Types of flaps
In facial wound reconstruction, the surgeon works with both a primary defect, created by the wound itself, and a secondary defect, created by the incision outlining the skin selected for the cutaneous flap. Movement of the flap to cover the wound creates the primary skin movement, but the skin adjacent to the wound and to the flap also moves, causing a secondary skin movement. Suturing the secondary defect first reduces the tension on the flap."Closing the secondary defect prior to closing the primary defect decreases the tension on the flap as it is sutured into place," Dr. Lehrer says.
In an advancement flap the tissue slides entirely in one direction, without rotation or transposition. Advancement flaps are useful when the incision lines of the flap run parallel to existing skin lines.
A single pedicle, or unilateral, advancement flap moves skin in a single direction to cover the primary defect, and a bilateral advancement flap moves skin from both sides of the primary defect. The design of bilateral advancement flaps varies according to the type and location of the primary defect. Bilateral advancement flaps include H-plasty, A to T-plasty and O to T-plasty.
A transposition flap "jumps" over an intervening island of normal tissue to cover a wound.
Rhombic transposition flaps are constructed by designing a rhombus around the primary defect. Rhombic flaps may be used to redistribute tension on the wound closure.
"In designing the flap, consider the direction of closure of the secondary defect," Dr. Lehrer says. "The first key suture should close the secondary defect."
Another common transposition flap is the "note flap," so called because the design is reminiscent of a musical eighth note. A note flap is useful on curved surfaces or for circular defects.
Swing-side plasty flaps are smaller than the wound itself, but undermining reduces the area of the wound, allowing adequate coverage by the flap. Ischemia of the flap is minimized, and there is no tip necrosis.
Rotation flaps are designed like a half-circle, with a flap to defect ratio of 3 or 4 to 1. A vector of tension is created at the pivot point of the flap rotation, so that the radius of the arc is the line of greatest tension. Placing the key tension-bearing suture closes the primary defect and defines the secondary defect.
Whether rotation flaps are suitable depends on the size of the primary defect, the extensibility of the donor tissue and the amount of tension that can be tolerated across the secondary defect. Rotation flaps can be used in wound reconstruction in the temple, cheek, scalp, nose and chin.