Comparative Atlas of Endoscopic Ear Surgery: Training Techniques Based on an Ovine Model 3030470040, 9783030470043

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Comparative Atlas of Endoscopic Ear Surgery Training Techniques Based on an Ovine Model Marco Bonali Livio Presutti Daniele Marchioni Editors

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Comparative Atlas of Endoscopic Ear Surgery

Marco Bonali  •  Livio Presutti Daniele Marchioni Editors

Comparative Atlas of Endoscopic Ear Surgery Training Techniques Based on an Ovine Model

Editors Marco Bonali Department of Otolaryngology - Head and Neck Surgery University Hospital of Modena Modena Italy

Livio Presutti Department of Otolaryngology - Head and Neck Surgery University Hospital of Modena Modena Italy

Daniele Marchioni Department of Otolaryngology - Head and Neck Surgery University Hospital of Verona Verona Italy

This work contains media enhancements, which are displayed with a “play” icon. Material in the print book can be viewed on a mobile device by downloading the Springer Nature “More Media” app available in the major app stores. The media enhancements in the online version of the work can be accessed directly by authorized users. ISBN 978-3-030-47004-3    ISBN 978-3-030-47005-0 (eBook) https://doi.org/10.1007/978-3-030-47005-0 © Springer Nature Switzerland AG 2021 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

To my wife, Simona, for all her personal support and her ability to make my life better. To my children, Andrea and Beatrice, for magnifying my existence. To my parents, Mauro and Maria Teresa, who have shaped me into the man I am today. —Marco Bonali To all the young doctors who would like to dedicate their efforts to otologic surgery. —Livio Presutti To the new generations of otosurgeons, hoping this book will be a new starting point for the development of mini-invasive techniques to improve patient care. —Daniele Marchioni A special dedication: To the memory of David Pothier (neurotologist at Toronto General Hospital)—an excellent surgeon and a colleague who worked hard to encourage the development of endoscopic ear surgery training—but, most of all, a great friend. —The Editors

Foreword

During the past few years, I have been blessed by being among very eminent visionary otologists motivated to establish and promote endoscopic ear surgery (EES). United to achieve the same goal, the International Working Group on Endoscopic Ear Surgery (IWGEES) was created on the basis of strong bonds of professional and friendship relations. Looking back, I realize that this league carried out the task with tremendous success. Today, I am thrilled to see a new generation of otologists carrying the mission forward. Dr. Marco Bonali, one of the most driven otologists of the new generation, has accomplished an excellent task in publishing this new atlas, which will serve as a learning and teaching tool for young otology residents and fellows. It has been stirring over the last two decades to witness the introduction of endoscopic ear surgery in the field of otology and neurotology. As we learn to utilize novel techniques, revise old concepts, and set new boundaries, development of unique areas of expertise becomes mandatory. Although several recent and excellent dissection manuals are present in our libraries, no surgical atlas dealing with training techniques based on an ovine model has been published until now. This book, Comparative Atlas of Endoscopic Ear Surgery: Training Techniques Based on an Ovine Model, is an exceptionally comprehensive practical review, which will improve our anatomical knowledge and surgical skills in endoscopic ear surgery. It is designed to provide the reader with elaborate knowledge about contemporary surgical steps and anatomical details of the ovine model compared with the human structures of the middle and inner ear. Ample space is provided for understanding the endoscopic anatomy and surgery of the ear, together with superb, clear figures and detailed legends. The organization of the sections provides a perfect road map for teaching and training young otologists to master endoscopic ear surgery. Many of these operative procedures performed in ovine models will provide contemporary and innovative experience that will be brought to bear during human endoscopic surgical procedures.

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Foreword

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This book is one that, in my opinion, will be an excellent addition to the literature and one that all trainees and experts in the field of otology will keep in every temporal bone dissection laboratory. With much to be admired about the selection of topics and authors, this book is a tribute to its editors and publisher. Mohamed Badr-El-Dine, MD Professor of Otolaryngology Head of Otology, Neurotology and Skull Base Surgery Unit Faculty of Medicine, Alexandria University, Egypt President of the International Working Group on Endoscopic Ear Surgery President of the Egyptian Society of Skull Base Surgery

Preface

Endoscopic techniques were introduced into otologic surgery, with the aim of visualizing middle ear pathology at difficult sites during surgical treatment, in the 1990s. As a result of the spread of minimally invasive surgical techniques, the transcanal endoscopic approach progressively gained popularity as a tool in the surgery of middle ear diseases. During the last decade, different surgeons have applied exclusive endoscopic techniques to middle ear pathologies such as cholesteatoma, ossicular chain defects, and otospongiosis. More recently, other techniques have been developed to access the lateral skull base through the external auditory canal, choosing either a combined (endoscopic–microscopic) approach or even an exclusive endoscopic approach. At present, transcanal endoscopic surgery is widely applied in the otologic field all over the world. This innovative technique is also affecting the international scientific community, with a growing number of publications in international scientific journals. As in all surgical procedures, adequate training of surgical skills during cadaveric dissection courses is advisable. Surgical simulation represents a fundamental and mandatory part of the learning curve for a surgeon because it enhances dexterity and allows experience to be gained in performing specific procedures. The latter is required for successful outcomes during future interventions in order to avoid surgical mistakes. Human cadaveric dissections obviously represent the best option to develop skills for real surgery. However, the availability of such specimens in some countries is limited because of high costs and local regulations. For these reasons, we have developed a different training program for endoscopic ear surgery in an ex vivo ovine model. The animal model represents a suitable, inexpensive, and reliable alternative to use of human cadaveric specimens. The safety and viability of the ovine model has recently been described for many procedures in otorhinolaryngology. The aim of this book is to introduce the reader to the world of endoscopic ear surgery by giving an overview of all such surgical procedures in humans. Moreover, it is a comprehensive atlas of the same procedures in the ovine model. Every chapter has been written by authors with outstanding experience in endoscopic ear surgery, comparing the surgical procedures performed in humans with those performed in the ovine model. “Hints and Pitfalls” subheadings give the reader important tips that should be kept in mind during surgery. Our aim is to give the reader the opportunity to achieve the skills needed to perform procedures such as myringoplasty, ossiculoplasty, and tympanoplasty through an endoscopic transcanal approach, reducing the costs and time needed to obtain an ix

Preface

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adequate level of skill to perform the same procedures in a real-life setting. We strongly believe that this comparative atlas describing both human and ovine surgical skills will be useful for surgeons coming from countries where the availability of human cadavers and gross anatomy laboratories is poor, and also for those who are approaching endoscopic ear surgery. It would be great to be able to spread endoscopic ear surgery by reducing the costs of surgical training and increasing the number of surgeons able to perform these techniques. The training program proposed herein would help in doing this if it was adopted on a larger scale. This book, organized as an atlas with high-­ quality figures and text explanations, could become a reference for residents and surgeons who aim to reach the top of their learning curve in endoscopic ear surgery as fast as possible. Modena, Italy Modena, Italy  Verona, Italy 

Marco Bonali Livio Presutti Daniele Marchioni

Acknowledgements

The editors wish to thank the staff of the Hearing Research Center at the Artificial Organ (ARTORG) Center for Biomedical Engineering, University of Bern, for kindly making available their rooms and instruments for dissection of specimens. In particular, special thanks go to the group head, Dr. Wilhelm Wimmer, and to the laboratory manager, Dr. Lukas Anschuetz, who is a great friend of ours. We also thank all members of the International Working Group on Endoscopic Ear Surgery because the history of endoscopic ear surgery took its first steps with that group of friends, and from there it has spread all over the world. A special mention should be given to Dr. Matteo Fermi, former resident of the Ear, Nose, and Throat (ENT) Department, at University Hospital of Modena, for his great support in the drafting of this book.

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Contents

1 Hints and Pitfalls: How to Start Endoscopic Ear Surgery Training����������������������������������������������������������������������   1 Matteo Alicandri-Ciufelli, Federica Canzano, Giulia Molinari, Francesco Mattioli, Muaaz Tarabichi, Lukas Anschuetz, and Livio Presutti 2 Surgical Instruments and Preparation of the Specimen��������������   9 Marco Bonali, Daniele Bernardeschi, Nirmal Patel, Michael Ghirelli, Ignacio Javier Fernandez, Matteo Fermi, Andrea Sacchetto, and Daniele Marchioni 3 Comparative Anatomy and Radiology: Human vs. Ovine Model������������������������������������������������������������������  29 Matteo Fermi, Seiji Kakehata, Matteo Alicandri-­Ciufelli, Marco Bonali, Anna Maria Billi, Francesca Cavalleri, and Abraam Yacoub 4 Myringotomy and Transtympanic Ventilation Tube Positioning ������������������������������������������������������������������������������  53 Domenico Villari, Adrian James, Marco Bonali, Francesco Maccarrone, Andrea Martone, and Livio Presutti 5 Endoscopic Approach to the Tympanic Cavity: Tympanomeatal Flap and Canalplasty������������������������������������������  73 Marco Bonali, Matteo Fermi, Brandon Isaacson, Daniel J. Lee, Gaetano Ferri, Davide Soloperto, Daniela Lucidi, and Livio Presutti 6 Myringoplasty���������������������������������������������������������������������������������� 113 Francesco Mattioli, Matteo Fermi, Giulia Molinari, Marco Bonali, Michael Ghirelli, Daniele Marchioni, George B. Wanna, and Lukas Anschuetz 7 Ossiculoplasty���������������������������������������������������������������������������������� 157 Ignacio Javier Fernandez, Matteo Fermi, Stéphane Ayache, Giuseppe Panetti, Claudio Melchiorri, Gaia Federici, Daniele Marchioni, and Marco Bonali

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8 Stapes Surgery���������������������������������������������������������������������������������� 199 Lukas Anschuetz, Alejandro Rivas Campo, Cecilia Botti, Giulia Molinari, Domenico Villari, Ignacio Javier Fernandez, Matteo Fermi, and Marco Bonali 9 Round Window Dissection and Cochlear Implantation �������������� 239 Ignacio Javier Fernandez, Marco Caversaccio, Michael Ghirelli, Matteo Fermi, Luca Bianconi, Abraam Yacoub, and Lukas Anschuetz 10 Approach to Internal Auditory Canal�������������������������������������������� 271 Livio Presutti, Matteo Fermi, Lukas Anschuetz, Luca Firrisi, Michael Ghirelli, Marco Bonali, and Daniele Marchioni

Contents

List of Videos

Video 2.1  Hair trimming. The step of hair trimming is showed under magnified endoscopic view, with particular attention to the position of the micro-scissors. During this step is very important to avoid injuring the skin because in live surgery a tedious bleeding may occur. At the end of the trimming procedure, the tympanic membrane is clearly visualized Video 4.1  Myringotomy and grommet insertion. The procedure of grommet insertion is explained. First step is represented by the myringotomy at the level of the pars flaccida of the tympanic membrane. Then, different types of grommets are showed (straight ones and T-tube), focusing on the specific gestures to insert the ventilation tubes under endoscopic view Video 5.1  Tympanomeatal flap and canalplasty. Two different types of tympanomeatal flap to gain the access to the tympanic cavity are presented in this video. The first is the regular flap and it allows the visualization of the ossicular chain region. The second is associated to the canalplasty and is used to reach the round window region and to perform the approach to the internal auditory canal Video 6.1  Myringoplasty. The video shows the reconstruction of the tympanic membrane with different materials. In particular, an implantable biomaterial (Cook Medical, Biodesign Otologic Repair Graft®, Bloomington, IN, USA) is cut and tailored to fit the eardrum defect. Another option is the creation of a composite cartilage-perichondrium graft, taken from the nasal septum of the ovine Video 7.1  Ossiculoplasty. The ossiculoplasty in the ovine model can be performed both as PORP (partial ossicular replacement prosthesis) and as TORP (total ossicular replacement prosthesis). PORP procedure is done by removing the incus and by positioning a remodeled ossicle, a cartilage double layer graft, or a synthetic material between the malleus and the stapes head. The TORP approach requires the removal of the stapes superstructure and the interposition of a synthetic prosthesis or the remodeled incus between stapes footplate and malleus

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Video 8.1   Stapes surgery. Stapes surgery training in the ovine model can be divided in stapedotomy procedure and stapedectomy procedure. Both the approaches can be performed with laser or microdrill/skeeter. A synthetic prosthesis is placed in the footplate hole and attached to the incus (stapedotomy) or it is positioned over a graft of perichondrium in the oval window region after stapes removal and the ring of the prosthesis is matched to the incus (stapedectomy) Video 9.1   Facial nerve decompression. The second tract of the facial nerve is always dehiscent in the ovine model, while the third tract can be skeletonized using a curette or a small drill, until the origin of the chorda tympani from the facial nerve is completely visualized Video 9.2   Round window dissection and CI. This video shows the dissection of the round window niche, after chorda tympani removal. The bony tegmen of the round window niche is progressively drilled and thinned using a small curette. Then, the round window membrane is opened and a cochlear implant electrode can be inserted inside the cochlea (scala tympani) through the external auditory canal under endoscopic view Video 10.1  Approach to IAC. The approach to the internal auditory canal represents the final step of the training in the ovine model. After the canalplasty and the creation of a circular tympanomeatal flap (degloved to obtain a wide surgical field), the ossicular chain is removed and the cochlear turns are opened. The vestibule is then exposed, by removing the stapes. A Piezoelectric device (Piezosurgery, Mectron, Carasco, Genova) or a small bur, or a curette, is used to open the cochleo-vestibular bone and gain access to the internal auditory canal. Finally, the acoustic-­facial bundle is exposed through the transcanal ­transpromontorial access and the first tract of the facial nerve is skeletonized

Electronic Supplementary Material:  Electronic supplementary material is available in the online version of the related chapter on Springer Link: http://link.springer.com/

List of Videos

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Hints and Pitfalls: How to Start Endoscopic Ear Surgery Training Matteo Alicandri-Ciufelli, Federica Canzano, Giulia Molinari, Francesco Mattioli, Muaaz Tarabichi, Lukas Anschuetz, and Livio Presutti

1.1

Introduction

Each type of surgery requires an adequate training period for the surgeon to familiarise with the anatomy and to develop manual skills. Ear and lateral skull base are universally considered very challenging regions for neurosurgeons, otolaryngologists and maxillofacial surgeons due to their complex anatomy and the presence of delicate vascular and nervous structures (e.g. the jugular vein, the carotid artery and the cranial nerves). The application of the endoscopic technique (endoscope-assisted or exclusive endoscopic approach) to the ear and lateral skull base has gained increasing importance worldwide in the last decades and has brought new anatomical, pathological and surgical concepts in this field. M. Alicandri-Ciufelli (*) · F. Canzano G. Molinari · F. Mattioli Department of Otolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy M. Tarabichi Department of Otolaryngology, Tarabichi Stammberger Ear and Sinus Institute, Dubai, United Arab Emirates L. Anschuetz Department of ENT, Head and Neck Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland L. Presutti Department of Otolaryngology - Head and Neck Surgery, University Hospital of Modena, Modena, Italy

Despite significant advantages compared to the use of the microscope, endoscopic ear surgery (EES) is characterised by some specific technical and manual skills that could make the learning curve of this technique particularly long. Several factors determine a deep difference between microscopic and EES. First of all, EES is a one-­handed technique: the endoscope is held in the non-dominant hand, while the opposite hand undertakes the majority of the surgery. As in other endoscopic surgeries, the surgeon needs to develop adequate hand-eye coordination. Nevertheless, the view during microscopic surgery is defined and limited by the narrowest segment of the ear canal. The fact that the entrance to the ear canal is not confined or constrained by a speculum allows the surgeon a far wider angle of attack when using the instruments in the more inaccessible areas (such as the hypotympanum or retrotympanum) [1]. In fact, transcanal operative endoscopy bypasses the narrow segment of the ear canal and provides a wide view that enables surgeons to look ‘around the corner’, even when a 0° endoscope is used (Fig. 1.1). The ‘working space’ in endoscopic surgery is cone shaped, and above the apex of the cone ‘the ear canal’ needs only to be wide enough to admit the endoscope and surgical instruments. In contrast, microscopic surgery requires an ­ ­upside-­down conical ‘working space’ that implies

© Springer Nature Switzerland AG 2021 M. Bonali et al. (eds.), Comparative Atlas of Endoscopic Ear Surgery, https://doi.org/10.1007/978-3-030-47005-0_1

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Narrowest segment of the external auditory canal

Microscope: limited field of view

Endoscope: wide field of view

Fig. 1.1  Comparison between the microscope and the endoscope regarding the wide field of view and the approach. (From Presutti L, Marchioni D. Endoscopic Ear Surgery. Principles, Indications, and Techniques. Thieme 2015)

much more bone removal laterally to obtain access and to prevent the surgeon from ‘digging his/herself into a hole’ [1]. Moreover, the magnification of the structures under endoscopic view makes the surgical details much clearer and easy to understand. This is relevant also during the training because the endoscope combines magnified high-resolution images with the possibility of an extremely close vision of the anatomical structures. Another great opportunity offered by endoscopic live surgery in learning anatomy and technical skills is that anyone watching the screen can have the same view of the surgeon (Fig.  1.2), differently from the microscopic approach. This allows a live interaction between the trainee and the trainer, who can suggest surgical gestures or correct technical mistakes in real time. An important point to underline is that the space of the surgical field is very limited and is shared between the optic and the surgical instruments at the same time. Some anatomical condi-

tions, such as a narrow external auditory canal, can further limit the working space. Time is required to learn how to manage intraoperative bleeding, as blood can deeply influence the quality of vision and may interfere with the surgical procedure. Especially in a narrow space, like the tympanic cavity, even a small amount of blood in the field could prevent the continuation of surgery. Anschuetz et  al. have analysed the management of bleeding in endoscopic ear surgery (EES), concluding that even the highest bleeding scores could be managed with an exclusively endoscopic technique, with no shift to the microscopic approach observed. They also underline that the development of optimal strategies is particularly important for beginners in EES, since the management of a possibly narrow and bleeding EAC (external auditory canal) may be frustrating. The initial steps during elevation of the tympanomeatal flap are challenging to a novice surgeon and require patience to

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Fig. 1.2  Operative setting: the surgeon and the attendants are watching the same screen. The surgical manoeuvres and the anatomical details are clearly visible and can be discussed in real time

repeatedly clean the surgical field, so as to safely perform the required steps [2]. Furthermore, certain manual dexterity is needed to surgically dominate hidden recesses or very medial regions far from the entry point of the optic (such as the cerebellopontine angle). To improve and facilitate the acquisition of all these skills in endoscopic ear and lateral skull base surgery, a specific and dedicated training programme should be followed. Since the endoscopic technique is relatively new, a training programme has not yet been universally established in this context.

1.2

Proposal of a Training Programme: Principles and General Features

In 2007, Snyderman et  al. published an article that suggested a training programme for acquisition of surgical skills in endonasal anterior skull base surgery. The authors standardised the training by proposing a modular incremental training programme, constituted by five stages, from ‘basic’ procedures to very complex operations performed by exclusive endonasal approach. The first level was spheno-ethmoidectomies, while the highest level of difficulty (level V) included the treatment of aneurisms and highly vascularised tumours. The first levels (I and II) were those expected to be achieved within resi-

dency and then the programme progressed in complexity. Similarly, present authors have proposed a staged training programme for acquisition of surgical skills for endoscopic middle ear and lateral skull base surgery. This programme consists of five stages that follow a progression from lateral to medial in a coronal plane of the ear and the temporal bone (Fig.  1.3). In each stage, operations that have a homogeneous grade of difficulty and risks are reported [3]. These steps reflect the progressive complexity of the anatomy and the presence of increasingly important structures encountered from the external ear to the internal auditory canal. In fact, the potential risk of damage of vessels or nerves represents a fundamental criterion for the progression towards higher steps, as shown in Table 1.1. Another factor considered in establishing the steps and the progression of training was the experience gained by surgeons who had been dealing with endoscopic ear and lateral skull base surgery since the beginning of the endoscopic era of otologic surgery. Indeed, this progressive training mirrors the gradual development of the endoscopic technique in this context. A gradual introduction of endoscope for middle ear pathology treatment has taken place since the 1990s. Endoscopy was used primarily for the visualisation of hidden areas, such as the retrotympanum, during classic microscopic tympanoplasties. Gradually, it was also

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I

II - III

IV

V

Fig. 1.3 Schematic drawing showing progression of training in a coronal plane, from a lateral to a medial direction. Levels are indicated in Roman numbers Table 1.1  Structures at risk during endoscopic ear surgery training Level I Not relevant risks Level II Ossicular chain, chorda tympani Level III Ossicular chain, facial nerve, labyrinth Level IV Facial nerve, labyrinth, jugular bulb, carotid artery Level V Facial nerve, jugular bulb, carotid artery, lower cranial nerves, vessels of CPA (AICA), brainstem. Risk of post-operative CSF leak

used in surgery to replace the microscope as the main tool during middle ear operations. Exclusive endoscopic tympanoplasty for the cholesteatoma treatment was first described by Tarabichi et  al [4]. The new concept of EES redirected the attention away from the less critical areas (i.e. mastoid) towards the tympanic cavity and its ‘hard-toreach’ extensions. The endoscopic technique was codified for a minimally invasive eradication of limited attic cholesteatoma, preserving the ossicular chain whenever possible, with complete removal of the disease. From this starting point, a clinical application of the transcanal endoscopic approach has allowed to extend the indications of this technique to the cholesteatoma of the whole tympanic cavity without mastoid involvement. At present, the main application of endoscopic surgery is in the surgical treatment of middle ear pathology, but with the natural evolution of the technique, there have also been

Table 1.2  Timeline of publication of new subjects dealing with endoscopic ear and lateral skull base surgery by our team 2008 Endoscopic-assisted tympanoplasties 2009 Approaches to tensor fold area, approaches to sinus tympani 2010 Exclusive endoscopic ‘closed’ tympanoplasties 2011 Exclusive endoscopic ‘open’ tympanoplasties 2012 – 2013 Pilot lateral skull base procedures; first cochlear schwannoma treated by transpromontorial approach; benign neoplasms removal 2014 Endoscopic cochlear implant procedure; approach to geniculate ganglion; approach to petrous apex lesions 2015 Endoscopic cochlear implants in malformations; pediatric tympanoplasties 2016 Case series of exclusive transcanal transpromontorial approach to internal auditory canal to treat vestibular schwannomas; endoscopic stapes surgery

advantages in lateral skull base diseases. Through the experience of recent years, present authors progressively noticed that the inner ear and the entire temporal bone could also be accessed in an endoscopic-­assisted fashion or even by exclusive endoscopic transcanal approaches. For the first time, an exclusive endoscopic approach to the internal auditory canal (IAC) was described and used to remove a cochlear schwannoma involving internal auditory canal (IAC) in March 2012. The operation used a direct transcochlear approach from lateral to medial and from external to internal auditory canal without any external incision [5]. Interestingly, when looking at timeline and subjects of publications dealing with endoscopic ear surgery published over the years by the present authors, it appears evident that the temporal line of the publications reflects the same steps of the training programme (Table 1.2). Another relevant factor derived from the experience of senior surgeons and applied in the creation of this staged programme is the development of complementary expertise. To tackle a certain stage of the training programme, it is advisable that the trainer has already acquired some skills from similar settings of surgery, as specified in Table  1.3. For example, for levels II and III of training, it is recommended that the surgeon has

1  Hints and Pitfalls: How to Start Endoscopic Ear Surgery Training Table 1.3  Different levels of complementary expertise to better improve the endoscopic ear surgery learning curve Level I Endoscopic nasal surgery Level II Microscopic middle ear surgery Level III Microscopic middle ear surgery Level IV Microscopic transpetrous approaches Level V Acoustic neuroma surgery (retrosigmoid, translabyrinthine approaches)

performed some microscopic middle ear surgical procedures, not only to familiarise with the middle ear anatomy, but also to gain some confidence in manoeuvring the instruments inside the tympanic cavity. Despite the acquired skills suggested before attempting every level can be nowadays important, the authors do not consider them as mandatory. This is due to the fact that the evolution of middle ear and lateral skull base is at present very difficult to predict and will mostly depend on development of technologies, instrumentation and consequent evolution and modification of the technique. It is not unlikely that future generations will begin their expertise in this surgical field using directly and exclusively the endoscope, and so, for example, the expertise in microsurgery could progressively become less necessary. Anyway, at present, the acquired skills mentioned will certainly increase the proficiency and safety in performing some operations and may also very likely shorten the learning curve [3]. The levels of the programme in detail (see Table 1.4) • Level I of the training programme includes office-based explorations of EAC and tympanic membrane or tympanic tube placement. In fact, those basic procedures allow the surgeon to obtain the first impressions about depth of the field, hand-eye coordination, magnification and surgical manoeuvring using the endoscope. The risks of severe complica-

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Table 1.4  Transcanal endoscopic middle ear and lateral skull base training programme Middle ear

Inner ear and lateral skull base

Level I Office-based endoscopies for diagnosis Myringotomies with/without tympanic tube placement Level II Combined approaches (endoscope-­ assisted microscopic surgeries) Office-based tympanic perforation repair Myringoplasties Endoscopic explorative tympanotomies with/without ossiculoplasties Level III Tympanoplasties for cholesteatoma Stapedoplasties Facial nerve decompression Endoscopic-assisted cochlear implants procedures Endoscopic resection of middle ear neoplasms (e.g. paragangliomas) Level IV Endoscopic suprageniculate approaches Infracochlear approaches Transpromontorial approaches for inner ear disease Level V Endoscopic transcanal transpromontorial approach for IAC pathology

tions in this kind of procedures are virtually absent. Prior expertise in the endoscopic nasal surgery can be very helpful at this stage, although not mandatory, to acquire skills. This step can be attempted very early, from the beginning of residency, during normal office evaluations or follow-up in the outpatient clinic. In addition, endoscopic ear de-waxing can be a good exercise at this level. • In level II, the surgeon can start using the endoscope for more operative procedures, also attempting its use inside the tympanic cleft, for example, in combined m ­ icroscopic/ endoscopic approaches. This can further improve manual skills and it allows the surgeon to familiarise with angled optics, ­

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which can be used to explore the sinus tympani, tensor fold area and protympanic spaces, looking for cholesteatoma residuals during microscopic surgeries. Level II can also include myringoplasties or explorative tympanotomies through an exclusive endoscopic approaches. In these operations, there is a potential risk of damage to the ossicular chain, and for this reason some experience must have been acquired at level I. In level II, bleeding management is very important. Unlike in the traditional ear surgery, where this incision is sometimes made and then left while the postauricular incision is started, the canal incisions are made and then the flap is lifted immediately. This can sometimes cause bleeding that makes raising the flap very difficult indeed. It is at this stage that those new to the technique will believe that the advantages of the endoscopic ear surgery are exaggerated and the difficulties are far greater than expected. Once the initial part of the surgery has been overcome, the benefits of the wide field of view and improved access become obvious. It is crucially important to get through the early part of the surgery so as to be able to truly appreciate what ­endoscopic surgery of the ear really has to offer [1]. Confidence in bleeding control is probably the most difficult skill to acquire in endoscopic ear and lateral skull base surgery, and in most cases it can discourage the surgeon in training. Bleeding control requires not only patience and good manual skills, but also appropriate positioning of the patient, cooperation with the anaesthesiologist in keeping blood pressure low and an adequate technique in raising the tympanomeatal flap (such as the use of hot blades). These factors are considered fundamental for progressing towards the next levels [3]. • Level III provides exclusive approaches to treat typical pathologies of the middle ear (e.g. cholesteatoma) and more rare pathologies that could damage the ossicular chain, facial nerve or labyrinth. Although it is very likely that adequate expertise is obtained by the surgeon

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in training after levels I and II, proficiency in microscopic procedures is anyway advisable because in case of problems during surgery or in particularly difficult procedures, an eventual shift to the microscopic vision and bimanuality can be very helpful. Level III represents the final step for middle ear endoscopic surgery, but similar considerations can be done with level IV [3]. • With level IV, the trainer starts to approach the inner ear and the lateral skull base. As already documented in former articles, endoscopic approaches to lateral skull base are less invasive compared to classic microscopic procedures. Nonetheless, at this level, the former experience in microscopic approaches can be very helpful in case of necessity, due to the fact that even more delicate structures will be manipulated (facial nerve, labyrinth, jugular bulb, carotid artery) and due to the risks of a possible damage. To start dealing with endoscopic suprageniculate and infracochlear approaches, as well as transpromontorial approaches for inner ear pathology, experience in microscopic transpetrous approaches is advisable. At this stage, high-flow vascular structures such as the jugular bulb and the carotid artery must be handled and preserved, and thus confidence in recognition of anatomical landmarks and bleeding management is mandatory [3]. • In level V, where the surgeon reaches the IAC and cerebello-pontine angle (CPA), he/she must be aware of the complex anatomy of CPA with all the posterior fossa vascularisation and cranial nerves. Actually, it is also advisable to have former experience with CSF leak management and reconstruction procedures of lateral skull base to possibly avoid, or if not to deal with, post-­operative complications related to it. Moreover, strong expertise in dissecting the vestibular schwannoma can be helpful due to the fact that in exclusive endoscopic approaches it should be done by one hand only, as described in the endoscopic transcanal transpromontorial approach to IAC [3].

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1.3

Application of the Staged Training Programme to the Ovine Model

Actually, the long learning curve required to master endoscopic ear surgery, the high costs for organising and/or participating to dissection courses on cadavers, and the limitations to the access to human cadaveric specimens by financial or regulatory issues have urged the search for alterative, suitable and affordable models to practise it. The ovine model has proved to be an inexpensive, safe and reliable model for otologic surgery. The lifelike feeling of fresh specimens provides excellent tissue properties and dissection. Another advantage is the similar size and presentation of the gross anatomic structures of the ovine ear compared to the human ear. Many studies have already demonstrated the value of the sheep model as a proper training model for otologic surgery; for example, it has been described and validated for the training of stapes surgery and for the round window insertion of cochlear implants [6–8]. In the experimental study reported by Anschuetz et  al., the authors assessed the suitability of the ovine model for training in ­ exclusive endoscopic surgery, assessing the time needed for anatomical dissection and surgical procedures [9].

Fig. 1.4 (a) Right ear. Piezoelectric device is used to remove the promontory bone and to approach the inner ear, while sparing the soft tissues (like nerves or internal auditory canal dura mater). (b) Panetti self-suctioning set

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Present authors believe that the staged training programme described above can be easily applied to the ovine model. The ovine model represents an excellent setting to start manoeuvring the instruments for endoscopic ear surgery and to gain confidence in holding the endoscope and moving it inside the EAC and tympanic cavity. The instruments used for training on the sheep are the same as in the human model. Specific devices can also be applied in the ovine ear, thus performing a ‘powered dissection’, such as the Panetti self-suctioning set (Spiggle & Theis, Overath, Germany) or the Piezosurgery device (Mectron, Carasco/Genova, Italy), as shown in Fig. 1.4. Ideally, each surgical procedure can be performed on the sheep ear, as described in the following chapters of this book. Table  1.5 summarises how, with a single sheep head (two ears), the trainee can accomplish all the surgical procedures, from the tympanic cavity to the internal auditory canal. In doing this, it is advisable that the surgeon follows the steps of the training programme in light of the previous considerations. Some anatomic differences between the ovine and the human middle ear are present. For instance, the absence of an anulus separating the tympanic membrane from the mucosa of the ovine middle ear can interfere with the reliability of the actual tympanomeatal flap elevation.

can be useful to elevate the tympanomeatal flap, dissect middle and inner ear structures and remove secretions or bony debris at the same time

M. Alicandri-Ciufelli et al.

8 Table 1.5  Flowchart of the staged training programme applied to the ovine model Ear #1 1. Miringotomy and transtympanic ventilation tube positioning 2. Tympanomeatal flap elevation + canalplasty 3. Myringoplasty 4. Ossiculoplasty (partial ossicular replacement prosthesis) 5. Ossiculoplasty (total ossicular replacement prosthesis) 6. Facial nerve decompression 7. Cochlear implant (electrode insertion)

Ear #2 1. Tympanomeatal flap elevation (eardrum and EAC skin removal) 2. Stapedotomy 3. Stapedectomy 4. Transpromontorial approach to IAC

Another important difference is the absence of bleeding in sheep ex  vivo model. These conditions may make the training quite different from the real surgical situations. On the one hand, training under simplified conditions is suitable, especially for a novice. On the other hand, other features of the ovine ear make some surgical steps more difficult than in humans, forcing the trainee to acquire surgical skills that can be applied to specific situations in the operating theatre. For instance, the external auditory canal (EAC) in the sheep is quite bent and narrow and presents a bony prominence [9]. To gain access to the tympanic cavity, an enlargement of the EAC is often required and this step represents an excellent training for endoscopic drilling, canaloplasty or removal of EAC exostoses. In conclusion, the ovine model offers an excellent setting for training in EES. Following a step-

by-step programme is advisable, and it has been proved that the same stages for training on the human could be applied to the sheep in a very useful and reliable manner.

References 1. Presutti L, Marchioni D.  Endoscopic ear surgery. Principles, indications, and techniques. Stuttgart: Thieme; 2015. 2. Anschuetz L, Bonali M, Guarino P, et al. Management of bleeding in exclusive endoscopic ear surgery: pilot clinical experience. Otolaryngol Neck Surg. 2017;157:700–6. 3. Alicandri-Ciufelli M, Marchioni D, Pavesi G, Canzano F, Feletti A, Presutti L.  Acquisition of surgical skills for endoscopic ear and lateral skull base surgery: a staged training programme. Acta Otorhinolaryngol Ital. 2018;38(2):151–9. https://doi. org/10.14639/0392-100X-1878. 4. Tarabichi M, Nogueira JF, Marchioni D, et al. Transcanal endoscopic management of cholesteatoma. Otolaryngol Clin North Am 2013;46:107–30. 5. Presutti L, Alicandri-Ciufelli M, Cigarini E, et  al. Cochlear schwannoma removed trough the external auditory canal by a transcanal exclusive endoscopic technique. Laryngoscope. 2013;123:2862–7. 6. Gocer C, Eryilmaz A, Genc U, Dagli M, Karabulut H, Iriz A. An alternative model for stapedectomy training in residency program: sheep cadaver ear. Eur Arch Otorhinolaryngol. 2007;264(12):1409–12. 7. Cordero A, Del Mar MM, Alonso A, Labatut T. Stapedectomy in sheep: an animal model for surgical training. Otol Neurotol. 2011;32(5):742–7. 8. Mantokoudis G, Huth ME, Weisstanner C.  Lamb temporal bone as a surgical training model of round window cochlear implant electrode insertion. Otol Neurotol. 2016;37(1):52–6. 9. Anschuetz A, Bonali M, Ghirelli M, Mattioli F, Villari D, Caversaccio M, Presutti L.  An ovine model for exclusive endoscopic ear surgery. JAMA Otolaryngol Head Neck Surg. 2017;143(3):247–52. https://doi. org/10.1001/jamaoto.2016.3315.

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Surgical Instruments and Preparation of the Specimen Marco Bonali, Daniele Bernardeschi, Nirmal Patel, Michael Ghirelli, Ignacio Javier Fernandez, Matteo Fermi, Andrea Sacchetto, and Daniele Marchioni

2.1

Introduction

Otologic surgery has been revolutionized by the introduction of the transcanal endoscopic approach to the middle ear during the last decades [1]. This relatively new technique requires an adequate training of manual skills, as for all the surgical procedures in general [2, 3]. These abilities should be improved during cadaveric dissection courses, before starting live surgery approaches. Indeed, the dissection courses enhance the dexterity and provide experience, which are mandatory for a successful performance during future interventions. Based on these principles, surgical simulation has become a valuable and financially attractive part of surgiElectronic Supplementary Material The online version of this chapter (https://doi.org/10.1007/978-3-030-47005-0_2) contains supplementary material, which is available to authorized users. The videos can be accessed by scanning the related images with the SN More Media App.

M. Bonali Department of Otolaryngology - Head and Neck Surgery, University Hospital of Modena, Modena, Italy M. Ghirelli (*) · I. J. Fernandez · M. Fermi Department of Otolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy D. Bernardeschi AP-HP, GHU Pitié-Salpêtrière, Service ORL, Otologie, implants auditifs et chirurgie de la base du crâne, Paris, France e-mail: [email protected]

cal education with a beneficial effect on competency and patient safety [4]. Actually, fresh frozen human cadaveric specimens are the gold standard of surgical training because, compared to live surgery, they’re the most similar models to practice with. Nevertheless, their availability is limited due to high costs and local regulations. Therefore, the animal model represents a suitable, cheap, and reliable alternative. The safety of the ovine model has recently been described for a multitude of procedures in head and neck surgery [5, 6]. In otologic surgery, the sheep has been described and validated for the training of stapes surgery [7, 8], for implantable devices [9], and for the round window insertion of cochlear implants [10]. Comparative anatomy studies allowed identifying similarities and differences between the sheep and the human middle ear [11]. The suitability of the ovine model was also confirmed by comparative radiological studies [12]. In our opinion, the ovine model is very helpful to train and develop surgical skills in an N. Patel Department of Otolaryngology and Head and Neck Surgery, Royal North Shore Hospital, Sydney, NSW, Australia A. Sacchetto Department of Otolaryngology, Head and Neck Surgery, University Hospital of Verona, Verona, Italy D. Marchioni Department of Otolaryngology - Head and Neck Surgery, University Hospital of Verona, Verona, Italy

© Springer Nature Switzerland AG 2021 M. Bonali et al. (eds.), Comparative Atlas of Endoscopic Ear Surgery, https://doi.org/10.1007/978-3-030-47005-0_2

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2.2

Identification, Application, and Validation of the Surgical Model

The first experience of endoscopic ear surgery training on the ovine model was organized years ago [13]. A thorough study of the anatomy of the ovine ear and its comparison with the human one was the obvious prerequisite. A careful assessment of the possibility to use this model for surgical approaches was performed. After this phase, we started the surgical dissections on the ovine head, trying to understand which procedures could be done during the training. The surgical model was assessed on a total of 20 ears by two ENT surgeons with 4  years of experience each. The time to perform the different steps (canalplasty, middle ear dissection, myringoplasty, and ossiculoplasty) and possible complications met in real surgery were assessed. After each dissection, a detailed subjective feedback rating was provided by the involved surgeon in order to rate the quality of the model and the improvement of surgical skills on a scale from 1 (very bad) to 10 (excellent) and a senior surgeon made an external evaluation of the dissection.

All 20 specimens were successfully dissected. The mean time required to perform canalplasty was 30 min (SD: 13.23), for middle ear dissection 8  min (SD: 2.6), for myringoplasty 8  min (SD: 4.3), and for ossiculoplasty 10  min (SD: 2.7). We observed a considerable drop of time required for canaloplasty. Indeed, the required dissection time decreased from 46.4 min for the first five cases to 16.2 min for the last five cases (statistically significant improvement; Table 2.1). The observed complications during dissection were nine injuries of the tympanic membrane or the tympanomeatal flap, one section of chorda tympani, and three subluxations of the incudomalleolar joint. The stapes remained intact in all cases. The model met the expectations of the performing surgeons. During the evaluation of the subjective rating, we discovered excellent values for tissue quality (8.9 points out of 10), allover satisfaction (8.3/10), and the learn effect (8.8/10). The different steps were also very positively rated as summarized in Table 2.2. The external rating revealed values from 6 to 10 with a mean at 7.4 points out of 10. The ex vivo ovine model for ear surgery presented in this book was created to train the exclusively endoscopic approach. Surgical education requires time and financial resources in order to allow the trainee to improve his skills under the Table 2.1  Statistical evaluation of canalplasty and tympanomeatal flap elevation p=0.02 60

p=0.002

40 Minutes

education program for otologic surgeons. However, a main issue in developing an animal model for exclusive endoscopic ear surgery is the inconsistency with the human anatomy and in particular regarding the external a­ uditory canal (EAC). In our experience, one of the most difficult steps in the exclusive endoscopic approach on ovine model is the elevation of the tympanomeatal flap and the maneuvering of the instruments in a possibly bent and narrow EAC. Nevertheless, the animal model represents a great opportunity to improve the instruments maneuvering and recreate a very similar model for the main steps of endoscopic middle ear surgery, if compared to humans. The aim of our work has been to compare the human and the ovine endoscopic anatomy and to develop an useful training alternative for exclusive endoscopic ear surgery; in the second phase, we’ve applied and validated the model.

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0 1-5

6-10

10-15

15-20

2  Surgical Instruments and Preparation of the Specimen Table 2.2  Subjective feedback by the performing surgeons shown as mean (SD) values

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2.3

 reparation of the Specimen P and Setting (Fig. 2.1: Video 2.1)

Dissection Evaluation 10

Rating 1-10

9 8 7

Ti

ss

ue

Q ua lit

y O ve Le ra ar ll n R e ffe ep ct ro du ci bi lit y D ril M lin yr g in go pl O as ss ty ic ul op la st y

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supervision of an experienced surgeon. Because every manual task is improved by experience, also surgical gestures should be acquired in the operating room. However, we have to consider that the number of surgical procedures performed by residents is limited, owing to work time regulations, economic considerations and also due to importance to guarantee the safety of the patient [14]. A good alternative for training could be the use of ex vivo human specimens as training models; indeed, this kind of surgical approach is widely practiced in otologic procedures, for example, by the means of a temporal bone dissection laboratory [15]. Nevertheless, the access to human cadaveric specimens may be limited due to financial or regulatory issues. In this context, the animal model helps out as a valid alternative. The ovine model could serve as a cheap and reliable model for otologic surgery. The lifelike feeling of fresh specimens provides excellent tissue properties and dissection. Another advantage is the similar size and presentation of the gross anatomical structures compared to humans [7, 8, 16]. The learning curve in endoscopic ear surgery may be somewhat different from the traditional microscopic approaches, and therefore a proper model for exclusive endoscopic ear surgery is required.

The dissection should be performed on fresh or previously defrosted (24  h at ambient air) 6–8  months old lamb heads (adult sheep could also be used). It’s also possible to re-freeze and defrost again two or three times the specimens, while maintaining good tissues to work on. It’s mandatory to avoid younger lambs in order to have enough space inside the external auditory canal to perform the procedures, using the endoscope and the surgical instruments at the same time. In Italy, the specimens can be easily taken at the local butchery from animals intended for alimentary use. Therefore, animal welfare and adequate slaughtering are subject to alimentary and veterinary regulations. Depending on the butchery, the ovine head could be covered by soft tissues and skin with wool and hair (Fig. 2.2), or completely decorticated and without the pinna (part of the external ear) (Fig. 2.3). The latter situation is better because the preparation of the specimen is faster and the trainee can easily start to work without preliminary cleaning procedures of the ovine head. In case of a not decorticated head, there are some steps to do before starting the endoscopic ear surgery training session in order to avoid additional difficulties due to the specimen. The big pinna (part of the external ovine ear) covers completely the external auditory meatus, and so the trainee has to amputate it at about 2 cm from its insertion on the skull. If there is a large bulging of the tragus, it can be removed in order to access the external auditory canal (Fig. 2.4). The cartilaginous portion of the EAC is bent in a posterior direction. When an anterior traction is applied to the remnant of the external ear and the cartilaginous EAC, the bony part of this anatomical corridor can easily be accessed. For this reason, two tension sutures through the cartilaginous part of the EAC should be placed to gain the access

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Fig. 2.1  (Video 2.1) Hair trimming. The step of hair trimming is showed under magnified endoscopic view, with particular attention to the position of the micro-scissors. During this step is very important to avoid injuring

Fig. 2.2  The ovine head is covered by hair and wool and the external ear is still present. Notice the big pinna that covers completely the external auditory canal meatus

to the tympanic membrane: the first antero-superiorly and the second antero-inferiorly (Fig. 2.5).

2.3.1 Setting of the Dissection Lab The aim of the correct setting of the laboratory for dissection is to permit a suitable endoscopic procedure of training. The ovine head should be placed on a clean dressing. It is very important to orien-

M. Bonali et al.

the skin because in live surgery a tedious bleeding may occur. At the end of the trimming procedure, the tympanic membrane is clearly visualized (https://doi. org/10.1007/000-2a)

Fig. 2.3  The specimen is completely decorticated and the ear pinna has already been removed. In this case, the muscles, cartilage, and bony portions of the ovine head are clearly visible

tate the nose of the sheep superiorly (from 12 to 2 o’clock position), before starting the dissection, to perform the dissection in a surgical position (Figs.  2.6 and 2.7). All the surgical instruments should be positioned on the dissection table, as well as the suction system, the three-CCD camera system, and a high-resolution monitor (Karl Storz, Tuttlingen, Germany, or similar; Fig. 2.8). The nose of the ovine head can be lifted up with some gauzes to work in a less vertical position, or it can be left resting on the working table (Fig. 2.9).

2  Surgical Instruments and Preparation of the Specimen

a

b

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Fig. 2.4 (a, b) The ear pinna is cut at its base with scissors. (c) The external auditory meatus is clearly visible at the end of the procedure

a

b

Fig. 2.5 (a, b) Two stiches are placed anterosuperiorly and anteroinferiorly at the level of the most external portion of the amputated pinna to enlarge the cartilaginous portion of the external auditory canal

Figure 2.10 shows the introduction of the endoscope and the surgical instruments inside the external auditory canal from different points of view during the trainee’s endoscopic procedure.

2.4

Surgical Instruments

The standard surgical equipment for the dissection of temporal bone on human specimens is suitable also for endoscopic ear surgery training

on ovine model (Fig. 2.11). Moreover, a drill is important to perform procedures like canalplasty or stapes surgery (Fig. 2.12). In addition to these standard instruments, it is possible to use laser (CO2/KTP), skeeter, piezo surgery, Panetti self-suction instruments, or other powered tools that might be useful for different approaches. Regarding the optics and the video system, the dissections should be performed by means of 3 (better than 4) mm diameter, 15 cm length endo-

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a

b

Fig. 2.6 (a) The ovine head is placed inside a basin with the nose on the edge of the container. Notice the position of the instruments in an oblique direction. (b, c) Endoscope

a

c

and surgical instruments are inserted inside the external auditory meatus under the view in surgical position

b

Fig. 2.7 (a) The specimen is put on a clean dressing in front of the HD monitor. (b) A detail of the correct position of the ovine head, with the nose upward (2 o’clock direction)

2  Surgical Instruments and Preparation of the Specimen

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Fig. 2.8  Overview of the dissection table with the animal specimen, the monitor and camera system, and the surgical instruments set

a

b

Fig. 2.9 (a, b) Trainee’s position during the endoscopic dissection approach. In this case, the ovine head lies on the table and the nose is not lifted up. The surgeon has to

put the endoscope and the instruments inside the external auditory canal in an almost vertical direction

scopes (Karl Storz, Tuttlingen, Germany, or similar) with angles of 0° and 45° (Fig.  2.13), a three-­CCD camera system, and a high-resolution monitor (Karl Storz, Tuttlingen, Germany, or similar).

The surgical instruments for endoscopic ear surgery training on ovine model are shown in detail below (Figs. 2.14, 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.21, 2.22, 2.23, 2.24, 2.25, 2.26, and 2.27).

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a

b

c

d

Fig. 2.10 (a–d) Different points of view of the endoscopic surgical approach on the ovine model, with particular attention to trainee’s hands, instruments, endoscope position and specimen orientation with respect to the surgeon

2  Surgical Instruments and Preparation of the Specimen Fig. 2.11 Surgical equipment for endoscopic ear surgery training on human specimen and ovine head. (1) Suction tubes, (2) angled dissectors (Thomassin dissectors) of various lengths, (3) round knives, (4) curved needles (also angled hooks can be used), (5) curette, (6) cottonoids, (7) different types of forceps (including forceps to cut the head of the malleus and crimping forceps for the stapes prosthesis loop), (8) sickle knife, (9) myringotomy knife, (10) scissors, (11) micro-­ scissors, and (12) Hartmann forceps

Fig. 2.12 (a, b) Surgical drill used to perform procedures like canalplasty or in stapes surgery approach

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Fig. 2.13  3 mm diameter, 15 cm length endoscopes (Karl Storz, Tuttlingen, Germany). (a) 0° lens endoscope. (b) 45° lens endoscope

Fig. 2.14 (a) Straight suction tubes (different sizes). (b) Curved suction tubes (different lengths)

a

b

2  Surgical Instruments and Preparation of the Specimen Fig. 2.15 (a, b) Sickle knife

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a

Fig. 2.17 (a, b) Round/ curved knives

a

b

b

2  Surgical Instruments and Preparation of the Specimen

Fig. 2.18 Curette

Fig. 2.19 Curved needles (different angles)

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Fig. 2.20  Angled hook

a

b

22 Fig. 2.21 Angled dissectors

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2  Surgical Instruments and Preparation of the Specimen Fig. 2.22 Thomassin dissectors (different lengths)

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24 Fig. 2.23 Micro-­ scissors (different sizes)

a

c

b

d

2  Surgical Instruments and Preparation of the Specimen Fig. 2.24 Scissors

Fig. 2.25  Hartmann or similar forceps

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26 Fig. 2.26 Crimper

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2  Surgical Instruments and Preparation of the Specimen

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Fig. 2.27  Forceps for the head of the malleus

References 1. Presutti L, Marchioni D.  Endoscopic ear surgery. Principles, indications, and techniques. Stuttgart: Thieme; 2015. 2. Alicandri-Ciufelli M, Marchioni D, Pavesi G, Canzano F, Feletti A, Presutti L.  Acquisition of surgical skills for endoscopic ear and lateral skull base surgery: a staged training programme. Acta Otorhinolaryngol Ital. 2018;38(2):151–9. https://doi. org/10.14639/0392-100X-1878. 3. Snyderman C, Kassam A, Carrau R, et al. Acquisition of surgical skills for endonasal skull base surgery: a training program. Laryngoscope. 2007;117:699–705. 4. Scott DJ. Patient safety, competency, and the future of surgical simulation. Simul Healthc. 2006;1(3):164–70. 5. Gorostidi F, Vinckenbosch P, Lambercy K, Sandu K.  Lamb larynx model for training in endoscopic and CO2 laser-assisted surgeries for benign ­ laryngotracheal obstructions. Eur Arch Otorhinolaryngol. 2018 Aug;275(8):2061–9. 6. Isaacson G, Ianacone DC, Soliman AM.  Ex vivo ovine model for suspension microlaryngoscopy training. J Laryngol Otol. 2016 Oct;130(10):939–42. 7. Gocer C, Eryilmaz A, Genc U, Dagli M, Karabulut H, Iriz A. An alternative model for stapedectomy training in residency program: sheep cadaver ear. Eur Arch Otorhinolaryngol. 2007;264(12):1409–12. 8. Cordero A, Del Mar MM, Alonso A, Labatut T. Stapedectomy in sheep: an animal model for surgical training. Otol Neurotol. 2011;32(5):742–7.

9. Schnabl J, Glueckert R, Feuchtner G, et al. Sheep as a large animal model for middle and inner ear implantable hearing devices: a feasibility study in cadavers. Otol Neurotol. 2012;33(3):481–9. 10. Mantokoudis G, Huth ME, Weisstanner C.  Lamb temporal bone as a surgical training model of round window cochlear implant electrode insertion. Otol Neurotol. 2016;37(1):52–6. 11. Seibel VA, Lavinsky L, De Oliveira JA. Morphometric study of the external and middle ear anatomy in sheep: a possible model for ear experiments. Clin Anat. 2006;19(6):503–9. 12. Seibel VA, Lavinsky L, Irion K.  CT-scan sheep and human inner ear morphometric comparison. Braz J Otorhinolaryngol. 2006;72(3):370–6. 13. Anschuetz A, Bonali M, Ghirelli M, Mattioli F, Villari D, Caversaccio M, Presutti L.  An ovine model for exclusive endoscopic ear surgery. JAMA Otolaryngol Head Neck Surg. 2017 Mar 1;143(3):247–52. https:// doi.org/10.1001/jamaoto.2016.3315. 14. Connors RC, Doty JR, Bull DA, May HT, Fullerton DA, Robbins RC.  Effect of work-hour restriction on operative experience in cardiothoracic surgical residency training. J Thorac Cardiovasc Surg. 2009;137(3):710–3. 15. Harris JP, Osborne E. A survey of otologic training in US residency programs. Arch Otolaryngol Head Neck Surg. 1990;116(3):342–4. 16. Ianacone DC, Gnadt BJ, Isaacson G.  Ex vivo ovine model for head and neck surgical simulation. Am J Otolaryngol. 2016;37(3):272–8.

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Comparative Anatomy and Radiology: Human vs. Ovine Model Matteo Fermi, Seiji Kakehata, Matteo Alicandri-­Ciufelli, Marco Bonali, Anna Maria Billi, Francesca Cavalleri, and Abraam Yacoub

3.1

Introduction (Fig. 3.1)

The middle ear cavity is a very small space where important anatomical relationships exist and where different subspaces can be described. Some of its features have recently been re-defined thanks to the endoscope [1–6]. In fact, some of the areas of the middle ear cavity are inaccessible by microscope, especially through the external M. Fermi · M. Alicandri-Ciufelli Department of Otolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy S. Kakehata Department of Otorhinolaryngology, Yamagata University, Faculty of Medicine, Yamagata, Japan M. Bonali (*) Department of Otolaryngology - Head and Neck Surgery, University Hospital of Modena, Modena, Italy A. M. Billi Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy e-mail: [email protected] F. Cavalleri Department of Neurosciences, Neuroradiology unit, University Hospital of Modena, Modena, Italy e-mail: [email protected] A. Yacoub Department of Otolaryngology, Head and Neck Surgery, Inselspital University Hospital and University of Bern, Bern, Switzerland Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Ain Shams University, Cairo, Egypt

auditory canal. These limitations are due to the nature of the microscope, which permits a straight-line vision and is unable to see around corners (Fig. 3.1). On the contrary, the endoscope allows us to “look around the corner” permitting the surgeon to explore almost every space of the middle ear cavity. In addition, angled lenses (i.e., 30°, 45°, 70°) might help to assess even deeper recesses (i.e., type B facial sinus, type B sinus tympani). In this chapter the anatomic details of the ovine model are highlighted and compared to those of the human. A specific knowledge of the ovine model anatomy is required in order to start a training program. The middle ear anatomy of the ovine is quite similar to the human one and is suitable to perform endoscopic surgical procedures. Thanks to the training on endoscopic ear surgery on the ovine model it is possible to obtain adequate skills and become expert enough to start applying endoscopic techniques on patients [7].

3.2

 xternal Auditory Canal E and Tympanic Membrane (Figs. 3.2, 3.3, 3.4, and 3.5)

The external auditory canal in coronal plane is quite horizontal, differently from the human where it has more diagonal orientation (Fig.  3.2). Its diameter is variable and depends on the age of the lamb. We recommend using 6-month-­old (or older) sheeps in order to have a suitable external auditory

© Springer Nature Switzerland AG 2021 M. Bonali et al. (eds.), Comparative Atlas of Endoscopic Ear Surgery, https://doi.org/10.1007/978-3-030-47005-0_3

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Fig. 3.1 Human specimens. Right ear. Comparison between transcanal microscopic view (a) and transcanal endoscopic view (b) of the retro- and hypotympanic regions. Notice that the microscope does not allow exploring properly these areas (black arrow). In particular, the endoscope offers a wide view of the retrotympanum espe-

cially with angled lenses. in incus, s stapes, t stapedial tendon, pr promontory, sst subtympanic sinus, p ponticulus, st sinus tympani, pe pyramidal eminence, fn facial nerve. (From Bonali M et al. The variants of the retro- and hypotympanum: an endoscopic anatomical study. Eur Arch Otorhinolaryngol. 2017;274(5):2141–2148)

Fig. 3.2  CT scan. Coronal view. Right ear. Comparison between human orientation of the external auditory canal (a) and ovine model straight route of the same corridor (b). White arrows indicate the inclination of the external

canal in both radiological images. White asterisk indicates the wide pneumatization of the hypotympanum in the ovine model

canal for using 3  mm e­ndoscope and temporal bone dissection instruments. In some cases a canalplasty is needed to get to the tympanic membrane and to work properly in the middle ear cavity. The tympanic membrane is quite different from the human one. At an otoendoscopic evalu-

ation it is immediately clear that the pars flaccida is more developed than in a human specimen. Moreover, only the superior aspect of the ­tympanic cavity can be seen and even the handle of the malleus is difficult to evaluate without performing a canalplasty to enlarge the

3  Comparative Anatomy and Radiology: Human vs. Ovine Model

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a

Fig. 3.3  CT scan. Coronal view. Right ear. The bulging of the inferior bony aspect of the external auditory canal (black arrow) partially covers the handle of the malleus (white arrow)

external auditory canal inferiorly (Figs. 3.3 and 3.4). Moreover, neither a prominent lateral process of the malleus nor tympanomalleolar ligaments/folds can be seen in the ovine model. When elevating the tympanomeatal flap, it is immediately evident that in the ovine model there is neither a fibrous annulus nor a bony annulus (Fig.  3.5). Thus, the elevation of the tympanomeatal flap should be performed carefully in order to find the right plane between the external auditory canal bone and skin in order to get into the middle ear cleft without breaking the eardrum.

3.3

Ossicular Chain (Figs. 3.6, 3.7, 3.8, 3.9, 3.10, and 3.11)

The ossicular chain is composed by the malleus, the incus, and the stapes. Small differences with the human bones are present.

3.3.1 Malleus The malleus can be divided into three parts: head, neck, and handle. The head of the malleus in the ovine model is flatter than the one in the human, and on the medial facet there is a wide groove for the attachment of the tensor tympani muscle and ten-

b

Fig. 3.4  Right ear. Comparison between human (a) and ovine (b) tympanic membrane visualization through the external auditory canal. Notice that the malleus is clearly visible with its lateral process in humans (black asterisk). On the contrary, it is partially hidden in the ovine due to the bulging of the inferior portion of the external auditory canal. Pars flaccida is also smaller than pars tensa in humans and vice versa in ovine model (black circle). pt pars tensa, pf pars flaccida, u umbus region, ma malleus

don (described below). The articular facet for the incus is located posteriorly, similarly as the human specimen. In the ovine model there is no lateral process, while the anterior is present (Fig. 3.6). The handle of the malleus is much longer in the sheep. In fact, its inferior limit is hardly identifiable during conventional dissections, since the hypotympanic region does not harbor useful structures for endoscopic training. The tympanic membrane is attached to the handle of the malleus and the umbus is located at the end of it (Fig. 3.7).

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Fig. 3.5  Right ear. (a) In humans the fibrous annulus (black arrowhead) should be carefully identified before opening the tympanic cavity mucosa. This step is important in order to avoid breaking in the tympanic membrane

during the elevation of the tympanomeatal flap. (b) In the ovine model the annulus is totally absent (black arrow). tmf tympano-meatal flap, eac-b external auditory canal bone

Fig. 3.6  Right ear. (a, b) Malleus anatomy through an endoscopic transcanal approach in humans. Notice the roundish shape of the head of this ossicle and the presence of the lateral process which is in contact with the tympanic membrane. (c, d) Malleus in ovine model. Lateral (c) and medial (d) aspect. Main differences in comparison

with the humans are the flat malleus head (black asterisk), the long handle (black circle), and the wide groove on the neck for the tensor tympani muscle and tendon (black arrow). Black arrowhead indicates the articular facet for the incudomalleolar joint. in incus, mhl malleus handle, lp lateral process, mh malleus head, s stapes

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Fig. 3.6 (continued)

3.3.2 Incus The shape of the ovine incus is similar to the one in the humans. However, the position of the two processes is inverted (Fig. 3.8). In fact, the ovine incus shows a long process, which is articulated through a posterior incudal ligament to the bony edges of the region where the ear drum attaches, while the short process is attached through a nonossified lenticular process to the head of the stapes. The articular facet is located at the anterior margin of the body of the incus. It joins with the articular facet of the head of the malleus to form the incudomalleolar joint (Fig. 3.9).

3.3.3 Stapes The stapes in the ovine model is very similar to the human one, apart from the size of the bone, which is smaller. The two crurae are thicker and their distance is closer (Fig. 3.10). The stapedial tendon attaches on to the stapes neck. The platina fits the oval window like in the human. The head of the stapes articulates with the lenticular process to form the incudostapedial joint. The stapes lies in the same position as in the human and it is connected with the stapedial tendon, even if in the ovine model there is no pyramidal eminence (Fig. 3.11).

Fig. 3.7  Right ear. Exploration of the pars tensa of the tympanic membrane, usually hidden by inferior portion of the external auditory canal in ovine model. The long handle of the malleus is attached to the tympanic membrane (pars tensa) and it ends at the level of the umbus (white asterisk). pf pars flaccida, pt pars tensa, ma malleus

3.4

Mesotympanum (Figs. 3.12 and 3.13)

The medial wall of the tympanic cavity is characterized by the presence of the promontorium. The Jacobson’s nerve, similarly to the humans, can be identified at the level of the anterior pillar of the round window niche and runs onto the promontorial region towards the area of the tensor tympani

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Fig. 3.8  Right ear. Detail of the incus in the ovine model. The long process is located at the level of the posterior quadrants of the eardrum, close to the projection of the tympanic tract of the facial nerve (facial sinus). The short process articulates with the stapes. On the contrary, in the human the

short process is located at the fossa incudis, close to the facial nerve, while the long process forms the incudo-stapedial joint. (a) Lateral view. (b) Medial view. Black arrowhead indicates the articular facet for the malleus head. lp long process. Black circle indicates the short process

Fig. 3.9  Right ear. (a) Incus anatomy through an endoscopic transcanal approach in humans. Notice the short process articulated with the region of the buttress posteriorly and the long process in contact with the stapes head (black arrowhead). (b) Incus in ovine model. Notice the

inversion of the bony processes of this ossicle (the short process is in contact with the stapes head; black arrowhead). sp short process, lp long process, st stapedial tendon, imj incudomalleolar joint

muscle and the Eustachian tube (Fig.  3.12). The oval window is located like in the human specimens in the posterosuperior mesotympanum, near to the posterior pillar of the round window niche. It is separated from the fossa of the tensor tympani

muscle by an additional ridge of bone (Fig. 3.13). The tensor tympani muscle is thicker in the ovine model than in humans and is similarly attached to the malleus, even if there is neither cochleariform process nor tensor tympani tendon.

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Fig. 3.10  Right ear. Detail of the stapes in the ovine model. The stapes footplate is slightly bended. The crurae and the stapes head are quite similar to human ossicle. sf stapes footplate. Black arrowheads indicate the stapes crurae. Black arrow indicates the stapes head

3.5

Retrotympanum (Figs. 3.14, 3.15, 3.16, and 3.17)

The retrotympanum is a complex area consisting of different spaces lying in the posterior aspect of the tympanic cavity. In the human the pyramidal eminence represents the fulcrum of the retrotympanum. In fact, two bony septations arise from this structure: the chordiculus, extending outward towards the chordal eminence, and the ponticulus, extending inward towards the promontory region, just below the oval window niche. These bony formations (if present) divide the facial sinus from the lateral tympanic sinus and the posterior tympanic sinus from the sinus tympani, respectively. Other bony septations exist. The subiculum (if present) extends among the styloid prominence and the posterior pillar of the round window niche, dividing the superior retrotympanum from the inferior retrotympanum and representing the inferior limit of the sinus tympani and the superior limit of the subtympanic sinus. The finiculus (if present) extends from the anterior pillar of the round window niche to the hypotympanic cellularity and contributes to divide the retrotympanum from the hypotympanum (Fig. 3.14). All of these septations are lacking in the ovine model. First of all, the pyramidal eminence is not devel-

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oped. In fact, the stapedial tendon arises from an area located close to the tympanic tract of the facial nerve without any bony coverage. Thus, none of the bony formations described above are present (Fig. 3.15). On the contrary, the chordal eminence is well represented, even if its position is more caudal than in the human. The chorda tympani enters the tympanic cavity at this point and goes towards the tympanic isthmus, as it does in the human anatomy (Fig. 3.16). The pneumatization of the retrotympanic area is less developed in the ovine model. Indeed, the round window niche is usually hidden at a first glimpse after the elevation of the tympanomeatal flap. Thanks to an adequate canalplasty and atticotomy, it can be seen and studied (Fig. 3.17). Differently from the human anatomy, neither the fustis nor a subcochlear canaliculus can be identified. Moreover, the second portion of the facial nerve is dehiscent in all the ovine specimens.

3.6

Epitympanum (Figs. 3.18, 3.19, 3.20, 3.21, and 3.22)

The epitympanum is one of the more complex areas of the middle ear in the humans. It communicates with the mastoid through the antrum and its superior aspect is usually hidden by the scutum, which is the posterolateral wall of the external auditory canal. In the human the epitympanic diaphragm divides the superior attic from the inferior attic and defines different ventilation routes through the anterior and posterior tympanic isthmus and the mesotympanum (Figs. 3.18 and 3.19). The epitympanic space is easily accessible in the ovine model thanks to the presence of a wider pars flaccida and the absence of the scutum. Thus, after the elevation of the tympanomeatal flap the epitympanum can be totally explored. The superior border of the epitympanum is the tegmen tympani, which does not confine with the middle cranial fossa like in the human, but with a pneumatized aspect of the petrous bone (Fig. 3.20). An additional bone is present at the level of the superior bony tegmen. The incudomalleolar joint is located at this

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Fig. 3.11  Right ear. (a, b) Stapes anatomy through an endoscopic transcanal approach in humans. Notice the long process of the incus articulated with the stapes head and the stapedial tendon attached to the stapes neck. Black arrow indicates the stapes footplate at the level of the oval window niche. (c, d) Stapes in ovine model. Notice the bigger lenticular process and the similar disposition of the

stapedial tendon and stapes footplate (black arrowhead), if compared to human anatomy. The pyramidal eminence is absent in the ovine model. lsc lateral semicircular canal, fn facial nerve, in incus, isj incudostapedial joint, st stapedial tendon, pe pyramidal eminence, sh stapes head, ma malleus, lep lenticular process

level. The short process of the incus is attached to the lateral edge of the bony attachment of the tympanic membrane by a posterior incudal ­ligament (Fig. 3.21). The second portion of the facial nerve, which is dehiscent in its caudal

part, represents the inferior limit of this area and shows a similar pathway to the human by going toward the anterior aspect of the tympanic cavity, medial to the tensor tympani muscle (Fig. 3.22).

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Fig. 3.12 Right ear. (a) Mesotympanum anatomy through an endoscopic transcanal approach in humans. The black asterisk indicates the Jacobson’s nerve. (b) Position and route of the Jacobson’s nerve (black asterisks) in humans after removal of the ossicular chain. (c) Mesotympanum in ovine model. Notice the big promontory bone (basal turn of the cochlea) and the similar position of round and oval window areas and facial nerve if

compared to the mesotympanic area in humans. Black asterisk indicates Jacobson’s nerve. (d) Position and route of the Jacobson’s nerve (black asterisks) in ovine model after ossicular chain removal and tensor tympani muscle reflection. in incus, ma malleus, fn facial nerve, s stapes, cp cochleariform process, pr promontory, rwn round window niche, ow oval window, ttc tensor tympani canal, ac additional bony crest

3.7

model, the protympanum is less developed. The tensor tympani muscle is much thicker than in the humans and attaches to the medial aspect of the head of the malleus without any tendon. Thus, a cochleariform process is not identifiable in the sheep. On the anterior aspect of the promontorium a muscular structure can be identified running from the floor of anterior epitympanic space to the inferior margin of the promontory region, anterior to the round window niche (Fig.  3.23). Its function is not clear and it has no homologous structures in the human tympanic cavity.

Protympanum (Figs. 3.23, 3.24, and 3.25)

The protympanum in humans is located between the mesotympanum posteriorly (the limit is the promontorium) and the anterior epitympanic space superiorly (the limit is the cochleariform process and the tensor fold with the tensor tympani canal). Its relationship with the intrapetrous aspect of the internal carotid artery has to be known in the human, since surgical maneuvers at its level could jeopardize the vessel. In the ovine

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Fig. 3.13  Right ear. (a) Oval window region in human’s anatomy after incus and malleus removal. Notice the relationship between cochleariform process, facial nerve, and stapes. Tensor tympani tendon is already cut. (b) Oval window region in ovine specimen after incus and malleus removal. Black arrow indicates the additional bony crest

that separates the stapes region from the tensor tympani muscle. Notice the thickness of tensor tympani muscle in ovine model. cp cochleariform process, fn facial nerve, ttm tensor tympani muscle, pr promontory, s stapes, st stapedial tendon

Fig. 3.14  Right ear. Human specimens. (a) Pyramidal eminence and retrotympanum. Black line indicates the chordiculus crest, while black dashed line indicates the ponticulus bone. Lateral tympanic sinus and facial sinus lie lateral to the pyramidal eminence; posterior sinus and sinus tympani lie medial to the pyramidal eminence. (b) Pneumatization of the retrotympanic area. Bony crests

and cavities in the retrotympanum. pr promontory, rwr round window region, cp cochleariform process, in incus, s stapes, pe pyramidal eminence, p ponticulus, su subiculum, f finiculus, fn facial nerve, lts lateral tympanic sinus, fs facial sinus, ps posterior sinus, st sinus tympani, lsc lateral semicircular canal, sst sinus subtympanicus, hy hypotympanum

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Fig. 3.15  Right ear. Ovine model. (a) No development of pyramidal eminence is clearly seen after chorda tympani removal. Stapes tendon arises directly close to the facial nerve (black asterisk) and has no bony coverage, just like

the VII nerve. (b) No sinuses or bony crests are present in the retrotympanic portion of the tympanic cavity (black arrowheads). in incus, s stapes, fn facial nerve, st stapedial tendon, pr promontory, rwn round window niche

The tensor tympani muscle is harbored in a cavity of the medial wall of the middle ear just lateral to the second portion of the facial nerve (Fig. 3.24). This cavity is separated by the oval window by a bony ridge (Fig. 3.25).

tant, preventing the surgeon from working at this level through a transcanal endoscopic approach (Fig. 3.28).

3.8

Hypotympanum (Figs. 3.26, 3.27, and 3.28)

In the human, the hypotympanum is a variably pneumatized area of the middle ear located between the finiculus (if present) and the eustachian tube ostium. This region does not ­ have important anatomic features except from the ­jugular bulb, which might be highly positioned or dehiscent and visible through this area, and the Jacobson’s nerve (Fig. 3.26). In the ovine model, the jugular bulb is not visible and under the ­promontory there is a pneumatized area which represents a door for the big hypotympanic region (Fig.  3.27). Looking at the CT scan, the difference between the human and the ovine model is quite evident. Indeed, the pneumatization of the hypotympanic area in the ovine model is impor-

3.9

Facial Nerve (Figs. 3.29, 3.30, 3.31, and 3.32)

The facial nerve can be divided into two portions in the tympanic cavity in the humans (precochleariform and postcochleariform tract). The intratympanic tract of VII c.n. is usually covered by the bony Fallopian canal. In the ovine model the cochleariform process is absent and after the elevation of the tympanomeatal flap the tympanic tract of the facial nerve can be immediately identified superiorly to the oval window. Its bony canal is almost always incomplete and doesn’t cover the nerve (Fig. 3.29). At the level of the oval window the facial nerve bends toward the retrotympanic region (second genu) being in contact with the stapedial tendon (and most likely with the stapedial muscle, which is not easily identifiable) and it runs inferiorly to exit from the skull base in a position located behind the external auditory canal and

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Fig. 3.16  Right ear. (a, b) Chorda tympani anatomy through an endoscopic transcanal approach in humans. Notice the route of this nerve (black asterisk) from the chordal eminence at the level of the posterior wall of the bony external auditory canal to the isthmus region between incus and malleus (black arrowhead). (c, d) Chorda tympani in ovine model. The chordal eminence

hypotympanic region (Figs. 3.30 and 3.31). During its course within this region the chorda tympani emergence can be identified. The chorda tympani enters the tympanic cavity from a bony formation, known as chordal eminence, to pass medial to the neck of the malleus, like in the human. At the level of the oval window the facial nerve runs back in an anterosuperior direction to reach the fossa of the tensor tympani muscle, passing medial to the muscle like in humans, and bending towards the intralabyrinthine portion (first genu) (Fig. 3.32). Here it is where the Fallopian canal is narrower, similarly to the human.

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can be seen clearly but the position of the chorda tympani (black asterisk) is more caudal than in the human and goes toward the isthmus region (black arrowhead), passing below the incus. in incus, ma malleus, s stapes, st stapedial tendon, fn facial nerve, ce chordal eminence, pr promontory, eac-b external auditory canal bone

3.10 I nternal Auditory Canal (Figs. 3.33, 3.34, and 3.35) The fundus of the internal auditory canal is located at the same position as in the human. The skeletonization of the cochleovestibular bone at the edge between the cochlear apparatus and the vestibular apparatus permits to identify the dura of the internal auditory canal (Fig.  3.33). The identification of the cochlear nerve is possible after the skeletonization of the cochlea at the modiolar area (Fig.  3.34). The

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Fig. 3.17  Right ear. (a, b) Round window region visualization through an endoscopic transcanal approach in humans. The round window niche region can be easily seen without the need for canalplasty (the tympanomeatal flap elevation is usually enough). (c, d) Round window region in ovine model. Figure (c) shows a prominence of bone of the posterior wall of the external auditory canal that hides the round window region (black arrowhead)

after tympanomeatal flap elevation. Figure (d) shows the clear exposition of the round window niche after posteroinferior canalplasty and removal of chorda tympani. in incus, ma malleus, eac-b external auditory canal bone, j Jacobson’s nerve, rwn round window niche, fn facial nerve, oc ossicular chain, ct chorda tympani, pr promontory, ttc tensor tympani canal

medial wall of the vestibule represents a portion of the fundus of the internal auditory canal. The spherical recess can be identified at this level. This is where the inferior vestibular nerve fibers enter to reach the saccule. The facial

nerve is located more anteriorly and more ­superiorly with respect to those nerves, in continuity with the intralabyrinthine portion described above, differently from humans (Fig. 3.35).

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Fig. 3.18  Right ear. Drawings representing the “epitympanic diaphragm” in humans. (a) Frontal endoscopic view through the external auditory canal. (b) Axial view from upper to lower portion of the tympanic cavity. s stapes, fn facial nerve, cp cochleariform process, ma malleus, in incus, aes anterior epitympanic space, amf anterior mal-

leolar fold, pes posterior epitympanic space, pil posterior incudal ligaments, tf tensor fold, mlf lateral malleal fold, imlf lateral incudomalleal fold, is isthmus, pe pyramidal eminence, dr ear drum. (From Presutti L, Marchioni D.  Endoscopic Ear Surgery. Principles, Indications, and Techniques. Thieme. Chapter 5. p. 69)

Fig. 3.19  Right ear. (a) Human specimen. Epitympanic area after ligaments, folds, and scutum removal. Black line indicates the incudo-malleolar lateral fold that separates superior from inferior lateral attic. Black arrow indicates the region of the medial attic, behind the ossicular chain. (b) Malleolar ligament folds and membranous folds forming the complete epitympanic diaphragm. The two major middle ear ventilation pathways of epitympanic compartments (blue arrow) and Prussak’s space (orange arrow) are represented. tf tensor fold, fn facial

nerve, s stapes, in incus, ma malleus, as anterior spine, ps posterior spine, prs (or Pr Sp) Prussak’s space, et Eustachian tube, aes anterior epitympanic space, imlf lateral incudomalleal fold, mlf lateral malleal ligamental fold, cp cochleariform process, plm posterior malleal ligamental fold, sup lat at superior lateral attic, inf lat at inferior lateral attic, ct chorda tympani. (From Marchioni D et  al. Lateral endoscopic approach to epitympanic diaphragm and Prussak’s space: a dissection study. Surg Radiol Anat. 2010;32:843–852)

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Fig. 3.20  CT scan. Coronal view. Right ear. Comparison between human bony tegmen tympani (a), which is contiguous superiorly to the middle cranial fossa, and the pneumatization of the petrous bone, that creates a space (b) between middle cranial fossa and tympanic cavity in ovine model. Black dashed line indicates the bony tegmen

in humans (a) and the pneumatization of the temporal bone in the ovine model. White arrows indicate the external auditory canal. White asterisk indicates the cochlea. Black circle indicates the ossicular chain. mcf middle cranial fossa, tc tympanic cavity, hy hypotympanum

Fig. 3.21  Right ear. Ovine model. (a, b) Epitympanic region. Notice the absence of mucosal folds and ligaments and the presence of an additional bone just below the bony tegmen. Incus is attached to the posterior bony portion of

the tympanic cavity through a posterior ligament (black asterisk). teg tegmen, ab additional bone, in incus, ma malleus, s stapes, tmf tympanomeatal flap, fn facial nerve

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Fig. 3.22  Right ear. (a) Facial nerve course in humans (black dashed lines). Notice the pneumatization of the attic region. (b) Facial nerve (tympanic tract) in ovine model (black dashed lines). The nerve is always uncovered by bone in the ovine, but the route is similar to that of

humans, going towards the tensor timpani muscle. teg tegmen, cp cochleariform process, ttc tensor tympani canal, lsc lateral semicircular canal, ow oval window, pr promontory, ab additional bone, ttm tensor tympani muscle

Fig. 3.23  Right ear. (a, b) Protympanic region visualization through an endoscopic transcanal approach in humans. From upper to lower position is possible to visualize the tensor fold, the supratubal recess, the Eustachian tube orifice (black arrowhead) and the area of bone covering the internal carotid artery. After removal of some bone, the carotid artery is clearly seen in its relationship with the tensor tympani muscle. Black circle indicates the tensor tympani tendon. (c, d) Protympanum in ovine

model. Figure (c) shows the absence of cochleariform process and tensor tympani tendon in the sheep (after incus removal). Figure (d) shows an additional muscle attached to the anterior portion of the promontory region (black dashed line). tf tensor fold, sr supratubal recess, cp cochleariform process, ic internal carotid artery, ma malleus, in incus, pr promontory, ttm tensor tympani muscle, s stapes, j Jacobson’s nerve, am additional muscle, hy hypotympanum

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Fig. 3.23 (continued)

Fig. 3.24  CT scan. Coronal view. Right ear. Comparison between human (a) and ovine (b) relationship between tensor tympani muscle (white arrowhead) and facial nerve second tract (black arrowhead). Notice the major thick-

ness of the ovine muscle that attaches to the malleus bone (black circle). White asterisk indicates cochlear turns. mcf middle cranial fossa, hy hypotympanum, eac external auditory canal

3.11 Take Home Messages

It is mandatory to understand the anatomy of the ovine model and its differences with respect to the human in order to carry out anatomicallyoriented dissections and to perform all the surgical procedures described in the other chapters as best as possible.

The anatomy of the ovine model looks like the human one for most of the structures of the middle and inner ear. This aspect can be exploited to improve anatomic basics and surgical skills in endoscopic ear surgery.

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Fig. 3.25  Right ear. Ovine model. Notice the thickness of the tensor tympani muscle and the absence of a tensor tympani tendon. Facial nerve runs medial to the tensor tympani muscle on the medial wall of the tympanic cavity, and it is separated from this muscular structure by a bony crest. This ridge of bone is bounded superiorly by the roof of the tympanic cavity and inferiorly it ends on the superior margin of the promontory, anterior to the oval window area. bc bony crest, ttm tensor tympani muscle, ow oval window, rwn round window niche, fn facial nerve, pr promontory, hy hypotympanum, am additional muscle

Fig. 3.26  Right ear. Human anatomy. (a) The hypotympanic region is delimited posteriorly by the finiculus bone, that originates from the anterior pillar of the round window niche. Jacobson’s nerve runs over this bony ridge. (b) Hypotympanic region in case of a high jugular bulb.

Notice the absence of finiculus bone in this case. j Jacobson’s nerve, hy hypotympanum, f finiculus bone, rwn round window niche, rw round window, pr promontory, ic internal carotid artery, et Eustachian’s tube orifice

Fig. 3.27  Right ear. Ovine anatomy. (a) The hypotympanum is represented by a pneumatized cavity. Finiculus bone is always absent (black asterisk) and the jugular bulb is not present in this area. (b) Detail of the hypotympanic

region. Notice the absence of anatomical structures under the promontory region. j Jacobson’s nerve, hy hypotympanum, pr promontory, rw round window

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a

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b

Fig. 3.28  CT scan. Coronal view. Right ear. Comparison between human (a) and ovine (b) hypotympanic region. Notice the big difference in pneumatization of this area

between the two models. eac external auditory canal, hy hypotympanum. White asterisk indicates the cochlea. Black circle indicates the malleus bone

Fig. 3.29  Right ear. (a) Schematic drawing of the tympanic facial nerve anatomy in humans. The black vertical line separates the two portions of the tympanic segment of the facial nerve with respect to the cochleariform process after removal of the ossicular chain. (b) Endoscopic anatomy of the facial nerve second tract. Black vertical line divides the pre- from the postcochleariform segment of the nerve. (c, d) Ovine model. The facial nerve is clearly visible after tympanomeatal flap elevation and there’s no bony canal covering the nerve. teg tegmen, lsc lateral

semicircular canal, ttc tensor tympani canal, et eustachian tube, cp cochleariform process, pr promontory, jb jugular bulb, f finiculus, su subiculum, p ponticulus, pe pyramidal eminence, pre cochl precochleariform segment of VII c.n., post cochl postcochleariform segment of VII c.n., gg geniculate ganglion, s stapes, st stapedial tendon, aes anterior epitympanic space, pes posterior epitympanic space, in incus, ma malleus, ct chorda tympani, rwn round window niche, fn facial nerve

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Fig. 3.29 (continued)

Fig. 3.30  Right ear. (a) Human anatomy. The facial nerve runs over the oval window region and the stapedial tendon emerges from pyramidal eminence. (b) Ovine anatomy. The stapedial muscle is not clearly identifiable. The course of the nerve around the stapes is similar to that

of humans. lsc lateral semicircular canal, cp cochleariform process, pr promontory, gg geniculate ganglion, s stapes, st stapedial tendon, in incus, ma malleus, ct chorda tympani, rwn round window niche, fn facial nerve

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Fig. 3.31  CT scan. Axial view. Right ear. Comparison between human (a) and ovine (b) facial nerve (third tract). Notice the course of the nerve (white arrowhead) inside the mastoid bone in humans; the same segment (white

asterisks) runs horizontally and posteriorly to the external auditory canal in ovine model due to the absence of the mastoid bone in the sheep. hy hypotympanum, ma mastoid bone

Fig. 3.32  Right ear. (a) Human anatomy. After removal of the ossicular chain (incus and malleus) and cochleariform process, the geniculate ganglion is clearly visible. (b) Ovine anatomy. The tensor tympani muscle is reverted and the ossicles are removed to show the course of the second tract of the facial nerve and the geniculate gan-

glion area. Notice the narrow bony space where the nerve bends toward the intralabyrinthine portion (first genu), similarly to the humans. teg tegmen, lsc lateral semicircular canal, fn facial nerve, gg geniculate ganglion, s stapes, cp cochleariform process, ow oval window, ttc tensor tympani canal, pr promontory

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a

b

c

d

Fig. 3.33  Right ear. (a, b) Projection of the internal auditory canal (black circle) through an endoscopic transcanal approach in humans. Notice the position of the internal auditory canal between the vestibule and the cochlear turns (a) and the exposition of the dura mater after some bone removal (b). (c, d) Internal auditory canal in ovine model. Figure (c) shows the similar disposition of the

inner ear, if compared to humans. Notice the same projection of the internal auditory canal (black circle, a–c) and the dural exposition after bone drilling (b–d). ttm tensor tympani muscle, gg geniculate ganglion, fn facial nerve, cp cochleariform process, cho cochlea, cho* cochlea (basal turn), cho** cochlea (middle and apical turns), ve vestibule, iac-d internal auditory canal dura

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Fig. 3.34  Right ear. (a) Identification of cochlear nerve and vestibular nerve at the level of internal auditory canal (black asterisk) through an endoscopic transcanal approach in humans. Notice the direction of the cochlear nerve toward the cochlear turns. Superior and inferior vestibular nerves are not clearly separate in this dissection

specimen. (b) Internal auditory canal (black asterisk) in ovine model. Cochlear nerve and vestibular nerve are in a similar position if compared to human specimens. gg geniculate ganglion, fn facial nerve, cho cochlea, cn cochlear nerve, vn vestibular nerve

Fig. 3.35  Right ear. (a) Skeletonization of the facial nerve (first and second tract) through an endoscopic transcanal approach in humans. Notice the narrow angle between the two segments at the level of the geniculate ganglion. (b) Facial nerve in ovine model. The facial

nerve is located more anteriorly and the angle between the first and second segment is wider than humans. fn** facial nerve (second tract), fn* facial nerve (first tract), gg geniculate ganglion, iac internal auditory canal

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References 1. Bonali M, Anschuetz L, Fermi M, et  al. The variants of the retro- and hypotympanum: an endoscopic anatomical study. Eur Arch Otorhinolaryngol. 2017;274(5): 2141–8. https://doi.org/10.1007/s00405-017-4492-0. 2. Alicandri-Ciufelli M, Fermi M, Bonali M, et  al. Facial sinus endoscopic evaluation, radiologic assessment, and classification: facial sinus endoscopic study. Laryngoscope. 2018;128:2397. https://doi.org/ 10.1002/lary.27135. 3. Anschuetz L, Alicandri-Ciufelli M, Bonali M, et  al. Novel surgical and radiologic classification of the subtympanic sinus: implications for endoscopic ear surgery. Otolaryngol Head Neck Surg. 2018;159:1037–42. https://doi.org/10.1177/01945998 18787180.

M. Fermi et al. 4. Marchioni D, Alicandri-Ciufelli M, Piccinini A, Genovese E, Presutti L.  Inferior retrotympanum revisited: an endoscopic anatomic study. Laryngoscope. 2010;120(9):1880–6. https://doi.org/ 10.1002/lary.20995. 5. Marchioni D, Soloperto D, Colleselli E, Tatti MF, Patel N, Jufas N.  Round window chamber and fustis: endoscopic anatomy and surgical implications. Surg Radiol Anat. 2016;38(9):1013–9. https://doi. org/10.1007/s00276-016-1662-5. 6. Marchioni D, Alicandri-Ciufelli M, Grammatica A, Mattioli F, Presutti L. Pyramidal eminence and subpyramidal space: an endoscopic anatomical study. Laryngoscope. 2010;120(3):557–64. https://doi. org/10.1002/lary.20748. 7. Anschuetz L, Bonali M, Ghirelli M, et  al. An ovine model for exclusive endoscopic ear surgery. JAMA Otolaryngol Head Neck Surg. 2017;143(3):247. https://doi.org/10.1001/jamaoto.2016.3315.

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Myringotomy and Transtympanic Ventilation Tube Positioning Domenico Villari, Adrian James, Marco Bonali, Francesco Maccarrone, Andrea Martone, and Livio Presutti

4.1

Introduction

Myringotomy and ventilation tube (also called grommet) placement are widespread procedures usually performed for refractory middle ear effusion with persistent conductive hearing loss. The technique was first described by Politzer in 1868 for the treatment of “otitis media with effusion” and popularized by Armstrong in 1954 [1]. The role of a transtympanic tube is to maintain the tympanic cavity opened and guarantee an additional aeration of the middle ear. The primary underlying issue for all of the indications is eustachian tube dysfunction (ETD). ETD is often a complication of upper respiratory tract infections especially in children that are predisposed to ETD for multiple reasons: the small caliber of their eustachian tube, its horizontal Electronic Supplementary Material The online version of this chapter (https://doi.org/10.1007/978-3-030-470050_4) contains supplementary material, which is available to authorized users. The videos can be accessed by scanning the related images with the SN More Media App. D. Villari (*) · F. Maccarrone A. Martone Department of Otolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy A. James Department of Otolaryngology, Head and Neck Surgery, Hospital for Sick Children, University of Toronto, Toronto, ON, Canada M. Bonali · L. Presutti Department of Otolaryngology - Head and Neck Surgery, University Hospital of Modena, Modena, Italy

direction, and their immature immune systems [2]. The goal of tympanostomy tube placement is not to cure the cause of ETD but to allow aeration of the middle ear until the patients’ eustachian tube starts to work properly. Specific subpopulations of children are at higher risk of eustachian tube dysfunction, including those with cleft palate, Down syndrome, and other children with craniofacial abnormalities [3–5]. Although tympanostomy tube placement is considered to be a simple, low-­risk intervention and it’s performed very commonly, there can be significant complications associated with the procedure. Adverse effects associated with tympanostomy tube insertion include those related to anesthesia and its complications (laryngospasm, bronchospasm), as well as tube-related sequelae such as recurrent (7%) or persistent (16– 26%) otorrhea, blockage of the tube lumen (7%), granulation tissue (4%), premature extrusion of the tube (4%), tympanostomy tube displacement into the middle ear (0.5%), and persistent perforation of the tympanic membrane (1–6%) [6]. When making clinical decisions, the advantages of tube insertion should be balanced with the risks of complications. Endoscopic myringotomy and ventilation tube positioning can be easier, if compared to the microscopic transcanal procedure, in case of tortuous external auditory canal. Moreover, the enhanced visualization might allow us to identify vascular abnormalities medial to the tympanic membrane (i.e., high positioned and/or dehiscent jugular bulb, aberrant internal carotid artery) avoiding critical complications.

© Springer Nature Switzerland AG 2021 M. Bonali et al. (eds.), Comparative Atlas of Endoscopic Ear Surgery, https://doi.org/10.1007/978-3-030-47005-0_4

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4.2

Indications

–– Persistent serous otitis media or otitis media with effusion, with hearing impairment or unresponsive to medical treatments. –– Recurrent acute otitis media with middle ear effusion. –– Recurrent barotrauma. –– Complications of acute otitis media (i.e., mastoiditis).

4.3

 urgical Steps in Human S Procedure

General anesthesia is used for children, while local anesthesia may be employed with adults. Topical anesthetic spray (e.g., xylocaine) can be applied inside the external auditory canal and in contact with the tympanic membrane 10  min before the procedure.

4.3.1 Patient Positioning and Surgical Setting (Fig. 4.1) The patient lay supine with slightly extended and rotated head to the contralateral side. The surgeon holds a 4 mm diameter, 15 cm length (or longer), 0°

Fig. 4.1  The patient is positioned supine with rotated head. The video equipment is positioned just beyond the patient’s head. The surgeon and the assistants look at the

angled endoscope (Karl Storz, Tuttlingen, Germany, or similar) by the left hand, and the operative instruments by the right hand (for right-handed surgeons). In case of a narrow external auditory canal a 3 mm diameter endoscope can be used. The endoscope is connected to AIDA three-chip high-resolution monitor and camera system (Karl Storz, Tuttlingen, Germany, or similar).

4.3.1.1 Step 1: Exploration of the Tympanic Membrane and Incision (Fig. 4.2) A myringotomy knife is carefully advanced toward the tympanic membrane for the preferred myringotomy stab incision. The myringotomy radial incision is made at the antero-inferior tympanic membrane quadrant. Incisions in the posterosuperior quadrant are avoided as they could injure the ossicular chain or the chorda tympani. The incision must be large enough to accommodate a ventilation tube. Sometimes an external ear canal anterior bulging can reduce the space and the procedure is more difficult, especially in case of accidental injury of the skin with consequent bleeding (Fig. 4.2). 4.3.1.2 Step 2: Suction (Fig. 4.3) The middle ear effusion may be aspirated with a small suction tube before inserting the grommet (Fig. 4.3).

same monitor and they can appreciate the procedure from an identical point of view

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a

b

c

d

Fig. 4.2  Case #1. Right ear. (a) Exploration of the tympanic membrane through a transcanal approach. Notice the anterior bulging of the canal, with a worse view of the anterior tympanic membrane compartments. (b) The myringotomy knife is introduced in the canal paying attention to preserve the skin. Black line indicates the area of incision that not involves

a

Fig. 4.3  Case #1. Right ear. (a) The suction tube is inserted inside the external auditory canal at the level of the previous tympanic incision and removes the middle ear effusion. (b)

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the annulus or the umbus region. (c, d) The knife is introduced through the incision and the hole is progressively enlarged by moving the tip of the knife in anterior and posterior direction. The asterisk indicates some blood over the anterior bulging, due to an accidental injury of the skin. ma malleus (lateral process), u umbus, ta tympanic anulus

b

After the removal of the effusion a hole in the antero-inferior quadrant of the tympanic membrane is clearly visible. This perforation represents the site for grommet insertion

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4.3.1.3 Step 3: Ventilation Tube Positioning and Insertion (Figs. 4.4 and 4.5) For long-term middle ear dysventilation a long-­ term T-tube can be used, and it remains in place for up to 3 years. The flanges of the T-tube are grasped with Hartmann forceps. The flanges are then trimmed so that the ends are pointed; this facilitates insertion of the tube through the myringotomy opening. The T-Tube is grasped with fine alligator forceps and the pointed end of the flange is inserted through the myringotomy incision (Fig. 4.4). In case of a short-term straight grommet positioning (i.e., Donaldson fluoroplastic type or Shepard type), the ventilation tube is picked up with Hartmann forceps and introduced into the ear canal using the right hand (for right-handed

surgeons). The tube is placed on the tympanic membrane adjacent to the myringotomy opening. Using a 1.5 mm, 45° (or 90°) hook the inner flange is rotated through the myringotomy incision so that the tube straddles the tympanic membrane (Fig. 4.5).

4.4

• During the introduction of the myringotomy knife inside the external auditory canal, the scalpel should be slipped along the anterior wall of the canal, parallel to the skin, for the right ear, and along the posterior wall of the canal, for the left ear (for right-handed surgeons, and contrariwise for left-handed surgeons).

a

b

c

d

Fig. 4.4  Case #1. Right ear. (a) A long-term T-tube grommet is introduced inside the external auditory canal with alligator forceps. (b, c) The flanges of the T-tube are inserted simultaneously through the eardrum perforation

Hints and Pitfalls (Human)

(black arrow). Sometimes an angled hook can be used to push the flanges inside the middle ear cavity (one by one). (d) Final view of the grommet after correct positioning

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Fig. 4.5  Case #2. Right ear. (a) A short-term grommet is positioned on the tympanic membrane just over the eardrum perforation. (b, c) An angled hook (45° or 90°) or a curved needle is used to gently push the inner flange of the

grommet slantwise inside the tympanic cavity through the hole previously created. (d) Final view of the grommet after correct positioning

• The incision should be made at the antero-­ inferior quadrant to avoid damaging the ossicular chain or the chorda tympani, and it should be done in between the tympanic annulus and the umbus without touching these two structures. • Great care should be taken to avoid injuring eventual high position jugular bulb or overriding internal carotid artery. • Middle ear effusion should be removed with the suction tube, avoiding closing the valve of the instrument to preserve the tympanic membrane integrity.

4.5

 urgical Steps on Ovine S Model

4.5.1 Surgical Instrumentations (Figs. 4.6, 4.7, and 4.8) A 3 mm (or 4 mm) diameter, 15 cm length (or longer), 0° endoscope should be sufficient to perform this procedure. The instruments set for the myringotomy and transtympanic tube positioning on ovine model is illustrated in Fig. 4.6. Figures 4.7 and 4.8 illustrate the dissection lab and an overview about the preparation of the specimen.

58 Fig. 4.6  Instruments set for myringotomy and grommet insertion on ovine model. First line, from left to right: myringotomy knife, micro-scissors, Thomassin dissector, sickle knife. Second line (from left to right): suction tubes (various sizes), Hartmann forceps, curved needles (also angled hooks can be used)

Fig. 4.7 Dissection table including the ovine’s head, surgical instruments, endoscopic optics, the AIDA three-chip high-­ resolution monitor and camera system (Karl Storz, Tuttlingen, Germany, or similar)

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c

Fig. 4.8  Trainee’s hands position in case of a not decorticated sheep’s head (a, b) and in case of a completely degloved sheep’s head (c). Notice the orientation of the nose of the sheep superiorly (from 12 to 2 o’clock) to perform the dissection in a surgical position. In case (a, b)

two tension sutures through the cartilaginous part of the external auditory canal are placed: the first antero-superiorly and the second antero-inferiorly, and they’re fixed on the skin to enlarge the lateral portion of the canal

Fig. 4.9  (Video 4.1) Myringotomy and grommet insertion. The procedure of grommet insertion is explained. First step is represented by the myringotomy at the level of the pars flaccida of the tympanic membrane. Then,

different types of grommets are showed (straight ones and T-tube), focusing on the specific gestures to insert the ventilation tubes under endoscopic view (https://doi. org/10.1007/000-4a)

4.5.2 Surgical Steps (Fig. 4.9: Video 4.1)

chain are identified, especially the neck and the handle of the malleus (Figs. 4.10 and 4.11). Note that, differently from the human specimen, the pars flaccida is much more developed in the ovine model. The incision can be made posterosuperiorly to the malleus in order to avoid touching the ossicular chain, and it can be performed by means of a myringotomy knife

4.5.2.1 Step 1: Incision (Figs. 4.10, 4.11, 4.12, 4.13, 4.14, and 4.15) The transcanal endoscopic approach is performed with a 0° endoscope. The tympanic membrane and the landmarks of the ossicular

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a

b

Fig. 4.10  Right ear. Endoscopic transcanal exploration of the tympanic membrane. (a) The pars flaccida is very well developed and the malleus is clearly visible. Sometimes the posteroinferior wall of the external auditory canal can

a

b

Fig. 4.11  Right ear. Endoscopic view of the inferior portion of the tympanic membrane. (a, b) The pars tensa is not indicated for the myringotomy due to its position. The malleus

a

be prominent, thus reducing the working space. (b) The pars tensa of the tympanic membrane is less developed. eac-s posterior external auditory canal skin, pf pars flaccida, ma malleus, pt pars tensa

b

Fig. 4.12  Right ear. (a) The myringotomy knife is introduced in the EAC, paying attention to preserve the skin of the canal. (b) The incision is made in the middle of the pars flaccida (black line), perpendicular to the major axis

has a long handle, which is attached to the inferior–anterior floor of the tympanic cavity. pf pars flaccida, pt pars tensa, ma malleus (lateral process), * malleus (long process)

c

of the long process of the malleus. (c) Detail of the tip of the knife and the correct site of incision. pf pars flaccida, ma malleus

4  Myringotomy and Transtympanic Ventilation Tube Positioning Fig. 4.13  Right ear. (a, b) Due to the high elasticity of the pars flaccida in ovine model, it is advisable to move the tip of the knife anteriorly and posteriorly, once the incision has been done, to create an adequate hole. (c, d) The myringotomy is created (black arrow) and the hole is visible (black circle) over the lateral process of the malleus. pf pars flaccida, ma malleus

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Fig. 4.14  Right ear. (a, b) Micro-scissors are introduced through the perforation and used to enlarge the hole previously created. (c) The perforation is visible at the end of the procedure

(Figs.  4.12 and 4.13). Once the myringotomy hole has been performed, it is recommended to enlarge it (depending on the size of the ventilation tube) with micro-scissors, Thomassin dissector or a sickle knife (Figs. 4.14 and 4.15).

4.5.2.2 Step 2: Suction (Fig. 4.16) A small suction tube can be used to suck some exudate out of the tympanic cavity to simulate the suction of the effusion in case of otitis media with effusion (Fig.  4.16). Since the tympanic

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Fig. 4.16  Right ear. (a) Suction tube is positioned at the level of the perforation to simulate the suction of middle ear effusion. (b, c) The thin edges of the perforation are gently touched with the suction tube, avoiding closing the

valve to preserve the membrane (black arrow indicates the edges of the perforation). (d) The myringotomy hole is finally created and clean (black circle)

4  Myringotomy and Transtympanic Ventilation Tube Positioning

membrane at this level is very thin, utmost care has to be taken to avoid sucking the edges of the myringotomy. Avoiding closing the valve of the suction tube might be an effective choice.

and put into the external auditory canal. Then, under endoscopic guide, it can be advanced through the canal until the tympanic membrane is reached (Fig. 4.17). Since the tympanic membrane at this level is quite elastic, the positioning of this ventilation tube might be more demanding. The insertion of this kind of tube can be performed by pushing the medial part of the tube on to the myringotomy in order to medialize the membrane and favorize the complete insertion (Fig.  4.18). During this procedure traumatisms of the ossicular chain must be avoided. The correct position of the ventilation tube can be checked and adjusted with a micro-

4.5.2.3 Step 3: Ventilation Tube Positioning (Figs. 4.17, 4.18, 4.19, 4.20, 4.21, 4.22, 4.23, 4.24, 4.25, 4.26, and 4.27) The insertion of the ventilation tube depends on the size and the shape of the grommet. In case of availability of traditional short-term ventilation tubes, such as the Donaldson type or the Shepard type, it can be grabbed with Hartmann forceps Fig. 4.17  Case# 1. Right ear. (a, b) The short-term grommet (Donaldson type) is introduced inside the external auditory canal with the aim of Hartmann forceps

a

a

Fig. 4.18  Case #1. Right ear. (a) The grommet is pushed inside the perforation with the forceps. Due to the high elasticity of the TM, the force that has to be applied to correctly push the grommet is higher than in humans. (b)

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b

b

The transtympanic ventilation tube is correctly visualized through the tympanic membrane. pf pars flaccida, ma malleus

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a

b

c

Fig. 4.19  Case #1. Right ear. (a–c) Suction tube and a needle (or a micro-hook) are used to clean and check the correct positioning of the grommet. pf pars flaccida, ma malleus, pt pars tensa Fig. 4.20  Case #2. Right ear. (a) The grommet is pushed medially in the external auditory canal with a micro-hook or a needle. (b) The same instruments can be used to insert the medial aspect of the ventilation tube through the eardrum starting from the posterior edge of the myringotomy hole. (c, d) Final view of the grommet correctly positioned. pf pars flaccida, ma malleus

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e

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Fig. 4.21  Case #3. Right ear. (a, b) The titanium grommet is inserted inside the external auditory canal with Hartmann forceps and put just near the perforation (black arrow). (c, d) A micro-hook or a needle is used to push the

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g

grommet through the perforation. (e–g) The titanium grommet is correctly placed through the pars flaccida and a small needle or hook is used to check the stability of the insertion. pf pars flaccida, ma malleus, pt pars tensa

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a

b

c

d

Fig. 4.22  Case #4. Right ear. (a–d) External view of the trainee’s hands during T-tube insertion in the external auditory canal

hook or a needle (Fig. 4.19). Another option is to use a hook or a needle for pushing the tube medially until the membrane is reached and insert the medial aspect of the tube starting from the posterior edge of the myringotomy hole (Fig.  4.20). The gestures are the same even in

case of ventilation tube made by different materials (i.e., titanium) (Fig. 4.21). In case of availability of a traditional longterm T-tube, it has to be grabbed with Hartmann forceps at the medial end, where the two small tube arms are joined together (Figs.  4.22 and

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b

Fig. 4.23  Case #4 Right ear. (a, b) The long-term T-tube has to be grabbed with Hartmann forceps at the medial end. The two small tube arms have to be joined together

a

b

c

d

Fig. 4.24  Case #4. Right ear. (a) The T-tube is gently introduced inside the external auditory canal. (b, c) During the procedure of T-tube positioning through the hole previously created (black arrow, fig. a), it’s important

to avoid to traumatize the ossicular chain and to enlarge the myringotomy hole. (d) The T-tube is correctly placed through the pars flaccida. pf pars flaccida

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a

b

Fig. 4.25  Case #4. Right ear. (a) The small tube arm is clearly visible inside the tympanic cavity and it lies over the short process of the malleus. (b, c) The correct posi-

c

tioning of the T-tube is checked with a needle or a small hook. pf pars flaccida, ma malleus, pt pars tensa

a

b

c

d

Fig. 4.26  Case #5. Right ear. (a–c) The T-tube is progressively pushed inside the perforation with alligator forceps. (d) One of the small medial arms of the T-tube is extruded from the tympanic cavity (black arrow)

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a

b

c

d

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Fig. 4.27  Case #5. Right ear. (a) The T-tube is not correctly in place inside the tympanic cavity. (b–d) With the aim of a micro-hook or a needle the small arm of the ven-

tilation tube is gently pushed through the perforation to obtain a good final positioning of the T-tube

4.23). The T-tube is then brought close to the tympanic membrane and gently inserted, avoiding traumatizing the ossicular chain and enlarging the myringotomy hole, if possible. The correct position of the ventilation tube can be checked and adjusted with a micro-hook (Figs. 4.24 and 4.25). Sometimes during the positioning of this ventilation tube one of the short arms or both might extrude from the tympanic cavity. It is a good exercise to try to put them back at its original position with a micro-hook or a needle (one by one) (Figs. 4.26 and 4.27).

4.5.2.4 Step 4: Ventilation Tube Removal (Fig. 4.28) Once the ventilation tube has been placed and its position has been checked, it can be removed by means of Hartmann forceps. In case of shortterm ventilation tube, like the Donaldson type, there usually is a small tip that can be grabbed with the instrument in order to pull it back in the external auditory canal (Fig. 4.28). This maneuver has to be performed carefully due to the elasticity of the membrane at this level in the ovine specimen.

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a

b

c

Fig. 4.28  Right ear. (a–c) Ventilation tube removal. Notice the high elasticity of the pars flaccida during the procedure. The grommet removal can be done with alligator forceps

4.6

Hints and Pitfalls (Ovine)

• The endoscope might be held on to the superior aspect of the external auditory canal in order to have more space to work on the posterior quadrant of the membrane to perform the myringotomy and the positioning of the ventilation tube. • The incision of the pars flaccida with the myringotomy knife is crucial and it should be done not so close to the lateral process of the malleus in order to avoid ossicular chain disarticulation. It is advisable to move the tip of the knife anteriorly and posteriorly, and not superiorly and inferiorly, once the incision has been done, to create an adequate hole without damaging the surrounding structures. • The myringotomy hole should be often enlarged with various instruments, such as micro-scissors or sickle knife, to avoid destabilizing the ossicular chain during insertion/ extrusion maneuvers. • The tympanic membrane at this level is mostly pars flaccida. Thus, the elasticity of the ­eardrum has to be considered while inserting and removing the ventilation tube. It is important to avoid rough movements in order to limit the possibility to enlarge the myringotomy hole or to damage the ossicular chain.

4.7

Take Home Messages

• Ventilation tube positioning is a common procedure that every ENT surgeon should be able to perform. Endoscopic insertion and removal might help in case of unfavorable anatomy of the external auditory canal (i.e., exostoses, stenotic EAC, anterior bulging). Moreover, it easily permits to recognize middle ear landmarks and to detect eventual vascular abnormalities. • The procedure in the ovine model is harder due to the relatively small size of the external auditory canal, the bigger extension of pars flaccida that covers the middle ear landmarks (i.e., ossicular chain details) and the elasticity of the eardrum. These aspects imply that this kind of training might be useful to get experience in performing this technique avoiding surgical mistakes and shortening surgical operative times. • There are some very similar gestures between human and ovine, especially during v­ entilation tubes insertion phase. The ability to perform this procedure correctly let the surgeon gain confidence and improve his skills also in human live surgery. The myringotomy and ventilation tube positioning is one of the first approaches to perform for the staged training program and so this chapter represents the starting point in endoscopic ear surgery training on the ovine model.

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References 1. Paradise JL, Bluestone CD.  Consultation with the specialist: tympanostomy tubes: a contemporary guide to judicious use. Pediatr Rev. 2005;26: 61–6. 2. Corbeel L. What is new in otitis media? Eur J Pediatr. 2007;166:511–9. 3. Kuo CL, Tsao YH, Cheng HM, Lien CF, Hsu CH, Huang CY, et al. Grommets for otitis medial with effusion in children with cleft palate: a systematic review. Pediatrics. 2014;134(5):983–94.

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4. Paulson LM, Weaver TS, Macarthur CJ.  Outcomes of tympanostomy tube placement in children with down syndrome—a retrospective review. Int J Pediatr Otorhinolaryngol. 2014;78:223–6. 5. Di Francesco R, Paulucci B, Nery C, Bento RF.  Cranio-facial morphology and otitis media with effusion in children. Int J Pediatr Otorhinolaryngol. 2008;72(8):1151–8. 6. Rosenfeld RM, Schwartz SR, Pynnonen MA, Tunkel DE, Hussey HM, Fichera JS, et  al. Clinical practice guideline tympanostomy tubes in children. Otolaryngol Head Neck Surg. 2013;149(1 Suppl):S1–S35.

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Endoscopic Approach to the Tympanic Cavity: Tympanomeatal Flap and Canalplasty Marco Bonali, Matteo Fermi, Brandon Isaacson, Daniel J. Lee, Gaetano Ferri, Davide Soloperto, Daniela Lucidi, and Livio Presutti

5.1

Introduction [1–3]

Canalplasty procedure aims to enlarge the bony external auditory canal (EAC). This procedure can be performed both as curative treatment (for exostoses or EAC pathologies removal) and as a preliminary surgical step during tympanoplasty or endoscopic approaches to inner ear and lateral skull base. Commonly, the vision of the anteroinferior portion of the tympanic membrane is hampered by prominent tympanic bone. Remodeling EAC allows creation of a larger surgical space with better exposition of the annulus, eardrum, and tympanic cavity, and also improves handling of the surgical instruments and makes possible for the second surgeon to help during the surgical maneuvers. Electronic Supplementary Material The online version of this chapter (https://doi.org/10.1007/978-3-030-470050_5) contains supplementary material, which is available M. Bonali (*) · L. Presutti Department of Otolaryngology - Head and Neck Surgery, University Hospital of Modena, Modena, Italy M. Fermi · G. Ferri · D. Lucidi Department of Otolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy B. Isaacson Department of Otolaryngology-Head and Neck Surgery, UT Southwestern Medical Center, Dallas, TX, USA e-mail: [email protected]

The need for canalplasty during tympanoplasty has been widely reduced by the endoscopic transcanal approach, which provides superior visibility of all middle ear compartments. Conventional microscopic approach in fact requires canalplasty to reach a 360° vision of the annulus with an only microscopic framing. Nevertheless, the canalplasty still represents a very important step in transcanal transpromontorial approaches to the internal auditory canal. Moreover, it is an important step in surgical training on ovine model due to the relatively small size of the EAC that sometimes requires enlargement to obtain a better maneuverability of the endoscope and surgical instruments. to authorized users. The videos can be accessed by scanning the related images with the SN More Media App.

D. J. Lee Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA, USA Department of Pediatric Otology and Neurotology, Mass. Eye and Ear, Boston, MA, USA e-mail: [email protected] D. Soloperto Department of Otolaryngology, Head and Neck Surgery, University Hospital of Verona, Verona, Italy

© Springer Nature Switzerland AG 2021 M. Bonali et al. (eds.), Comparative Atlas of Endoscopic Ear Surgery, https://doi.org/10.1007/978-3-030-47005-0_5

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5.2

Indications

–– Exostoses of the EAC with hearing impairment or draining ear –– Osteomas of the EAC –– External auditory canal stenosis –– External auditory canal pathologies (like cholesteatoma) –– Transcanal skull base surgery

Fig. 5.1 (a, b) The patient is positioned in a supine position with the head rotated on the contralateral side and the ear affected by pathology well exposed. (c) The angle between the head and the shoulder should be as wide as possible to ensure comfortable movements during the

5.3

 urgical Steps in Human S Procedure

5.3.1 Patient Positioning and Surgical Setting (Fig. 5.1) The patient is positioned on the operatory table in supine position with the head rotated on the contralateral side with respect to the affected ear. The

operation. (d) A single stitch can be put on the tragus skin (paying attention to preserve the tragal cartilage) and the suture thread attached anteriorly (black arrow) to enlarge the opening of the EAC meatus

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angle among the neck and the shoulder should be as wide as possible in order to facilitate transcanal surgical maneuvers. To achieve the widest opening of the EAC meatus, a stitch can be put on the tragus skin and the suture thread is attached anteriorly above the ipsilateral eye (Fig. 5.1). The video equipment should be placed just beyond the patient’s head. A 15-cm length, 0° angled endoscope (Karl Storz, Tuttlingen, Germany, or similar) is held by the left hand, and the operative instruments by the right hand (for right-handed surgeons). A 3-mm diameter endoscope should be sufficient for EAC surgery. The endoscope is connected to AIDA three-chip high-resolution monitor and camera system (Karl Storz, Tuttlingen, Germany, or similar). A curette and/or microdrill with cutting and diamond burr are fundamental to perform the bony work in the external auditory canal.

5.3.1.1 Canalplasty: Exostoses/ Osteomas Removal The procedure most similar to ovine model canalplasty in human live surgery is represented by the exostoses/osteomas removal, because of the bony bulging to drill and due to the necessity to preserve the skin flaps during the drilling phase.

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Step 1: Cleaning of the EAC and Visualization of the Tympanic Membrane (Figs. 5.2, 5.3, and 5.4) Accurate cleaning of the EAC is the first step of the procedure and is preparatory to the evaluation of the stenosis due to the bony bulging. External auditory canal hair trimming should be mandatory in case of hairy ear canal (Fig.  5.2). This avoids continuous necessity to clean the tip of the endoscope during in and out movements through the external auditory canal. After this phase of cleaning, the 0° 3-mm diameter endoscope is the best tool to evaluate the tympanic membrane medial to the EAC stenosis, if possible (Figs. 5.3 and 5.4). Step 2: External Auditory Canal Incision and Elevation of the Skin Flaps (Figs. 5.5, 5.6, and 5.7) A skin incision is made in the EAC just lateral to the bony prominence with a circular scalpel (Fig.  5.5) or a molecular resonance scalpel (Vesalius, TeleaMedical, Sandrigo, Vicenza, or similar) (Fig. 5.6). A lateral-to-medial skin dissection is performed interposing cottonoids soaked in epinephrine solution between the skin flap and the underlying bone bulging of the external auditory canal (Fig.  5.7).

Fig. 5.2  Right ear. (a, b) The external auditory canal hair trimming with microscissors is performed to keep the optic lens clean during the surgical procedure. During this step, the skin should not be injured to avoid a troublesome bleeding

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Fig. 5.3  Case #1. Right ear. (a, b) Endoscopic exploration of the tympanic membrane. The bony bulging of the EAC covers partially the tympanic membrane (black dots). tm tympanic membrane, eac external auditory canal

Fig. 5.4  Case #2. Right ear. (a, b) The tympanic membrane (white asterisk) is not entirely visible due to the bony prominences of the EAC. bb bony bulging

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Fig. 5.5  Case #1. Right ear. (a) The skin incision is made lateral to the bony prominence in the EAC with a round knife. (b–d) The skin flap is detached from the bone using a round knife until the entire portion of the external audi-

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tory canal is free of skin, to avoid injuries during the drilling phase. eac-s external auditory canal skin, eac-b external auditory canal bone, sf skin flap. White asterisk indicates the tympanic membrane

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Fig. 5.6  Case #2. Right ear. (a) A molecular resonance scalpel is used to make the skin incision. (b–d) The round knife is put on the cottonoids soaked with adrenaline to

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reduce bleeding and perform a smooth exposure of the bone without injuring the EAC skin. eac-s external auditory canal skin, sf skin flap, bb bone bulging

Fig. 5.7  Case #2. Right ear. (a, b) The bone is completely exposed using suction or a round knife and cottonoids to push the skin flap. sf skin flap

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We recommend pushing the cottonoids forward with the dissector or suction tubes; the skin is then detached from the bone until the entire bony prominence is completely free of skin. Step 3: Drilling of the External Auditory Canal (Figs. 5.8, 5.9, 5.10, 5.11, and 5.12) The meatal skin flap and the eardrum can be protected by means of round shaped aluminum sheet or small cottonoid (Fig. 5.8). Circumferential drilling of the external auditory canal on demand is performed to enlarge the direct view of the tympanic membrane. High speed drill, with cutting or diamond burr, under intermittent irrigation allows for precise bone removal and is believed to decrease the risk of

Fig. 5.8  Case #1. Right ear. (a) A cottonoid (black asterisk) is put between the skin flap and the bone to avoid skin injuries. (b–d) A cutting bur is used to drill and regularize

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injury of the surrounding structures (Fig.  5.9). Canalplasty may also be performed by different types of instruments such as Piezosurgery. The bone drilling starts from the base of the bony prominence to preserve the skin as much as possible. Then, the bone is removed with a periosteal elevator (Figs. 5.10 and 5.11). At the end of the procedure, the remaining bone is regularized again with the diamond bur (Fig. 5.12). Step 4: Meatal Skin Flaps Replacement (Figs. 5.13 and 5.14) Once the bony canal overhangs lateral to the tympanic membrane have been removed, the meatal skin flaps should be replaced at their initial position. The flap can be lateralized by means of a

the bone. eac-b external auditory canal bone, eac-s external auditory canal skin

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Fig. 5.9  Case #2. Right ear. (a, b) A diamond bur is used to start the drilling of the bony bulging, paying attention not to hit the surrounding skin with the tip of the bur. eac-b external auditory canal bone, eac-s external auditory canal skin

Fig. 5.10  Case #2. Right ear. (a, b) The base of the bony prominence (black asterisk) is drilled. (c, d) The bone fragment is then removed by the means of a periosteal

elevator. eac-bb external auditory canal bone bulging, tm tympanic membrane, sk-f skin flap

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Fig. 5.11  Case #2. (a–d) The bony fragment is carefully removed, leaving the skin flap intact in a medial position in the EAC. b-fr bony fragment

Fig. 5.12  Case #2. Right ear. (a–d) A diamond bur is used to regularize the bone of the EAC after the bony prominence removal. eac-b external auditory canal bone,

sf skin flap. Black asterisks indicate the bone drilled to create a smooth surface

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Fig. 5.12 (continued)

Fig. 5.13  Case #1. Right ear. (a, b) The skin is gently detached form the bone until the skin flap is entirely visualized. (c, d) The skin flap is repositioned to cover the

bone of the EAC as much as possible. eac-b external auditory canal bone, sf skin flap

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Fig. 5.14  Case #2. Right ear. (a, b) Final view of the tympanic membrane after the procedure. eac-b external auditory canal bone, eac-s external auditory canal skin, tm tympanic membrane

small suction tip (without closing the suction valve to avoid generating excessive pressure) and then laid on to the bony surface of the EAC with a round knife (Figs. 5.13 and 5.14). An attempt should be made to preserve as much skin as possible in order to reduce the amount of bony canal uncovered and to fasten up the reepithelization process that can take up to 4 weeks.

5.3.1.2 Special Application: Atticotomy (Figs. 5.15 and 5.16) Once the tympanomeatal flaps have been elevated and when an enhanced exposure of the superior retrotympanum and the epitympanum is required, an atticotomy can be performed. This surgical step is one of the most common in transcanal endoscopic procedures. It can be performed either with curette or microdrill or powered instruments, such as Piezosurgery (Mectron, Carasco, Genova, Italy, or similar). It consists of removal of the posterosuperior aspect of the bony annulus and canal.

5.4

Hints and Pitfalls (Human)

• The elevation of the meatal flap can be performed with cottonoids soaked with epinephrine in order to limit the external canal bleeding. • An attempt should be made to preserve as much external auditory canal skin as possible in order to facilitate the reepithelization process. • During the drilling phase it is important to carefully control the anterior bony wall of the external auditory canal. This step is important to avoid an excessive exposure of the temporomandibular joint, which needs to be identified only by transparency without provoking bony defects. Moreover, the posterior wall drilling should be conducted carefully to avoid creating communication between the external auditory canal and the mastoid air cells, which can lead to cholesteatoma formation, and to avoid injuring the third tract of the facial nerve.

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Fig. 5.15  Right ear. (a, b) The atticotomy is performed by the means of a bur. The scutum bone (black asterisk) is drilled until the epitympanum and the incudomalleolar joint is clearly visible. (c, d) A piezoelectric device is used

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to remove the posterosuperior aspect of the bony annulus and the bony canal (black asterisk). in incus, ma malleus, imj incudomalleolar joint, fn facial nerve, pr promontory, lsc lateral semicircular canal

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Fig. 5.16  Right ear. (a) The retrotympanum and posterior epitympanum are covered by the posterosuperior portion of the bony annulus and bony canal. (b–d) A curette

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is used to remove the bone (black asterisk) and complete the atticotomy. in incus, ma malleus, tmf tympanomeatal flap

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5.5

 urgical Steps on Ovine S Model

5.5.1 Surgical Instrumentations (Figs. 5.17, 5.18, 5.19, and 5.20) A 3-mm 0° endoscope should be sufficient to perform this procedure. Different sized round knives, sickle knives, and Thomassin’s dissectors are recommended (Fig.  5.17). A curette

and/or microdrill with cutting and diamond burrs are needed to perform the bony work in the external auditory canal (Fig.  5.18). The sheep should be positioned with the contralateral side on the dissection table and the tip of the nose anteriorly. The surgeon should stand (or sit) at the posterior end of the ovine model (Fig. 5.19). The video equipment is positioned in front of the surgeon (Fig. 5.20).

Fig. 5.17  Instruments set for tympanomeatal flap elevation and canalplasty on ovine model. From left to right: microscissors, Thomassin’s dissectors, round knife, Hartmann forceps, sickle knife, suction tubes (various size)

Fig. 5.18  Instruments for canalplasty. (a, b) A set of cutting and diamond burr is very useful to drill the bony portion of the external auditory canal. (c) The bone removal

(especially during the identification of the third tract of the facial nerve) can be performed using a bone curette (also a piezoelectric device can be used for this purpose)

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Fig. 5.19 (a, b) Trainee’s hands position in case of a not decorticated head. Notice the orientation of the nose of the sheep superiorly (from 12 to 2 o’clock), to perform the dissection in a surgical position

Fig. 5.20  Dissection table including the ovine’s head, surgical instruments, endoscopic optics, and the AIDA three-­ chip high-resolution monitor and camera system (Karl Storz, Tuttlingen, Germany, or similar)

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5.5.2 Surgical Steps (Fig. 5.21: Video 5.1)

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Step 1: Preparation of the Ear Canal and Visualization of the Tympanic Membrane (Figs. 5.22, 5.23, and 5.24) The first step to allow a better dissection procedure is to cut the hair at the level of the EAC meatus and the lateral portion of the EAC (in particular for not decorticated models). Microscissors are required to complete this step, that is very important to avoid dirtying the optic while moving the endoscope in and out the EAC (Fig. 5.22).

Once the external auditory canal is completely clean, the 0° angled lens 3 mm diameter endoscope is put inside the canal to visualize the tympanic membrane (Figs. 5.23 and 5.24). At this point, two different procedures can be performed: the first is the tympanomeatal flap elevation without a consistent drilling of the bony portion of the EAC (Case #1); this approach allows the surgeon to complete the myringotomy and grommet insertion, myringoplasty, ossiculoplasty, and stapes surgery. The second consists in the elevation of the flap associated to the drilling

Fig. 5.21  (Video 5.1) Tympanomeatal flap and canalplasty. Two different types of tympanomeatal flap to gain the access to the tympanic cavity are presented in this video. The first is the regular flap and it allows the visual-

ization of the ossicular chain region. The second is associated to the canalplasty and is used to reach the round window region and to perform the approach to the internal auditory canal (https://doi.org/10.1007/000-5a)

Fig. 5.22 (a, b) The hair of the external auditory meatus and lateral portion of the EAC (black asterisk) is cut with microscissors

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Fig. 5.23  Right ear. Case #1. Tympanic membrane visualization. (a) Panoramic view of the ear canal and tympanic membrane (the posterior wall of the EAC lays inferiorly in this picture). (b) Detail of the tympanic mem-

brane. eac-s external auditory canal skin, pf pars flaccida of the tympanic membrane, ma malleus, pt pars tensa of the tympanic membrane

Fig. 5.24  Right ear. Case #2. Exploration of the tympanic membrane. (a, b) Notice the pars flaccida widely visible and the pars tensa hidden behind the EAC bone bulging

(inferiorly and posteriorly). eac-s external auditory canal skin, pf pars flaccida of the tympanic membrane, ma malleus, pt pars tensa of the tympanic membrane

of the posteroinferior portion of the bony canal (Case #2); through this approach, it is possible to visualize the round window area, decompress the facial nerve, and reach the IAC.

gical position, with the posterior wall of the ear canal located inferiorly; Figs.  5.25, 5.26, 5.27, and 5.28). It should be made by means of a round knife (or a sickle knife). Flap dissection proceeds, pushing the flap medially and anteriorly by means of a round knife, whose round edge sticks to the bony EAC in order to progressively detach the skin encompassing the incision until the tympanic mucosa is identified (Figs.  5.29 and 5.30). Differently from the human, the ovine model does not have any fibrous annulus (Fig. 5.31). Cottonoids soaked with saline can be used to obtain blunt dissection avoiding tearing the flap. The flap elevation should be uniformly performed at every

Case #1 Step 2: External Auditory Canal Incision and Elevation of Tympanomeatal Flap (Figs. 5.25, 5.26, 5.27, 5.28, 5.29, 5.30, 5.31, 5.32, 5.33, 5.34, and 5.35) An incision is made about 0.5–1  cm lateral to the pars flaccida of the eardrum. The incision is made from the 10 o’clock to the 4 o’clock position (considering the view of the tympanic membrane through a traditional sur-

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a

b

c

Fig. 5.25  Right ear. Case #1. Tympanic membrane view from a classic surgical position (posterior wall of EAC inferiorly). (a–c) The superior straight incision (black

line) is made with a round knife and it starts at 10 o’clock position, close to the tympanic membrane

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Fig. 5.26  Right ear. Case #1. (a–c) The superior incision of the skin is completed until the bone of the EAC is clearly visible (black dots)

Fig. 5.27  Right ear. Case #1. (a, b) The inferior straight incision (black line) is made, starting from the 4 o’clock position. Black dots represent the previous superior incision

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c

Fig. 5.28  Right ear. Case #1. Completion of the EAC skin incisions. (a, b) A third vertical skin cut is made approximately 0.5–1  cm lateral to the tympanic mem-

brane to connect the inferior and superior incisions previously created. (c) Final view of the incisions with the bone clearly exposed (black dots)

Fig. 5.29  Right ear. Case #1. (a, b) A round knife is used to gently push the skin of the EAC medially and anteriorly, detaching completely the flap from the underlying

bone (by scratching the bone to feel it under the instrument). eac-b external auditory canal bone

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b

c

Fig. 5.30  Right ear. Case #1. (a–c) The superior portion of the skin flap is pushed inferiorly and anteriorly to visualize the mucosa of the tympanic cavity. tmf tympanomeatal flap

a

Fig. 5.31  Right ear. Case #1. (a) The flap is progressively elevated posteriorly with the help of a cottonoid to preserve the skin as much as possible. (b, c) The fibrous

b

tympanic annulus is absent in the ovine model (black arrow). tmf tympanomeatal flap, eac-b external auditory canal bone

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edge (using forceps, Thomassin’s dissectors, round knives), otherwise the flap could break (Figs. 5.32, 5.33, 5.34, and 5.35). Step 3: Access to the Tympanic Cavity (Figs. 5.36, 5.37, and 5.38) The tympanomeatal flap elevation is completed and the tympanic cavity is visualized. The ossicular chain is well exposed without drilling the bony EAC (Fig.  5.36). To better expose the oval window area and the stapedial tendon, a small amount of the posterosuperior bone of the EAC can be removed with a curette (Figs. 5.37 and 5.38).

Fig. 5.31 (continued)

a

b

c

Fig. 5.32  Right ear. Case #1. (a–c) The mucosa of the superior portion of the tympanic cavity (black asterisk; immediately medial to the flap created) is opened with a

round knife to gain the access to the tympanic cavity (black arrow). tmf tympanomeatal flap

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Fig. 5.33  Right ear. Case #1. (a–c) Forceps can be used to pull and complete the opening of the mucosa at the superior aspect of the tympanic cavity. tmf tympanomeatal flap. Black asterisk indicates the mucosa of the tympanic cavity

Fig. 5.34  Right ear. Case #1. (a, b) The tympanomeatal flap is pushed inferiorly with a Thomassin’s dissector (or a round knife). (c, d) The superior portion of the tympanic cavity is visualized (black dots). An additional tegmen

tympani bone is clearly seen. tmf tympanomeatal flap, pf pars flaccida of the tympanic membrane, ma malleus, eac-­ b external auditory canal bone, tb tegmen bone

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Fig. 5.34 (continued)

Fig. 5.35  Right ear. Case #1. (a, b) The inferior and posterior aspect of the tympanomeatal flap is elevated and the tympanic cavity mucosa is exposed (black asterisk). eac-b

external auditory canal bone, tmf tympanomeatal flap, tm tympanic membrane

Case #2 Step 2: External Auditory Canal Incision and Elevation of Tympanomeatal Flap (Figs. 5.39, 5.40, 5.41, 5.42, 5.43, and 5.44) This step is basically the same as previously described. The incisions of the skin of the EAC are made with a sickle knife or a round knife and it is very important in this case to expose

properly the inferior portion of the EAC bone (Figs. 5.39, 5.40, 5.41, and 5.42). The dissection of the flap then proceeds medially and anteriorly (Figs. 5.43 and 5.44). Step 3: Drilling of the External Auditory Canal (Figs. 5.45, 5.46, 5.47, 5.48, and 5.49) Once the meatal skin is reflected medially towards the eardrum and the tympanic cav-

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Fig. 5.36  Right ear. Case #1. (a, b) The ossicular chain is progressively exposed with a Thomassin’s dissector (except for the handle of the malleus, attached inferiorly to the hypotympanic region). (c, d) The exposure of the

tympanic cavity is completed and the anatomical structures are in evidence. teg tegmen tympani, oc ossicular chain, in incus, ma malleus, fn facial nerve, s stapes, st stapedial tendon

ity, the bony canal is exposed. In this phase it is very important to elevate the flap properly, especially in the posteroinferior portion of the EAC (the main area of drilling; Fig.  5.45). A round-shape aluminum sheet could be placed in contact with the flap in order to protect it during drilling of the bony canal (Fig.  5.46). The bony removal should be performed especially at the posterior and inferior aspect of the

ovine EAC in order to improve the exposure of the eardrum and tympanic cavity (Figs. 5.47 and 5.48). Once the caliber of the external auditory is satisfactory, the meatal skin flaps can be replaced back at their initial position by means of a small suction and a round knife, to check the result of canalplasty (Fig.  5.49). The meatal skin should be preserved as much as possible.

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Fig. 5.37  Right ear. Case #1. (a) Detail of the ossicular chain joints. (b, c) A curette is used to remove a small amount of bone of the EAC posterosuperiorly. (d)

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Panoramic view of the tympanic cavity. imj incudomalleolar joint, isj incudostapedial joint, in incus, ma malleus, ct chorda tympani, fn facial nerve, s stapes

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Fig. 5.38  Right ear. Case #1. (a, b) The posterior bony aspect of the EAC is further removed with a curette to visualize the chordal eminence with the chorda tympani and the oval window region. (c, d) Final view of the ana-

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tomical structures of the tympanic cavity at the end of this approach. in incus, ma malleus, fn facial nerve, s stapes, st stapedial tendon, ct chorda tympani

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Fig. 5.39  Right ear. Case #2. (a–d) The inferior skin incision (black line) is made through a sickle knife and starts at 4 o’clock position (traditional surgical position with the posterior wall of the EAC inferiorly)

Fig. 5.40  Right ear. Case #2. (a, b) A round knife (or powered devices like electric scalpel) is employed to refine the incision (black line) and reach the EAC bone

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Fig. 5.41  Right ear. Case #2. (a, b) The superior line of incision (black line) of the skin is created by the means of a sickle knife (or a round knife). (c, d) The EAC bone

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(black line) is exposed under the skin superiorly (starting from 10 o’clock position)

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Fig. 5.42  Right ear. Case #2. (a–c) The incisions previously created are connected by a third lateral line (made through a round knife). (d) Finally, the EAC bone is completely exposed (black dots) and the flap created

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b

c

Fig. 5.43  Right ear. Case #2. (a–c) The skin flap is progressively pushed medially to reach the tympanic membrane. The round knife scratches onto the bone to elevate

the flap without injuring the skin. tmf tympanomeatal flap, eac-b external auditory canal bone

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Fig. 5.44  Right ear. Case #2. (a, b) The tympanic membrane is approached superiorly to avoid excessive tension of the flap during the drilling phase in the inferior portion of the EAC. tmf tympanomeatal flap

Fig. 5.45  Right ear. Case #2. (a–c) The tympanomeatal flap is reflected inferiorly with a round knife. Notice the absence of tympanic annulus in the ovine model (black

arrowhead). (d) The inferior and posterior portion of the bony EAC (black dots) are well visualized. tmf tympanomeatal flap, eac-b external auditory canal bone

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Fig. 5.46  Right ear. Case #2. (a, b) A small piece of aluminum (e.i. package of stiches; black asterisk) is placed medially to the bone of the EAC and over the flap to protect it. tmf tympanomeatal flap, eac-b external auditory canal bone

Fig. 5.47  Right ear. Case #2. (a–d) The cutting bur is positioned at the posteroinferior portion of the EAC bone, and drilling is performed carefully to avoid injuries to the tympanomeatal flap

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c

Fig. 5.48  Right ear. Case #2. (a–c) Drilling is protracted until the bony bulging at the posteroinferior portion of the EAC is completely removed. tmf tympanomeatal flap, eac-b external auditory canal bone

Fig. 5.49  Right ear. Case #2. (a) The tympanomeatal flap is finally replaced in its original position after the canalplasty. (b) Detail of the tympanic membrane with the pars

tensa and the malleus better visualized. ma malleus, pf pars flaccida of the tympanic membrane, pt pars tensa of the tympanic membrane

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Step 4: Access to the Tympanic Cavity and Enlargement of the EAC (Figs. 5.50, 5.51, 5.52, 5.53, 5.54, and 5.55) After the elevation of the tympanomeatal flap, the detachment of the tympanic membrane proceeds to obtain a complete visualization of the tympanic cavity (Figs. 5.50, 5.51, 5.52, and 5.53). Moreover, an enlargement of the ear canal is often required for further surgical steps to obtain a wide

working space for the endoscope and other instruments (Figs.  5.54 and 5.55). A bone curette can be used to remove small bony fragments, especially those located close to the flap or the tympanic membrane. The atticotomy is made when the exposure of the retrotympanum has to be improved (i.e., round window niche exposure) and the posterior portion of the EAC can be removed to approach widely the round window area.

Fig. 5.50  Right ear. Case #2. (a) Overview of the surgical field after canalplasty. (b, c) A round knife (or a Thomassin’s dissector) is used to pull the mucosa of the tympanic cavity (black asterisk) downward. (d) The tympanic cavity is finally visualized superiorly (black arrow-

head) and the tympanomeatal flap is reflected progressively medially and anteriorly. eac-b external auditory canal bone, tmf tympanomeatal flap. Black dots indicate the area of canalplasty

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Fig. 5.51  Right ear. Case #2. (a, b) Suction tubes or a blunt dissector can be used to progressively expose the entire tympanic cavity (from up to down; black arrowhead); in this

phase it is very important to carefully dissect the flap from the EAC bone in order to avoid breaking fragments of skin. Black asterisk indicates the mucosa of tympanic cavity

Fig. 5.52  Right ear. Case #2. (a–d) The ossicular chain and the facial nerve are exposed (black dots) by the means of forceps that pull the TMF inferiorly and anteriorly. in

incus, tmf tympanomeatal flap, fn facial nerve, eac-b external auditory canal bone

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Fig. 5.53  Right ear. Case #2. (a, b) Final view of the tympanic cavity after the TMF elevation. in incus, ma malleus, s stapes, fn facial nerve, ct chorda tympani

Fig. 5.54  Right ear. Case #2. (a–c) The bone curette is used to progressively remove attic and posterior wall of EAC bone. Notice the rotational movement of the curette

to control the tip and avoid injuries to surrounding structures. (d) Detail of bone removal. in incus, ma malleus, fn facial nerve, eac-b external auditory canal bone

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Fig. 5.55  Right ear. Case #2. (a, b) Panoramic overview of the tympanic cavity after the EAC bone removal. (c, d) Detailed view of the tympanic cavity with all the anatomical structures well exposed. Notice the round window

region clearly visible. in incus, ma malleus, fn facial nerve, s stapes, pr promontory, ct chorda tympani, rwn round window niche

5.6

avoid leaving skin fragments and to lose the plane to access the tympanic cavity. This step is even more important than in human surgery, because in the ovine model the fibrous annulus is missing. • The protection of the meatal (or tympanomeatal) flap is advisable during the drilling of the bony canal, otherwise the skin might be injured together with the pars flaccida of the eardrum and the ossicular chain attached on it. For this reason, the flap should be properly reflected to uncover the bone and drill safely.

Hints and Pitfalls (Ovine)

• The canalplasty is a surgical step often required in ovine model training in order to improve the surgical working space and to obtain an adequate exposure of hidden areas of the tympanic cavity, such as the retrotympanum (i.e., round window niche). • During the tympanomeatal flap elevation, the dissection of the tissues should be done in a subperiosteal fashion. The bone should be scratched with the dissection instruments to

5  Endoscopic Approach to the Tympanic Cavity: Tympanomeatal Flap and Canalplasty

• The removal of the posterior wall of EAC bone should be done carefully and from superficial to deep, thus similar avoiding holes in the bone because of the presence of the facial nerve under the bony surface.

5.7

Take Home Messages

• Canalplasty is an important procedure in otologic surgery, because it allows to gain a wider view of the tympanic cavity, to facilitate the dissection and the reconstruction during several surgical procedures. Another fundamental application of this technique is during the removal of exostoses/ osteomas of the external auditory canal bone. • The endoscopic atticotomy and posterior wall of the EAC removal in human specimens are easier due to the wider size of the canal, with respect to the ovine model. A regular drill, a curette, or powered devices (like Piezosurgery; Mectron, Carasco, Genova) can be used to obtain a proper dissection of the bone. • Regarding the gestures during ovine training in canalplasty, there is a challenging

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phase of this approach, related to the necessity to elevate the tympanomeatal flap and protect it during the drilling procedure. This step is very important because it is really similar to the removal of exostoses/osteomas in human live surgery (a procedure not so easy to perform under endoscopic view). Moreover, the atticotomy in ovine model represents a good exercise for the trainee and requires the same gestures as for attic removal in human models.

References 1. Morrison DR, O’Connell B, Lambert PR. The impact of canalplasty on outcomes of medial graft tympanoplasty. Otol Neurotol. 2019;40(6):761–6. https://doi. org/10.1097/MAO.0000000000002259. 2. Grinblat G, Prasad SC, Piras G, et  al. Outcomes of drill canalplasty in exostoses and osteoma: analysis of 256 cases and literature review. Otol Neurotol. 2016;37(10):1565–72. https://doi.org/10.1097/MAO. 0000000000001239. 3. Presutti L, Marchioni D. Endoscopic ear surgery. 1st ed. Stuttgart: Thieme Medical Publishers; 2014.

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Myringoplasty Francesco Mattioli, Matteo Fermi, Giulia Molinari, Marco Bonali, Michael Ghirelli, Daniele Marchioni, George B. Wanna, and Lukas Anschuetz

6.1

Introduction

The tympanic membrane is a tri-layer delicate structure located at the medial end of external auditory canal (EAC), representing the separation between the external and the middle ear. Its shape resembles a very shallow cone pointing medially. The layers encountered from lateral to medial are: the skin, the intermediate layer, made up of collagen fibers, and the mucosa of the middle ear.

Electronic Supplementary Material The online version of this chapter (https://doi.org/10.1007/978-3-030-470050_6) contains supplementary material, which is available to authorized users. The videos can be accessed by scanning the related images with the SN More Media App.

F. Mattioli (*) · M. Fermi · G. Molinari · M. Ghirelli Department of Otolaryngology, Head and Neck Surgery, University Hospital of Modena, Modena, Italy M. Bonali Department of Otolaryngology - Head and Neck Surgery, University Hospital of Modena, Modena, Italy D. Marchioni Department of Otolaryngology - Head and Neck Surgery, University Hospital of Verona, Verona, Italy G. B. Wanna Department of Otolaryngology, New York Eye and Ear Infirmary of Mount Sinai, New York, NY, USA L. Anschuetz Department of ENT, Head and Neck Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland

Acute or chronic otitis, or ear trauma, are the main factors that can determine an eardrum perforation, which could also possibly heal spontaneously. The presence of a perforation that does not heal spontaneously in reasonable time, as in chronic otitis media, represents not only an anatomical but also a functional issue, requiring surgical correction in most of the cases. The aim of reconstructing a tympanic membrane is to allow the patient to have a normal or at least better quality of life (hearing, water sport, etc.). The eardrum repair is performed by using a free graft at the perforation site, which should act as a guide for re-­epithelialization of the eardrum. The material used varies among temporalis muscle fascia, tragal cartilage or perichondrium, and heterologous grafts (i.e., Biodesign Membrane®, Cook Medical, Bloomington, IN, USA). The tympanic membrane perforation could be classified based on localization and size of the defect. Depending on the characteristics of the perforation, the external auditory canal (EAC), and the middle ear-related findings (for instance state of the tympanic cavity and eustachian tube function), the endoscopic transcanal myringoplasty can be performed with one of these grafts. The graft can be positioned in underlay technique (under the tympanic annulus, once the tympanomeatal flap has been elevated), which is the most manageable way, or in overlay technique (over the tympanic annulus and under the squa-

© Springer Nature Switzerland AG 2021 M. Bonali et al. (eds.), Comparative Atlas of Endoscopic Ear Surgery, https://doi.org/10.1007/978-3-030-47005-0_6

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mous layer of the tympanic membrane), which requires the difficult step to peel only the lateral layer of the eardrum and place the graft over the fibrous layer of the tympanic membrane. The graft is usually positioned over malleus in our experience, paying particular attention to the correct positioning of the flap in the anterior portion of the tympanic membrane, under the anterior annulus, and in good contact with the edges of the perforation, to avoid blunting and medialization of the graft in the postoperative period. There are several potential advantages in performing endoscopic myringoplasty [1, 2]: • Clear visualization of the anterior annulus and the anterior limit of the perforation • Lack of necessity of canalplasty, usually even in cases of tortuous EAC • Evaluation of ventilation routes during surgery • Direct control of the ossicular chain and other middle ear anatomical structures [3] On the other hand, some disadvantages have to be pointed out [4, 5]: • One-handed surgery • Technical difficulties to perform overlay technique due to the fragility of the skin layer • Lack of stereoscopic view

6.2

Indications and Contraindications

6.2.1 Indications –– Dry tympanic perforations with normal middle ear mucosa –– Marginal perforations –– Conductive hearing loss due to the tympanic defect Eardrum perforation is a risk factor for skin migration from the external auditory canal to the

middle ear, with consequent development of a cholesteatoma. Thus, it is strongly recommended to treat it.

6.2.2 Contraindications –– Contralateral severe hearing loss should be taken in consideration before approaching the affected ear. –– Age