Skin Grafting

Skin grafting is the transfer of epidermis with varying amounts of dermis from a donor site to a recipient bed, detached from its blood supply. It covers defects that cannot be closed primarily or left to heal by secondary intention.

Types

• Split-thickness skin graft (STSG): epidermis and part of the dermis, thickness 0.2 to 0.4 mm (thin 0.15 to 0.3 mm, intermediate 0.3 to 0.45 mm, thick 0.45 to 0.6 mm). Donor site heals by re-epithelialisation from adnexal structures in 7 to 14 days. Thin grafts take better but contract more. Can be meshed (1.5:1 to 6:1) to expand coverage and allow drainage.
• Full-thickness skin graft (FTSG): epidermis and entire dermis. Better colour, texture match and less contraction, but needs a well-vascularised bed. Donor sites are closed primarily (postauricular, supraclavicular, upper eyelid, groin, antecubital fossa).
• Composite graft: skin with cartilage or fat (nasal alar rim defects from auricular helical rim).
• Cultured epithelial autografts, dermal substitutes (Integra, Matriderm), epidermal suspensions (ReCell), allografts (cadaver), xenografts (porcine) and amnion used as temporary or adjunct cover, especially in major burns.

Indications

Burns (excised to viable bed), traumatic wounds, chronic ulcers (venous, pressure, diabetic) after optimisation, skin cancer excision defects, necrotising infection debridement, donor site coverage for flaps, vitiligo surgery, and reconstructive surgery (contracture release, cleft lip, vaginoplasty lining).

Graft take (survival) phases

• Plasmatic imbibition (first 24 to 48 hours): nutrition by diffusion from wound fluid.
• Inosculation (days 2 to 4): alignment of graft and host capillaries.
• Revascularisation (days 4 to 7): ingrowth of new vessels. Lymphatic reconnection by day 5 to 7.
• Maturation and contraction (weeks to months): primary contraction (immediate elastic recoil, greater in FTSG) and secondary contraction (myofibroblast-mediated, greater in thin STSG).
• Requirements for take: a vascularised bed (granulation tissue, muscle, paratenon, perichondrium, periosteum), immobilisation, intimate contact (no haematoma, seroma), absence of infection (below 10^5 organisms/g, no beta-haemolytic streptococci), and adequate host nutrition.
• Poor recipient beds: exposed bone without periosteum, cartilage without perichondrium, tendon without paratenon, irradiated tissue, and necrotic or infected tissue.

Assessment before grafting

• Defect size, depth, site, vascularity of bed, infection, functional and cosmetic demands, patient comorbidities (diabetes, vascular disease, smoking, steroids, malnutrition, anticoagulation).
• Donor site availability: thigh (most common), scalp (rapid healing, useful in children and for repeated harvest), buttock, abdomen, and back. Avoid scarred or irradiated skin.

Postoperative course and findings

• Normal: graft initially pale, becoming pink by day 3 to 5 as circulation is restored, with dusky purple or bluish tone being acceptable early (venous congestion). Pale sheen persists for weeks.
• Complications:
  • Haematoma or seroma beneath graft (most common cause of failure), appears as fluctuant blister and lifts graft.
  • Infection (purulence, odour, green discoloration with Pseudomonas, melting graft with beta-haemolytic streptococcus).
  • Shear and movement causing graft loss.
  • Graft contracture, hypertrophic scarring, pigmentation changes (hyperpigmentation commonly), hair growth in grafts (FTSG), and poor sensation.
  • Donor site pain, delayed healing, infection, hypertrophic scarring, and colour mismatch.
  • Marjolin ulcer or malignant change in chronic graft sites (rare).

Red flags: expanding blister under the graft, fever, spreading cellulitis, blackened graft, and donor site infection.

• Clinical assessment of the recipient bed and graft viability.
• Wound bed assessment: healthy red granulation, no slough, no exposed avascular structures. Quantitative bioburden: swab or tissue culture (excluding beta-haemolytic Streptococcus), as needed.
• Preoperative investigations: CBC, glucose and HbA1c, albumin, coagulation, ankle brachial index for lower limb wounds, perfusion assessment (transcutaneous oxygen), and radiographs for osteomyelitis.
• Biopsy of chronic ulcers before grafting to exclude malignancy.
• Postoperative graft take assessment at first dressing change (day 3 to 5): percentage of take, haematoma, seroma, infection. Failure less than 90% take suggests need for regrafting.
• Serial measurement of contracture and range of movement over months.

Preoperative optimisation

• Prepare the recipient bed: debride to healthy bleeding tissue, control infection (antibiotics only for clinical infection or beta-haemolytic Streptococcus), and condition with negative pressure therapy, dermal templates or temporary dressings when the bed is not ready.
• Stop smoking, control glucose, improve nutrition (protein 1.5 g/kg/day), correct anaemia, and optimise arterial supply. Withhold anticoagulants as appropriate.
• Prophylaxis: cefazolin 2 g IV within 60 minutes of incision for contaminated or large wounds. Tetanus cover.

Harvesting

• Donor site infiltrated with tumescent saline or adrenaline (1:200,000 in saline) and lidocaine 1% (maximum 7 mg/kg with adrenaline) to tense the skin and reduce bleeding. Dermatome (air or electric, setting 0.2 to 0.4 mm, or Humby knife). Meshing as required. Harvest a width and length with a margin to allow contraction.
• FTSG harvested with scalpel, defatted, and the donor site closed primarily.

Application and fixation

• Place graft on haemostatic bed, dermal side down, with edges sutured or stapled (absorbable fast sutures in children), and secure with tie-over bolster dressing (for FTSG and uneven surfaces), negative pressure dressing at 75 to 125 mmHg (improves take on complex beds, extremities, burns, and reduces shear), fibrin sealant, or non-adherent contact layer with compressive dressing.
• Splint the limb or joint to immobilise for 5 to 7 days (up to 10 for lower limbs). Elevate the limb and keep non-weight bearing.

Postoperative care

• First dressing change on day 3 to 5 (earlier if infection or haematoma suspected). Evacuate haematoma or seroma by rolling with a cotton-tipped applicator, pricking blebs, and re-applying.
• Resume gentle mobilisation at 7 to 10 days. Avoid shearing and pressure until fully stable (10 to 14 days). Compression garments for 6 to 12 months and silicone, massage, and moisturisation once healed to limit hypertrophic scars and contracture. Sun protection for at least 12 months to prevent hyperpigmentation.
• Analgesia: paracetamol 1 g every 6 hours, NSAIDs short term, and opioids for severe pain. Gabapentin 300 mg at night for neuropathic donor site pain.
• Donor site management: occlusive or semi-occlusive dressings (alginate, hydrofibre, silver foam, polyurethane film) left undisturbed until they separate, healing in 7 to 14 days. Prevents infection and pain. Avoid gauze that adheres. Local anaesthetic infusion catheters or topical lidocaine reduce pain.
• Nutrition, glucose control, and DVT prophylaxis as appropriate.

Graft failure and complications

• Partial loss: dressings, secondary intention healing, or regrafting after bed preparation.
• Infection: culture-directed antibiotics (flucloxacillin 500 mg to 1 g four times daily; penicillin V 500 mg four times daily for beta-haemolytic Streptococcus; ciprofloxacin or ceftazidime for Pseudomonas) and topical antiseptics (acetic acid 0.5 to 1%, silver sulfadiazine 1% for burns).
• Contracture: splinting, physiotherapy, steroid injection, laser, Z-plasty, release and regrafting with FTSG, or flap reconstruction.
• Hypertrophic scars and keloids: silicone, pressure, triamcinolone 10 to 40 mg/mL injection, pulsed dye laser, fractional CO2 laser.
• Pigmentation: sunscreen, hydroquinone 4% (where appropriate), laser.

Burn-specific considerations

Early tangential excision with autografting within 3 to 5 days for deep burns. Meshed STSG 3:1 for large areas with cadaveric allograft overlay (Meek technique for very large burns), sheet grafts for face, hands and joints. Dermal substitutes for functional areas, and cultured epithelial autografts in massive burns.

Follow-up

Review at 1 to 2 weeks, then monthly to 3 months, 6 months and 12 months. Observe for contracture, scars, pigmentation, sensory recovery, and skin cancer in long-standing grafts.