Planimetric elongation of skin by Z-plasty.

The present paper investigates the elongation of skin that can be achieved by Z-plasties. The following observations have been made: 1. Traditional Z-plasties always result in a stereometric transfer of skin with two kinds of elongation, the stereometric and the planimetric. 2. The stereometric elongation accomplished within the Z-plasty was immediately below the mathematical values if measured stereometrically under in vitro conditions. Stereometric elongation can effectively be used only in connection with stereometric structures. 3. The planimetric elongation of the skin was accomplished outside the Z-plasty and extended far into the surrounding tissue. Planimetric elongations are needed for scar corrections on plane surfaces. 4. Only Z-plasties with tip angles of alpha/beta = 75 and 60 degrees were suited to make optimum use of the planimetric elongation in the primary direction of a scar. All other Z-plasties under study provided smaller planimetric elongation values. Z-plasties with tip angles alpha/beta = 30 degrees even produced shortenings. The mechanical and geometric reasons for these findings have been discussed.