Wounds and Classification of Wounds 5TH MBBS, By Dr Nwankwo Monday

Introduction A wound is a disruption of living tissue such as skin, mucous membrane, or organs, resulting in loss of normal anatomical structure and function. It is usually caused by external factors or internal underlying disease. Classifying wounds guides treatment, predicts healing, and estimates infection risks. Normal Wound Healing – Three Phases Reactive Phase – begins from time of injury and lasts 2‑5 days. Characterised by haemostasis (control of bleeding by vasoconstriction, platelet plug formation, coagulation then clot retraction), inflammation, epithelial migration, and demolition (removal of dead tissue by macrophages). Regenerative (Proliferative) Phase – can last up to 6 weeks. Involves re‑epithelialisation, matrix synthesis, and neovascularisation. Remodelling (Maturation) Phase – can last up to 2 years. Involves scar contraction, collagen cross‑linking, and shrinkage. Types of Wound Healing Healing by primary (first) intention – the wound is apposed using sutures, staples, skin tapes, or skin glue. Normal healing occurs. Usually gives minimal scar formation. Healing by secondary (second) intention – in the presence of extensive tissue loss or significant contamination or sepsis, the wound is debrided, irrigated but not sutured. It heals by granulation, contraction, and epithelialisation. Has poor scar formation. Delayed primary healing (tertiary intention) – wound is initially left open and dressed, allowing infection to clean out and oedema to resolve. Types of Wound Closures Primary wound closure – wound is closed immediately after it is created (surgically) or after irrigation at presentation (for non‑surgical wounds). Delayed primary wound closure – wound closure is delayed for 3‑5 days to allow for resolution of oedema. Secondary wound closure – wound closure is delayed to allow infection to subside. This is usually beyond 5 days. Materials for Skin Closure Sutures, staples, clips (e.g., Dermaclips), skin tapes (Steri‑strip), skin glues (dermal adhesive – liquid cyanoacrylate monomers). Classification of Wounds 1. By level of contamination and infection risk Class I (Clean) – uninfected, primarily closed surgical wounds. No entry into respiratory, alimentary, or genitourinary tracts (e.g., thyroidectomy). Low risk of infection (1‑3%). Class II (Clean‑Contaminated) – controlled entry into respiratory, alimentary, or genitourinary tracts without unusual contamination (e.g., appendectomy). Risk of infection 3‑11%. Class III (Contaminated) – open, fresh, accidental wounds or surgical procedures with a major break in sterile technique or gross spillage from the gastrointestinal tract. Risk of infection 11‑20%. Class IV (Dirty/Infected) – old traumatic wounds with retained devitalised tissue, or existing clinical infections (e.g., perforated viscera or abscesses). Risk of infection 27‑40%. Factors affecting infection rates in surgical wounds – patient factors (diabetes, obesity, smoking, age >65 years, malnutrition, steroids) – risk x 2‑3; surgery factors (duration >2 hours, implants like mesh/joint implants, poor blood supply, OR traffic); post‑op care (dressing technique, wound hygiene). 2. By healing time (acute vs chronic) Acute wounds heal in a predictable, short timeframe (days to weeks) following normal stages of healing. Chronic wounds fail to heal in an orderly set of stages, often taking months or years (e.g., pressure ulcers, diabetic ulcers, venous stasis ulcers). 3. By skin integrity Open wounds – the skin is broken, exposing underlying tissues (incisions, lacerations, abrasions, punctures). Closed wounds – the skin remains intact, but soft tissue is damaged underneath (contusions/bruises, haematomas, crush or traction injuries). 4. Specific types by aetiology and mechanism Incisions – clean cuts made by a sharp object like a scalpel. Lacerations – linear, jagged, or irregular tears in tissue. Abrasions/friction burns – surface scrapes where the top layer of skin is rubbed away. Punctures – deep holes caused by a sharp object (e.g., nail puncture, bites). Burns – caused by thermal (heat/cold), electrical, or chemical agents. Penetrating wounds – enters a body cavity (e.g., chest, abdomen). Avulsion – partial or complete loss or detachment of a tissue or organ. Crush – tissue devitalisation following heavy impact. Perforating wounds – object passes through a hollow viscera. 5. By depth and severity Superficial – only affects the epidermis (e.g., minor abrasions). Partial‑thickness – extends through the epidermis and into the dermis (e.g., second degree burns, blisters). Full‑thickness – extends through the dermis, subcutaneous tissue, and can expose muscle, tendon, or bone. 6. Based on intent – surgical (planned) or traumatic (accidental); tidy or untidy. 7. Based on level of tissue damage Simple – superficial (involving mainly skin and subcutaneous fat), well vascularised, results from sharp cut, edges are clean. Complex – deep and involves fascia, muscle, tendon, nerves, vessels, bones, or joint capsules. There is devitalisation. Classification of Thermal Wounds (Burns) First degree – superficial (epidermis only). Second degree – partial thickness (epidermis and superficial dermis, presenting with blisters). Third degree – full thickness (all skin layers), often painless due to nerve destruction. Fourth degree – deep tissue necrosis involving subcutaneous fat, muscle, or bone. Note on Management – Mnemonic “WATER” W – Wash + Haemostasis A – Anaesthesia T – Tetanus prophylaxis E – Explore + Evaluate R – Repair/Closure Post‑Op Care Dressing. Antibiotics (not routine for clean wounds). Wound review at 48‑72 hours for redness/pus. Suture removal: face 5‑7 days, scalp 7‑10 days, limbs 10‑14 days. Pain control.