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SURGERY NOTES: WOUND, WOUND HEALING, SINUS, ULCER, FISTULA & BURNS

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1. WOUND

Definition

Classification of Wounds

• Epidermal
• Dermal (superficial or deep)
• Full thickness

• Simple
• Complex (significant soft-tissue loss, open fracture/joint, visceral involvement)
• Complicated (infection, necrosis, haematoma, gas gangrene, compartment syndrome)
• Chronic (vascular ulcers, pressure ulcers, diabetic ulcers)

Wound Assessment

• Assess using ATLS principles
• Note site, size, geometry, contamination, pulsatile bleeding, deformities
• Correlate with mechanism of injury (e.g., high-pressure injection injuries can track proximally and require urgent debridement)
• Assess motor and sensory function before local anaesthetic

Wound Management Principles

1. Haemostasis - direct pressure, tourniquet if needed
2. Analgesia - local or systemic
3. Debridement - remove necrotic/foreign material; copious irrigation
4. Dead space obliteration
5. Closure - primary, delayed primary, or secondary intention
6. Dressings - appropriate to wound type
7. Tetanus prophylaxis
8. Antibiotics - only if clinically indicated

Types of Wound Closure

• Primary (1st intention): Wound edges apposed directly - clean wounds <6 hours old
• Delayed primary: Closure at 3-5 days - contaminated wounds
• Secondary (2nd intention): Left open to granulate - infected/heavily contaminated
• Tertiary / healing by granulation

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2. WOUND HEALING

Phases of Normal Wound Healing (Bailey & Love; Schwartz)

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Phase 1 - HAEMOSTASIS (Immediate: 0-10 min)

• Disruption of vascular endothelium → vasoconstriction and exposure of subendothelial extracellular matrix
• Platelets adhere, activate and aggregate → platelet plug formation
• Platelet activation releases: TXA2, ADP, serotonin, PDGF, TGF-β, EGF, VEGF
• Coagulation cascade activated → fibrin clot provides provisional wound matrix
• Fibrin clot acts as scaffold for subsequent cellular migration

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Phase 2 - INFLAMMATION (Days 1-5)

• Vasodilation and increased vascular permeability
• Wound becomes red, swollen, warm, painful
• Neutrophils arrive first (0-2 days): phagocytose bacteria and debris; release proteases and reactive oxygen species
• Macrophages arrive by day 2-3: key orchestrators of wound healing
  • Phagocytose debris and dead neutrophils
  • Release growth factors: PDGF, TGF-β, FGF, VEGF, IL-1, TNF-α
  • Macrophages are essential - macrophage-depleted wounds fail to heal
• Lymphocytes arrive later and regulate healing

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Phase 3 - PROLIFERATION (Days 5-21)

• Stimulated by VEGF, FGF, TGF-β
• Endothelial cells sprout from existing vessels to form new capillary loops
• Essential for nutrient delivery to healing wound
• Produces the characteristic red, granular appearance of granulation tissue

• Fibroblasts migrate into wound, stimulated by PDGF, TGF-β, FGF
• Fibroblasts synthesise collagen (primarily Type III initially, then Type I)
• Collagen synthesis requires oxygen, Vitamin C, iron, α-ketoglutarate as cofactors for hydroxylation of proline and lysine
• Initially Type III (fetal-type) collagen predominates → later replaced by Type I
• Granulation tissue = fibroblasts + new blood vessels + inflammatory cells in ground substance

• Keratinocytes at wound margins proliferate and migrate over moist wound surface
• Epithelialization rate increases by 50% in a moist environment vs dry
• Stimulated by EGF, TGF-α, keratinocyte growth factor

• Myofibroblasts (modified fibroblasts with actin) generate contractile force
• Wound edges drawn toward centre
• Important in open wounds; can cause contracture if excessive

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Phase 4 - MATURATION AND REMODELLING (Day 21 onwards - up to 2 years)

• Collagen cross-linking and reorganisation
• Type III collagen gradually replaced by Type I collagen
• Wound strength increases: 30% at 3 weeks, 80% at 3 months (never reaches 100% of normal)
• Tensile strength peaks at ~80% of original skin strength
• Collagen turnover mediated by matrix metalloproteinases (MMPs) balanced by TIMPs
• Scar vascularity decreases → scar becomes pale and flat

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Growth Factors in Wound Healing (Schwartz Table)

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Types of Healing

1. Primary intention (1st intention): Clean, apposed wound - minimal scar
2. Secondary intention (2nd intention): Open wound granulates from base - more scar
3. Tertiary/Delayed primary: Wound left open then closed at 3-5 days

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Factors Affecting Wound Healing

• Age: Delayed healing in elderly (decreased protein synthesis, comorbidities)
• Diabetes mellitus: Impaired neutrophil function, microvascular disease, neuropathy
• Malnutrition: Vitamin C deficiency → impaired collagen synthesis (scurvy); zinc deficiency → impaired cell proliferation
• Anaemia: Profound anaemia (<15% Hct) impairs oxygen delivery and healing
• Obesity: Adipose tissue poorly vascularised; increased tension on closure
• Immunosuppression: HIV, corticosteroids, chemotherapy
• Smoking: Vasoconstriction → tissue hypoxia; impairs neutrophil function
• Steroids: Inhibit inflammatory phase (angiogenesis, neutrophil/macrophage migration, fibroblast proliferation); inhibit collagen synthesis; effect most significant in first 3-4 days post-injury

• Infection (most important local factor)
• Ischaemia/necrotic tissue
• Oedema
• Foreign bodies (sutures, implants)
• Mechanical injury and tension
• Ionising radiation
• Low oxygen tension

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Abnormal Wound Healing

• Raised scar confined within the original wound margins
• More common in areas of tension (flexure surfaces)
• Occur early (within weeks), may regress spontaneously
• Treated with: topical silicone, intralesional corticosteroid injection, compression therapy, surgical excision

• Extend beyond original wound borders - can be locally destructive
• More common in darker skin types
• Common sites: face, earlobes, deltoid, presternal region
• Arise months after injury; do not regress spontaneously
• More resistant to treatment; may require repeated excision with adjuvant radiotherapy

• Failure of wound to remain closed; seen in 1-3% of abdominal wounds
• Risk factors: infection, obesity, malnutrition, poor technique, steroids

• Excess wound contraction causing functional limitation
• Common after burns

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Healing in Specific Tissues (Schwartz)

• Bone: Haematoma → callus (woven bone) → remodelling (lamellar bone); primary bone healing requires rigid fixation
• Cartilage: Limited capacity - avascular; mainly via diffusion
• Tendon: Intrinsic (vincular blood flow, synovial diffusion) + extrinsic (fibrous adhesions) healing; early mobilisation promotes intrinsic healing
• Nerve: Wallerian degeneration distally; regeneration guided by Schwann cell bands of Büngner at 1-3 mm/day; neurotropism mediated by growth factors
• Fetal wound healing: Scarless healing - higher TGF-β3, hyaluronic acid, fewer inflammatory cells; no scar formation

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3. SINUS

Definition

Classification

• Arise from remnants of persistent embryonic ducts
• Examples: branchial sinus, thyroglossal sinus, pre-auricular sinus, pilonidal sinus (disputed - may be acquired)

1. Retained foreign body - ingrown hair, suture material (most common cause of post-operative sinus)
2. Chronic infection - tuberculosis, osteomyelitis (most common cause in osteomyelitis), actinomycosis
3. Chronic inflammation - Crohn's disease
4. Malignancy - sinus may drain from an underlying tumour
5. Inadequate surgical drainage of a cavity

Pathology

• The cavity from which the sinus originates maintains an ongoing source of infection/foreign material
• This prevents healing and perpetuates the tract
• Wall of sinus lined by granulation tissue
• Chronic sinuses may become epithelialised

Clinical Features

• Persistent discharge (serous, purulent, or containing flecks of material)
• History of previous infection or abscess
• Pain may be present if infection flares
• Sinogram can delineate extent and connections

Treatment

• Directed at removing the underlying cause
• Biopsy of the wall should ALWAYS be taken to exclude malignancy or specific infection
• Surgical excision of the sinus tract (sinusectomy)
• Adequate drainage
• Treat specific infection (e.g., anti-tubercular therapy for TB sinus)
• Remove foreign body if present

Important Specific Sinuses

• Pilonidal sinus: In natal cleft; caused by ingrown hair follicles; treated by excision +/- primary closure or flap
• Branchial sinus: Remnant of 2nd branchial cleft; opens along anterior border of sternocleidomastoid
• Thyroglossal sinus: Opens in midline neck following rupture of thyroglossal cyst

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4. ULCER

Definition

Classification

• Venous ulcer (most common leg ulcer - 70%)
• Arterial (ischaemic) ulcer
• Traumatic ulcer
• Pressure ulcer (decubitus)
• Neuropathic ulcer (diabetic foot)

• Tuberculous ulcer
• Syphilitic ulcer (gumma)
• Actinomycotic ulcer
• Tropical ulcer (Meleney's synergistic gangrene)
• Marjolin's ulcer (malignant transformation in chronic scar/burn/sinus)

• Squamous cell carcinoma
• Basal cell carcinoma (rodent ulcer)
• Melanoma

Examination of an Ulcer - Clinical Features

Pathophysiology by Type

• Due to chronic venous hypertension → lipodermatosclerosis
• Site: Gaiter area (medial malleolus)
• Shallow, irregular edge, moist, fibrinous exudate
• Associated with varicose veins, DVT

• Due to atherosclerosis → ischaemia
• Site: Toes, heel, lateral malleolus (pressure points)
• Punched-out, deep, pale/necrotic base, painful
• Associated with intermittent claudication, absent pulses, cold limb

• Due to peripheral neuropathy + microvascular disease
• Site: Pressure points of foot (plantar, metatarsal heads)
• Painless despite appearance (neuropathy)
• "Punched out" surrounded by callus

• Due to sustained pressure → ischaemia and tissue necrosis
• Grading: I (intact skin, redness) → II (partial thickness) → III (full thickness) → IV (bone, tendon, muscle visible)
• Prevention key: pressure-relieving mattresses, turning, skin care

• Malignant transformation (usually SCC) in a chronic scar, burn scar, venous ulcer, or sinus
• Characteristic: slowly growing, raised, everted edge; painless (scar lacks sensation)
• Latent period: 10-25 years

Investigations

• Swab for C&S
• Ankle-Brachial Pressure Index (ABPI) - if <0.8, arterial component
• Biopsy - essential to exclude malignancy
• Blood glucose, FBC, albumin

Treatment Principles

• Treat underlying cause
• Local wound care: debridement, moist dressings
• Compression bandaging for venous ulcers (if ABPI >0.8)
• Vascular reconstruction for arterial ulcers
• Offloading for neuropathic ulcers
• Optimise nutrition (Vit C, zinc, protein), correct anaemia, prevent infection

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5. FISTULA

Definition

Classification

• Congenital: Tracheo-oesophageal fistula, branchial fistula
• Acquired:
  • Post-inflammatory: Crohn's disease, diverticulitis, tuberculosis, actinomycosis
  • Post-surgical: anastomotic leak, iatrogenic injury
  • Post-radiation
  • Malignant (tumour eroding into adjacent structure)
  • Arteriovenous (traumatic or congenital)

• Enterocutaneous (bowel to skin) - complicates Crohn's, bowel surgery
• Colocutaneous (colon to skin)
• Enterovesical (bowel to bladder)
• Rectovaginal / Vesicovaginal (obstetric, radiation, malignancy)
• Branchial (neck)
• Tracheo-oesophageal
• Arteriovenous
• Fistula-in-ano (anorectal)

• High output: >500 mL/day (small bowel)
• Low output: <200 mL/day (colon)

Causes - "FRIEND" Mnemonic (for why fistula fails to heal)

• F - Foreign body
• R - Radiation
• I - Infection / Inflammation (Crohn's)
• E - Epithelialization of the tract
• N - Neoplasm
• D - Distal obstruction

Principles of Fistula Management

• Control sepsis
• Nutritional support (TPN if high output)
• Skin protection
• Skin barrier products, stoma bags for enterocutaneous

• No distal obstruction
• No foreign body or malignancy
• No active Crohn's
• No radiation damage

• Address underlying cause
• Excise the fistulous tract
• Treat distal obstruction
• Bowel resection and reanastomosis for enterocutaneous fistulae
• Key principles of fistula surgery (Bailey & Love): eliminate the underlying cause, excise the tract, eliminate dead space, adequate blood supply at repair

Fistula-in-Ano

• Abnormal communication between anal canal/rectum and perianal skin
• Classified by Parks (relation to external sphincter): intersphincteric, transsphincteric, suprasphincteric, extrasphincteric
• Treatment: lay-open (fistulotomy) for low fistulae; seton for complex/high fistulae; LIFT (ligation of intersphincteric fistula tract) procedure

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6. BURNS

Definition

Epidemiology (Bailey & Love)

• UK: ~175,000 A&E visits/year; ~13,000 admissions; ~1,000 need fluid resuscitation
• Half the victims are under 16 years of age
• Children: predominantly scalds
• Adults: flame burns, contact burns
• Elderly: scalds, falls against hot objects

Causes of Burns

1. Thermal: Flame, scalds (most common in children), contact, flash
2. Chemical: Acid/alkali (industrial, domestic)
3. Electrical: Low voltage (<1000 V), high voltage (>1000 V), lightning
4. Radiation: UV, ionising
5. Cold: Frostbite

Assessment of Burns

A. Assessment of Burn AREA

• Corrects for age-related differences in body proportions
• At birth: head = 18%, lower limb = 13.5% each
• For each year: 1% subtracted from head, 0.5% added to each lower limb

B. Assessment of Burn DEPTH

Pathophysiology of Burn Injury

Jackson's Zones of Thermal Injury (three concentric zones)

1. Zone of coagulation (centre) - direct thermal damage, irreversible cell death
2. Zone of stasis (middle) - potentially salvageable; microvascular damage, decreased perfusion; can progress to coagulation with inadequate treatment; this zone is the key therapeutic target
3. Zone of hyperaemia (periphery) - vasodilation, inflammation; recovers with minimal treatment

The Burn Shock (Systemic Response)

• Burns >15-20% TBSA in adults, >10% in children cause systemic inflammatory response
• Massive release of inflammatory mediators: histamine, prostaglandins, cytokines
• Increased capillary permeability → massive fluid shift from intravascular to interstitial space
• Results in: hypovolaemic shock, hypoproteinaemia, haemoconcentration
• Maximum oedema at 8-12 hours post-burn; resolves at 48-72 hours

Pulmonary Complications (Inhalation Injury)

1. Supraglottic: Heat injury from hot gases → oropharyngeal/laryngeal oedema → airway obstruction (develops within hours); signs: singed nasal hairs, stridor, hoarse voice, soot in airway
2. Subglottic: Chemical injury from smoke particles and toxic gases (CO, cyanide, acrolein) → chemical tracheobronchitis, bronchospasm; symptoms: dyspnoea, wheeze, carbonaceous sputum
3. Systemic: CO poisoning; CO has 200x affinity for Hb vs. O2 → carboxyhaemoglobinaemia → tissue hypoxia; Rx: 100% oxygen

• Singed nasal hairs/eyebrows
• Burns around face/mouth
• Carbonaceous sputum
• Hoarse voice/stridor
• History of fire in enclosed space

Other Systemic Complications

• Renal: ATN from hypovolaemia; haemoglobinuria/myoglobinuria in electrical burns
• GI: Curling's ulcer (stress ulcer of duodenum); ileus; bacterial translocation; abdominal compartment syndrome from gut oedema
• Haematological: Haemolysis, thrombocytopenia, DIC in major burns
• Metabolic: Hypermetabolic state (BMR ↑ up to 200%); catabolism; hyperglycaemia
• Peripheral circulation: Circumferential full-thickness burn → coagulation of collagen fibres → loss of elasticity → tourniquet effect as limb swells → limb-threatening ischaemia; requires escharotomy

Management of Burns

Prehospital Care (First Aid)

1. Ensure rescuer safety (especially in electrical/chemical burns)
2. Stop the burning process (Stop, Drop and Roll)
3. Check for other injuries (ABC assessment)
4. Cool the burn wound:
   • Cool with tepid water (~15°C) for minimum 20 minutes
   • Effective up to 1 hour post-burn
   • Avoid ice (worsens vasoconstriction)
   • Avoid hypothermia, especially at extremes of age
5. Give oxygen (anyone in enclosed space fire)
6. Elevate burned limbs; sit patient up if airway burn
7. Analgesia

Criteria for Admission to Burns Unit (Bailey & Love Table 46.1)

• Burns >15% TBSA (adults), >10% (children and elderly)
• Full-thickness burns >5% TBSA
• Burns of special areas: face, hands, feet, genitalia, perineum, major joints
• Circumferential burns
• Chemical/electrical burns
• Inhalation injury
• Burns at extremes of age
• Burns with significant co-morbidities
• Non-accidental injury suspected

Fluid Resuscitation

4 mL × weight (kg) × %TBSA burned = total fluid in 24 hours

• Half given in first 8 hours (from time of burn, not time of admission)
• Half given in next 16 hours
• Fluid of choice: Hartmann's (Ringer's lactate)
• Urine output target: 0.5-1.0 mL/kg/hour

TBSA% × weight (kg) × 0.5 = one portion

• Six portions given over 36 hours:
  • 3 portions given 4-hourly for 12 hours
  • 2 portions given 6-hourly for 12 hours
  • 1 portion given over 12 hours
• Colloid: albumin or fresh-frozen plasma

• 100 mL/kg for first 10 kg
• 50 mL/kg for next 10 kg
• 20 mL/kg for each kg >20 kg

Wound Care

• Superficial burns: Simple non-adherent dressings; silver sulfadiazine cream or moist wound dressings; healing in 2-3 weeks
• Deep partial-thickness burns: Silver-based dressings (Mepilex Ag, Aquacel Ag); review at 5-7 days; if not healing by 21 days → skin grafting
• Full-thickness burns: Require skin grafting (split-thickness skin graft)
• Escharotomy: Required for circumferential full-thickness burns to limbs or chest; longitudinal incisions through eschar to release constriction

Surgical Management

• Tangential excision and grafting (early, within 48-72 hours of injury)
• Split-thickness skin graft (STSG): From unburned donor sites; 0.2-0.5 mm thick
• Meshing allows graft to cover larger area (up to 3:1 ratio)
• Biological dressings: Cadaver skin, amnion - temporary cover
• Dermal substitutes: Integra, Matriderm - for full-thickness burns
• Full-thickness grafts: For small areas of cosmetically/functionally important sites (face, hands)

Special Burns

• Entry and exit wounds often small but deep tissue damage (arc effect; current travels along vessels/nerves)
• Risk of cardiac arrhythmia - ECG monitoring essential
• Myoglobinuria risk → renal failure; forced alkaline diuresis
• High-voltage (>1000 V): explosive soft tissue injury, fractures, nerve/vessel injury

• Remove contaminated clothing immediately (with protection)
• Copious water irrigation for minimum 20 minutes
• Alkali burns typically deeper than acid (saponification of fat vs. protein precipitation)
• Do NOT attempt neutralisation (exothermic reaction)

• 100% O2 via non-rebreather mask
• Early intubation if airway compromise
• CO poisoning: 100% O2 (reduces CO half-life from 5 hours to 90 minutes)

Nutritional Support

• Hypermetabolic state requires aggressive nutritional support
• Early enteral feeding is preferred (within 6 hours)
• High protein, high calorie diet
• Nasogastric tube if needed

Complications

• Infection: Most common cause of death in burns patients; wound, pneumonia, catheter sepsis, bacteraemia
• Scar formation: Hypertrophic scars; treated with compression garments, silicone sheets, intralesional steroids
• Contracture: Joint contracture; requires physiotherapy and early splinting; may need surgical release
• Psychological: Depression, PTSD, body image issues

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COMPARISON TABLE: SINUS vs FISTULA vs ULCER

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