Reconstruction of Congenital Auricular Malformations
Reconstruction of auricular malformations requires a comprehensive knowledge of microtia for selection of the proper surgical approach. Inadequate knowledge and experience of reconstruction of the ear has led to disastrous results. For this reason, the plastic surgeon should be well aware of the many surgical options that exist to treat microtia. This chapter covers ear deformities ranging from simple protruding ears to major congenital deformities. The single most important ingredient for a successful result is the surgical experience of the surgeon. Adequate study and meticulous attention to detail will lead to the best possible outcome. In addition, the plastic surgeon should realize that the care of the patient with an ear deformity might necessitate a team approach that includes an otologist, psychiatrist, audiologist, and radiologist. The family of the patient afflicted with an auricular malformation deserves a coordinated approach and should be aware of the complete plan at the outset of treatment.
Topographic landmarks of a normal ear are shown in Figure 23-1. Development of the auricle is first observed in the 5-week-old embryo. The auricle begins as six mesenchymal proliferations at the dorsal ends of the first and second pharyngeal arches surrounding the first pharyngeal cleft. Initially, the external ear is located in the lower neck of the embryo. As the mandible develops, the ear ascends to the side of the head at the level of the eyes. The commonly accepted embryologic theory (Fig. 23-2) is that the six hillocks correlate directly with the tragus, helix, cymba, scapha, antihelix, and antitragus.1
The auricle receives its blood supply from the superficial temporal, posterior auricular, and occipital arteries. The venous drainage of the auricle is by the posterior auricular, external jugular, superficial temporal, and retromandibular veins. The lymphatics of the ear drain anteriorly to the parotid lymph nodes and posteriorly to the cervical lymph nodes. The auricular muscles are innervated by branches of the seventh cranial nerve. The temporal branch of the facial nerve supplies the anterior and superior auricular muscles, and a posterior auricular branch of the same nerve supplies the posterior auricular muscle. Sensory innervation of the auricle is from the lesser occipital, great auricular (C2, C3), and auricular temporal nerves. Arnold’s nerve, a branch of the tenth cranial nerve, supplies the concha.
A normal auricle is shown in Figure 23-3. The vertical axis of the normal auricle is tilted posteriorly approximately 20°. The vertical height of the normal ear is approximately equal to the distance between the lateral bony orbital rim and the root of the helix at the level of the eyebrow (about 6-cm). The width of the ear is approximately 55% of its height. Typically, the helical rim protrudes 1- to 2-cm from the skull, and the angle of protrusion should be between 25° and 30°. The superior aspect of the ear is usually level with the eyebrow.2
A number of congenital auricular deformities exist that may require surgical intervention. To achieve the most natural appearing ear possible through surgery, the surgeon must assess the deformed ear for the presence of several important auricular landmarks. Recognizing and grading the deformity will allow the surgeon to craft the proper surgical options. Involving family members of the patient with an ear deformity is important. Eavey3 observed that children with microtia and significant auricular malformations require comprehensive attention directed to early family counseling and evaluation of the patient for expected and unexpected hearing loss, impaired language development, and associated medical conditions. Both auricular and otologic reconstructive procedures may be necessary and must be coordinated. In 1999, Wang4 identified that the early use of an auricular prosthesis is psychologically beneficial to children who have an ear defect resulting from congenital malformation. Wang also described techniques to establish the proper location and orientation of auricular implants used to secure auricular prostheses by using information from computed tomography (CT) scans. The techniques were applied to children and adults to ensure accurate implant placement, leading to improved positioning and orientation of auricular prostheses.
External ear deformities exist in 1% of births. Correcting major congenital malformations of the auricle tests the plastic surgeon’s surgical skills. Microtia has been the subject of numerous publications as clinicians have attempted to establish a method of classification of the severity of a given deformity. Tanzer5,6 in 1959 published the first scientific article on auricular reconstruction with autogenous rib cartilage. In 1966, Cronin7 popularized the use of silicone as an implant material to reconstruct auricles. Brent,8 who first reported his work in 1974, is considered the world’s foremost authority on auricular reconstruction.
In 1988, Aguilar and Jahrsdoerfer9 amended the 1926 grading system used to classify the severity of microtia described by Marx. In 1996, Aguilar10 reaffirmed this concise classification of congenital ear malformations: grade I is a normal ear; grade II has some of the auricular framework present, but there are obvious deformities; and grade III is the standard “peanut ear” deformity (Fig. 23-4), which encompasses anotia (Marx’s grade IV).
In 1974, Rogers12 published a similar classification that divided deformities into four groups: macrotia, lop ear, cup ear, and prominent ear. Weerda13 combined all of the classifications proposed by Marx and Tanzer and modified by Rogers.14 This classification is included for completeness, and demonstrates the awkwardness of classification schemes that are too comprehensive or detailed. Weerda’s system included surgical guidance for each classification:
First-degree dysplasia. Average definition: most structures of a normal auricle are recognizable (minor deformities). Surgical definition: reconstruction normally does not require the use of additional skin or cartilage.