Ear Anatomy

The contours of the normal ear must first be reviewed in order to understand the nature and extent of microtia and approaches to reconstruction ( Fig. 14-1 ). The auricle is an aesthetic sculpture of complex convexities and concavities that are smooth and uninterrupted. The elastic cartilage framework of the auricle is pliable yet structurally strong and resistant to trauma. The soft tissue envelope of the ear is fibrofatty and loose over the lobule and the margin of the helix but thin and fixed over the remaining cartilage framework.

Normal anatomic landmarks of the pinna. A, Helix; B, root of helix; C, antihelix; D, tragus; E, antitragus; F, inferior crus of triangular fossa; G, superior crus of triangular fossa; H, lobule. 1, scaphoid fossa; 2, triangular fossa; 3, concha cymba; 4, concha cavum; 5, intertragal incisura.

Normal adult ear height ranges from 5.5 to 6.5 cm. The ear grows rapidly in the first 2 to 3 years of life, reaching 90% of its adult size by about age 8. Thereafter it grows at a modest rate until it reaches adult dimensions at about 13 years of age in boys and 12 years in girls. The mature horizontal width of the ear is achieved at an earlier age. Protrusion of the ear from the surface of the mastoid should be 1.5 to 2.0 cm, with a conchal mastoid angle between 15 and 20 degrees. The superior margin of the helix is at the level of the tail of the eyebrow in 85% of people. Because the tail of the eyebrow is quite variable, the level of the upper eyelid also may be used as a landmark if the patient has bilateral microtia. The ear inclination is the angle formed by the vertical axis of the face and the longitudinal axis of the ear with the patient in the Frankfort horizontal position. This is approximately 25 degrees, with a standard deviation of 6.2 degrees. Therefore, the longitudinal axis of the ear is not quite parallel with the dorsum of the nose, because the ear is in a slightly more vertical orientation.

Microtia

Microtia deformities present in various shapes and sizes, and currently no precise and accurate classification scheme is universally used. Consideration of the status of the external auditory canal (EAC), middle ear contents, and associated syndromes further complicates attempts at classification of ear anomalies. Microtia deformities are typically divided into three broad categories that overlap a great deal. Type I ( Fig. 14-2, A ) is used to designate ears with mild deformity. All major structures are present to some degree, and reconstruction may or may not require additional tissue. Type II microtia ( Fig. 14-2, B ) includes ears that have major structures present to some degree, but there is a deficiency of tissue with surgical correction requiring the addition of cartilage and skin. Mini-ear, conchal bowl–type microtia, and severe cup-ear deformities are included in this category. In type III microtia, also known as lobule type microtia or peanut-ear deformities ( Fig. 14-2, C ), there are few or no recognizable landmarks of the auricle. The lobule is usually present and positioned anteriorly. Anotia is the complete absence of auricle and lobule. Reconstructive surgeons may find it more useful to simply note the status of the helix/antihelix, the conchal bowl, the lobule, the tragus, and the EAC, because these are the landmarks that dictate the stages of ear reconstruction and the degree of surgical difficulty.

A, Type I microtia with constricted ear and minimal tissue deficiency. B, Type II microtia with absence of major portions of the ear. C, Type III microtia with markedly deformed and small cartilaginous remnant.

Evaluation

Children with microtia typically present to an otolaryngologist during infancy because of the visible anomaly and parental concerns about the child’s hearing. Parents are usually concerned with the short- and long-term effects of monaural hearing on the child’s speech and language development. In addition to the ear, physical examination should focus on the mandibular shape and excursion, maxilla, eyes, and neck to rule out mandibular and maxillary asymmetry, epibulbar dermoids, coloboma, and vertebral anomalies, any of which may indicate that the microtia is part of a syndrome.

Patients with microtia typically have normal hearing in the contralateral ear, although all patients with unilateral microtia should have age-appropriate ear-specific hearing assessment. Radiologic evaluation should include high-resolution computed tomography of the temporal bones to assess the degree of atresia; cervical spine films to rule out vertebral anomalies; renal ultrasound to rule out congenital renal malformations; and Panorex for malocclusion. If multiple anomalies are found, the child is referred to a multidisciplinary craniofacial team for more comprehensive evaluation.

Options for Microtia Management

Microtia reconstruction is elective. Patients and their families should be informed of all the choices so that they can make an informed decision. The options include: 1) observation; 2) prosthetic management, either adhesive or implant retained; 3) single-stage reconstruction with high-density porous polyethylene (Medpor) implant and temporoparietal fascial flap; and 4) staged autogenous costochondral reconstruction. There are advantages and disadvantages of each approach ( Table 14-1 ). One alternative for older children or adults may be the use of an auricular prosthesis. In some institutions, implant-retained auricular prosthesis is recommended as the primary modality. The appearance is often excellent. However, most reconstructive surgeons discourage the use of osseointegrated implant-retained prosthetic management for two reasons: 1) the prosthesis is a synthetic appendage substitute that will forever require daily care, and 2) placement of the implants violates the vascularity of the non–hair-bearing skin over the mastoid and complicates future reconstruction using the other techniques if the patient becomes dissatisfied with the implant-retained prosthesis.

Other alloplast implants used in auricular reconstruction, most notably Medpor, should be mentioned as part of a thorough informed consent even if your institution may not offer these types of reconstructions. Reinisch, Romo, and others have had success using a high-density porous polyethylene (Medpor) auricular implant in conjunction with a temporoparietal fascial flap that obviates the morbidity of the rib graft donor site. This approach allows for reconstruction at an earlier age, and the reconstruction can usually be performed in one stage. Furthermore, the resulting ear may have better definition of the conchal bowl. These advantages are weighed against the potential for implant extrusion, fracture, and a more rigid ear compared with rib graft frameworks.

Tissue engineering technology is emerging and may someday replace the need for rib graft harvesting. To date, though, no reliable tissue-engineered cartilage framework implant is available.

Autogenous Costochondral Microtia Reconstruction

The traditional method for microtia reconstruction uses autogenous rib cartilage to create the auricular framework. The use of rib cartilage in auricular reconstruction was pioneered by Tanzer. Brent and Nagata have contributed significantly to the improvement of microtia reconstruction with rib cartilage. Reconstruction using Brent’s technique requires three to four stages, whereas Nagata describes a two-stage technique. Each stage is separated by 3 to 6 months. The reconstruction can be considered when the patient is approximately 6 to 8 years old, though surgeons using the technique of Nagata often wait until the child is 10 years old to allow for further cartilage growth. Parents are often eager to initiate reconstruction at a young age to avoid psychologic effects to the child, but it is important to wait until enough cartilage can be obtained to create an adult-size ear. The surgeon must develop carving and sculpting skills before undertaking autogenous costochondral microtia reconstruction. For obvious reasons, fresh cadaveric rib cartilage is the best material with which to practice carving and harvesting grafts. If this cannot be obtained, carving the basic auricular framework can be practiced using other materials such as soap. It is important to keep in mind that the auricular framework is not exactly an image of the ear, as the reconstruction must accommodate the soft tissue envelope.