Residency · Residency · Plastic Surgery

Negative Pressure Wound Therapy and Advanced Wound Care

Overview

Negative pressure wound therapy (NPWT) has transformed wound management since its introduction in the 1990s. Combined with dermal substitutes and staged reconstruction, NPWT enables treatment of complex wounds that previously required immediate flap coverage or prolonged secondary healing. ---

Negative Pressure Wound Therapy (NPWT)

Mechanism of Action

Macro-deformation: mechanical collapse of the foam draws wound edges together, reducing wound size. Micro-deformation: cellular-level mechanical stress on wound bed cells stimulates proliferation and granulation (mechanotransduction). Fluid removal: removes excess interstitial edema and wound exudate containing inhibitory MMPs, pro-inflammatory cytokines, and bacterial products. Wound environment modification: reduces bacterial colonization, maintains moist wound environment.

Improved perfusion: increases blood flow to wound margins (zone 1) while compressing the wound center; effect is pressure-dependent.

Components of a Standard NPWT System

Wound filler: reticulated open-cell polyurethane foam (black, 400-600 micron pore size) or polyvinyl alcohol foam (white, denser, less adherent) or gauze-based systems. Adhesive drape: transparent occlusive barrier maintaining seal. Tubing and canister: connects wound to suction pump. Pump unit: programmable for continuous or intermittent suction.

Pressure Settings

Standard: -125 mmHg continuous (most studied setting). Low-intensity: -75 mmHg (for sensitive areas, skin grafts, painful wounds). Intermittent therapy: 5 minutes on / 2 minutes off; may stimulate more granulation tissue but is less well tolerated due to discomfort. Higher pressures (beyond -200 mmHg) do not improve outcomes and may impair perfusion.

Foam Selection

Dressing Changes

Every 48-72 hours for foam-based systems (tissue ingrowth becomes problematic beyond 72 hours). Non-adherent contact layer (Adaptic, Mepitel) placed between wound bed and foam protects delicate structures. Bridge technique: foam can be extended from the wound to a remote location for suction connection.

<image>Exploded-view medical illustration of a negative pressure wound therapy system applied to an open wound on the lower leg, showing each layer: wound bed with granulation tissue at the base, optional non-adherent contact layer (Mepitel) over exposed tendon, black polyurethane foam filling the wound cavity, transparent adhesive drape sealing over the foam and surrounding skin, tubing connected to the drape through a tracked pad, leading to the portable suction unit with collection canister. Arrows indicate the direction of fluid flow from wound to canister.</image>

Indications for NPWT

Acute Wounds

Open fractures (temporizing before definitive soft tissue coverage). Traumatic tissue loss. Surgical wound dehiscence. Fasciotomy wounds (assists primary closure).

Chronic Wounds

Diabetic foot ulcers (Level I evidence). Pressure injuries (wound bed preparation for surgical closure). Venous stasis ulcers (adjunct to compression).

Surgical Applications

Skin graft bolster: NPWT over split-thickness skin grafts improves take rate (uniform compression, fluid evacuation, graft immobilization). Over closed incisions (ciNPWT): prophylactic use over high-risk surgical incisions (e.g., groin, abdomen, sternal wounds) reduces surgical site infection and dehiscence. Temporary abdominal closure: open abdomen management with ABThera or Barker vacuum pack. Sternal wound infections: bridge therapy before definitive flap coverage.

Special Modifications

NPWT with instillation (NPWTi-d): intermittent delivery of antiseptic (Dakin solution, betadine) or saline followed by suction; enhances debridement and reduces biofilm. NPWT with simultaneous irrigation (Veraflo). ---

Contraindications

Absolute

Malignancy within the wound bed (may promote tumor growth). Untreated osteomyelitis (requires debridement and antibiotics first). Non-enteric and unexplored fistulae. Necrotic tissue with eschar (requires debridement before NPWT application).

Relative

Exposed blood vessels, vascular anastomoses, or bypass grafts (hemorrhage risk -- protect with non-adherent barrier or white foam). Exposed nerves (protect with non-adherent layer). Active hemorrhage. Patients on anticoagulation (increased hemorrhage risk). Difficult-to-seal wound locations (perineum, irregular surfaces). ---

Dermal Substitutes and Staged Reconstruction

Integra Bilayer Matrix Wound Dressing

Composition: inner layer of bovine collagen and chondroitin-6-sulfate glycosaminoglycan; outer silicone layer acting as temporary epidermis. Mechanism: provides a scaffold for neodermis formation; host fibroblasts and endothelial cells infiltrate over 2-3 weeks. Application technique: place dermal side on prepared wound bed (well-vascularized, non-infected); secure with sutures/staples; bolster or NPWT application. Second stage: silicone layer removed at 2-3 weeks once neodermis is mature (vascularized, pink); ultra-thin STSG applied. Combined with NPWT: NPWT over Integra improves integration rates and reduces time to second stage.

MatriDerm

Single-layer bovine collagen-elastin matrix. Applied in a single stage simultaneously with skin graft. No silicone layer; one-step procedure. Suitable for partial and full-thickness defects.

NovoSorb Biodegradable Temporizing Matrix (BTM)

Synthetic biodegradable polyurethane foam sealed with a temporary polyurethane film. Integrates over 2-4 weeks, then film removed and STSG applied. Advantages: synthetic (no animal-derived products), cost-effective, consistent quality.

AlloDerm and Other Acellular Dermal Matrices

Processed cadaveric or xenograft dermis. Used as dermal template in burns, abdominal wall reconstruction, breast reconstruction. Single-stage application with skin graft is possible but may have variable take rates. ---

Staged Reconstruction Algorithm

Stage 1: Wound Bed Preparation

Serial debridement of necrotic and infected tissue. Initiate NPWT with or without instillation. Optimize systemic factors (nutrition, glucose control, vascular status). Goal: clean, well-vascularized wound bed with granulation tissue.

Stage 2: Dermal Substitute Application

Apply Integra, BTM, or other dermal template. NPWT overlay to improve scaffold integration. Wait 2-4 weeks for neodermis maturation.

Stage 3: Definitive Coverage

Thin STSG (0.006-0.008 inch) applied over neodermis. NPWT as graft bolster for 5-7 days. Progressive wound care and rehabilitation.

When to Skip to Free Flap

Exposed critical structures (bone without periosteum, tendon without paratenon, hardware, vessels). Large defects where skin grafting alone provides inadequate coverage. Irradiated wound beds with poor vascularity. Functional requirements (weight-bearing surfaces, joint coverage).

<image>Flowchart-style medical illustration showing the staged reconstruction approach for a complex wound. Panel 1: contaminated wound with necrotic tissue undergoing serial debridement. Panel 2: NPWT application with clean granulating wound bed. Panel 3: Integra bilayer matrix application with NPWT overlay. Panel 4: removal of silicone layer showing vascularized neodermis. Panel 5: thin split-thickness skin graft application with NPWT bolster. Final result showing healed wound with good contour.</image>

Other Advanced Wound Care Modalities

Hyperbaric Oxygen Therapy (HBO)

Systemic delivery of 100% O2 at 2.0-2.4 ATA for 90-minute sessions. Increases dissolved plasma oxygen, promotes angiogenesis, enhances neutrophil killing. Best evidence: diabetic foot ulcers, radiation injury, refractory osteomyelitis, compromised grafts/flaps. Typically 20-40 sessions; Marx protocol for osteoradionecrosis (20 pre-op + 10 post-op).

Topical Oxygen Therapy

Continuous or intermittent delivery of oxygen directly to the wound surface. Emerging evidence; less robust than HBO data. Does not increase systemic oxygen delivery.

Growth Factor Therapy

Becaplermin (Regranex): recombinant PDGF-BB; FDA-approved for neuropathic diabetic ulcers. Applied daily to debrided wound bed. Modest improvement in healing rates (approximately 15% increase over placebo).

Electrical Stimulation

Level I evidence for pressure injuries (EPUAP/NPIAP guidelines). Mimics endogenous bioelectric wound currents. Promotes cellular migration, proliferation, and angiogenesis.

Enzymatic Debridement

Collagenase (Santyl): selective enzymatic debridement of necrotic tissue. Does not harm viable tissue. Slower than sharp debridement but useful when operative debridement is not feasible.

Cellular and Tissue-Based Products

Dehydrated human amnion/chorion membrane (dHACM, EpiFix): contains growth factors, anti-inflammatory cytokines. Growing evidence for diabetic ulcers and chronic wounds. Single application or repeated application depending on product. ---

Evidence Base for NPWT

Level I Evidence

Diabetic foot ulcers: improved healing rates with NPWT vs. standard moist wound care (Blume et al., 2008). Open fractures: reduced infection rates with NPWT vs. standard dressings (Stannard et al., 2012). Closed-incision NPWT: reduced surgical site infection in high-risk incisions (multiple RCTs and meta-analyses).

Level II-III Evidence

Skin graft bolster: improved take rates (multiple cohort studies). Sternal wound infections: effective temporizing measure (case series). NPWT with instillation: improved wound bioburden reduction (comparative studies). ---

Clinical Pearls

NPWT is a bridge therapy, not a destination -- the goal is to prepare the wound bed for definitive surgical closure, not to heal the wound by secondary intention. Change foam dressings every 48-72 hours; longer intervals lead to tissue ingrowth into the foam, causing pain and bleeding at removal. Always place a non-adherent contact layer over exposed tendons, nerves, or vessels before applying foam to prevent desiccation injury or hemorrhage. NPWT over skin grafts improves take rates by providing uniform pressure, removing fluid, and immobilizing the graft -- standard settings of -75 to -125 mmHg are appropriate.

Closed-incision NPWT is cost-effective for high-risk surgical closures (obese patients, repeat operations, irradiated tissue, groin incisions). Integra combined with NPWT has expanded the indications for dermal substitutes to include contaminated and complex wounds that previously required immediate flap coverage. NPWT with instillation (NPWTi-d) is particularly useful for heavily contaminated wounds with biofilm -- the instilled solution disrupts biofilm mechanically and chemically. Always rule out malignancy in a chronic wound that fails to heal despite appropriate management (Marjolin ulcer). ---.

References

• Argenta LC, Morykwas MJ. Vacuum-assisted closure: a new method for wound control and treatment. Ann Plast Surg. 1997;38(6):563-576.
• Morykwas MJ, Argenta LC, Shelton-Brown EI, McGuirt W. Vacuum-assisted closure: a new method for wound control and treatment: animal studies and basic foundation. Ann Plast Surg. 1997;38(6):553-562.
• Blume PA, Walters J, Payne W, et al. Comparison of negative pressure wound therapy using vacuum-assisted closure with advanced moist wound therapy in the treatment of diabetic foot ulcers. Diabetes Care. 2008;31(4):631-636.
• Stannard JP, Volgas DA, McGwin G, et al. Incisional negative pressure wound therapy after high-risk lower extremity fractures. J Orthop Trauma. 2012;26(1):37-42.
• Dumville JC, Land L, Evans D, Peinemann F. Negative pressure wound therapy for treating leg ulcers. Cochrane Database Syst Rev. 2015;7:CD011354.
• Yannas IV, Burke JF, Orgill DP, Skrabut EM. Wound tissue can utilize a polymeric template to synthesize a functional extension of skin. Science. 1982;215(4529):174-176.

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