Fundamentals of expanded tissue.

The relatively recent advent of tissue expansion for medical purposes precludes the availability of extensive knowledge concerning the physiologic and histologic changes that occur during controlled expansion of the skin. This paper reviews the basic science and clinical research that has been conducted to investigate the changes and summarizes the findings. It can be concluded that flaps harvested from skin previously expanded have an improved survival rate compared to similar flaps developed in nonexpanded skin. Increased vascularity to either the skin, the capsule that forms around the expander, or both probably in some way accounts for the improved survival. Controlled expansion of the skin results in the creation of additional new skin at the expense of thinning the dermis and subcutis. This thinning is associated with an overall decrease in tensile strength of the expanded skin. The increase in surface area gained from skin expansion probably varies according to the type of skin expanded and the underlying tissues that serve as a foundation for the expander.