Skin Grafts

Full-thickness skin grafts (FTSG) include the complete epidermis and full-thickness dermis, with all adnexal structures. Split-thickness skin grafts (STSG) include the epidermis and a variable portion of the dermis. The thickness of the graft determines its properties: thicker grafts contract less, match surrounding skin better, but have higher metabolic demands and lower take rates.

Graft survival proceeds through three overlapping phases that require a well-vascularized wound bed and strict immobilization:

FTSGs are indicated when: • Primary closure is not possible (insufficient tissue laxity) • Local flaps would distort free margins (eyelid, alar rim, lip) • The defect is on a concave surface (medial canthus, conchal bowl, temple hollow) where flaps may tent or create unnatural contours • The patient prefers a simpler, single-stage procedure over a flap • The defect size is too large for local flap coverage FTSGs are particularly well-suited for the medial canthus, nasal sidewall, conchal bowl, and eyelid. Concave surfaces where grafts settle into the contour naturally.

Choosing the right donor site is the most important decision in FTSG planning. The ideal donor provides skin that matches the recipient site in color, texture, thickness, and sebaceous quality.

Graft harvesting technique: 1. Create a template: use the foil from a suture package or a piece of sterile paper, press it into the defect, trim to exact size, and add 2–3mm on each side to compensate for graft contraction. 2. Transfer template to donor site: trace and mark the graft outline as an ellipse oriented along RSTLs of the donor site. 3. Harvest: incise the marked ellipse with a #15 blade and sharply dissect the graft from the underlying subcutaneous tissue. Close the donor site primarily in layers. 4. Degrease: this is the most critical processing step. Place the graft dermal-side up and meticulously remove all subcutaneous fat using sharp iris scissors. The goal is a smooth, glistening dermal surface with no visible fat lobules. Residual fat acts as a barrier to revascularization and is the most common cause of preventable graft failure. 5. Fenestrate: make small stab incisions (2–3mm) throughout the graft to allow drainage of blood and seroma fluid that would otherwise accumulate beneath the graft and prevent contact with the wound bed.

The graft must be immobilized against the wound bed to prevent shearing during the critical inosculation phase (days 2–4). 1. Suture the graft: place interrupted sutures (5-0 or 6-0 absorbable or nylon) around the perimeter, spacing evenly. Leave suture tails long (3–4cm) for bolster tie-over. 2. Build the bolster: shape a piece of cotton, Adaptic, or mineral oil-soaked gauze to match the graft dimensions. The bolster should provide firm, even pressure across the entire graft surface. 3. Tie over: use the long suture tails to tie the bolster firmly over the graft. The bolster should compress the graft uniformly against the wound bed. 4. Leave in place: the bolster remains for 5–7 days. Instruct the patient to avoid any manipulation of the site. 5. Bolster removal: at 5–7 days, carefully cut the tie-over sutures and remove the bolster. The graft should appear pink (viable) with early adherence to the wound bed.

Composite grafts contain skin and underlying cartilage (chondrocutaneous graft) or skin and fat. The most common application is reconstruction of alar rim defects after Mohs surgery. Auricular composite graft: harvested from the antihelix, conchal bowl, or root of the helix. The graft includes skin on both surfaces with cartilage in between. It provides structural support and skin coverage simultaneously. Size limitation: composite grafts should not exceed 1–1.5cm in greatest dimension. Larger grafts have unacceptably high failure rates because the cartilage component increases the metabolic demand while having no intrinsic blood supply. The characteristic color changes in the first 48 hours are expected: the graft appears white initially (ischemia), then transitions to blue/purple (venous congestion), then gradually pinks up as revascularization occurs. This white-blue-pink sequence is normal and should not prompt intervention.

Understanding the causes of graft failure allows the surgeon to optimize technique and prevent complications.