G.M. is supported by the Swiss National Science Foundation #320030_173081.

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
<ol>
	<li>Use the transcanal approach if the diameter of the ear canal is &#8805;5.5 mm. 
	NOTE: The anatomy and shape of the outer ear canal might further limit the working space.</li>
	<li>Assess the canal&#39;s diameter by placing a 5 mm diameter ear speculum. Ensure that the speculum sits comfortably in the canal.</li>
	<li>Do not use the transcanal approach in anterior perforations with a non-visible anterior rim.</li>
	<li>Use the inside-out-technique11 for middle ear pathologies such as cholesteatomas, which reach the epitympanon beyond the semicircular canal.</li>
</ol>
2. Preparation
<ol>
	<li>Positioning of the patient: Place the operating table at the lowest position, tilted in a reverse Trendelenburg position (Figure 1A) with the angle (&#945;) of the headrest at its maximal reclination (without head hanging). 
	NOTE: This position is contraindicated in patients with atlantoaxial instability. Finally, rotate the head towards the contralateral side (&#946;, Figure 1B).</li>
	<li>Instruments: Use bent instruments to keep the working field open. Hold the instruments correctly with the fingers, thus preventing any blocked vision (Figure 2 and Figure 3). 
	NOTE: Black-colored instruments reduce light reflections.</li>
	<li>Disinfection and cleaning of the ear canal: Clean the ear canal thoroughly to avoid any intraoperative infection. Disinfect the canal with diluted Povidone Iodine (2.5%-5% due to toxicity).</li>
</ol>
3. Local anesthesia
<ol>
	<li>Perform local anesthesia in two steps:
	<ol>
		<li>Inject all four quadrants (23 G needle) with Carbostesin 0.25% (50 mg/20 mL) mixed with Adrenalin 1 mg/mL (final concentration 1:200,000 epinephrine).</li>
		<li>Inject within the ear canal using a small bent 27 G needle. Be careful when injecting in the anterior-inferior area to avoid facial paresis.</li>
	</ol>
	</li>
</ol>
4. Tympanomeatal flap and speculum holder
<ol>
	<li>Perform a tympanomeatal flap using a u-shape incision with a sickle or a round knife starting at 6&#39; o clock position (inferio-anterior). Detach the ear canal skin with a Rosen knife until the inferior annulus rim is reached.</li>
	<li>Install the speculum holder (Figure 4).</li>
	<li>Insert the largest possible ear speculum. Make sure that the orientation is correct. 
	NOTE: Letters indicating the size of the speculum should be placed superiorly.</li>
	<li>Complete the tympanomeatal u-shaped flap by cutting the superior-posterior part with the Belucci scissor. Detach the ear canal skin with a Rosen knife until the superior annulus rim is reached.</li>
	<li>This step might cause bleeding.</li>
	<li>Use an absorbable gelatin sponge soaked with adrenaline to stop bleeding.</li>
	<li>Detach the whole flap until the edge of the annulus.</li>
</ol>
5. Middle ear dissection
<ol>
	<li>Make sure that facial nerve monitoring is working before entering the middle ear. 
	NOTE: The patient should have recovered from any neuromuscular block, which can be assessed by neuromuscular monitoring (4 TOF, train of four).</li>
	<li>Enter the middle ear at the posterior-superior part of the annulus since it is easier to detach at this position. 
	&#8203;NOTE: Large cholesteatomas or granulation tissue around the middle ear ossicles might hide any anatomical landmark. In this case, inferio-posterior entering of the middle ear might be advised to find other landmarks (CAVE: jugular bulb).</li>
	<li>Dissect and visualize the anatomical middle ear structures. Visualize the chorda tympani, promontory, incudostapedial joint, stapedial tendon, and the facial nerve (tympanic segment).</li>
	<li>Widen the posterior-superior part of the ear canal with a bone curette or a 2 mm rough diamond drill (low speed) if any of the above structures are not sufficiently exposed. Put an absorbable gelatin sponge in the middle ear to prevent the entrance of bone dust into the middle ear.</li>
</ol>
6. Stapes suprastructure removal
<ol>
	<li>Disconnect the incudostapedial joint with a small 0.3-0.6 mm hook or a sickle knife and make an anterior movement to prevent breaking of the footplate.</li>
	<li>Test the mobility of all the three ossicles by touching each ossicle with a needle to confirm isolated ankylosis of the stapes.</li>
	<li>Use protection glasses or filters integrated into the microscope.</li>
	<li>Dissect the stapedial tendon with the laser (e.g., diode laser, CO2-Laser). Test the strength of the laser during this procedure. Use a FOX laser with 2.5-3 W energy in pulse mode (30-50 ms); however, this value depends on the device and its probe.</li>
	<li>Dissect the posterior crus of stapes near the attachment of the footplate &#177; anterior crus if the footplate is too mobile.</li>
	<li>Remove the stapes suprastructure. Brake the stapes away from the facial nerve towards the promontory if the anterior crus is still intact. Keep the footplate intact. 
	&#8203;NOTE: The footplate should not move while breaking the suprastructure. There is a risk of a longitudinal fracture of the footplate during this procedure.</li>
</ol>
7. Footplate perforation
<ol>
	<li>Use the FOX laser to carbonize/weaken the footplate (2 W, 30 ms pulse mode) by making a rosette pattern.</li>
	<li>Use a perforator microdrill (skeeter 0.6 mm) to perforate the last shell of the footplate in the posterior third section.</li>
	<li>If the footplate is too thick, use a diamond microdrill to thin out the footplate until a blue shimmering structure is visible (also known as blue lining).</li>
	<li>Do not use the suction in the area of the footplate once the footplate is open.</li>
</ol>
8. Stapes prosthesis insertion
<ol>
	<li>Measure the distance between the long process of the incus and the footplate using a measurement instrument with a 4 mm measuring mark. Use a 0.25 mm longer prosthesis than measured.</li>
	<li>Hold the prosthesis hook with a small alligator ear forceps using a predefined angle of orientation (~20&#176;) prior to insertion.</li>
	<li>Crimp the stapes hook on the long process of the incus. 
	NOTE: The front tine of the crimping instrument moves while the back tine remains stable on the incus.</li>
	<li>Check the movement of the prosthesis by moving the malleus handle.</li>
	<li>Avoid the prosthesis from touching the promontory or the facial nerve.</li>
	<li>Consider using otologic cement if there is an interplay between prosthesis and incus process.</li>
	<li>Avoid over-crimping since there is a risk for incus necrosis in the long term.</li>
	<li>Seal the perforated footplate with small water-soaked absorbable gelatin sponge.</li>
</ol>
9. Wound closure/dressing
<ol>
	<li>Reposition the tympanomeatal flap, adapt with silk dressing, and pack with absorbable gelatin sponge soaked with a solution of hydrocortisone 10 mg (1%)/neomycin 3.5 mg/polymyxin B sulfates 10,000 Units.</li>
	<li>Use a 10 cm ribbon gauze soaked with the same solution for ear canal packing.</li>
</ol>

<ol><li>Mudry, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+history+of+the+microscope+for+use+in+ear+surgery%5BTitle%5D)+AND+%22Otology+%26+Neurotology%22%5BJournal%5D)">The history of the microscope for use in ear surgery.</a> Otology & Neurotology. 21 (6), 877-886 (2000).</li>
<li>Rosen, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+development+of+stapes+surgery+after+five+years%3A+Mobilization-Fenestra+Ovalis%5BTitle%5D)+AND+%22AMA+Archives+of+Otolaryngology%22%5BJournal%5D)">The development of stapes surgery after five years: Mobilization-Fenestra Ovalis.</a> AMA Archives of Otolaryngology. 67 (2), 129-141 (1958).</li>
<li>Rosen, S., Bergmant, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Improved+hearing+after+mobilization+of+the+stapes+in+otosclerotic+deafness%5BTitle%5D)+AND+%22The+Journal+of+Laryngology+%26+Otology%22%5BJournal%5D)">Improved hearing after mobilization of the stapes in otosclerotic deafness.</a> The Journal of Laryngology & Otology. 69 (5), 297-308 (1955).</li>
<li>Nazarian, R., McElveen, J. T., Eshraghi, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((History+of+otosclerosis+and+stapes+surgery%5BTitle%5D)+AND+%22Otolaryngologic+Clinics+of+North+America%22%5BJournal%5D)">History of otosclerosis and stapes surgery.</a> Otolaryngologic Clinics of North America. 51 (2), 275-290 (2018).</li>
<li>Jackson, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transmeatal+tympanotomy%5BTitle%5D)+AND+%22South+African+Medical+Journal%22%5BJournal%5D)">Transmeatal tympanotomy.</a> South African Medical Journal. 34, 983-984 (1960).</li>
<li>Austin, D. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcanal+tympanoplasty%5BTitle%5D)+AND+%22Otolaryngologic+Clinics+of+North+America%22%5BJournal%5D)">Transcanal tympanoplasty.</a> Otolaryngologic Clinics of North America. 5 (1), 127-143 (1972).</li>
<li>de Savornin Lohman, E. A. J., Borgstein, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transmeatal+tympanoplasty+of+subtotal+and+anterior+perforations%3A+a+single-institution+experience+including+94+patients%5BTitle%5D)+AND+%22Clinical+Otolaryngology%3A+Official+Journal+of+ENT-+UK%3B+Official+Journal+of+Netherlands+Society+for+Oto-Rhino-Laryngology+%26+Cervico-Facial+Surgery%22%5BJournal%5D)">Transmeatal tympanoplasty of subtotal and anterior perforations: a single-institution experience including 94 patients.</a> Clinical Otolaryngology: Official Journal of ENT- UK; Official Journal of Netherlands Society for Oto-Rhino-Laryngology & Cervico-Facial Surgery. 42 (4), 920-923 (2017).</li>
<li>Seidman, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Anterior+transcanal+tympanoplasty%3A+A+novel+technique+to+repair+anterior+perforations%5BTitle%5D)+AND+%22Otolaryngology-Head+and+Neck+Surgery%3A+Official+Journal+of+American+Academy+of+Otolaryngology-+Head+and+Neck+Surgery%22%5BJournal%5D)">Anterior transcanal tympanoplasty: A novel technique to repair anterior perforations.</a> Otolaryngology-Head and Neck Surgery: Official Journal of American Academy of Otolaryngology- Head and Neck Surgery. 138 (2), 242-245 (2008).</li>
<li>Aslan, A., Tanyeri Toker, G., Ozgur, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcanal+approach+for+Type+2+tympanoplasty+with+incus+interposition+ossiculoplasty%3A+Our+experience+on+134+patients%5BTitle%5D)+AND+%22Clinical+Otolaryngology%22%5BJournal%5D)">Transcanal approach for Type 2 tympanoplasty with incus interposition ossiculoplasty: Our experience on 134 patients.</a> Clinical Otolaryngology. 43 (4), 1135-1139 (2018).</li>
<li>Holt, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcanal+antrotomy%5BTitle%5D)+AND+%22Laryngoscope%22%5BJournal%5D)">Transcanal antrotomy.</a> Laryngoscope. 118 (11), 2036-2039 (2008).</li>
<li>Roth, T. N., Haeusler, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Inside-out+technique+cholesteatoma+surgery%3A+a+retrospective+long-term+analysis+of+604+operated+ears+between+1992+and+2006%5BTitle%5D)+AND+%22Otology+%26+Neurotology%3A+Official+Publication+of+the+American+Otological+Society%2C+American+Neurotology+Socient+%5Band%5D+European+Academy+of+Otology+and+Neurotology%22%5BJournal%5D)">Inside-out technique cholesteatoma surgery: a retrospective long-term analysis of 604 operated ears between 1992 and 2006.</a> Otology & Neurotology: Official Publication of the American Otological Society, American Neurotology Socient [and] European Academy of Otology and Neurotology. 30 (1), 59-63 (2009).</li>
<li>Roth, T. N., Ziglinas, P., Haeusler, R., Caversaccio, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cholesteatoma+surgery+in+children%3A+long-term+results+of+the+inside-out+technique%5BTitle%5D)+AND+%22International+Journal+of+Pediatric+Otorhinolaryngology%22%5BJournal%5D)">Cholesteatoma surgery in children: long-term results of the inside-out technique.</a> International Journal of Pediatric Otorhinolaryngology. 77 (5), 843-846 (2013).</li>
<li>Shah, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Cholesteatoma+surgery%3B+transcanal+approach%5BTitle%5D)+AND+%22Advances+in+Oto-Rhino-Laryngology%22%5BJournal%5D)">Cholesteatoma surgery; transcanal approach.</a> Advances in Oto-Rhino-Laryngology. 29, 216-223 (1983).</li>
<li>Cannon, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Glomus+tympanicum+removal+by+transmeatal+approach%5BTitle%5D)+AND+%22Laryngoscope%22%5BJournal%5D)">Glomus tympanicum removal by transmeatal approach.</a> Laryngoscope. 72, 193-200 (1962).</li>
<li>Gacek, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcanal+labyrinthectomy%5BTitle%5D)+AND+%22Laryngoscope%22%5BJournal%5D)">Transcanal labyrinthectomy.</a> Laryngoscope. 88 (10), 1707-1708 (1978).</li>
<li>Jones, R., Silverstein, H., Smouha, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Long-term+results+of+transmeatal+cochleovestibular+neurectomy%3A+an+analysis+of+100+cases%5BTitle%5D)+AND+%22Otolaryngology-Head+and+Neck+Surgery%3A+Official+Journal+of+American+Academy+of+Otolaryngology-+Head+and+Neck+Surgery%22%5BJournal%5D)">Long-term results of transmeatal cochleovestibular neurectomy: an analysis of 100 cases.</a> Otolaryngology-Head and Neck Surgery: Official Journal of American Academy of Otolaryngology- Head and Neck Surgery. 100 (1), 22-29 (1989).</li>
<li>Kos, M. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcanal+approach+to+the+singular+nerve%5BTitle%5D)+AND+%22Otology+%26+Neurotology%22%5BJournal%5D)">Transcanal approach to the singular nerve.</a> Otology & Neurotology. 27 (4), 542-546 (2006).</li>
<li>Isaacson, B., Tolisano, A. M., Patel, A. R., Barnett, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transcanal+microscopic+transpromontorial+approach+for+vestibular+schwannoma%5BTitle%5D)+AND+%22Journal+of+Neurological+Surgery%2C+Part+B%3A+Skull+Base%22%5BJournal%5D)">Transcanal microscopic transpromontorial approach for vestibular schwannoma.</a> Journal of Neurological Surgery, Part B: Skull Base. 80, 279-280 (2019).</li>
<li>Mazzoni, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Transmeatal+microsurgery+for+intralabyrinthine+and+intrameatal+schwannomas%3A+a+reappraisal%5BTitle%5D)+AND+%22Acta+Otorhinolaryngologica+Italica%22%5BJournal%5D)">Transmeatal microsurgery for intralabyrinthine and intrameatal schwannomas: a reappraisal.</a> Acta Otorhinolaryngologica Italica. 40 (5), 390-395 (2020).</li>
<li>Presutti, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Expanded+transcanal+transpromontorial+approach+to+the+internal+auditory+canal%3A+Pilot+clinical+experience%5BTitle%5D)+AND+%22Laryngoscope%22%5BJournal%5D)">Expanded transcanal transpromontorial approach to the internal auditory canal: Pilot clinical experience.</a> Laryngoscope. 127 (11), 2608-2614 (2017).</li>
<li>Kiratzidis, T., Arnold, W., Iliades, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Veria+operation+updated.+I.+The+trans-canal+wall+cochlear+implantation%5BTitle%5D)+AND+%22ORL%3B+Journal+for+Oto-Rhino-Laryngology+and+its+Related+Specialties%22%5BJournal%5D)">Veria operation updated. I. The trans-canal wall cochlear implantation.</a> ORL; Journal for Oto-Rhino-Laryngology and its Related Specialties. 64 (6), 406-412 (2002).</li>
<li>Dworacek, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Instruments+for+transmeatal+middle+ear+surgery%5BTitle%5D)+AND+%22AMA+Archives+of+Otolaryngology%22%5BJournal%5D)">Instruments for transmeatal middle ear surgery.</a> AMA Archives of Otolaryngology. 70, 510-511 (1959).</li>
<li>Tseng, C. C., Lai, M. T., Wu, C. C., Yuan, S. P., Ding, Y. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Endoscopic+transcanal+myringoplasty+for+anterior+perforations+of+the+tympanic+membrane%5BTitle%5D)+AND+%22JAMA+Otolaryngology-Head+%26+Neck+Surgery%22%5BJournal%5D)">Endoscopic transcanal myringoplasty for anterior perforations of the tympanic membrane.</a> JAMA Otolaryngology-Head & Neck Surgery. 142 (11), 1088-1093 (2016).</li>
<li>Bonali, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Correlation+of+radiologic+versus+endoscopic+visualization+of+the+middle+ear%3A+implications+for+endoscopic+ear+surgery%5BTitle%5D)+AND+%22Otology+%26+Neurotology%22%5BJournal%5D)">Correlation of radiologic versus endoscopic visualization of the middle ear: implications for endoscopic ear surgery.</a> Otology & Neurotology. 41 (9), 1122-1127 (2020).</li>
<li>Presutti, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+impact+of+the+transcanal+endoscopic+approach+and+mastoid+preservation+on+recurrence+of+primary+acquired+attic+cholesteatoma%5BTitle%5D)+AND+%22Otology+%26+Neurotology%22%5BJournal%5D)">The impact of the transcanal endoscopic approach and mastoid preservation on recurrence of primary acquired attic cholesteatoma.</a> Otology & Neurotology. 39 (4), 445-450 (2018).</li>
<li>Gao, Z., Jia, X. H., Yuan, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Endaural+endoscopic+atticoantrotomy+%28retrograde+mastoidectomy%29+using+a+constant+suction+bone-drilling+technique%5BTitle%5D)+AND+%22Journal+of+Visualized+Experiments%3A+JoVE%22%5BJournal%5D)">Endaural endoscopic atticoantrotomy (retrograde mastoidectomy) using a constant suction bone-drilling technique.</a> Journal of Visualized Experiments: JoVE. (171), e62450(2021).</li>
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</ol>

L.A. is a consultant for Stryker ENT. None of the other investigators has any relevant financial interests, activities, relationships, or affiliations that represent a relevant financial conflict of interest with respect to this work.

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 (&gt;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 H&#228;usler11. 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 &gt;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&#176; or 70&#176;, 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.

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.

<table><tbody><tr><td>Adrenalin</td><td>Sintetica</td><td></td><td></td></tr><tr><td>Belucci microscissors</td><td>Olympus (former Richards)</td><td>8178100FX</td><td></td></tr><tr><td>Betadine solution (Povidon iodine)</td><td>Mundipharma Medical Company</td><td></td><td></td></tr><tr><td>Carbostesin</td><td>Sintetica</td><td></td><td>Bupivacain 2.5 mg/mL</td></tr><tr><td>Cup forceps</td><td>Olympus (former Richards)</td><td></td><td></td></tr><tr><td>Curette</td><td>Olympus (former Richards)</td><td>13-0147</td><td></td></tr><tr><td>Curved suction tubes</td><td>Spiggle &amp;amp; Theis</td><td>302007NV und6066500100</td><td></td></tr><tr><td>Drill</td><td>Bienair</td><td></td><td>2 mm rough diamond drill</td></tr><tr><td>FOX laser</td><td>A.R.C. Laser GmbH</td><td></td><td></td></tr><tr><td>Gelfoam (absorbable gelatine compressed sponge)</td><td>Pfizer Injectables</td><td>GS-010DP</td><td>absorbable gelatin sponge</td></tr><tr><td>Gloves</td><td>Sempermed</td><td></td><td>Appropriate size</td></tr><tr><td>Hooks</td><td>Olympus (former Richards)</td><td>&amp;nbsp;13-0201, 13-0202, 13-0204, 13-0206</td><td>0.3&amp;ndash;0.6 mm</td></tr><tr><td>Hydrocortison/neomycin/polymyxin otic /Cortisporin Otic Solution</td><td>Pfizer</td><td></td><td></td></tr><tr><td>Needle</td><td>Olympus (former Richards)</td><td>13-0207</td><td>27 G</td></tr><tr><td>Operating Microscope</td><td>Leica</td><td>E 114637</td><td></td></tr><tr><td>Otologic dissectors</td><td>Olympus (former Richards)</td><td></td><td></td></tr><tr><td>Ribbon gauze</td><td></td><td></td><td></td></tr><tr><td>Round knifes</td><td>Olympus (former Richards)</td><td>13-0211 13-0212</td><td></td></tr><tr><td>Silk dressing</td><td>Otosilk</td><td></td><td></td></tr><tr><td>Speculum</td><td>Olympus (former Richards)</td><td>OK 082R</td><td></td></tr><tr><td>Surgical Mask</td><td>Halyard</td><td>48247</td><td></td></tr><tr><td>Water to rinse</td><td>Ringer</td><td></td><td></td></tr></tbody></table>

the microscopic transcanal approach in stapes surgery revisited

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.

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 &#177;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 &#60;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&#39; 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 &#177; 0.2 mm), mean diameter was 0.46 mm (range 0.4-0.6 mm, SD &#177; 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.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/63011/63011fig1v2.jpg" /> 
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. <a href="https://www.jove.com/files/ftp_upload/63011/63011fig1v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/63011/63011fig2v2.jpg" /> 
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. <a href="https://www.jove.com/files/ftp_upload/63011/63011fig2v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/63011/63011fig3v2.jpg" /> 
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). <a href="https://www.jove.com/files/ftp_upload/63011/63011fig3v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/63011/63011fig4v2.jpg" /> 
Figure 4: Ear speculum holder. The figure illustrates the design of the speculum holder. <a href="https://www.jove.com/files/ftp_upload/63011/63011fig4v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/63011/63011fig5v2.jpg" /> 
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. <a href="https://www.jove.com/files/ftp_upload/63011/63011fig5v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/63011/63011fig6v2.jpg" /> 
Figure 6: Positioning of the hands. The wrist of the surgeon should be in (A) neutral position and (B) not extended. <a href="https://www.jove.com/files/ftp_upload/63011/63011fig6v2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Table 1: Summary of the study. The table summarizes the patient and operation characteristics <a href="https://www.jove.com/files/ftp_upload/63011/table1_summary.xlsx" target="_blank">Please click here to download this Table.</a>
Table 2: Patient and operation characteristics. The table shows individual patient details and operation characteristics. <a href="https://www.jove.com/files/ftp_upload/63011/table2.xlsx" target="_blank">Please click here to download this Table.</a>

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The Microscopic Transcanal Approach in Stapes Surgery Revisited

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 ...

the-microscopic-transcanal-approach-in-stapes-surgery-revisited

Research

JoVE Journal

Medicine

2.3K Views.  University of Bern. This article describes the microscopic transcanal technique for stapes surgery, providing step-by-step surgical instructions for familiarizing surgeons with this approach. 

Video: The Microscopic Transcanal Approach in Stapes Surgery Revisited

Canalostomy As a Surgical Approach to Local Drug Delivery into the Inner Ears of Adult and Neonatal Mice

Local delivery of therapeutic drugs into the inner ear is a promising therapy for inner ear diseases. Injection through semicircular canals (canalostomy) has been shown to be a useful approach to local drug delivery into the inner ear. The goal of this article is to describe, in detail, the surgical techniques involved in canalostomy in both adult and neonatal mice. As indicated by fast-green dye and adeno-associated virus serotype 8 with the green fluorescent protein gene, the canalostomy facilitated broad distribution of injected reagents in the cochlea and vestibular end-organs with minimal damage to hearing and vestibular function. The surgery was successfully implemented in both adult and neonatal mice; indeed, multiple surgeries could be performed if required. In conclusion, canalostomy is an effective and safe approach to drug delivery into the inner ears of adult and neonatal mice and may be used to treat human inner ear diseases in the future.

Here we describe canalostomy procedure which allows local drug delivery into the inner ears of adult and neonatal mice through the semicircular canal with minimum damage to hearing and vestibular function. This method can be used to inoculate viral vectors, pharmaceuticals, and small molecules into the mouse inner ear.

Local delivery of therapeutic drugs into the inner ear is a promising therapy for inner ear diseases. Injection through semicircular canals (canalostomy) ...

Genetics

Discovering Middle Ear Anatomy by Transcanal Endoscopic Ear Surgery: A Dissection Manual

The middle ear is located in the center of the temporal bone and bears a highly complex anatomy. The recently introduced exclusively endoscopic transcanal approach to the middle ear is a minimally invasive technique sparing the bone and mucosa of the mastoid bone, since the middle ear is accessed through the external auditory canal. This emerging method has several advantages over the traditional (microscopic) approaches to the middle ear such as the panoramic wide-angle views of the anatomy, the possibility to approach and magnify tiny structures, and the possibility of looking around the corner using angled endoscopes.
The cadaveric dissection method presented here consists of an overview on the technical requirements and a precise description of a step-by-step protocol to discover the anatomy of the middle ear. Each step and anatomical structure is carefully described in order to provide a comprehensive guide to endoscopic ear anatomy. In our opinion, this is particularly important to any novice in endoscopic ear surgery as it provides thorough anatomical knowledge and may improve surgical skills.

The aim of this article is to describe the methodology of exclusively endoscopic cadaveric middle ear dissection. Moreover, we aim to provide a comprehensive guide to endoscopic middle ear anatomy.

The middle ear is located in the center of the temporal bone and bears a highly complex anatomy. The recently introduced exclusively endoscopic transcanal ...

Surgical Labyrinthectomy of the Rat to Study the Vestibular System

To study the vestibular system or the vestibular compensation process, a number of methods have been developed to cause vestibular damage, including surgical or chemical labyrinthectomy and vestibular neurectomy. Surgical labyrinthectomy is a relatively simple, reliable, and rapid method. Here, we describe the surgical technique for rat labyrinthectomy. A postauricular incision is made under general anesthesia to expose the external auditory canal and the tympanic membrane, after which the tympanic membrane and the ossicles are removed without the stapes. The stapes artery, which is located between the stapes and the oval window, is a vulnerable structure and must be preserved to obtain a clear surgical field. A hole to fenestrate the vestibule is made with a 2.1-mm drill bur superior to the stapes. Then, 100% ethanol is injected through this hole and aspirated several times. Meticulous dissection under a microscope and careful bleeding control are essential to obtain reliable results. Symptoms of vestibular loss, such as nystagmus, head tilting, and a rolling motion, are seen immediately after surgery. The rotarod or rotation chair test can be used to objectively and quantitatively evaluate the vestibular function.

This protocol describes the surgical labyrinthectomy of a rat, which is a useful method for studying the vestibular system.

To study the vestibular system or the vestibular compensation process, a number of methods have been developed to cause vestibular damage, including ...

An Endoscopic Transcanal Transpromontorial Approach for Vestibular Schwannomas using a Computer-Based Three-Dimensional Imaging System

A 2D monocular endoscope has been used in transcanal transpromontory vestibular schwannoma surgery instead of craniotomy. However, the absence of depth perception is the limitation of this approach. With the loss of depth perception, the surgeon will be not able to perform delicate and particularly complicated surgery. A binocular endoscope has been developed to provide stereoscopic vision with better depth perception for complicated anatomic structures and has been applied in some endoscopic surgeries. However, the diameter of the endoscope is a limitation in the performance of transcanal otologic surgeries. A small diameter endoscope facilitates easier surgery in a restricted space. A computer-based 3D imaging system can obtain 3D images in real-time using a small monocular endoscope. In this study, to evaluate the feasibility of a computer-based 3D imaging system for endoscopic lateral skull base surgery, we applied this 3D imaging system in a transcanal transpromontorial approach in two patients with vestibular schwannomas. The surgical procedure was completed without complication in these two cases. There was no mortality, perioperative complications, nor notable postoperative complications. Using this computer-based 3D imaging system, a better depth perception and stereoscopic vision was observed compared to a conventional 2D endoscope. The improvement in depth perception offers superior management of the complicated surgical anatomy.

Here, we present a transcanal transpromontorial approach for vestibular schwannomas using a computer-based three-dimensional (3D) imaging system combined with a two-dimensional (2D) endoscope. This system provided stereoscopic vision, better depth perception and reduced visual fatigue. This 3D imaging system enabled the application of 3D vision technology in endoscopic lateral skull base surgery.

A 2D monocular endoscope has been used in transcanal transpromontory vestibular schwannoma surgery instead of craniotomy. However, the absence of depth ...

Endaural Endoscopic Atticoantrotomy (Retrograde Mastoidectomy) using a Constant Suction Bone-drilling Technique

Endoscopic middle ear surgery is a widely employed minimally invasive surgical technique to address middle ear and mastoid pathology. Bone drilling is the main technical challenge of endoscopic middle ear surgery. The accompanying video describes the detailed protocol of a constant-suction bone-drilling technique and the procedure of endaural exclusive endoscopic atticoantrotomy (retrograde mastoidectomy) using this technique. The main components of this bone-drilling technique include a soft and flexible suction tube, which is placed into the tympanic cavity to provide constant suction, and a soft sleeve, which is wrapped around the drill shaft to prevent the high-speed rotating shaft from damaging the lens of the endoscope. With these simple modifications, the traditional otological electrodrill can be used for drilling a tiny endaural incision in endoscopic middle ear surgery. Based on this bone-drilling technique, endaural endoscopic atticoantrotomy (retrograde mastoidectomy) can be successfully established for the removal of various amounts of bone, depending on the extent of the lesion. The short-term postoperative outcome seems promising.

Endaural Endoscopic Atticoantrotomy Retrograde Mastoidectomy using a Constant Suction Bone-drilling Technique

In this paper, we present the protocol and short-term outcomes of endaural exclusive endoscopic atticoantrotomy using a constant suction bone-drilling technique.

Endoscopic middle ear surgery is a widely employed minimally invasive surgical technique to address middle ear and mastoid pathology. Bone drilling is the ...

An Integrated (Microscopic/Endoscopic) Dissection Ear Surgery Course

Traditionally, otologic surgical training consisted of microscopic cadaveric dissections. However, during the last decades the endoscope has significantly changed the surgical perspective in the otologic field. Thus, the modern ear and lateral skull base surgeon should master the entire spectrum of endoscopic and microscopic approaches, with the aim of tailoring the procedure and guaranteeing the best possible functional outcome. This work proposes a step-by-step guided and illustrated dissection course, including indications for the setup of the cadaver lab and the integration of the microscope and endoscope to enhance the use of both instruments. The alternation of the endoscope and microscope allows the novice to train the correct handling of the instruments in the surgical field under both optical views. This aspect is of utmost importance since it is not advisable to start off a technique without practicing the other one, as both are important and complementary in the modern otologic surgery setting.

An Integrated Microscopic/Endoscopic Dissection Ear Surgery Course

Traditionally, otologic surgical training consisted of microscopic cadaveric dissections. However, during the last decades the endoscope has significantly ...

Step-by-Step Stapedotomy through Transcanal Exclusive Endoscopic Approach

In recent years there has been an increasing trend in the use of the endoscope to treat a variety of middle ear pathologies, including otosclerosis. Several studies comparing traditional microscopic and endoscopic stapes surgery have reported similar hearing results and an overall low rate of complications. The endoscope has unraveled its full potential in demanding settings of stapes surgery, such as unfavorable anatomy of the oval window niche or revision cases. Reduced manipulation of the chorda tympani and low rate of post-operative dysgeusia are further benefits to mention for endoscopic stapes surgery.
Being a one-handed technique, management of bleeding, positioning, and crimping of the prosthesis may be challenging for novice endoscopic surgeons, so some training in endoscopic ear surgery is recommended before performing endoscopic stapedotomy. The problem of sharing the surgical field between the endoscope and the operating instruments could be easily overcome if proper instruments positioning is understood. One-handed bleeding control in the narrow space of the ear canal may represent an issue during the elevation of the tympano-meatal flap, possibly discouraging the surgeon since the preliminary steps of surgery. Following appropriate technique to raise the flap and the collaboration with the anesthesiology team in keeping the blood pressure low guarantee an adequate bleeding control in most cases.
The aim of this article is to describe the entire surgical procedure of a transcanal exclusive endoscopic stapedotomy, from operating room set up and patient positioning to post-operative care. A step-by-step description of the surgical maneuvers with technical hints is reported, to guide the surgeon across the procedure and allow any ear surgeon to perform stapes surgery endoscopically.

The aim of this article is to provide a step-by-step method for endoscopic stapes surgery from operating room setting and patient positioning to post-operative care. This work would represent a guide for any otologic surgeon who is willing to treat otosclerosis with endoscopic transcanal technique.

In recent years there has been an increasing trend in the use of the endoscope to treat a variety of middle ear pathologies, including otosclerosis. ...

Endoscopic Cholesteatoma Surgery

Implementation of endoscopes in cholesteatoma surgery resulted in considerable changes in the management of cholesteatoma in the last two decades. Compared to the microscopic approach with an excellent but straight-line view and limited illumination, the introduction of endoscopes provides a wide-angled panoramic view. Moreover, angled lenses allow the surgeon to visualize the middle ear and its hidden recesses through a transcanal, minimally-invasive approach. The endoscope enables the surgeon to remove limited cholesteatoma of the middle ear and its recesses using an exclusive endoscopic technique by taking advantage of these benefits. This reduces the rate of residual disease and sparing external incisions and excessive temporal bone drilling as in a transmastoid approach. Since transcanal endoscopic access is mainly a one-handed technique, it implies the need for specific procedures and technical refinements. This article describes a step-by-step guide as a surgical manual for endoscopic removal of epitympanic cholesteatoma. Different techniques for cholesteatoma dissection and bone removal for epitympanectomy, including curettage and powered instruments such as drills and ultrasonic devices with their outcomes, are discussed. This may offer ear surgeons insight into technical refinements and the latest technological developments and open the horizon for different techniques.

The present protocol describes a step-by-step guide for the complete endoscopic removal of epitympanic cholesteatoma with different techniques for cholesteatoma dissection and bone removal for epitympanectomy.

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Real-Time Telemetric Impedance Measurements During Cochlear Implantation

Performing Repeated Intraoperative Impedance Telemetry Measurements during Cochlear Implantation

Impedance measurements are routinely performed during cochlear implantation (CI) after finalized electrode insertion. They may allow conclusions on the electrode's and implant's function. In the postoperative setting, the analysis of impedance changes enables the identification of scarring or inflammation processes around the electrode. Recent studies report associations between impedance telemetry and the site of stimulation. Consequently, repeated impedance measurements during cochlear implant electrode insertion may enable objective feedback on whether the electrode is positioned inside the perilymph or outside the inner ear. With the presented novel method, impedances can be measured in real-time during cochlear implantation. This protocol systematically explains how to perform repeated impedance recordings during CI surgery. These repeated measurements are challenging since they depend on multiple intraoperative methodological factors starting with the draping of the patient. Thus, for successful recordings, a standardized procedure is mandatory. In this article, we comprehensively illustrate the system setup and procedure of performing intraoperative measurements during CI surgery.

Author Spotlight: Advancements in Impedance Monitoring for Cochlear Implant Surgery

Here we present a protocol to conduct repeated impedance telemetry measurements during cochlear implantation (CI). They may allow conclusions on the electrode's and implant's function. Repeated impedance measurements enable objective feedback on whether the electrode is positioned inside the perilymph or outside the inner ear.

Impedance measurements are routinely performed during cochlear implantation (CI) after finalized electrode insertion. They may allow conclusions on the ...

Robot-Assisted Transcanal Endoscopic Ear Surgery for Congenital Cholesteatoma

Congenital cholesteatoma accounts for 25% of cholesteatoma cases in children. Transcanal Endoscopic Ear Surgery (TEES) is ideal for these patients because it offers a wide endoscopic view of the middle ear and a minimally invasive approach. The two main limitations are the loss of one operative hand and a narrow external auditory canal in younger children. Here, we present the case of a 3-year-old patient with a Potsic stage III congenital cholesteatoma adherent to the incus and branches of the stapes. A robotic-assisted TEES procedure was performed, during which a robotic arm with 6 degrees of freedom held a 0&#176;, 2.9 mm wide endoscope, enabling the surgeon to work in a narrow environment with both hands. The procedure's duration was 2 h and 9 min, including 16 min for the installation and draping of the robotic arm. After a trans-canal approach, the cholesteatoma was dissected from the ossicles using both a needle (or sickle knife) and suction to stabilize the ossicles and limit the risk of hearing trauma. The cholesteatoma was debulked to reduce its size, allowing it to be pushed under the malleus anteriorly and then separated from other adherences before removal. A tragal cartilage graft was used to reinforce the tympanic membrane.

This protocol describes the removal of congenital cholesteatoma using minimally invasive transcanal endoscopic ear surgery with a two-handed approach and a robotic endoscope holder.

Congenital cholesteatoma accounts for 25% of cholesteatoma cases in children. Transcanal Endoscopic Ear Surgery (TEES) is ideal for these patients because ...