This article describes the microscopic transcanal technique for stapes surgery, providing step-by-step surgical instructions for familiarizing surgeons with this approach.
The microscopic transcanal (aka transmeatal) surgical approach was first described in the 60s, offering a minimally invasive means of reaching the external auditory canal, the middle ear, and epitympanon. Such an approach avoids a retroauricular or endaural skin incision; however, working through a narrow space needs angled microsurgical instruments and specific training in otologic surgery. The transcanal approach restricts the working space; however, it offers a binocular microscopic vision into the middle ear without extended skin incisions and thus, reducing post-operative pain and bleeding. In addition, this minimally invasive approach avoids scar tissue complications, hypoesthesia of the auricle, and potential protrusion of the pinna. Despite its numerous advantages, this method is still not routinely performed by otologic surgeons. Since this minimally invasive technique is more challenging, there is a need for extensive training in order for it to be widely adopted by otologic surgeons. This article provides step-by-step surgical instructions for stapes surgery and reports possible indications, pitfalls, and limitations using this microscopic transcanal technique.
The advent of a binocular operating microscope in otologic surgery in 19511 paved the way for a less invasive microscopic transcanal approach. Alternatives were endaural incisions or retroauricular approaches, which are more invasive. The first transcanal stapes surgery was described by Rosen already in 19522,3, but at that time, the stapes was mobilized and not removed. In 1956, Shea revolutionized stapes surgery with the use of the first Teflon prosthesis4. The transcanal approach proved suitably adapted to this technique since it provided good 3D visualization of the posterior part of the ear canal, tympanic membrane, and middle ear. The indication for a transcanal microscopic method has widened over time, covering a large number of surgical otologic interventions: Tympanotomy5, tympanoplasty6,7,8, ossiculoplasty9, antrotomy10, cholesteatoma11,12,13, glomus tympanicum14, labyrinthectomy15, neurectomy16,17, intrameatal acoustic neuroma by transpromontory approach18,19,20 or even cochlea implantation21.
This challenging approach requires the use of specialized instrumentation for transcanal surgery (initially described in the 60s)22 and specific surgical training. It restricts working space but does, however, offer a binocular microscopic vision into the middle ear without the need for an extended skin incision and thus, reduces post-operative pain and bleeding. In addition, this minimally invasive approach avoids scar tissue complications, hypoesthesia of the auricle, and protrusion of the pinna. In this article, we provide step-by-step surgical instructions for stapes surgery and report possible indications, pitfalls, and limitations using this microscopic transcanal technique.
The local review board of the Bern University (Kantonale Ethikkomission Bern) approved the present study, a formal informed consent was not required for this type of retrospective study.
1. Indications
2. Preparation
3. Local anesthesia
4. Tympanomeatal flap and speculum holder
5. Middle ear dissection
6. Stapes suprastructure removal
7. Footplate perforation
8. Stapes prosthesis insertion
9. Wound closure/dressing
We present here a retrospective cross-sectional analysis (01/2018 to 05/2021) from 66 patients (37 males, 29 females) aged 9-68 years (mean 46.3y, SD ±13.4y), who underwent stapes surgery (48 standard surgeries, 18 revisions, Table 1 and Table 2). All patients were operated by the same surgeon (GM). The instruments were bent and black (Figure 3). The mean speculum size was 6.1 mm (range 5-8 mm, n = 51, Figure 2) which allowed an adequate visualization of the operating field. Only 1 out 66 cases needed a retroauricular incision (9 years old child with a canal diameter <5 mm). A posterior canaloplasty was necessary for 37 of 66 patients. Figure 2 illustrate how to hold the bent instruments with the first three fingertips while stabilizing the hand on the speculum or head of the patient with the remaining two fingers. A speculum holder consists of a mobile extension mounted on the operation table (Figure 4). Light exposure is limited and needs to be adjusted by the position of the microscope and the angled instruments (Figure 5). The ergonometric position of the sitting surgeon and optimized angle of the hands (Figure 6) allow a stable microsurgical performance. Fifty-eight patients received a Richards' piston prosthesis, one patient a Matrix Slim Line KURZ prosthesis, and five patients a malleo-vestibulo-pexy (MVP) prosthesis (ball joint prosthesis). The mean size of the prosthesis was 4.4 mm (range 4-5 mm, SD ± 0.2 mm), mean diameter was 0.46 mm (range 0.4-0.6 mm, SD ± 0.08 mm, Table 1). The prosthesis was additionally fixed with otologic cement in 33 of 66 cases. The Chorda tympani was preserved in 55 out of 65 cases.
Figure 1: Positioning of the patient. (A) The operation table at the lowest position tilted in the reverse Trendelenburg position. (B) The head/body rotation in a side-lying position towards the healthy ear. Please click here to view a larger version of this figure.
Figure 2: How to hold the instruments. The instruments must be held like a pencil; the ring finger should be supported at the edge of the speculum. Please click here to view a larger version of this figure.
Figure 3: Bent instruments for transcanal microscopic approach. The figure illustrates bent instruments such as a hook, a suction, or an ear speculum (from left to right). Please click here to view a larger version of this figure.
Figure 4: Ear speculum holder. The figure illustrates the design of the speculum holder. Please click here to view a larger version of this figure.
Figure 5: Surgical field exposure. The exposure of the surgical field can be influenced by 1) the angle of the microscope light, 2) the angle of the introduced instrument, and 3) the angle of the ear canal/head position. Please click here to view a larger version of this figure.
Figure 6: Positioning of the hands. The wrist of the surgeon should be in (A) neutral position and (B) not extended. Please click here to view a larger version of this figure.
Table 1: Summary of the study. The table summarizes the patient and operation characteristics Please click here to download this Table.
Table 2: Patient and operation characteristics. The table shows individual patient details and operation characteristics. Please click here to download this Table.
The current article provides detailed insider information about the transcanal microscopic approach for stapes surgery. We could demonstrate that microsurgery is feasible using a key-hole technique avoiding a retroauricular or endaural incision in the majority of cases.
Some prerequisites, however, have to be met for achieving a successful surgery. The dissectors should be curved. The knives, hooks, and the needle are angled (Figure 1) to improve the visualization and light conditions in such a narrow space22. In addition, instruments should be black-colored, avoiding any microscopic light reflections. Patient positioning is crucial for the transcanal approach since the ear canal is curved, and the light beam of the microscope must be fully aligned with the longitudinal axis of the canal (Figure 2). In addition, it is crucial to hold the instruments correctly (Figure 3) and to keep a suitable ergonomic posture of the hands (Figure 5) for a successful transcanal surgery.
A speculum holder, as shown in Figure 3, allows a two-handed technique and a straight access route to the tympanic membrane/middle ear. The speculum might additionally serve as an instrument guide. Finally, the angle of the fingers/instruments and the angle of the microscope light should be adjusted and optimized. In view of all these parameters, extensive training of transcanal otologic surgery is needed to improve surgical performance.
Alternative approaches include the endaural and retroauricular incision or the endoscopic transcanal approach. The retroauricular incision is advised for inaccessible anterior perforations of the tympanic membrane or subtotal perforations. Such cases, however, might still be accessible through endoscopic approach23, provided that the ear canal diameter is large enough (>5 mm). The retroauricular approach remains the gold standard if there is a need to open the mastoid cavity. For combined cholesteatoma surgeries (transmeatal and retroauricular transmastoidal approach), we recommend the inside-out technique, which was first described by Roth and Häusler11. This technique suggests as a first step a transcanal access to the middle ear identifying all anatomical structures following the extension of the disease (cholesteatoma) by epitympanectomy. As a second step, a retroauricular incision might follow in cases where transmastoidal access is indicated based on the extension of the cholesteatoma. There is a considerable advantage of this two-step approach since there is a non-negligible proportion of patients who will not need a retroauricular incision (second step) based on a limited extension of the disease.
The transcanal endoscopic approach uses the same route of access and is also limited to an ear canal diameter of >5 mm. Similarly, this approach is minimal-invasive and offers a closer wide-angle view of anatomical structures. In addition, an endoscopic approach offers an angled view of 45° or 70°, which is valuable for the removal of cholesteatomas in the retrotympanum24, the attic region25 or for anterior perforations23. In cholesteatoma surgery, similarly to the above-mentioned inside-out technique, a transcanal endoscopic cholesteatoma removal is performed, followed by clearance of the disease from the mastoid as necessary. In this context, novel exclusive endoscopic techniques were recently described using a constant suction bone-drilling technique26. Endoscopic surgery, however, is a one-handed technique and challenging in inflamed conditions with associated bleeding. Therefore, the management of bleeding plays a key role in the endoscopic approach to the middle ear27. In addition, endoscopy provides a limited depth of field since it does not offer a binocular view. New 3D endoscopes might improve the depth of field28; however, such endoscopes have a larger diameter of 4 mm.
Compared to the retroauricular approach, the microscopic transcanal approach is minimal-invasive and has several advantages such as avoidance of retroauricular pain, scar tissue complications, hypoesthesia of the auricle, and protrusion of the ear.
The transcanal approach also has limitations. The main limitation is the diameter of the ear canal, which should be at least 5 mm. Any disease without direct or with limited access through the meatus is not suitable for a transcanal approach alone. The approach can be extended by using an endoscope or a combined transmastoidal access.
The transcanal/transmeatal microscopic approach has been a proven technique for more than 70 years; however, this method is still not routinely performed by otologists despite the advantages of this minimally invasive approach. Since the performance of this minimally invasive technique is more difficult and challenging, there is a need for extensive training in order to promote its use by otologic surgeons. This illustrative teaching video offers one additional tool to familiarize otologists with this surgical technique.
G.M. is supported by the Swiss National Science Foundation #320030_173081.
Name | Company | Catalog Number | Comments |
Adrenalin | Sintetica | ||
Belucci microscissors | Olympus (former Richards) | 8178100FX | |
Betadine solution (Povidon iodine) | Mundipharma Medical Company | ||
Carbostesin | Sintetica | Bupivacain 2.5 mg/mL | |
Cup forceps | Olympus (former Richards) | ||
Curette | Olympus (former Richards) | 13-0147 | |
Curved suction tubes | Spiggle & Theis | 302007NV und6066500100 | |
Drill | Bienair | 2 mm rough diamond drill | |
FOX laser | A.R.C. Laser GmbH | ||
Gelfoam (absorbable gelatine compressed sponge) | Pfizer Injectables | GS-010DP | absorbable gelatin sponge |
Gloves | Sempermed | Appropriate size | |
Hooks | Olympus (former Richards) |  13-0201, 13-0202, 13-0204, 13-0206 | 0.3–0.6 mm |
Hydrocortison/neomycin/polymyxin otic /Cortisporin Otic Solution | Pfizer | ||
Needle | Olympus (former Richards) | 13-0207 | 27 G |
Operating Microscope | Leica | E 114637 | |
Otologic dissectors | Olympus (former Richards) | ||
Ribbon gauze | |||
Round knifes | Olympus (former Richards) | 13-0211 13-0212 | |
Silk dressing | Otosilk | ||
Speculum | Olympus (former Richards) | OK 082R | |
Surgical Mask | Halyard | 48247 | |
Water to rinse | Ringer |
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