Undermining of the scalp: quantitative effects.

The aim of the present study was to evaluate to what extent undermining-affects the closing-tension of scalp defects to quantify the surgery-related benefits provided by this procedure. Data were collected by stepwise loading in 10 patients, 20 scalp flaps (obtained by a reversed Y scalp incision), and thee different degrees undermining (1, 5, and 15 cm). The obtained data confirmed the value of undermining to diminish the tension on wound margins when closing a scalp defect. There nas a progressive decrease in tension required to advance the wound edge when the amount of undermining was sequentially increased. Most of this reduction occurred with the 5-cm undermining, although statistically the 15-cm undermining also resulted in a significant decrease in the tension required to close the defect. Mean 83.3- and 92.2 percent reductions of the closing tension were obtained with 5 cm and 15 cm of undermining, respectively, compared with that achieved by the 1-cm undermining with the same width of defect.