0.001.

Intraoperative Characteristics

Intraoperative variables are shown in Table 3. There was no difference between groups in preoperative ASA classification of fitness (p = 0.393), corroborating the lack of significant difference in comorbid diagnoses. VAC patients on average waited twice as many days from first consultation to surgery, but this was not statistically significantly different between groups (control 2.9 ± 3.3 days vs VAC 6.3 ± 8.0 days; p = 0.171). Length of surgery was significantly longer for VAC patients (control 184.9 ± 74.2 minutes vs VAC 260.0 ± 88.0 minutes; p < 0.001) (Fig. 3B); however, estimated blood loss, although nearly double, did not reach significance (control 786 ± 725 ml vs VAC 1394 ± 1146 ml; p = 0.075). Surgeries on average spanned 5–6 vertebral levels (control 5.4 ± 1.9 vs VAC 6.4 ± 2.2; p = 0.063), with equivalent involvement of the cervicothoracic (control 30% vs VAC 43%; p = 0.318) or thoracolumbar (control 16% vs VAC 14%; p = 0.837) levels. Last, the median LOS (control 16 days vs VAC 16 days) and the proportion of patients who stayed ≤ 7 days, 8–16 days, 17–34 days, and ≥ 35 days was similar between groups (p = 0.383); however, significantly more VAC-treated patients required postoperative admission to the ICU (control 19% vs VAC 43%; p = 0.039) (Fig. 3C).

TABLE 3.

Operative details in 64 patients who underwent open posterior spinal fusion

VariableControl Group, n = 43VAC Group, n = 21p Value
Time from consultation to surgery in days, mean ± SD2.9 ± 3.36.3 ± 8.00.171
ASA class
 I1 (2.3%)0 (0.0%)0.393
 II3 (7.0%)1 (4.8%)
 III11 (25.6%)6 (28.6%)
 IV25 (58.1%)9 (42.9%)
 V0 (0.0%)1 (4.8%)
 Emergency surgery in patients w/ ASA class V3 (7%)4 (19%)
Length of surgery in mins, mean ± SD184.9 ± 74.2260.0 ± 88.0<0.001
 Median length of surgery in mins165231
Estimated blood loss in ml, mean ± SD*786 ± 7251394 ± 11460.075
Postop hemoglobin drop in g/L, mean ± SD−14.79 ± 18.26−15.14 ± 21.230.945
No. of surgical levels involved, mean ± SD5.4 ± 1.96.4 ± 2.20.063
 CT junction involved13 (30%)9 (43%)0.318
 TL junction involved7 (16%)3 (14%)0.837
Median LOS in days1616
LOS0.383
 ≤7 days10 (23%)4 (19%)
 8–16 days9 (21%)5 (24%)
 17–34 days7 (16%)7 (33%)
 ≥35 days17 (40%)5 (24%)
ICU admission required8 (19%)9 (43%)0.039

CT = cervicothoracic; TL = thoracolumbar.

Unless otherwise indicated, values are expressed as the number of patients (%). Boldface type indicates statistical significance.

Totals were lower due to missing data for the following variable: estimated blood loss, total of 24 available in control group and 18 in VAC group.

Postoperative Infections

Postoperative SSIs and detailed patient demographics and surgical details are provided in Tables 4 and 5. In total, 21% of patients in the control group developed an SSI, whereas only 10% of patients in the VAC group experienced one (9/43 vs 2/21; p = 0.314) (Fig. 4). In the control group, 4 of the 9 infections were superficial, whereas in both patients with infections in the VAC group the SSIs were deep. All deep infections were treated with oral antibiotics and irrigation and debridement. The time to infection was 46.0 ± 39.6 days in the control group and 36.5 ± 15.4 days in the VAC group, a nonsignificant difference (p = 0.763). The majority of infections occurred within 6 weeks of surgery. The most commonly isolated organism in both groups was Staphylococcus aureus. Of the 3 control cases that were culture negative, all had been treated with 2 weeks of oral antibiotics, and then subsequent irrigation and debridement surgery.

TABLE 4.

Postoperative details in 64 patients who underwent open posterior spinal fusion

VariableControl Group, n = 43VAC Group, n = 21p Value
SSI9 (21%)2 (10%)0.314
Time to infection in days, mean ± SD46.0 ± 39.636.5 ± 15.40.763
 Deep SSI52
Global need for reop6 (14%)3 (14%)0.971
 Infection52
 Wound dehiscence01
 Retained drain products10
Residual SCI14 (33%)9 (43%)0.420
 Paraplegia—complete & incomplete118
 Bowel & bladder dysfunction54
 Central cord syndrome20
 Brown-Séquard syndrome10

Unless otherwise indicated, values are expressed as the number of patients (%).

TABLE 5.

Demographic and clinical characteristics of 11 patients who developed an SSI after undergoing open posterior spinal fusion

Case No.Age (yrs), SexLength of Op (mins)Level of SurgeryICUDiabeticMalnourishedPast Radiation at Surgical SitePreop SteroidsImmunocompromisedSmokerType of InfectionOrganismTime to Infection (days)
Control group
 169, F246T7–L1NoNoNoYesYesYes: active malignancyPreviousDeepNo growth24
 256, M190C7–T6NoNoYesYesYesYes: malnourishedYesSuperficialNot tested126
 374, M306L1–5NoYesNoYesNoNoNoDeepStaphylococcus epidermidis98
 463, F265C5–T4NoNoNoYesYesNoNoDeepNo growth37
 574, F112C4–7YesNoNoNoNoNoPreviousSuperficialNot tested13
 668, F114C7–T4NoNoNoYesYesYes: on chemotherapyNoDeepS. aureus17
 774, M148C3–T2NoNoNoNoNoNoYesSuperficialNot tested22
 857, F68C6–6NoNoNoNoNoNoNoDeepNo growth27
 919, M119C3–5NoYesNoNoNoYes: type 1 diabetesNoSuperficialNot tested50
Avg61.61741 (11%)2 (22%)1 (11%)5 (56%)4 (44%)4 (44%)2 (22%)46.0
VAC group
 162, F190T7–11NoNoYesNoNoYes: LT methotrexate for RAYesDeepMethicillin-sensitive S. aureus62
 265, F183C7–T2NoYesNoNoNoYes: diabetic (revision surgery ×2)NoDeepMethicillin-resistant S. aureus11
Avg63.5186.501 (50%)1 (50%)002 (100%)1 (50%)36.5

Avg = average; LT = long-term.

FIG. 4.
FIG. 4.

Bar graph showing the incidence of SSIs in control (21%) and VAC-treated (9.5%) patients. The relative risk of developing an SSI with VAC treatment was 0.5 (95% CI 0.1–1.9, p = 0.491). Values are percent ± SE.

Discussion

The purpose of this pilot study was to explore whether the use of NPWT, through the application of an incisional VAC, reduces the incidence of SSI in patients undergoing spine surgery who are at high risk for postoperative wound infection. A 10% SSI rate was identified in the VAC group versus a 21% rate in the control patients with standard postoperative dressing. Patients in the present study were selected for having an increased risk of infection based on both their comorbidity and the nature of their surgeries. We therefore expected the rates of SSI to be higher than those reported in the adult spine surgery literature—9%–12% for fusion with instrumentation—and more similar to those reported in high-risk patients, including a rate of up to 20% in patients with metastatic spine tumors.2–4,10,15,18 Despite additional risk factors in the incisional VAC group including malnourishment, longer surgical time, and increased admission to the ICU, our results showed a 50% lower complication rate after VAC treatment; a finding that was not statistically significant. This nonsignificance is probably due to small sample sizes leading to an underpowered analysis. Based on these complication rates in this pilot study, 90 patients per group would be required to detect a statistically significant difference (α statistic, p < 0.05, 80% power). In addition, we sought to determine if there were any significant risks associated with this new wound closure modality. No adverse events secondary to VAC application were identified.

The theory behind NPWT strongly suggests its efficacy in reducing surgical infection rates. NPWT has been shown to protect incisions from external infectious sources, remove fluid and infectious material, increase microcirculation and oxygen saturation, and decrease lateral tissue tension, thereby increasing incisional apposition.8 Despite this evidence, the literature is inconclusive in terms of the success of incisional VAC therapy in reducing infection rates. Several examples are available in the literature. Masden et al.11 examined the use of NPWT in amputation surgery, finding a 13.5% infection rate when using standard dry dressings versus 6.8% when using VAC; however, these results were nonsignificant, due to the small sample size. Mark et al.9 demonstrated similarly effective reductions in SSI in morbidly obese patients with multiple comorbidities undergoing cesarean section, with a 10.4% infection rate in standard dressing versus 0% in VAC. Yet again, due to small sample sizes, results were nonsignificant. Stannard et al.,17 using large sample sizes of patients healing from high-risk lower-extremity fractures, were able to achieve significance, with an impressive relative reduction of infection of 1.9 in VAC-treated patients (19% SSI in controls vs 10% in VAC). As such, consensus is largely that NPWT is effective in reducing surgical infections.

Much less research has been conducted on the efficacy of NPWT in the prevention of SSI in spinal surgery. Several studies have looked at using VAC for the treatment of established postoperative infection in spine surgery. In their systematic review, Ousey et al.13 identified 10 retrospective studies and 4 case reports in which VAC treatment was used for spinal infection, with no RCTs. Only one of these studies examined more than 50 patients. Their review emphasized the need for larger prospective RCTs, as well as for investigations into the role of NPWT in prophylactic treatment to prevent spinal infection. To date, no such studies exist. Recently, Nordmeyer et al.12 conducted an RCT examining the effect of NPWT on seroma formation when primarily applied to incisional wounds in patients with spinal fractures. Twenty patients, 10 with standard wound dressing and 10 with VAC, were followed. At postoperative days 5 and 10, the patients in whom VAC was performed had significantly lower seroma volumes and significantly fewer days of wound secretion. Long-term SSI rates were not reported, and the patient demographics and comorbid conditions were not provided. With that in mind, to the best of our knowledge, ours are the first published data reporting the effect of prophylactic NPWT on infection rates in spine surgery.

Besides infection rates, VAC therapy resulted in improvement in other parameters of morbidity. Despite having significantly longer surgeries (185 minutes in control patients vs 260 minutes in VAC patients) and a significantly higher number of patients requiring ICU admission (19% of controls vs 43% of VAC patients), the median LOS was identical at 16 days, and overall LOS was not significantly different. This is consistent with previous research on NPWT use in high-energy orthopedic fracture fixation; patients were ready for discharge half a day earlier than control patients, suggesting a further role for primary VAC in reducing patient morbidity and hospital-associated health costs in high-risk patients.9,17

One of the strengths of this study is the surgical similarity between cohorts, with no significant differences in number of operative levels or involvement of cervicothoracic and thoracolumbar junction. Despite prospective selection of patients for incisional VAC application, the two groups did not significantly differ in underlying comorbidities, including diabetes, active malignancy, previous surgical site radiation, immunocompromise, and functional status. However, VAC-treated patients did have longer surgical times, and were prospectively selected as patients with a high probability of wound complications. With the trend supporting decreased SSI in incisional VAC-treated patients, this strengthens the conclusion toward the efficacy of prophylactic NPWT in spine surgery. Other strengths of this pilot study include use of a single-surgeon database and prospective selection and follow-up of the incisional VAC-treated group.

Several study limitations exist. As a proof-of-concept study, the sample sizes available for analysis were limited, and as demonstrated by power calculations, were not large enough to produce a significant result. Furthermore, although control group data were carefully selected to facilitate fair comparison between the two groups, the patients receiving VAC had more risk factors for infection including longer surgeries, more ICU admissions, and being malnourished; however, these factors would create a bias toward a higher risk of infection in the VAC group, thereby underestimating the treatment effect. Furthermore, the data were collected retrospectively and we did not control for intrinsic differences in the surgeries of patients, which may be sources of treatment bias that impact the interpretation of our results. Also, generalizability to other centers or a subcohort of this group (i.e., cancer patients versus trauma patients) cannot be assumed. To overcome these shortcomings, a current multicenter prospective RCT is underway externally to validate the role of NPWT in reducing SSI in spine surgery. It would also be of future utility to examine whether there is any cost-effectiveness of NPWT regarding the socioeconomic burden of infection in spine surgery, for example, in reducing LOS, readmission and reoperation rates, and long-term infection-related morbidity.

Conclusions

Our current study explores the role of prophylactic incisional NPWT in reducing postoperative infection in patients with a high risk of postoperative wound infection following open posterior spine surgery. Our preliminary results support an effective role for incisional VAC therapy in reducing postoperative SSI in comparison with the standard wound dressings. Based on the data of our pilot study, it is clear that further prospective RCTs are needed to establish significant outcomes to affect clinical change.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Bailey, Dyck, Rasoulinejad. Acquisition of data: Dyck, Steyn, Petrakis. Analysis and interpretation of data: Bailey, Dyck, Steyn, Petrakis, Urquhart, Rasoulinejad. Drafting the article: Dyck. Critically revising the article: Bailey, Urquhart, Raj, Rasoulinejad. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Bailey. Statistical analysis: Dyck, Urquhart. Administrative/technical/material support: Raj. Study supervision: Bailey, Rasoulinejad.

References

  • 1

    Altintas B, Biber R, Brem MH: The accelerating effect of negative pressure wound therapy with Prevena™ on the healing of a closed wound with persistent serous secretion. Int Wound J 12:662663, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Anderson PA, Savage JW, Vaccaro AR, Radcliff K, Arnold PM, Lawrence BD, et al.: Prevention of surgical site infection in spine surgery. Neurosurgery 80 (3S):S114S123, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Carl HM, Ahmed AK, Abu-Bonsrah N, De la Garza Ramos R, Sankey EW, Pennington Z, et al.: Risk factors for wound-related reoperations in patients with metastatic spine tumor. J Neurosurg Spine 28:663668, 2018

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Chahoud J, Kanafani Z, Kanj SS: Surgical site infections following spine surgery: eliminating the controversies in the diagnosis. Front Med (Lausanne) 1:7, 2014

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Gillespie BM, Rickard CM, Thalib L, Kang E, Finigan T, Homer A, et al.: Use of negative-pressure wound dressings to prevent surgical site complications after primary hip arthroplasty: a pilot RCT. Surg Innov 22:488495, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Hansen E, Durinka JB, Costanzo JA, Austin MS, Deirmengian GK: Negative pressure wound therapy is associated with resolution of incisional drainage in most wounds after hip arthroplasty. Clin Orthop Relat Res 471:32303236, 2013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Horan TC, Andrus M, Dudeck MA: CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infections in the acute care setting. Am J Infect Control 36:309332, 2008

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Horch RE: Incisional negative pressure wound therapy for high-risk wounds. J Wound Care 24 (4 Suppl):2128, 2015

  • 9

    Mark KS, Alger L, Terplan M: Incisional negative pressure therapy to prevent wound complications following cesarean section in morbidly obese women: a pilot study. Surg Innov 21:345349, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Martin JR, Adogwa O, Brown CR, Bagley CA, Richardson WJ, Lad SP, et al.: Experience with intrawound vancomycin powder for spinal deformity surgery. Spine (Phila Pa 1976) 39:177184, 2014

    • Crossref
    • PubMed
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  • 11

    Masden D, Goldstein J, Endara M, Xu K, Steinberg J, Attinger C: Negative pressure wound therapy for at-risk surgical closures in patients with multiple comorbidities: a prospective randomized controlled study. Ann Surg 255:10431047, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Nordmeyer M, Pauser J, Biber R, Jantsch J, Lehrl S, Kopschina C, et al.: Negative pressure wound therapy for seroma prevention and surgical incision treatment in spinal fracture care. Int Wound J 13:11761179, 2016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Ousey KJ, Atkinson RA, Williamson JB, Lui S: Negative pressure wound therapy (NPWT) for spinal wounds: a systematic review. Spine J 13:13931405, 2013

  • 14

    Pachowsky M, Gusinde J, Klein A, Lehrl S, Schulz-Drost S, Schlechtweg P, et al.: Negative pressure wound therapy to prevent seromas and treat surgical incisions after total hip arthroplasty. Int Orthop 36:719722, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15

    Parchi PD, Evangelisti G, Andreani L, Girardi F, Darren L, Sama A, et al.: Postoperative spine infections. Orthop Rev (Pavia) 7:5900, 2015

  • 16

    Reddix RN Jr, Tyler HK, Kulp B, Webb LX: Incisional vacuum-assisted wound closure in morbidly obese patients undergoing acetabular fracture surgery. Am J Orthop 38:446449, 2009

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17

    Stannard JP, Volgas DA, McGwin G III, Stewart RL, Obremskey W, Moore T, et al.: Incisional negative pressure wound therapy after high-risk lower extremity fractures. J Orthop Trauma 26:3742, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Van Hal M, Lee J, Laudermilch D, Nwasike C, Kang J: Vancomycin powder regimen for prevention of surgical site infection in complex spine surgeries. Clin Spine Surg 30:E1062E1065, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Veeravagu A, Patil CG, Lad SP, Boakye M: Risk factors for postoperative spinal wound infections after spinal decompression and fusion surgeries. Spine (Phila Pa 1976) 34:18691872, 2009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • Collapse
  • Expand
  • FIG. 1.

    Flow diagram of the wound closure paradigm.

  • FIG. 2.

    Incisional VAC application (VAC devices and materials obtained from KCI/Acelity). A: Primary closure. B: Exposed skin edges of the clean, closed incision are covered with a VAC Drape. C: A 1-inch × 1-inch piece of VAC Granufoam is cut to fit the size of the incision. D: A VAC Drape and SensaT.R.A.C. Pad cover the incision and surrounding wound area to make an airtight seal. Negative pressure is applied using a KCI Prevena V.A.C. device at 75 mm Hg. Asterisks mark a secondary (10-Fr) deep drain that is placed outside of the VAC dressing. Figure is available in color online only.

  • FIG. 3.

    Bar graphs showing significant differences between control and VAC-treated patients. A: Significantly more VAC-treated patients were malnourished at baseline. Values are percents ± SE. B: Average length of surgery was significantly longer for VAC-treated patients. Values are mean ± 95% CI. C: Significantly more VAC-treated patients required postoperative ICU admission. Values are percents ± SE. *p < 0.05; **p < 0.001.

  • FIG. 4.

    Bar graph showing the incidence of SSIs in control (21%) and VAC-treated (9.5%) patients. The relative risk of developing an SSI with VAC treatment was 0.5 (95% CI 0.1–1.9, p = 0.491). Values are percent ± SE.

  • 1

    Altintas B, Biber R, Brem MH: The accelerating effect of negative pressure wound therapy with Prevena™ on the healing of a closed wound with persistent serous secretion. Int Wound J 12:662663, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 2

    Anderson PA, Savage JW, Vaccaro AR, Radcliff K, Arnold PM, Lawrence BD, et al.: Prevention of surgical site infection in spine surgery. Neurosurgery 80 (3S):S114S123, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 3

    Carl HM, Ahmed AK, Abu-Bonsrah N, De la Garza Ramos R, Sankey EW, Pennington Z, et al.: Risk factors for wound-related reoperations in patients with metastatic spine tumor. J Neurosurg Spine 28:663668, 2018

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Chahoud J, Kanafani Z, Kanj SS: Surgical site infections following spine surgery: eliminating the controversies in the diagnosis. Front Med (Lausanne) 1:7, 2014

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 5

    Gillespie BM, Rickard CM, Thalib L, Kang E, Finigan T, Homer A, et al.: Use of negative-pressure wound dressings to prevent surgical site complications after primary hip arthroplasty: a pilot RCT. Surg Innov 22:488495, 2015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Hansen E, Durinka JB, Costanzo JA, Austin MS, Deirmengian GK: Negative pressure wound therapy is associated with resolution of incisional drainage in most wounds after hip arthroplasty. Clin Orthop Relat Res 471:32303236, 2013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Horan TC, Andrus M, Dudeck MA: CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infections in the acute care setting. Am J Infect Control 36:309332, 2008

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Horch RE: Incisional negative pressure wound therapy for high-risk wounds. J Wound Care 24 (4 Suppl):2128, 2015

  • 9

    Mark KS, Alger L, Terplan M: Incisional negative pressure therapy to prevent wound complications following cesarean section in morbidly obese women: a pilot study. Surg Innov 21:345349, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 10

    Martin JR, Adogwa O, Brown CR, Bagley CA, Richardson WJ, Lad SP, et al.: Experience with intrawound vancomycin powder for spinal deformity surgery. Spine (Phila Pa 1976) 39:177184, 2014

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 11

    Masden D, Goldstein J, Endara M, Xu K, Steinberg J, Attinger C: Negative pressure wound therapy for at-risk surgical closures in patients with multiple comorbidities: a prospective randomized controlled study. Ann Surg 255:10431047, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Nordmeyer M, Pauser J, Biber R, Jantsch J, Lehrl S, Kopschina C, et al.: Negative pressure wound therapy for seroma prevention and surgical incision treatment in spinal fracture care. Int Wound J 13:11761179, 2016

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Ousey KJ, Atkinson RA, Williamson JB, Lui S: Negative pressure wound therapy (NPWT) for spinal wounds: a systematic review. Spine J 13:13931405, 2013

  • 14

    Pachowsky M, Gusinde J, Klein A, Lehrl S, Schulz-Drost S, Schlechtweg P, et al.: Negative pressure wound therapy to prevent seromas and treat surgical incisions after total hip arthroplasty. Int Orthop 36:719722, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 15

    Parchi PD, Evangelisti G, Andreani L, Girardi F, Darren L, Sama A, et al.: Postoperative spine infections. Orthop Rev (Pavia) 7:5900, 2015

  • 16

    Reddix RN Jr, Tyler HK, Kulp B, Webb LX: Incisional vacuum-assisted wound closure in morbidly obese patients undergoing acetabular fracture surgery. Am J Orthop 38:446449, 2009

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 17

    Stannard JP, Volgas DA, McGwin G III, Stewart RL, Obremskey W, Moore T, et al.: Incisional negative pressure wound therapy after high-risk lower extremity fractures. J Orthop Trauma 26:3742, 2012

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Van Hal M, Lee J, Laudermilch D, Nwasike C, Kang J: Vancomycin powder regimen for prevention of surgical site infection in complex spine surgeries. Clin Spine Surg 30:E1062E1065, 2017

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Veeravagu A, Patil CG, Lad SP, Boakye M: Risk factors for postoperative spinal wound infections after spinal decompression and fusion surgeries. Spine (Phila Pa 1976) 34:18691872, 2009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation

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