Wound healing

Overview & Definition

A wound is any disruption of the normal anatomical continuity of skin or underlying soft tissue; wound healing is the highly conserved biological process that restores tissue continuity through a coordinated, overlapping sequence of cellular and molecular events. In adult mammalian skin, the end-result is repair with scar (not true regeneration). Understanding the phase-specific biology lets you diagnose a delayed wound, target the failing step, and choose the correct dressing, drug, or intervention.[1][2][4][9]

The four classical phases are: [1]

1. Haemostasis — minutes to hours after injury.
2. Inflammation — ~0 to 3 days (cells present up to day 5–7).
3. Proliferation — 3 days to ~3 weeks (24 days by classic autopsy data).
4. Remodelling — 3 weeks to 12 months (occasionally longer; the scar never reaches 100 % tensile strength). [1]

These phases are overlapping and continuous, not isolated — the macrophage at day 3 is the critical pivot between inflammation and proliferation, and its absence (in experimental models) causes the wound to stall in the inflammatory phase. [1]

The textbook distinction between healing by primary, secondary and tertiary intention is the cornerstone of acute wound management: [1]

• Primary intention — clean wound edges surgically approximated (suture, staple, glue, Steri-Strip); minimal tissue loss; fastest healing (7–14 days); least scar.
• Secondary intention — open wound left to granulate, contract, and re-epithelialise from the edges and adnexal remnants; greater tissue defect; slower healing (weeks to months); more scar and contraction.
• Tertiary (delayed primary) intention — contaminated, infected, or war wound left open initially, debrided/cleaned, then closed surgically 3–7 days later; balances infection control with timely closure. [1]

A related, often-tested distinction is between regeneration (true restoration of original tissue architecture, as in amphibian limb regrowth or early-gestation fetal skin) and repair (restoration of continuity with a fibrous scar, the rule in adult skin). [1]

Classification of wounds

Wounds are classified clinically along several axes — by cause, depth, contamination, and time to healing. The classification drives all downstream decisions: debridement, closure, dressing choice, antibiotic use, and prognosis.[2][4]

Epidemiology & Risk Factors

Cutaneous wound healing is a global health priority. The burden of chronic wounds is dominated by venous, arterial, diabetic, and pressure-related aetiologies, each with its own epidemiology and risk profile. Chronic wounds consume an estimated 2–3 % of the healthcare budget in industrialised countries, a figure that rises further when lost productivity, social care, and amputation are counted.[4][7][11]

Risk factors impairing wound healing can be grouped into local (in the wound) and systemic (in the patient). Diabetes is the single most consequential systemic factor, by virtue of microangiopathy, neuropathy, neutrophil dysfunction, and impaired fibroblast activity. Smoking, malnutrition (protein, vitamin C, zinc), corticosteroids, immunosuppression, age >80, anaemia, hypoxia, ionising radiation, and obesity all contribute additively. Local factors include infection, foreign body, haematoma, necrosis, tension, and ischaemia. [1]

Pathophysiology

Wound healing is a coordinated, sequence-driven biological process. At every stage, there is a specific cellular cast, a specific signalling network, and a corresponding clinical and histological appearance. The molecule-by-molecule detail matters: most chronic wounds fail because one specific step is blocked, and identifying that step dictates the intervention.[1][2][4][6][9]

Phase 1 — Haemostasis (minutes to hours)

Within seconds of vessel injury, three overlapping processes are initiated: [1]

1. Reflex vasoconstriction (endothelin, thromboxane A₂) — reduces blood loss.
2. Platelet adhesion, activation, and aggregation (primary haemostasis) — platelets adhere to exposed subendothelial collagen and von Willebrand factor via GPIb-V-IX and GPVI receptors, then undergo shape change, release α-granule contents (PDGF, TGF-β, EGF, FGF, VEGF) and dense-granule contents (ADP, serotonin, calcium). ADP and thromboxane A₂ recruit more platelets, forming the platelet plug.
3. Fibrin formation (secondary haemostasis) — exposure of tissue factor triggers the extrinsic pathway; contact with collagen triggers the intrinsic pathway; both converge on factor X activation → thrombin → fibrinogen → fibrin mesh that stabilises the plug and acts as a provisional extracellular matrix (ECM) scaffold for the migrating cells that arrive in the next phase. [1]

Crucially, the growth factors released in the first minutes are not just for stopping bleeding — they recruit neutrophils and macrophages within hours and orchestrate every later phase. The fibrin scaffold is also the road fibroblasts use to migrate into the wound from day 3 onwards.[1][2][6][9]

Phase 2 — Inflammation (0 to 3 days)

Inflammation is not just "rubor, calor, tumor, dolor" — it is the body's demolition and inspection crew at work. Neutrophils (polymorphonuclear leukocytes, PMNs) arrive within 6 hours, peak at 24–48 hours, and clear bacteria and devitalised tissue by phagocytosis, reactive oxygen species (NADPH oxidase–derived superoxide, hydrogen peroxide, hypochlorous acid via myeloperoxidase), and NETosis (release of neutrophil extracellular traps that bind pathogens). They undergo apoptosis after 24–48 hours and are cleared by incoming macrophages.[1][2]

Macrophages arrive on day 2–3 from circulating monocytes (recruited by MCP-1, PDGF, TGF-β), peak at day 3–5, and serve three critical roles: [1]

• Debridement — phagocytose apoptotic neutrophils and cellular debris.
• Antimicrobial defence — also kill bacteria via ROS and nitric oxide.
• Release of growth factors (TGF-β, VEGF, FGF, PDGF, IGF-1) that orchestrate the transition to proliferation: fibroblast activation, myofibroblast differentiation, angiogenesis, re-epithelialisation. [1]

The M1 → M2 phenotype switch by day 3–5 is the master timing signal. Prolonged M1 polarisation (from persistent infection, hypoxia, hyperglycaemia, or foreign body) is one of the central mechanisms by which chronic wounds get "stuck" in inflammation and fail to progress.[1][6][9]

T-lymphocytes arrive later (day 5–7) and modulate remodelling by releasing cytokines that influence collagen turnover and fibroblast activity. Mast cells and basophils contribute histamine-mediated vasodilation in the early phase. [1]

Phase 3 — Proliferation (3 days to 3 weeks)

Four overlapping subprocesses give the wound its tissue bulk:[1][2][4]

1. Fibroplasia — platelet- and macrophage-derived TGF-β, PDGF, and FGF recruit fibroblasts into the wound. Fibroblasts migrate along the fibrin provisional matrix (using integrins and the fibronectin-rich scaffold), proliferate, and deposit type III collagen, fibronectin, glycosaminoglycans, and hyaluronic acid — the new extracellular matrix that replaces fibrin. This provisional matrix is mechanically weak but provides the template on which type I collagen will later be laid.
2. Angiogenesis — VEGF, FGF-2, angiopoietin and PDGF drive endothelial cell migration and capillary sprouting into the wound. The result is granulation tissue — the bright-red, beefy, friable, vascularised connective tissue that fills the wound defect.
3. Epithelialisation — within 24 hours of injury in a moist wound (longer in dry wounds), keratinocytes at the wound edge detach from the basement membrane, become migratory, glide over the provisional matrix (using integrin-α5β1 and fibronectin), proliferate behind the migration front, and eventually re-stratify to reform a stratified epidermis. Re-epithelialisation is dramatically faster in a moist wound (Winter 1962/63; Hinman 1963) — the reason for the modern occlusion/dressing approach.
4. Wound contraction — under the influence of TGF-β, fibroblasts differentiate into myofibroblasts that express α-smooth-muscle actin and contract. Centripetal contraction can reduce an open wound by 0.5–1 mm per day, and accounts for most of the area reduction in secondary intention healing. [1]

The end of proliferation is marked by a confluent granulation tissue bed re-covered by advancing epithelium — the macroscopic appearance of an "active healing" wound. [1]

Phase 4 — Remodelling (3 weeks to 1+ year)

Remodelling is the longest phase and the one that determines final scar quality. Type III collagen (deposited in proliferation) is degraded by matrix metalloproteinases (MMP-1, MMP-8, MMP-13) and replaced by stronger type I collagen. New collagen fibres are reorganised along tension lines and cross-linked by lysyl oxidase (a copper-dependent enzyme). Myofibroblasts and fibroblasts are removed by Fas/FasL-mediated apoptosis. The scar becomes flatter, paler, and softer.[1][4]

Critically, tensile strength increases logarithmically: ~20 % at 3 weeks, ~30 % at 4 weeks, ~80 % at 3 months, then plateaus and never exceeds ~80 % of uninjured skin. The scar is acellular, avascular, and permanently weaker than unwounded skin. Long-term biological consequences include abnormal hair and sweat-gland function, loss of adnexal structures, and altered mechanical properties — the substrate for hypertrophic scarring, keloid formation, and contracture (covered in the keloid topic).[4]

Growth factors in wound healing — the master regulator cast

Wound healing is driven by growth factors released from platelets, macrophages, fibroblasts, endothelial cells, keratinocytes, and mast cells. Each has a specific receptor, a specific binding partner, and a specific cellular effect.[6][9]

Other key mediators: [1]

• IGF-1 (insulin-like growth factor) — fibroblast proliferation.
• CSF / G-CSF / GM-CSF — haematopoietic recruitment.
• IL-1, IL-6, TNF-α — pro-inflammatory cytokines; orchestrate early inflammation but excess prolongs inflammation (causative in chronic wounds).
• Cyclooxygenase-2 (COX-2) → prostaglandin E₂ (PGE₂) — vasodilation, pain.
• Lipoxins, resolvins, protectins — termination of inflammation (resolution phase, increasingly studied).
• MMPs (matrix metalloproteinases) and TIMPs (tissue inhibitors of metalloproteinases) — balance of ECM synthesis and degradation; chronic wounds show MMP overexpression and TIMP downregulation, causing net collagen degradation. [1]

Moist wound healing — the Winter/Hinman principle and its rationale

G.D. Winter's 1962/63 and Hinman & Maibach's 1963 experiments changed surgical practice forever: occlusive and semi-occlusive dressings heal partial-thickness wounds 30–50 % faster than dry exposure because epithelial cells migrate ~2–3 times faster across a moist, warm surface than under a desiccating scab. Occlusion also enables autolytic debridement — phagocytes and matrix proteases digest devitalised tissue under the dressing with minimal surgical trauma. The corollary is that the old practice of letting wounds "form a good scab" is harmful. Modern dressings (hydrocolloid, hydrogel, foam, film, alginate, hydrofibre, antimicrobial) all aim to exploit this principle, with the dressing choice driven by exudate volume, depth, and infection status.[3]

Chronic wound pathophysiology — what makes a chronic wound chronic

Chronic wounds (venous, arterial, diabetic, pressure, vasculitic) are trapped in the inflammatory phase. The unifying pathophysiology is: [1]

• Tissue hypoxia (from vascular disease, oedema) → fails to support neutrophil oxidative burst, fibroblast proliferation, and collagen synthesis.
• Repetitive ischaemia-reperfusion → ROS, inflammation.
• Hyperglycaemia → advanced glycation end-products stiffen collagen; neutrophil dysfunction; reduce NO.
• Biofilm — chronic wounds harbour polymicrobial biofilms that resist antibiotics 100–1000× compared to planktonic bacteria; protect bacteria from leukocyte phagocytosis.
• MMP overexpression + TIMP reduction → net collagen degradation rather than remodelling.
• Growth factor sequestration or degradation — TGF-β, PDGF, KGF inactivated by excess protease activity.
• Cellular senescence — fibroblasts, keratinocytes, and endothelial cells from chronic wounds enter senescence and lose proliferative capacity; they secrete a SASP (senescence-associated secretory phenotype) of pro-inflammatory cytokines and proteases that perpetuates the non-healing state.
• Impaired M1→M2 macrophage polarisation — chronic wound macrophages remain pro-inflammatory. [1]

Understanding this pathophysiology is the basis for advanced therapies (NPWT, growth factor gels, skin substitutes, HBOT) and for the TIME framework below.[1][2][6][8]

Clinical Presentation

Acute wound

A normal acute wound progresses through the four phases with a predictable clinical pattern.[2]

Atypical acute-wound presentations — the examiner's favourites — include: [1]

• Diabetic patient: diminished inflammation (so neutrophil signs mute); a wound may be disproportionately infected despite modest erythema. Always investigate when in doubt.[10]
• Immunosuppressed: atypical organisms (Pseudomonas, fungal, mycobacterial), no pyrexia, atypical pain.
• Corticosteroid-dependent patient: minimal erythema, swelling, heat, or pain — the cardinal signs are suppressed. A wound that "doesn't hurt" in a steroid-dependent patient with diabetes is a wound to biopsy and culture.
• Pregnant woman: increased scarring tendency (keloid, hypertrophic scar); relative immune modulation.
• Elderly: muted inflammation, slower granulation, higher anaesthetic risk.
• Child: faster healing, but more prone to hypergranulation and exuberant scarring.

Chronic wound — and its look-alikes

A chronic wound fails to complete at least 50 % area reduction within 4 weeks, and to fully heal within 12 weeks, despite optimal aetiology-appropriate care. The wound is "stuck" in the inflammatory phase; the edge does not advance; the base is often pale, friable, hypergranular, sloughy, or exudative. Surrounding skin may be macerated, eczematous, or hyperpigmented (haemosiderin in venous disease; haematogenous pigmentation in chronic infection). Classic clinical hallmarks: persistent exudate, foul odour (biofilm or Pseudomonas), undermining, rolled and raised edges (think malignancy). [1]

Differential Diagnosis

The differential of a chronic non-healing ulcer is wide, and every candidate must be evaluated. The mnemonic "VAMPiDRAVL" (Venous, Arterial, Marjolin/Martorell, Pyoderma gangrenosum/Martorell/Malignancy, Dermatitis artefacta, Rheumatologic, Atypical Mycobacteria, Vasculitis, Lymphoedema, Lymphoma) covers most; the working differential in any specific patient depends on site, age, history, and risk profile. [1]

Clinical & Bedside Assessment

Assessment of a wound is structured and systematic. The TIME framework (Schultz et al. 2003) is the international standard for chronic wound assessment; it captures the four clinical questions that drive management.[8]

Comprehensive wound assessment (the structured bedside)

1. Patient-level history — age, comorbidities (diabetes, vascular disease, RA, IBD), medications (corticosteroids, immunosuppressants, anticoagulants, chemotherapy), smoking, alcohol, nutrition, prior wounds, prior amputations, family history.
2. Wound-specific history — onset, duration, precipitant, prior treatments, response, recurrence, frequency of dressing changes, pain (timing, character, modifiers), discharge (volume, colour, odour), impact on daily life.
3. Wound examination — site (anatomic, clock-face), size (length × width × depth with ruler in centimetres), undermining/tunnelling (probe with cotton bud, document extent), base (% granulation, slough, eschar), exudate (type: serous/serosanguineous/purulent/haemorrhagic; volume: none/scant/moderate/heavy), edge (advancing/rolled/undermined/macerated), surrounding skin (cellulitis, eczema, maceration, callus, induration), odour, pain on dressing change.
4. Peripheral limb examination — pulses (dorsalis pedis, posterior tibial, popliteal, femoral); capillary refill (< 3 sec normal); temperature gradient; oedema (pitting grade 0-3); trophic changes; foot deformity (Charcot, claw toes); footwear.
5. Perfusion assessment — ABPI (see Investigations), toe-brachial index (TBI), transcutaneous oxygen (TcpO2) in selected cases.
6. Sensory assessment (diabetic foot) — 10 g Semmes-Weinstein monofilament (≥4-6 plantar sites; loss = high ulcer risk); 128 Hz tuning fork at great toe; ankle reflexes (present/absent); pin-prick; proprioception.
7. Risk assessment (pressure ulcer) — Braden Scale (most validated): six subscales scored 1-4 — Sensory perception, Moisture, Activity, Mobility, Nutrition, Friction/Shear; total score range 6-23; < 18 = at risk, < 13 = severe risk; Norton Scale (older, less discriminative), Waterlow Scale (UK, higher sensitivity), MUST (Malnutrition Universal Screening Tool, UK).
8. Pressure ulcer staging (NPUAP/EPUAP/PPPIA 2016) — Stage I (non-blanchable erythema of INTACT skin), Stage II (partial-thickness loss; pink/red, no slough), Stage III (full-thickness loss, fat visible), Stage IV (full-thickness loss, tendon/muscle/bone visible), Unstageable (obscured by eschar/slough), Suspected Deep Tissue Injury (SDTI; persistent non-blanchable deep red/maroon/purple discolouration).
9. Standardised serial photography — most practical objective monitoring tool. [1]

Bedside assessment scoring systems

Investigations

Investigations are not arbitrary; they must be aetiology-driven and used to alter management. Below is the structured investigation set, with named values, thresholds, and the evidence behind them.[7][11]

Perfusion (mandatory for any chronic lower-extremity ulcer)

Toe-brachial index (TBI) is preferred in diabetes (medial arterial calcification makes ABPI unreliable); a TBI of < 0.7 is abnormal. Transcutaneous oxygen pressure (TcpO2) on the dorsum of the foot reflects distal perfusion and is used in assessing amputation level (TcpO2 >30 mmHg suggests healing capacity). [1]

Vascular imaging

• Venous duplex ultrasound — first-line for suspected venous ulcer; identifies reflux (retrograde flow >0.5 sec, valve closure time) and obstruction in superficial (great saphenous, small saphenous) and deep (femoral, popliteal, tibial) systems. Drives the decision about endovenous ablation (foam sclerotherapy, endovenous laser, radiofrequency) of superficial reflux to improve healing.[7]
• Arterial duplex ultrasound — first-line non-invasive test for peripheral arterial disease; gives anatomic and haemodynamic information.
• CT angiography / MR angiography — when endovascular intervention is planned; provides anatomic detail of stenosis and run-off.
• Catheter digital subtraction angiography (DSA) — gold standard; reserved for when intervention is contemplated or as part of an endovascular procedure.

Metabolic and nutritional work-up

Microbiology

• Wound swab — standard for clinically infected wounds; gold standard is tissue biopsy in chronic non-healing wounds. Use the Levine technique: rotate a swab over a clean 1 cm² area with pressure; express fluid from the wound. In wounds with >10⁵ CFU/g of tissue, infection is considered present.
• MRSA screen — nasal + axillary + groin; pre-op if patient has history of MRSA.
• Pseudomonas screening — wet chronic wound with sweet/grape-like odour, blue-green exudate.
• AFB, fungal, atypical — for chronic non-healing with negative conventional cultures, especially with travel or tropical exposure (Buruli, chromoblastomycosis, leishmaniasis). [1]

Histopathology

• Biopsies are mandatory when: (a) a chronic wound has been present for >3 months without progression, (b) the wound shows any atypical feature (raised everted edge, exophytic growth, friable granulation, regional lymphadenopathy, or rapid change), (c) vasculitis is suspected (purpura, livedo, multi-system features), (d) infection with an unusual organism is suspected, (e) pyoderma gangrenosum is suspected.
• Technique: elliptical incisional biopsy from the wound edge (where pathology is most active), including both affected and adjacent normal skin. Send separately for histology AND microbiology. Multiple biopsies increase yield.
• Histology of healing: in early phases, granulation tissue with new capillaries and fibroblasts; later, dense collagen with reduced cellularity; in chronic wounds, persistent inflammatory infiltrate, fibrosis, fibrin deposition; in Marjolin, atypical keratinocytes with dermal invasion. [1]

Diagnostic criteria and named scores reproduced verbatim

• TIME framework — Tissue / Infection / Moisture / Edge (Schultz et al. 2003).[8]
• Braden Scale — six subscales: Sensory perception, Moisture, Activity, Mobility, Nutrition, Friction/Shear; score 6-23; < 18 at risk; < 13 severe risk.
• Norton Scale — five domains: physical condition, mental condition, activity, mobility, incontinence.
• Waterlow Scale — eleven items: sex, age, BMI, mobility, incontinence, skin type, weight loss, appetite, surgery, trauma, mental state.
• PUSH Score — three subscores: length × width (0-10), exudate amount (0-3), tissue type (0-4).
• Wagner grading (DFU) — 0 = no ulcer high-risk foot; 1 = superficial ulcer; 2 = deep ulcer to tendon/bone/capsule; 3 = deep ulcer with abscess or osteomyelitis; 4 = localised gangrene (forefoot); 5 = extensive gangrene (whole foot).
• Texas University — 4 grades (0, I, II, III) × 4 stages (A, B, C, D); depth increases with grade; B = infection, C = ischaemia, D = both.
• IWGDF risk categories — 0 no neuropathy; 1 neuropathy alone; 2 neuropathy + PAD or deformity; 3 neuropathy + PAD + deformity or prior ulcer/amputation.
• PEDIS — Perfusion, Extent/size, Depth/tissue loss, Infection, Sensation; primarily research use.
• S(AD)SAD — Size, Area, Depth, Sepsis, Arteriopathy, Neuropathy; >6 = poor healing.
• NPUAP/EPUAP/PPPIA 2016 pressure ulcer staging — Stage I-IV, Unstageable, Suspected Deep Tissue Injury.
• CEAP — Chronic venous disorders, Clinical (C0-6), Etiology (Ec = congenital, Ep = primary, Es = secondary), Anatomy (As = superficial, Ap = perforator, Ad = deep), Pathophysiology (Pr = reflux, Po = obstruction, Pr,o = both).

Management — Resuscitation

Severe wound complications require resuscitation-level interventions — wound sepsis, necrotising fasciitis, or wet gangrene. The bundle is ATLS-style, with a strong surgical-component bias.[2][4]

Management — Definitive & Stepwise

Acute wound management — the bedside ladder

1. Stop bleeding — direct pressure, elevation, tourniquet (rare); surgical control if artery.
2. Pain control — morphine 5-10 mg IV/SC/PO PRN; nerve block as appropriate; NSAIDs avoided in the first 48-72 h (delay inflammatory phase).
3. Examination under aseptic conditions — depth, contamination, tendon/vessel/nerve/bone injury, joint penetration.
4. Irrigation and debridement — copious normal saline (300-1000 mL) at low pressure (4-15 psi) with 20 mL syringe and 18-19 G catheter; reduce bacterial load by 10²-10⁵; avoid antiseptic solutions in clean wounds (toxic to fibroblasts); remove devitalised tissue (sharp/surgical best; enzymatic with streptokinase-streptodornase for selected cases; autolytic with hydrocolloid/hydrogel for thin slough; larval (maggot) therapy with sterile Lucilia sericata larvae for selected chronic wounds with MRSA or biofilms).
5. Tetanus — see above.
6. Antibiotics — only with clinical infection or heavily contaminated wound.
7. Closure (within 6-8 h for clean wound, longer after careful debridement in contaminated) — primary suture (deep +/- superficial), skin closure strips, tissue adhesive (octyl/butyl cyanoacrylate, e.g. Dermabond); staples; consider delayed primary if heavy contamination.
8. Dressing — matched to exudate and depth.
9. Review — at 7-14 days; sutures removed when healed: face 5-7 d, scalp 7-10 d, trunk 10-14 d, limb 10-14 d, foot 14-21 d; absorbable sutures (Polydioxanone PDS, Monocryl) for deep tissue. [1]

Chronic wound management — the structured chronic-wound consult

The chronic wound consult has five mandatory components, in this order: [1]

1. Establish aetiology — venous, arterial, diabetic/neuropathic, pressure, vasculitic, neoplastic, drug-induced, infective; mixed aetiologies are common.
2. Treat systemic factors — HbA1c control, smoking cessation, nutrition (protein, vitamin C, zinc, vitamin A, iron), corticosteroid dose reduction, optimise cardiac output, anaemia correction.
3. Wound bed preparation — TIME — see Mnemonic above.[8]
4. Apply the correct specialist therapy — compression (venous), offloading (DFU), revascularisation (arterial), pressure redistribution (PU), immunosuppression (vasculitis/PG), wide excision (Marjolin).
5. Reassess at 4 weeks — % area reduction — the single most useful early predictor. < 30 % area reduction at 4 weeks = unlikely to heal within 12 weeks; reconsider and intensify (NPWT, advanced dressing, growth factor, skin substitute, HBOT).[13]

Modern wound dressings — exudate-matched

Modern dressings exploit the moist wound healing principle (Winter 1962). Dressing choice is driven by wound depth, exudate volume, infection status, patient comfort, and cost.[3]

A aetiology-specific ladders

Venous leg ulcer

The cornerstone of venous ulcer management is sustained compression that overcomes the venous hydrostatic pressure gradient (~80-100 mmHg in the leg). Without compression, healing rates are ~30 % at 12 weeks; with adequate compression 35-40 mmHg at the ankle, healing rates are 70-80 % at 12 weeks.[7][11]

Arterial ulcer

The cornerstone is revascularisation if feasible. Compression is contraindicated. Amputation may be necessary for non-revascularisable limb-threatening disease.[4]

Diabetic foot ulcer (DFU)

The cornerstone is offloading to redistribute pressure away from the wound. Total contact cast (TCC) is the gold standard for non-infected, non-ischaemic plantar neuropathic DFU.[10]

Pressure ulcer

The cornerstone is pressure redistribution + repositioning + nutrition. [1]

Marjolin ulcer

Pyoderma gangrenosum

The cornerstone is systemic immunomodulation with rigorous avoidance of surgical debridement (pathergy).[4]

Chronic wound management — comprehensive medication and procedural ladders

Antibiotics for clinically infected chronic wounds (only for clinical infection, NOT for colonisation): [1]

Topical metronidazole is an excellent adjunct for malodorous anaerobic ulcers (0.75 % gel or 1 % cream twice daily). [1]

Nutritional support for wound healing

Advanced wound therapies — when the wound is not healing

Specific Subtypes & Scenarios

The clinical syndrome of "wound that won't heal" has many specific entities, each with its own pathophysiology, epidemiology, and management.[2][4]

Granulation tissue variants and complications

• Hypergranulation (over-granulation, exuberant granulation tissue that prevents epithelialisation) — friable red tissue raised above the wound surface; often due to over-moist environment or occlusive dressing; treat with silver nitrate cautery, topical corticosteroid, change to foam dressing; biopsy if atypical (pyogenic granuloma, amelanotic melanoma).
• Undermining / tunnelling — cavity extends under edges; common in pressure ulcer Stage III/IV; document with probing; pack with alginate or hydrofibre for cavity fill.
• Wound contracture — excessive wound contraction, often across joints (e.g. after burn); functionally limiting; may require surgical release and skin graft/flap.
• Fistula — abnormal communication with another epithelial surface (e.g. enterocutaneous); requires management of the source (surgery, drainage) before the wound can heal. [1]

Complications & Pitfalls

Wound-related complications range from extension of infection to systemic sepsis, from cosmetic to life-threatening. Recognising them in time is the art.[2][4]

Prognosis & Disposition

Prognosis depends on wound aetiology, size, duration, comorbidities, and adherence to therapy.[13]

Disposition: [1]

• Outpatient wound-care clinic / community nursing — most chronic wounds.
• Multidisciplinary foot service — DFU (podiatrist, vascular, orthotist, diabetes, wound nurse).
• Multidisciplinary leg ulcer service — venous ulcer (vascular + wound nurse + dermatology).
• Hospital admission — severe wound infection, sepsis, NPWT initiation, IV antibiotics, post-operative flap care, frail patient unable to self-care, non-healing despite optimal outpatient care.
• Referral — vascular surgery (ABPI < 0.5), dermatology (vasculitis/PG workup), plastic surgery (Marjolin, large flaps), orthotics (DFU insoles, footwear), wound nurse (chronic ulcer), dietetics (malnutrition), pain team (chronic ulcer pain). [1]

Safety net and follow-up:[13]

• Discharge criteria for acute wound — re-epithelialised; sutures removed; no inflammation/infection.
• Follow-up of chronic wound — at 1, 2, 4, 6, 8, 12 weeks; clinic visits at minimum 3-monthly for the first year.
• Skin-graft / flap follow-up — daily for 5-7 d, then weekly for 6 wk.
• Document — standardised serial photography, PUSH score trend, dressing review. [1]

Quality of life of patients with chronic wounds is significantly impaired — equivalent to congestive heart failure or COPD. Chronic pain, malodour, sleep disturbance, and mobility restriction drive depression, social isolation, and loss of work productivity. Address the psychosocial as well as the physical. [1]

Special Populations

Different patient groups shift the risk profile and the management priorities.[2][4]

Evidence, Guidelines & Regional Differences

Wound management evidence is broad but heterogeneous — dominated by small RCTs, observational series, and expert consensus. The landmark papers and current guidelines are:[4][7][8][10][11]

Landmark studies and foundational documents: [1]

• Winter GD 1962/1963 — first demonstration of moist wound healing; occlusive dressings 30-50 % faster than dry exposure in partial-thickness wounds.
• Hinman CD, Maibach H 1963 — independently confirmed moist wound healing in humans.
• Schultz GS, Sibbald RG, Falanga V et al. 2003 — TIME framework (Wound Repair Regen 2003; 11 Suppl 1); systematic, scientific approach to chronic wound care.[8]
• Steed DL 1995 (J Am Coll Surg) and 2006 — pivotal RCTs of recombinant human PDGF (becaplermin) in chronic DFU; first growth factor therapy approved.
• Marston WA et al. 2016 — Wound Healing Society 2015 update on guidelines for venous ulcers; key recommendations on compression >30 mmHg, pentoxifylline, endovenous ablation, graft.[7]
• Nelson EA, Adderley U 2011 — BMJ Clinical Evidence review of compression for venous ulcer; multi-layer >40 mmHg class III > short-stretch > class II; 4-layer > short-stretch in trials.[11]
• IWGDF 2015, 2019, 2023 — international guidelines on DFU prevention and management; offloading (TCC gold standard), classification, infection, Charcot, peripheral arterial disease.
• NICE NG19 2015 (UK) — Diabetic foot problems: prevention and management; integrated foot care, urgent referral, antibiotic choices, offloading.
• EWMA (European Wound Management Association) 2017 onward — TIME framework implementation document; NPWT, antimicrobial, and biofilms position documents.
• Game FL et al. 2012 / 2016 (Cochrane) — HBOT for chronic DFU modestly reduces major amputation; not routine.
• Huang W et al. 2014/2016 (Cochrane) — Apligraf + standard care increases healing of venous ulcer and chronic DFU vs standard care alone; Dermagraft supported for DFU >6 wk.[12]
• Dai et al. 2016 — comparative analysis of skin substitutes used for DFU; Apligraf / Dermagraft evidence base; amniotic membrane and bilayered emerging.[12]
• Margolis DJ et al. 2000 (Br J Dermatol) — venous leg ulcer multicentre study of % area change as a prognostic index at 24 weeks — foundational for the 4-week healing-predictor rule.[13]
• Steed DL et al. 1996 and subsequent PDGF / becaplermin trials (Wound Rep Reg; J Amer Acad Derm).
• Greer N et al. 2013 (VA Evidence-based Synthesis Program) — NPWT for chronic wounds; evidence mixed.
• **Vuorisalo S, Brull DJ, Mohammadieh HA — venous ulcer recurrence prevention; compression hosiery lifelong reduces recurrence 50 %+.

Regional differences: [1]

Areas of controversy: [1]

• HBOT in DFU — Cochrane-positive for major amputation but trials small; cost and limited availability; selection of patients (Wagner grade not consistent across trials).
• Becaplermin (rhPDGF) — black-box warning for malignancy; not approved in Europe; clinical use declining.
• PRP (autologous platelet-rich plasma) — meta-analyses mixed; trial heterogeneity; not standard of care.
• Maggot (larval) therapy — RCTs show equivalence with conventional debridement (Sherman 2002; Dumville 2009); patient acceptance limits use.
• SGLT2 inhibitors and amputation — canagliflozin amputation-risk signal 2017; subsequent studies mixed; regulatory advisory relaxed; benefit-risk favours continued use in most.
• Vitamin C mega-dose for wound healing — limited evidence beyond repletion; mega-dose IV in burns and critically ill inconsistent.
• Manuka honey — Cochrane Jull et al. 2015/2017 supports honey for partial-thickness burns but not for chronic leg ulcer; commercial availability drives off-label use. [1]

Exam Pearls

A high-yield summary of the must-remember facts for any dermatology, surgery, or general medicine exam.[1][2][4]

Exam-favourite MCQ stems: [1]

1. Which cell is the master regulator of wound healing? — Macrophage (releases TGF-β to switch from inflammation to proliferation; debridement of apoptotic neutrophils).
2. Which growth factor is anti-fibrotic? — TGF-β3 (TGF-β1 and β2 are pro-fibrotic).
3. Which is true about scar maturation? — Final tensile strength ~80 % of uninjured skin, plateau; never reaches 100 %.
4. Vitamin deficiency with impaired wound healing? — Vitamin C deficiency = scurvy = wound dehiscence (cofactor for prolyl/lysyl hydroxylase, collagen cross-linking).
5. Element essential for epithelialisation? — Zinc (zinc deficiency impairs leukocyte function and epithelial cell proliferation).
6. Which dressing for dry necrotic wound? — Hydrogel (donates moisture; supports autolysis).
7. Which dressing for heavily exuding bleeding wound? — Alginate (Ca²⁺-mediated haemostasis; high absorbency).
8. Which dressing for infected wound? — Antimicrobial: silver, iodine, honey, PHMB (NB: iodine cytotoxicity, silver for 2-4 weeks max).
9. First-line for venous leg ulcer? — High-compression bandaging (40 mmHg at ankle) — Class III (+/- pentoxifylline 400 mg TDS); 4-layer > short-stretch; Unna's boot for tolerability.
10. ABPI < 0.5 = ? — Severe PAD; compression CONTRAINDICATED; refer for revascularisation.
11. ABPI >1.3 = ? — Non-compressible (calcified, often DM); use toe-brachial index (TBI < 0.7).
12. Diabetic foot ulcer: which dressing is wrong if ABPI suggests calcification? — Use TBI; high ABPI often falsely normal in DM.
13. What is the gold standard offloading for plantar neuropathic DFU? — Total contact cast (TCC).
14. Pyoderma gangrenosum — what to AVOID? — Surgical debridement (pathergy worsens lesion); treat with high-dose corticosteroids or cyclosporin.
15. Marjolin ulcer — most important action? — Biopsy ANY non-healing wound >3 months and ANY changing scar (elliptical biopsy of edge).
16. Marjolin ulcer treatment? — Wide local excision 2-4 cm with SLN biopsy ± adjuvant radiotherapy.
17. Classic dressing principles? — Moist wound healing (Winter 1962/63); match dressing to exudate; TIME framework.
18. Pressure ulcer staging Stage I vs II? — Stage I = non-blanchable erythema, INTACT skin; Stage II = partial-thickness loss.
19. Braden Scale components? — Sensory perception, Moisture, Activity, Mobility, Nutrition, Friction/Shear.
20. Smoking in wound healing? — Nicotine vasoconstriction + CO reduces oxygen delivery + impairs fibroblast migration; smoking cessation 4 wk pre-elective halves wound complication.
21. What reverses corticosteroid-induced healing impairment? — Vitamin A 25,000 IU/day.
22. BECAPLERMIN contraindicated in? — Malignancy (black-box warning) — recombinant PDGF gel.
23. Wet wound with foul odour — likely organism? — Anaerobes (or Pseudomonas in wet ulcer; sweet/grape-like smell); treat with topical / systemic metronidazole.
24. Compression class for maintenance after venous ulcer healing? — Class II-III elastic hosiery lifelong.
25. Pentoxifylline for VLU? — 400 mg PO TDS (Cochrane-supported as adjunct to compression); contraindicated in recent cerebral/retinal bleed. [1]

Exam application bank (NEET-PG / INICET)

One-line answer

Wound healing is a coordinated, overlapping biological sequence of (1) Haemostasis (minutes–hours — platelet plug, fibrin, growth factors), (2) Inflammation (0–3 days — neutrophils then macrophages clear debris), (3) Proliferation (3 days–3 weeks — fibroblasts synthesise type III collagen, angiogenesis, epithelialisation, granulation tissue, wound contraction by myofibroblasts), and (4) Remodelling (3 weeks–12 months — type III → type I collagen, scar maturation, max ~80% tensile strength, never 100%). Healing by intention: primary (surgically approximated edges, fastest, minimal scar), secondary (open wound fills by granulation and contracts), tertiary (delayed primary closure after debridement). Growth factors central: PDGF, TGF-β1/2, VEGF, FGF-2, EGF. Chronic wounds (arterial, venous, diabetic, pressure, vasculitic, pyoderma gangrenosum, Marjolin) stall in inflammation. TIME wound-bed

Worked stems (answer without another resource)

Stem 1 — Classic presentation. Map symptoms to mechanism; name the first investigation and first treatment step with dose/route if drug therapy is standard. [1]

Stem 2 — Unstable / complicated. List red flags that force immediate resuscitation, theatre, ICU, antidote, or reperfusion — and what you do in the first 15 minutes. [1]

Stem 3 — Atypical group. Elderly, pregnancy, child, or immunocompromised: how presentation and thresholds change. [1]

Stem 4 — Differential trap. Name the three closest mimics and one discriminator for each. [1]

Stem 5 — Disposition. Who goes home with safety-netting, who is admitted, who needs HDU/ICU/theatre, and what follow-up is mandatory. [1]

Rapid viva checklist

1. Definition + classification
2. Pathophysiology chain
3. Bedside signs / criteria
4. Score with exact components (if any)
5. Emergency bundle
6. Definitive therapy with doses
7. Complications of disease and of treatment
8. Special populations
9. Guideline/trial name if classic
10. Three exam traps

Coverage self-check

If you cannot answer any stem above from this page alone, re-read the matching section — the page is intended to be self-sufficient for final-prof and NEET-PG/INICET questions on Wound healing.