7.4 Pressure Injury Staging & Periwound Skin Assessment

7.4 Pressure Injury Staging & Periwound Skin Assessment

Clinical Pearl: Diabetic foot ulcers are graded by the Wagner and University of Texas systems; pressure injuries are staged, and the two vocabularies are not interchangeable. This section covers the pressure injury staging system the blueprint names, the one staging error international consensus explicitly forbids, and the periwound assessment that frequently reveals more about a wound's trajectory than the wound bed itself.

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The NPUAP/EPUAP Pressure Injury Staging System

A naming note you must not miss on exam day: the CFCN blueprint names the National Pressure Ulcer Advisory Panel (NPUAP), because that was the organization's name when the 2019 role delineation study was written. In 2019 the organization renamed itself the National Pressure Injury Advisory Panel (NPIAP) to match the 2016 shift from "pressure ulcer" to "pressure injury." NPUAP and NPIAP refer to the same body and the same staging system; a question stem may use either name, and neither is a distractor.

The National Pressure Ulcer Advisory Panel (now NPIAP), European Pressure Ulcer Advisory Panel (EPUAP), and Pan Pacific Pressure Injury Alliance (PPPIA) unified guidelines define a pressure injury as localized damage to the skin and underlying soft tissue, usually over a bony prominence or related to a medical or other device. Pressure injuries are staged strictly according to the deepest anatomical tissue layer exposed or damaged.

+-------------------------------------------------------------------------+
|                    PRESSURE INJURY STAGING SPECTRUM                     |
+-------------------------------------------------------------------------+
| Stage 1 | Non-blanchable erythema of INTACT skin; localized redness     |
+---------+---------------------------------------------------------------+
| Stage 2 | Partial-thickness loss of dermis; shallow pink/red wound bed  |
|         | OR intact / ruptured serum-filled blister; NO adipose visible |
+---------+---------------------------------------------------------------+
| Stage 3 | Full-thickness loss of skin; ADIPOSE (subQ fat) is visible;   |
|         | granulation, slough, epibole present; bone/tendon NOT exposed |
+---------+---------------------------------------------------------------+
| Stage 4 | Full-thickness skin and tissue loss; EXPOSED or directly      |
|         | palpable BONE, TENDON, MUSCLE, FASCIA, or LIGAMENT            |
+---------+---------------------------------------------------------------+
| Unstage | Full-thickness skin & tissue loss where the TRUE BASE is      |
|  -able  | completely OBSCURED by slough (yellow/tan) or eschar (black)  |
+---------+---------------------------------------------------------------+
|  DTPI   | Intact or non-intact skin with persistent, non-blanchable,    |
|         | deep RED, MAROON, or PURPLE discoloration; or blood blister   |
+-------------------------------------------------------------------------+

Detailed Stage Criteria

1. Stage 1 Pressure Injury: Intact skin with a localized area of non-blanchable erythema. Blanching is assessed by applying gentle finger pressure for 3 seconds; if the redness fails to blanch (turn white/pale), microvascular capillary damage is present. In darkly pigmented skin, erythema may not be visually apparent; clinicians must assess for localized differences in skin temperature (warmth or coolness), tissue firmness (induration or bogginess), and pain compared to adjacent tissue.
2. Stage 2 Pressure Injury: Partial-thickness loss of skin with exposed dermis. The wound bed is viable, shallow, pink or red, and moist. Stage 2 also encompasses an intact or ruptured serum-filled blister. Exclusions: Stage 2 must never be used to describe moisture-associated skin damage (MASD), intertrigo, medical adhesive-related skin injury (MARSI), or skin tears. Adipose tissue, granulation tissue, slough, and eschar are never present in a Stage 2 injury.
3. Stage 3 Pressure Injury: Full-thickness loss of skin in which subcutaneous adipose tissue is visible within the ulcer crater. Granulation tissue, epibole (rolled wound edges), undermining, and tunneling may be present. Slough or eschar may be visible, but only if they do not obscure the true depth of the wound base. Anatomical Note: On the heel or lateral malleolus where subcutaneous fat is sparse, a Stage 3 injury may remain anatomically shallow.
4. Stage 4 Pressure Injury: Full-thickness skin and tissue loss with directly exposed or palpable fascia, muscle, tendon, ligament, cartilage, or bone. Slough, eschar, epibole, undermining, and tunneling are frequently present. The presence of exposed bone or tendon places the patient at imminent risk for acute osteomyelitis, tenosynovitis, and septic arthritis.
5. Unstageable Pressure Injury: Full-thickness skin and tissue loss in which the actual extent of tissue destruction at the base of the wound is completely obscured by slough (yellow, tan, gray, green, or brown) or eschar (tan, brown, or black). True depth cannot be determined until sufficient slough or eschar is removed to reveal the wound base. Once debrided, the wound will be revealed as either a Stage 3 or Stage 4 injury.
6. Deep Tissue Pressure Injury (DTPI): Intact or non-intact skin exhibiting localized, persistent, non-blanchable deep red, maroon, or purple discoloration, or an intact or ruptured blood-filled blister. DTPI results from intense, prolonged mechanical pressure and shear forces acting at the deep bone-muscle interface, causing deep soft-tissue necrosis that subsequently blooms outward toward the skin surface. DTPIs can rapidly evolve into extensive Stage 3 or Stage 4 full-thickness injuries, even with optimal treatment.

Two Non-Negotiable Pressure Injury Documentation Rules

• RULE 1: Prohibition of "Reverse Staging" (Back-Staging):
  Pressure injuries are classified strictly according to the deepest anatomical structure involved at their maximum severity. A pressure injury is NEVER down-staged or reverse-staged as it heals. A Stage 4 pressure injury that granulates and closes does not become a Stage 3, then a Stage 2, then a Stage 1. Why? The body heals full-thickness defects through granulation and scar formation (fibrosis); lost muscle, subcutaneous adipose, and dermal rete pegs are never regenerated. The correct clinical documentation is: "Healing Stage 4 Pressure Injury" or "Closed/Resolved Stage 4 Pressure Injury."
• RULE 2: Etiological Exclusivity:
  Pressure injury staging systems must NEVER be applied to non-pressure ulcers. It is medically and legally incorrect to document a "Stage 3 diabetic foot ulcer" or a "Stage 2 venous leg ulcer." Diabetic foot ulcers must be classified using the Wagner or University of Texas systems, and venous ulcers are documented by anatomical description, depth of tissue loss (partial- or full-thickness), and CEAP clinical classification.

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Periwound Skin and Wound Margin Assessment

A thorough assessment extends beyond the wound bed to encompass the wound margins and the periwound skin envelope (defined as the skin within a 4-centimeter radius surrounding the ulcer borders). Pathological changes in the periwound provide critical clues regarding exudate management, invasive infection, and cellular chronicity.

+-------------------------------------------------------------------------+
|                    PERIWOUND & WOUND MARGIN ASSESSMENT                 |
+-------------------------------------------------------------------------+
|                                                                         |
|    [ Normal Periwound Skin (0 to 4 cm zone) ]                          |
|           |                                                             |
|           +--> MACERATION: White, waterlogged, sodden tissue; high MMPs|
|           +--> INDURATION: Palpable firmness; deep cellulitis/abscess  |
|           +--> ERYTHEMA: Spreading redness >2 cm; heat; infection      |
|           +--> DENUDATION: Stripped stratum corneum; MASD or MARSI     |
|           +--> FLUCTUANCE: Boggy fluid wave; trapped purulence/pus     |
|                                                                         |
|    [ Wound Margins / Edges ]                                            |
|           |                                                             |
|           +--> EPIBOLE: Rolled, inverted epithelial edges; stops migration
|           +--> UNDERMINING: Tissue destruction beneath intact skin edge |
|           +--> TUNNELING / SINUS: Narrow channel into deep structures   |
|                                                                         |
|    [ Deep Bone Evaluation ]                                             |
|           +--> PROBE-TO-BONE (PTB): Rigid, metallic contact -> OSTEO   |
|                                                                         |
+-------------------------------------------------------------------------+

Clinical Periwound Indicators

1. Maceration: Softened, soggy, opaque white periwound epidermis resulting from prolonged contact with excessive wound exudate or trapped sweat. Macerated skin possesses an alkaline pH and contains high concentrations of destructive matrix metalloproteinases (MMPs) that lyse intercellular adhesion proteins, causing epidermal breakdown and rapid ulcer enlargement.
2. Induration: An abnormal, palpable firmness and loss of elasticity of the periwound skin compared to surrounding healthy tissues. Induration extending > 2 cm beyond the wound margin is a cardinal sign of active soft-tissue cellulitis or deep fascial phlegmon.
3. Erythema: Dermal redness surrounding the ulcer. Clinicians must distinguish localized periwound inflammatory hyperemia (< 1–2 cm, mild warmth, physiological wound healing) from spreading bacterial cellulitis (erythema extending > 2 cm from the margin, accompanied by ascending warmth, edema, severe tenderness, and systemic signs).
4. Denudation and Excoriation: Loss of the superficial epidermis, presenting as raw, glistening, weeping red surfaces. Arises from chemical digestive erosion (corrosive exudate) or mechanical adhesive stripping (Medical Adhesive-Related Skin Injury / MARSI).
5. Fluctuance: A palpable, boggy, fluid-wave sensation felt when pressing gently on periwound tissues. Fluctuance indicates an underlying, encapsulated collection of purulent exudate or hematoma (abscess) requiring urgent surgical drainage.
6. Epibole (Rolled Wound Edges): A clinical condition in which migrating keratinocytes at the wound margin curl downward into the ulcer crater and touch the underlying wound base. Because keratinocytes cease migration upon contacting a basement membrane or viable tissue (contact inhibition), epithelial advancement freezes, rendering the wound chronic and stalled. Overcoming epibole requires conservative sharp paring or chemical cauterization with silver nitrate to re-open the epithelial edge.
7. Undermining and Tunneling:
   • Undermining: Destruction of subcutaneous tissue extending horizontally beneath the intact epidermal and dermal margin along the perimeter of the ulcer.
   • Tunneling (Sinus Tract): A narrow, linear channel of tissue destruction extending from any point of the wound bed in a single direction into deeper subcutaneous or fascial layers.
   • Documentation Standard: Undermining and tunneling must always be measured in centimeters and documented according to a standard clock-face orientation, with 12:00 o'clock oriented toward the patient's head and 6:00 o'clock oriented toward the patient's feet.
8. Bedside Probe-to-Bone (PTB) Test: In any open neuropathic or diabetic foot ulcer, the foot care nurse or clinician inserts a sterile, blunt metallic probe gently into the deepest portion of the wound. If the probe encounters a hard, gritty, rigid, unyielding surface, the test is considered positive. In high-risk populations, a positive PTB test exhibits a positive predictive value of > 89% for underlying osteomyelitis, mandating urgent radiographic evaluation and infectious disease referral.

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Wound Classification & Staging Systems Reference Matrix