|Year : 2021 | Volume
| Issue : 3 | Page : 153-157
Canalplasty in tympanoplasty – Functional and surgical outcome: A retrospective study
Ravneet Ravinder Verma1, Ravinder Verma2
1 Department of ENT, Head and Neck Surgery, Government Medical College, Chandigarh, India
2 Verma Hospital and Research Centre, Jalandhar, Punjab, India
|Date of Submission||23-Aug-2020|
|Date of Acceptance||28-Jun-2021|
|Date of Web Publication||16-Dec-2021|
Dr. Ravinder Verma
Verma Hospital and Research Centre, Jalandhar - 144 001, Punjab
Source of Support: None, Conflict of Interest: None
Background: During repair of central perforations of tympanic membrane, annulus should be visible in a single view. It helps in better placement of graft. To attain this, the bony canal is enlarged. Materials and Methods: Eighty patients with dry central perforation were selected during the period 2010–2020. Sixty patients with dry central perforation underwent tympanoplasty Type 1 with canalplasty and twenty patients were subjected to tympanoplasty Type 1 only. The method, operative procedure, and words of wisdom to give good results and prevent complications are described. Results: Patients with canalplasty had better postoperative results, and the success rate is improved as compared to only myringoplasty. The primary outcome measure of canalplasty with tympanoplasty procedure is complete re-epithelization and provision of a dry ear in 95%, whereas the final outcome without canalplasty was 90%. Conclusion: The aim of the canalplasty is to create a wide, patent, and physiological bony ear canal. Canalplasty helps to have better visualization, better postoperative care, better exposure for ossiculoplasty, time gain during graft placement, prevent lateralization, and promotes healing. It does improve the surgical outcome in tympanoplasty Type I.
Keywords: Annulus, canalplasty, central dry perforation, myringoplasty, ossiculoplasty, tympanoplasty
|How to cite this article:|
Verma RR, Verma R. Canalplasty in tympanoplasty – Functional and surgical outcome: A retrospective study. Indian J Otol 2021;27:153-7
| Introduction|| |
Tympanoplasty is the repair of middle ear complex includes tympanic membrane grafting with or without reconstruction of the ossicular chain. The purpose of myringoplasty is restoration of anatomical and functional characteristics of the membrane with the closure of the defect, adequate and stable well-ventilated middle ear and production of acoustic characters similar to normal tympanic membrane. When tympanic membrane and annulus cannot be visualized intraoperatively, particularly in anterior or subtotal perforation, canalplasty should be performed. Complete exposure will avoid the compromised surgical results. Canalplasty is widening of the bony external auditory canal (EAC) to visualize the entire tympanic annulus in a single view and create disease-free, self-cleaning canal. It may be complete circumferential, partial or segmental enlargement of bony EAC. It is completed by removing the bony overhang of the canal bulges. Canalplasty may be a procedure in itself as for congenital or acquired atresia stenosis of EAC or can be a part of other procedures such as tympanoplasty or tympanotomy. The usual indications of canalpalsty include exostoses, stenosing or atresia of EAC, and widening for surgical access. A retrospective study of eighty patients undergoing tympanoplasty with canalplasty is presented.
| Materials and Methods|| |
Eighty patients undergoing tympanoplasty procedures for chronic suppurative otitis media with central perforation with or without conductive hearing loss were selected for this study. Patients in the age group of 15–60 years [Table 1] with dry central perforation, mild-to-moderate conductive hearing loss [Table 2], and failed tympanoplasty were included in this study. Exclusion criteria were active discharge, granulation tissue, cholesteatoma or polyp in the ear, sensorineural hearing loss, and myringosclerosis or tympanosclerosis. Patients who were immune compromised and suffering from cardiac problem or bleeding disorders were also excluded from this study. All cases were operated for myringoplasty and/or middle ear inspection with or without reconstruction of ossicular chain.
Preoperative assessment included otomicroscopy to note the size and site of the perforation. The size and site of perforation determined the surgical approach. The status of the middle ear mucosa (normal or granular/polypoidal), Eustachian tube More Details patency by Valsalva or tympanometry, position of handle of the malleus (medialized or normal), and the status of the contralateral ear were noted. Pure-tone audiometry was done in all patients preceding the surgery. Computed tomography scan petro-temporal complex for the middle ear aeration, pneumatization of mastoid, hidden cholesteatoma, and the position of important structures like facial nerve in suspected cases were done.
Surgical techniques include end aural or postural approach or combination of both. Most of the patients were operated under local anesthesia. 2% Xylocaine with 1:100,000 adrenaline is injected at the expected sites of incision and external ear canal wall. Anterior canal wall, conchal bowl, and crus of helix are also injected. A postaural incision behind the crease is given, and a periosteal flap is created. The EAC is opened at the level of the transition between the bony and cartilaginous EACs from 10 to 6 o'clock on the right side and 2–6 o'clock on the left side. Two vertical incisions at both ends and the posterior canal wall flap are raised. With conical burr, the posterior canal wall bulge is removed. Another incision is given from 6 to 2 o'clock on the anterior canal wall in the right ear and 6–10 o'clock on the left side at a medial level than the posterior incision. Another vertical incision at 2 o'clock on the right side and 10 o'clock on the left side from the annulus is given. Anterior flap is elevated lateral to medial, along the annulus. Flaps are folded medially into the middle ear cavity. Inferior bony canal is removed and followed by anteroinferior bony canal. Laterally based flap is elevated anterosuperiorly. Bony bulge in the anterosuperior part is removed with cutting burr. The middle part of the anterior bony canal is removed with diamond burr to avoid injury to temporomandibular (TM) joint. The skin and mucosa in the superior part is elevated along the tympanic membrane remnant and flaps raised all around. The whole flap is attached superiorly in the petrosquamous suture area for vascularity from 2 to 10 o'clock. The osseous auditory canal wall is remodeled in such a way that the whole of the annulus is visible in one frame. The continuity and mobility of ossicular chain is checked. All the corners and hidden areas of the middle ear cavity are examined. Handle of malleus is de-epithelized. Ossiculoplasty was done wherever required [Figure 1]. Temporalis fascia graft is inserted under the handle of malleus in all fresh cases and lateral to the handle in revision cases and laid on the bare bone all around. The tympanic membrane remnants and canal skin flaps are reposed back over the graft on all sides leaving no space between the graft and the flaps [Figure 2] and [Figure 3]. Canal packed with medicated gel foam and postaural wound stitched in layers. In those done under general anesthesia, nitrous oxide is discontinued before the placement of graft. In some cases, the anterior flap is elevated and folded laterally in the cartilaginous portion to avoid injury to the skin.
|Figure 2: Diagrammatic representation of steps of canalplasty and tympanoplasty. (a) Incision; (b) Flap elevation; (c) Bony overhang removed; (d) Complete Tympanic membrane visualized (e) Flap repositioned|
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|Figure 3: Different steps of canalplasty. (a) Anterior and posterior bony overhangs. (b) Anterior canal wall skin incision. (c) Removal of anterior bony overhang. (d) Exposure of anterior annulus. (e) Checking ossicular chain. (f) Completion with graft and skin over bare bone|
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| Results|| |
In our series, in 20 cases, only myringoplasty was carried out, and the success rate has been 85%. In all those cases where canalplasty was done as an associated procedure, the overall success rates jumped to 95% [Table 3]. This increment in the success rate is quite encouraging. There was an average of 17.33 dB gain in all cases [Table 4]. The complication rate in our series has been 20% [Table 5]. These complications are minor and did not need a revision or left no residual abnormality. The rate of complication depends on various factors like revision surgery for failed myringoplasty.
| Discussion|| |
Before sound waves reach the tympanic membrane, they are modified through reflection and damping by the outer shape of the body, the auricle, and the auditory canal. The auricle and the auditory canal form a funnel with closed other ends with tympanic membrane. The auditory canal and auricle have the greatest influence on the resonance of the outer ear. The ear canal plays a very important role in modulation of the sound. The sharp anterior tympanomeatal angle can significantly alter volume of the ear canal and the width of the canal inlet, which affected 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 2800–3000 Hz, depending on the length and diameter of canal. In principle, the bigger the entrance of the external auditory meatus, the higher the resonance frequency, and the greater the volume of the cavity, the lower the resonance frequency. A loss of 10 dB in acoustic pressure amplification in the frequency range between 3 and 4 kHz is associated with the volume expansion. The wavelengths of the frequencies are equal to four times the canal length. When the bony EAC is remodeled surgically, resonance acoustics also change. The creation of wide bony EAC was shown to decrease the resonant frequency substantially and increase the peak amplitude significantly. A perforation of the tympanic membrane has practically no effect on this resonance.
Tympanometric volume is a good indicator of Eustachian tube function and ventilation of the middle ear in perforation. Normal volume of ear canal is 1.5–2.0 ml. In perforation of the tympanic membrane, the ear canal volume measurement should be high because the instrument will measure the volume of the entire middle ear (4–5 ml in adults). If the volume is less than this (e.g., 2.5-3 ml), then ventilation of the middle ear cleft and mastoid must be poor.
The primary outcome measure of canalplasty with tympanoplasty procedure is complete re-epithelization and provision of a dry ear in 95% of cases. This figure of successful graft uptake and dry ear is encouraging. We can definitely conclude that canalplasty is a useful procedure as far as the operative management of the central perforation.
One of the essentials while performing tympanoplasty is complete visualization of the tympanic membrane and the annulus. The usual problem during tympanoplasty surgery is blockage of the view anterior or posterior tympanic membrane due to bony overhangs. Canalplasty provides better visualization and increased assess which helps in evaluation of ossicles, secure graft placement, time gain during graft placement, prevents lateralization, and promotes healing along with better post-operative care and easier follow-up examinations.
Canalplasty prevents accumulation of squamous debris and has been proposed as an adjunct or alternative to tympanoplasty for the treatment of tympanic membrane atelectasis and early cholesteatoma. Canalplasty helps in de-epithelization of the tympanic membrane and placement of graft in overlay technique of tympanoplasty and thus prevents cholesteatoma pearls later on. The goal of the canalplasty is creation of a widely patent and physiologically intact canal wall. Both the bony and cartilaginous portions must be addressed surgically. Care should be taken to preserve the normal skin and adnexa for lining the canal, but if this is not adequate, skin grafts should be used to prevent healing by secondary intent.
Tympanoplasty and canalplasty can be done via different approaches, i.e. transcanal, endaural, or postaural or a combination of all. Postaural approach provides better exposure and easy-to-harvest temporalis fascia graft and gives better results. The endaural and transcanal approaches are less invasive, and healing is faster and less time-consuming. Endoscopic approach has advantage over others in better visibility and less morbidity.
It is advisable to inject the anesthetic agent slowly with needle in contact with bone and avoid a bleb formation. Bleb formation may lead to more bleeding. The canal skin incision should be given either just lateral to the bony hump or about 6–7 mm away from the annulus circumferentially in a jagged manner to prevent restenosis. The skin of the EAC is elevated medially up to the level of annulus and sometimes laterally.
Normal bony ear canal is lined by keratinizing squamous epithelium with migratory characteristics. It is unique in the sense that it is adherent to the periosteum of bony canal and it lacks subcutaneous tissue. The skin must be protected from the injury by burr or intervention and covered with silastic sheet or aluminum foil due to the special character of the skin of the bony canal. Widening of bony canal may lead to shortening of the skin to leave the bone exposed. This uncovered bone is a potential source of infection. The solution to this problem is preservation and protection of skin flap, covering the denuded bone with split-thickness/full-thickness skin graft taken from the inner arm or postaural region, fascia, or local pedunculated skin graft leading to faster healing.
Different flaps have been described in the literature. For anterior bony overhangs, lateral- or medial-based flaps have been described. Bone is always removed from lateral to medial under direct vision. While drilling the anterior canal wall overhang, initially bone should be removed superiorly followed by inferior and then the central part around the TM joint area. The lateral most part of the anterior canal wall near the zygoma and the medial most part near the annulus are hard bone and can be removed with cutting burrs. The middle portion of the anterior canal wall is softer and hence diamond burr is to be used. Moreover, the TM joint area should be manipulated carefully so as not to injure the joint. When the bone adjacent to TM joint is maximally thinned, note the change of color to pinkish gray or bluish of anterior canal wall in the TM joint area. If the TM joint is exposed or injured, it can be covered with skin. All angulations must be removed to avoid the collection of debris in postoperative period.
Blood supply of EAC and tympanic membrane is very important for otologists for giving incisions and the healing pattern of the flaps. Vascular strip is a skin of EAC between tympanomastoid suture and tympanosquamous suture present at posterosuperior portion of EAC. It is thick in nature and supposed to have more vascularity, so all the blood supply to EAC and TM comes from superior part through vascular strip.
Flaps should be raised in such a way that blood supply of flap is not injured. Most of the flaps described are either superiorly based as they contain the best blood flow for the medial portion of the tympanic membrane. The medial portion of the EAC and lateral surface of the tympanic membrane is supplied by deep auricular artery which is a branch of maxillary artery that enters EAC through floor and divides into posterior and anterior marginal branches along tympanic sulcus up to attic. Since this vessel enters through the floor of the external bony meatus, hence inferiorly based flaps survive better. All flaps in the end of the procedure must be repositioned properly and hemostasis secured.
Proper burrs, adequate vasoconstriction, and protection of skin flap are the basic requirements for a proper canalplasty. Anterior and posterior walls up to 5 mm can be removed and floor up to 13 mm can be removed. The secret of successful canalplasty is preservation of the delicate canal skin. It should be covered with gauze, cotton ball, and aluminum foil or silastic sheath. Henceforth, it is advised to widen the canal in parts to prevent the complications. All bony fragments and bone dust must be meticulously removed to avoid further tissue reaction. The end result of canalplasty must be visualization of the entire tympanic annulus in one position of the microscope (Fisch's dictum).
Complications of canalplasty procedure are not frequent if proper care is taken. Partial, transient, or delayed facial palsy can occur, probably relating to thermal injury transmitted from the burr. Injury to TM joint can occur and may cause herniation of joint into external canal. The other complications of canalplasty include tearing of the skin; opening into the mastoid air cells; damaging the tympanic membrane, ossicles, and skin flaps; or infections such as perichondritis, bleeding, and hematoma formation. The long-term complication of canalplasty is restenosis of EAC. To avoid stenosis, the incision on the skin should be given in a jagged manner. The sealing of any inadvertently opened mastoid air cells helps to avoid the late complication of canal cholesteatoma. Canalplasty via the postauricular approach minimizes complications.
Correlate the size of the perforation with the audiogram, particularly the air-bone gap. Lerut et al. investigated that there was a strong correlation between air-bone gap and increasing perforation size; however, the location (interior/posterior) had no impact on hearing. The greatest changes in air-bone gap were at 0.5 and 4 kHz and the smallest changes at 2 kHz. The audiograms thus revealed a consistent “v-” shaped pattern with the turning point at 2 kHz. This can be explained by the fact that 2 kHz is the resonance frequency of the middle air; thus, hearing is better preserved at this frequency. The clinical significance is that one can predict the expected air-bone gap by looking at the size of the perforation. If the audiogram does not correspond with the expected findings, then additional middle ear pathology must be expected. If the air-bone gap is > 30 Db, then an ossiculoplasty may be required.
Does canalplasty improve hearing? A question still difficult to answer. Since we carried out the study in perforated eardrums with or without ossicular chain interruption, it is very difficult to say that canalplasty has a role in improving the hearing. Many studies reported an improvement in hearing. In our study, there was a definite improvement in hearing, as shown in [Table 4]. However, there were different types of operative procedures carried out, thus rendering a viable comparison difficult. It is needed to be studied how much hearing gain occurs with canalplasty. However, there was no worsening of hearing level and no sensorineural hearing loss observed in our cases. It is, therefore, not possible to compare the hearing results with those authors who claim reduced air-bone gap. Comparing the various surgical techniques is difficult. The outcome of these techniques is significantly influenced by the experience of operating surgeon, the degree of the disease, and patient comorbidity.
| Conclusion|| |
The primary outcome measure of canalplasty with tympanoplasty procedure is complete re-epithelization and provision of a dry ear in 95%. The success rate in cases without canalplasty was 85%. This figure of successful graft uptake and dry ear is encouraging. In all cases of tympanoplasty or myringoplasty, the tympanic annulus must be visualized, especially in anterior and subtotal perforations. To achieve this goal, canalplasty is considered an integral part of tympanoplasty or myringoplasty. At the same time, canal skin must be preserved. To attain this, canal should be widened in parts. We can definitely conclude that canalplasty is a useful procedure as far as the operative management of the central perforation.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]