Skin Flap Surgery

Tissue Mechanics and Vascular Classification

Classification by Blood Supply

• Random pattern flap: The flap relies on the subdermal and intradermal vascular plexus. Because it has no named axial artery, its length-to-base-width ratio should not exceed 3:1 (up to 4:1 on the face, thanks to its rich blood supply) to avoid ischemia at the tip.
• Axial pattern flap: The pedicle contains a named artery and vein (for example, the supraorbital/supratrochlear artery supplying the paramedian forehead flap). The flap can be made much longer while still surviving completely.

Tissue Biomechanics

• Primary defect: The wound created by removing the lesion.
• Secondary defect: The new gap created where the flap was taken from.
• Redirecting tension: At its core, a flap moves the tension vector away from sensitive skin (near the eye or the nasal ala) to neighboring skin that is mobile and has tissue to spare, so that key anatomical structures are not pulled out of shape.

Common Local Flaps in Facial Reconstruction

Advancement Flaps

The flap moves in a straight line directly into the defect, without rotating or crossing over intact skin.

• Single or bipedicle advancement flap: Two parallel incisions are extended from the defect, the tissue is undermined and slid forward. Burow's triangles are usually removed at either side of the flap base to prevent "dog-ear" bulges.
• V-Y advancement (island pedicle) flap: A triangular flap is pushed into the defect and the trailing edge is closed in a Y shape. Very effective for defects of the upper lip (philtrum area), cheek and nasal ala.
• O-to-T flap / H-plasty: Two mirror-image advancement flaps close a round defect from opposite sides, leaving a T- or H-shaped scar (often used on the forehead and just above the eyebrow).

Rotation Flaps

A curved (arcuate) incision allows the flap to swing around a pivot point and cover a triangular defect.

• Principle: The arc of the flap should be 4–5 times the width of the base of the defect.
• Uses: Large defects on the scalp, cheek and chin, where the curved incision can be hidden in natural creases or along the hairline.

Transposition Flaps

The flap is lifted and moved across an area of neighboring intact skin to fill the primary defect.

• Rhomboid flap (Limberg / Dufourmentel flap):
  • Technique: The round defect is converted into a rhombus with 60° and 120° angles. A rhombus-shaped flap is drawn alongside and swung into place.
  • Uses: Reconstruction of defects on the temple, cheek and back.
• Bilobed flap:
  • Technique: The flap has two adjoining lobes. The first lobe (90–100% of the size of the primary defect) rotates into the primary defect. The second lobe (50–80% of the size of the first) fills the gap left by the first lobe. The defect left by the second lobe is closed directly.
  • Gold-standard indication: Defects of 0.5–1.5 cm on the lower third of the nose (tip and ala), where the skin is thick and not very mobile.
• Z-plasty: Two mirror-image triangular flaps are swapped to lengthen a scar in a chosen direction and rotate the tension axis by 45–60°, releasing tight, contracted scars.

Interpolation Flaps

The flap's pedicle passes over or under a bridge of intact skin. This requires a two-stage operation (stage 1: flap transfer; stage 2: division of the pedicle after 3–4 weeks).

• Paramedian forehead flap: An axial flap (supraorbital/supratrochlear artery). The gold standard for large defects involving the entire nasal tip or a nasal ala down to cartilage.
• Nasolabial interpolation flap: Uses tissue from the smile line to rebuild defects of the nasal ala or the helix of the ear.

Avoiding and Managing Complications

Depth of Undermining

The depth of dissection is critical to flap survival:

• Face: In the superficial subcutaneous fat or just above the SMAS, to protect the branches of the facial nerve (CN VII).
• Nose: Just above the periosteum or perichondrium (subperichondrial/subperiosteal plane), so the full, robust vascular layer is included.
• Scalp: In the loose subgaleal plane.

Managing Flap Ischemia and Necrosis

• Venous congestion: The flap is bluish-purple, swollen and oozes dark blood. Management: Remove sutures causing excess tension at the base, release blood by small incisions, or apply warm compresses.
• Arterial insufficiency: The flap tip is pale, white, dull and cold. Management: Check whether the pedicle is kinked, loosen sutures, apply local nitroglycerin or use intravenous therapy.

Trapdoor Effect (Pincushioning)

• Appearance: After healing, a rotated or transposed flap bulges up in a dome above the surrounding skin because the circular scar beneath it contracts.
• Prevention and treatment: Undermine the wound bed widely, 1–2 cm beyond the flap edge; inject intralesional triamcinolone acetonide (5–10 mg/mL) or resurface with fractional CO2 laser from the second month onward.

Our Flap Surgery Process at Haute-Derma

• Assessment and Surgical Marking
  • The edges of the defect are marked once the margins have been confirmed clear.
  • The planned flap is drawn along the relaxed skin tension lines (RSTL), with the rotation angle and Burow's triangles worked out in advance.
• Tumescent Anesthesia and Vessel-Sparing Dissection
  • Lidocaine 1% with epinephrine 1:100,000 is infiltrated gently.
  • Clean incisions are made at 90° to the skin surface, and dissection follows the correct, safe anatomical plane.
• Trial Fit and Bipolar Hemostasis
  • The flap is test-fitted into the defect to make sure it sits perfectly with no tension at all (tension-free).
  • Bleeding is controlled meticulously with fine bipolar cautery, avoiding excessive burning that could damage the pedicle.
• Layered Closure to Minimize Tension
  • Deep dermal sutures are placed with 5-0 PDS or Vicryl.
  • The skin edges are closed with 6-0 or 7-0 nylon or Prolene under surgical loupes.
• Aftercare and Monitoring of Blood Flow
  • Antibiotic ointment is applied with a light pressure dressing to prevent hematoma. The flap's color is checked at 24–48 hours.