Congenital malformations of the external ear are uncommon birth defects with long-term sequelae for children and their families. The impact of such deformities on the patient can be both physical and emotional. Parents often experience feelings of guilt because they believe they have caused the deformity. School-aged children may be the object of teasing and ridicule. Hearing loss due to associated ear canal atresia can result in learning difficulties.
Auricular malformations range from anotia to mild alterations in the external form of the ear. Fortunately, knowledge of reconstructive techniques and audiological rehabilitation continues to improve and benefit patients.
History of the Procedure
The earliest reports of auricular reconstruction date back to 600 BC from passages in the Sushruta Samhita, in which the great Indian surgeon Sushruta describes ear lobe reconstruction using local skin flaps. In the 16th century, Gaspare Tagliocozzi reported using a transfer flap from the arm to reconstruct the ear. In 1845, Dieffenbach made the next major report when he described the reconstruction of the upper part of an auricle that had been severed sharply by a sabre. Surgeons of the 19th century believed total auricular reconstruction was impossible because no source of skin or elastic cartilage was acceptable to create the auricle.
The modern age of auricular reconstruction begins in the 20th century. In 1920, Gillies first described the use of costal cartilage grafts in reconstructing the auricle. In 1930, Pierce described the principle of creating an auricular framework from cartilage grafts. Tanzer further popularized the use of autogenous rib cartilage for reconstruction. Many of the techniques he described are the foundation of microtia repair today. Brent has further refined these techniques over the last 3 decades.  More recent innovations have also included the use of alloplastic frameworks, incorporation of temporoparietal fascial flaps, and osteointegrated implants for the anchoring of prosthetic auricles.
Today, the basic steps in microtia repair require an average of 2-4 stages and involve the use of either an alloplast or the patient's rib cartilage to serve as a framework that is implanted under the skin. Subsequent stages may involve creating a lobule, separating the reconstructed auricle from the head, and constructing a tragus.
Surgeons involved in microtia repair have long recognized the difficulty of creating a natural appearing ear. These problems are 2-fold and include the creation of a rigid, biocompatible framework and its coverage with skin. No natural substitute exists for the thin pliable auricular cartilage. Nor is skin available of similar quality and elasticity to that covering the auricle. One key to successful reconstruction is to provide sufficient relief in the helix, scaphoid fossa, and antihelix to create the illusion of thin skin overlying thin cartilage. Problems such as thick skin, hair-bearing skin, and poor quality cartilage serve to frustrate the surgeon's attempt to achieve the desired result.
Other challenges in the creation of the auricle are properly positioning the reconstructed ear in relation to the opposite ear, providing sufficient projection of the auricle from the head, creating a postauricular sulcus, and reconstructing a natural appearing lobule and tragus.
Congenital microtia occurs with a frequency of 1 per 7000 live births. The incidence of microtia varies by race, with the highest incidence in persons of Asian and Latin American descent, as well as certain Native American groups. Persons of European origin have a lower incidence, while people of African descent have the lowest incidence. Males are 3 times more commonly affected than females, and the right ear is more commonly involved by a 2:1 ratio. Bilateral defects occur in only 12% of nonsyndromic cases, as compared with 50% of syndromic cases.
In two thirds of cases, the microtia occurs as an isolated defect. Nearly 28% of microtic ears occur in association with other birth defects. Ten percent of microtia occurs as part of a well-defined syndrome. A large proportion of microtia is believed to be due to autosomal inheritance with variable expression and incomplete penetrance. Coexisting conditions that may be present include Goldenhar syndrome, branchiootorenal syndrome, branchial cleft cysts, holoprosencephaly, Treacher Collins syndrome, and Robinow syndrome. Other malformations may include mandibular deformities, facial paralysis, and maldevelopment of the facial and cranial bones.
Rarely can an environmental or genetic cause for microtia be found. Isotretinoin and thalidomide are teratogens that can cause microtia. Microtia also can occur as a result of fetal alcohol syndrome or maternal diabetes embryopathy. Single gene disorders such as Treacher Collins syndrome or chromosomal abnormalities such as trisomy 18 also can result in microtia or anotia.
The development of the auricle involves many embryonic stages. Any small change in any of these stages may result in various forms of deformity. Some of these deformities are known variously as lop ear, cup ear (constricted ear), or cryptotia. These entities differ from microtia and are not discussed. A relationship between the severity of malformations and the amount of the auricular deformity has been noted. In general, the more auricular tissue present, the less severe the associated malformations. The precise pathophysiologic mechanisms by which teratogenic or genetic influences result in microtia have yet to be defined.
Microtia is a congenital disorder and is immediately recognizable at birth. The malformed ear may be completely absent (grade 4 microtia or anotia, but, most commonly, a residual malpositioned lobule is present beneath a rudimentary hillock of cartilage (grade 3 microtia. Microtia is usually associated with aural atresia in the higher stages. Grade 1 microtia (a small ear with normal architecture often has an associated patent ear canal. Grade 2 microtia (a small ear missing much of the architectural features of a pinna may or may not have a patent canal or tympanic membrane. Grade 1 to Grade 4 microtia are depicted in the images below.
Ear reconstruction is indicated when a child with microtia has reached sufficient age, which may be between 3 and 6 years old. The latter age is typically recommended for rib cartilage reconstruction because sufficient time must be allowed for the normal ear to reach most of its adult size and act as an accurate template for the ear to be reconstructed. In addition, the costal cartilage will achieve sufficient size to provide adequate donor material for the framework.
A survey conducted by Im et al of members of the American Society of Plastic Surgeons found that in terms of pediatric patients, 49% of respondents who performed microtia reconstruction preferred to operate on patients aged 7-10 years, while 40% preferred operating on children aged 4-6 years. 
Placing the reconstructed ear in the proper location is important. This placement is best determined by taking measurements from facial landmarks (ie, lateral canthus, alar facial crease, lateral commissure) to the normal ear and transposing the same measurements to the side of the deformity. Making a template of the normal ear from overexposed radiographs ensures that the reconstructed ear has the appropriate size and shape.
In many children, the hairline on the abnormal side is unusually low, causing the cartilage framework implant to be placed at least partially under hair-bearing scalp. Recognizing this problem at the outset is better than attempting to shift the framework inferiorly and anteriorly. The problem of hair over the ear can be addressed later using electrolysis, skin grafting, or laser hair removal.
In patients with hemifacial microsomia, measurements from the normal side of the face would cause the surgeon to place the auricular framework far posterior to the auricular remnant. This eventuality would prevent the surgeon from using the malformed hillocks in lobule reconstruction. In these cases, addressing the hemifacial microsomia first is best, so that mandibular symmetry may be achieved. With this accomplished, proper positioning of the auricle is more likely to result.
Typically, the otologist performs hearing restoration surgery after the first stages of microtia repair are complete. The temporomandibular joint, the path of the facial nerve, and the location of the temporal fossa dura are landmarks that dictate the position of the new ear canal.
Occasionally, in persons with microtia and aural atresia, the pinna is not centered over the ideal location for canal placement. In these individuals, the auricular framework can be shifted a few millimeters in the appropriate direction or the conchal bowl may be enlarged. By the time auricular reconstruction is initiated, ossification of the mastoid bone is complete and the facial nerve, deep to the planes critical to microtia repair, should be protected. Nevertheless, overzealous use of the electrocautery may transmit damaging current to the nerve, particularly in smaller children. In patients with multiple facial anomalies in whom the course of the facial nerve is in question, nerve monitoring should be considered.
Skin quality is another anatomic factor critical to a good outcome. Dissection of the pocket for the auricular framework must be carried out in the subcutaneous plane, deep to the subdermal vascular plexus, but superficial to the galea and other elements of the superficial musculoaponeurotic system complex (SMAS) plane. This allows the skin to be stretched and conformed to the underlying framework. Any prior damage to the skin in this area makes the task of reconstruction significantly more difficult. Radiation therapy, actinic damage, cigarette smoking, and trauma have the potential to rob the skin of critical blood supply, deprive it of healing characteristics, and prevent it from adequately revealing the intricacies of the cartilage framework.
If rib cartilage is to be used, the donor cartilage must be of the appropriate size before reconstruction can be contemplated (see Preoperative details). Adequate cartilage size is generally achieved by the time the child is aged 6 years. This is when the surgeon may harvest the cartilaginous portions of the contralateral sixth, seventh, and eighth ribs to form the framework. To ensure that the cartilage remains viable and has the potential for future growth, perichondrium must be preserved over the harvested portions. In taking pains to preserve the deep perichondrium, the surgeon often violates the parietal pleura. This problem is addressed during surgery by evacuating any air from the pleural cavity with a Valsalva breath, sealing the opening with a running watertight closure, and placing a temporary suction drain in the chest.
Auricular reconstruction using costal cartilage probably is not indicated for patients with limiting anomalies in other parts of the body. Other contraindications include lack of graft material in patients with previous cartilage harvest, patients with poor skin quality in the auricular area secondary to burns or previous surgery, and patients who are poor anesthetic risks.
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