Innovations in Endoscopic Ear Surgery [1st ed. 2020] 978-981-13-7931-4, 978-981-13-7932-1

Table of contents :
Front Matter ....Pages i-x
Innovations in Endoscopic Ear Surgery (Seiji Kakehata)....Pages 1-4
The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach (Seiji Kakehata, Tsukasa Ito)....Pages 5-17
Setup and Safety of Powered TEES (Tsukasa Ito, Seiji Kakehata)....Pages 19-31
Resected Area During Transcanal Endoscopic Ear Surgery for Cholesteatomas with an Antral Extension (Suetaka Nishiike, Takao Imai, Kazuo Oshima, Satoru Uetsuka)....Pages 33-44
Computer Simulations of Transcanal Endoscope Ear Surgery (Kazunori Futai, Seiji Kakehata)....Pages 45-53
Presurgical Diagnostic Imaging of Middle Ear Cholesteatomas for Transcanal Endoscopic Surgery (Masafumi Kanoto)....Pages 55-62
Approach to the Inner Ear by “Underwater” Endoscopic Ear Surgery: Its Utilization and Prospects (Daisuke Yamauchi, Yohei Honkura, Yosuke Hara, Jun Ohta, Hiroshi Hidaka, Yukio Katori)....Pages 63-72
An Augmented Reality Interface for Endoscopic Ear Surgery (Nozomu Matsumoto, Byunghyun Cho, Makoto Hashizume, Takashi Nakagawa)....Pages 73-78
Regeneration of Middle Ear Mucosa for TEES (Kazuhisa Yamamoto, Hiromi Kojima)....Pages 79-84
Bone Curette Handle for Improved Bone Removal in Endoscopic Ear Surgery (Yu Matsumoto)....Pages 85-87
Endoscopic Regenerative Medicine for Tympanic Membrane (Shin-ichi Kanemaru)....Pages 89-95
Three-Dimensional Displacement of the Endoscope (Yasuomi Kunimoto, Taihei Fujii, Hiroaki Yazama)....Pages 97-100
Endoscopic Surgery for Adhesive Otitis Media (Kunio Mizutari)....Pages 101-108

Citation preview

Innovations in Endoscopic Ear Surgery Seiji Kakehata Tsukasa Ito Daisuke Yamauchi Editors

123

Innovations in Endoscopic Ear Surgery

Seiji Kakehata  •  Tsukasa Ito Daisuke Yamauchi Editors

Innovations in Endoscopic Ear Surgery

Editors Seiji Kakehata Department of Otolaryngology Head and Neck Surgery Faculty of Medicine Yamagata University Yamagata Japan

Tsukasa Ito Department of Otolaryngology Head and Neck Surgery Faculty of Medicine Yamagata University Yamagata Japan

Daisuke Yamauchi Department of Otolaryngology Head and Neck Surgery Tohoku University Graduate School of Medicine Sendai Japan

ISBN 978-981-13-7931-4    ISBN 978-981-13-7932-1 (eBook) https://doi.org/10.1007/978-981-13-7932-1 © Springer Nature Singapore Pte Ltd. 2020 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 Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Foreword

Innovations in Endoscopic Ear Surgery provides an important look into the growing field of endoscopic ear surgery from the surgeons in Japan. We in Italy are very familiar with the activities of Japanese surgeons and have been fortunate to be able to work together with many of these surgeons. Prof. Seiji Kakehata has been a leader in the field of endoscopic ear surgery not only in Japan but also internationally. I am so pleased to see that more Japanese surgeons are also following in his footsteps and working to advance the field in ways that are not only exciting but, more importantly, beneficial to patients. This text comes at a critical time and should be read by anyone who is interested in endoscopic ear surgery. Specifically, endoscopic ear surgery is emerging from its position as a junior partner to microscopic ear surgery and is moving toward taking its place as the conventional ear surgical approach. We look forward to the day when the title of the follow-up text of Innovations in Endoscopic Ear Surgery will simply be Innovations in Ear Surgery because endoscopic ear surgery will be synonymous with ear surgery. I look forward to learn about and adopt the new techniques introduced in Innovations in Endoscopic Ear Surgery, and I encourage all ear surgeons to join the growing community of endoscopic ear surgeons. June, 2019    

Livio Presutti, M.D. Professor and Chair Department of Otolaryngology University Hospital of Modena Modena, Italy

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Preface

Getting a good picture of what the internal structures of the ear looked like had long been a challenge to otologists. It was possible to peer into the external auditory canal via the microscope, but the curving canal itself and the structures through which it travels and opens up onto have remained hidden to the microscope with its rigid, straight-line view. Conventional microscopic ear surgery has, as a result, had to remove anatomical structures to facilitate visualization. While other surgical fields incorporated the endoscope early on into the standard practice, the narrowness of the external auditory canal of the ear had long represented a barrier to the use of the endoscope in the field of otology. However, otologists started to work to get a better “picture” of what lies within the ear in the 1980s using the endoscopic and analog cameras, followed by actual endoscopic surgery in the late 1990s. Endoscopic ear surgery came into its own at the end of the first decade of the twenty-first century with the introduction of high-definition digital images. Ear surgeons can now see the tiny micrometer-sized anatomical structures within the ear projected onto large monitors with no degradation of the image quality. Thus, a new world has been opened to ear surgeons with endoscopic ear surgery rapidly maturing as a field and entering into a stage where innovations are taking endoscopic ear surgery and particularly transcanal ear endoscopic surgery (TEES) into hitherto uncharted areas. Innovations in Endoscopic Ear Surgery introduces the reader to the latest contributions to the field by the Japanese endoscopic ear surgery “school.” We in Japan are proud of our position as early adopters and promoters of endoscopic ear surgery and are grateful for the chance to introduce new avenues of exploration that we have embarked upon. This book covers topics ranging from the incorporation of powered instruments into TEES, or what we call “powered TEES,” which allows us to move further into the ear, the safety of powered TEES, performing TEES underwater, the fusion of

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Preface

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advanced imaging technology and endoscopic ear surgery to facilitate both diagnosis and treatment of a variety of ear conditions, and merging cutting-­ edge regenerative medicine techniques with TEES to achieve optimal results with minimal invasiveness. I hope you will join us in our journey regardless of whether you have eyed the developments but not yet taken the plunge, have taken up the challenge, or are an old hand at endoscopic ear surgery. All are welcome to the world of endoscopic ear surgery! Yamagata, Japan

Seiji Kakehata

Contents

1 Innovations in Endoscopic Ear Surgery����������������������������������������   1 Seiji Kakehata 2 The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach����������������������������������������������   5 Seiji Kakehata and Tsukasa Ito 3 Setup and Safety of Powered TEES�����������������������������������������������  19 Tsukasa Ito and Seiji Kakehata 4 Resected Area During Transcanal Endoscopic Ear Surgery for Cholesteatomas with an Antral Extension����������������  33 Suetaka Nishiike, Takao Imai, Kazuo Oshima, and Satoru Uetsuka 5 Computer Simulations of Transcanal Endoscope Ear Surgery��������������������������������������������������������������������������������������  45 Kazunori Futai and Seiji Kakehata 6 Presurgical Diagnostic Imaging of Middle Ear Cholesteatomas for Transcanal Endoscopic Surgery ������������������  55 Masafumi Kanoto 7 Approach to the Inner Ear by “Underwater” Endoscopic Ear Surgery: Its Utilization and Prospects������������������������������������  63 Daisuke Yamauchi, Yohei Honkura, Yosuke Hara, Jun Ohta, Hiroshi Hidaka, and Yukio Katori 8 An Augmented Reality Interface for Endoscopic Ear Surgery��������������������������������������������������������������������������������������  73 Nozomu Matsumoto, Byunghyun Cho, Makoto Hashizume, and Takashi Nakagawa 9 Regeneration of Middle Ear Mucosa for TEES����������������������������  79 Kazuhisa Yamamoto and Hiromi Kojima 10 Bone Curette Handle for Improved Bone Removal in Endoscopic Ear Surgery������������������������������������������������������������������  85 Yu Matsumoto

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11 Endoscopic Regenerative Medicine for Tympanic Membrane����������������������������������������������������������������������������������������  89 Shin-ichi Kanemaru 12 Three-Dimensional Displacement of the Endoscope��������������������  97 Yasuomi Kunimoto, Taihei Fujii, and Hiroaki Yazama 13 Endoscopic Surgery for Adhesive Otitis Media���������������������������� 101 Kunio Mizutari

Contents

1

Innovations in Endoscopic Ear Surgery Seiji Kakehata

1.1

 Short History of the Use A of the Endoscope in Otology

While the invention of the endoscope can be traced back to Philipp Bozzini, a physician of Italian and German descent, in 1806 [1], it took more than 150 years for it to become a part of the tool set for the ear surgeon. While the endoscope has long been a standard tool in other surgical fields, otologists were late adopters to the use of the endoscope in surgery, despite the fact that the internal structures and spaces of the ear had long been among the most, if not the most, difficult areas to surgically expose and access even with a microscope. This delay in the incorporation of the endoscope into ear surgery can be attributed to the delicate and tiny anatomical structures which are often interlocking and located within a miniature maze that includes hidden recesses and dead ends. Ear surgeons when using a microscope are often required, even today, to operate blindly. Many internal ear structures only became visible during surgery just before the end of the twentieth century via the use of the endoscope. The endoscope was first incorporated into the field of otology as a diagnostic and photographic

tool. Nomura et  al. described in 1982 [2] using what they referred to as a needle otoscope to take photos of the tympanic membrane as well as the challenges involved. These challenges included the size of the camera itself, limitations on the size and quality of photos, and need for sending film out for development which were all part and parcel of photography in the predigital age. The endoscope next started to play a supporting role in microscopic ear surgery (MES) as a tool which allowed surgeons to look around corners into hidden recesses with straight and angled lens as reported by Thomassin [3]. It was particularly useful in cholesteatoma surgery where surgeons struggle to ensure that no remnants are left behind which can lead to a residual cholesteatoma.

1.2

The Endoscope Goes Solo

The most dramatic breakthrough came with the papers of Dr. Muaaz Tarabichi who described ear surgery successfully performed exclusively using an endoscope. His first papers in 1997 and 1999 [4, 5] described the removal of limited cholesteatomas by TEES.

S. Kakehata (*) Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Yamagata University, Yamagata, Japan e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2020 S. Kakehata et al. (eds.), Innovations in Endoscopic Ear Surgery, https://doi.org/10.1007/978-981-13-7932-1_1

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1.3

 igh Definition Takes It H to the Next Level

While ear surgery was being performed solely with the endoscope from the 1990s as stated above, the switch from standard definition (SD) to high definition (HD) imaging resulted in crystal-­clear images of the internal structures of the inner anatomy of the ear. These images allayed some of the fears associated with endoscopic ear surgery, particularly as related to worries about 2D images. This technological advance was accompanied by expanded interest in TEES  spurred on by the establishment of the International Working Group on Endoscopic Ear Surgery (IWGEES) in 2008. The members of the IWGEES were instrumental in developing and promoting TEES, and a real jump was seen in the number of surgeons performing endoscopic ear surgery around the world as we entered the 2010s.

1.4

Embarking on the Path to TEES

We hope that our book will stir the interest of ear surgeons and prompt many readers to take the first steps to incorporating TEES into their own surgical practice. However, as with most new endeavors, it is incumbent upon the novice TEES surgeon to gather the necessary information, study the appropriate resources, observe experts in action, and obtain the required skills through careful and diligent practice. This section shall take a brief look at relevant issues related to TEES, recommend resources for individual study, and suggest ways to participate in the growing community of TEES surgeons.

1.4.1 Steep Learning Curve A common refrain that is heard by surgeons who have not yet embarked upon TEES is that TEES has a steep learning curve. While that may have been absolutely true in the early days of TEES,

any “hurdles” to learning TEES have become much lower over time for both the novice ear surgeon and the experienced ear surgeon who has not yet embarked upon learning TEES.  While TEES is characterized by the need to perform one-handed surgery and its 2D view, any surgeon who has experience performing endoscopic sinus surgery (ESS) will have a good head start on these and other aspects of TEES which they should then supplement with an in-depth study of the internal ear anatomy. Such study should be accompanied by rigorous practice on cadavers and/or 3D printed models as well as observation of and guidance from experienced TEES surgeons. Observation of TEES procedures is actually made easier by the fact that both the surgeon and any observers can simultaneously see the same view of the surgery as it is performed which greatly facilitates the teaching of TEES. Thus, a step-by-step approach to both the theory and practice of TEES should ensure that any competent ear surgeon can become a competent TEES surgeon.

1.4.2 Heads-up Surgery One of the big differences between MES and TEES is the posture assumed by the surgeon. Some surgeons may find looking up at the video monitor rather than down through a microscope a bit disconcerting in the beginning and take some time to get used to this difference. However, the heads-up posture of TEES is more ergonomically sound than the posture of MES which requires a more rigid posture that is harder to maintain over the course of a long surgical procedure [6, 7]. Moreover, MES is starting to also move in the direction of heads-up surgery with the introduction of the exoscope.

1.4.3 Resources in the Literature A wide range of resources are available for surgeons interested in TEES. Among our recommendations are Endoscopic ear surgery—principles,

1  Innovations in Endoscopic Ear Surgery

indications, and techniques by Livio Presutti and Daniele Marchioni [8] and TEES Surgical Atlas by Seiji Kakehata for Japanese readers [9] (which will also soon be published in Chinese). An excellent primer on getting started in TEES is an article which was written by Ryan et al. and provides a detailed step-by-step guide to learning TEES [10]. We also recommend checking the references listed for each of the sections herein.

1.4.4 Face-to-Face Resources In addition to resources in the literature, any aspiring TEES surgeon would be well advised to take advantage of the many opportunities to meet up with the growing community of TEES surgeons. This community strives to promote TEES and warmly welcomes newcomers.

1.4.4.1 International Working Group on Endoscopic Ear Surgery (IWGEES) The International Working Group on Endoscopic Ear Surgery (IWGEES) was, as stated above, established in 2008 with the stated goals of developing and improving endoscopic ear surgery in conjunction with the microscope. The IWGEES works year-round to promote and facilitate discussion on the latest in endoscopic ear surgery, and its home page (https://iwgees.org/) is a good place to start when looking for information and gatherings on endoscopic ear surgery. We also encourage all to become a member of the IWGEES. 1.4.4.2 World Congress on Endoscopic Ear Surgery The first World Congress on Endoscopic Ear Surgery was held in 2015  in Dubai, the second was held in Bologna in 2017, the third was held in Boston in 2019, and the fourth World Congress on Endoscopic Ear Surgery is scheduled from April 8th to the 10th of 2021  in Kyoto, Japan. This World Congress brings together experts on endoscopic ear surgery to promote its continued advancement, growth, and acceptance.

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1.4.4.3 Hands-on Seminar in Yamagata One of the best ways to get an idea of the benefits of TEES is the annual Hands-on Seminar in Yamagata, Japan. This seminar is a two-day event which offers attendees the opportunity to hear lectures from leaders in the field, get hands-on experience by practicing TEES using 3D printed models, observe several live surgeries, and last, but not least, enjoy a night at a traditional Japanese hot spring! The 9th annual seminar should be held in the late spring or early summer of 2020.

1.5

 oving Forward and into M the Future

The purpose of this book, Innovations in Endoscopic Ear Surgery, is to provide a peek into the future of TEES as it continues to develop and evolve. With TEES now entering its maturation phase, innovations are appearing that not only build upon what has become standard practice, but also expand into new and exciting directions. This book is designed to provide a guide to the future of TEES.

References 1. De Groen PC. History of the endoscope [scanning our past]. Proc IEEE. 2017;105(10):1987–95. 2. Nomura Y.  Effective photography in otolaryngology e head and neck surgery: endoscopic photography of the middle ear. Otolaryngol Head Neck Surg. 1982;90:395e398. 3. Thomassin JM, Korchia D, Duchon Doris JM.  Endoscopic-guided otosurgery in the prevention of residual cholesteatomas. Laryngoscope. 1993;103(8):939–43. 4. Tarabichi M.  Endoscopic management of acquired cholesteatoma. Am J Otol. 1997;18(5):544–9. 5. Tarabichi M.  Endoscopic management of limited attic cholesteatoma. Otolaryngol Head Neck Surg. 1999;121(2_suppl):195. 6. Vijendren A, Devereux G, Tietjen A.  The Ipswich microbreak technique to alleviate neck and shoulder discomfort during microscopic procedures. Appl Ergon. 2018. https://doi.org/10.1016/j.apergo.2018.04.013. 7. Vijendren A, Devereux G, Kenway B. Effects of prolonged microscopic work on neck and back strain amongst male ENT clinicians and the benefits of a prototype postural support chair. Int J Occup Saf

4 Ergon. 2017;1:1–10. https://doi.org/10.1080/108035 48.2017.1386411. 8. Presutti L, Marchioni D.  Endoscopic ear surgery  – principles, indications, and techniques. New  York: Thieme; 2015.

S. Kakehata 9. Kakehata S.  TEES surgical atlas. Tokyo: Nakayama Shoten; 2018. 10. Ryan P, Wuesthoff C, Patel N.  Getting started in endoscopic ear surgery. J Otol. 2018. https://doi. org/10.1016/j.joto.2018.10.002.

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The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach Seiji Kakehata and Tsukasa Ito

2.1

Introduction

While the endoscope plays the starring role in transcanal endoscopic ear surgery (TEES), TEES has a supporting cast of equipment that have helped guarantee its success, particularly the 3-charged-coupled device (CCD) camera and more recently the complementary metal-oxide semiconductor (CMOS) cameras connected to video monitors. These cameras and monitors, which were originally high definition (HD) and more recently ultra HD or 4K, combine to produce clear images that allow surgeons to confidently perform transcanal surgery with an endoscope within the delicate anatomical structures of the middle ear. However, indications for removal of cholesteatomas by TEES are generally considered to be limited to the tympanic cavity and inferior portion of the attic. Those cholesteatomas located beyond the inferior portion of the attic had been considered outside the reach of TEES. Instead such cholesteatomas still continue to be removed, even by TEES surgeons, via microscopic ear surgery (MES) with its invasive retroauricular incision and extensive temporal bone removal. However, S. Kakehata (*) · T. Ito Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Yamagata University, Yamagata, Japan e-mail: [email protected]; [email protected]

as in the past, technical advances in outside fields allowed us to expand the indications for TEES.  These advances, once again, include advances in digital imaging technology in the field of MRI imaging which facilitate pinpointing the anatomical location of a cholesteatoma during the preoperative diagnosis, as well as advances in surgical tool technology incorporating ultrasonic aspiration and improvements in surgical drills. The practical application of these advances has allowed us to move beyond the reach of the original TEES procedure, or what we call herein “non-powered” TEES and move deeper into the middle ear. Our department now has three different options from which to choose when performing TEES: non-powered TEES which because of the physical limitations of the endoscope can only be performed up to the aditus ad antrum; powered TEES which has extended the reach of TEES beyond the posterior end of the lateral semicircular canal (LSC) up to superior portion of the Donaldson’s line, or more specifically the antrum; and a third “dual MES/TEES approach” which incorporates both MES and non-powered TEES for those cholesteatomas. This chapter will first focus on clearly defining and comparing the anatomical indications for removal of cholesteatomas by non-powered TEES, powered TEES, and the dual MES/TEES approach. This discussion will be followed by an introduction to the diagnostic technology of color mapped fusion imaging (CMFI) which takes MRI

© Springer Nature Singapore Pte Ltd. 2020 S. Kakehata et al. (eds.), Innovations in Endoscopic Ear Surgery, https://doi.org/10.1007/978-981-13-7932-1_2

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images and converts them into a CMFI to allow surgeons to preoperatively determine to what extent a cholesteatoma extends beyond the inferior portion of the attic. This degree of diagnostic precision had been previously been difficult, if not impossible. The next topic will be the powered instruments of the Sonopet® Ultrasonic Aspirator (UST-2001 (Stryker, Kalamazoo, Michigan USA)) and the Visao® High-Speed Otologic Drill (Medtronic, Minneapolis, Minnesota, USA) with a high-speed curved burr incorporating a unique non-rotating outer sheath. These tools make it possible to safely remove cholesteatomas via powered TEES. The surgical procedure itself for powered TEES and the dual MES/TEES approach will then be explained in depth. The details of the surgical setup and safety issues for TEES, in general, and powered TEES, in particular, are dealt with in Chap. 3.

2.2

 he Anatomy of the Middle T Ear and Indications for TEES

2.2.1 M  ES vs. TEES in the Removal of Middle Ear Cholesteatomas When a cholesteatoma is removed via MES, the most important preoperative information is simply that a cholesteatoma is present, its general anatomical location, and the condition of the middle ear and inner structures. The location information is important not in determining whether a cholesteatoma can or should be removed by MES,

but rather to make sure that all hidden areas in the vicinity of the cholesteatoma are checked as much as possible for remnants. In contrast, determining whether a cholesteatoma can be removed by TEES, and in particular, powered TEES, requires much more precise information on the anatomical location than that for MES. While the anatomy of the middle ear has been described in depth, some of the anatomical terminology differs for the space within the middle ear depending on the source which has resulted in some inconsistency in the literature and references. This inconsistency is particularly apparent when looking at the terminology related to the attic, antrum, and mastoid. However, a higher degree of anatomical precision and agreed upon terminology is required when physicians are deciding among themselves whether a patient is indicated for non-powered TEES, powered TEES, or the dual MES/TEES approach.

2.2.2 Definitions of the Space in the Middle Ear Figure 2.1 shows the PTAM system which we have used to classify middle ear cholesteatomas. This PTAM system was developed by the Japan Otological Society (JOS) in 2010 [1] and subsequently updated in 2015 [2]. The PTAM system divides the tympanomastoid space into four sections where the protympanum is P; the tympanic cavity is T; the attic is A; and the mastoid is M. As an aside, it should be noted here that a new

Fig. 2.1  The PTAM system for staging and classification of middle ear cholesteatomas [2] P: Protympanum T: Tympanic cavity A: Attic M: Mastoid

2  The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach Fig. 2.2  The EAONO/ JOS joint consensus statements on the definitions, classification, and staging of middle ear cholesteatoma [3]

Fig. 2.3  A revised PTAM staging and classification system for middle ear cholesteatomas designed specifically for powered TEES

s­ uperseding STAM system as shown in Fig. 2.2 was developed by the European Academy of Otology & Neuro-Otology (EAONO) and JOS as a consensus system [3]. The STAM system differs in that the protympanum is replaced by a supratubal S1 site and a posterior portion of the original T site has been replaced by a tympanic sinus S2 site. Both of the S sites are defined as difficult to access sites. However, these changes, while significant, are largely unrelated to our purposes herein and we shall use the PTAM system herein with a caveat as described below. This caveat is in response to a vexing problem which is presented by both the PTAM and STAM systems in the context of powered TEES.  The problem is that these systems define the attic and the mastoid but do not delineate the antrum. This lack of clarity related to the antrum is also found in textbooks where the same textbook can refer to the “mastoid and the antrum” and also define the mastoid as consisting of three regions including

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P: Protympanum T: Tympanic cavity A: Attic M: Mastoid S1: Supratubal recess S2: Sinus tympani

P: Protympanum T: Tympanic cavity A: Attic M: Mastoid An: Antrum CM: Central mastoid

the mastoid antrum, central mastoid tract, and mastoid air cells [4]. Tos uses the term “central mastoid” and describes it as “the central area, which extends from the antrum down to the mastoid tip” [5]. Up until now, this ambiguity and/or the contradictions surrounding the definition of the space which constitutes the antrum did not present any practical problems from a surgical perspective and could largely be ignored, particularly as related to MES procedures. However, powered TEES is defined as allowing removal of cholesteatomas in the antrum and thus, it behooves us to clearly define what we mean by the antrum within the context of powered TEES as a way of eliminating any confusion. One method which was considered was dividing the mastoid space as defined in the PTAM system as M1 and M2, but we felt that the term antrum best described the space which is targeted. Thus, Fig. 2.3 shows a revised PTAM staging and classification system for middle ear cholesteatomas

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designed specifically for powered TEES.  The mastoid (M) space has been extended and subdivided into two regions with the upper region defined as the antrum (An) and the lower region defined as the central mastoid (CM).

2.2.3 Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach Indications We treat the majority of patients with cholesteatomas with one of the three aforementioned TEES procedures: non-powered TEES, powered TEES, or dual MES/TEES approach. The specific approach will typically be decided upon during the presurgical planning; however, a surgeon always has the option during surgery of switching from non-powered TEES or powered TEES to a dual MES/TEES approach or even just MES.

2.2.4 Indications for Non-powered TEES Non-powered TEES is not a general term used in the literature and is used herein to refer to what is typically simply called TEES. We have adopted the term non-powered TEES in this specific text so as to clearly distinguish it from powered TEES. The indications for the removal of cholesteatomas by non-powered TEES are cholesteatomas which are restricted to the protympanum (P), tympanic cavity (T), or inferior portion of the attic (A) as shown in Fig.  2.4. Fig. 2.4 The indications for the removal of cholesteatomas by non-powered TEES

S. Kakehata and T. Ito

Such cholesteatomas do not require the use of any powered instruments and instead can be removed under direct endoscopic visualization with a curette, chisel, and hammer to remove the necessary bone. A  wealth of information is available in the literature on this standard TEES procedure [6–9].

2.2.5 Indications for Powered TEES The indications for powered TEES are those cholesteatomas which extend beyond the inferior portion of the attic (A) into the superior portion of the attic (A) through to the antrum (An) up to the Donaldson’s line as shown in Fig. 2.5. We began performing powered TEES in 2011 and our first report in the literature was in 2013 [10] although it should be noted that the term “powered TEES” was not used in the original paper.

2.2.6 Indications for the MES/TEES Dual Approach The term “dual approach” has ironically a double meaning in that dual refers to the two types of surgical procedures which are employed, microscopic and endoscopic. However, dual also refers to the fact that this procedure uses two “ports,” a transmastoid port made possible by MES and a transcanal port made possible by TEES.  This dual approach will utilize both a transcanal approach using an endoscope and a retroauricular

P: Protympanum T: Tympanic cavity A: Attic M: Mastoid An: Antrum CM: Central mastoid

2  The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach Fig. 2.5 The indications for the removal of cholesteatomas by powered TEES

Fig. 2.6 The indications for the removal of cholesteatomas by the MES/TEES dual approach

approach using a microscope, an endoscope, or both a microscope and endoscope. The specifics of this surgical procedure will be described in Sect. 2.5.2. The indications for the MES/TEES dual approach are those cholesteatomas which extend beyond both the Donaldson’s line and the posterior end of the LSC and the central mastoid (CM) as shown in Fig. 2.6. We employ this dual approach rather than simply an MES procedure, because it allows a canal wall up (CWU) procedure. Furthermore, the dual transcanal and transmastoid approaches using an endoscope facilitate better removal of matrix of the cholesteatoma in the attic, especially the lower tegmen, under direct visualization with no additional burden placed on the patient. The ultimate objectives of incorporating the endoscope into what is often done exclusively via MES are to cut down on the invasiveness, allow maximum preservation of the mastoid mucosa and minimize bone loss incurred by typical MES and reduce the occurrence of residual as well as recurrent cholesteatomas.

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P: Protympanum T: Tympanic cavity A: Attic M: Mastoid An: Antrum CM: Central mastoid L: Lateral semicircular canal D: Donaldsons line

P: Protympanum T: Tympanic cavity A: Attic M: Mastoid An: Antrum CM: Central mastoid L: Lateral semicircular canal D: Donaldsons line

2.2.7 Indications for Pediatric Patients A further consideration is the age of the patient. Initially, children were contraindicated for TEES. However, the advantages offered by TEES of minimal bone loss and no external scarring were particularly appealing for children and their parents. We determined that the circumference of the external auditory canal (EAC) is not a barrier to TEES in children and gradually expanded indications to children with the proviso that we would switch over to MES at the first sign of trouble [11]. Fortunately, at present, the need to switch over has never become an issue.

2.2.8 Contraindications Non-powered and powered TEES are contraindicated for LSC fistulas, wide exposure of the dura, and infiltrative cholesteatomas. These conditions are typically treated using the dual MES/TEES approach or canal wall down (CWD).

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2.3

Identification of Location of Cholesteatomas

2.3.1 Preoperative Diagnostic Imaging Procedures for Cholesteatomas 2.3.1.1 Standard Preoperative Diagnostic Imaging Procedures for Cholesteatomas The standard diagnostic procedure for diagnosing a cholesteatoma is that once a patient is suspected of having a cholesteatoma based on visual examination via either a microscope or endoscope, they undergo a CT scan. However, while the CT scan will reveal shadows suggestive of soft tissue density masses that are likely to be a cholesteatoma and the condition of the middle and inner ear bony structure, CT images do not provide sufficient information on the extent of the cholesteatoma within the middle ear. Figure 2.7 is a typical CT image where a soft tissue density mass is clearly present, but an accurate diagnosis is essentially impossible due to poor image quality. This lack of precision is typically not a problem if the cholesteatoma is to be removed via MES. MES does not require detailed location information because the size of the

r­etroauricular incision and amount of bone removal is the same for all procedures. Nonpowered TEES is generally restricted to those cholesteatomas which can be visually confirmed prior to surgery by an endoscopic examination. In contrast, powered TEES does require more precise anatomical location as to whether an attic lesion extends into the antrum or even beyond the LSC and whether a soft tissue density mass that might be in the superior portion of the attic or antrum on a CT scan is a cholesteatoma. These requirements lead us to develop a different diagnostic imaging approach as described below.

2.3.1.2 Preoperative Diagnostic Imaging Procedures for Cholesteatomas to Be Treated by Powered TEES Our own standard preoperative diagnostic imaging procedure for any cholesteatoma is initially the same as any other institution. We start with a visual examination via a microscope or endoscope in our outpatient clinic and if a suspicious mass is observed, then a CT scan is performed. However, we follow up every CT scan by performing an MRI and creating two types of CMFIs as described below.

2.3.2 CMFI as a Preoperative Diagnostic Imaging Tool

Fig. 2.7  Poor image quality CT image with a soft tissue density mass

CMFIs have become an essential part of our preoperative diagnosis of cholesteatomas. We developed CMFI in 2012 [12–14] and it has become an essential part of our presurgical diagnosis of cholesteatomas, particularly when deciding whether powered TEES is indicated. The two types of CMFI are (1) a non-echo planar imaging (non-­ EPI) diffusion-weighted imaging (DWI) CMFI and (2) a T1-weighted image (T1WI) CMFI which are both created simultaneously as part of the MRI process [15–23]. Looking at the first type of CMFI, the nonEPI DWI CMFI uses non-EPI DWI as opposed to echo planar imaging (EPI) DWI because while EPI DWI had been as tool in diagnosing

2  The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach non-EPI DWI

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EPI DWI

Fig. 2.8  EPI DWI image vs. non-EPI DWI for diagnosing a cholesteatoma

cholesteatomas, EPI DWI images present real diagnostic challenges due to image distortion which makes pinpointing the exact anatomical location guesswork. Due to this fatal flaw from the perspective of powered TEES, we use nonEPI DWI which offers greater accuracy in the identification of cholesteatomas than EPI (Fig. 2.8) [12–14]. Yet even a non-EPI DWI image presents challenges in determining the anatomical extent of a cholesteatoma due to the lower image resolution and disappearance of most intracranial structures. These drawbacks can be overcome by further processing of the non-EPI DWI MRI by fusing the images using magnetic resonance cisternography (MRC) and finally color mapping as shown in Fig. 2.9 using a 3.0-T MR unit (Achieva, Royal Philips Electronics Inc., the Netherlands). This resulting image is a non-EPI DWI CMFI and it reveals the presence of a possible cholesteatoma as indicated by a high intensity red region in the area of the middle ear. However, such red regions could also be a cholesterin granuloma. To rule out a cholesterin granuloma, the T1WI CMFI is simultaneously

Fig. 2.9  Non-EPI DWI CMFI with the presence of a possible cholesteatoma indicated by a high intensity red region in the area of the middle ear

created. This second type of CMFI can differentiate a cholesteatoma from a cholesterin granuloma because a cholesteatoma appears as a high intensity region on a DWI (Fig. 2.10a) and low intensity region on a T1WI (Fig. 2.10b), while a cholesterin granuloma appears as a high intensity region on both DWI (Fig.  2.10c) and T1WI (Fig. 2.10d).

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a

b

c

d

Fig. 2.10  Comparison between a CMFI DWI and CMFI T1WI (a) where the cholesteatoma appears as a high intensity region on a DWI and (b) as low intensity region

on a T1WI, while a cholesterin granuloma appears as a high intensity region on both (c) DWI and (d) T1WI

2  The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach

2.3.3 Postoperative Diagnostic Imaging Procedures for Cholesteatomas An essential part of the follow-up is conducting diagnostic imaging in order to check for residual or recurrent cholesteatomas. The standard protocol is to perform a CT scan, but Khemani et al. [19] have recently reported that DWI is a more reliable follow-up imaging method than a CT scan after cholesteatoma surgery. Our work and that of others in this area have shown that non-­ EPI DWI is an excellent tool for detecting recurrent cholesteatomas that are larger than 3 mm in size [7, 8, 11, 15–17]. Our own follow-up protocol is designed to maximize both accuracy and cost-efficiency. The patient comes in for an initial CT scan 6 months after surgery and if no soft tissue masses, subsequent follow-up is done with CT scans alone. If a soft tissue mass is found on the initial CT scan or any subsequent CT scans, a CMFI is created using non-EPI DWI 6 months later to determine whether the mass is a postoperative change such as scarring. T1WI is also performed at this time to determine whether any visible mass is a cholesteatoma or cholesterin granuloma.

2.4

Powered Instruments

The endoscope had not been used in the superior portion of the attic and the antrum due to shortcomings of the endoscope, but rather because of the difficulties and dangers of using a conventional rotating drill to remove the bone of the lateral canal wall into the antrum and manipulating it with one hand. Such drills can catch meatal skin which can pull in and damage delicate anatomical structures. Thus, a conventional drill cannot be used in any procedure which extends into the superior portion of the attic and the antrum. Our department, however, worked to extend the indications for TEES to include the superior portion of the attic and antrum by incorporating the two powered-instruments mentioned above: the Sonopet® Ultrasonic Aspirator which has

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opened the door to safely expanding indications for TEES through the superior area of attic and into the antrum and the Visao® High-Speed Otologic Drill with its curved burr and unique non-rotating outer sheath.

2.4.1 Sonopet® Ultrasonic Aspirator 2.4.1.1 Use of the Sonopet® Ultrasonic Aspirator The Sonopet® is not used in the removal of cholesteatomas in non-powered TEES.  However, the Sonopet®, in combination with the Visao® curved burr, makes it possible to safely remove cholesteatomas in the superior portion of the attic and the entire antrum. This Sonopet® is essential in expanding the indications through to the antrum. The Sonopet® offers three separate functions in a single handpiece: bone removal, irrigation, and aspiration (Fig.  2.11). While the combination of these three functions together is great for one-­handed TEES, the unique ultrasonic bone removal function is what opens the door to previously untreatable regions of the middle ear by TEES. The Sonopet® does not actually cut into bone, but instead the ultrasonic vibrations cause bone to fragment and emulsify while generally preserving other surrounding types of tissues such as skin and muscle. This ability of the Sonopet® to selectively remove bone allows surgeons to safely operate and open a path to the antrum. This multifunctionality makes it an ideal tool for use in the one-handed surgery of TEES.  The Sonopet® has  a longitudinal–torsional compound vibration  (LT-vibration) when used with its H201 tip  as well as simple longitudinal vibration (L-vibration). This non-rotating motion of the

Fig. 2.11  The Sonopet® Ultrasonic Aspirator

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Sonopet® prevents damage to the tympanomeatal flap or other soft tissue, which a standard surgical drill can cause. The history and use of the Sonopet® is explained in greater detail in Chap. 3.

2.4.1.2 Development of a Dedicated Sonopet® for TEES The conventional Sonopet® used for bone removal consists of a universal angled-handpiece 25MA and a H201 tip with a rigid tip cover. Unfortunately, this conventional Sonopet® design presents some drawbacks when performing TEES.  Specifically, the angled-handpiece 25MA which is held in the right hand interferes with the endoscope which is held in the left hand and the H201 tip cover is thicker than necessary for the TEES keyhole surgery. We thus helped to develop a new Sonopet® for powered TEES in cooperation with Stryker Corporation. The dedicated Sonopet® for TEES consists of a universal straight handpiece 25MS and a H101 tip which is a little shorter than the H201 tip and covered with a thinly tapered tip cover. This redesigned Sonopet® is optimized for TEES and makes it easier to perform pediatric patients with a narrow EAC.  Unfortunately, the H101 tip is currently only sold in Japan.

2.4.2 Visao® High-Speed Otologic Drill with Curved Burr and Unique Non-rotating Outer Sheath While the Sonopet® does selectively remove bone, it is still essential to protect the delicate anatomical structures of the ossicular chain and facial nerve from any possible damage. The Visao® curved burr with a 2-mm diameter is used to create a thin bony plate and polish the edge of an atticotomy or atticoantrotomy. The curved shape of this drill is suitable for the keyhole surgery of TEES.  Moreover, the curved burr has a non-rotating thin outer sheath and this lack of rotation greatly enhances safety (Fig.  2.12) ensuring that it does not catch on tissue or other anatomical structures.

Fig. 2.12 Visao® High-Speed Otologic Drill with curved burr and unique non-rotating outer sheath

2.5

Surgical Procedures

2.5.1 Powered TEES The presurgical preparation is essentially the same for non-powered TEES and powered TEES as is described in Chap. 3. The initial surgical steps are also essentially the same for non-­ powered TEES and powered TEES and many good references are available which describe non-powered TEES [6–9]. We described the surgical procedure for powered TEES in our initial paper beginning with the use of general anesthesia combined with a local anesthesia which is applied to the bony ear canal. Skillful administration of both the general and local ­ anesthesia can help to minimize bleeding which goes a long way toward taking advantage of the superior visualization offered by the HD 3-CCD camera and HD monitor. The skin of the ear canal is elevated by making a circumferential incision medially in the bony ear canal using a round knife (Fig. 2.13). This incision creates a tympanomeatal flap which is also elevated anteriorly to create an unobstructed view of the tympanic cavity all the way to the retrotympanum (Fig. 2.14). The next step is to visually inspect the tympanic cavity for the presence of any matrix which should be elevated. The steps taken up until this point are exactly the same as  those taken for a non-powered TEES procedure.

2  The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach

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Fig. 2.13  Elevation of the skin of the ear canal by making a circumferential incision medially in the bony ear canal using a round knife

Fig. 2.15 Insertion of the Sonopet® to start an atticotomy

Fig. 2.14  Elevated tympanomeatal flap creating an unobstructed view of the tympanic cavity all the way to the retrotympanum

Fig. 2.16  Thinning of bony plate with Visao® High-­ Speed Otologic Drill with curved burr

Powered TEES begins with the use of the Sonopet® to start an atticotomy (Fig. 2.15) which involves removing the bone of the lateral canal wall and opening up access to the superior area of the attic into the antrum. A critical part of the powered TEES procedure is leaving a bony plate over the ossicular chain along the lateral canal wall of the attic and antrum. This plate is thinned by the Visao® curved burr and its purpose is to ensure that the Sonopet® and Visao® curved burr do not come into contact with and damage the

delicate structures of the ossicular chain and facial nerve. The purpose of the thinning by the Visao® curved burr to facilitate ease of its removal once all bone removal is just about finished (Fig. 2.16). At that point, the plate can be carefully removed with a gentle tap of a chisel by a hammer along with cutting of any remaining bone with a curette. The Visao® curved burr is once again used to smooth any jagged edges and widen the opening until the edge of the cholesteatoma can be seen. Once the cholesteatoma edge is visible, the matrix is elevated from the antrum

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Fig. 2.17 Visible cholesteatoma edge with elevated matrix from the antrum to attic

Fig. 2.19  Performing scutumplasty to reconstruct the ossicular chain and bony canal wall using cartilage with perichondrium harvested from the tragus

Fig. 2.18  Creation of anterior ventilation route

Fig. 2.20  Repositioning of tympanomeatal flap to its original location

to attic taking care to leave the mucosa intact (Fig.  2.17). The cholesteatoma matrix from the antrum is completely removed with the matrix from the mesotympanum. After removal of the cholesteatoma, an anterior ventilation route is made to prevent cholesteatoma recurrence (Fig.  2.18). A scutumplasty is performed to reconstruct the ossicular chain and bony canal wall using cartilage with perichondrium harvested from the tragus (Fig. 2.19). The tympanomeatal flap is repositioned into its original location (Fig. 2.20), and then, the EAC is packed with chitin sheets, Gelfoam sponges soaked in antibiotic eardrops, and Merocel sponges.

2.5.2 Dual MES/TEES Approach The dual MES/TEES approach is used when the cholesteatoma extends beyond the Donaldson’s line of the LSC and encroaches into the posterior end of the LSC.  The dual approach takes unique advantage of the strong points of both the MES approach and the TEES approach. The dual approach begins with nonpowered TEES which is performed to elevate any matrix up to the inferior portion of the attic. This TEES approach helps to ensure that the structures within the areas of the P, T, and A (Fig.  2.6) are carefully checked under direct

2  The TEES Lineup: Non-powered TEES, Powered TEES, and the Dual MES/TEES Approach

visualization to confirm that all matrix remnants are removed. Once the TEES portion of the procedure has been completed, a modified mastoidectomy is performed by MES as a transcortical antrotomy. The visual access provided by the dual transcanal and transmastoid ports allows us to preserve mucosa and thus ensure complete removal of debris. The dual MES/TEES approach lowers the risk of residual and recurrent cholesteatomas, particularly in adult patients, in comparison with a conventional MES procedure.

2.6

Conclusion

The lineup of non-powered TEES, powered TEES using the Sonopet® Ultrasonic Aspirator and the Visao® curved burr, and the dual MES/ TEES approach expands the range of choices for surgeons and enhances the effectiveness of cholesteatoma removal surgery.

References 1. Tono T, Aoyagi M, Ito M, et al. Staging of middle ear cholesteatoma. Otol Jpn. 2010;20:743–5. 2. Tono T, Sakagami M, Kojima H, et  al. Staging and classification criteria for middle ear cholesteatoma proposed by the Japan Otological Society. Auris Nasus Larynx. 2017;44(2):135–40. 3. Yung M, Tono T, Olszewska E, et  al. EAONO/JOS joint consensus statements on the definitions, classification and staging of middle ear cholesteatoma. J Int Adv Otol. 2017;13:1–8. 4. Schuknecht HF, Gulya AJ. Anatomy of the temporal bone with surgical implications. 3rd ed. New  York: Informa Health Care USA; 2007. p. 116–23. 5. Tos M. Manual of middle ear surgery. Vol. 2 Mastoid surgery and reconstructive procedures. New  York: Thieme Medical Publishers; 1995. p. 258–60. 6. Tarabichi M.  Endoscopic management of acquired cholesteatoma. Am J Otol. 1997;18:544–9. 7. Tarabichi M.  Endoscopic management of limited attic cholesteatoma. Laryngoscope. 2004;114: 1157–62. 8. Marchioni D, Mattioli F, Alicandri-Ciufelli M, et  al. Endoscopic approach to tensor fold in patients with attic cholesteatoma. Acta Otolaryngol. 2009;129:946–54.

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9. Presutti L, Marchioni D.  Endoscopic ear surgery  – principles, indications, and techniques. New  York: Thieme; 2015. 10. Kakehata S, Watanabe T, Ito T, et  al. Extension of indications for transcanal endoscopic ear surgery using an ultrasonic bone curette for cholesteatomas. Otol Neurotol. 2014;35:101–7. 11. Ito T, Kubota T, Watanabe T, et al. Transcanal endoscopic ear surgery for pediatric population with a narrow external auditory canal. J Laryngol Otol. 2016;130(S3):S101. 12. Kanoto M, Sugai Y, Hosoya T, et  al. Detectability and anatomical correlation of middle ear cholesteatoma using fused thin slice non echo planar imaging diffusion-weighted image and magnetic resonance cisternography (FTS-nEPID). Magn Reson Imaging. 2015;33(10):1253–7. 13. Watanabe T, Ito T, Furukawa T, et  al. The efficacy of color mapped fusion images in the diagnosis and treatment of cholesteatoma using transcanal endoscopic ear surgery. Otol Neurotol. 2015;36(5):763–8. 14. Watanabe T, Ito T, Furukawa T, et al. The efficacy of color mapped diffusion weighted images combined with CT in the diagnosis and treatment of cholesteatoma using transcanal endoscopic ear surgery. Otol Neurotol. 2015;36(10):1663–8. 15. Más-Estellés F, Mateos-Fernández M, Carrascosa-­ Bisquert B, et  al. Contemporary non-echo-planar diffusion-weighted imaging of middle ear cholesteatomas. Radiographics. 2012;32:1197–213. 16. Dremmen MH, Hofman PA, Hof JR, et  al. The diagnostic accuracy of non-echo-planar diffusion-­ weighted imaging in the detection of residual and/or recurrent cholesteatoma of the temporal bone. AJNR Am J Neuroradiol. 2012;33:439–44. 17. Jindal M, Riskalla A, Jiang D, et  al. A systematic review of diffusion-weighted magnetic resonance imaging in the assessment of postoperative cholesteatoma. Otol Neurotol. 2011;32:1243–9. 18. Yamashita K, Yoshiura T, Hiwatashi A, et  al. Detection of middle ear cholesteatoma by diffusionweighted MR imaging: multishot echo-planar imaging ­compared with single-shot echo-planar imaging. AJNR Am J Neuroradiol. 2011;32:1915–8. 19. Khemani S, Singh A, Lingam RK, et al. Imaging of postoperative middle ear cholesteatoma. Clin Radiol. 2011;66:760–7. 20. Schwartz KM, Lane JI, Bolster BD Jr, et al. The utility of diffusion-weighted imaging for cholesteatoma evaluation. AJNR Am J Neuroradiol. 2011;32:430–6. 21. Schwartz KM, Lane JI, Neff BA, et  al. Diffusion-­ weighted imaging for cholesteatoma evaluation. Ear Nose Throat J. 2010;89:E14–9. 22. Baráth K, Huber AM, Stämpfli P, et al. Neuroradiology of cholesteatomas. AJNR Am J Neuroradiol. 2011;32:221–9. 23. Bammer R.  Basic principles of diffusion-weighted imaging. Eur J Radiol. 2003;45:169–84.

3

Setup and Safety of Powered TEES Tsukasa Ito and Seiji Kakehata

3.1

Introduction

3.2

Equipment

This chapter will expand on Chap. 2 which focused on powered transcanal endoscopic ear surgery (TEES) by looking at the surgical setup and safety concerns related primarily to powered TEES as well as what was referred to in Chap. 2 as “non-powered TEES.” To reiterate “non-­powered TEES” is not a general term used in the literature and is used here to refer to what is typically simply called TEES.  Successful TEES, in general, and powered TEES, specifically, requires careful preparation including procuring the proper equipment together with properly positioning and preparing that equipment, the surgical staff, and the patient. The safety issues which also need to be addressed for powered TEES include proper use of the powered instruments within the middle ear, heat generation of light sources, and the potential impact of skull vibrations generated by these powered instruments.

Non-powered TEES requires endoscopes, a camera/imaging system, sufficient illumination, and a standard surgical tool set for microscopic ear surgery (MES) together with additional curved dissectors (Fig.  3.1), curved suction tools (Fig.  3.2), and finer forceps than are typically used in MES (Fig.  3.3). These additional tools facilitate access into the hidden recesses. Powered TEES also requires the two powered instruments of the Sonopet® Ultrasonic Aspirator (Stryker Corporation, Kalamazoo, Michigan, USA) which comes with a standard console (UST-2001)

T. Ito (*) · S. Kakehata Department of Otolaryngology, Head and Neck Surgery, Faculty of Medicine, Yamagata University, Yamagata, Japan e-mail: [email protected]; [email protected]

Fig. 3.1  Surgical tools used in TEES from top to bottom: Thomassin single curved dissector (Karl Storz Endoscopy Japan K.K., Tokyo, Japan); Thomassin double curved dissector (Karl Storz Endoscopy Japan K.K., Tokyo, Japan); elevator (Daiichi Medical Co., Ltd., Tokyo, Japan); and round knife (Medtronic Japan Co., Ltd., Tokyo, Japan)

© Springer Nature Singapore Pte Ltd. 2020 S. Kakehata et al. (eds.), Innovations in Endoscopic Ear Surgery, https://doi.org/10.1007/978-981-13-7932-1_3

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a

b

Fig. 3.2  Curved suction tubes which were bent in-house to the appropriate angles

Fig. 3.4 (a) The Sonopet® Ultrasonic Aspirator: universal angled-handpiece 25MA (top) and the universal straight-handpiece 25MS (bottom) (Stryker Corporation, Kalamazoo, Michigan, USA). (b) The Sonopet® Ultrasonic Aspirator console is shown on the right (UST-­ 2001, Stryker Corporation, Kalamazoo, Michigan, USA)

angles of view are 0°, 30°, 45°, and 70°; and the standard lengths are 10, 14, and 18 cm. No matter what endoscope is used, an endoscope will provide a wider angle of view within the middle ear in comparison to a microscope. It should also be noted that (Fig. 3.4) and various handpieces and tips which not all possible combinations of diameter, angle, will be discussed in section “The Sonopet® and length are available among endoscopes on the Ultrasonic Aspirator for Use in Powered TEES” market. While our unit initially performed TEES and the Visao® High-Speed Otologic Drill with three endoscopes with angles of view at 0°, (Medtronic Inc., Minneapolis, Minnesota, USA) 30°, and 70°, we now almost exclusively perform with a high-speed curved bur and unique non-­ TEES with just two endoscopes which both have a rotating outer sheath (Fig. 3.5) which will be dis- 2.7-mm diameter and length of 18 cm but differ in cussed in section “Visao® High-Speed Otologic the angle of view at either 0° or 30° (Fig. 3.6). The Drill with a Curved Burr.” majority of each surgical procedure is performed using the 0° endoscope, while the 30° endoscope is primarily used to do a final check of the more hid3.2.1 The Endoscope den recesses of the middle ear to ensure that all pathologies have been removed. The centerpiece of TEES is the Hopkins rod-lens However, it should be noted that many, if not endoscope which is currently available in different most, surgeons performing TEES today use a 3.0diameters, angles of view, and lengths. The standard mm endoscope. Pothier states that he prefers a 3.0diameters are 2.7, 3.0, and 4.0  mm; the standard mm endoscope because the larger diameter Fig. 3.3  Forceps which are finer than typical forceps with good gripping power (Medtronic Japan Co., Ltd., Tokyo, Japan)

3  Setup and Safety of Powered TEES

a

21

b

c

Fig. 3.5 (a) Visao® High-Speed Otologic Drill (Medtronic Inc., Minneapolis, Minnesota, USA) with a high-speed curved burr and unique non-rotating outer

sheath. (b) A close-up of the 2.0-mm burr. (c) View of the Visao® drill in use during surgery

the narrow confines of the external auditory canal (EAC). Our department has conducted measurements of the osseous external auditory canal (OEAC) in patients who have successfully undergone TEES and the narrowest diameter was 3.4 mm in a group of children and adults with that 3.4 mm figure actually from an adult. This figure is not only extremely close to the diameter of a 3.0mm endoscope but would also rule out the use of a 4.0-mm endoscope [3]. Fig. 3.6  A 0° 2.7-mm endoscope (top) and 30° 2.7-mm endoscope (bottom) (Karl Storz Endoscopy Japan K.K., Tokyo, Japan) used in our department when performing TEES

provides a better field of view and better illumination [1]. Our unit instead prefers the 2.7-mm endoscope because we feel it still provides an excellent field of view and recent improvements in the technical specifications of the 2.7-mm endoscope have resulted in excellent illumination. Moreover, data collected on heat generation indicates that the smaller the diameter of the endoscope, the less the heat generated [2], particularly when comparing a 2.7-mm endoscope to a 4.0-mm endoscope. Furthermore, a narrower endoscope offers greater maneuverability which is extremely important in

3.2.2 Imaging System While the endoscopes which are described above have long been commercially available and are a standard instrument in nearly all surgical departments, TEES only became a viable option with the development of advanced, high quality imaging systems. The imaging system consists of two elements, the camera system and the video monitor, both of which need to be built to advanced specifications (Fig. 3.7).

3.2.2.1 3-CCD Camera The standard camera system used in TEES is a high-definition (HD) 3-charged-coupled device (CCD) camera which passes the incoming light

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a

image for TEES. We use standard commercially available 26-in HD monitors to ensure that the image can be clearly seen at a distance of slightly over one meter which represents the distance between the seated surgeon and the monitor (Fig. 3.7b).

3.2.3 Illumination b

Fig. 3.7 (a) Endoscope camera (Image 1 HDTVH3-ZA, Karl Storz Endoscopy Japan K.K., Tokyo, Japan). (b) Standard HD monitor surgical setup

through a trichroic prism assembly. This prism assembly splits light wavelengths into the corresponding three colors of red, green, and blue. A 3-CCD camera is vastly superior to a 1-CCD camera which has only a single chip or charged-­ couple device. The 1-CCD camera can process only one-third of the color information of a 3-CCD camera and it interpolates gaps in the received information. This interpolation process results in much poorer resolution in comparison to the resolution achieved with a 3-CCD camera. In particular, reds, which are critical in any surgical procedure, are poorly rendered by 1-CCD cameras and, as a result, anatomical structures and landmarks are difficult to distinguish. TEES should thus only be performed if a 3-CCD camera is available, and conversely never performed using a 1-CCD camera [4, 5].

3.2.2.2 HD Video Monitor The second essential component of the imaging system is an HD video monitor because a non­HD monitor does not provide a clear enough

While TEES requires top-of-the-line imaging equipment, TEES is performed with standard light sources. Up until recently, the most commonly used light sources were xenon; however, these xenon light sources have now generally been replaced by the newer light-emitting diode (LED) light sources. We ourselves use an LED light source (Power LED 175, Karl Storz Endoscopy Japan K.K., Tokyo, Japan) and regardless of whether a xenon or LED light source is used, TEES should only be performed at the proper settings to ensure that no thermal tissue damage occurs. We use a 30% setting for a xenon light source and a 40% setting for an LED light source. The issue of light sources, heat generation, and safety shall be discussed in greater depth in Sect. 3.5.2.

3.2.4 Surgical Tools and Materials for TEES 3.2.4.1 Surgical Tool Set As stated above, a standard surgical tool set is used for TEES with the addition of curved instruments (Fig.  3.1). These curved instruments expand the reach within the middle ear, but they must be handled with great care when inserting them into recesses around corners and even more so when removing these instruments from such recesses. We highly recommend only removing these instruments from recesses under visualization of the endoscope to ensure that delicate anatomical structures, in particular, the ossicular chain, are not damaged. 3.2.4.2 Lens Defogger While the imaging system described above provides extremely high quality images, one problem with the endoscope is that the lens can get

3  Setup and Safety of Powered TEES

a

23

b

c

Fig. 3.8 (a) Antifog agent Ultrastop® (Henke-Sass, Wolf, Tuttlingen, Germany). (b) Antifog pad Dr. Fog® (Aspen Medical Europe Ltd., Leicestershire, UK). (c) Defogging of the endoscope lens during surgery

fogged up when inserted into the ear. While this fogging of the lens cannot be prevented, it can be easily managed by regularly defogging of the lens. We use the antifog agent Ultrastop® (Henke-­ Sass, Wolf, Tuttlingen, Germany) and an antifog pad Dr. Fog® (Aspen Medical Europe Ltd., Leicestershire, UK) (Fig. 3.8). The primary surgeon should remove the endoscope when the lens becomes fogged up and the assistant surgeon will wipe the lens with the antifog pad moistened with the antifog agent (Fig.  3.8). It should be noted

that the antifog agent has been found to be ototoxic as a topical agent [6] and thus great care should be taken to use the agent sparingly and to make sure that the agent does not come into contact with tissue in the ear.

3.2.4.3 Cottonoids Despite their rather “humble” nature, cottonoids play an outsized role of importance in TEES because they can be used as a “second hand” to hold anatomical structures in place. We use two

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a A

P

T

An

M

P: protympanum T: tympanic cavity A: Attic An: Antrum M: Mastoid

Fig. 3.10  Revised system for staging and classifying of middle ear cholesteatomas to be treated by powered TEES based on PTAM system for staging and classification of middle ear cholesteatomas

b instruments facilitate access to the antrum up to the Donaldson’s line of the lateral semicircular canal (LSC) with the antrum defined as described at length in Chap. 2 (Fig. 3.10) [7].

3.2.5.1 Sonopet® Ultrasonic Aspirator

Fig. 3.9 (a) Small “handmade” cotton balls (left) and Bemsheet cottonoids (No. 3 Bemsheet, Kawamoto Corporation, Osaka, Japan) (right). (b) Use of Bemsheet cottonoids during surgery

types of cottonoids which are soaked in epinephrine at a concentration of 1:1000 and in addition to acting as a second hand, play different roles at different stages of surgery. The first type is any generic sterile non-woven gauze from which we create “handmade” cotton balls of approximately 2  mm in diameter (Fig.  3.9). These tiny cotton balls are inserted into the middle ear and play a critical role in staunching bleeding and holding structures within the ear out of the way during surgery. The second type of cottonoid is a flat sheet (No. 3 Bemsheet, Kawamoto Corporation, Osaka, Japan) which is used in the initial stage of surgery to keep the tympanomeatal flap elevated and to staunch bleeding (Fig. 3.9).

3.2.5 Powered Instruments Powered TEES is made possible by the aforementioned powered instruments: the Sonopet® Ultrasonic Aspirator and the Visao® HighSpeed Otologic Drill with a curved burr. These

The Sonopet® Ultrasonic Aspirator vs. the Ultrasonic Bone Curette (UBC) This textbook offers a perfect opportunity to clear up any confusion related to the naming and functionality of the Sonopet® Ultrasonic Aspirator (Stryker Corporation, Kalamazoo, Michigan, USA), in particular, as it relates to use and somewhat “misuse” of the term ultrasonic bone curette (UBC). It is first necessary to take a bit of a detour and review an abbreviated history of ultrasonic surgical instruments as it relates to our topic. A generic ultrasonic surgical instrument was originally made up of three parts: a console unit, foot controller pedal and handpiece with a non-­ detachable tip, and over time handpieces with different types of tips were designed for specific surgical tasks. The first generation of ultrasonic surgical instruments were the cavitation ultrasonic aspirators. Cavitation is a phenomenon where ultrasonic waves selectively target fluid including fluid in soft tissue. The original ultrasonic aspirator used for this purpose was the Cavitron Ultrasonic Surgical Aspirator or CUSA and it began to be mentioned in the literature in the late 1970s [8, 9]. Thus, the ultrasonic aspirator was originally designed for soft tissue removal coupled with irrigation and suctioning while not affecting bone. This type of ultrasonic aspirator is still a standard surgical tool and is widely used to

3  Setup and Safety of Powered TEES

remove tumors [10] such as in neurosurgery [11] and renal surgery [12]. CUSA over time became synonymous with an ultrasonic aspirator, and CUSA is often used to mean a generic ultrasonic aspirator. However, a new technology was developed in the early 2000s for use with an ultrasonic aspirator. This technology is based on handpieces with tips that vibrate at an ultrasonic frequency either longitudinally (the L mode) or with torsional oscillation (the LT mode). In contrast to cavitation, this technology does not damage soft tissue, but instead targets harder tissue such as bone which is emulsified and aspirated away. This L/ LT technology was first made available on the market in the early 2000s as the Sonopet® Omni (model UST-2001 Ultrasonic Surgical Aspirator, Stryker Corporation, Kalamazoo, Michigan, USA) which was also referred to in the literature as the ultrasonic bone curette (UBC) or the Sonopet® UBC (Miwatec Co. Ltd., Kawasaki, Japan). Again, this Sonopet® offered three functions in one handpiece: bone removal (in place of soft tissue removal), irrigation, and suctioning. Many papers are available in the literature from the early- to mid-2000s which used the name UBC and described its use to remove bone in a wide range of fields including neurosurgery [13], paranasal sinus surgery [14], maxillofacial surgery [15], and spinal surgery [16]. Confusion arises because the Sonopet® could function both as what are commonly referred to as a CUSA and what used to be referred to as a UBC based on the specific handpiece model with its non-detachable tip. The Sonopet® has different shaped handpieces which facilitate better access depending on the surgical site, for example, a straight handpiece versus a curved handpiece. However, it is the tip which determines the functionality of an ultrasonic aspirator, i.e., the cavitation of soft tissue of a CUSA or emulsification of hard bony tissue of what was commonly referred to as the UBC. Then in 2010, the design of the Sonopet® was changed with the introduction of a universal handpiece to which different tips can be attached with each tip having a specific function. It was after the introduction of this universal handpiece

25

that we began working with the Sonopet®. Our initial paper introducing powered TEES also used the designations of “ultrasonic bone curette,” UBC, and Sonopet® [17]. However, due to changes in corporate ownership, what was previously referred to as the “ultrasonic bone curette,” “UBC,” and even the “Sonopet® UBC” is now properly called the Sonopet® Ultrasonic Aspirator or simply the Sonopet®. The Sonopet® Ultrasonic Aspirator for Use in Powered TEES In the initial days of using the Sonopet® for TEES, the conventional type of the Sonopet® for bone removal consisted of the universal angled-­ handpiece 25MA and the LT mode H201 tip as well as the L mode H203 tip both of which had a rigid tip cover (Fig. 3.4). After a short period of time, we stopped using the H203 tip and used only the H201 tip because we found the LT mode to be far superior to the L mode. We also found that the angled-handpiece 25MA when held in the right hand could be difficult to manipulate around the endoscope in the left hand. In addition, the original tip cover was rather bulky when inserted into the narrow confines of the EAC where differences of tenths of a millimeter can hinder access. We thus worked to develop a new Sonopet® specifically designed for powered TEES in cooperation with Stryker Corporation. This dedicated Sonopet® for powered TEES consists of the universal straight-handpiece 25MS and a new H101 tip that is a little shorter than H201 tip and covered with a thinly tapered tip cover. Thus while powered TEES can be safely performed with the H201 tip, this new, specially designed H101 tip is optimized for powered TEES and cuts down on inadvertent contact with the endoscope. It should be noted that while the straight-handpiece is available internationally, at the time of publication, the H101 tip was only sold in Japan (Stryker Japan K.K., Tokyo, Japan). Thus when we refer to a Sonopet® herein, we are referring to an ultrasonic aspirator setup for emulsification of hard tissue. In other contexts in the literature, a Sonopet® could also refer to an ultrasonic aspirator setup for cavitation of soft tissue.

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3.2.5.2 Visao® High-Speed Otologic Drill with a Curved Burr The Visao® High-Speed Otologic Drill is equipped with a curved burr, the tip of which is 2  mm in diameter. It should be noted that the “curved” in the name “curved burr” refers to the non-rotating shaft. The non-rotation of the shaft which is covered by a thin outer sheath is particularly suited to powered TEES because it prevents possible damage to surrounding soft tissue (Fig. 3.5) and like the other non-powered instruments, its curve is essential to performing TEES. The Visao® drill is used in two different ways in the course of performing an atticotomy or atticoantrotomy. The first is to thin the bony plate as described in Chap. 2 which is left over the ossicular chain and the facial nerve. This bony plate is created to protect the ossicular chain and the facial nerve, and the plate is thinned to make it easy to remove later with a hammer and chisel. The second use is to polish away any jagged edges of the atticotomy or atticoantrotomy to facilitate better visualization of the cholesteatoma.

Fig. 3.11 Surgical setup for powered TEES

3.3

Surgical Theater Setup

Figure 3.11 shows our preferred setup of the surgical theater for powered TEES. While the figure is largely self-explanatory and may differ slightly from explanations in other sources [1, 4, 18–20], several points should be stressed. The first is that an armrest is absolutely critical in stabilizing the endoscope-holding hand and preventing arm fatigue and hand tremor. This armrest helps to ensure that the endoscope is smoothly inserted into and removed from the ear canal without any abrupt movements which could result in damage within the ear. We have fashioned our own armrest as shown in Fig.  3.12 which consists of a small table that can be adjusted to the appropriate height and a thick piece of padding. A second point which should be noted is that a microscope should always be positioned close by and available for immediate use. A golden rule for TEES is that if the surgeon feels any doubt about continuing a TEES procedure, they should immediately

Surgical Setup 26 in. monitor

Anesthesia equipment

Anesthesiologist

Endoscope console

es t mr Ar

Assistant surgeon

Surgical tool tray

Sonopet console

NIM

Microscope

Primary surgeon

Nurse

3  Setup and Safety of Powered TEES

27

Fig. 3.12  Armrest used to stabilize arm during TEES

switch over to MES. The ultimate objective is a safe and successful procedure which can be performed by either TEES or MES.

3.4

Patient Preparation

3.4.1 Preoperative Preparation Careful patient preparation also will help to ensure a successful and safe TEES procedure. In addition to the standard preparation for any patient undergoing ear surgery, we perform preoperative prepping of the EAC which can be broken into external and internal steps. Figure 3.13 shows how the external access path to the EAC can be straightened by making a tragal stitch in the anterior direction and creating auricular traction by taping the opposite side in the posterior and superior directions. The EAC itself is prepped by inserting the endoscope and trimming the hair with scissors along the length of the EAC as well as cleaning out all ear wax and dirt. This prepping of the EAC is an extremely important step because it helps to minimize the smearing of the endoscope lens which requires cleaning during surgery. This

Fig. 3.13  Straightening external access path to the EAC by making a tragal stitch in the anterior direction and creating auricular traction by taping the opposite side in the posterior and outward directions

preoperative prepping is also a good first step for novice TEES surgeons to get used to working within the EAC with the endoscope.

3.4.2 Pediatric Patient Considerations Powered TEES, as stated above, can be safely performed in pediatric patients and our presurgical prep is essentially the same.

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3.5

Safety Issues

Any surgery which is performed within the middle ear needs to be done with an especially heightened concern for safety. While many safety-related issues such as thermal damage to facial nerve or inner ear by light source and inner ear damage during bone removal procedure using powered instruments, properly and at optimal settings. The initial safety concerns surrounding non-powered TEES were focused on heat generated within the middle ear by the light source attached to the endoscope. It should be noted here that non-powered TEES has been performed successfully and safely for close to 20  years by others and ourselves [18–20]. However, the introduction of powered instruments within the middle ear raised additional issues of safety which had to be directly addressed including proper handling of the Sonopet® together with skull vibrations generated by the use of powered instruments within the EAC.

3.5.1 Proper Handling of the Sonopet® Proper handling of the Sonopet® is important not only for the safety of the patient, but also for the safety of the endoscope itself. The main concern for the patient is to be careful to ensure that the Sonopet® is not brought too close to surrounding tissue and damage such tissue by the suction function. The main concern for the endoscope is to be careful that the endoscope itself and the Sonopet® do not come into contact with each other. Inadvertent contact with the endoscope can damage the lens beyond repair which results in a very costly surgical procedure! The best way to ensure that the endoscope is not damaged is to make sure that you can always see the black tip cover of the Sonopet® when working with the Sonopet® and the endoscope together. Put another way, do not insert the endoscope past the reach of the Sonopet®.

3.5.2 H  eat Generation by Light Sources The main concern related to heat generated by a light source within the middle ear is the potential for thermal tissue damage. While it should be noted that the use of an endoscope in powered TEES is cooled to some degree by the irrigation of the Sonopet®, the issue of heat generated by the light source still cannot be ignored. A light source which naturally generates heat is attached to the endoscope and that heat has to be dissipated and can be transferred to the endoscope itself. While TEES has, as has been repeatedly stated, been safely performed over many years, our group and others [2, 21, 22] have worked to determine guidelines for proper use of the endoscope to prevent thermal tissue damage, the optimal type of light source and the optimal setting for such light sources. The first and most important maxim related to prevention of thermal tissue damage during both non-powered TEES and powered TEES is to make sure that the endoscope does not come into contact with tissue within the EAC. In addition, the endoscope should be removed at regular intervals to allow for the heat to dissipate with Mitchell and Coulson recommending that the endoscope be removed at least every 5 min for at least 88  s [23]. MacKeith et  al. looked at heat transfer to three parts of the endoscope itself: the tip, the shaft, and the light beam (defined as 5 mm distal to the tip) [21]. They found that with what they described as a “standard Stolz light source,” the tip of the endoscope retained the most heat regardless of tip size and angle. Their findings underscore the importance of not allowing the endoscope tip to come into direct contact with tissue. The study conducted by our own department looked at the type of light source and its settings [2]. We used a 3D-printed model of the temporal bone and measured increases in temperature at three locations within the middle ear cavity: the promontory, facial nerve, and lateral semicircular canal when using either xenon or LED light sources at different settings with 2.7-mm and 4.0-mm

3  Setup and Safety of Powered TEES 60 50 40

4.0 mm, 0-deg Ch 1

Ch 2

Ch 3

29 60 50 40

30

30

20

20

10

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0 60 50

LED 40% LED 100%

XEN 30% XEN 100%

2.7 mm, 0-deg

0 60 50

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30

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LED 40% LED 100%

XEN 30% XEN 100%

4.0 mm, 30-deg

0

LED 40% LED 100%

XEN 30% XEN 100%

2.7 mm, 30-deg

LED 40% LED 100%

XEN 30% XEN 100%

Fig. 3.14  Maximum temperatures for each of the three thermocouples within the middle ear. The maximum temperature measured within the middle ear cavity was less than 31 °C using the xenon light source set at 30% output

and the LED light source at both settings, while the temperature at the promontory and facial nerve exceeded 40  °C using a 4.0-mm endoscope with a xenon light source set at 100%

endoscopes of 0° and 30°. Figure 3.14 shows the results which we obtained, and our findings revealed that xenon and LED light sources could be used safely, so long as the standard settings were not exceeded. These standard settings are generally defined as up to 30% for the xenon light source and 40% for an LED when used with a 4.0mm endoscope. However, we ourselves regularly use and recommend a 2.7-mm endoscope coupled to an LED light source set at a 40% output.

fell within a safe range for the inner ear. We conducted a study in which skull bone vibrations generated by conventional drills were compared to the Sonopet® [25]. The study compared the vibrations generated during a conventional microscopic transcortical mastoidectomy by the Sonopet® in comparison to two conventional drills: an Osteon Drill (Zimmer, Warsaw, Indiana, USA) which we designated as Drill A and Visao® High-Speed Otologic Drill which we designated as Drill B and is the same drill which we used with the curved burr attachment. The skull bone vibrations were measured with a polyvinylidene difluoride (PVDF) film taped to the forehead during mastoidectomy using the Sonopet® and the two types of highspeed drills. PVDF is a piezoelectric material and the charge builds up in the PVDF film in response to applied mechanical stress. Figure 3.15 shows the mean values of the measured skull vibrations and the background noise level at the four frequency bands. In the frequency bands of 500–2000  Hz and 2000– 8000 Hz, the mean values of the Sonopet® with LT-vibration did not exceed the values for Drill B

3.5.3 Skull Vibrations Associated with Powered TEES Otologic drills have long been safely used within the ear and are not associated with damage to hearing function within the standard clinical usage [24]. However, the use of the Sonopet® within the middle ear naturally raised questions about how it compares to conventional drills. A major concern related to the Sonopet® was whether the skull bone vibrations generated by it compared favorably with conventional drills and

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differences in the skull vibrations were observed among the three instruments below 500  Hz or above 8000 Hz.

–80

Mean value [dB rms]

–90 –100

*

–110 –120

*

–130 –140 –150

200–500 500–2000 2000–8000 8000–20k Frequency [Hz] Sonopet-LT Drill B 40 kRPM noise

Drill A Drill B 80 kRPM

Fig. 3.15  The mean values of skull vibrations for Drill A, Drill B, Sonopet® LT mode, and background noise levels shown in four frequency bands –50

Peak value [dB rms]

–60 –70 –80

*

–90 –100 –110

* *

–120 –130

200–500 500–2000 2000–8000 8000–20k Frequency [Hz] Sonopet-LT Drill B 40 kRPM noise

Drill A Drill B 80 kRPM

Fig. 3.16  The peak values of skull vibrations for Drill A, Drill B, Sonopet® LT mode, and background noise levels shown in four frequency bands

with a revolution speed of 40k rpm. The peak values of skull vibrations by the Sonopet® with LT-vibration were significantly lower than the vibrations of Drill B at 40k  rpm in the band of 500–2000 Hz and those of Drill B at 80k rpm in the bands of 500–2000  Hz and 2000–8000  Hz (p