Aural Atresia of the External Ear 

Updated: Nov 04, 2018
Author: Stephen S Park, MD; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Background

Microtia repair provides many challenges to the facial plastic surgeon.[1] It requires the maintenance of the 3-dimensional details of an ear under the coverage of a 2-dimensional skin surface. In addition, an aesthetically pleasing result requires symmetric position, adequate projection, and dependable longevity. All of these factors contribute to microtia repair being one of the most demanding yet rewarding procedures to perform. The reconstructed auricle has an immeasurable positive psychological and emotional impact on the self-esteem of a young child with microtia. This article reviews the history and pertinent evaluation of microtia repair, and it includes a detailed description of the surgical techniques currently considered the criterion standard.

The image below depicts microtia.

Grade I microtia. Grade I microtia.

History of the Procedure

Microtia repair was first reported by Sushruta in 600 BC. He noted that the surgeon should "slice off a patch of living flesh from the cheek of a person devoid of ear lobes in a manner so as to have one of its ends attached to its former seat.”[2] In 30 AD, Celsus recommended advancement flaps, and, in 1575, Pate used an ear prosthesis made of enameled metal.

Following these initial descriptions, a major progression occurred with the use of cartilage to repair the defect. In 1920, Gillies first reproduced the auricle by burying rib cartilage under the mastoid skin and then separating the ear from the underlying skin with a cervical flap.[3] Subsequently, in 1937, Gillies also attempted maternal cartilage for ear reconstruction but noted problems with resorption.[4] Tanzer reemphasized the use of autogenous cartilage in 1964.[5] He commented on the advantages of its high viability, resistance to shrinkage and softening, and lower incidence of resorption. Other authors have also supported the use of autogenous rib cartilage as the most reliable material in reconstructing microtic ears, including a description by Brent of more than 1200 cases of microtic ear reconstruction.[6]

Problem

Microtia is strictly defined as a small auricle, but an array of deformities exists, each having different implications in terms of optimum treatment and expectations. No universal classification system of microtia predominates; however, multiple authors have described systems based on the degree of deformity and specific anatomic parts. Marx described a microtia staging system that consists of the following 4 levels:[7]

  • Grade 1 microtia is characterized by an abnormal auricle with all identifiable landmarks.

  • Grade 2 microtia consists of an abnormal auricle without some identifiable landmarks.

  • Grade 3 microtia is recognized by a very small auricular tag

  • Grade 4 microtia is anotia.

Weerda describes the following 3 types of microtia:[8]

Grade I microtia is characterized by a mild deformity with a slightly dysmorphic helix and antihelix, as depicted in the 1st image below. All the major structures are present, and no additional cartilage is necessary during surgical repair. Characteristic lop ear and cup ear abnormalities are categorized into this group. Also, a Stahl ear has features of a third crus with a flattened scaphoid fossa and deficient antihelix, as depicted in the second image below.

Grade I microtia. Grade I microtia.
Stahl ear deformity with third crus. Stahl ear deformity with third crus.

Grade II microtic ear deformities have all major structures present to some degree, but repair requires cartilage or skin, as depicted in the image below. The external auditory meatus is present but with stenosis. Typical defects include severe cup ears, as depicted in the 1st image below.

A: Grade II microtia. B: Grade III microtia. A: Grade II microtia. B: Grade III microtia.

The grade III abnormality is characterized by few, if any, landmarks. If present, the lobule is usually positioned anteriorly. Peanut and anotic ears are examples of grade III malformations, as depicted in the second image above.

The Tanzer microtia classification is based on the description and location of the defect, as follows:[5]

  • Type A microtia consists of an anotic ear.

  • Type B microtia describes a completely hypoplastic ear with or without aural atresia.

  • Type C microtia consists of hypoplasia of the middle third of the auricle.

  • Type D microtia is characterized by hypoplasia of the superior third of the auricle.

  • A prominent ear is classified as type E microtia.

Aguilar and Jahrsdoerfer simplified the classification into the following 3 categories:[9]

  • Grade I microtia is any normal ear that is reduced in size.

  • Grade II microtia is an ear with structural deficiencies.

  • Grade III microtia is characterized by the classic peanut deformity and includes the anotic ear.

Other authors have a more complex system consisting of numerous categories. For example, Fukuda systematizes ear deformities into 9 types based on the shape of the vestige.[10]

Another classification system developed by Firmin focuses on the type of incision required for placement of the cartilage framework, with deformities divided into 3 types:

  • Type 1 correlating with the incision for a lobular type deformity

  • Type 2 correlating with the incision for a large conchal remnant deformity

  • Type 3 correlating with the incision for a small conchal remnant deformity and varied atypical vestiges

Firmin’s classification has been endorsed in recent literature as a more useful system with practical implications for surgical technique.[11] An updated and more detailed version of this classification awaits publication and will take into consideration not only the type of incision, but also the type of framework required and the type of additional cartilage used for projection.[12]

Epidemiology

Frequency

The incidence of microtia is 1 per 5,000-20,000 births. The incidence of microtia is 1 per 900-1200 births in the Navajo population and 1 per 4000 births in the Japanese population.

The male-to-female ratio is 2.5:1. Microtia is typically unilateral rather than bilateral (unilateral-to-bilateral ratio of 4:1). The right ear is affected more frequently than the left ear (right-to-left ratio of 3:2). The reason for this predilection remains unclear.

Etiology

Although no specific chromosomal abnormality for microtia has been cited, a multifactorial inheritance is considered. An immediate family history is noted in approximately 5% of patients. Prenatal infections and teratogens such as isotretinoin, thalidomide, and maternal rubella have been implicated.

Presentation

Fifty percent of microtia cases are associated with congenital syndromes. Hemifacial microsomia is a spectrum of craniofacial malformations characterized by asymmetric facies with microtia, malar or mandibular hypoplasia, cleft palate, tragal skin tags, upper eyelid colobomas, and facial nerve paralysis, as depicted in the image below. Goldenhar syndrome is a nonhereditary variant of hemifacial microsomia associated with abnormal development of the first and second branchial arches. Associated findings include preauricular nodes, epibulbar dermoids, malar and mandibular hypoplasia, and vertebral, cardiac, or renal abnormalities.

Hemifacial microsomia with microtia. Hemifacial microsomia with microtia.

Treacher Collins syndrome (ie, mandibulofacial dysostosis, Franceschetti syndrome) is an autosomal dominant inherited disease isolated to chromosome arm 5q. Typical features in addition to microtia include stenosis or atresia of the external auditory canal, middle ear abnormalities, antimongoloid slanting of the palpebral fissures, lower lid colobomas, partial or near absence of eyelashes, microstomia, hypoplastic zygoma and mandible, and a narrow or cleft palate. Oculoauricular vertebral dysplasia is characterized by microtia with cervical spine anomalies and epibulbar dermoids.

A number of associated abnormalities and syndromes may coexist with microtia and highlight the necessity for a thorough head and neck examination with attention to recognizing these features. In a review of 1200 cases of microtia, associated deformities included branchial arch deformities (36.5%), facial nerve weakness (15.2%), cleft lip and/or palate (4.3%), urogenital defects (4%), cardiovascular malformations (2.5%), and macrostomia (2.5%).

The evaluation for microtia repair begins with a head and neck examination that emphasizes facial asymmetry; retrognathia (or other airway concerns common to this group); integrity of the facial nerve; quality of non–hair-bearing skin in the vicinity of the auricle, hairline, position of the remnant auricle, and future lobule; and condition of the contralateral ear. The patient should be referred to an otologist if other middle or inner ear abnormalities exist.

A retrospective study by Billings et al indicated that in patients with unilateral microtia/aural atresia, there is an increased likelihood that the normal ear will suffer hearing loss and middle ear effusion requiring management with a tympanostomy tube. The study, which included 72 patients, all under age 3 years, found that 14 (19.4%) underwent tympanostomy tube placement, compared with a reported 6.8% of children under age 3 years in the general population.[13]

Indications

Patients who undergo microtia repair are typically in the pediatric age group, but patients may also include adults who have delayed seeking repair. The operative indication is the patient's desire to repair the congenital deformity. Although repair is elective in the sense that an absent auricle is not life threatening, the negative psychosocial impact of a facial malformation may cause irreparable damage to an individual's self-image. Completion of the surgical repair before the patient enters the first grade has concrete advantages during the adolescent years and is usually encouraged. However, surgical repair in younger children is usually limited by the size of their chest walls and donor site cartilage. The goals of repair should be clearly discussed to establish realistic expectations. Microtia repair aims to make the reconstructed ear less conspicuous, but the result is not necessarily an ear that appears normal under close scrutiny.

Children with microtia commonly have atresia of the ear canal as an associated abnormality. The atresia repair is performed after the microtia reconstruction to preserve the delicate mastoid skin essential for an optimal appearance of the ear. The auricle is subtly repositioned to align the meatus with the new external auditory canal. Some surgeons reserve the repair of atresia for bilateral cases because they consider the risk of damaging the facial nerve to outweigh the benefits of the operation. However, others feel that repair of a unilateral atresia is appropriate for select patients when it is performed by a qualified otologist. The repaired ear can dramatically improve hearing because it provides binaural functional hearing.[14]

Relevant Anatomy

The external ear and middle ear are derived from the first and second branchial arches. By the fifth week of gestation, the external ear begins to develop as 6 small buds of mesenchyme along these arches. These hillocks, called the auricular hillocks of His, fuse during the 12th week. By the 20th week, the adult auricle is formed. Each hillock of His represents an anatomic structure of the ear, as depicted in the image below. The first 3 hillocks are formed from the first pharyngeal arch. The first hillock forms the tragus, the second hillock develops into the helical crus, and the third hillock eventually becomes the helix. The remaining 3 hillocks are formed from the second pharyngeal arch. The fourth and fifth hillocks become the antihelix, while the sixth hillock forms the antitragus.

A: Hillocks of His. B: Derivatives of the hillocks A: Hillocks of His. B: Derivatives of the hillocks of His. The first 3 hillocks are derived from the first pharyngeal arch. The last 3 hillocks are derived from the second pharyngeal arch. The first hillock forms the tragus; the second forms the helical crus; the third forms the helix; the fourth and fifth form the antihelix; and the sixth forms the antitragus.

The named landmarks of the normal adult ear include the helix, antihelix, tragus, antitragus, lobule, concha cavum, concha cymba, scaphoid fossa, triangular fossa, and crura of the antihelix, as depicted in the image below. At birth, the height of the ear is 66% of adult size. The ear is approximately 85% of full size by age 6 years and 90% by age 9 years. The height of the average adult ear ranges from 5.5-6.5 cm, achieved at age 15 years in boys and age 13 years in girls. The width is approximately 55% of the height. Because the final adult size is nearly achieved by age 6 years, the contralateral normal ear serves as a reasonable template of the final auricular height. The normal protrusion from the mastoid is 1.5-2 cm or approximately 15-20°.

Named landmarks of the normal auricle. Named landmarks of the normal auricle.

The primary blood supply is from the superficial temporal artery and the posterior auricular artery. Sensory innervation is provided by the greater auricular nerve (C3), lesser occipital nerve (C2, C3), auricular branch of cranial nerve (CN) X, auriculotemporal nerve (V3), and sensory twigs of CN VII and IX.

Contraindications

A contraindication for microtia repair is a patient who is too young and has inadequate chest wall development. Anxious parents often request surgical intervention at the earliest age possible, but reconstruction is usually delayed until the patient is aged 5-6 years. Moreover, the small degree of emotional maturity that occurs in the following 1-2 years often significantly affects postoperative care.

A relative contraindication relates to the expected outcomes of this challenging operation and the degree of initial auricular deformity. Because even the best repairs cannot withstand close inspection by a layperson, one should exercise caution when repairing ears that are only mildly deformed (eg, grade I microtia, grade II microtia). Smaller procedures using common otoplasty techniques with scoring and sutures are often more appropriate in such circumstances.

 

Workup

Imaging Studies

Atresia repair candidacy is dictated largely by radiographic findings of the middle ear space, and a temporal bone CT scan is essential in the future.

Other Tests

Formal audiography is prudent to document the level of hearing of both the microtic and uninvolved ear. A patient with bilateral atresia requires a bone conduction hearing aid that is placed as soon as possible and replaced often during infancy for speech and language development.[15]

 

Treatment

Medical Therapy

Nonsurgical options for the treatment of microtia include simple coverage of the microtic ear with the patient's hair. This way, the affected child may decide for or against having surgery at a future date. A prosthetic ear is another alternative and is used more frequently following total auriculectomy for cutaneous malignancies. More advanced models use bone-anchored devices and provide an excellent aesthetic appearance with minimal surgical procedure. Disadvantages of prosthetic ears relate to the daily care needed and the concern over inadvertent dislodgement, particularly in social situations.

Surgical Therapy

Silastic-Dacron implants, as depicted in the image below, were once often used because of their reproducible framework and lack of donor site morbidity. Unfortunately, most alloplastic materials are prone to extrusion when placed under such thin skin coverage, and they have low tolerance to trauma. Recent enthusiasm has developed for the use of porous, high-density, polyethylene implants (eg, Medpor). These implants must be buried under a thicker layer of vascular tissue, usually a transposed temporal parietal fascia flap.

Silastic-Dacron alloplastic implant. Silastic-Dacron alloplastic implant.

In animal models, these grafts have the capability to heal by secondary intention or by skin grafting if they become exposed to the environment.[16] In one of the few long-term clinical studies of reconstructions with these grafts, involving 786 reconstructions over 18 years, Reinisch demonstrated high initial complication rates at the outset of his study, but an overall decrease in complication rates at 12-year follow-up after careful improvements were made in implant design and graft technique.[17]

Although this more recent generation of alloplastic implants may be less problematic than silicone, these implants maintain a risk of extrusion and infection that limits their applicability in primary microtia repair. One must also bear in mind that the external ear is subject to repeated minor trauma that the alloplastic implant must be expected to withstand over a lifetime.[18] More importantly, failure of alloplastic implants may complicate future autogenous costal cartilage reconstruction by violating the delicate mastoid skin. Reconstruction with autogenous cartilage remains the standard treatment.

Timing

The ideal age for auricular reconstruction depends on a few variables. The child's torso should have achieved sufficient growth and development so as to allow for enough costal cartilage needed for the framework. Maturation and motivation in the child patient is preferable; postoperative cooperation is greatly increased when the patient desires the repair. Psychosocial issues can be powerful to a young child and this should be considered with regard to school. In all, most children begin their repair at about age 6 years.

Recent literature highlights a possible exception to the traditional timing of surgery in the case of patients with concomitant microtia and aural atresia. As discussed previously, microtia repair traditionally precedes atresia repair to preserve blood supply and surgical planes required for auricular reconstruction. While microtia repair usually begins at age 6 years, the multiple-staged surgeries required by the autogenous costal cartilage technique may last approximately 24 months. Therefore, atresia repair may not occur until age 8 years or later, which is after the critical period of central auditory development that occurs around age 3-5 years.[19]

Several authors have investigated techniques to accelerate the repair process to allow for earlier binaural hearing during this critical period of development. A recently developed technique using Medpor alloplastic implants allows atresia repair prior to microtia repair, and in a study of 31 patients who underwent this procedure, repairs were performed at an average age of 4.2 years, much younger than previously reported patients, and with comparable short-term outcomes.[20] While this technique is promising, long-term outcome data are needed to adequately assess its efficacy.

Preoperative Details

Use an exposed radiograph film to trace the outline of the contralateral normal ear and to serve as a template for reproducing auricular details, especially the contour of the triangular fossa and scaphoid fossa. When bilateral microtia exists, use the ear from a parent as a template. The radiograph film is also useful for determining the amount of costal cartilage needed during harvest, thereby avoiding any excessive resection and morbidity.

Careful measurements are needed to ensure symmetry of the new auricle in terms of vertical height, posterior position, and oblique orientation. A malpositioned ear is often more conspicuous than one that is properly located but lacking in fine definition. Important landmarks for reference include the lateral canthus, alar lobule, and oral commissure. Use exposed radiograph film for positioning the ear with respect to these reference points.

Intraoperative Details

The classic microtia repair with autogenous costal cartilage involves the following 4 stages, each separated by 3 months:

  1. Cartilage harvest and implantation

  2. Lobule transfer

  3. Lateralization with skin graft

  4. Creation of the tragus

The fourth stage is often not required because a rudimentary tragus may be found.

Cartilage harvest and implantation

This initial stage is the most involved and requires a few days of hospitalization. The contralateral chest, at the confluence of the sixth and seventh ribs for the primary platform of the ear and the floating eighth rib for the helical rim, is used to obtain the donor costal cartilage. When the cartilage is obtained, great care is taken to split the rectus muscle rather than cut it, thus greatly reducing the postoperative pain and splinting. Further chest deformities may be reduced by retaining a rim of the upper margin of the sixth rib cartilage, thus tethering the remaining rib framework to the sternum and preventing outward flaring of the posterior rib border.

The cartilage graft is carved with traditional woodworking gauges and scalpels, as depicted in the 1st image below. Power instrumentation is not used, since its forces may damage the cartilage. The preoperatively prepared radiographic tracing serves as a template for carving and building the framework, as depicted in the first image below. The contours of the helix and antihelix are exaggerated to accommodate the thicker skin flap that invariably blunts these details after implantation. The eighth rib cartilage is carved and secured to the framework with 4-0 clear nylon, as depicted in the second image below.

Instruments used for carving costal cartilage. Instruments used for carving costal cartilage.
Carved auricular template. Carved auricular template.

An accurate outline for the position of the new ear is made with respect to the contralateral normal ear and relative to the lateral canthus, nasal ala, and oral commissure. Relatively small discrepancies of vertical height can be detected when both ears are in view simultaneously (ie, frontal view). A low anterior hairline should not influence the position of the graft. With bilateral microtia, refer to absolute numbers rather than symmetry; an understanding of the standard ideal auricular position in the head is imperative. The superior aspect is usually at the level of the supratarsal crease, the inferior lobule is at the subnasale, the root of the helix is 6.5-7 cm posterior to the lateral canthus, and the long axis of the ear is roughly 15° off the vertical plane.

To obtain optimal definition of the new ear, elevate the subcutaneous pocket as thinly as possible. Resect and bank all rudimentary auricular cartilage in the postauricular scalp for use during the third stage. Place 2 microsuction drains behind and over the graft, keeping the cartilage in position and maintaining close apposition between the framework and overlying skin. To maximize auricular contours, as depicted in the image below, tight adherence of the skin to the cartilage is essential. In most cases, remove drains on the fourth or fifth postoperative day.

Microdrains in place. Microdrains in place.

Lobule transfer

The second stage of reconstruction is the lobule transfer. Perform this procedure approximately 2-3 months after stage I. The remnant lobule is typically found in a superior and anterior position and is moved to the inferior border of the reconstructed framework as an inferiorly based transposition flap. Partially fillet the lobule open to cover the medial and lateral surfaces of the cartilage graft, as depicted in the image below.

Lobule transfer. Lobule transfer.
Inferiorly based lobule. Inferiorly based lobule.
Lobule transferred. Lobule transferred.

Lateralization with skin graft

Perform stage III 3 months later. Stage III consists of the elevation of the framework from the mastoid and the creation of a postauricular sulcus. Make an incision along the posterior periphery of the cartilage graft with care to minimize bringing hair-bearing scalp onto the lateral surface of the ear. As the ear is lifted, preserve a layer of soft tissue on the cartilage to support the skin graft. Undermine the posterior mastoid skin and advance it forward to resurface the new scalp defect. The banked cartilage from the first stage is then harvested and carved into a wedge for placement as a support buttress behind the ear to augment projection, as depicted in image B below. Create a small pocket for this graft so that it is not exposed to the skin graft. Alternatively, elevate a sleeve of temporalis fascia and rotate it inferiorly for coverage of the cartilage. Secure a split-thickness skin graft to the posterior surface of the framework, as depicted in image C below.

A: Stage III, skin incision for ear elevation. B: A: Stage III, skin incision for ear elevation. B: Wedge of cartilage placed as buttress graft for projection support. C: Skin graft in position.
After Stage III lateralization. After Stage III lateralization.

Creation of the tragus

The final stage is construction of the tragus and conchal bowl. For unilateral microtia, obtain a composite graft from the concha cymba of the contralateral normal ear. Insert the graft through a small J-shaped incision in the area of the anticipated tragus, as depicted in the image below. The reconstructed tragus produces a shadow that mimics an external auditory meatus until atresia repair is performed.[21] In cases of bilateral microtia, in which contralateral conchal cartilage is not available, build the tragus using residual costal cartilage and wrap the preauricular skin around the graft. Brent described a technique of incorporating the tragus during the initial stage by securing an additional cartilage graft to the main framework.[6] This method is particularly advantageous in patients with bilateral microtia.

A: Stage IV, composite graft for tragal reconstruc A: Stage IV, composite graft for tragal reconstruction. B: Shadow created by tragus.
After atresia repair, with new ear canal. After atresia repair, with new ear canal.

Bilateral microtia is characterized by several other unique considerations. The first stage to each side is separated by several months to minimize postoperative splinting from bilateral chest wounds during cartilage harvesting. Conversely, subsequent stages may be performed simultaneously. Lastly, tragal reconstruction is modified, as discussed above.

Several surgeons have recently modified the standard 4-stage repair and have advocated a combined 1- to 2-stage approach. This concept is appealing because it decreases hospitalization, accomplishes the procedure with fewer patients in the operating room, and eases the patient's anxiety. Song and Song described a 1-stage repair that involved an ultrathin skin flap and a subcutaneous tissue flap.[22] This technique allowed for creation of the sulcus simultaneously with the framework construction. Two of 15 patients (13.3%) had complications that required an additional 1-month hospitalization. Also, this procedure still required patients to pursue secondary procedures (eg, tragal construction, lobule repositioning) to obtain a more aesthetically pleasing reconstruction.

Other authors such as Nagata[23] have described techniques that transpose the lobule during the creation of the framework; that is, stages I and II are combined. These techniques include the building of a tragus with the initial framework, thus completing the microtia repair in 2 stages. Brent advocates lobule transfer and elevation of the framework if the remnant lobe is short. A small vestigial lobule allows for preservation of a significant skin bridge and an adequate blood supply to the lobule.

Nagata recently introduced 2 modifications to standard reconstruction techniques. The first is a skin grafting method that involves raising an ultra-delicate split-thickness skin graft in continuity with full-thickness skin to cover the scalp defect and create the postauricular sulcus during stage III of repair. This single composite flap, while technically difficult and time-consuming to create, allows for precise surgical planning and limits visible scarring to the inferior portion of the ear.[24]

The second modification, described by Kawanabe and Nagata,[25] is a costal cartilage harvesting technique whereby the perichondrium is left intact at the donor site and “leftover” cartilage, remaining after the carving of the auricular framework, is returned to the perichondrial pocket, allowing for the regeneration of cartilage. In their study of 273 patients who underwent repair using this technique, complications rates were reduced: 1 patient developed a pneumothorax and no patients developed chest wall deformities.

Furthermore, a follow-up study showed histological maturation of regenerated cartilage into costal hyaline cartilage at 12 months after surgery.[26] This finding is particularly promising as it points to future opportunity for patients whose surgical outcomes are limited by the amount of costal cartilage available for use.

When the microtia repair is complete, a preexisting low hairline may result in varying amounts of hair overlying the elevated framework. This hair may be addressed simply with trimming, electrolysis, laser hair removal, or adequate coverage of the auricle with the patient's hairstyle. If these conservative measures fail to address the problem, the skin may be excised and the graft resurfaced with a skin graft. To create good color match, a full-thickness skin graft from the posterior surface of the contralateral ear is used to cover the framework. Depilation may also be performed preoperatively in the anticipated surgical area to create hairless skin prior to any framework implantation.

Postoperative Details

Postoperatively, patients are instructed to refrain from contact sports for 6 weeks, after which they are allowed to participate in all reasonable activities without restriction. The reconstructed ear with autogenous costal cartilage tolerates trauma relatively well, including blows from soccer balls, abrasion from wrestling matches, and insect stings.

Follow-up

Routine follow-up care is indicated for postoperative wound healing. Once the atresia portion is complete, observing the patient annually may be worthwhile; however, no additional problems are anticipated.

Complications

During stage I, operation on the chest wall may result in pneumothorax, chest wall deformity, and atelectasis secondary to limited inspiration due to pain. A postoperative chest radiograph is obtained in the recovery area to confirm the absence of a pneumothorax. Pneumothorax, chest wall deformity, or atelectasis, if present, can usually be managed conservatively rather than requiring a chest tube because the source of air is from violation of the parietal pleura and not the visceral pleura with continued air leak from the lungs. When encountered intraoperatively, the wound is closed over a small red rubber tube set to suction, and it is withdrawn during a Valsalva maneuver.

Procedures with framework implantation may result in hematomas, seromas, chondritis, and graft or skin ischemia. Skin necrosis is an unusual complication, but it must be recognized promptly and managed aggressively to minimize subsequent cartilage resorption, infection, and permanent loss of definition. A small area of skin necrosis may heal with meticulous wound care and gentle debridement, as depicted in the image below. However, a larger area may require mobilization of a vascularized temporoparietal fascial flap to cover the cartilage and to support a skin graft. Hyperbaric oxygen therapy is recommended as soon as impaired vascularity is noted postoperatively.

Exposed cartilage. Exposed cartilage.

Despite adequate measures to obtain projection during stage III, the reconstructed ear may lack sufficient protrusion compared with the contralateral ear. An alternative to further manipulation of the framework is an otoplasty to the normal ear. The projection of the unaffected ear may be reduced to create a more symmetric appearance. A rare but significant complication of this procedure is facial nerve injury. In 25-30% of patients with atresia, the facial nerve takes a sharp turn anteriorly at the level of the second genu. The nerve crosses the lower third of the middle ear, exits the glenoid fossa, and is vulnerable to injury in the preauricular area. Also, the facial nerve may lack a vertical segment in patients with low-set ears and a course in the soft tissue over the mastoid.

Outcome and Prognosis

The outcomes of microtia repair are reflected in the psychological benefit and satisfaction of the patient and/or parent. Brent surveyed his patients in 1992 and noted that those grading themselves as severely affected prior to surgery were 100% pleased with the result.[27] Among patients who considered themselves moderately disturbed by microtia and underwent the procedure when younger than 14 years, 95.5% were satisfied with the decision to pursue surgery. In regards to the chest donor site, 62% of all people surveyed reported no concern, and 35% noted the scar as a concern but thought the operation to be worthwhile. Few patients (3%) expressed concern about the appearance of the chest scar.

A retrospective study by Sakamoto et al suggested that in patients with congenital aural atresia, an external auditory canal area of over 72.3 mm2 is the most significant predictive factor for a successful long-term hearing outcome from external auditory canal construction/tympanoplasty. The study, which included 51 ears with congenital aural atresia, reported that a mesotympanic depth of over 5.5 mm, a mesotympanic height of over 4.6 mm, and an external auditory canal diameter of over 9.5 mm also predicted a favorable result.[28]

Future and Controversies

The future of microtia repair includes the development of tissue engineering. Restrictions of present techniques include the limited availability of cartilage to repair the defect and the surgical morbidity of autogenous costal cartilage. Investigations have begun in which a small amount of cartilage may be harvested and expanded in vitro and in vivo. The initial procedure, which was proposed by Peer, used diced autogenous cartilage and placed it in a Vitallium ear mold.[29] The mold was subsequently banked and harvested, but the results were not consistent.

More recently, investigations have demonstrated the ability to seed bovine chondrocytes on a biodegradable template and implant these molds into an athymic mouse; this process resulted in an auricle-shaped cartilage. Other studies have shown that autogenous transfer of tissue-engineered cartilage is possible in a rabbit model. The cells are placed on a biodegradable template that engineers 3-dimensional morphology and guides the growth of the new cartilage into an anatomic graft, as depicted in the image below.

Tissue-engineered cartilage for potential microtia Tissue-engineered cartilage for potential microtia repair.

Despite these initial successes, the development of cartilage that retains its size and shape as well as its viability in an immunocompetent animal model remains a challenge. A successfully engineered auricle will be one that incorporates a biocompatible scaffold, optimal chondrocyte source, and an ability to tolerate an immunocompetent host by closely resembling the histological make-up of native cartilage. There continue to be numerous developments in this field and tissue-engineered cartilage may represent the implant of the future because of its ability to encompass the advantages of alloplastic and autogenous grafts.[30]