Rotation Flaps

Rotation flaps recruit adjacent tissue by pivoting it along an arc centered on a fixed point. The defect is typically triangular or is converted to a triangle, and the curvilinear incision extends from one edge of the defect outward in a sweeping arc. As the flap rotates into the defect, the effective tissue movement is a combination of rotation and some degree of advancement. The key biomechanical concept is pivotal restraint: the tissue at the pivot point is tethered and limits the degree to which the flap can rotate. Increasing the arc length increases the effective advancement at the distal tip, reducing wound closure tension. However, longer arcs create larger secondary defects and more tissue rearrangement. The surgeon must balance adequate arc length against the cosmetic and functional consequences of a longer incision.

Pivotal restraint is the central concept governing rotation flap mechanics. As a flap rotates about its pivot point, the effective length of the flap shortens because the straight-line distance from the pivot to the distal tip decreases with rotation. This shortening creates tension at the closure point. The degree of pivotal restraint depends on the arc of rotation: a 90-degree rotation produces moderate shortening, while a 180-degree rotation produces maximal shortening. Several strategies can overcome pivotal restraint: (1) increasing the arc length, which increases the effective advancement component of the flap; (2) performing a back-cut at the base of the flap, which releases the tethering effect at the pivot point; (3) wide undermining, which frees tissue attachments and allows greater mobility; and (4) removing a Burow triangle along the arc to reduce redundancy and facilitate rotation.

The standard rotation flap begins with a triangular defect (or a circular defect converted to a triangle). A curvilinear incision extends from one apex of the triangle in a sweeping arc. The flap is undermined widely and rotated about the pivot point until the leading edge of the flap meets the opposite side of the defect. A Burow triangle is typically excised along the arc or at the base to manage tissue redundancy. The standard rotation flap is versatile and can be used on the scalp, cheek, and trunk. On the scalp, the inelastic galea limits tissue movement, so very large arcs (6-8 times defect width) and galeal scoring may be necessary. On the cheek, moderate-sized rotation flaps can recruit the substantial laxity of the preauricular and cervicofacial tissue.

Rotation flaps can be classified by the number of rotating components, the anatomic location, and whether they are combined with advancement or transposition elements. The table below compares the major variants used in Mohs reconstruction.

The O-to-Z flap (also called bilateral rotation or double rotation) addresses a circular defect by creating two opposing rotation flaps that converge from opposite sides. The circular defect is bisected, and curvilinear incisions extend from each end of the bisecting line in opposite directions. The result is a Z-shaped final scar. This design distributes tension equally on both sides, halving the rotational arc required by each flap. The O-to-Z is particularly useful on the scalp vertex, where bilateral recruitment is necessary due to the circumferential inelasticity of scalp tissue, and on the lower lip, where bilateral tissue recruitment preserves oral competence and symmetry. On the scalp, the arc may need to extend to the temporal or occipital regions to achieve adequate mobilization.

The dorsal nasal rotation flap, described by Rieger, is a specialized rotation flap that recruits the entire dorsal nasal skin envelope to fill defects of the distal nasal dorsum and nasal tip. A curvilinear incision begins at one side of the defect, courses along the lateral nasal sidewall, and extends cephalad to the glabella or medial brow. The entire dorsal nasal skin is undermined in the supraperichondrial/supraperiosteal plane and rotated to fill the defect. A standing cone is typically excised in the glabellar region. This flap provides an excellent color and texture match because it uses nasal skin to reconstruct nasal skin. The blood supply is strong, deriving from the dorsal nasal artery and lateral nasal branches. The main limitation is that it can cause slight asymmetry of the nasal dorsum or deviation of the nasal tip, particularly if the flap is under excessive tension.

The following general steps apply to all rotation flaps: (1) Assess the defect and identify the optimal pivot point and direction of rotation. (2) Design the curvilinear incision, ensuring the arc length is 4 to 8 times the defect width. Mark the incision with a surgical marker before cutting. (3) Incise through skin and subcutaneous tissue along the planned arc. (4) Undermine the flap widely in the appropriate surgical plane (subcutaneous on the face, subgaleal on the scalp, supraperichondrial on the nose). (5) Test flap mobility by rotating it into the defect without sutures. If tension is excessive, lengthen the arc, deepen undermining, or perform a limited back-cut. (6) Excise the Burow triangle at the point of maximum tissue redundancy. (7) Close the wound in layers with deep absorbable sutures to obliterate dead space and reduce tension, followed by cutaneous sutures or staples. (8) Ensure hemostasis and consider a bolster or drain if dead space persists.

Complications of rotation flaps include distal flap necrosis (particularly if the arc is too short or the back-cut is too long), hematoma formation (especially on the scalp where subgaleal dead space is large), wound dehiscence (from excessive tension at the pivot point), standing cone deformity (from inadequate Burow triangle excision), and distortion of adjacent landmarks. On the nose, the Rieger flap can cause tip deviation or dorsal asymmetry. On the scalp, alopecia along the scar line is expected and should be discussed with the patient preoperatively. Hematoma prevention on the scalp requires meticulous hemostasis, consideration of a drain, and a pressure dressing. If distal necrosis occurs, conservative wound care with moist dressings typically allows secondary intention healing with acceptable results.