Mathematical guide to minimize donor size in full-thickness skin grafting

Full-thickness skin grafting is a common repair option in dermatologic surgery. Generally, a 3:1 ellipse is designed for the donor area. This results in occasional large donor site defects. A new formula to guide donor site design would potentially create smaller donor defects.

To design a mathematical formula to facilitate smaller donor incisions.

A geometric analysis was undertaken to design a practical formula to create smaller defects. This strategy was then used in a case series of 23 patients with large (average 11 cm in diameter) defects [This sentence was corrected after online publication on June 29, 2009: (average 16 x 11 cm) changed to read (average 11 cm in diameter).]. A geometrical analysis was used to design the best way to divide donor grafts to minimize tissue loss.

A formula called for the diameter of the primary defect to be multiplied by 3/2 and 2/3 to design a donor ellipse length and width, respectively. The resulting graft was divided into two equal sizes, using a tangential acute angle. The width and the area of the donor were significantly smaller, so the donor site was repaired using a shorter and faster repair.

Skin graft harvest may be accomplished using a smaller donor graft than previously described using the formula reported here. This will probably reduce surgical morbidity, time, and expense. The authors have indicated no significant interest with commercial supporters.