Minimally Invasive Spine Surgery: A Primer [Illustrated] 1626232180, 9781626232181

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Minimally Invasive Spine Surgery A Primer

Luis Manuel Tumialán, MD Associate Professor of Neurosurgery Barrow Neurological Institute St. Joseph’s Hospital and Medical Center Phoenix, Arizona, USA Director of Minimally Invasive Spine Surgery Greenbaum Surgical Specialty Hospital HonorHealth Neuroscience Research Institute Scottsdale, Arizona, USA Illustrated by Joshua Lai, MScBMC Medical Illustrator Neuroscience Publications Barrow Neurological Institute St. Joseph's Hospital and Medical Center Phoenix, Arizona

530 illustrations

Thieme New York • Stuttgart • Delhi • Rio de Janeiro

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Library of Congress Cataloging-in-Publication Data Names: Tumialán, Luis Manuel, author. | Lai, Joshua, illustrator. Title: Minimally invasive spine surgery : a primer / Luis Manuel Tumialán; illustrator, Joshua Lai. Description: New York : Thieme [2020] | Includes bibliographical references and index. | Summary: "The purpose of this work is to be a readable cohesive single-authored introductory text that discusses the principles of minimally invasive spine surgery and then explains the technique procedure by procedure. It is the goal for the reader to experience each chapter as if they are in the operating room with the author. The hope is that the words from the book become the voice inside the resident's head as they see, learn and eventually perform the procedure. This work is written as if the author were actually teaching the resident in a rotation. He begins discussing the philosophical approach to minimally invasive spinal surgery as compared to open procedures and the mindset that one should apply. He then walks the reader through the basic procedures, such as microdiscectomies and laminectomies. Principles introduced in early chapters are reinforced in the later chapters; in this manner, the earlier chapters become the building blocks for the later chapters. This is analogous to resident education, where one would teach a resident a minimally invasive microdiscectomy before going into a lumbar fusion. Each chapter has narrated video for review"– Provided by publisher. Identifiers: LCCN 2019053438 | ISBN 9781626232181 hardcover | ISBN 9781626232198 eISBN Subjects: MESH: Spine–surgery | Minimally Invasive Surgical Procedures–methods | Orthopedic Procedures–methods Classification: LCC RD768 | NLM WE 725 | DDC 617.4/71–dc23 LC record available at https://lccn.loc.gov/2019053438

Important note: Medicine is an ever-changing science undergoing continual development. Research and clinical experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowledge at the time of production of the book. Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers’ leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule or every form of application used is entirely at the user’s own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page. Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain.

Copyright © 2020 by Thieme Medical Publishers, Inc. Barrow Neurological Institute holds copyright to all diagnostic images, photographs, intraoperative videos, animations, and art, including the cover art, used in this work and the accompanying digital content, unless otherwise stated. Used with permission from Barrow Neurological Institute, Phoenix, Arizona. Thieme Publishers New York 333 Seventh Avenue, New York, NY 10001 USA +1 800 782 3488, [email protected] Thieme Publishers Stuttgart Rüdigerstrasse 14, 70469 Stuttgart, Germany +49 [0]711 8931 421, [email protected] Thieme Publishers Delhi A-12, Second Floor, Sector-2, Noida-201301 Uttar Pradesh, India +91 120 45 566 00, [email protected] This book, including all parts thereof, is legally protected by copyright. Any use, exploitation, or commercialization outside the narrow limits set by copyright legislation, without the publisher’s consent, is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, mimeographing, preparation of microfilms, and electronic data processing and storage.

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On the cover:

Cover art designed by Luis Manuel Tumialán and Joshua Lai; illustrated by Joshua Lai Cover design: Thieme Publishing Group Typesetting by Thomson Digital, India Printed in the United States of America by King Printing Co., Inc. ISBN 978-1-62623-218-1 Also available as an e-book: eISBN 978-1-62623-219-8

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A posterior view of the lumbosacral spine is shown, with various minimally invasive approaches shown on the right side of the spine: A minimal access port in position for a microdiscectomy at L5-S1, an expandable minimal access port with a view of the completed osteotomy cuts for a transforaminal lumbar interbody fusion at L4-5 (pedicle screws in position at L4 and L5) and at L3-4, an access port is positioned for removal of a far lateral disc extrusion. A dilator up against the L2 lamina with the various trajectories of exposure is shown for the decompression. Kambin’s prism is shown over the right L2-3 disc space. Finally, a dilator navigates the branches of the lumbar plexus for a transpsoas approach into the L2-3 disc space.

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For Jorge August 11, 1975 – October 19, 2001

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Contents Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Video Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 A Minimally Invasive Perspective: The Conversion

...............................................

1

2 Minimally Invasive Microdiscectomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3 Minimally Invasive Lumbar Laminectomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4 Minimally Invasive Transforaminal Lumbar Interbody Fusion

...................................

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5 Minimally Invasive Far Lateral Microdiscectomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6 Minimally Invasive Lateral Transpsoas Interbody Lumbar Fusion

...............................

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7 Minimally Invasive Posterior Cervical Foraminotomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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8 Minimally Invasive Posterior Cervical Laminectomy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9 Anterior Cervical Discectomy with Arthroplasty or Fusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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10 Minimally Invasive Decompressions for Metastatic Spinal Disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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11 Minimally Invasive Resection of Intradural Extramedullary Lesions within the Thoracic Spine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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12 Radiation and Minimally Invasive Spine Surgery

.................................................

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13 Minimizing Ionizing Radiation in Minimally Invasive Spine Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Coda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Index

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Foreword In the 10 years that I have known Luis Manuel Tumialán, he has been at the forefront of developing minimally invasive approaches to spine surgery. This Primer is a testament to his passion for improving patient outcomes and striving to advance the knowledge and understanding of the art and science of minimally invasive spine surgery. The Primer is a comprehensive, well-written volume on minimally invasive spine surgery encompassing the cervical, thoracic and lumbar spine. It is superbly illustrated with detailed 3D illustrations, drawings and diagnostic studies. In it, Dr. Tumialán not only details the surgical techniques and nuances of minimally invasive spine surgery but also eloquently describes the evolution and historical perspectives of the techniques as they evolved into the minimally invasive procedures he uses daily. Within each chapter, he emphasizes the grounds for surgical intervention plus the advantages of using minimally invasive techniques. Each chapter meticulously details and beautifully illustrates the surgical anatomy. Throughout the book, he underscores the unique anatomy of the spine at each level. Fortunately for the reader, Dr. Tumialán applies his extensive experience with minimally invasive spine procedures to guide the reader through each technique as if they were assisting with the surgery. Chapter 1 presents the history of the conversion from open spine surgery to minimally invasive surgery. Chapters 2 through 6 describe minimally invasive discectomy, laminectomy, transforaminal lumbar interbody fusion, lateral microdiscectomy and lateral transpsoas interbody lumbar fusion. Chapters 7 through 9 portray minimally invasive techniques in the cervical spine and describe in beautiful detail posterior cervical foraminotomy, posterior cervical laminectomy and anterior cervical discectomy with arthroplasty or fusion. Chapters 10 and 11 feature minimally invasive procedures for spinal cord decompression in metastatic spine disease along with the removal of intradural extramedullary lesions within the thoracic spine. Finally,

Chapters 12 and 13 focus on the use of fluoroscopy and radiation safety in minimally invasive spine surgery. Dr. Tumialán also scrutinizes the learning curve of becoming familiar with minimally invasive techniques, always with the aim of accomplishing the surgical task with the least disruption of the vertebral bone and musculature. Throughout the book, he emphasizes the historical aspects of each procedure and how he personally learned from the early maverick surgeons and adapted their techniques to the minimally invasive approach. He describes the pitfalls and pearls of converting to the minimally invasive approach at each level of the spine with instructive cases. For example, in Chapter 3, he describes the removal of the ligamentum flavum in patients with lumbar stenosis and reveals the conversion from piecemeal removal to en bloc removal and discusses the advantages of the latter procedure. He not only describes in detail each specific surgical procedure but also emphasizes the potential complications and their treatment. Minimally invasive spine surgery has changed tremendously over the past few decades, from rudimentary approaches to exquisitely refined minimally invasive techniques. This extraordinary volume covering fundamental and sophisticated minimally invasive spine techniques should be on every spine and orthopedic surgeon’s reading list and reference shelf, and even in the operating room. The Primer and its video accompaniments are certainly essential for the surgeon, resident or fellow who desires to learn and develop expertise in minimally invasive spine surgery. In the spirit of advancing our craft, Volker K.H. Sonntag, MD Emeritus Professor, Vice Chairman, and Spine Section Chief Department of Neurosurgery Barrow Neurological Institute St. Joseph’s Hospital and Medical Center Phoenix, Arizona December 2019

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Preface We all come from the past, and children ought to know what it was that went into their making to know that life is a braided cord of humanity stretching up from time long gone, and that it cannot be defined by the span of a single journey from diaper to shroud. Russell Baker The practice of spine surgery is remarkable in that every spine surgeon I have ever met has been so willing to share their knowledge, teach me their tricks and talk to me about their failures as much as their successes. The entire basis of all of our professional meetings is sharing our recent experiences in the management of the spine and discussing new developments for its surgical treatment. The objective is as simple as it is noble: teach other surgeons how to help patients. Such an open-source environment can only lead to the rapid development of technology and seismic advances in a field. A fast-paced advancement has indeed been the case for modern spine surgery, which is less than 100 years old. Although it may be hard to fathom, it was only a modest 85 years ago that Mixter and Barr first reported the surgical management of radiculopathy by removing an extruded lumbar herniated disc that was compressing a nerve root. I have patients older than Mixter and Barr’s operation. It has been 61 years since Cloward, Smith and Robinson described anterior cervical approaches that revolutionized the management of cervical radiculopathy and myelopathy. Most of my patients are older than that operation. Roy-Camille began routinely using lumbar pedicle screws in 1986, which makes me older than that technique. The common denominator among all these developments is that these pioneering surgeons identified a structural problem amenable to a surgical solution. Whether a compressed nerve root in the cervical or lumbar spine or a dynamic instability, surgeons conceived and then executed a surgical intervention, analyzed their results and published their findings. Successes or failures, they hid nothing. Instead, they shared their experiences with the world. They taught generation after generation of surgeons how to perform these procedures. In turn, each generation of surgeons made their contribution to refining each procedure, or in some circumstances, they developed something entirely new. The development of minimally invasive spine surgery is part of that continuum. Throughout the decades of development and iterations, surgeons established patterns and traditions that were inevitably passed on as well. In much the same way, my

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son may sputter out an adage spoken by my father’s grandmother, which he has heard a thousand times come from my mouth. Similarly, we must indeed utter statements in the operating theater, the origins of which we do not necessarily know short of our mentors. But our mentors may have repeated it from their mentors, who may have, in turn, repeated the same statement from another generation. Some of those classic quotations have undoubtedly bubbled to the surface in this work. Vox audita perit, litera scripta manet. This Primer is a continuation of the open-source mentality that is the specialty of spine surgery. In its simplest form, it is nothing more than a historical account of where we have been, a snapshot in time of where we currently are and a modest hint of where we have the potential to go. The material in this book came from “a braided cord of humanity stretching up from time long gone,” which has been so well captured in our peer-reviewed literature. For each procedure, I have gathered those writings of pioneering surgeons, reviewed the more recent rigorous analyses of our peerreviewed literature and placed them alongside the wise words of mentors and the tricks I have been taught along the way. I have attempted to lay the material out in a manner that would be beneficial to the medical student, resident, fellow or practicing spine surgeon. The goal is to understand the origins of the procedure, the anatomical basis and the nuances of the surgical technique. The hope is that the contents of this book will help surgeons help their patients, the same way the mentors, friends and the timeless voices in our spine literature have helped me help my patients. And so, to paraphrase the late Russell Baker quote that begins this preface, I leave the reader with the following thought before embarking on this Primer of minimally invasive spine surgery: We all come from the past, and spine surgeons ought to know what it was that went into the ability to routinely perform both the simple and complex spine operations of today. To know that our specialty is a braided cord of experiences, both successes and failures, stretching from time long gone, and that it cannot be defined by the span of a single journey from residency to retirement. Luis Manuel Tumialán Phoenix, Arizona December 2019

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Acknowledgments I did not know precisely what form this book would eventually take when I blissfully and quite naïvely embarked upon writing it 4 years ago. One thing is certain: At the time, I had no concept of how to bring to life the images in my mind; how to organize an entire library of intraoperative photographs, MRIs and operative footage; or even how to appropriately assemble all the chapters. All I knew is that there was the concept of a book percolating in my mind, and I just started typing. The reality is that assembling a book such as this Primer is a veritable construction project, where an entire team of professionals is needed. I was fortunate to have such a team of experts in the Barrow Neuroscience Publications Department. Without that team, the Primer would not resemble the final, fully matured form you have before you. In fact, it would never have seen the light of day. Instead, it would be a half-baked idea still percolating in my mind. The construction foreman of this project was Mark Schornak, who leads the Neuroscience Publications team. Mark proficiently coordinated the efforts of the animators, illustrators and video editors while Mary Ann Clifft led the early editorial process. They created method for the chaos I would bring week after week when I visited the department. Throughout the submissions of the chapters, Lynda Orescanin untethered my tangled prose and put appropriate limits on my use of metaphors. She tempered my desire to anthropomorphize surgical instruments but, at the same time, encouraged my voice to surface in the writing, which allowed me to jettison the neutral academic voice from the pages of this book. Somehow, Lynda struck a perfect balance. Time and again, Lynda’s keen eye would identify opportunities to clarify a point or restructure a sentence. Thus, the neologism, to “Orescan” a chapter came into being to describe Lynda’s work. As a result of the proficient “Orescanning,” the Primer is a vastly improved product. It became evident very early in this project that to communicate a concept or idea central to minimally invasive spine surgery, the artwork had to depict what a surgeon sees through an operating microscope. Artists created wonderful hand-drawn art early in this project, but those works could not capture the spatial lighting and stereovision the eyes see with the operating microscope, especially through a minimal access port. Nor do two-dimensional photographs from a microscope capture the essence of depth. An important decision was made very early in this project to invest the time needed to build a computer model that

would allow for the necessary perspectives that would better communicate the images seen in minimally invasive spine surgery. Over several months, Joshua Lai brought our spine model, affectionately known as Gilgamesh, to life, and with it, a new perspective on artwork for minimally invasive spine surgery. While the creation of Gilgamesh threw off all the timelines for the completion of the book, I believe that it was a worthwhile endeavor. I am grateful for the support offered by Mark Schornak throughout that creative process and the backing by Barrow Neurological Institute to see it through. I trust the reader will find genuine benefit in the various computer-generated figures created for this work. I am grateful to Michael Hickman, who brought to life those concepts that require animation to communicate the point superbly. Phillip Hoppes expertly breathed life into radiation physics with his illustrations and animations in Chapters 12 and 13. Phil’s work positively impacts the reader’s ability to comprehend and absorb what is otherwise an esoteric topic and help them decrease their radiation exposure throughout their careers in spinal surgery. Cassandra Todd somehow organized a library of over a thousand images, sought the necessary copyright permissions for previously published images and edited countless figures, adding measurements, arrows or highlights that offered clarity. Marie Clarkson weaved my narrations to correspond with the operative video footage, Josh’s spectacular artwork and the animations created by Mike and Phil to produce a seamless video for each chapter that summarizes the key points. Danielle VanBrabant and Peter Lawrence also lent their talents to the project, enhancing, modifying or creating images to fill the voids recognized at the eleventh hour. Finally, no chapter was considered complete until processed by the scrutinizing eye of Samantha Soto. Samantha identified the glaring omissions committed by the author and systematically formatted each chapter, bringing further order and organization to each chapter and the Primer as a whole. Samantha’s work is best captured with the neologism “Sotorization,” which means the complete and exhaustive analysis and correction of the form, content and structure of a chapter. Samantha left no “t” uncrossed and no “i” undotted. Without this remarkable team of professionals coordinated by a thoughtful construction foreman, there would be no Primer. I am indebted to my Minimally Invasive Ensemble at Greenbaum Surgical Specialty Hospital, where I perform

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Acknowledgments

the majority of the surgeries I present in this book. The unparalleled level of professionalism exhibited by that team allows me to deliver the highest level of care to my patients. Finally, I wish to thank the patients who have entrusted me with their care. Without that trust, I never would have gained the knowledge and experience to have produced this work. The gratitude that I have for my patients’ faith in me is

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the basis for my unfailing dedication to continuing to advance the field of spine surgery. In the end, this Primer is a meager token of appreciation for that trust and faith. Luis Manuel Tumialán Phoenix, Arizona December 2019

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Video Contents Chapter 1: Minimally Invasive Conversion Chapter 2: Minimally Invasive Microdiscectomy Chapter 3: Minimally Invasive Lumbar Laminectomy Chapter 4: Minimally Invasive Transforaminal Lumbar Interbody Fusion 4.1: Overview 4.2: Phase I 4.3: Phase II 4.4: Phase III Chapter 5: Minimally Invasive Far Lateral Microdiscectomy 5.1: Management of Far Lateral Disc Herniations L1-2 to L4-5 5.2: Management of Far Lateral Disc Herniation L5-S1 Chapter 6: Lateral Transpsoas Interbody Lumbar Fusion Chapter 7: Minimally Invasive Posterior Cervical Foraminotomy Chapter 8: Minimally Invasive Posterior Cervical Laminectomy Chapter 9: Anterior Cervical Discectomy Chapter 10: Minimally Invasive Resection of Metastatic Disease 10.1: Introduction and Case 1: Metastatic Non Small Cell Lung Cancer to T9 10.2: Case 2: Metastatic Small Cell Lung Cancer to T3 10.3: Case 3 and Conclusion: Management of Metastatic Testicular Carcinoma to T10 Chapter 11: Minimally Invasive Resection of Intradural Extramedullary Lesions 11.1: Introduction and Management of Intradural Meningiomas 11.2: Management of Spinal Dural Arteriovenous Fistula and Conclusion Chapter 12: Fundamentals of Fluoroscopy Chapter 13: Minimizing Ionizing Radiation in Minimally Invasive Spine Surgery

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Introduction I distinctly remember the first time I gazed down into a minimal access port. I felt lost. Completely lost. Nothing more than a tuft of muscle lay within my field of view, without so much as a hint of bone to offer me a glimmer of hope. The preliminary exposure looked nothing like what I had seen in the figures from the article I had read the night before. I remember my anxiety as I studied every millimeter offered to me by that 14-mm-diameter minimally invasive access port. I wondered where and how to even begin. As I zoomed out from the microscope, I wondered how it would be possible to perform an operation through such a constrained device. As I zoomed back in, I reaffirmed that my objective was to decompress a cervical nerve root. That event would not happen if I just stared at the hole. I had to actually do something. The only problem was that I could not conceive how to possibly accomplish the task at hand while looking at an unknown landscape at the bottom of this port. With great trepidation, I took the cautery and lightly touched a tuft of muscle. With that simple step, my career in minimally invasive spinal surgery began. As I continued to work, I was uncertain about the midline and concerned about the exposure. I did not want to venture into the canal, but at the same time, I did not want to interrupt the facet. I desperately needed to visualize the lamina, the facet, or any bony prominence to gain some element of orientation. Even as I began the exposure, I still had no idea where I was relative to the midline. With foreboding unease, I began to unveil the bony anatomy that hid underneath. I slowly began to recognize parts of the posterior cervical spine. With a countless number of anteroposterior, lateral and even owl’s eye fluoroscopic images, along with hints of the partially exposed bony anatomy, I was able to assemble the structures at depth. As my confidence grew, my anxiety receded. Finally, I exposed the requisite anatomy and began to drill slowly, very slowly. The terrain was still unfamiliar, but at least the elements of the anatomy were now somewhat recognizable. No one was more surprised than I that I was ultimately able to accomplish the objectives of the operation. My first minimally invasive operation was far from efficient. In fact, it took hours. But I was genuinely surprised when I saw how well the patient did afterward, despite my struggle. Although the case I have shared with you represented the beginning of my career in minimally invasive spine surgery, I do not want it to represent the beginning of yours. For that reason, I have written this book. Upon completion of my residency years ago, I developed a strong interest in applying minimally invasive techniques to the various spine surgeries I was performing. But what I sought did not exist: a practical introductory text that would convey the essentials of minimally invasive spine

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surgery. I did find several comprehensive multi-authored texts but no introductory text that could serve as a primer. There was no book that I could read from beginning to end. Nor was there a book from which I could select one chapter as a practical guide for a procedure such as a posterior cervical foraminotomy. Several wonderful surgical technique articles exist in our vast spine literature, but they are constrained by scientific writing that inhibits the friendly voice inside the reader’s head from talking one through the operation. Equally important were the practical aspects of the operation, such as room set up, recommended instruments and tricks of the trade, all of which are difficult to convey in a peer-reviewed technique paper. As I surveyed the landscape of textbooks, I felt a need to fill the void of reading material that exists for residents and fellows who are interested in minimally invasive spine surgery. The current text represents my effort to do just that. But as I set about writing this Primer with the intent of filling that void, I realized that I needed to understand more about how the mind transitions from open spine surgery to minimally invasive spine surgery. As I reflect on my own learning experience and watch the early experience of the residents and fellows with whom I am privileged to work, I ask myself: Why is it that minimally invasive surgery presents so many hurdles? After all, the anatomy of the spine does not change simply because of the selection of a minimal access port over a Williams retractor. Moreover, a minimally invasive exposure, while limited, should be no different than an open exposure. In fact, the exposure of the requisite anatomy should be exactly the same. The logical question now becomes: What is the essential difference between minimally invasive spine surgery and traditional midline open spine surgery? Perhaps embedded in the answer to that question is a path forward to learning how to perform minimally invasive surgery on the spine. The pages before you represent my attempt to answer that question. But first, I must begin by comparing minimally invasive spine surgery to traditional midline spine surgery.

The Premise of Minimally Invasive Spine Surgery I have long marveled at how little of an open exposure I actually use to accomplish an operation on the spine. In years past, I often looked down into a wound with retractors open at the end of a single-level fusion or simple lumbar decompression, astounded by the degree of retraction of muscle and skin. Whether performing a microdiscectomy or a lumbar fusion, I have observed that the exposure was more a consequence of the midline approach than of an

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Introduction

actual need to expose the requisite anatomy to accomplish the operation at hand. The issue was obvious. Most of the anatomy I was exposing was the consequence of starting in the midline but needing to expose lateral enough to reach the pedicle screw entry points and transverse processes for an instrumented fusion or reaching the lateral aspect of the lamina for a decompression. As I ventured into minimally invasive spine procedures, I noticed the exact opposite: I used almost every millimeter of exposure granted to me by an access port. I had to. Little if any anatomy that I exposed was unnecessary for the operation, so I had better be in the right place. From these observations, I generated what I believe to be the three premises of minimally invasive spine surgery. The first premise is that surgeons use only a small percentage of a traditional midline open exposure to perform the actual operation. The rest of that exposure is the inevitable consequence of the midline approach. The second premise is that the same operation may be performed with a precisely focused but limited exposure, where the surgeon uses almost the entire exposure to perform the operation. One may consider the second premise to represent the efficiency of an exposure, a concept that warrants further explanation. If one were to consider the efficiency of an exposure as the ratio of requisite anatomy needed to actually perform the operation relative to actual anatomy exposed, then minimally invasive exposures are highly efficient. Caspar first introduced the concept of a ratio between the surgical target and the surgical exposure as he reflected on the management of patients with lumbar radiculopathy. Caspar believed that the outcomes of those patients were compromised by disproportionately large exposures relative to the surgical target. In his 1977 publication on microdiscectomy, Caspar1 advocated precise monosegmental unilateral access to the lumbar segment with minimal disruption of the paraspinal musculature. Most importantly, he emphasized the significance of minimizing the surgical exposure relative to the surgical target. To acknowledge Caspar’s contributions to advancing this central principle of minimally invasive surgery, I will refer to the efficiency of a surgical exposure as the Caspar ratio throughout this Primer (i.e., the ratio of surgical target to surgical exposure). Surgical Target ðmm2 Þ Efficiency of a ¼ ¼ Caspar Ratio Surgical Exposure ðmm2 Þ Surgical Exposure

Striving for a Caspar ratio of 1 is a central theme of the Primer. After all, striving for equivalence between the surgical exposure and target is the foundation of minimally invasive surgery of the spine (▶Fig. 1). The third and final premise is that minimally invasive operations must be indistinguishable from their open

counterparts. This last premise traces its origins to Dr. Richard Fessler’s thoughtful foreword to the Neurosurgery supplement on minimally invasive spine surgery that was published in 2002, which is a must-read for anyone beginning to learn minimally invasive spine surgery.2 These premises will serve as our guideposts throughout the various chapters in this Primer. They are the standards by which we will measure each minimally invasive procedure and technique.

The Organization of the Primer The Primer is divided into four sections. The first three sections are the various minimally invasive procedures for the lumbar, cervical and thoracic spine. I have found that most minimally invasive texts begin with the cervical spine, which is the logical approach from an anatomical standpoint. However, I chose to begin with the lumbar spine in this Primer because it is the most practical place to commence the minimally invasive conversion. I would recommend against starting your minimally invasive career (as I did) with a posterior cervical foraminotomy. Within the lumbar spine section, I predictably begin with the lumbar microdiscectomy. If there is a minimally invasive procedure to cut your teeth on, it is the microdiscectomy. For several reasons, it is the perfect gateway procedure for minimally invasive approaches. The exposure of the surgical anatomy is similar to that with an open approach and thus is familiar to the surgeon. The reconstruction of the anatomy at depth that has to occur in the surgeon’s mind is limited because it is so close to the midline. The surgeon can therefore connect the lines of what is seen to what is unseen in a relatively straightforward manner. In the microdiscectomy, those lines are short because the relevant surgical anatomy is just off the midline. Perhaps the most important aspect of the minimally invasive microdiscectomy is that it offers the opportunity to become familiar with the various bayoneted instruments and to work with them within the constraints of a minimal access port. It is also an opportunity to become comfortable working with a minimally invasive drill attachment. As your familiarity with bayonetted instruments develops and your comfort level with precisely docking the minimal access port increases, you will be able to expand your minimally invasive armamentarium. Converging the minimal access port toward the midline instead of just over the nerve root paves the way for decompression of the entire thecal sac. The minimally invasive laminectomy is the next logical step. The increased angulation will affect your capacity to remain oriented, but building on the subtle angulation that your mind has become accustomed to with the microdiscectomy will make bridging that gap less of a leap and more of an inevitable step. The acquired skill set resulting from the combination of these two procedures

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Fig. 1 Juxtaposition of two exposures for a lumbar microdiscectomy. (a) By its very nature, the traditional midline approach (purple outline) requires more exposure than the minimally invasive approach (blue outline), but the requisite anatomy required for the operation remains the same. (b) Magnified view of a traditional midline open left L4-5 microdiscectomy with use of a McCulloch retractor. To fully visualize the requisite anatomy in a midline approach, the surgeon will need to make a longer incision and expose more of the

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anatomy. (c) In this intraoperative photograph, the L4-5 segment has been exposed for a minimally invasive microdiscectomy. The nerve root suction retractor is in position, retracting the traversing nerve root of L5. The disk space can be seen lateral to the nerve root. Precise placement of a minimal access port over the requisite anatomy accomplishes the same goal through a 16-mm diameter aperture. When the efficiency of the exposure is the ratio of requisite anatomy to exposed anatomy, the minimally invasive exposure is highly efficient.

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will form the basis for beginning minimally invasive transforaminal lumbar interbody fusions, the fourth chapter of this Primer. By the same token, the expertise gained by working through the transforaminal corridor for interbody fusion translates immediately to the far lateral microdiscectomy, which I cover in Chapter 5. The far lateral microdiscectomy places the surgeon the farthest from the midline and therefore has the potential to be the most disorienting. Early in my experience, I found this procedure to be quite challenging. It is obvious to me now why that was the case. In the farlateral approach, the lines that are seen are the farthest from those that are unseen. My mind had the greatest amount of anatomy to reconstruct at depth with this procedure, more so than for any other. Distance from the midline underscores a constant theme that will develop in your conversion: Midline is the basis of your orientation. Therefore, the farther you migrate off the midline, the greater the likelihood you will become disoriented. The lumbar section ends with a chapter on the transpsoas approach to the lumbar spine. The lateral approach to lumbar disc spaces has caused a seismic shift in spine surgery since its introduction, especially in the management of adjacent segment degeneration, coronal imbalance and scoliosis. I cover minimally invasive approaches to the cervical spine in the second section. The cervical section proceeds in a similar manner to the lumbar section. It begins with the posterior cervical foraminotomy then moves to the cervical laminectomy before ending with the anterior cervical discectomy. The inclusion of a chapter on the anterior cervical discectomy may mystify residents and fellows. That particular chapter may at first seem extraneous and out of place in this Primer, but I hope that after reviewing it, the reader will understand my logic for including it and find it especially relevant to the overall text. The third section delves into the minimally invasive management of more complex clinical scenarios, such as nerve sheath tumors in the lumbar and thoracic spine and the management of metastatic disease. This section ends with a chapter on the minimally invasive management of a constellation of intradural extramedullary lesions, both vascular and neoplastic. The fourth and final section contains two chapters on a topic important not only to patients but also to spine surgeons and their operating room staff. The material in that chapter could have been combined with that of another section or even this introduction, but I chose to place it into its own section to underscore its significance. The topic is radiation exposure in minimally invasive spinal procedures. I believe that the current generation of residents and fellows —our next generation of surgeons—is being exposed to more ionizing radiation than the generation before us. We will probably have no concrete idea of what the impact of

that increased radiation exposure will be until the end of our careers. By that time, it will be too late to do anything about it. Thus, this concluding section on radiation awareness is intended not only to heighten our awareness of radiation exposure but also to discuss ways to decrease that exposure. Understanding the fundamentals of fluoroscopy, which I review in Chapter 12, is an essential component of decreasing radiation exposure. That understanding will form the basis for my discussion of a low-dose radiation protocol in Chapter 13. It is my hope that minimally invasive spine surgeons will use this understanding and some form of this protocol to decrease their radiation exposure over their lifetimes. My concern about radiation exposure should also serve as an explanation for the noticeable absence of a chapter covering percutaneous techniques. In the absence of navigation, the radiation exposure for placement of a percutaneous screw is simply too dear in my estimation. Admittedly, computer-assisted navigation immediately neutralizes this argument, but as the reader will see in the minimally invasive transforaminal lumbar fusion chapter, there are other reasons I have shifted away from percutaneous techniques. The absence of material on percutaneous techniques should in no way be misconstrued as a criticism of that technology, which several of my colleagues use every day to improve the lives of their patients. More than anything, it represents the path I happened upon as I went through my own learning curve, exploring the various minimally invasive options for instrumentation. The organization of each chapter in this Primer is consistent throughout the text, beginning with an overview, evolution and history of the procedure before discussing the anatomical basis for a minimally invasive approach for that particular procedure. I then discuss the technique from operating room setup to the phases of the operation and operative nuances. Each chapter ends with a review of clinical cases in which the minimally invasive procedure was applied. Finally, a word on the references included at the end of each chapter. I have approached referencing the spine surgery literature in the Primer differently than I have any of my previous works. For a reference to find its way into this Primer, it must have met the following criteria: I must possess the actual manuscript (not just the abstract), and I must have read the entire manuscript—often more than once. If these criteria are not met, then I will assure my reader the reference will not adorn the bibliography. My hope is that this stringent approach will offer readers a meaningful bibliography that will prove worthwhile reading. In doing so, I hope to make up for the various book chapters and articles I have written in the past that contained a seemingly endless bibliography, empowered by bibliography software that makes references so readily available.

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A Minimally Invasive Spine Surgery Philosophy and Disclaimer I readily concede that the contents of this book represent one surgeon’s approach to minimally invasive surgery on the spine. It is certainly not the be-all or end-all. No two procedures are ever conducted exactly the same way by any two surgeons, even those who trained in the same program under the same mentor. We all evolve our own techniques with each procedure based on our own experiences and training. My hope is simply to offer a starting point for spine surgeons interested in minimally invasive techniques. Such a framework can aid residents in preparing for a case the following day, seasoned fellows examining the anatomical basis for a minimally invasive approach and attending surgeons who are beginning to apply minimally invasive techniques in their practices. Each surgeon reading this Primer will undoubtedly develop his or her own technique, incorporating or dismissing the various elements of each chapter. Not only do I expect this reaction, but I encourage it. I have little doubt that, at some point, a reader of this work will develop a superior technique for one of the procedures mentioned in it. Perhaps a reader will even develop a new technique that was not mentioned at all or not even conceived at the time of this writing. In the years to come, I want my readers to eclipse the contents of this current work and to advance our specialty for the betterment of our patients. More than anything, the contents of this book reflect my journey through my own learning curve. I wish to share some of that experience in the form of a stepwise approach to the common minimally invasive procedures that are routinely performed and then to proceed with more advanced techniques to address more complex clinical scenarios. I hope to eliminate the snares that entrapped me during my journey and to smooth out the terrain so that the reader may have a seamless transition into the minimally invasive precinct. No book can diminish the challenges or eliminate the complexity of learning minimally invasive surgery. But perhaps the contents of the Primer will serve as a lens through which you can view and begin to understand what your mind must unravel to become proficient. All the procedures I discuss follow simple and consistent philosophical principles regarding minimally invasive surgery on the spine. The first and foremost principle builds on the third premise introduced earlier, which bears repeating: There should be no difference between operations performed minimally invasively and those conducted with a traditional midline approach. The incisions may vary in length and location, but the work performed at depth should be indistinguishable. The second principle is the importance of minimizing ionizing radiation. The literature is replete with manuscripts reporting increased radiation exposure in minimally invasive spine surgery. Radiation exposure is a frequent criticism of minimally invasive

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approaches. Some surgeons consider it a barrier to the application of minimally invasive techniques. I would like for readers to develop a mindset that there is no reason why a minimally invasive procedure cannot be done with less radiation than an open procedure. In fact, there is no reason these procedures cannot be done with less radiation than ever before.

A Historical Perspective Before closing this chapter, I would like to invite the reader to consider the rise of minimally invasive surgery as part of a continuum that began at the dawn of our specialty. Initially, I erroneously conceived the rise of minimally invasive spine surgery as a sudden sea change in spine surgery that occurred during the early part of this century. In writing this book, I have discovered that my initial notion could not be further from the historical reality. Less invasive techniques have always been part of the spirit of innovation for surgeons challenged with various degenerative and neoplastic diseases of the spine. Over the years, surgeons undoubtedly saw the adverse consequences of extensive exposures. The disability caused by postoperative pain and, at times, instability in postoperative patients had to have prompted an “I can do more with less” mentality in these surgeons. Modifications to procedures arose to address what surgeons obviously viewed as the unnecessary disruption of the native spine. The desire to do more with less has been part of a continuum ever since the first descriptions of lumbar disc herniations as a cause of radiculopathy. In fact, no procedure over the decades better demonstrates the desire of surgeons to disrupt less and less of the anatomy to accomplish an operation than the surgical management of lumbar disc herniations. For that reason, I end this introductory commentary with the evolution and refinement of that procedure. Originally managed with bilateral laminectomies and transdural resection of the disc material, lumbar discectomies quickly evolved into bilateral laminectomies and extradural resection of disc material as described by Mixter and Barr. In short order, Semmes and Love described hemilaminectomy for discectomy, and soon thereafter, Love described the discectomy, working solely within the intralaminar space with no bone removal at all. That evolution occurred over the span of 11 short years after Dandy’s original description of this clinical entity.3 The ensuing decades brought forth the operating microscope by Yaşargil and Caspar, with further modifications to minimize the extent of exposure made by Williams soon thereafter.4 The most recent step in this evolution was the migration from a subperiosteal dissection of the spinous process and lamina to a paramedian transmuscular approach precisely and directly onto the lamina facet junction with a tablemounted minimal access port as described by Foley and

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Introduction Smith.5 The migration from a subperiosteal dissection to direct access onto the spine ushered in the current modern era of minimally invasive techniques descr