Skin Grafting: Complete Overview

Definition

Types of Skin Grafts

Indications

1. Wound Coverage (Most Common)

• Burns (deep partial-thickness and full-thickness burns) - early excision and grafting reduces infection risk and healing time
• Traumatic wounds with skin loss too large for primary closure or secondary intention healing
• Chronic non-healing ulcers (venous, diabetic, pressure ulcers) after adequate debridement

2. Reconstructive Indications

• Skin defects after tumor excision (e.g., basal cell carcinoma, squamous cell carcinoma, melanoma) - particularly when the defect is too large to close primarily but not large enough to warrant a free flap
• Reconstruction after mastectomy or other cancer resections
• Soft tissue defects over periosteum, fascia, or muscle that cannot be closed primarily
• Orbital exenteration defects (where a prosthesis will be placed)
• Maxillectomy defects (with palatal obturators)
• Flap donor site closure (e.g., radial forearm flap or fibula flap harvest sites)
• Granulating wounds as a delayed second-stage closure after initial healing

3. Specific Clinical Situations

• Patients medically unfit for prolonged anesthesia required for free flap reconstruction
• Pediatric burns - scalp is an excellent donor site
• Areas requiring coverage after contracture release
• Coverage of exposed healthy periosteum or perichondrium (e.g., upper two-thirds of nose using FTSG)
• Patients requiring staged reconstruction where the wound is first granulated, then grafted

Contraindications

Absolute Contraindications (Recipient Site)

• Exposed avascular bone without periosteum - no vascular bed to support graft
• Exposed tendon without paratenon
• Exposed cartilage
• Heavily irradiated tissue (poor vascularity)
• Active infection or heavy bacterial colonization - wounds containing >10⁵ organisms per gram of tissue will not support a graft; specific organisms that destroy fibrin and prevent adherence include:
  • Streptococcus pyogenes (beta-hemolytic streptococci are particularly destructive)
  • Pseudomonas aeruginosa
  • MRSA

Relative Contraindications / Unfavorable Conditions

• Fat as recipient bed - less vascular than muscle/fascia, poor take
• Exposed peritoneum or major blood vessels - risk of compromise if graft fails
• Systemically unfit patients with coagulopathy (high hematoma risk)
• Active malignancy in wound bed - graft will not address underlying disease

Systemic Factors That Impair Graft Take

• Diabetes mellitus
• Smoking
• Prior radiotherapy or chemotherapy to the area
• Malnutrition / poor nutritional status

Steps of Skin Grafting

Pre-operative

1. Assess and prepare the recipient site - complete debridement of necrotic tissue, control of infection, and achievement of a viable wound bed (granulation tissue, healthy muscle, or fascia)
2. Donor site selection - choose a cosmetically concealed area; options include inner thigh (most common), scalp (excellent for large burns - heals with no alopecia), back, buttock
3. Mark both sites - measure the defect, mark the donor site area accordingly
4. Patient counseling - donor site will create an additional permanent scar

Intraoperative

A. Harvesting the Graft (STSG)

1. Infiltrate donor site subcutaneously with physiologic saline to create a flat harvestable surface
2. Apply mineral oil to the skin surface to lubricate
3. Assistant holds skin taut with gauze or towel clamp
4. Set electric/air-powered dermatome to 0.2-0.3 mm (0.008-0.012 inches) - set between 6/1000 and 12/1000 inch; verify the gap manually with a #15 blade
5. Hold dermatome at 45-60 degrees to the skin surface; activate before skin contact
6. Advance with consistent, gentle pressure and forward motion across the width of the blade
7. After harvest: donor site should show light punctate bleeding (papillary dermis level) - fat lobules must NOT be visible
8. Hemostasis at donor site: epinephrine-soaked gauze (1:10,000 to 1:20,000)

B. Processing the Graft

• Pie-crusting: make small perforations with a #15 blade or needle to prevent hematoma collection
• Meshing: pass through a mesh carrier for large defects - ratios of 1:1.5, 1:2, 1:3, 1:6, or 1:9; meshing promotes drainage and allows expansion to cover larger areas; standard of care for large burns
• Avoid meshing on aesthetically important areas (face, hands) as mesh pattern becomes visible scarring

C. Applying the Graft

1. Achieve meticulous hemostasis of recipient bed
2. Apply graft dermis side down onto the wound bed
3. Place under mild tension - attach one edge, pull/stretch toward opposite edge; trim to fit with an ideal 1-2 mm gap from wound edge to graft
4. Graft must contact the wound bed completely
5. Orient graft seams perpendicular to biodynamic skin tension lines, respecting aesthetic units
6. Fix with staples, non-absorbable sutures (Prolene - especially hands and face), thrombin/cyanoacrylate glue; absorbable sutures are avoided as they cause inflammatory granulomas

D. Dressing

1. Apply a non-adherent (low-adherent) dressing (e.g., Adaptic, Jelonet) directly on the graft
2. Apply a bolster or tie-over dressing, or negative pressure wound therapy (NPWT/VAC) to:
   • Eliminate dead space
   • Prevent shear forces
   • Promote graft-bed contact
3. Immobilize the area for 3-7 days (critical phase of revascularization)

Postoperative

• First dressing change at 3-5 days (after initial adherence)
• Monitor for hematoma, seroma, infection
• Ongoing immobilization until graft is secure
• Compression garments for burn scar management after full healing

Stages of Graft Acceptance ("Take")

Stage 1 - Graft Adherence (Immediate)

• The graft adheres immediately through a thin fibrin layer
• Within 48 hours, fibrin begins breaking down; adhesion is then maintained by fibroblast proliferation and collagen deposition
• No blood flow to the graft yet; graft appears pale

Stage 2 - Serum Imbibition (0 to 48 hours)

• The graft survives by absorbing nutrients from plasma leaking out of capillaries in the recipient bed
• The graft gains weight and swells during this phase
• This is entirely passive diffusion - the graft has NO active circulation
• This phase is transient; the graft cannot survive on imbibition indefinitely

Stage 3 - Revascularization (48 hours to 3 weeks)

• Graft begins to appear pink/red as circulation is restored
• This is the most critical phase; shear forces and fluid collections (hematoma/seroma) during this phase = graft failure
• Complete by approximately 3 weeks

Stage 4 - Remodelling (3 weeks to 1 year)

• Collagen reorganization, increasing graft strength and durability
• Pigmentation normalizes (partially)
• Sensory recovery occurs (better in FTSG than STSG)
• Secondary contraction occurs (myofibroblast activity in wound bed) - more pronounced in STSG

Summary Table: STSG vs FTSG

Causes of Graft Failure (Summary)

1. Hematoma or seroma (most common) - separates graft from bed, blocks revascularization
2. Infection (>10⁵ organisms/gram) - destroys fibrin, prevents adherence
3. Shear forces - disrupt forming vascular connections
4. Poor recipient bed - exposed bone, tendon, irradiated tissue
5. Systemic factors - diabetes, smoking, poor nutrition, steroids