The Sandwich Technique for Quick and Efficient Application of Negative Pressure Wound Therapy to the Feet and Hands: A Case Report

NPWT has been widely used for more than 25 years, after Louis C. Argenta and Michael J. Morkywas invented the first NPWT device known as VAC in the mid-1990s.¹ The use of negative vacuum therapy can be traced back to the Roman era, when wounds sustained in battle were sucked directly by mouth to remove toxins. The use of ‘cupping’ is another technique developed in the 19th century to draw out fluid from a wound.² Since its creation, the NPWT device has been used on millions of patients globally and has been a major advancement in managing wounds of varying size and depth.^1-3

The literature supports the use of NPWT in the treatment of pressure injuries, traumatic wounds, partial-thickness burn wounds, and diabetic foot wounds, and as a bolster dressing for split-thickness skin grafts.^3,4 Advantages of NPWT include visible contraction of wound edges (macrostrain), decreased wound edema, removal of bacterial load and proinflammatory mediators, angiogenesis, and improved tissue perfusion.^3-6

Macrostrain promotes healing by stimulating myofibroblast differentiation, which enhances the healing process through myofibroblast involvement in the inflammatory response to injury, reduces edema by compressive force, and draws the wound edges together.^4-6 Microstrain occurs when negative pressure is initiated and the cells on the wound surface are physically pulled into the foam. This mechanical force at a cellular level stimulates the release of TGF-β1 from platelets. Fibroblasts then form collagen, which supports the cellular matrix.² The effect of the mechanical force alters the wound environment, creating perfusion changes at the wound surface (hyperperfusion in deep vessels and hypoperfusion on superficial vessels).^4-6 Microstrain also increases cellular energy, which aids in local cellular proliferation.^7,8 These effects enhance the development of granulation tissue and angiogenesis, thus hastening the healing process and eventual wound closure. NPWT may or may not include the use of instillation therapy, which has been shown to decrease the patient’s length of stay, number of operations, and time to wound closure.^9,10 Contraindications to NPWT placement include vascular insufficiency, exposed neurovascular structures, infection such as untreated osteomyelitis, and malignancy.¹⁰

Although NPWT is considered effective for a wide range of wounds,¹¹ there are complications that can arise during its use, including NPWT device failure, infection, skin necrosis, peri-wound maceration, and pain.^3,12 The NPWT device can have a loss of adequate seal using the acrylic drape, which causes extravasation of serous fluid, peri-wound maceration, and introduces new prokaryotic organisms into the otherwise recently debrided wound bed. Assuring an adequate seal is critical for NPWT to allow for macro- and microstrain to efficiently heal the wound bed.

The complex topography of the foot and hand, wound depth/configuration, digital conformation, digital circumference/size, and interdigital space present a technical challenge in obtaining a proper seal while using NPWT. Adjuncts to create a more effective seal may include the use of liquid medical adhesive (Mastisol, Eloquest Healthcare) or hydrocolloid dressings (DuoDERM Dressings, ConvaTec Group plc) between each digit or around the wound. Obtaining a consistent, reliable, and effortless seal with an occlusive drape is vital to efficient wound healing. In the current report, the authors provide a novel technique to assist clinicians in obtaining an adequate, stable NPWT seal on the foot.

Written informed consent was obtained for the publication of this case and photos. The IRB at ValleyWise Health Medical Center (formerly known as Maricopa Integrated Health System) has determined that this case report (CR2021-018) is exempt from IRB review based on Code or Federal Regulations Title 25, Part 46 – Protection of Human Subjects.

A 22-year-old female presented to the Arizona Burn Center after sustaining a grease burn (2% total body surface area) to the left foot with a central area of full-thickness burn injury surrounded by partial-thickness burns. Initially, the patient was treated conservatively and was instructed to apply silver sulfadiazine (Silvadene, Pfizer Inc) daily to the affected area with subsequent follow-up after 3 days for re-evaluation of the burn wound. When the patient returned, the skin adjacent to the wound was noted to be cellulitic, warm to the touch, and edematous, extending up the distal left leg from the infected burn wound. Therefore, the patient was admitted for intravenous antibiotics and operative management.

The day after admission, the patient underwent tangential excisional debridement of the burn eschar on the left foot (Figure 1). A silver sponge (VAC Granufoam Silver, 3M) was applied and secured with acrylic drape for the initiation of NPWT set at continuous -125 mm Hg. On postoperative day 3, the patient returned to the operating room for further excisional debridement of the wound bed using curettage, followed by an application of a split-thickness meshed autograft. The wound borders were framed with a liquid adhesive and a hydrocolloid dressing. An interface of silicone nonadherent dressing (Mepitel, Mölnlycke Health Care) was placed over the graft followed by a black sponge (VAC Granufoam Black, 3M). The sandwich technique was utilized with acrylic drapes placed on the plantar and dorsal aspects of the foot and then pressed together, forming a seal proximally against the hydrocolloid dressing, followed by the lateral edges and then distally around the foot. The NPWT dressing was utilized to bolster the skin graft (Figure 2).

The NPWT dressing was removed 3 days later, and the graft was noted to be well adhered to the wound bed. The patient was subsequently discharged and followed in the burn clinic to monitor the autograft healing (Figure 3).

Technique

Supplies required to apply NPWT dressings include the following 3M proprietary products: pressure sensor (SensaT.R.A.C. pad), drape (VAC Acrylic Drape or DERMATAC), and sponge (Granufoam dressing). Before application of NPWT, the wound should be debrided to healthy bleeding tissue with removal of the burn eschar or fibrinous exudate (Figure 4). The periwound area is then dried. Some may find it helpful to frame the periwound border with a liquid adhesive solution, such as a liquid adhesive followed by a hydrocolloid dressing, but this is not required and can be considered excessive use of materials. Furthermore, application of liquid adhesive and a hydrocolloid dressing between the toes is no longer required with the sandwich technique, as the dorsal and plantar acrylic drape supplants the need for interdigital application of those dressings. It was believed that in order to prevent NPWT seal leakage, a hydrocolloid dressing was required along the border of the wound or between the toes, but this is no longer the case. Eliminating this unnecessary step allows the operation or bedside procedure to be concluded faster. Instead, the wound bed is measured and an appropriately sized sponge is then applied over the wound bed. It is important that the sponge only cover the wound bed, as application over the epidermal skin border can lead to maceration, bruising from suction trauma, or irritation of the periwound integument.

The sandwich technique is applied by sealing the entire hand or foot within the NPWT drape. The first NPWT drape is placed on the dorsum of the foot or hand where the wound and sponge are located and applied proximal to distal. A second drape is placed on the opposite side and again placed proximal to distal, as if 2 pieces of sliced bread are being placed around the foot or hand—hence the term sandwich technique. The drapes must be applied at an equal level on the hand or foot, covering the distal aspect of the foam, to meet the opposite drape to prevent a leak. As the second drape is applied, careful attention should be given to the outer edges where the 2 drapes make contact. Using a finger on both sides of the drape, a seal is created on the medial and lateral aspects by pressing the drapes together, followed by the most distal aspect of the drape (Figure 5). Additional drapes can be added as needed to seal larger defects of the foot or hand. Redundant drape edges that have been sealed together are then trimmed (Figure 6). For adequate pressure sensor functioning, a 2.5-cm hole is cut on the dorsal part of the drape over the foam followed by the pressure sensor pad placement (Figure 7). Next, the pressure sensor tubing is connected to an NPWT device (Figure 8), and the NPWT dressing is then monitored for leaks and re-enforced as necessary.

Though NPWT can be very efficient for foot and hand wounds, there are inherent difficulties when applying NPWT dressings to these anatomic sites. Loss of an airtight seal and missed undraped areas must be addressed by the clinician. While one might expect the loss of an adequate seal due to the inter-digital web spaces, the presence of many mobile joints, and movement of the finger or toe, the sandwich technique can easily prevent this through the broad-based application of drape coverage. Concerns regarding the use of NPWT include the potential for skin maceration of the webspace or the plantar aspect of the foot after the drape is applied. This can be prevented by the application of cotton undercast padding (Webril Cotton Undercast Padding, Cardinal Health, Inc), a hydrocolloid dressing, or an antimicrobial foam dressing with silver (Mepilex Ag, Mölnlycke Health Care) as a barrier between the skin and the drape. It is important to prevent the cotton undercast padding or other products placed in the webspace from contacting the sponge, as this can cause a wicking of fluid and subsequent maceration. In previous procedures, the authors used acrylic drape with a hydrocolloid dressing between the toe or finger web spaces as part of the sealing process. This is no longer necessary, and the use of a hydrocolloid dressing and a liquid adhesive between the toes is now obviated. The acrylic drape easily sticks to itself and becomes difficult (if not impossible) to pull apart. Previously, when placed between the digits, the acrylic drape—which had been cut into thin strips—would become easily entangled due to the strength of the adhesive. If the seal would not hold and a leak was detected, the entire procedure required repeating, with no guarantee that a second application would work. In such an event, the only recourse was to apply more acrylic drape or remove the entire dressing and start over, leading to further waste of physical resources and increased provider frustration.

The proprietary drape is a low-tack, polyurethane-acrylic adhesive dressing with interspersed soft-silicone, which prevents skin stripping.^13,14 It can be readjusted when applied to the skin or when creating a seal between two opposing drapes over the foot or hand. If the drape sticks to itself, it can be pulled apart and reused, but a standard acrylic drape is irretrievable once it sticks to itself. The silicone perforated layer of the proprietary drape enables simple and easy repositioning. One limitation is that the drape should not be pulled tight over the digits, foot, or hand, as this can lead to skin blistering.^13,14 Despite that, this drape is beneficial when treating complex wounds and for decreasing the risk of skin injury.^13,14

The following case report has no specific limitations other than it is a single case report with the objective of disseminating information to the clinical specialist. While one could perform a large case series review or a randomized trial against other types of dressings with NPWT and drapes, there would be limited value other than to point out the ease of use with the “sandwich technique,” which is what is being presented here. The use of the “sandwich technique” to treat either hand or foot wounds as described in this single case report has actually been utilized on innumerable wounds for over the last 3 years. A more expansive study would not provide any additional insights.

The “sandwich technique” is an efficacious and safe approach to attain a reliable seal, reduce supply costs from over-draping, and eliminate extended surgery time for reapplication of NPWT due to loss of suction, which overall decreases clinician frustration. The technique can be achieved with wounds that require NPWT on the dorsal or plantar/dorsal side of the foot or hand, encompassing the deep webspace, or to the distal tip of single or multiple digits, which may be hard to seal due to their inherent curvature or mobility. In the authors’ experience, patients have tolerated this technique very well. Through the objective to reduce the prevalence of leaks and shorten the time required to apply NPWT, the authors believe the sandwich technique will be a helpful approach for clinicians to consider.