6.2 TIME Framework & Wound Bed Preparation
Key Takeaways
- The TIME framework (Tissue, Infection/Inflammation, Moisture balance, Edge of wound) provides a systematic, evidence-based approach to wound bed preparation.
- Tissue management focuses on removing non-viable, necrotic material and slough through selective or non-selective debridement modalities.
- Infection and inflammation control involves managing bioburden across the contamination-to-systemic infection continuum using the NERDS and STONEES clinical criteria.
- Moisture balance prevents cellular desiccation while protecting periwound skin from proteolytic exudate maceration.
- Edge management addresses stalled epidermal margins, senescent keratinocytes, and epibole (rolled edges) by refreshing wound perimeters and applying matrix therapies.
TIME Framework & Wound Bed Preparation
Wound Bed Preparation (WBP) is a structured, clinical management concept introduced by Falanga, Schultz, and colleagues to overcome molecular and cellular barriers to healing in chronic wounds. Chronic wounds—such as pressure injuries, diabetic foot ulcers, and venous leg ulcers—frequently become trapped in a self-perpetuating inflammatory loop characterized by high protease activity, degraded extracellular matrix (ECM), senescent fibroblasts, and persistent microbial bioburden. The TIME framework provides clinicians with a standardized, systematic approach to evaluate and optimize the wound environment.
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| T - TISSUE MANAGEMENT |
| Non-viable, necrotic, or slough tissue -> Selective/Non-selective|
| debridement to expose viable, vascularized wound bed. |
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v
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| I - INFECTION / INFLAMMATION CONTROL |
| Bioburden continuum & persistent inflammation -> Antimicrobials, |
| MMP regulation, and biofilm management strategies. |
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v
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| M - MOISTURE BALANCE MANAGEMENT |
| Desiccation vs. Exudate Maceration -> Absorbent or hydrating |
| dressings to maintain optimal fluid-balanced environment. |
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v
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| E - EDGE OF WOUND / EPIDERMAL ADVANCEMENT |
| Stalled edges, epibole, senescent cells -> Debridement of margin, |
| advanced biologics, collagen/ECM constructs. |
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1. Tissue Management (T)
The presence of non-viable tissue (necrotic eschar, yellow fibrinous slough, devitalized fascia, or foreign debris) impairs healing by acting as a physical barrier to keratinocyte migration, providing a nutrient-rich medium for bacterial proliferation, and stimulating continuous neutrophilic recruitment.
Clinical Assessment & Objectives
Clinicians evaluate tissue type, color, attachment, and volume within the wound bed. The primary goal of Tissue management is the complete removal of non-viable material to create a clean, well-vascularized, granular wound bed capable of supporting tissue regeneration.
| Debridement Modality | Mechanism of Action | Clinical Indications | Contraindications / Precautions |
|---|---|---|---|
| Sharp / Surgical | Scalpel, curette, or scissors physically excise devitalized tissue | Rapid removal of thick eschar, gross necrotic tissue, or urgent infection | Uncorrected bleeding disorders, severe arterial insufficiency (ABI < 0.5) |
| Enzymatic | Exogenous collagenase (clostridial collagenase) digests native collagen anchors | Slough or eschar in patients intolerant of sharp debridement | Co-application with heavy metals (silver, mercury) which deactivate enzyme |
| Autolytic | Endogenous lysosomal enzymes digest necrotic tissue under moisture-retentive dressings | Painless management of mild-to-moderate slough in non-infected wounds | Active wound infection or rapidly spreading cellulitis (too slow) |
| Mechanical | Wet-to-dry dressings, wound irrigation, or monofilament pads physically detach tissue | Removal of loose debris or non-adherent slough | Wet-to-dry is non-selective, painful, and damages newly formed granulation tissue |
| Biological (Maggots) | Lucilia sericata larvae secrete proteolytic enzymes and ingest necrotic tissue | Intractable slough/necrotic wounds, osteomyelitis, MRSA colonization | Near major exposed blood vessels, severe ischemia, patient aversion |
2. Infection & Inflammation Control (I)
Microbial bioburden exists along a continuous spectrum ranging from benign contamination to life-threatening systemic sepsis. Distinguishing local infection from systemic infection guides appropriate antimicrobial stewardship.
The Bioburden Continuum
- Contamination: Transient presence of non-replicating organisms on the wound surface without host tissue injury or immune response.
- Colonization: Replicating organisms adhere to the wound bed without invading host tissue or inducing a clinical immune response.
- Local Infection / Subtle Bioburden: Replicating organisms invade superficial wound tissue, eliciting a localized host response. Clinical signs are characterized by the NERDS mnemonic:
- N: Non-healing wound despite optimal therapy
- E: Exudate increase (change in volume or character)
- R: Red, friable, easily bleeding granulation tissue
- D: Debris or slough accumulation on the wound surface
- S: Smell or foul odor
- Systemic / Deep Infection: Microorganisms invade deep tissue, fascia, or bone, causing systemic illness. Clinical signs are characterized by the STONEES mnemonic:
- S: Size increasing or breakdown of newly healed tissue
- T: Temperature elevation (local warmth > 3°F or systemic fever)
- O: Os (exposed bone or positive probe-to-bone test)
- N: New areas of breakdown / satellite lesions
- E: Exudate, Erythema, Edema expanding > 2 cm from wound edge
- S: Smell / severe malodor
Therapeutic Approach
- Local Infection (NERDS): Targeted with topical antimicrobial agents (cadexomer iodine, silver hydrofiber, medical-grade honey, PHMB) to avoid unnecessary systemic antibiotic exposure.
- Deep / Systemic Infection (STONEES): Requires systemic antimicrobial therapy combined with urgent surgical debridement or abscess drainage.
3. Moisture Balance (M)
A moist wound bed optimizes cellular migration, accelerates re-epithelialization, and facilitates endogenous autolytic debridement. However, an imbalance in exudate levels creates significant clinical complications:
- Desiccation (Too Dry): Cell drying, formation of hard crusts/eschar, death of superficial keratinocytes and fibroblasts, and delayed cell migration across the wound bed.
- Maceration (Too Wet): Excessive exudate containing high concentrations of active proteases (MMPs) and inflammatory cytokines breaks down periwound skin, leading to epidermal stripping, pain, and expansion of wound dimensions.
Clinicians achieve moisture balance by selecting dressings based on exudate volume: hydrogels and hydrocolloids donate moisture to dry wounds, whereas alginates, hydrofibers, foams, and superabsorbents absorb excess exudate in heavily draining wounds.
4. Edge Management (E)
The wound edge (epidermal margin) reflects the functional capacity of keratinocytes to migrate across the granular wound bed. In chronic wounds, epidermal advancement frequently stalls due to cellular senescence, phenotypically altered keratinocytes, or structural edge abnormalities.
Pathological Edge Presentations
- Epibole (Rolled Edges): Keratinocytes at the wound margin migrate downward along the vertical wound wall instead of horizontally across the wound bed. Once keratinocytes contact the basement membrane at the base of the wall, contact inhibition halts further migration, sealing the edge while leaving the wound center open.
- Hyperkeratosis / Callus: Thickened stratum corneum surrounding neuropathic foot ulcers that exerts high mechanical shear forces on underlying tissue.
- Senescent Margins: Keratinocytes at the periphery become non-responsive to endogenous growth factors (such as EGF and TGF-alpha), remaining stuck in the G0 phase of the cell cycle.
Management of Stalled Margins
- Debridement of the Margin: Sharp excision or curettage of epibole or calloused edges ("re-heading" the wound) converts non-responsive, senescent margins into fresh, active edges capable of horizontal migration.
- Advanced Biologics & Matrices: Application of cellular and tissue-based products (CTPs), bioengineered skin substitutes, or collagen-ORC (oxidized regenerated cellulose) dressings to neutralize excess MMPs and provide a structural scaffold for keratinocyte migration.
A patient presents with a chronic diabetic foot ulcer displaying rolled, rounded wound margins where the epidermal layer has migrated downward and fused with the wound bed base. What is this clinical finding, and what is the primary intervention required?
According to the NERDS and STONEES clinical assessment framework for bioburden, which set of clinical features indicates deep or systemic infection requiring systemic antimicrobial therapy?
Why is clostridial collagenase ointment contraindicated for co-application with silver-containing topical dressings during Tissue (T) management?