Chapter 19: Axial Pattern and Interpolation Flaps

INTRODUCTION

Facial symmetry correlates highly with facial attractiveness.¹ The symmetry of midline structures has the greatest impact on perception of beauty.² As the nose occupies the most central location on the face, its complex, symmetrical contours play a key role in how we perceive other people’s faces. Observers normally focus their gaze on the central triangle of the eyes, nose, and mouth.³ Asymmetric noses are perceived as less attractive, deformed noses attract excessive attention,^1,3 and even small nasal lesions are considered disfiguring, bothersome, and important to repair.⁴ When local flaps are insufficient for coverage of a complex nasal defect, the surgeon may need to consider staged repair with a forehead or cheek interpolation flap. Similarly, the ear may require a postauricular interpolation flap (PIF) to repair a larger defect in an aesthetic fashion. Staged interpolation flaps present unique technical challenges. This chapter will discuss the planning and execution of: (1) the paramedian forehead flap for nasal reconstruction; (2) the melolabial interpolation flap (MIF) for alar reconstruction; and (3) the retroauricular interpolation flap for ear reconstruction.

ANATOMY OF THE EXTERNAL NOSE

The nose has subtle convexities and concavities resulting from the complex anatomy of the bone, cartilage, and soft tissue. The surgeon’s task is to recreate or simulate the normal anatomy, restore the complex nasal topography and maintain airway patency. This section will focus on those aspects of external nasal anatomy essential to planning and executing the paramedian forehead flap and the MIF.

Bony Framework of the Nose

The pyriform aperture demarcates the boundary between the external and internal nasal cavities. It provides a stable frame for the cartilaginous framework of the nose and anchors most of the muscles of facial expression. The paired nasal bones form the superior border of the pyriform aperture, merging in the midline and projecting outward as the nasal dorsum. The maxilla forms the lateral and inferior borders of the pyriform aperture. The anterior nasal spine at the maxillary midline forms the most prominent inferior bony projection of the nose.

Cartilaginous Framework of the Nose

Cartilage forms the nasal skeleton external to the pyriform aperture. The nasal cartilages determine nasal projection and support the airways. In contrast to the immobile bony skeleton, the flexible cartilaginous framework is vulnerable to distortion and compression, which can alter appearance and impair breathing. The external nasal framework consists of three primary structures: (1) the septal cartilage; (2) the paired upper lateral cartilages; and (3) the paired lower lateral cartilages. The septal and paired upper lateral cartilages are anchored to bone and therefore provide more resistance to compression.

The quadrilaterally shaped septal cartilage is rigid and flat, gaining stability through its articulations with the ethmoid bone, vomer, maxilla, and nasal bone. Its caudal margin slopes from the anterior nasal spine to ...