Typical "Z" plastic surgery: take the scar contracture line as the central axis, and make parallel auxiliary incision lines with equal angles and opposite directions at both ends of the central axis. In this way, two triangular skin flaps are combined into a parallelogram, the short diagonal on the contracture line is called the contracture diagonal, and the long diagonal perpendicular to it is called the transverse diagonal. After operation, the central axis can be increased to be equal to the length of the transverse diagonal line before operation. According to the principle of geometry, the greater the angle between the two arms and the central axis, the greater the elongation of the central axis after operation. But the angle is too big, so it has no practical application value in clinic. 30 years old is too young? The extension of the inner axis and the central axis is very few. Usually at 45? ~60? Most applicable. When the flaps are cross-stitched, the tips of the flaps can be obtuse to ensure blood supply. Three-point method is adopted for the tip suture, and it is not allowed to penetrate the full thickness of the tip.