The Use of Custom-Made Negative Pressure Wound Therapy to Manage Acute Wound Infections: A Retrospective Outcomes Study

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Wound infection commonly results when microbes (bacteria, fungus) breach the host defenses, leading to harmful alterations in the host.¹ The infection can result from traumatic injuries, which can lead to skin breaches and contamination from external sources, or sometimes from minor injuries (eg, thorn pricks, minor cuts, or bruises), and in rare instances from nonpenetrating soft tissue injuries.² The negative effect of bacteria depends on the patient's immune system, as well as the quantity and virulence of bacteria.² The toxic metabolites produced by the bacterial infection can hamper wound healing and promote rapid tissue loss in the case of necrotizing soft tissue infection.³ This ultimately leads to a complex infected wound with tissue loss and exposed underlying vital structures such as bone, muscle, nerves, and tendons.⁴ The steps in the management of these complex infected wounds comprise optimization of the patient's physiological state, early antibiotic therapy, debridement, and wound care to control the infection followed by reconstructive procedures to achieve wound healing.⁴

NPWT traditionally has been used to assist in the healing of various wound types.⁵ It can be safely used for most acute and chronic wounds, surgical sites, burn wounds, and traumatic wounds.⁵ There is documented evidence of custom-made NPWT being used for chest wall infections, especially osteomyelitis of the sternum and mediastinal infection.^6-10 The use of custom-made NPWT in acute infected wounds is still debatable, with limited supporting evidence; however, it is not outright contraindicated. A few researchers have been against leaving the vacuum-assisted dressing in situ for a prolonged duration, as it increases the local bacterial bioburden, contributing to the worsening of infection and sepsis.¹¹ Evidence suggests that NPWT decreases local bacterial bioburden.¹² Liu et al¹² observed a significant decrease in bacterial colony counts over 8 days in rabbits with infected wounds managed with NPWT. Lo Torto et al¹³ found increased levels of daptomycin in the wounds treated with negative pressure dressings compared with wounds managed with conventional saline dressings. Further research on other antibiotics is required. Other evidence suggests the utility of NPWT in the management of acutely infected wounds.

Negative pressure dressings decrease the burden of infection and promote eventual wound healing, thereby complementing the effect of primary debridement of an infected wound.⁵ The commercially available NPWT dressings have proven to be efficacious in managing infected wounds, but their use is limited due to the cost of the dressing (7000 INR per dressing).¹⁴ Such treatment is unaffordable for patients with low income or no income; custom-made NPWT offers a viable cost-effective alternative for these patients.¹⁴

Custom-made dressings are fashioned from sterile polyurethane foam and a suction catheter placed on the wound bed and sealed with adhesive iodine drape, with the suction tubing connected to a portable or wall suction unit.^15,16 The use of wall suction for NPWT is contraindicated in the Western world, but several publications have shown equivalent results with no complications with the use of wall suction with custom-made NPWT dressings.^14-16

The current retrospective study analyzed the safety and efficacy of custom-made negative pressure dressings in the management of complex infected wounds of the lower limb.

All patients who received custom-made NPWT for acutely infected wounds at PSG Medical College Hospital, Coimbatore, India, from 2018 through 2020 were included in this retrospective study. Patients with peripheral vascular disease, chronic wounds, infected metalwork, surgical site infections, and osteomyelitis were excluded from the study. A total of 43 patients received the low-cost, custom-made NPWT for complex infected wounds of the lower limb. Patients with proven infected wounds of the lower limb of various etiologies with clinical signs of infection supported by positive culture swabs and soft tissue defects who received custom-made NPWT were included in the analysis. The data were retrieved from case notes and wound photographs.

All patients underwent a thorough assessment, with a detailed history and physical examination. Blood investigations to monitor infection markers were performed. MRI was used to determine the extent of infection in the region. Limb perfusion was assessed during physical examination by documenting distal pulses, and all patients were examined for peripheral vascular disease using arterial Doppler ultrasound. All patients were immediately started on empirical antibiotics (ie, co-amoxiclav), and after results of cultures were available, culture-specific antibiotics were started based on sensitivity patterns. The results of cultures were typically available on the third postoperative day, which is around the time the authors of the current study performed the first dressing change. All patients were treated with emergency incision and drainage of abscess or underwent debridement of the infected wounds.

Application of custom-made NPWT

The low-cost, custom-made NPWT was applied using chlorhexidine-impregnated gauze to cover the wound edges (Bactigras; Smith & Nephew) and 2 sterile pieces of polyurethane foam pad cut to match the size of the wound.^17-19 The suctioning end of the catheter was inserted between the 2 layers of foam pieces. The entire wound with foam and gauze was sealed airtight using an Ioban adhesive dressing (3M). After confirmation of a good seal on the wound, the suction catheter was connected to wall suction. The suction pressure delivered through wall suction could not be recorded, and the authors of the current manuscript did not use a pressure stabilizer in this cohort of patients. Suction was continuous after it was started, and dressings were changed every 72 hours. Three times a day, after first clamping the suction tube, the suction was switched off and disconnected from wall suction to allow patient mobilization and physical therapy in the wards. The wound was inspected at each dressing change and was debrided as necessary to remove loose slough before application of the next custom-made NPWT dressing. When persistent deep infection or purulent collection was suspected, further debridement was done, followed by application of the custom-made NPWT.

Antibiotics were stopped after the wound developed healthy granulation tissue and the results of culture swabs were negative. Wound closure was achieved with either STSG or secondary suturing. The progress of wound healing was assessed at 2- and 6-week post-discharge follow-up visits. A descriptive statistical analysis was performed, and the results were analyzed.

A total of 43 patients with infected ulcers or wounds in the lower limb were included in the analysis. The mean age of the patients was 58 years (range, 29–77 years). There were 33 male and 10 female patients.

The etiology of infection was as follows: diabetes in 53% (23 patients), posttraumatic (road traffic accident) in 35% (15 patients), and other causes in 12% (5 patients), including insect bites and thorn prick causing infected wounds following drainage of abscess or debridement for necrotizing fasciitis. Fifty-three percent of patients had type 2 diabetes, with a mean hemoglobin A1c level of 11 mmol/L and a mean blood glucose level of 15.5 mmol/L at the time treatment began. Eight patients (19%) had diabetic ketoacidosis. There were 10 smokers in the study population. The other comorbidities identified were hypertension (35%), obesity (body mass index > 30 in 25% of patients), and biologics (2 patients).

No complications were recorded. Infection resolved with custom-made NPWT dressings over a mean of 2.5 weeks (range, 1–5 weeks), after which coverage was achieved with either skin graft or secondary suturing. Five patients underwent second-look debridement due to persistent deep infection after initial debridement. The average size of the wounds was 24.5 cm² (range, 12 cm²–42 cm²). Eighteen wounds (42%) measured less than 20 cm², and 25 (58%) measured greater than or equal to 20 cm². All wounds healed beyond the second-look debridement, with no need for further wound inspections or debridement. An average of 5 custom-made NPWT dressings were required (range, 3–12 changes), with larger wounds typically requiring more time.

The most common organisms isolated were Staphylococcus aureus (60%), Pseudomonas (12%), Acinetobacter (10%), Klebsiella (4%), Proteus (7%), and Escherichia coli (7%). All patients were treated with empirical antibiotics initially, and on the third postoperative day appropriate antibiotics were given based on culture sensitivity patterns. A culture swab of the wound was obtained to exclude lingering infections before definitive management (skin graft or secondary suturing).

An STSG was performed in 27 patients (Figure 1) and secondary suturing was done in 10 patients (Figure 2). In 6 patients, the wound was allowed to heal by secondary intention. The average time to wound healing was 5 weeks (range, 3–7 weeks). There were no complications. A basic cost analysis of the custom-made NPWT showed it to be quite economical, with a cost per dressing of 750 INR.

The current study highlights the use of custom-made NPWT in the management of infected wounds. The negative pressure works on the principle of exudate removal, and it promotes healing by maintaining a healthy granulation bed. Gill et al¹⁵ published the results of 51 complex wounds managed with custom-made ("homemade") NPWT dressing fashioned from sterile foam, simple suction tubing with multiple holes, and an adhesive drape covering the wound. In that study, suction tubing was connected to wall suction to provide continuous suction at 125 mm Hg. The authors of that series achieved wound coverage in an average of 13 days, with an average of 2.9 dressing changes. There were no complications, and the homemade NPWT was found to be cost-effective.¹⁵ In a randomized controlled study of 100 patients undergoing skin grafting treated with custom-made NPWT, Mohsin et al¹⁴ reported a mean of 99.7% graft take in the NPWT group, with no patients requiring secondary procedures, compared with a mean of 88.5% graft take in patients treated with commercially available, widely used NPWT and the need for secondary coverage procedures in 6 patients in the latter group.

In the current series, there were no adverse events with the use of custom-made NPWT to manage deep infections and abscesses of the lower limbs. No flare-up of infection occurred. All wounds healed with no evidence of infection and were ready for coverage with skin grafting or secondary suturing at an average of 2.5 weeks. In a prospective review of 42 patients with deep spinal infection (with exposed dura in 30 patients), Lee et al²⁰ reported spontaneous healing in all but 5 patients after treatment with commercially available NPWT. These 5 patients required flap reconstruction. The patients in that series required an average of 2.3 surgical debridements in the operating room and a minimum 6-week course of antibiotics to achieve healing of the infection and the wound.²⁰ None of the patients in the current cohort had a flare-up of infection, and only 5 patients required a second debridement. The number of second surgical debridements is comparatively lower in the current study than in Lee et al,²⁰ likely because control of infection can be achieved faster in the lower limbs than in the spine.

A systematic review by Glass et al²¹ noted that NPWT could selectively inhibit the growth of Pseudomonas species while at the same time creating an environment that is conducive to the proliferation of S aureus species. In the current study, 60% of cultures were positive for S aureus, and as of this writing no flare-ups or sepsis secondary to NPWT dressing have occurred. The authors of the current study believe that good results can be achieved with thorough debridement followed by custom-made NPWT. These negative pressure dressings must be changed every 72 hours to prevent and/or remove any opportunistic organisms that may proliferate on the polyurethane foam.

In 1998, Fleischmann introduced the concept of NPWT with instillation, which combines the effectiveness of NPWT and periodic cleansing of the wound with the instillation of saline or antimicrobial solution.²² The procedure dwells on 3 verticals (negative pressure, irrigation, and dwell time) followed by drainage, which promotes wound healing by reducing bacterial concentration via periodic cleansing of the wound and also promotes healthy granulation.²³ In their prospective analysis of complex infected wounds managed with standard NPWT vs NPWT with instillation, Goss et al²⁴ found a significant reduction in bacterial bioburden with NPWT with instillation. In that study, with standard NPWT there was an increase in bioburden over 7 days. A systematic review by Gabriel et al²⁵ demonstrated that patients treated with NPWT with instillation required fewer surgical debridement procedures and had reduced bacterial counts; as a result, these patients achieved earlier wound closure than patients treated with standard NPWT. The evidence concerning NPWT with instillation appears promising; however, there is no published literature on the use of custom-made NPWT dressings with instillation.

In a case series, Jones et al³ described 20 cases of infected wounds managed with NPWT dressings and reported adequate healing in 19 patients, with no complications. They also noted an average 29% reduction in wound size with the use of NPWT. In a study on NPWT dressings vs conventional dressings for S aureus-infected wounds in rabbits, Li et al²⁶ reported a significant decrease in bacterial bioburden and biofilm formation if NPWT was applied early. In the current case series, most patients had deep or extensive infections, yet only 5 patients (12%) required second-look debridement in the operating room. Applying a custom-made NPWT early after debridement of the infection could markedly reduce the bacterial load and promote quicker wound healing. The role of thorough debridement to eradicate any infection cannot be understated, and debridement promotes wound healing. Moog et al²⁷ noted a decrease in bacterial load following debridement in up to 60% of patients in their study. Furthermore, they obtained a negative culture result in these patients within 4 debridements.²⁷ In the current study, before definitive management of the wound (skin grafting or secondary suturing), a negative culture result was obtained in all patients, with only 5 patients requiring a second debridement. It is worth noting that NPWT alone does not solve the issue of an infected wound; rather, it complements thorough debridement and aids in the healing of infected wounds.

The downside with the custom-made NPWT used in the current study is that patients had to remain hospitalized until definite closure was achieved. Patient mobilization is possible with the custom-made NPWT; the suction catheter is clamped to enable this 3 times a day. Mobilization and physiotherapy are quite important in these patients to prevent venous stasis. As of this writing, no cases of deep vein thrombosis have occurred in any of the patients treated with the custom-made NPWT described in the current study.

The main limitation of the current study is that it lacks a control group. Additionally, this is a retrospective study, so it was not possible to group patients homogenously, and there was significant overlap in patient/treatment groups. Finally, the treatment itself is a limitation from a patient perspective because inpatient care is necessary for the duration of NPWT until definitive wound closure is achieved.

The findings of the current study suggest that the custom-made NPWT is a good adjunct to debridement in the management of acutely infected wounds, because it prevents further complications, markedly reduces the number of operating room visits and duration of stay, and, most importantly, is economical.

Authors: Chandan Noel Vincent, MBBS, MS-Ortho, MECS-Ed¹; Aakash Sethuraman Venkatesan, MBBS, D-Ortho, DNB-Ortho, MRCS²; Dinakar Rai, MBBS, MS-Ortho³; Arvind Kumar Salem Muthuswamy, MBBS, MS-Ortho³ 

Affiliations: ¹Manchester Royal Infirmary Hospital, Orthopaedics, Manchester, England; ²NHS Wales Aneurin Bevan University Health Board, Caerleon, Newport, Wales; ³PSG Institute of Medical Sciences and Research, Peelamedu, Coimbatore, India

Disclosure: The authors disclose no financial or other conflicts of interest.

Ethical Approval: The study was approved by the Institutional Ethics Committee-PSG IMSR, Peelamedu, Coimbatore, India. 

Correspondence: Chandan Noel Vincent, MBBS, MS-Ortho, MECS-Ed; Manchester Royal Infirmary, Orthopaedics, Oxford Road, Manchester, England M139WL; chandannoel@gmail.com

Manuscript Accepted: January 22, 2024