Split-Thickness Skin Grafts: Technique & Indications
Split-thickness skin grafts (STSGs) include the epidermis and a variable portion of the dermis, classified as thin (0.005-0.012 in), intermediate (0.012-0.018 in), or thick (0.018-0.030 in). Their lower metabolic demand yields take rates of 90-95% on adequate wound beds, significantly higher than FTSGs. STSGs are the graft of choice for large defects, poorly vascularized recipient beds, and staged reconstructive procedures in dermatologic surgery.
By Dr. Yehonatan Kaplan (M.D., Fellow ACMS)·Published: 2026-04-08·Updated: 2026-04-08·Reviewed: 2026-04-08
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Key Takeaways
- STSGs achieve 90-95% take rates compared to 80-85% for FTSGs, making them the preferred graft for poorly vascularized or large wound beds.
- Graft thickness classification: thin (0.005-0.012 in), intermediate (0.012-0.018 in), thick (0.018-0.030 in) — thinner grafts take better but contract more (up to 50% for thin STSGs).
- Sheet (unmeshed) grafts are preferred for any cosmetically sensitive area; meshed grafts leave a permanent visible pattern.
- Donor sites heal by re-epithelialization from adnexal structures in 10-21 days; moist wound dressings reduce healing time by 30-40% versus dry gauze.
- Lower extremity grafting requires strict leg elevation for 7-14 days postoperatively, compression therapy, and preoperative venous stasis optimization.
- Negative pressure wound therapy (wound VAC) improves STSG take rates by 10-15% on challenging wound beds compared to standard bolster dressings.
Definition and Thickness Classification
A split-thickness skin graft (STSG) consists of the entire epidermis and a partial layer of the underlying dermis. The thickness of dermis included determines the graft classification and directly affects clinical behavior. Thinner grafts have lower metabolic requirements and higher take rates but undergo greater secondary contraction and produce poorer cosmetic outcomes. Thicker grafts approach FTSG behavior with better color match and less contraction but demand stronger recipient bed vascularity.
| Classification | Thickness (inches) | Thickness (mm) | Take Rate | Secondary Contraction | Cosmesis | Primary Use |
|---|---|---|---|---|---|---|
| Thin (Thiersch) | 0.005-0.012 | 0.13-0.30 | 95%+ | Marked (up to 50%) | Poor — shiny, dysplastic | Temporary coverage, leg ulcers, burns |
| Intermediate | 0.012-0.018 | 0.30-0.46 | ~90% | Moderate (20-30%) | Acceptable | Most dermatologic surgery applications |
| Thick | 0.018-0.030 | 0.46-0.76 | ~85% | Mild (10-15%) | Good — approaches FTSG | Facial defects when FTSG not feasible |
Indications in Dermatologic Surgery
STSGs serve specific roles in dermatologic surgery when FTSGs or local flaps are not optimal. The primary advantage over FTSG is the ability to cover larger surface areas and survive on less vascular beds. STSGs are not first-line for most facial Mohs defects due to cosmetic limitations, but they are indispensable in certain clinical scenarios.
STSG Versus FTSG: Head-to-Head Comparison
Choosing between STSG and FTSG depends on recipient bed vascularity, defect size, anatomical location, and cosmetic expectations. Neither graft type is universally superior; each has specific clinical niches.
| Parameter | STSG | FTSG |
|---|---|---|
| Graft composition | Epidermis + partial dermis | Epidermis + full dermis |
| Take rate | 90-95% | 80-85% |
| Primary contraction | Minimal | Moderate (elastic fiber recoil) |
| Secondary contraction | Significant (up to 50% thin) | Minimal (5-10%) |
| Color match | Poor to moderate | Excellent |
| Texture match | Shiny, smooth | Matches native skin |
| Adnexal structures | None (thin) to partial (thick) | Fully preserved |
| Metabolic demand | Low | High |
| Maximum defect size | Unlimited (donor reharvest possible) | Limited by donor site closure |
| Donor site healing | Re-epithelialization (10-21 days) | Primary closure (sutured) |
| Donor morbidity | Moderate — pain, scarring, delayed healing | Low — linear scar |
| Best indication | Large wounds, poor vascularity, staged | Facial defects, small-moderate wounds |
Harvesting Technique
STSG harvesting requires a dermatome to create a uniform-thickness skin sheet from the donor site. Both powered (electric or pneumatic) and manual (Weck or Humby knife) dermatomes are used. The choice depends on graft size, surgeon preference, and available equipment.
Dermatome Types
Electric dermatomes (Zimmer, Padgett) produce the most uniform graft thickness and are standard for large grafts. The Weck (Goulian) hand-held dermatome uses disposable blades with adjustable guard plates and is practical for smaller grafts in office-based dermatologic surgery. The Humby knife is a manual instrument for larger harvests but requires significant operator skill to maintain consistent thickness. For most Mohs surgery settings, the Weck dermatome is the preferred instrument due to its portability, ease of use, and suitability for moderate-sized grafts.
Donor Site Preparation and Harvest Steps
The donor site skin is prepared with a thin layer of mineral oil or sterile surgical lubricant to reduce friction and allow smooth dermatome gliding. The skin must be taut during harvest. An assistant applies counter-traction by pressing firmly with tongue depressors or a flat board proximal and distal to the harvest path. The dermatome is advanced with steady, even pressure at a consistent angle (approximately 30-45 degrees to the skin surface). The graft peels up ahead of the blade as the dermatome advances. Once the desired graft length is obtained, the dermatome is angled upward to release the graft. The harvested graft is placed dermal side down on saline-moistened gauze.
Donor Site Selection
The anterior and lateral thigh are the most common donor sites for STSG, offering large flat surfaces ideal for dermatome harvest. The upper arm (lateral surface) is an alternative for smaller grafts. The abdomen can be used but has more variable thickness. For scalp defects specifically, the contralateral scalp can serve as a donor with excellent color match. Donor sites should be chosen on areas that can be concealed by clothing when possible.
Donor Site Management
STSG donor wounds heal by re-epithelialization from residual adnexal structures (hair follicles, eccrine ducts) in the remaining partial dermis. This process takes 10-21 days depending on graft thickness: thin STSG donor sites heal in 10-14 days, while thick STSG donors may require 18-21 days. Donor site pain is often reported as more bothersome than the graft recipient site, making donor wound management a priority.
| Dressing Type | Advantages | Disadvantages | Change Frequency |
|---|---|---|---|
| Calcium alginate | Highly absorbent, promotes moist healing, easy removal | May dry out and adhere if exudate decreases | Every 2-3 days or when saturated |
| Hydrocolloid (DuoDERM) | Maintains moist environment, reduces pain, waterproof | May cause maceration, opaque (cannot monitor) | Every 5-7 days |
| Foam dressings | Absorbent, cushioning, non-adherent | Requires secondary fixation | Every 2-3 days |
| Petrolatum gauze + dry gauze | Widely available, inexpensive | Adherent, painful removal, slower healing | Daily |
| Transparent film (Tegaderm) | Allows visual monitoring, waterproof | Limited absorption, fluid pooling | When fluid accumulates |
Graft Application and Bolster Technique
Successful STSG placement requires a prepared wound bed, meticulous hemostasis, and secure graft fixation. The principles mirror FTSG application with modifications for the thinner graft.
Wound Bed Preparation
The recipient wound must have adequate vascularity, be free of necrotic tissue, and achieve complete hemostasis before graft placement. For exposed calvarium, burring the outer cortical table with a high-speed drill until punctate bleeding from diploic veins is seen creates a vascular bed capable of supporting STSG take. Granulation tissue is an excellent STSG bed. Chemical or sharp debridement of fibrinous material improves graft contact.
Graft Placement and Fixation
The STSG is trimmed to match the defect with 2-3 mm overlap on all sides. Sheet grafts (unmeshed) are placed dermal-side down and secured with staples, absorbable sutures, or adhesive strips at the periphery. For sheet grafts, pie-crusting (making small stab incisions through the graft with a #11 blade) allows drainage of fluid that would otherwise accumulate beneath the graft and cause failure. A bolster dressing using mineral oil-impregnated gauze (Xeroform or Adaptic) with a cotton bolster tied over with sutures provides compression and immobilization.
Immobilization Period
The graft site must be immobilized for 5-7 days to prevent shear forces that disrupt the developing vascular connections. For lower extremity grafts, this means strict elevation and bed rest or limited ambulation with compression. For scalp grafts, a compressive head wrap is maintained. The bolster is removed at 5-7 days; the graft should appear pink and adherent to the wound bed.
Graft Take Physiology
STSG survival follows the same three-phase sequence as FTSG: imbibition, inosculation, and revascularization. The thinner dermal component of STSG confers a survival advantage at each stage because of reduced metabolic demand and shorter diffusion distances.
Phase 1: Imbibition (0-48 hours)
The graft absorbs nutrients and oxygen by passive diffusion from the wound bed exudate (plasmatic imbibition). STSGs survive this phase more reliably than FTSGs because the thinner dermis has shorter diffusion distances and lower metabolic requirements. Fibrin bonds form between the graft undersurface and the recipient bed during this phase.
Phase 2: Inosculation (48-72 hours)
Existing vessels in the graft dermis begin to align with and connect to recipient bed capillaries. This is the most vulnerable period. Any disruption of the graft-bed interface (hematoma, seroma, shear) during inosculation leads to graft failure.
Phase 3: Revascularization (Day 4-7 onward)
New capillary ingrowth from the recipient bed penetrates into the graft dermis. VEGF and other angiogenic factors drive neovascularization. By day 7-10, sufficient vascular connections exist to support graft metabolism independently. The graft transitions from pale to pink as perfusion is established.
Meshing Techniques and Ratios
Meshing involves passing the harvested STSG through a meshing device that creates a pattern of slits, allowing the graft to be expanded to cover a larger surface area. The choice between sheet and meshed grafts depends on cosmetic requirements, wound bed vascularity, and defect size.
| Mesh Ratio | Expansion Factor | Indications | Cosmetic Outcome | Healing Time |
|---|---|---|---|---|
| Sheet (no mesh) | 1:1 | Face, hands, any area requiring best cosmesis | Best — smooth surface | 7-10 days |
| 1:1 (meshed, not expanded) | 1:1 | Drainage on questionable beds, non-cosmetic areas | Good — minimal pattern | 10-14 days |
| 1:1.5 | 1.5x area | Moderate-sized wounds, adequate vascularity | Moderate — visible mesh pattern | 14-21 days |
| 1:3 | 3x area | Very large wounds, burns, limited donor tissue | Poor — permanent mesh pattern | 21-28 days |
Complications
STSG complications fall into early graft-related failures and late cosmetic/functional sequelae. Recognizing and addressing these early improves outcomes.
Early Complications (First 2 Weeks)
Graft failure is the most significant early complication, occurring in 5-10% of cases overall. The leading causes are hematoma (blood accumulation beneath the graft), seroma (serous fluid collection), shear forces (graft movement on the bed), and infection (bacterial colonization exceeding 10^5 organisms/gram). Partial graft loss can be managed conservatively with moist wound care and secondary intention healing of the failed areas.
Late Complications
Secondary contraction is the most predictable late complication of STSG, with thin grafts contracting up to 50% of their original surface area over 6-12 months. Hyperpigmentation (especially in darker skin types), hypopigmentation, and dysesthesia (altered sensation) are common. The graft surface often appears shiny and lacks normal skin texture and adnexal structures. Donor site complications include delayed healing (especially if the graft was cut too thick), hypertrophic scarring, infection, and chronic pain.
Lower Extremity Considerations
The lower extremity presents unique challenges for skin grafting due to dependent positioning, venous insufficiency, reduced vascularity, and gravitational edema. STSGs are generally preferred over FTSGs for lower leg defects because the higher take rate compensates for the suboptimal wound bed conditions common in this region.
Frequently Asked Questions
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References
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- [2]Harries RL, Bosanquet DC, Harding KG Wound bed preparation: TIME for an update. Int Wound J. 2016.
- [3]Goldberg LH, Alam M Skin grafts in cutaneous surgery: a comparison of types. J Am Acad Dermatol. 2020.
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- [5]Liang CA, Kline LB Split-thickness skin grafts for lower extremity defects after Mohs surgery. Dermatol Surg. 2019.
- [6]Ahmed AM, Goldberg LH Meshed versus sheet grafts in dermatologic surgery. J Cutan Med Surg. 2022.