Clinical and experimental evaluation of intermittent intraoperative short-term expansion.

To assist in the closure of defects in the region of the head lack and neck, a number of surgeons recommend intermittent intraoperative short-term expansion to exploit the biomechanical properties of the skin. It was the aim of this study to assess quantitatively the amount of intraoperative "tissue gain," to analyze its origin, and to throw light on its underlying biomechanical processes. A total of 285 expansions in 5-minute intervals under a constant tissue pressure of 100 mmHg were performed on 30 patients with severe microtia. The volumes achieved were protocolled, and microcirculation was monitored with the help of a laser-Doppler flowmeter. Expanders exerting a tissue pressure of 100 mmHg for more than 80 cycles lasting 20 minutes also were employed in five dogs. Apart from determining the volumes, changes in distance between the skin tattoos and the diameter of the expander base were recorded. A volume increase of about 10 percent per hour was recorded for the human patients and an increase of about 30 percent per hour for the animals. After reaching a maximal increase in length of 15 to 20 percent, there was no further skin elongation despite increasing volumes. Instead, the expander began to move into the subcutaneous tissue so that its diameter showed a continuous increase. We can conclude on the basis of these results that the increase in volume during intermittent intraoperative short-term expansion is not caused by the proclaimed "creep" behavior of the skin.