Skin Grafts
Summary
A skin graft is the transfer of skin (Epidermis ± Dermis) from a donor site to a recipient site (Wound bed) to achieve wound coverage. Skin grafts are used when primary wound closure is not possible, or when healing by secondary intention would result in unacceptable scarring or function. There are two main types: Split-Thickness Skin Grafts (STSG) – containing epidermis + partial dermis, and Full-Thickness Skin Grafts (FTSG) – containing epidermis + entire dermis. STSGs are harvested with a dermatome and can cover large areas; FTSGs are harvested with a scalpel from areas of skin laxity and are used for cosmetically sensitive areas (Face, Hands). Graft survival depends on a well-vascularised recipient bed and immobilisation to allow revascularisation (Inosculation → Neovascularisation). Key causes of graft failure include haematoma/seroma, infection, and shear. Understanding the indications, techniques, and aftercare of skin grafts is essential for surgical exams. [1,2]
Clinical Pearls
"STSGs Contract, FTSGs Minimise Contraction": STSG undergoes more secondary contraction (Scarring). FTSG has more dermis → Less contraction. Use FTSG for hands, face, crossing joints.
"Graft Bed Must Be Healthy": Grafts will NOT take on avascular tissue (Bone without periosteum, Cartilage without perichondrium, Tendon without paratenon, Irradiated tissue).
"Seroma/Haematoma Kills Grafts": Fluid under the graft lifts it off the bed → Prevents revascularisation → Graft failure. Meshing/Quilting sutures help.
"Tie-Over Dressing": Classic technique to immobilise FTSG. Sutures tied over cotton wool bolster to prevent shear and ensure graft-bed contact.
Indications for Skin Grafts
| Indication | Notes |
|---|---|
| Burns | Most common use. STSG for large burns. Early excision and grafting improves outcomes. |
| Traumatic Wounds | Wounds too large for primary closure. |
| Post-Surgical Defects | After tumour excision (Skin cancer, Melanoma). |
| Chronic Wounds/Ulcers | Venous leg ulcers, Diabetic ulcers (After wound bed preparation). |
| Contracture Release | Burn scar contractures. FTSG preferred to minimise re-contraction. |
| Reconstruction | Resurfacing after flap failure or tissue loss. |
Split-Thickness Skin Graft (STSG)
| Feature | Notes |
|---|---|
| Composition | Epidermis + Partial Dermis (0.2-0.4mm thickness). |
| Harvest | Dermatome (Power or Hand). Thigh, Buttock, Back common donor sites. |
| Donor Healing | Heals by RE-EPITHELIALISATION from dermal appendages (Sebaceous glands, Hair follicles). 2-3 weeks. |
| Area Coverage | Can cover LARGE areas. |
| Meshing | Can be meshed (1:1.5 to 1:6 expansion). Allows drainage of fluid and covers larger areas. |
| Contraction | MORE secondary contraction (Less dermis). |
| Appearance | May have "meshed pattern" appearance. Less aesthetic. |
| Uses | Burns (Large area), Leg ulcers, Temporary wound coverage. |
Full-Thickness Skin Graft (FTSG)
| Feature | Notes |
|---|---|
| Composition | Epidermis + ENTIRE Dermis. |
| Harvest | Scalpel excision from areas of laxity (Groin crease, Postauricular, Supraclavicular, Inner arm). Donor closed primarily. |
| Donor Healing | Requires PRIMARY CLOSURE (As no dermis left to re-epithelialise). |
| Area Coverage | LIMITED by donor availability and need for primary closure. |
| Meshing | NOT meshed (Would defeat the purpose of cosmesis). |
| Contraction | LESS secondary contraction (Full dermis). |
| Appearance | Better colour/texture match. More aesthetic. |
| Uses | Face, Eyelids, Hands, Fingers, Crossing joints. |
Summary Table
| Feature | STSG | FTSG |
|---|---|---|
| Thickness | Thin (Partial dermis) | Thick (Full dermis) |
| Donor Healing | Re-epithelialisation | Primary closure required |
| Take Rate | Higher (Less metabolic demand) | Lower (More demanding) |
| Contraction | MORE | LESS |
| Aesthetics | Poorer | Better |
| Coverage | Large areas | Limited areas |
| Primary Indication | Burns, Ulcers | Face, Hands, Joints |
Skin Layers
| Layer | Components |
|---|---|
| Epidermis | Keratinocytes, Melanocytes. Avascular. |
| Dermis | Collagen, Elastin, Blood vessels, Nerves, Appendages (Hair follicles, Sweat/Sebaceous glands). |
| Hypodermis (Subcutis) | Fat. NOT included in grafts. |
Graft Take (Revascularisation)
| Phase | Timing | Mechanism |
|---|---|---|
| Plasmatic Imbibition | Days 1-2 | Graft absorbs plasma from wound bed by diffusion. Provides nutrients. |
| Inosculation | Days 2-4 | Direct anastomosis of graft vessels with recipient bed vessels (Duct-to-duct connection). |
| Neovascularisation | Days 4-7 | Ingrowth of new vessels from recipient bed into graft. True vascularisation. |
| Maturation | Weeks-Months | Nerve ingrowth (Some sensation returns), Pigmentation changes, Contraction. |
Must Have...
| Requirement | Notes |
|---|---|
| Vascularised Bed | Grafts will NOT take on avascular tissue. |
| Clean/Granulating Wound | Free of infection, Necrotic tissue. May need wound bed preparation (Negative Pressure Wound Therapy). |
| Adequate Haemostasis | Haematoma = Graft failure. |
| Minimal Exudate | Excessive exudate lifts graft off. |
Grafts Will Fail On...
| Surface | Reason |
|---|---|
| Bare Bone (Without Periosteum) | Avascular. |
| Bare Cartilage (Without Perichondrium) | Avascular. |
| Bare Tendon (Without Paratenon) | Avascular. |
| Irradiated Tissue | Poor vascularity. |
| Infected Wound | High bacterial load prevents take. |
STSG Harvesting
- Preparation: Lubricate donor site (Paraffin/Saline). Mark boundaries.
- Dermatome Setting: Adjust thickness (Typically 0.012-0.018 inches / 0.3-0.45mm).
- Harvesting: Apply even pressure and smooth motion. Skin adheres to blade.
- Processing: May mesh using skin mesher (Expand 1:1.5, 1:3, 1:6).
- Application: Apply graft to recipient, Dermal side down. Staple/Suture edges.
- Dressing: Non-adherent layer + Foam/Cotton wool + Compression.
FTSG Harvesting
- Template: Create template of defect using suture pack foil.
- Site Selection: Postauricular, Groin crease, Supraclavicular (Match colour/thickness to defect).
- Excision: Scalpel excision of ellipse including full dermis.
- Defatting: Remove all subcutaneous fat from deep surface (Improves revascularisation).
- Primary Closure: Close donor site directly (Subcuticular).
- Inset: Suture graft into defect.
- Tie-Over Dressing: "Bolster" – Suture ends left long, Tied over cotton wool to immobilise graft and ensure bed contact.
Management Algorithm (Aftercare)
SKIN GRAFT APPLIED
↓
IMMOBILISATION (Critical for Take)
- Limb splintage if over joint
- Patient education: Avoid shear/manipulation
- Tie-over dressing kept in place 5-7 days
↓
FIRST DRESSING CHECK (Day 5-7)
- Remove outer dressings carefully
- Assess graft take
- Look for haematoma/seroma/infection
↓
GRAFT TAKE?
┌────────────────┴────────────────┐
SUCCESSFUL FAILED/PARTIAL
↓ ↓
Resume mobilisation Identify cause
Moisturise graft - Haematoma: Evacuate
Sun protection - Infection: Antibiotics
Compression if limb - Consider re-grafting
Factors Affecting Graft Take
| Factor | Impact |
|---|---|
| Haematoma/Seroma | Lifts graft off bed. Most common cause of failure. |
| Infection | Bacteria destroy graft. Strep/Pseudomonas particularly problematic. |
| Shear/Movement | Disrupts inosculation. Immobilisation critical. |
| Poor Recipient Bed | Avascular tissue, Irradiated tissue. |
| Tight Dressings | Ischaemia of graft. |
| Patient Factors | Smoking, Diabetes, Malnutrition, Immunosuppression. |
Donor Site Care
| Type | Care |
|---|---|
| STSG Donor | Semi-occlusive dressing (Allevyn, Mepitel). Heals in 2-3 weeks. Keep moist. May scar. |
| FTSG Donor | Closed primarily. Standard wound care. Suture removal 7-14 days. |
Graft Complications
| Complication | Notes |
|---|---|
| Graft Failure/Loss | Haematoma, Seroma, Infection, Shear. May need re-grafting. |
| Contraction | Secondary (Myofibroblast-mediated). Worse with STSG. Problematic across joints. |
| Abnormal Pigmentation | Hypo/Hyperpigmentation. May improve over months. |
| Abnormal Sensation | Some nerve regrowth. May have altered sensation/hyperaesthesia. |
| Poor Cosmesis | Meshed pattern, Colour mismatch, Texture difference. |
Donor Site Complications
| Complication | Notes |
|---|---|
| Pain | STSG donor sites are painful (Exposed nerve endings). |
| Delayed Healing | Infection, Poor nutrition, Diabetes. |
| Hypertrophic Scarring | Especially if donor re-harvested from same site. |
| Infection | Keep dressings clean. Monitor for signs. |
| Factor | Notes |
|---|---|
| Graft Take Rate | STSG: ~95%. FTSG: ~85-90% (When conditions optimal). |
| Cosmesis | FTSG > STSG. FTSG better colour/texture match. |
| Contraction | STSG contracts 10-40%. FTSG contracts 5-10%. |
| Functional Outcome | Depends on location and contraction. May need release and re-grafting if contracture limits function. |
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Burns Guidelines | British Burns Association | Early excision and grafting. Wound bed preparation. |
| Wound Management | NICE | NPWT for complex wounds. Graft for non-healing ulcers. |
Evidence Points
- Early Burn Excision: Reduces sepsis, Improves survival, Shortens hospital stay.
- Meshed vs Sheet STSG: Meshed allows drainage and expansion, but poorer cosmesis.
- FTSG for Hands/Face: Standard of care for cosmesis and function in these areas.
What is a Skin Graft?
A skin graft is a piece of healthy skin taken from one part of your body (The "donor site") and transplanted to cover a wound or defect elsewhere (The "recipient site"). It is used when a wound is too large to close directly or when letting it heal naturally would lead to bad scarring.
What are the types?
- Split-Thickness Graft: A thin layer of skin. Can cover large areas. Donor site heals like a graze.
- Full-Thickness Graft: A thicker piece of skin. Better for face or hands. Donor site needs stitches.
How does it stick?
The graft doesn't have its own blood supply initially. It survives by absorbing fluid from the wound bed, then tiny blood vessels grow into it over the first week. This is why keeping it still and protected is so important.
What can go wrong?
The main risks are:
- Blood or fluid collecting under the graft (Lifts it off).
- Infection.
- Movement (Disrupts the new blood vessel connections). If the graft fails, it may need to be redone.
What about scarring?
- Grafted areas often look different from surrounding skin (Colour, Texture).
- Full-thickness grafts look more natural than split-thickness.
- Moisturising and sun protection help improve appearance over time.
Primary Sources
- Gurtner GC, et al. Wound repair and regeneration. Nature. 2008;453(7193):314-321. PMID: 18480812.
- Wysocki AB. Skin anatomy, physiology, and pathophysiology. Nurs Clin North Am. 1999;34(4):777-797. PMID: 10496400.
Common Exam Questions
- Difference STSG vs FTSG: "What is the main structural difference?"
- Answer: STSG = Epidermis + Partial Dermis. FTSG = Epidermis + Full Dermis.
- Contraction: "Which graft contracts more?"
- Answer: STSG (Less dermis → More secondary contraction).
- Graft Take Failure Cause: "What is the most common cause of graft failure?"
- Answer: Haematoma/Seroma (Lifts graft off bed, prevents revascularisation).
- Avascular Surfaces: "What surfaces will a graft NOT take on?"
- Answer: Bone without periosteum, Cartilage without perichondrium, Tendon without paratenon.
Viva Points
- Plasmatic Imbibition → Inosculation → Neovascularisation: The 3 phases of graft take.
- Meshing: Allows drainage (Prevents haematoma), Expands coverage, BUT poorer cosmesis.
- Tie-Over Dressing: Cotton wool bolster tied over FTSG for immobilisation.
- FTSG Defatting: All fat must be removed from deep surface to allow revascularisation.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.