|Year : 2013 | Volume
| Issue : 4 | Page : 159-163
Role of canaloplasty
Editor-in-chief IJO CEO; Indian Institute of Ear Disease
|Date of Web Publication||7-Jan-2014|
M K Taneja
Editor-in-chief IJO CEO; Indian Institute of Ear Disease
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Taneja M K. Role of canaloplasty. Indian J Otol 2013;19:159-63
| Introduction|| |
The surgical procedure on the ear in principle can affect its acoustic function, including surgery of the external ear. The ear canal plays a major role in modulating the sound that is incident upon the tympanic membrane. The sharp anterior tympanomeatal angle, where the oblique ear canal meets the tympanic membrane, can significantly alter the sound pressure levels and impedances at various sites in front of the drum, especially at high frequencies.
More important factors in sound conduction are the volume of the ear canal and the width of the canal inlet, which affect the resonance of the canal. A resonance-induced amplification of sound pressure of up to 20 dB occurs in the normal ear canal at frequencies of 2,800-3,000 Hz, depending on the length and diameter of the canal. The wavelengths of these frequencies are equal to four times the canal length.  A perforation of the tympanic membrane has practically no effect on this resonance.
Increasing the canal volume, as by the surgical creation of a radical mastoid cavity, shifts the resonance to significantly lower frequencies.  The nature of the cavity surface (smooth or angular) led to a relatively small change in the resonance amplitude (about 6 dB), but did not alter the resonance frequency. 
The width of the canal inlet is also a major acoustic factor in a radical cavity, which functions as a Helmholtz resonator. Increasing the surface area of the inlet increases the resonance frequency, as was demonstrated in a petrous model.  Certain surgical measures that are desirable to ensure optimum aeration (cavity reduction and enlarging the inlet) can also help match the acoustics of sound reception in a radical cavity to that of the normal ear canal. 
| Materials and Methods|| |
We conducted a prospective study at the Otorhinolaryngology outpatient department of Indian Institute of Ear Diseases (Cochlear Implant Center), Muzaffarnagar (UP), India, over a period of 10 years from 2003 to 2013.
A total of 82 patients having external auditory canal stenosis (partial or total) were selected for surgery. Written informed consent was obtained from each study participant. In cases of subject between 10 and 18 years of age, consent was provided by the legal guardian while they themselves provided assent.
After routine hematological and radiological evaluation, canaloplasty was performed. Statistical analysis was performed on the intent-to-treat (ITT) population.
| Results|| |
A total of 82 surgeries were performed out of which majority was in the age group of 15-25 years (44) [Table 1]. The commonest etiological factor in our study was inferior canal wall hump [Figure 1] leading to myringitis (47) [Table 2] for which transcanal anteroinferior wall canaloplasty was performed with cure rate of 89.3% (42/47) [Table 3] and [Figure 8].
| Discussion|| |
Canaloplasty is a procedure to widen the external auditory canal usually posteriorly and superiorly by removing all overhangs lateral to tympanic annulus as to become an inverted cone, while meatoplasty is widening of the auditory meatus for aeration to mastoid cavity. It is performed in exostosis resulting in cholesteatoma of external auditory canal and retention of cerumen. Bone is removed from posterior and superior bony auditory canal along with conchal cartilage.
Canaloplasty is a part of repair in congenital aural atresia, or otoplasty with the widening of surgical horizon of otolaryngologist to head and neck surgeon and plastic surgeon.
The secret of success of procedure is in preservation of canal skin and to do so, canal is widened in parts.
There are various routes: Postaural, endaural, or transcanal. Author prefers an endaural approach.
The incision for canaloplasty is given from 6 to 12 O'clock position from the outer or lateral margin of exostosis or bony hump and medially unto annulus margin [Figure 3],[Figure 4] and [Figure 5]. Posterior canal wall skin is elevated as in tympanotomy/stapedectomy, taking care of canal skin; every bit of canal skin should be preserved [Figure 6]. Suction should be used only on bony wall or on a perforated circular knife. Rotation of burr should always be away from the elevated flap. In cases of fibrous stenosis/chronic otitis media, we are not bothered to preserve canal skin as canal skin has to be removed due to its mutilation.
|Figure 3: Posterior canal wall vertical incision 2 mm; lateral to annulus, joining horizontal incision|
Click here to view
A ledge of bone is left just lateral to annulus/skin flap which will prevent the flap getting tripped in rotating burr simultaneously silastic sheet/X-ray film/aluminum foil from suture may be placed over the elevated skin flap to protect canal skin.
In cases of fibrotic stenosis where tympanic membrane is thick, lusterless, superficial layer is gently peeled off all around but fibrous middle layer has to be preserved as in onlay myringoplasty.
After widening the posterior canal wall, another incision is given from 12 to 6 O'clock at the anterior canal wall. Canal skin is elevated as of posterior canal wall up to annulus [Figure 3] and [Figure 4]. The canal skin of anterior canal lateral to exostosis is elevated laterally/outward and placed under the anteriorly placed retractor prong.
Drilling on anterior wall is done initially on both superior and inferior part, gradually coming to mid-anterior segment taking care of temporomandibular joint (TMJ) as anterior bony canal wall forms the posterior wall of TMJ. Drilling should always be done away from the skin flap or the tissue surgeon wants to protect. Avoid injury or exposure of TMJ, pinkish gray color is visible through the anterior canal call to visualize the upcoming TMJ.
The ledge of bone all around the annulus is removed and no angle should be left where at the end keratin may accumulate [Figure 7]. The canal skin is reposited; sometimes vertical cuts may be required for better approximation [Figure 8].
Canaloplasty is performed in cases of chronic otitis externa where medical treatment fails to resolve or hearing loss is more than 20 dB. It is preferable to do it with meatoplasty. Canal skin as being infected is always removed and Thiersch skin graft is placed.
Inferior canal wall bulge acts as a trap where secretion gets stagnated, hence once myringitis sets in, it is difficult to get a dry ear. There may be a small anteroinferior perforation with healthy middle ear mucosa. The myringitis may be associated with central perforation [Figure 5]. Simple myringoplasty may lead to failure due to accumulation of secretion resulting in infection of graft; hence, an inferior canal wall canaloplasty is performed. Horizontal incision is given from 9 to 3 O'clock lateral to bulge usually 8.0 mm lateral to annulus [Figure 2], canal skin is elevated [Figure 6] all extra bone is drilled away as usual till complete annulus is visualized [Figure 9]. If a myringoplasty is required, authors prefer to do an inlay procedure raising to the annulus and creating two anterior and posterior flaps by bisecting the tympanomeatal flap at 6 O'clock then after placing the temporal fascia graft all 360° and under the handle of malleus, tympanomeatal flaps (which are attached superiorly from 9 to 3 O'clock) are reposited.
Atresia of external auditory canal
It results from failed or aborted development, usually unilateral and associated with other congenital anomalies of ear resulting in hearing loss. Selection of case is important, one must assess preoperatively how much hearing improvement is anticipated, and if not, bone conduction hearing aid or bone anchored hearing aid (BAHA) may be advised.
Before proceeding to surgery, reassessment of hearing and tuning fork testing is mandatory. There may be total or severe sensorineural hearing loss in other side anatomically normal ear. HRCT scan of bilateral temporal bones must show normal inner ear. An ear suggesting good cochlear function, oval window with stapes and normal course of facial nerve is a good case to operate; facial nerve lying over the oval window is difficult to tackle. Reconstruction of auricle is performed first followed by tympanoplasty or canaloplasty.
Endotracheal anesthesia is given; patient is put in supine position with head turned away from surgeon. Muscle relaxants are usually not given when facial nerve monitoring is to be done.
Standard endaural incision is given as in myringoplasty. The surface marking of epitympanum is below temporal line behind the TMJ. The drilling begins at the attic. Middle fossa dura is skeletonized. Remember skeletonizing means always leaving an egg shell bone over the structure. The atretic plate of bone is drilled away, taking care of ossicles. The drilling proceeds anteromedially avoiding unnecessary opening of mastoid air cells. An effort is made to create wide anterior canal wall, preferably more than two mm anterior to ossicles. While drilling anterior canal wall all precaution must be taken not to expose TMJ, and author prefers doing all work with diamond drill around the ossicles and TMJ. Heat generated by diamond drill is tremendous hence profuse irrigation should be used, always keep the direction of rotation of burr away from vital structures and to prevent injury, suction tip may be placed over the structure you want to save. On completion of skeletonization, bone becomes transparent with underneath structure partially visible and the sound of drilling changes from low pitch to high pitch. An attempt is made to create a 10 mm diameter external auditory canal. Facial nerve is usually displaced anteriorly and laterally in vertical segment hence while drilling in this area surgeon has to be extra cautious and facial nerve monitoring is mandatory. If electro-cautery is must, assistant should palpate the face manually.
Atretic bone is drilled in the end. A gel film or silastic sheet is placed between ossicles and canal wall to prevent refixation. A new tympanic sulcus is created. Skin graft of 0.2 mm partial thickness is procured from medial aspect of upper arm. Skin graft is placed on sofratulle and spread evenly. Graft is cut into multiple pieces along with sofratulle for placement in canal.
Nitrous oxide is withdrawn well in advance as it dissipates in middle ear as bubbles which may dislodge/displace the temporal fascia graft.
Three to four holes are made by drill at the lateral end of newly created canal; 4/0 vicryl suture is passed through them. The skin grafts are anchored to canal by these sutures and canal is further gently packed with sofratulle pack. Endaural incision is closed as usual by interrupted silk sutures. Meatoplasty is usually performed for better results. Wound is checked frequently but not disturbed for minimum 10 days until gross infection is observed. On 10 th -14 th day, all sutures are removed and secretions are gently sucked out. Care of the canal is mandatory for some time. Chemical cautery and dressing with ointment is strongly recommended otherwise restenosis may develop.
Results are explained to attendants in writing both for hearing as well as cosmetically. Results are encouraging cosmetically, but in terms of hearing improvement up to 30 dB hearing gain is expected in 60% cases in experienced hands. If patient or attendants are not convinced thoroughly, BAHA should be advised specifically in bilateral hearing loss cases.
In our study, canaloplasty was performed for various etiologies. Two cases of congenital anotia were operated by endaural approach and 360° canaloplasty was performed along with tympanoplasty, but results were not encouraging. In ten cases, posterosuperior wall canaloplasty with conchal meatoplasty was done through endaural route which was successful in 80% cases. Prolong dressing was required; in no case skin grafting was required. The best in series were patients of inferior canal wall hump with myringitis or central perforation, in these cases transcanal or minimal endaural canaloplasty and/or myringoplasty was done. Success rate was quite encouraging as 89.3% in canaloplasty alone and 91.3% in canaloplasty with myringoplasty.
| Conclusion|| |
If inferior canal wall canaloplasty is performed; myringitis with intact tympanic membrane having inferior canal wall hump heals well with no reoccurrence. Canaloplasty is a key of successful tympanoplasty. In one view annulus all around should be visualized; wide meatoplasty is one of the important step in preventing restenosis. No part of cartilage should be left exposed which may result in perichondritis. Canal skin is gold; hence, every bit of canal skin should be preserved.
| References|| |
|1.||Huttenbrink KB. Biomechanical aspects of middle ear reconstruction. In: Jahnke K, editor. Middle Ear Surgery, Recent Advances and Future Directions. New York: Thieme Publishers; 2010. |
|2.||Kirikal J. The middle ear. The University of Tokyo Press; 1960. |
|3.||Lim DJ. Human tympanic membrane. An ultrastructural observation. Acta Otolaryngol 1970;70:176-86. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
[Table 1], [Table 2], [Table 3]
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