Wound Healing, Skin & Soft Tissue

Phases of Wound Healing

Types of Wound Healing

• Primary intention — clean edges approximated directly (e.g., sutured surgical wound). Minimal granulation. Fastest.
• Secondary intention — large defect heals by granulation, contraction, epithelialisation (e.g., chronic ulcer).
• Tertiary intention (delayed primary closure) — left open initially for infection control, closed surgically after 3–5 days.

Clinical Milestones

• 48 hours: epithelial seal forms over a clean surgical wound
• Day 5–7: peak tensile strength build begins from collagen
• 3 months: ~80% of original tensile strength regained

Factors Affecting Wound Healing

Nutritional Role in Healing

NPWT applies sub-atmospheric pressure (−50 to −125 mmHg) to a wound bed through a sealed dressing to promote healing.

Mechanism of Action

• Macro-deformation — wound edges drawn together by suction, reducing wound size
• Micro-deformation — mechanical stretch at cellular level stimulates fibroblast proliferation and angiogenesis
• Exudate removal — decreases oedema, bacterial load, and proteolytic enzymes
• Improved perfusion — reduces interstitial pressure, improving capillary blood flow
• Moist environment — promotes granulation and epithelialisation
• Barrier function — protects from external contamination

Indications

• Diabetic foot ulcers, pressure ulcers, venous/arterial ulcers
• Traumatic wounds: degloving injuries, open fractures, soft tissue loss
• Post-operative: wound dehiscence, infected surgical wounds
• Burns: as bridge to skin grafting
• Abdominal wound management: open abdomen / laparostomy
• Sternal wound infections post-cardiac surgery
• ciNPWT (closed incision) — prophylactic use over high-risk closed surgical incisions

Contraindications

• Malignancy in wound (promotes tumour growth)
• Untreated osteomyelitis
• Necrotic tissue with eschar (must debride first)
• Exposed vessels, anastomoses, organs without intervening tissue
• Fistulae to body cavities or organs
• Coagulopathies

Management of Keloid

• First line: Silicone gel sheets (12–24 hrs/day × 3–6 months), pressure garments
• Intralesional steroids: Triamcinolone 10–40 mg/mL, repeated every 4–6 weeks
• Surgical excision + adjuvant: Excision alone has 45–100% recurrence; must combine with steroids or radiotherapy
• Radiotherapy: Postoperative, within 24 hours of excision; reduces recurrence to <10%
• Laser: Pulsed dye laser (PDL) for vascular component; CO&sub2; laser for bulk reduction
• Cryotherapy: Freeze-thaw cycles; useful for small lesions
• Bleomycin / 5-FU intralesional: Emerging options

A chronic, recurrent, debilitating inflammatory skin condition affecting apocrine gland-bearing areas. Not primarily an infective condition — it is a follicular occlusion disease with secondary superinfection.

Pathophysiology

Follicular occlusion → retention of keratin → follicular rupture → inflammatory response in dermis → sinus tract formation → secondary bacterial colonisation (not primary infection).

Sites

Axilla (most common), groin, perianal area, inframammary folds, buttocks, perineum.

Hurley Staging

Management

• Medical: Topical clindamycin, systemic tetracyclines, rifampicin + clindamycin combination, adalimumab (anti-TNF-α — FDA approved for Hurley II/III)
• Surgical — Hurley I–II: Incision & drainage (temporary), unroofing of sinus tracts (deroofing)
• Surgical — Hurley III: Wide excision of all involved skin and subcutaneous tissue; reconstruction with split skin graft or local flap
• Laser: Nd:YAG laser hair removal reduces recurrence in Hurley I–II
• Key principle: I&D alone = high recurrence; deroofing or wide excision = definitive

Most common skin malignancy. Arises from basal cells of epidermis. Locally invasive — metastasis extremely rare (<0.1%). “Rodent ulcer” refers to the classic central ulceration with rolled pearly edges.

Types

• Nodular (most common) — pearly papule with telangiectasia; rolls over on palpation
• Superficial — erythematous plaque, multiple, trunk
• Morphoeaform / sclerosing — scar-like, ill-defined; most aggressive; highest recurrence
• Pigmented — may mimic melanoma
• Basosquamous (metatypical) — hybrid with SCC behaviour; can metastasise

Risk Stratification (NCCN)

Management

• Standard excision: Low-risk tumours — 3–5 mm margin
• Mohs micrographic surgery (MMS): High-risk, facial, recurrent — intraoperative margin analysis; lowest recurrence rate (1–2%)
• Curettage & electrodessication: Low-risk nodular on trunk/extremities only
• Topical imiquimod 5%: Superficial BCC <2 cm in non-critical areas
• Radiotherapy: Inoperable, elderly, critical sites
• Hedgehog pathway inhibitors: Vismodegib / Sonidegib — for locally advanced / metastatic BCC (PTCH1/SMO mutation → HH signalling → uncontrolled growth). Side effects: muscle cramps, alopecia, dysgeusia

Premalignant Lesions of Skin

Squamous Cell Carcinoma

• Second most common skin malignancy after BCC
• Risk factors: UV exposure, chronic wounds (Marjolin’s), immunosuppression, HPV (16/18 for anogenital SCC), arsenic, industrial carcinogens
• Features: Indurated, ulcerated lesion with everted edges; more likely to metastasise than BCC (2–5% for cutaneous SCC, higher for lip, ear, genitalia)
• Management: Wide excision (1 cm margins for low-risk, 2 cm for high-risk); sentinel lymph node biopsy for high-risk; adjuvant radiotherapy for perineural invasion or nodal disease
• Cetuximab (anti-EGFR): For advanced / metastatic cutaneous SCC not amenable to surgery

Subtypes

• Superficial spreading (most common, ~70%) — radial growth phase first; flat, irregular borders; ABCDE features
• Nodular (~15%) — vertical growth phase from outset; most aggressive; no radial phase
• Lentigo maligna — elderly, sun-damaged skin (face); Hutchinson’s freckle; slow growing
• Acral lentiginous — palms, soles, subungual; most common type in dark-skinned patients; Bob Marley’s melanoma
• Desmoplastic — rare; fibrous stroma; high local recurrence; nerve invasion common

Staging — AJCC 8th Edition (Concise)

Management

1. Excision margins by Breslow:

   In situ: 0.5–1 cm; T1 (≤1mm): 1 cm; T2 (1–2mm): 1–2 cm; T3–T4 (>2mm): 2 cm. Wider margins do not improve survival.
2. Sentinel Lymph Node Biopsy (SLNB):

   Indicated for T1b and above (≥0.8 mm with ulceration, or ≥1 mm). Uses blue dye + radioisotope. If SLN positive → completion lymph node dissection or observation with surveillance (MSLT-II trial evidence).
3. Adjuvant therapy (Stage III):

   Anti-PD-1 checkpoint inhibitors (Nivolumab, Pembrolizumab) or BRAF/MEK inhibitors (Dabrafenib + Trametinib for BRAF V600E-mutant tumours).
4. Metastatic disease (Stage IV):

   Ipilimumab (anti-CTLA-4) + Nivolumab (anti-PD-1) combination; BRAF-targeted therapy for BRAF V600E mutants. Median survival has improved from <1 year to >5 years with modern immunotherapy.

Dermatofibrosarcoma Protuberans (DFSP)

• Origin: Dermal fibroblasts; associated with COL1A1–PDGFB fusion gene (t(17;22))
• Features: Slowly growing indurated plaque → multinodular protuberant mass. Trunk most common. Locally aggressive, rarely metastasises (<5%).
• Histology: Storiform (cartwheel) pattern of spindle cells; CD34 positive, Factor XIIIa negative
• Management: Wide local excision (2–3 cm margins) or Mohs surgery; imatinib mesylate (tyrosine kinase inhibitor targeting PDGFB) for unresectable/metastatic disease

Merkel Cell Carcinoma

• Rare neuroendocrine carcinoma of skin; sun-exposed areas in elderly immunocompromised
• Aggressive — early nodal metastasis
• Associated with Merkel Cell Polyomavirus (MCPyV)
• Treatment: wide excision + SLNB ± radiotherapy; Avelumab (anti-PD-L1) for metastatic disease

Kaposi’s Sarcoma

• Vascular tumour associated with HHV-8 (Human Herpesvirus 8)
• Types: Classic (Mediterranean elderly), Endemic (African), AIDS-related (most common), Iatrogenic (post-transplant)
• AIDS-related KS: violaceous plaques/nodules; treatment includes HAART (causes regression), liposomal doxorubicin

Localised injury to skin and underlying tissue, usually over a bony prominence, caused by prolonged pressure (>capillary closing pressure of 32 mmHg) → ischaemia → necrosis.

Common Sites

• Supine: Sacrum (most common), occiput, heels, elbows, scapula
• Sitting: Ischial tuberosities, greater trochanters
• Lateral: Greater trochanters, malleoli

NPUAP/EPUAP Staging

Flap Choices for Stage IV Pressure Sores

• Sacral: Gluteus maximus musculocutaneous flap (V–Y or rotation)
• Ischial: Hamstring advancement flap, posterior thigh flap
• Trochanteric: Tensor fascia lata (TFL) flap

Prevention

• Repositioning every 2 hours
• Pressure-relieving mattresses (air-fluidised, alternating pressure)
• Nutrition: protein 1.25–1.5 g/kg/day, Vitamin C, zinc
• Risk scoring: Braden scale / Norton scale / Waterlow scale

STSG Thickness Classification

• Thin (0.008–0.012″): better take, poor durability
• Intermediate (0.012–0.018″): most commonly used
• Thick (0.018–0.030″): poor take, best durability & cosmesis

Phases of Graft Take

1. Plasmatic imbibition (0–48 hrs): Graft absorbs nutrients from wound bed (avascular)
2. Inosculation (48–72 hrs): Capillary buds from recipient connect to graft vessels
3. Revascularisation (Day 3–5): Blood flow re-established
4. Maturation: Graft fully incorporated; adnexal structures may regenerate in FTSG

Causes of Graft Failure

• Haematoma / seroma under graft (most common) — prevents vascular ingrowth
• Infection (especially β-haemolytic Streptococcus — destroys graft at <10&sup5; organisms/gram)
• Movement / shear forces (loss of contact)
• Poor recipient bed (avascular: bone, tendon without periosteum/perichondrium, irradiated tissue)

Classification by Blood Supply

Reconstructive Ladder

Always start with the simplest option that gives adequate reconstruction.

Common Flaps by Indication

Transfer of a patient’s own adipose tissue from a donor site (abdomen, thighs, flanks) to a recipient site for volume restoration or contour correction. Also known as fat grafting or lipotransfer.

Reconstructive Indications

• Breast reconstruction — post-lumpectomy contour correction, post-mastectomy volume restoration
• Post-radiation soft tissue fibrosis
• Facial lipoatrophy (trauma, aging, HIV-related)
• Scar revision and skin quality improvement
• Contour deformities (post-traumatic, post-liposuction, congenital)

Technique (Coleman Technique)

1. Harvesting: Low-pressure liposuction (hand syringe) to minimise fat cell trauma
2. Processing: Centrifugation at 3000 rpm × 3 minutes to separate fat, oil, and blood
3. Injection: Small aliquots (<0.1 mL per pass) in multiple planes in a “fan” pattern to maximise surface area contact for revascularisation

Key Points

• Graft survival rate: 40–60% (variable; some volume loss expected)
• Adipose-derived stem cells (ADSCs) in fat graft may enhance regeneration and angiogenesis
• Contraindicated if malignancy at recipient site
• Must not inject in large boluses — central necrosis occurs