The Dynamic Changes in Skin Thickness of Forehead during Tissue Expansion

In addition to providing extra flap size, the tissue expansion process also brings changes in flap thickness. This study aims to identify the changes in the forehead flap thickness during the tissue expansion period. Patients undergoing forehead expander embedment from September 2021 to September 2022 were included. The thickness of the forehead skin and subcutaneous tissue were measured with ultrasound before and 1, 2, 3, and 4 months after expansion. Twelve patients were included. The average expansion period was 4.6 months, and the mean expansion volume was 657.1mL. The thickness of skin and subcutaneous tissue in the central forehead changed from 1.09 +/- 0.06 to 0.63 +/- 0.05mm and from 2.53 +/- 0.25 to 0.71 +/- 0.09mm, respectively. In the left frontotemporal region, skin and subcutaneous tissue thickness changed from 1.03 +/- 0.05 to 0.52 +/- 0.05mm and 2.02 +/- 0.21 to 0.62 +/- 0.08 mm. On the right side, skin and subcutaneous tissue thickness changed from 1.01 +/- 0.05 to 0.50 +/- 0.04mm and 2.06 +/- 0.21 to 0.50 +/- 0.05 mm. This study measured the dynamic changes in the thickness of the forehead flap during expansion. The thickness of the forehead flap decreased the fastest in the first 2 months of expansion, and the changes in skin and subcutaneous thickness slowed down in the third and fourth months and tended to a minimum value. Additionally, the thickness of subcutaneous tissue decreased greater in magnitude than the dermal tissue.