1.5 Wound Bed Tissue Types & Periwound Assessment

Wound Bed Tissue Types & Periwound Assessment

Formulating an effective wound care treatment plan requires accurate identification of all tissue types present within the wound bed and comprehensive evaluation of the periwound skin (the area extending at least 4 cm beyond the wound margins). Tissue characterization must be documented as precise percentage estimates totaling 100% of the wound bed surface area.

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Wound Bed Tissue Types: Visual & Clinical Features

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| VIABLE TISSUES (Preserve & Protect)                                                     |
| - Granulation: Moist, firm, beefy red vascular tissue; bumpy granular surface.          |
| - Epithelialization: Fragile, shiny, thin pink/silvery translucent advancing skin.       |
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                                           vs.
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| NON-VIABLE TISSUES (Debride - *Except Stable Heel Eschar*)                              |
| - Slough: Soft, moist, stringy or mucinous yellow/tan/gray fibrinous tissue.             |
| - Eschar: Hard, dry, leathery black/brown necrotic tissue (or wet/soggy necrotic mass).|
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1. Granulation Tissue

• Healthy Granulation: Moist, firm, bright "beefy red" tissue composed of capillary loops, extracellular matrix, and fibroblasts. Represents healthy proliferation and adequate perfusion.
• Pale / Pink Granulation: Indicates low hemoglobin (anemia), poor arterial perfusion, or localized tissue edema.
• Dark Red / Purple Granulation: Indicates high bacterial bioburden, localized infection, or venous stasis congestion.
• Hypergranulation (Exuberant Granulation): Overgrowth of granulation tissue rising above the level of intact surrounding skin margins. Hypergranulative tissue is friable, bleeds easily, and physically prevents keratinocytes from migrating across the wound bed. Management: Silver nitrate cautery, topical high-potency corticosteroid ointment, or pressure dressings.

2. Slough

• Characteristics: Non-viable, avascular tissue consisting of accumulated dead leukocytes, fibrin, cellular debris, liquefying necrosis, and bacterial biofilms. Ranges in color from yellow, tan, gray, to green; may be soft, stringy, mucinous, or firmly adherent.
• Clinical Implication: Slough harbors pathogens, stimulates chronic MMP release, and prevents epithelial migration. Requires systematic removal via debridement.

3. Eschar

• Characteristics: Black, dark brown, or charcoal-colored necrotic tissue resulting from severe tissue ischemia, infarction, or burn injury. May present as dry, hard, leathery, and firmly attached, or soft, boggy, and liquefying.
• The Heel Eschar Rule (CRITICAL EXCEPTION):

Mandatory Clinical Practice Standard: Stable, dry, intact, adherent, non-erythematous, uninfected eschar on a heel or distal ischemic limb MUST NOT BE DEBRIDED. Dry intact heel eschar serves as a natural sterile biological cover. Softening or debriding stable heel eschar opens a pathway for bacterial invasion down to the calcaneus, risking osteomyelitis. The eschar must be kept dry, clean, and painted with an antiseptic such as povidone-iodine. If the heel eschar becomes boggy, fluctuating, painful, purulent, or erythematous, it is UNSTABLE/INFECTED and requires immediate surgical debridement and vascular consultation.

4. Epithelial Tissue

• Regenerated epidermal layer advancing from wound margins or hair follicle remnants (appearing as small pink "epithelial islands" within the wound bed). Epithelialization appears as delicate, shiny, translucent pink or silvery skin. Highly fragile; requires protection from adhesive tape trauma, friction, and harsh cleansers.

5. Exposed Deep Structural Structures

• Tendon: Shiny, bright white fibrous structure when viable. If exposed to air, tendons rapidly dry out (desiccate), turn dull yellow/gray, undergo necrosis, and snap. Management: MUST be kept continuously moist with hydrating hydrogels or non-adherent contact layers.
• Bone / Periosteum: Smooth, hard, off-white surface. If dry, bone turns dark brown/black and dies. Probe-to-bone testing (feeling hard bone with a sterile metallic probe) has a high positive predictive value for osteomyelitis.
• Muscle: Dark red, striated tissue that twitches when stimulated if viable; dusky gray/black and non-reactive if necrotic.

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Periwound Assessment & Pathology

Evaluating periwound skin (4 cm radius) is essential for identifying complications and preventing wound enlargement.

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Detailed Mechanics of Epibole (Rolled Edges)

When a chronic wound bed is stalled or desiccated, advancing basal epithelial cells migrate downward along the vertical wound wall. Upon contacting the viable tissue base at the bottom of the wall, physical contact triggers contact inhibition—the cell signaling process that falsely informs keratinocytes that epithelialization is complete. The epidermal edge rolls under and fuses with the wound base, creating a permanent rolled border (epibole).

   NORMAL EPITHELIAL MIGRATION                  EPIBOLE (ROLLED EDGES)
   Intact Skin ------> Keratinocytes            Intact Skin 
   ===================                          ===================\ 
                      \ Progress across                            \  Rolled Edge
                       \ Moist Bed                                  ( Keratinocytes migrate down
   ---------------------------------                                 \ & fuse with wound bed)
   [ Viable Moist Granulation Bed ]             -------------------------------------

Once epibole forms, wound contraction and epithelial advancement cease entirely. To restart healing, the clinician must re-injure the rolled margins using sharp scalpel debridement or chemical cauterization with silver nitrate sticks, exposing fresh, uninhibited basal keratinocyte edges.

Documentation Standards for Tissue & Periwound

Clinical documentation must accurately reflect both wound bed tissue proportions and periwound status to support clinical decision-making and reimbursement requirements. An exemplar clinical progress note entries includes:

"Wound bed measures 4.2 cm (L) x 3.1 cm (W) x 0.8 cm (D) at sacrum. Tissue composition: 70% beefy red granulation tissue, 30% soft yellow slough firmly adherent at 12:00 to 3:00. No eschar or exposed bone/tendon. Exudate: Moderate serosanguineous. Periwound: 1.5 cm zone of maceration at inferior margin (6:00); non-blanchable erythema extending 3 cm superiorly. Margins: Epibole noted from 9:00 to 11:00. Action: Sharp debridement of slough and epibolic edges performed; applied calcium alginate dressing covered with border foam."$