Composite Grafts, Split-Thickness Grafts, and Free Cartilage Grafts

A composite graft is a free graft consisting of two or more tissue types, most commonly skin and cartilage, harvested as a single unit. The most clinically important composite graft in dermatologic surgery combines auricular skin with the underlying conchal or helical cartilage for reconstruction of nasal alar defects involving cartilage loss. Because the graft contains avascular cartilage in its center, composite grafts have the most precarious blood supply of any graft type. They rely entirely on peripheral revascularization from the wound margins. This limits reliable composite graft size to approximately 1.0-1.5 cm in greatest dimension. Larger composite grafts carry a high risk of central necrosis due to insufficient perfusion of the graft core.

The ear is the primary donor site for composite grafts used in facial reconstruction. The conchal bowl provides a concave cartilage-skin unit ideal for nasal alar replacement, while the helical root/crus provides a convex unit suitable for alar rim or helical rim reconstruction.

Composite grafts undergo a characteristic color change sequence during the first week that serves as a clinical indicator of graft viability. Recognizing this sequence is essential for appropriate postoperative management and patient reassurance.

A split-thickness skin graft consists of the entire epidermis and a variable portion of the dermis. STSGs are classified by dermal thickness: thin (0.13-0.30 mm, also called Thiersch grafts), medium/intermediate (0.30-0.46 mm), and thick (0.46-0.76 mm). STSGs are harvested using a dermatome (manual or powered) that shaves the skin at a controlled depth. Because they leave behind a dermal remnant at the donor site, the donor wound heals by re-epithelialization from the remaining adnexal structures (hair follicles, eccrine ducts). This is a critical distinction from FTSGs where the donor site requires primary closure.

Understanding the key differences between graft types is fundamental to selecting the appropriate reconstruction method for each clinical scenario.

Free cartilage grafts provide structural support and architectural framework without a skin component. Cartilage is avascular and derives its nutrition from surrounding perichondrium and overlying soft tissue via diffusion. This property allows cartilage to survive as a free graft in most wound beds. Free cartilage grafts are used to restore contour and prevent collapse in areas where the cartilage framework has been lost during tumor extirpation.

Composite graft success depends on maximizing the graft-recipient contact area and minimizing metabolic demand during the critical revascularization period. The graft should be slightly oversized (10-15%) to account for contraction. Gentle handling is essential. Cartilage should not be crushed with forceps. The graft is sutured with interrupted sutures placing the skin-to-skin and cartilage-to-cartilage interfaces in alignment. Some surgeons advocate fenestrating the skin component to allow drainage and prevent hematoma. The wound bed must be freshened and hemostatic. Postoperatively, cooling with cold compresses for 48-72 hours reduces metabolic demand and has been shown to improve composite graft survival rates. Patients must be strictly counseled to stop smoking for at least 2 weeks before and after surgery.

Composite graft complications include partial necrosis (most common, especially central necrosis due to inadequate perfusion), complete graft loss, infection, hematoma formation beneath the graft, color mismatch, contour irregularity, and donor site complications (ear deformity if excessive cartilage is harvested). STSG complications include secondary contraction (the most functionally significant), poor cosmetic appearance (shiny, depigmented, atrophic), donor site pain and infection, hypertrophic scarring at the donor site, and pigmentary changes. For cartilage grafts, complications include warping (especially rib cartilage), resorption over time, infection, and visible/palpable edges.