© Borgis - New Medicine 3/2004, s. 66-68
Henryk Skarżyński1, Maciej Mrówka1, Paulina Młotkowska-Klimek1, Bożena Skarżyńska2
Surgical technique of external ear canal reconstruction
1International Center of Hearing and Speech, Institute of Physiology and Pathology of Hearing,
Warsaw, Poland
Head: Prof. Henryk Skarżyński MD, PhD
2Department of Anatomy, Medical University, Warsaw, Poland
Head: Prof. Bogdan Ciszek MD, PhD
Summary
Treatment of congenital ear malformations is one of the most difficult issues in otosurgery. The best surgical solutions depend on results of the techniques which are reproducible and help achieve adequate anatomical and functional effects. Success depends on several conditions, i.e. the patient´s age, specific surgical techniques, type of material used during surgery. The authors of the paper discuss the technique of reconstructing the external auditory meatus in children with congenital defects, which is used at the International Centre of Hearing and Speech, the Institute of Physiology and Pathology of Hearing. Surgical operations performed on a considerable number of patients over a short time period allowed us to acquire essential experience and develop a method which provides permanent and reproducible results. The study material comprises assessment of 31 patients. Postoperative course was uncomplicated, adequate anatomical results were achieved in 28 patients after the first operation, and in 3 patients, after reoperation. Supported by our clinical experience, we believe that a one-year follow-up after surgery helps recognize that the resulting adequate anatomical effect is permanent.
Introduction
No uniform protocol of surgical treatment of congenital ear malformations has been developed over the past several years (1). Despite the undoubted progress in the treatment of congenital defects there are various numerous procedures which include the patient´s age and indications for surgical reconstructive technique. For the surgeon, congenital malformations are very challenging, and requiring high commitment. Parents´ pressure plays a significant role here, often stemming from the sense of guilt towards their handicapped child. Achievements in medical sciences offer new possibilities for the professional environment, and promise hope for parents looking for information on the treatment of congenital malformations.
External, middle and internal malformations of the ear are rather rare and various authors estimate them to range from 1 in 6 000 to 1 in 30 000 births. In some closed populations, such as the Navajo Indians, the prevalence reaches even 1:1 200 (2; 3; 4; 5). The aetiology of the malformations is still unknown. They usually accompany other defects such as Treacher Collins´ syndrome, branchiootorenal syndrome or Goldenhar´s syndrome (6). They are also accompanied by other defects, especially those of the heart and arterial vessels, kidneys, facial skeleton, nasal cavity or sinuses (7). They are often related to various disorders occurring in the fetal life, e.g., intrauterine infections, ischaemia or exposure to toxins (8). There are several classifications of ear malformations depending on their severity.
One of the most popular classifications was developed by Marx and Altman (9). They categorized aural ear malformations into three groups. The first degree includes deformity of the pinna, with easy to identify details of the ear structure, with the ear canal present but stenosed. In the second degree the pinna is residual, roller-shaped, with folds at both ends, and the ear canal is absent. In the third degree, the pinna is residual (only the lobe is present) and the ear canal is absent. The abnormalities coexist with a variable severity of malformations of the middle and inner ears. Tanzer (10, 11) categorized ear malformations into 5 groups: 1st degree (anotia) – absence of the pinna and auditory canal; 2nd degree (microtia, or a complete hypoplasia) - atresia of the pinna, severe deformity of the pinna usually followed by the absence of the auditory canal; 3rd degree (hypoplasia of the middle third of the auricle) - the auditory canal is usually present; 4th degree (hypoplasia of the superior third of the auricle) – the external auditory canal is formed; 5th degree (a prominent ear) - the ear is formed with a protruding concha.
It is difficult to choose the right option of treatment since it requires a detailed assessment of anatomical and functional results that might be obtained. They should meet the patients´ and their parents´ expectations. Sometimes, however, the result may be unsatisfactory (12). Complications may appear and are unpredictable and frequent, e.g., facial nerve palsy, sensorineural hearing loss, cicatrisation and stenosis of the new auditory canal, perforation of the tympanic membrane (8).
The typical procedure developed and employed in the management of congenital ear malformations at our Institute refers to achieving final auditory results (13, 14) which also include functional and aesthetic effects. In terms of the functional results, aiming at good auditory effects, the procedure includes reconstruction of the external auditory canal and middle ear with reconstruction of the conducting apparatus, providing that the CT examination indicates such a possibility. In the external ear malformations, accompanied by significant middle ear defects, only the pinna is reconstructed whereas hearing is improved by bone-anchored hearing aids (BAHA) using bone conductive abilities.
In terms of the aesthetic aspect in unilateral microtia, with no evidence of previous surgical interventions, it is possible to use a silicone prosthesis of the concha, providing that the patient approves of it. The prosthesis is attached with titanium anchors placed in the bone. This solution is usually offered in the case of adult patients.
The most important condition in patient qualification to undergo the auditory canal and middle ear reconstruction is a good prognosis of hearing improvement; postoperative hearing assessment may indicate that it is possible to obtain over 30 dB HL thresholds for air conduction. Preservation of the external auditory canal is significant; however, this condition is desirable but not necessary. Another condition to be considered, includes a minor deformity of the middle ear, which allows the surgeon to reconstruct the ossicular chain; equally important is the absence of anatomical abnormalities in the tympanic cavity and its surrounding structures. It is also crucial to localize the temporomandibular joint, since there are numerous congenital abnormalities excluding the auditory canal reconstruction. Localization of the facial nerve should also be considered (15, 1).
Material
Thirty one patients who underwent surgical treatment in the years between 1999-2001, were assessed. The cases included only unilateral microtia in which preoperative diagnostic procedures had shown the absence of the external auditory canal. The patients satisfied all the qualification criteria. Radiological examination (CT scan) revealed the presence of the tympanic cavity, auditory ossicles, and the distance between the membranous part of the tympanum and temporomandibular joint. Audiometric examination confirmed the presence of the air-bone gap which provided postoperative hearing improvement at a social communication level. The patients´ age ranged between 6-16 years. Speech development was maintained within the standard range.
The surgical procedure included the following stages:
1. an incision behind the pinna to expose the surface of the mastoid process and the anatomical site where the auditory canal is usually formed in the bony part;
2. removal of the cortex layer of the mastoid process to obtain the patient´s own material for the posterior wall of the canal, and to obtain an access into the air space;
3. localization of the tympanic cavity from the site of the mastoid process following the removal of the pneumatic cells;
4. assessment of the presumed localization of the tympanic membrane, or more frequently, a structure similar in its localization and build;
5. removal of the bone tissue as far as the temporomandibular joint location, but without opening it, and mobilization or amendment of the ossicular chain;
6. formation of the posterior canal wall by grafting the cortex layer of the previously obtained material;
7. obtaining of a large free temporal muscle fascia flap and if possible, a pedunculated fascia flap;
8. covering the canal bone walls with the fascia muscle flap, and covering the site near the ostium with pieces of the skin and perichondrium;
9. formation of the entrance to the canal;
10. fixing the pedunculated pieces of the skin and cartilage with stabilizing sutures, closing the wound behind the pinna, dressing the wound.
Result
The patients were followed up for one to three years; all the surgical wounds had healed by first intention. The surgical dressings were usually removed after 14 days, and a stabilizing drain was subsequently left in place for 2-3 weeks. Audiometric measurements assessing hearing results were performed at 1, 6 and 12 months after the operation. The present paper assesses only the permanence of the anatomical effects, i.e. maintenance of the lumen of the newly formed canal. The lumen of the canal was obtained in 28 cases (90.3%), and this allowed for efficient penetration and purification. That state was maintained for a year. Three patients developed progressive stenosis of the canal preceded by a growth of granulation tissue, which required reoperation. The surgical procedure consisted of removal of the granulation tissue and scar formed. The second stage of the treatment was very successful: a sufficient width of the canal was obtained, which allowed the surgeons to properly clean and penetrate the tympanic cavity.
It is crucial to maintain a wide lumen of the canal in the first postoperative year, since it will further determine the preservation of the effects obtained. So far 9 patients out of 31 have been followed up for 3 years, and 12 patients, for 2 years. Over this time no significant canal stenosis has been recognized. The results obtained after one year may be presumed as long-term and permanent when the patient group is more numerous. Effective auditory results usually required a subsequent stage of surgical operation, i.e. ossiculoplasty. The procedure could be performed using an approach through the reconstructed external auditory canal after the wounds have healed, which is usually 6-8 months after the reconstructive operation. It should be emphasized that despite detailed preparation and the surgeon´s high qualifications, intraoperative difficulties are likely, e.g., too short a distance to the mandibular joint and an abnormal course of the facial nerve. Similar difficulties have been encountered by many surgeons treating congenital malformations, which has been confirmed by several reports (16).
Conclusions
1. The applied surgical technique of the auditory canal reconstruction provides good results, helps obtain an adequately wide lumen of the canal, and is reproducible in consecutive patients.
2. The technique requires considerable experience in otosurgery, particularly in reconstructive operations. Satisfactory results can be obtained only if indications for the operative treatment are well determined and obeyed. Functional effects may be achieved with the reconstruction of the external auditory canal or with a subsequent surgical operation performed on the ossicular chain, with respect to the actual local conditions.
Piśmiennictwo
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