A 70-year-old woman underwent Mohs micrographic surgery for a large basal cell carcinoma on the nasal tip. The defect was repaired using the flap shown below.

Which of the following describes the type of flap used in this reconstruction?

A. Advancement flap

B. Rotation flap

C. Interpolation flap

D. Island pedicle flap

E. Transposition flap

Rationale: 

The image shows a paramedian forehead flap, a classic example of an interpolation flap. Interpolation flaps are defined by the fact that they are not immediately adjacent to the defect, cross over intervening, intact skin (e.g., the glabella), and require staging, typically including a second procedure to divide the pedicle after 2–3 weeks. The flap is based on the supratrochlear artery and is used to repair complex nasal defects involving the tip, ala, or columella. The paramedian forehead flap is a great option for large defects involving the tip/ala due to the excellent color, thickness, and texture match and its robust axial blood supply.

Correct answer: C. Interpolation flap. The paramedian forehead flap is a prototypical interpolation flap, used in multi-stage nasal reconstruction.

Incorrect answers: 

A. Advancement flaps are used in areas with significant skin laxity (e.g., cheek, forehead), but do not cross intervening skin or require staged division.

B. Rotation flaps involve curving adjacent tissue around a pivot point into the defect.

D. Island pedicle flaps involve a subcutaneous pedicle flap from adjacent skin, moved without crossing intervening skin.

E. Transposition flaps, such as bilobed or rhomboid flaps, do not cross intervening skin and are typically single-stage repairs. 

Additional reading at Facial Flap Surgery Chapter 6: Staged Pedicle Flaps.