External Ear, Aural Atresia Treatment & Management

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.

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.

In animal models, these grafts have the capability to heal by secondary intention or by skin grafting if they become exposed to the environment. 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. More importantly, failure of alloplastic implants may complicate future autogenous costal cartilage reconstruction by violating the delicate mastoid skin.

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.

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.

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.

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.

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.

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.

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. 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.^[5] This method is particularly advantageous in patients with bilateral microtia.

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.^[10] 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 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.

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.

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.

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.

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.

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.

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.^[11] 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.

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.^[12] 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 may represent the implant of the future because of its ability to encompass the advantages of alloplastic and autogenous grafts.