Contemporary Treatment of Microtia–Atresia

Abstract

Microtia–atresia is a congenital deformity affecting the external ear and ear canal that can present with varying degrees of severity and morbidity. Treatment occurs along a spectrum and primarily centers on improving aesthetic appearance. Many cases of microtia will not be effectively treated with conservative measures and will require some form of reconstruction. There are several options available, including porous polyethylene implants, autologous rib grafting, and autologous chondrocyte frameworks. Equally significant is the treatment of hearing loss, as many patients with microtia–atresia will have a component of conductive hearing loss. This article aims to comprehensively review contemporary treatment modalities for microtia–atresia and discuss the advantages, disadvantages, and practicality of each. Treatment and reconstruction often take a multidisciplinary and multistaged approach to achieve optimal results, with ideal management determined by each patient's individualized needs.

Keywords

microtia - reconstruction - congenital

Microtia and atresia are congenital deformities involving the external ear and ear canal, with an incidence ranging from 3 to 10 in every 10,000 live births.[1] Microtia refers to poorly developed or misshapen external ear structures and is often accompanied by atresia or abnormality of the external ear canal. Microtia is bilateral in 10% of cases, and in unilateral cases, it is twice as likely to affect the right ear.[2] It generally has a sporadic presentation, although it can be associated with certain conditions such as Goldenhar's syndrome, Treacher Collins syndrome, and hemifacial microsomia.[1] [3]

Both microtia and atresia can have varying degrees of severity and morbidity. Microtia is most commonly graded using the Marx classification, ranging from Grade I to Grade IV.[2] Grade I refers to deformity in which all the subunits are present, but the auricle is at least two standard deviations smaller than normal. The ear canal is generally patent.[2] Grade II microtia includes deformity of the upper one-half to two-thirds of the auricle with the remainder of the external ear having identifiable landmarks and anatomy. The patient may have a component of canal atresia. Grade III, often referred to as “peanut ear,” is the most common form of microtia, where a small remnant of cartilage is usually present with an anterosuperiorly rotated lobule and complete aural atresia is often found. Grade IV, or anotia, has complete absence of the external ear structures and ear canal.[2] The severity of aural atresia can vary greatly. Mild iterations may present as a stenotic ear canal with a rudimentary tympanic membrane, whereas severe forms generally have no identifiable ear canal with middle ear structures that are deformed or absent.[4] Other methods of grading microtia–atresia include Tanzer and Nagata classification, which focus more on approaches and techniques required for reconstruction.[5]

Treatment of microtia generally focuses on the aesthetic appearance of the deformity, with various reconstructive options available. For patients with mild cosmetic and functional deformity, observation without intervention may be a viable option. Patients may opt for prosthetic placement if they are appropriate candidates.[2] For cases that are better treated with surgical reconstruction, options include porous polyethylene (PPE) implants and autologous rib graft frameworks.[6] Equally significant is the treatment of hearing loss, as many patients with microtia–atresia will have a component of conductive hearing loss. Treatment often depends on multiple factors but is generally accomplished with bone-anchored hearing devices that can be implanted or worn on a headband. Patients with bilateral hearing deficits require a more urgent need for intervention, as they are at higher risk of speech and developmental delay.[1] The purpose of this article is to review contemporary treatment modalities for microtia–atresia and discuss the advantages, disadvantages, and practicality of each.

Evaluation

The optimal age of microtia management depends on the severity and type of treatment planned for the patient.[5] In general, the auricle is fully developed and adult sized by the age of 8.[2] For reconstruction with autologous rib grafting, surgery is usually performed between 7 and 11 years of age, when the rib and costal cartilage is more mature.[5] [6] PPE implantation can be performed at a younger age (4–5 years), as it does not involve donor site morbidity or considerations.[6] [7] In addition to age, it is essential to take into account the risk of social stigma and emotional distress associated with microtia deformity. Initiating treatment earlier increases the likelihood that patients will be able to avoid bullying and ridicule in school.[6]

Prior to any treatment, patients should be carefully examined to determine what level of management is most appropriate. This should begin with a thorough history and physical examination, with special attention given to the head and neck. Any abnormally developed or syndromic features should be noted such as hemifacial microsomia, dysmorphia, and cleft lip or palate. A careful eye, skin, and facial nerve exam should be performed. Facial symmetry should be evaluated, and the location of the auricle on both sides should be noted.[4] The shape, size, and level of development of the ear should be reported and compared with the contralateral side. A normally developed ear will grow to approximately 6 cm in height with an auriculocephalic angle of 20 to 30 degrees and a 20-degree backward slope from the vertical.[2] The ear canal or remnant of the ear canal should be carefully evaluated to assess the severity of atresia.

Many patients with microtia–atresia will have some level of hearing loss that should be assessed early, usually during infancy with auditory brainstem response testing.[2] Patients will often have a moderate-to-severe conductive hearing loss from 40 to 65 dB, although up to 15% of patients will have a concomitant sensorineural hearing loss.[2] [4] Hearing should also be tested on the contralateral ear, regardless of deformity. If a patient is not old enough for surgery, early intervention with conductive hearing aids can be initiated.[4] At around 5 to 6 years of age, a high-resolution computed tomography (CT) scan should be performed to assess the microtia deformity and evaluate the patient for surgical candidacy. CT imaging is also essential in the assessment and grading of aural atresia, which is done using the Jahrsdoerfer grading scale. The Jahrsdoerfer grading scale is a 10-point grading scale that is used to predict the likelihood of hearing improvement after atresiaplasty.[4] Patients with a score of 7 or more are 85 to 90% more likely to have a favorable outcome after surgery. A score of less than 6 denotes a poor surgical candidate.[2]

Treatment Options

When considering treatment, it is always important to discuss the limitations and expectations of surgery with the patient and family.[5] Intervention occurs along a spectrum, and choice of management is often contingent on the severity of the malformation. Many patients with mild deformity of the auricle may not require any treatment, whereas some may pursue interventions purely for cosmetic or functional purposes, such as fitting for hearing aids and glasses.[2] For patients who are poor surgical candidates or have insufficient tissue for surgical reconstruction, prosthetic auricles may be considered. Silicone prosthetic auricles can be fashioned by a prosthetic specialist who will use the contralateral ear to mold an aesthetic match on the side of the deformity. The prosthesis can be affixed using adhesives or osseointegrated implants and often results in a favorable aesthetic result. Unfortunately, prosthetics can be expensive with limited longevity. Children may be prone to losing the device, and changes to skin color may result in a poor aesthetic match.[2] [6]

Surgical Reconstruction

Many cases of microtia will not be effectively treated with conservative measures and will require some form of reconstruction. There are several options for reconstruction, including PPE implants, autologous rib grafting, and autologous chondrocyte frameworks. The choice between these depends on several factors including the severity of the deformity and functional goals postoperatively.[6] Reconstruction with costochondral rib grafting is generally completed in several stages, and donor site morbidity must be taken into consideration. It is usually performed between the ages of 7 and 11, when the costal cartilages have sufficiently matured.[5] Alloplastic implants, often made of PPE (Supor, Poriferous Surgical), have become increasingly popular as the procedure can be done at a younger age with fewer steps and less morbidity. However, this usually requires the use of a temporoparietal fascia (TPF) flap, which is technically difficult and can result in failure or necrosis of the flap.[6] There are advantages and disadvantages to each method, and the choice of approach should be made on a case-by-case basis.

Autologous Rib Graft Frameworks

Microtia repair with autologous rib has been performed since the early 1900s and has good aesthetic and durable results.[5] There are several popular techniques that generally require a multistaged approach. The use of autologous rib grafting for microtia was first pioneered by Gillies in the 1920s, who buried a rib graft under the skin of the mastoid and later separated it with a cervical flap. This was often complicated by resorption of the graft framework.[3] The method was modified in 1930 by Pierce, when he added a skin graft to the posterior aspect of the ear and a tubed flap to better reconstruct the helix.[5] [8] Unfortunately, progressive cartilage resorption continued to be a persistent complication. The modern technique of autologous rib reconstruction was pioneered by Tanzer in the 1950s, paving the way for longer-lasting and reliable results with limited resorption.[5] [9] Today, techniques described by Brent, Nagata, Tanzer, Beahm, and Walton serve as the reference and foundation for modern techniques.[5] [9] [10] [11] [12] [13]

The Brent technique is a four-staged approach that is known to have reliable and lasting results.[10] [13] The first stage involves harvesting the rib cartilage and constructing a framework that is inserted into a subcutaneous pocket at the desired ear location ([Fig. 1]). The rib is usually harvested on the side contralateral to the deformity. The base of the framework is constructed from the synchondrosis of ribs 6 and 7, with the helix formed from the free-floating cartilage of rib 8. When creating the framework, features and details of the ear should appear exaggerated, as the effect will be blunted after placement into the subcutaneous tissue. An ear template can be used to establish the size and location of the pocket, which should be created posterior to existing vestigial cartilage. The tissue pocket should be dissected off of the cartilage and any remnants should be removed. Additional cartilage that will be used later to project the ear can be banked in subcutaneous tissue of the chest. The carved framework is placed inside the subcutaneous pocket at the head, and bulb suction is used to allow the skin to heal to the framework.[5] The second stage consists of lobule transposition and subsequent stages involve sulcus, tragus, and conchal construction. The sulcus is created by elevating the posterior aspect of the framework and inserting banked cartilage, which assists in projecting the ear. A full-thickness skin graft is used to cover the exposed postauricular cartilage.[5] [10] [13]

Fig. 1 (A, B, C) Costal cartilage is harvested from the chest and carved into a framework that is inserted into a subcutaneous pocket.

The Nagata technique is completed in two stages.[11] The sixth and seventh costal cartilages form the base of the framework. The eighth and ninth cartilages make the helix and the antihelix, respectively, and the choncha is constructed from the remaining cartilage. Attention is then brought to the lobule, where a “lazy W” incision is made. This splits the lobule into an anterior and posterior skin flap, and the anterior flap is sutured to the external surface of the tragus. Care is taken to preserve the subcutaneous pedicle in the conchal bowl, which is the blood supply to the W flap. The two free edges are then brought together to form the depth of the intertragal notch, and the W flap and lobule flap are transposed and sutured. A subcutaneous pocket is created, and the vestigial cartilage removed. The framework is then placed into the pocket and bolstered for at least 2 weeks. The second stage takes place 6 months later when a skin incision is made posterior to the helix and a wedge of cartilage is placed to project the ear. A TPF flap is then raised and tunneled to cover the exposed posterior aspect of the framework.[5] [11] Several modifications have been made to the Nagata technique, notably by Chen, Kurabayashi, and Fisher.[5] [14] [15] [16] The Fisher modification allows for the procedure to take place in one stage but is technically difficult.[5] [15]

Park performed a two-flap method consisting of three stages.[17] The first stage involves inserting a tissue expander in a subfascial pocket over the mastoid. The expander is inflated over 5 months to a final approximate volume of 80 to 90 mL. Contralateral rib cartilage is harvested in the second stage to form the ear framework. The tissue expander is removed, and the upper framework is placed in the pocket between the fascia and skin and the lower aspect inserted into the envelope of the lobe. A skin graft and fascial flap is used to cover the posterior aspect. In the third stage, the tragus, concha, and helical crus is created.[5] [15] [17]

Multiple other iterations exist, each with their own strengths and weaknesses. In general, autologous rib grafting and framework creation is considered a complex and difficult procedure, often with multiple stages. While harvesting the rib graft, care has to be taken to avoid violation of the pleura. If this occurs, the defect must be repaired appropriately and the patient is at risk for pneumothorax.[5] A chest X-ray should be performed on all postoperative patients, and patients should be monitored for signs and symptoms of pneumothorax. Most will require overnight observation, and significant pain is a frequent complaint. Complications at the reconstruction site include infection, necrosis, framework exposure, and framework resorption or deformity.[5] Advantages of this technique include reliability of results with no risk of extrusion or reaction to the framework. The technique has been used for many decades and has been proven to provide long-term satisfactory results ([Fig. 2]).[5]

Fig. 2 Two-year postoperative results using an autologous rib–graft framework.

Porous Polyethylene Frameworks

PPE is an inorganic implantable material that is often used in facial reconstruction. It is durable, nonresorbable, and highly biocompatible. The concept of nonbiologic implants was largely introduced in the 1960s by Cronin,[18] who performed reconstructions using Silastic implants. Unfortunately, these implants presented several complications, including high extrusion rates, capsule formation, and poorly healing skin grafts. In 1994, Reinisch described the use of PPE implants. Although initially these were associated with high complication rates, the use of a TPF flap led to improved outcomes ([Fig. 3]).[6]

Fig. 3 (A, B) Three-year postoperative results after TPF flap and PPE framework implantation. PPE, porous polyethylene; TPF, temporoparietal fascia.

Several factors have to be considered to achieve the best results when using PPE frameworks. The recipient tissue bed must have adequate soft tissue coverage, vascularity, and tissue integrity. Importantly, the TPF flap that will cover the implant must be the appropriate size and thickness to prevent implant extrusion ([Fig. 4]). The use of implants allows for reconstruction at an earlier age since maturation of the rib cartilage does not have to be considered. Therefore, reconstruction can take place as early as age 4, when the contralateral ear reaches 85% of the adult size.[6]

Fig. 4 (A, B) A TPF flap is harvested and used to cover the PPE framework. PPE, porous polyethylene; TPF, temporoparietal fascia.

Reconstruction with implants usually takes place in one or two stages, although one stage is often sufficient for satisfactory results. When the procedure is completed in two stages, the second stage will be performed after 3 months when the lobule, tragus, and concha will be reconstructed.[4] Each stage with PPE implantation is generally less morbid than with rib grafting. There is no time spent carving the graft in the operating room, and patients do not experience pain associated with the rib donor site. The procedure can usually be done as an outpatient procedure with patients going home the same day. There are several disadvantages to using PPE implants, including a higher risk of extrusion and immunogenicity due to the use of nonbiologic material. The implant may become fractured, infected, or exposed leading to ultimate failure of the reconstruction. Furthermore, long-term data are limited, although it is generally considered reliable. Lastly, the use of a TPF flap increases the morbidity and complexity of the procedure. Raising the flap while preserving the blood supply can be difficult, as anatomy of the superficial temporal artery can vary vastly, and there is risk of flap failure.[2] [6] [19]

Three-Dimensional-Printed Autologous Chondrocyte Frameworks

Three-dimensional (3D) printing was first used in craniofacial surgery in the 1990s and has further integrated into the field ever since.[20] The technology has been used to develop surgical models and customized guides that have reduced operative times and refined techniques. Due to the morphologic complexity of the human ear, 3D printing can be particularly valuable in the treatment of microtia–atresia. The technology serves to create structurally complex frameworks and scaffolds that precisely mimic the shape of the ear without donor site morbidity usually associated with rib grafting.[5] With tissue engineering, autologous chondrocytes can be printed into completely biocompatible and aesthetically optimal frameworks that do not have the risk of implant extrusion or rejection.[20] Despite this potential, the realistic technological and clinical benefit has not been fully elucidated.[20]

The use of 3D-printed autologous chondrocyte frameworks is, at this point, mostly theoretical.[20] A standardized method of tissue engineering has yet to be established, and there are major obstacles in developing optimal tissue harvesting, propagation, and scaffolding techniques. The implants must have adequate longevity and strength to be able to resist the mechanical forces of implantation as well as good quantity and quality of chondrocytes. Preclinical studies have shown that human chondrocytes can be successfully seeded and propagated onto scaffolds to create cartilage implants, and researchers have developed 3D-printed autologous chondrocyte implants without the use of a framework.[20] In recent clinical trials, 3D-printed chondrocyte frameworks have been successfully implanted into patients, although results and outcomes of the procedure are still unclear.[21] Overall, the integrity, viability, and optimal implantation method for these frameworks has yet to be determined. The use of a subcutaneous pocket places greater force onto the implant, making adequate strength essential. TPF flaps exert less pressure onto the frameworks but are technically difficult and can increase operative time and morbidity.

With recent advancements in 3D printing and tissue engineering, the possibilities within the field of auricular reconstruction have only expanded. While preliminary research shows promise, continued investigation is essential to fully understand the practical applications of 3D-printed autologous frameworks.

Atresiaplasty

Atresiaplasty can be performed on qualified patients to improve hearing and cosmesis but, in general, is not the preferred treatment for hearing loss in microtia–atresia. Hearing outcomes have not been shown to be superior to those achieved with bone-anchored hearing devices and rates of meatal stenosis and recurrence are high. Other reported complications include facial nerve injury and hearing deterioration.[1] If the decision is made to proceed with atresiaplasty, hearing must be evaluated prior to treatment to assess for middle and inner ear abnormalities. A CT scan is obtained to further evaluate the facial nerve, ossicles, pneumatization, vasculature, and other anatomical factors. The Jahrsdoerfer criteria is used to predict the risk of restenosis of the new external auditory canal. This is a 10-point scale that assesses several anatomical factors, with a rating of 7/10 predicting surgical success.[22]

The timing of atresiaplasty depends on the reconstructive technique. With autologous rib grafting, atresiaplasty is usually done after the framework has been inserted in the subcutaneous pocket and can add stages to the repair.[4] Atresiaplasty with PPE implantation is also classically performed after reconstruction. However, Roberson et al found that atresiaplasty could be performed before PPE reconstruction with similar hearing benefits to atresiaplasty after rib graft reconstruction, which would allow for earlier intervention and reconstruction.[23] This involves adding stages to the reconstruction, although some teams have successfully attempted single-stage PPE reconstruction with canalplasty.[6]

Hearing Restoration

Hearing restoration is a salient aspect in the treatment of microtia–atresia, and most patients will have a degree of conductive hearing loss.[1] Bilateral hearing loss must be treated as soon as possible to avoid speech and developmental delay. Options include headband bone conduction devices and percutaneous or transcutaneous bone-anchored hearing aids. The optimal device can vary from patient to patient, and age and severity of deformity must be considered. Unilateral cases do not always require the same sense of urgency and hearing restoration can be timed around the surgical reconstruction.[1] Studies have shown that bone-anchored hearing aid placement can be safely performed in a two-staged procedure after reconstruction with good aesthetic and functional outcomes ([Fig. 5]).[6] [24]

Fig. 5 (A, B) Postauricular placement of a bone conduction implant during the second stage of autologous rib–graft reconstruction. Postoperative positioning of the BAHA sound processor.

Conclusion

Contemporary treatment of microtia is a complex topic. There are numerous techniques and treatment modalities, each with their own advantages and disadvantages. Various considerations must be taken into account including morbidity, complexity, and functional benefit. Microtia–atresia treatment and reconstruction often take a multidisciplinary and multistaged approach to achieve optimal results. Candidates should be evaluated on a case-by-case basis, with the ideal treatment determined by each patient's individualized needs.

Conflict of Interest

None declared.

• References

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Artikel online veröffentlicht:
08. April 2024