Answer:
The Z-plasty involves transposition of two triangular-shaped flaps. The purpose is three-fold: (1) lengthening of a linear scar contracture, (2) dispersal of a scar- i.e. breaking up a straight line scar, and (3) realigning the scar within lines of minimal tension. In the classic Z-plasty, the two triangular flaps have limbs of equal length cut at a 60 degree angle. In trying to re-orient the scar to parallel the lines of minimal tension, the limbs should follow the lines of minimal tension. Often, this requires an angle of less than 60 degrees.
The W-plasty involves imbrication of triangles of skin on each side of an excised scar. The triangles are at 60-degree angles, the tip of one opposing the base of the other side. Like the Z-plasty, the W-plasty breaks up a straight linear scar into smaller components, and can improve the direction of the scar.