A wound is a disruption of the normal anatomical structure and function of tissue, typically the skin. Wounds can result from various causes, including physical trauma, surgical procedures, thermal injury, chemical exposure, or underlying medical conditions. The severity and characteristics of a wound depend on the mechanism of injury, its depth, location, and the presence of contamination.

Classification of Wounds

Wounds can be classified based on several criteria, which helps in understanding their nature and guiding management.

Classification by Cause:

• Mechanical Wounds: Caused by physical force.

  • Incised Wound: Clean cut with sharp edges (e.g., surgical incision, knife cut).

  • Laceration: Irregular tear of tissue with jagged edges (e.g., blunt trauma).

  • Abrasion: Superficial scraping of the skin (e.g., friction burn, scrape).

  • Contusion: Bruise; injury to underlying tissue without breaking the skin (e.g., blunt force impact).

  • Puncture Wound: Caused by a sharp object piercing the skin (e.g., nail, needle).

  • Avulsion: Tearing away of tissue or a body part.

  • Crush Injury: Tissue damage caused by prolonged pressure or compression.

• Thermal Wounds: Caused by heat or cold (e.g., burns, frostbite).

• Chemical Wounds: Caused by corrosive substances (e.g., acid or alkali burns).

• Electrical Wounds: Caused by the passage of electrical current through the body.

• Radiation Wounds: Caused by exposure to radiation (e.g., radiation therapy side effects, sunburn).

• Ischemic Wounds: Caused by insufficient blood supply to the tissue (e.g., pressure ulcers, arterial ulcers).

• Chronic Wounds: Wounds that fail to heal in an orderly and timely manner (e.g., venous ulcers, diabetic ulcers, pressure ulcers).

Classification by Depth:

• Superficial: Involves only the epidermis (e.g., abrasion, first-degree burn).

• Partial-Thickness: Extends through the epidermis and into the dermis (e.g., blisters, second-degree burn).

• Full-Thickness: Extends through the epidermis and dermis into the subcutaneous tissue, potentially involving muscle, bone, or other underlying structures (e.g., third-degree burn, deep pressure ulcer).

Classification by Contamination Level (Surgical Wounds):

• Clean: Uninfected wound with no inflammation, not entering respiratory, gastrointestinal, genitourinary, or oropharyngeal tracts.

• Clean-Contaminated: Surgical wound entering respiratory, gastrointestinal, genitourinary, or oropharyngeal tracts under controlled conditions.

• Contaminated: Open, fresh accidental wounds, or surgical wounds with major breaks in sterile technique or gross spillage from the gastrointestinal tract.

• Dirty/Infected: Old traumatic wounds with retained contaminated tissue, or wounds with existing clinical infection or perforated viscera.

Classification by Healing Time:

• Acute Wounds: Wounds that proceed through the normal phases of wound healing in a timely and predictable manner (typically weeks).

• Chronic Wounds: Wounds that fail to heal within the expected timeframe, often due to persistent inflammation, infection, or underlying conditions.

Phases of Wound Healing

Normal wound healing is a dynamic and complex biological process that occurs in a series of overlapping phases:

• Inflammatory Phase (Days 0-5):

  • Hemostasis: Immediate response to injury involving vasoconstriction and platelet aggregation to form a platelet plug, followed by the coagulation cascade to form a fibrin clot, stopping bleeding.

  • Inflammation: Vasodilation and increased capillary permeability allow inflammatory cells (neutrophils, macrophages) to migrate to the wound site. Neutrophils phagocytose bacteria and debris. Macrophages continue phagocytosis, release growth factors, and recruit other cells essential for subsequent phases. Characterized clinically by redness, swelling, heat, pain, and loss of function.

• Proliferative Phase (Days 3-21):

  • Granulation: Fibroblasts proliferate and synthesize collagen, forming new connective tissue. New blood vessels (angiogenesis) grow into the wound bed, creating a granular, pink, moist tissue.

  • Contraction: Myofibroblasts in the wound edge contract, pulling the wound margins together and reducing wound size.

  • Epithelialization: Epithelial cells from the wound edges or remaining hair follicles/glands migrate across the granulation tissue to cover the wound surface, restoring the epidermal barrier.

• Remodeling Phase (Day 21 – up to 2 years):

  • Collagen Maturation: Type III collagen, initially laid down, is gradually replaced by stronger Type I collagen.

  • Scar Formation: The scar tissue remodels, becoming stronger and less vascularized. The scar may flatten and fade in color over time. The tensile strength of the healed wound gradually increases but typically only reaches about 80% of the original tissue strength.

Healing by Intention:

• Primary Intention: Occurs in clean, surgically incised wounds with minimal tissue loss and edges that are closely approximated (e.g., sutured surgical wound). Healing is rapid with minimal scarring.

• Secondary Intention: Occurs in wounds with significant tissue loss, irregular edges, or contamination (e.g., large traumatic wounds, pressure ulcers). The wound is left open to heal by granulation, contraction, and epithelialization. This process is slower and results in more significant scarring.

• Tertiary Intention (Delayed Primary Closure): Occurs in contaminated wounds that are initially left open to allow for cleaning and reduction of infection risk. Once the wound appears clean and healthy, it is surgically closed.

Factors Impairing Wound Healing

Numerous factors can negatively impact the wound healing process, potentially leading to chronic wounds or complications.

• Local Factors:

  • Infection: Presence of microorganisms in the wound bed impairs healing and can cause tissue damage.

  • Inadequate Blood Supply/Ischemia: Poor oxygen and nutrient delivery to the wound (e.g., peripheral vascular disease, pressure).

  • Foreign Bodies: Presence of debris, sutures, or other foreign material in the wound.

  • Mechanical Stress: Excessive tension, pressure, or movement on the wound.

  • Excessive Exudate: Large amounts of wound fluid can macerate surrounding skin and create a poor healing environment.

  • Dry Wound Bed: Lack of moisture can delay cell migration.

  • Necrotic Tissue: Dead tissue in the wound bed acts as a barrier to healing and promotes bacterial growth.

• Systemic Factors:

  • Age: Healing can be slower in older adults.

  • Nutrition: Deficiencies in protein, vitamins (especially C and A), and minerals (especially zinc) impair healing.

  • Underlying Medical Conditions: Diabetes Mellitus (impaired circulation, neuropathy, increased infection risk), peripheral vascular disease, immunosuppression (e.g., HIV, chemotherapy), renal failure, liver disease.

  • Medications: Corticosteroids, NSAIDs, chemotherapy.

  • Smoking: Nicotine causes vasoconstriction, reducing blood flow to the wound.

  • Obesity: Can lead to poor circulation and increased risk of infection.

Complications of Wounds

Wounds can be associated with various complications that can delay healing, cause further tissue damage, or impact systemic health.

• Infection: The most common complication, characterized by increased pain, redness, swelling, warmth, purulent exudate, and delayed healing. Can lead to cellulitis, abscess formation, or systemic sepsis.

• Hemorrhage: Bleeding from the wound. Can be immediate or delayed.

• Hematoma: Collection of blood within the wound or surrounding tissues.

• Dehiscence: Separation of the wound edges, particularly in surgical incisions.

• Evisceration: Protrusion of internal organs through a dehisced wound.

• Fistula Formation: An abnormal connection between the wound and an internal organ or another body surface.

• Scarring: Formation of fibrous tissue. Can be hypertrophic (raised within the wound boundaries) or keloid (raised and extending beyond the wound boundaries). Contractures (scarring that restricts movement) can occur, especially over joints.

• Chronic Pain: Persistent pain associated with the wound or scar.

• Psychological Impact: Wounds, especially chronic or disfiguring ones, can have significant psychological effects on patients.

Wound Assessment and Management Principles

Effective wound management requires a systematic approach involving thorough assessment and implementation of appropriate interventions.

Wound Assessment:

• Location: Anatomical site of the wound.

• Size: Length, width, and depth.

• Shape and Edges: Regular or irregular, attached or unattached edges.

• Wound Bed: Appearance of the tissue (e.g., granulation tissue, slough, eschar, exposed structures).

• Exudate: Amount (minimal, moderate, copious), type (serous, sanguineous, serosanguineous, purulent), and odor.

• Periwound Skin: Condition of the skin surrounding the wound (e.g., intact, macerated, erythematous, dry, presence of edema).

• Signs of Infection: Redness, warmth, swelling, pain, purulent exudate, delayed healing.

• Pain: Level and characteristics of wound-related pain.

• Patient Factors: Overall health status, nutritional status, medications, mobility, psychological state.

General Management Principles:

• Wound Cleansing: Removing debris, exudate, and contaminants using appropriate solutions (e.g., normal saline) and techniques.

• Debridement: Removal of necrotic tissue, slough, and foreign material from the wound bed to promote healing. Methods include surgical, enzymatic, mechanical, autolytic, and biological debridement.

• Infection Control: Preventing or treating wound infection through proper hygiene, aseptic technique during dressing changes, and administration of antibiotics if indicated.

• Moisture Balance: Maintaining an optimal moisture level in the wound bed. This involves selecting dressings that absorb excess exudate while keeping the wound moist.

• Dressing Selection: Choosing appropriate wound dressings based on wound type, depth, exudate level, and the goal of treatment (e.g., absorption, moisture donation, debridement, protection).

• Protection: Protecting the wound from further trauma, pressure, and contamination.

• Pain Management: Assessing and managing wound-related pain effectively.

• Nutritional Support: Ensuring adequate protein, calorie, vitamin, and mineral intake to support healing.

• Management of Underlying Conditions: Addressing systemic factors that impair healing (e.g., blood sugar control in diabetes, improving circulation).

• Offloading/Pressure Relief: Reducing pressure on wounds caused by pressure (e.g., pressure ulcers).

• Patient Education: Educating the patient and caregivers about wound care, signs of complications, and the importance of adherence to the treatment plan.

• Referral: Consulting with wound care specialists or other healthcare professionals as needed.