Ebook Minimally invasive spine surgery techniques, evidence, and controversies: Part 1

(BQ) Part 1 book Minimally invasive spine surgery techniques, evidence, and controversies has contents: The definition of minimally invasive spine surgery and the rationale for its use, the four pillars of minimally invasive spine surgery, posterior foraminotomy,.... and other contents.

Roger Härtl | Andreas Korge

Minimally Invasive Spine Surgery

Techniques, Evidence, and Controversies

711 illustrations and images, and 35 cases.

Roger Härtl | Andreas Korge

Minimally Invasive Spine Surgery

Techniques, Evidence, and Controversies

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Foreword

incisions, while other chapters describe very innovative proaches It is pleasing to see that the basic AOSpine surgi-cal principles have been taken into account when formulat-ing the approaches Even with the drive for all approaches

ap-to be minimal, authors include a realistic valuation that, in some cases, MISS techniques could be inappropriate

Radiation exposure is a concern and should be closely itored

mon-The book is a comprehensive coverage of all techniques in minimally invasive spine surgery A word of caution, some approaches are very complex and the surgeon will have to

be highly skilled, requiring three-dimensional thinking; such techniques may be out of reach for lesser mortals Never-theless, the descriptions, pictures, and diagrams are excel-lent and have made the understanding of the approaches very clear

This book is beautifully produced and written to a very high standard, a standard one would expect from such eminent surgeons

I strongly recommend Minimally Invasive Spine Surgery—

Techniques, Evidence, and Controversies to all current and up-and-coming spine surgeons developing their minimally invasive surgical techniques I would go so far as to say this

is “a must have” book for such surgeons In fact, it should

be on the bookshelf of all spine surgeons

The authors are to be congratulated on producing such a

comprehensive book on minimally invasive surgical

tech-niques They stress that access strategies should not

com-promise the goal of the surgical procedure, the importance

of the knowledge of the anatomical planes, and an

appre-ciation of the anatomy from the experience of performing

open procedures They accept there is a long learning curve

and correctly recommend a strategy of performing more

straightforward cases at the beginning of a surgeon´s

intro-duction to minimally invasive surgery A concept that many

inexperienced surgeons find difficult to acknowledge

The importance of the four “pillars” of MISS are emphasized:

microsurgical techniques; access strategies to the spine;

im-aging/navigation techniques; and specialised instruments

and implants Some chapters use standard approaches that,

with recent technology, have been reduced to very small

John K Webb FRCS Consultant Spinal Surgeon Centre for Spinal Surgery and Research University Hospital

Nottingham NG7 2UH United Kingdom Co-founder and first President of AOSpine

Dedication

To Alasha, Sebastian and Julian.

To Heidrun, Louisa and Daniel.

For all their love, support, understanding and patience,

without which, this book would not have been possible

Acknowledgments

We would like to thank the many authors, educators,

il-lustrators, designers, project managers, and technical and

administrative contributors that worked tirelessly to bring

this publication to life

• Jeff Wang, Khai Lam, and Frank Kandziora, the original

members of the expert group team (together with

Rog-er Härtl and Andreas Korge) for bringing togethRog-er the

ideas for the book

• Our illustrious team of authors, from all corners of the

world, many juggling professorial and academic

posi-tions, and or very busy medical and surgical practices

• Kathrin Lüssi and Patricia Codyre and the entire AO

Education team, led by Urs Rüetschi

• Claas Albers from AOTK; and the AOSpine team, led by

Alain Baumann

• Amber Parkinson and Michael Gleeson, Project

Coor-dinators

• Marilyn Schreier from Syntax language editing

• Jecca Reichmuth for scientific illustrations and Roger Kistler for typesetting

• Carl Lau, Cristina Lusti, and Susanne Klein for reading, and for Susanne's essential administrative work (keeping track of our world traveling authors)

proof-• Patrick Hiltpold from AO CID for compiling the based summaries and PICO analyses

evidence-• Rosalie Villano from Leica Microsystems, Thomas Kienzle from Richard Wolf Medical Instruments, and Drew Messler from Micro Image Technologies for supplying photos and images

• Thieme publishingRoger Härtl

Andreas Korge

Thoracic Techniques, and Lumbar Sacral Techniques—both posterior and anterior This comprehensive book not only provides basic concepts, and the latest clinical and scien-tific research, but it is also case-based with clear photographs, x-rays, MRI, CT scans, and illustrations of anatomy and cases, giving the reader an excellent understanding of the decision-making process, as well as the whole surgical pro-cedure from preoperative planning to recovery.

In the end, several conclusions can be drawn:

• MISS is here to stay; it is a logical consequence of the evolution of surgery, based on advances in at least four areas: microsurgery, navigation, new spinal access strat-egies, and spinal instrumentation

• MISS offers alternative and frequently advantageous treatment options in all regions of the spine, and for most pathologies; it expands our technical capabilities as sur-geons and frequently allows the safer and more effective treatment of patients that were previously not considered good surgical candidates for a particular operation

• More work is needed; especially in the area of spinal deformity correction The success of minimally invasive spine surgery will depend on the integration of scien-tific progress, technical expertise, and the surgeon’s individual experience and good judgment

• Surgeons have to be willing to learn and evolve; they have to continue to critically and honestly evaluate the pros and cons of MISS as well as their own results in each patient

We hope that neurological and orthopedic spine surgeons all around the world can benefit from this first edition of

“Minimally Invasive Spine Surgery—Techniques, Evidence, and Controversies” to improve care of their patients

We are thankful to our colleagues, families and AOSpine for the unconditional and enthusiastic support they have given us throughout the preparation of this book

Introduction

Introduction

This is the first edition of “Minimally Invasive Spine

Sur-gery—Techniques, Evidence, and Controversies” The idea

for the book came out of our work in the AOSpine Expert

Group on MISS and Navigation, around 2008, where we

enthusiastically discussed many of the initial hopes and

controversies that surrounded the evolving field of MISS

with our esteemed colleagues Jeff Wang, Khai Lam and

Frank Kandziora It was clear to all of us that MISS offered

exciting and potentially effective treatment strategies for

many areas in spinal surgery However, it also seemed to

be heavily dominated by a small number of champion

sur-geons and steered by industry, and not necessarily by the

needs of our patients As a consequence, we embarked on

an ambitious project to critically explore the possibilities,

the current reality, but also the limitations of MISS

The final product has greatly surpassed our initial

expecta-tions We proudly present a comprehensive, user-friendly

and didactic overview of the techniques, indications and

controversies of currently utilized minimally invasive

tech-niques and spinal navigation in the cervical, thoracic and

lumbar spine for a wide variety of spinal disorders We

include critical discussions of the pros and cons of these

techniques for our patients, and provide an objective,

evi-dence-based framework of MISS using currently published

literature We also acknowledge the importance of the

geon’s individual experience and wisdom by including

sur-gical pearls and “tips and tricks” from master surgeons and

many of the pioneers of MISS

The book has been divided into five sections that together

cover all areas of MISS: In the “Fundamentals” section, we

explore the principles of MISS, its historical development

as a consequence of advances made in various subspecialties

within surgery, and how its principles perfectly fit the “AO

philosophy” The sections following cover technical

proce-dures and the science behind particular MISS approaches

based on the anatomic regions: Cervical Techniques,

Spine Center, Cedars-Sinai Medical Center

444 South San Vicente Boulevard, #800

Los Angeles, CA 90048

USA

Vijay Anand, MD FACS

Clinical Professor of Otolaryngology-Head and Neck

Surgery

Weill Cornell Medical College

New York Presbyterian Hospital

Weill Cornell Medical Center

New York, NY

USA

Ali A Baaj, MD Assistant Professor Director, Spine Surgery Program Division of Neurosurgery University of Arizona

1501 Campbell Ave Tucson, AZ 85724 USA

Gopalakrishnan Balamurali, FRCS Neuro Consultant Spine and Neurosurgeon Department of Orthopaedics, Accident and Spine Surgery

Ganga Hospital Coimbatore, Tamil Nadu India

Eli M Baron, MD Board Certified Neurosurgeon Spine Surgeon

Cedars-Sinai Spine Center

444 South San Vicente Boulevard, Suite 800 Los Angeles, CA 90048

USA

Rahul Basho, MD Clinical Instructor of Spine Surgery Department of Orthopaedic Surgery Riverside County Regional Medical Center

26520 Cactus Avenue Moreno Valley, CA 92555 USA

Rudolf W Beisse, Prof Dr Chief Surgeon

Department of Spine Surgery

St Benedict´s Hospital Bahnhofstrasse 5

82327 Tutzing Germany Oheneba Boachie-Adjei, MD Chief, Scoliosis Service Hospital for Special Surgery

535 East 70th Street New York, NY 10021 Professor of Orthopaedic Surgery Weill Medical College of Cornell University USA

Andreas Korge, MD Head of Department Spine Center Schön Klinik München Harlaching Harlachinger Strasse 51

81547 München Germany

Roger Härtl, MD Leonard and Fleur Harlan Clinical Scholar in Neurological Surgery

Associate Professor of Neurological Surgery Director of Spinal Surgery

Department of Neurological Surgery Weill Cornell Brain & Spine Center Starr Building, Room 651

525 East 68th Street New York, New York 10021 USA

Bronek Boszczyk, PD Dr med

Consultant Spinal Surgeon & Head of Service

The Centre for Spinal Studies and Surgery

Honorary Clinical Associate Professor Division of

Orthopaedic and Accident Surgery

Queen’s Medical Centre Campus, Derby Road, West

Block D Floor

Nottingham University Hospitals NHS Trust

Nottingham, NG7 2UH

United Kingdom

Salvador A Brau, MD, FACS

Director – Spine Access Surgery Associates

Visiting Clinical Assistant Professor of Surgery – Keck

School of Medicine – USC

Instructor in Surgery – Geffen School of Medicine –

UCLA

Los Angeles, CA 90095

USA

Dean Chou, MD

Associate Professor of Neurosurgery

Associate Director of Spine Tumor Surgery

Assistant Professor of Neurosurgery

Mayo Clinic School of Medicine

200 First Street SW,

Rochester, MN 55905

USA

Mark B Dekutoski, MD

Department of Orthopaedic Surgery

Associate Professor of Orthopaedics

Mayo Clinic School of Medicine

200 First Street Southwest,

Department of Neurosurgery, Suite 2210

676 North St Claire Avenue Chicago, IL 60611 USA

Daniel Gelb, MD Associate Professor and Vice Chairman Department of Orthopaedics University of Maryland School of Medicine

22 South Greene Street

S 11B Baltimore, MD 21201 USA

Alex Gitelman, MD ULCA Spine Center

1250 16th street Ste 715 Santa Monica, CA 90404 USA

Patrick Hahn, Dr med Center for Spine Surgery and Pain Therapy Center for Orthopaedics and Traumatology

St Anna Hospital Herne Hospitalstrasse 19

44649 Herne Germany Roger Härtl, MD Leonard and Fleur Harlan Clinical Scholar in Neurological Surgery

Associate Professor of Neurological Surgery Director of Spinal Surgery

Department of Neurological Surgery Weill Cornell Brain & Spine Center Starr Building, Room 651

525 East 68th Street New York, New York 10021 USA

Franziska C Heider, MD Spine Center

Schön Klinik München Harlaching Harlachinger Strasse 51

81547 München Germany

Paul F Heini, Prof Dr med Spine Service

Klinik Sonnenhof Buchserstrasse 30

3006 Bern Switzerland Paul S Issack, MS, MD, PhD Chief, Division of Adult Reconstructive Surgery New York Downtown Hospital

170 William Street, 8th Floor New York, NY 10038 Clinical Assistant Professor of Orthopaedic Surgery Weill Medical College of Cornell University USA

Andrew James, Dr Leeds General Infirmary Leeds Teaching Hospitals NHS Trust Great George Street

Leeds West Yorkshire LS1 3EX United Kingdom Sheila Kahwaty, Physician Assistant-Certified Cedars-Sinai Medical Center

8700 Beverly Boulevard Los Angeles, CA 90048 USA

Iain H Kalfas, MD Department of Neurosurgery Cleveland Clinic

9500 Euclid Avenue Cleveland, OH 44195 USA

Frank Kandziora, MD, PhD Zentrum für Wirbelsäulenchirurgie und Neurotrauma- tologie

Berufsgenossenschaftliche Unfallklinik Friedberger Landstraße 430

60389 Frankfurt am Main Germany

Rishi Mugesh Kanna, MS, MRCS, FNB

Associate Consultant Spine Surgeon

Department of Orthopaedics, Accident and Spine

UCLA School of Medicine

UCLA Spine Center

Martin Komp, Dr med

Center for Spine Surgery and Pain Therapy

Center for Orthopaedics and Traumatology

Thailand Khai Lam, MD Spinal Unit, Orthopaedic Department 1st Floor Bermondsey Wing Guy’s Hospital

St Thomas’ Street London, SE1 9RT United Kingdom Rondall K Lane, MD, MPH Assistant Professor in Residence UCSF School of Medicine Department Anesthesia/Perioperative Care

1600 Divisadero Street San Francisco, CA 94143 USA

Jeremy Lieberman, MD Professor

Chief, Division of Spine Anesthesia Department of Anesthesia & Perioperative Care Box 0648, Room C-450

521 Parnassus Avenue UCSF

San Francisco, CA 94143 USA

Steven C Ludwig, MD Associate Professor and Chief of Spine Surgery Director of Spine Surgery Fellowship Department of Orthopaedics University of Maryland Medical Center

22 South Greene Street Suite 22 SB Baltimore, MD 21201 USA

H Michael Mayer, MD, PhD Head of Department Spine Center Schön Klinik München Harlaching Harlachinger Strasse 51

81547 München Germany

John McCormick, MD Neurological and Orthopaedic Surgery University of Virginia

Charlottesville, Virginia 22908 USA

Paul C McCormick, MD, MPH, FAANS Herbert and Linda Gallen Professor of Neurological Surgery

Columbia University College of Physicians and Surgeons

710 West 168th Street New York, NY 10032 USA

Christoph Mehren, MD Head of Department Spine Center Schön Klinik München Harlaching Harlachinger Strasse 51

81547 München Germany Mark M Mikhael, MD Spine Surgery – Orthopaedic Surgery Illinois Bone and Joint Institute, LLC

2401 Ravine Way, Suite 200 Glenview, IL 60025 USA

Osmar JS Moraes, MD

R Maestro Cardim 592

11 andar Sao Paulo, SP 02313001 Brazil Yaron A Moshel, MD, PhD Assistant Professor Thomas Jefferson University Department of Neurological Surgery Division of Neuro-Oncology

909 Walnut Street, 2nd Floor Philadelphia, PA 19107 USA

Praveen V Mummaneni, MD

Associate Professor and Vice-chairman

Department of Neurosurgery

Co-director UCSF Spine Center

University of California, San Francisco

505 Parnassus Ave, M779

San Francisco, CA 94143

USA

Eric W Nottmeier, MD

Adjunct Associate Professor of Neurosurgery

Mayo Clinic College of Medicine

Neurosurgeon,

St Vincent’s Spine and Brain Institute

4205 Belfort Road, Suite 1100

Jacksonville, FL 32216

USA

Alfred T Ogden, MD

Assistant Professor of Neurological Surgery

The Neurological Institute

Columbia University

710 West 168th Street

New York, NY 10032

USA

Sylvain Palmer, MD, FACS

Neurological Surgery Medical Associates

Orange County Neurosurgical Associates

26732 Crown Valley Parkway, Suite 561

Mission Viejo, CA 92651

USA

Luca Papavero, Prof Dr med

Clinic for Spine Surgery,

Department of Orthopedic Surgery

Bumrungrad Spine Institute

Bumrungrad International Hospital,

Bangkok

Thailand

Noel I Perin, MD, FRCS(Ed) Professor Neurosurgery Department of Neurosurgery Suite 8-S

NYU Medical Center

530, 1st Avenue New York, NY 10016 USA

Mark Pichelmann, MD Assistant Professor of Neurosurgery Mayo Clinic School of Medicine

200 First Street Southwest, Rochester, MN 55905 USA

Luiz Pimenta, MD Instituto de Patologia da Coluna Specialist in minimally invasive spine surgery Rua Vergueiro no 1.421, sala: 305

São Paulo – SP Brazil Shanmuganathan Rajasekaran, Dr, PhD Ganga Hospital

313 Mettupalayam Road Coimbatore 641043 India

Marcus Richter, MD Chefarzt des Wirbelsäulenzentrums Facharzt für Orthopädie Facharzt für Orthopädie und Unfallchirurgie

St Josefs-Hospital Beethovenstrasse 20

65189 Wiesbaden Germany Daniel Riew, MD Mildred R Simon distinguished Professor of Orthopaedic Surgery

Professor of Neurological Surgery Chief, Cervical Spine Surgery McDonnell International Scholars Academy Ambassador Suite 11, 300 Pavillion

One Barnes-Jewish Plaza

St Louis, MI 63110 USA

Sebastian Ruetten, Priv.-Doz Dr med habil, MD Head Department of Spine Surgery and Pain Therapy Center for Orthopaedics and Traumatology

St Anna Hospital Herne Hospitalstrasse 19

44649 Herne Germany Rajiv Saigal, MD, PhD PGY-3, Department of Neurological Surgery University of California, San Francisco

505 Parnassus Avenue, M779 San Francisco, CA 94143 USA

Walter Saringer, Prof Dr med Medizinische Universität Wien Spitalgasse 23

1090 Wien Austria Philipp Schleicher, Dr Leiter Biomechaniklabor Zentrum für Wirbelsäulenchirurgie und Neurotraumatologie

Berufsgenossenschaftliche Unfallklinik Frankfurt am Main

Friedberger Landstrasse 430

60389 Frankfurt am Main Germany

Meic H Schmidt, MD, FACS Ronald I Apfelbaum Endowed Chair in Spine Surgery Associate Professor and Chief

Division of Spine Surgery Department of Neurosurgery Clinical Neurosciences Center Director, Spinal Oncology Service Huntsman Cancer Institute University of Utah

175 N Medical Drive East Salt Lake City, UT 84132 USA

Theodore H Schwartz, MD, FACS

Professor of Neurosurgery

Departments of Neurological Surgery, Neurology

Neuroscience and Otolaryngology

Weill Cornell Medical College

New York Presbyterian Hospital

525 East 68th Street, Box #99

New York, NY 10065

USA

Christopher I Shaffrey, MD, FACS

Harrison Distinguished Professor

Neurological and Orthopaedic Surgery

University of Virginia

Charlottesville, VA 22908

USA

Ajoy Prasad Shetty, MS DNB Ortho

Consultant Spine Surgeon

Department of Orthopaedics, Accident and Spine

Chicago, IL 60611 USA

Volker Sonntag, MD Vice Chairman, Department of Neurological Surgery Barrow Neurological Institute

350 West Thomas Road Phoenix, AZ 85013 USA

John Stark, MD Back Pain Clinic The Medical Arts Building

825 Nicollet Mall, Suite 715 Minneapolis, MN 55402 USA

Lukasz Terenowski, MD The Prof Alfred Sokolowsiki Memorial Specialistic Hospital

Department VI of Traumatic and Orthopaedic Surgery uliza Alfreda Sokołowskiego 11

70-001 Szczecin – Zdunowo Poland

William D Tobler, MD The Christ Hospital

2123 Auburn Avenue, Suite 441 Cincinnati, OH 45219 USA

Juan S Uribe, MD Assistant Professor Director, Spine Section Department of Neurological Surgery University of South Florida Tampa, FL 33620 USA

Jeffrey C Wang, MD Professor of Orthopaedics and Neurosurgery UCLA School of Medicine

UCLA Spine Center

1250 16th Street, Suite 745 Santa Monica, CA 90404 USA

Michael Y Wang, MD, FACS Associate Professor Departments of Neurological Surgery & Rehabilitation Medicine

University of Miami Miller School of Medicine Lois Pope LIFE Center, 2nd Floor

1095 Northwest 14th Terrace (D4-6) Miami, FL 33136

USA Jean-Paul Wolinsky, MD Associate Professor of Neurosurgery and Oncology Clinical Director of the Johns Hopkins Spine Program Johns Hopkins Hospital

600 North Wolfe Street, Meyer 7.109 Baltimore, MD 21287

USA James Zucherman, MD

St Mary’s Spine Center One Shrader Street, Suite 450 San Francisco, CA 94117 USA

Definition of the different classes of evidence table XVI

1.1 The definition of minimally invasive spine surgery 3

and the rationale for its use

1.2 Minimally invasive spine surgery and AOSpine 13

principles

1.3 The four pillars of minimally invasive spine surgery 23

1.4 Evidence-based medicine and minimally invasive spine 51

surgery

1.5 Different spinal pathologies and patient selection 57

1.6 Computer-assisted navigation for minimally invasive 67

spine surgery

1.7 Biologics in minimally invasive spine surgery 85

1.8 Anesthetic considerations and minimally invasive 91

spine surgery

Table of contents

5 Critical overview and outlook 483

5.1 Minimally invasive spine surgery: a critical overview 485 and outlook

3 Thoracic techniques 173

3.2 Extreme lateral mini-thoracotomy approach for 177

thoracic spinal pathologies

3.3 Anterior thoracoscopic approaches, including 191

fracture treatment

3.4 Posterior approaches for minimally invasive thoracic 211

decompression and stabilization

3.5 Posterior approaches for minimally invasive treatment 223

of spinal fractures

3.6 Vertebroplasty and percutaneous cement 243

reinforcement techniques

Definition of the different classes of evidence (CoE)

Definition of the different classes of evidence (CoE)

Articles on treatment

Studies of therapy Level Study design Criteria

I Good quality RCT • Concealment

• Blind or independent assessment for important outcomes

• Co-interventions applied equally

• Follow-up rate of ≥ 85%

• Adequate sample size

II Moderate or poor quality

RCT Good quality cohort

• Violation of any of the criteria for good quality RCT

• Blind or independent assessment in a prospective study, or use of reliable data*

in a retro study

• Co-interventions applied equally

• Follow-up rate of ≥ 85%

• Adequate sample size

• Control for possible confounding †III Moderate or poor quality

cohort Case control

• Violation of any of the criteria for good quality cohort

• Any case-control design

IV Case series • Any case-series design

Randomized Controlled Trial (RCT)

* Reliable data are data such as mortality or reoperation.

† Authors must provide a description of robust baseline characteristics, and control for those that are unequally

distributed between treatment.

(Reproduced with kind permission from the AOSpine Evidence-Based Spine-Care Journal (EBSJ).)

Author Andreas Korge

1 Fundamentals

1.1 The definition of minimally invasive spine surgery and the rationale for its use

Author Andreas Korge

1 Rationale

Spine surgery was initially referred to in anecdotal reports

at the beginning of the 20th century, but later developed

to increasingly cover all the anatomical regions of the

ver-tebral column With time, a better understanding of the

pathologies underlying the visible symptoms and

improve-ments in diagnostic tools and surgical equipment led to a

dramatic increase in surgical treatment strategies from the

1950s onwards Macrosurgical exposures were accepted as

standard practice at the time, since treatment goals focused

predominantly on target surgery and its practicability

However, macrosurgical exposures are associated with a

large number of side effects including significant muscle

damage and increased bleeding, muscular denervation,

re-duced segmental innervation, as well as a decreased or even

severely compromised local blood supply with postoperative

sequelae such as scar-tissue formation and local pain

syn-dromes Further postoperative side effects include the need

for prolonged pain medication, a longer immobilization and

recovery period accompanied by an extended period of

physical disability and delayed return to work, and

some-times with a limited possibility, or even in some cases no

possibility, of resuming previous professional activity

In consequence, the importance of effective approach

mo-dalities has become increasingly apparent, and particular

focus has been placed on the optimization of access

strate-gies through minimizing the anatomical working corridor

while simultaneously maintaining the treatment aims of

standard open surgery The measures used to decrease

in-traoperative iatrogenic tissue trauma include reducing

ac-cess size, making smaller incisions, and using preexisting

anatomical neurovascular and muscle compartment

work-ing planes, with the aim of achievwork-ing similar, or if possible,

better postoperative results than those obtained via standard

open procedures [1, 2] Less muscle damage as a result of

muscle-splitting dissection rather than muscle-cutting

tech-niques, and reduced blood loss due to meticulous

hemo-stasis with less postoperative scar-tissue formation, have

led to a decrease in postoperative pain symptoms with less pain medication, and to a reduction in overall morbidity with a quicker recovery time and a shorter hospitalization period With so many obvious potential benefits, special emphasis was placed on minimally invasive spine surgery (MISS) from the early 1990s onwards While access modi-fications dominated the results in the literature during the first MISS decade [3, 4], after the year 2000, outcome stud-ies focused on the question of whether the high expectations regarding MISS were justified, and whether they had been met [5–9] Recent studies now increasingly concentrate on evidence-based outcome evaluation [10–14], and in this context reference is also made to the individual chapters of this book

Modifications in access strategies should not compromise the goal of the surgical procedure, independent of the type

of pathology involved Even if this is not always possible in the beginning when first using a modified surgical technique that requires a learning curve, this goal must be strived for

For example, at the onset, percutaneous pedicle screw ment for fusion surgery was limited to mono- and biseg-mental cases of in situ fusion Technical advances now en-able multisegmental pedicle screw insertion and segmental reduction to be performed; surgery, for example, is facili-tated by computer-assisted navigation; and cement aug-mentation techniques are available, so that the range of indications for treatment by MISS is now nearly the same

place-as for open surgery

Among the many other examples given in historical reviews [15, 16], typical examples of minimalized treatment strategies are the development of posterior mini-open or percutane-ous pedicle screw placement techniques in combination with minimally invasive transforaminal intervertebral (mini-TLIF) or anterior intervertebral (mini-ALIF) implant placement (Fig 1.1-1) [4, 9,17] Video-assisted thoracoscopic surgery for decompression or fusion procedures has been developed for the treatment of the thoracic spine [18], while for the cervical spine, even for a single anatomical region (ie, the atlantoaxial segment C1/2), four different anterior

1.1 The definition of minimally invasive spine surgery and

the rationale for its use

Andreas Korge

Author Andreas Korge

minimally invasive techniques are now available (see

chap-ter 2.5 Anchap-terior C1/2 surgery) Today, a wide range of

minimally invasive surgical procedures can be applied for

the treatment of the entire spine (Table 1.1-1, Table 1.1-2)

However, the variety and number of minimally invasive

procedures that can currently be performed have only been

made possible by the introduction of numerous technical

innovations within the last decades These can be

summa-rized as the four “pillars” of MISS (see chapter 1.3 The four

pillars of MISS in this section), namely: microsurgical

tech-niques; access strategies to the spine; imaging/navigation

techniques; and instrumentation and implants To mention

but a few of these developments, improved visualization

with magnification and illumination of the target area is

ensured by the use of high-end microscopes, endoscopes

or head lamps with adequate xenon light sources (Fig 1.1-2)

Instruments have been further modified, enabling the

sur-geon to operate within a narrow working channel; for

ex-ample, bayonet-shaped instruments and high-speed drills,

etc ensure a virtually unrestricted visual field under

mi-Fig 1.1-1a–b Posterior percutaneous pedicle screw placement at L4/5 after initial anterior cage implantation using a mini-ALIF technique.

a Insertion tubes with adapted screws in place on the right side; on the left side, completed screw-rod implantation, with only the skin incisions visible.

b Intraoperative AP x-ray showing the insertion tubes with screws in place on the right side and completed left-sided instrumentation.

Cervical spine Foraminotomy

Microfacetectomy Craniocervical junction decompression Laminoplasty

Fusion procedures with instrumentation (eg, transpedicular, translaminar, lateral mass)

Skip laminectomy Thoracic spine Costotransversectomy

Transpedicular decompression surgery Laminotomy

Vertebral body augmentation (vertebroplasty/kyphoplasty) Fusion procedures (percutaneous pedicle screw placement) Lumbar spine Decompression surgery (disc pathologies, synovial cysts,

acquired spinal stenosis)

• Medial and paramedian

• Intraforaminal and extraforaminal Vertebral body augmentation (vertebroplasty/kyphoplasty) Lordoplasty

Dynamic nonfusion techniques (incl nucleus replacement) Fusion procedures (eg, percutaneous pedicle screw placement, translaminar screws, transsacral techniques) Intervertebral support (mini-PLIF, TLIF)

Cervical spine Uncoforaminotomy

Decompression surgery (eg, intervertebral, transnasal, transoral)

Fusion procedures (eg, cages, plates) Total disc replacement

Vertebral artery decompression Thoracic spine Decompression surgery (eg, disc pathologies, fracture)

Fusion procedures (eg, cages, plates) Lumbar spine Total disc replacement

Nucleus replacement Fusion procedures (cages, plates)—mini-ALIF

• Anterior, anterolateral, lateral Spinal canal decompression Anterior extraforaminal decompression Vertebral body augmentation Tumor marginal resection/curettage Table 1.1-1 Minimally invasive spine surgery—applications using

1 Fundamentals

1.1 The definition of minimally invasive spine surgery and the rationale for its use

of the procedure With careful preparation, both surgeon and patient should be able to benefit from the potentially positive aspects of MISS: less tissue trauma, reduced bleeding and scar-tissue formation, decreased pain with quicker mobiliza-tion and recovery time, shorter hospital stay, and a more rapid return to daily activities at both a professional and per-sonal level (Fig 1.1-4) It is most important that these approach modifications do not influence the treatment strategy at the target site itself, which should be independent of the size of the access pathway, and be adequate and identical for both macro- and microsurgical approaches

Minimally invasive spine surgery has been defined as: “(a)

procedure that by virtue of the extent and means of surgical

techniques results in less collateral tissue damage, resulting

in measurable decrease in morbidity and more rapid

func-tional recovery than tradifunc-tional exposures, without

differen-tiation in the intended surgical goal” [19] The present author

subscribes to this view In an effective minimally invasive

spine operation today, one of the major aspects of

preopera-tive preparation, which has a significant effect both on the

intraoperative procedure and the postoperative results, is the

meticulous decision-making process and thorough planning

Fig 1.1-2a–b

a Microscopic view of the spinal canal at L4/5 with a large synovial cyst compressing

the hidden nerve root L5

b Microscopic view of the spinal canal at L4/5 after removal of the synovial cyst with

decompressed and now visible nerve L5.

Fig 1.1-3 Tube placed over disc space at L4/5 left in preparation for interbody work, with K-wires already positioned bilaterally through pedicles L4 and L5 for percutaneous screw placement using a Wiltse type approach.

Medial

Dura

Dura Nerve root L5 Synovial cyst

Smaller incision

Less soft-tissue damage

Less blood loss

Lower complication rate

Less scarring Less postoperative pain

Quicker recovery

Shorter hospital stay

Quicker return to DLA

Author Andreas Korge

2 Learning curve

As with the use of any new technique, the first attempts at

performing minimally invasive surgical approaches will also

involve learning the procedure itself, how to handle new

instruments correctly, and specific implants if required

Ac-cepting a relatively steep learning curve and at the onset

an extended time for surgery must be taken into account

In addition, any learning curve will also have a certain

ef-Fig 1.1-5a–c Examples of learning curves in MISS in relation to complication rates.

a Between-group comparison of MISS surgeons over a 6-year period.

“a” and “b”: surgeons that were experienced in microsurgery of the entire spine, who performed the most difficult procedures;

“c”, “d”, “e”, and “f”: surgeons that were initially less skilled in the new techniques, but who later gained increasing microsurgical experience

(red bars: complication rate [in %]); final team aim: to reduce the complication rate to below 5%

b Development of complication rates over a 5-year period for MISS procedures performed by an experienced spine surgeon familiar with spine

microsurgery.

c Development of complication rates over a 2-year period for MISS procedures performed by spine surgeons inexperienced in MISS, who

adopted this technique in 2008, showing a significant reduction in complication rates over time.

18 16 14 12 10 8 6 4 2 0

fect on, eg, intraoperative tissue trauma, blood loss and so

on, and will also include an initially increased complication rate [20–22] The specific learning curve will depend on the type of surgery in question and the acquired skills of the individual surgeon Care must be taken when using new tools to avoid making any inappropriate surgical gesture, and caution should be exercised to avoid overestimating surgical ability Even for experienced surgeons, a certain learning curve will always exist (Fig 1.1-5)

1 Fundamentals

1.1 The definition of minimally invasive spine surgery and the rationale for its use

size to the well-known macrosurgical length when pared to an endoscopic technique

com-Accepting the existence of a learning curve, and adopting

a strategy like doing more straightforward cases at the set with meticulous patient selection will help to reduce any frustration regarding the new technique, or limit a tendency to keep within the limits of known standard pro-cedures Also helpful is when the first MISS cases can be treated together with an experienced MISS surgeon, as is possible in, eg, percutaneous pedicle screw placement, with each surgeon dealing with his side Participating in human anatomical specimen workshops on the chosen surgical technique will further optimize the learning curve In the literature, it has been reported that the number of interven-tions required for a surgeon to become familiar with a spe-cific MISS procedure ranges between 10 and 20, depending

on-on the type of surgery [23, 24] However, the author ers that these procedures can only become good routine practice with an effective intraoperative workflow after at least 30 cases in succession have been performed, with a subsequent 30 cases per year treated thereafter If a sufficient number of minimally invasive cases are not available for routine surgery, the author suggests that it might be advis-able to keep to the same familiar and established macro-surgical procedures In fact, eg, for posterior fusion of the lumbar spine, more than 90% of all surgical interventions are still currently performed using a macrosurgical or only

consid-a limited microsurgicconsid-al consid-approconsid-ach (Fig 1.1-7)

It is always easier to take a standard, familiar technique

using a macrosurgical access with a large incision and

mod-ify it to a microsurgical procedure by reducing the length

of the incision than to adopt an entirely different approach

and philosophy For example, in the case of a

mono-segmental thoracic pathology, in traditional open

macro-surgery, a large thoracotomy is performed, with rib

resec-tion starting 1–2 disc spaces cranially from the affected

target area However, in minimally invasive open

trans-thoracic surgery with a modified access technique, the

sur-geon has to meet the challenge of placing the skin incision

directly over the pathology, while gradually minimizing

the skin incision as much as possible (Fig 1.1-6; and see

chapter 3.2 Extreme lateral mini-thoracotomy approach

for thoracic spinal pathologies) The entire setup required

for MISS will not differ greatly, especially when

micro-surgery is to be performed for other surgical interventions

and the use of a microscope, etc, is part of routine practice

But if the surgeon switches to video-assisted transthoracic

surgery for the treatment of the same pathology, this

tech-nique will include the use of endoscopes with new access

portals and a different three-dimensional orientation

with-in the thoracic cavity, a new set of with-instruments, and

poten-tially different implants—moreover, with an additionally

stressful and different, new visual working axis (see

chap-ter 3.3 Anchap-terior thoracoscopic approaches, including

frac-ture treatment) In the event of an intraoperative

compli-cation, it will be easier to deal with the problem when

using a mini-open technique by just enlarging the incision

Fig 1.1-6 Marking the incision line for a minimalized transthoracic microscopically-assisted approach for the treatment of a L1 fracture Red line: theoretical placing and size of a macrosurgical skin incision, which is usually even larger; continuous black line: microsurgical incision line; all four borders of the target vertebral body at L1 have been marked.

Posterior

Caudal

Anterior Cranial

Fig 1.1-7 Access progression for posterior fusion surgery of the lumbar spine

More than 90% of surgeries are currently performed by either open macrosurgical approaches or with an only slightly reduced approach extent

(ie, within the range “Open” to “Mini-open”); MISS includes a variety of approach modifications ranging from “Controlled open” to finger-size incisions.

Author Andreas Korge

Posterior fusion surgery of the lumbar spine

1 Fundamentals

1.1 The definition of minimally invasive spine surgery and the rationale for its use

bar interbody fusion (TLIF) when compared to a certain amount of radiation exposure (12.4 mRem) without navi-gational assistance [30] Transposition of the study design

to an in vivo evaluation demonstrated a statistically nificant reduction of total image intensification time in the navigation group of more than 50% Similar results with a significant reduction in image intensification time (77%

sig-reduction) and radiation dose (60% reduction for the hand and 32% for the body) were found when an electromag-netic navigation system was used for percutaneous pedicle screw placement in comparison to standard image-inten-sifier-guided placement [31] However, it should be noted that radiation dose to the individual patient is higher when CT-based datasets are used

In addition to the beneficial effect of reduced radiation posure to the surgeon, computer-assisted or electromag-netic image-guided navigation as well as computerized isocentric image intensification significantly improve the accuracy of percutaneously inserted pedicle screws, thus decreasing the risk of screw misplacement [31–34] Despite the increased setup time involved, the overall time for navigation-based surgery compared to that for surgery us-ing standard intraoperative image intensification does not differ, as there is no difference in the results regarding blood loss, exposure time or hospital stay between these treatment strategies [30, 31]

ex-4 Cost effectiveness

New technologies for both access and target surgery

most-ly require a significant initial investment in operating-room setup (eg, carbon table for isocentric C-arm 3-D image-intensifier navigation, video screens), instruments (eg, bayonet-shaped instruments, endoscopic equipment), and implants (eg, cannulated screws for percutaneous pedicle screw placement), and other tools being more or less cost-intensive Adopting these new technologies may involve a single investment, or require repetitive investments in sur-gical material/setup

Once the prerequisites for MISS have been determined, when considering the overall benefit of this new surgical strategy in terms of direct and indirect costs, the cost-anal-ysis and cost-effectiveness aspects must be taken into ac-count [35] Sources of direct cost include factors such as those related to time (duration of stay in the emergency room and intensive care unit; time in the operating room,

eg, the duration of surgery; length of hospital stay), tional investigations (such as laboratory, radiological, or

addi-3 Radiation exposure

The minimization of an access route inevitably leads to more

limited visualization of the surgical field, or to no

visualiza-tion whatsoever The use of x-ray imaging for local

orienta-tion therefore prevails, as visual anatomical landmarks that

were once familiar under macrosurgical conditions may be

indistinguishable or obscured Imaging tools are

manda-tory at the preoperative stage for meticulous localization,

and also intraoperatively for verification of the target area

This is the case for both soft tissue and osseous pathologies

Moreover, as regards, eg, vertebral body augmentation

(ver-tebroplasty, kyphoplasty) and fusion surgery, certain

pro-cedures require repeated x-ray monitoring of individual

intraoperative surgical steps like cement distribution,

reduc-tion maneuvers, or pedicle screw placement As a result,

the radiation dose to the patient, surgeon and support staff

may increase, depending on the type of MISS [25–27]

In-traoperative use of leaded glasses, thyroid shields, and lead

aprons help to reduce local radiation exposure

Standard image intensification with an image intensifier

and/or pre- and intraoperative CT scan is the most

fre-quently used imaging tool With standard image

intensifica-tion, both patient and surgeon are subjected to radiation

exposure in low and limited amounts in the case of a single

procedure [28] However, repeated radiation exposure due

to image intensifier-assisted surgical interventions that are

continuously performed over time leads to an increased

overall radiation dose to the surgeon, predominantly

involv-ing the hand, eye, and other exposed parts of the body

Careful dose monitoring is therefore mandatory in order to

avoid exceeding annual dose limits

Differences in radiation dose have been demonstrated in

an in vivo study comparing two different microdiscectomy

procedures [29] Standard microdiscectomy generally

re-quires two lateral images, ie, a preoperative view for segment

localization and an intraoperative view for target area

ver-ification In comparison, MISS lumbar microdiscectomy

using tubular retractors requires several image-intensifier

views for level verification, dilator positioning and tube

placement, resulting in a 10- to 20-fold potential increase

in the amount of radiation dose

Computer-assisted navigation with preoperative or

intra-operative CT-scan or image intensifier-based datasets helps

to reduce the amount of radiation exposure to the surgeon

A human anatomical specimen study demonstrated that no

radiation was detectable when computer-assisted navigation

with image intensification was used for transforaminal

lum-Author Andreas Korge

compared to standard open procedures Further studies with longer-term follow-up are necessary to evaluate the effect

of MISS on both direct and indirect costs in order to mine the possible financial benefit of the latter technique compared to open spine surgery

deter-The length of hospital stay (LOS) connected with surgical interventions is a matter of ongoing debate at scientific meetings, and a subject of controversy in the literature

Length of hospital stay is without any doubt directly lated to cost-effectiveness Since, however, the reimburse-ment systems for identical treatment procedures vary sig-nificantly in different countries and healthcare systems, LOS is a parameter of relatively limited value when com-paring the economic impact of different minimally invasive

re-or macrosurgical strategies, in that the predefined minimum LOS periods determine hospital reimbursement, and bear-ing in mind that financial deductions are made if the LOS falls below the pre-established lower limits for LOS (as is the case in Germany)

5 Summary

• Minimally invasive spine surgery consists of ized modifications of established access strategies that have been introduced without changing or modifying the surgical goal

miniatur-• Benefits of minimally invasive spine surgery include smaller skin incisions and less soft-tissue damage, result-ing in reduced blood loss and lower complication rates with decreased scar-tissue formation, reduced postop-erative pain and need for pain medication, quicker re-covery and shorter hospital stay, with more rapid return

to work and daily activities

• A learning curve must be taken into account when ciding to use MISS techniques

de-• Radiation dose is increased in specific MISS procedures, however, the use of intraoperative navigation reduces radiation exposure to the surgeon and operating-room staff

• Long-term studies are necessary to determine the efits of MISS in terms of cost-effectiveness, which has already been documented in short-term follow-up

ben-interdisciplinary investigation, eg, cardiology), other

ex-penses (eg, board, medication, blood units), and

profes-sional fees (eg, surgeon, anesthetist), which together

con-tribute to the overall cost of MISS However, over time,

indirect costs in fact make up approximately 85% of the

total costs! [36] Indirect costs among others include

post-operative factors such as patient rehabilitation, delayed

return to work, loss of productivity, the possible inability

to work, and unplanned early retirement It should also be

noted that the surgeon’s learning curve, at least initially,

may influence the cost-effectiveness of a given procedure

Several studies have been made comparing the financial

aspects of MISS strategies with those of open procedures

for different pathologies In a 2-year cost-utility study

com-paring a minimally invasive transmuscular tubular

tech-nique versus an open midline retractor-assisted multilevel

hemilaminectomy for lumbar stenosis, Parker et al [37] found

that with an identical postoperative health status, both

techniques were cost-equivalent As postoperative

infec-tions are to a large extent responsible for the financial

bur-den involved, and as it is reported that MISS is associated

with a significantly reduced infection rate when compared

to open surgery (0.6% for MISS versus 4% for open surgery,

based on a literature review of 1495 TLIFs), the use of MISS

techniques in terms of direct costs constitutes a possible

economic advantage [38] In addition, retrospective

analy-sis shows the superior cost-saving aspects of MISS compared

to open procedures for TLIF in terms of direct costs,

includ-ing more rapid patient mobilization and quicker discharge

from hospital, as well as reduced laboratory and medication

costs [39, 40] As far as the economic aspects are concerned,

little doubt exists that for a monosegmental pathology, the

exclusive use of posterior surgery (TLIF) will limit the

cost involved compared to a combined anterior-posterior

strategy (anterior-posterior interbody fusion) in terms of

reduced time of surgery, shorter stay in the intensive care

unit, less blood loss, and shorter period of hospitalization

[41]

Although the above-mentioned studies show a tendency

towards the greater cost-effectiveness of certain MISS

pro-cedures, at the present time insufficient studies are available

to clearly demonstrate the superiority of MISS in this regard

1 Fundamentals

1.1 The definition of minimally invasive spine surgery and the rationale for its use

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1 Principles of minimally invasive spine surgery

In the history of surgery, reducing iatrogenic tissue trauma

to a minimum has always been regarded as one of the basic

principles Modern surgical techniques and technology have

shifted this goal into a new dimension In spine surgery,

the last decade of the 20th century was marked by

signifi-cant advances in the field of minimally invasive surgical

procedures These developments continue to follow basic

principles, and what can almost be qualified as a philosophy

regarding minimally invasive surgery

1.1 Goals

The aim of every surgical procedure is to resolve the patient’s

clinical problem by treating the underlying pathology (Table

1.2-1) This pathology can be considered as the target of each

surgical procedure So one of the goals of minimally invasive

spine surgery (MISS) is to carry out efficient “target surgery”

with a minimum of iatrogenic trauma To attain this target,

the surgeon has to create an access to it So practically

speak-ing, either the access part or the target part of the surgical

procedure—or both—can be minimally invasive

The majority of minimally invasive techniques in spine

sur-gery primarily concern the access, and not what is performed

in the target region

1.2 Access surgery

The spine can be accessed from different directions through different entry points (Table 1.2-2)

The surgical entry point (skin incision) is usually determined

by the topography of the target region and access anatomy

For MISS, it must be adequately placed and should be as small as possible in size The cosmetic aspects must be tak-

en into consideration (eg, placement, length, and tion of skin incision)

orienta-The surgical route to the target area should be reasonably fast, and must follow strict anatomical pathways, such as preexisting spaces; or, when this is not possible, access sur-gery should be performed with a minimum of collateral damage to the surrounding tissues If collateral damage cannot be avoided, it should be reparable or at least have minimal effects on the clinical outcome Whenever possible, muscular and/or ligamentous function should be fully pre-served

1.2 Minimally invasive spine surgery and AOSpine principles

Surgical dissection techniques

Instruments and implants

Skin incision Accurate placement

Adequate size Cosmetic aspects Route to target area Fast

The least traumatic (anatomical pathways!) Collateral damage Negligible

Reparable

Target treatment Efficient

Unrestricted due to small approach Surgical dissection techniques Negligible

Not relevant for outcome Risk of symptom recurrence, etc

Author H Michael Mayer

1.5 Patient positioning

The positioning of the patient can strongly influence the minimally invasive exposure as well as the target surgery

Preoperative positioning in MISS must enable the surgeon

to operate without having to adjust the patient’s position intraoperatively It should aim at reducing or avoiding col-lateral damage, such as pressure sores, and facilitate surgical dissection Examples of this are lateral positioning and access

to the lumbar levels L2–4 for anterior lumbar interbody sion (ALIF), which allows easier access to the spine even in obese patients; or the knee-chest position in patients un-dergoing lumbar discectomy or decompression procedures, which allows pressure release within the epidural venous system and thus reduces the risk of epidural bleeding

fu-1.6 Skin incisions

In MISS, skin incisions should be as small as possible This implies an accurate localization of the incision in terms of the target area to be reached In the majority of mini-open techniques, the skin incision is made directly above the tar-get In endoscopic techniques, localization of the incision(s)

is determined by the intended working direction as well as

by the angles of view required during the operation

1.7 Surgical dissection techniques

Surgical dissection techniques differ according to the type

of tissue that is to be treated (eg, nerve versus bone; muscle versus blood vessel) An improved knowledge of the struc-ture and function of these tissues has modified traditional surgical dissection techniques In MISS, it has gained even more significance

A muscle or a bone structure should basically be treated with the same care as a nerve or a blood vessel Blunt mus-cle-splitting techniques are characteristic of MISS The use

of high-speed burrs instead of large rongeurs can help to preserve bone structures The individual mobilization of blood vessels can decrease the vascular complication rate

The use of hemostatic agents in spinal canal surgery can reduce the risk of epidural hematoma The microsurgical closure of the annulus fibrosus is aimed at promoting the healing potential of this structure, which is generally re-garded as low

1.3 Target surgery

One of the most important considerations in MISS,

how-ever, is to provide adequate exposure of the target area

The target (eg, disc herniation, disc, spinal nerve, tumor)

must be identified and clearly visible Treatment of the

un-derlying pathology (eg, via discectomy, vertebrectomy,

neurolysis, tumor removal) should be given full priority,

and it must be possible to carry this out without any of the

potential compromises that MISS approaches might come

with Spinal manipulation (eg, reduction maneuvers) should

also be possible, as well as the insertion of implants for

spinal stabilization

Retreat from the surgical field should leave no or only

mi-nor traces, such as hematoma, open annulus fibrosus

fol-lowing discectomy, or scar tissue; and any minor sequelae

should not have an effect on the clinical outcome (eg,

muscle damage) In the case of staged surgical therapy (eg,

dynamic posterior stabilization) or when there is a risk of

pathological recurrence (eg, disc herniations), the

postop-erative sequelae, such as scar tissue, muscle or intervertebral

joint damage should not be such that they negatively affect

these further therapeutic options

1.4 Preoperative planning

To achieve all the above-mentioned goals, meticulous

pre-operative planning is necessary Positioning of the patient

on the operating table requires specific modifications

Lo-calization of the entry area under image intensifier control

is mandatory, and surgical preparation techniques must be

adapted to the surgery in question Special instruments,

light and magnification sources (eg, loupe, surgical

micro-scope, head lamp), as well as retractor devices (eg, frame

or ring retractors, tubes) are necessary Positioning of the

equipment and operating room personnel may require

cer-tain modifications Moreover, the topography and

“volu-metry” of the surgical target area must be clearly determined

before the operation

This information is usually obtained via different imaging

techniques, such as MRI and CT scan Preoperative

vascu-lar topography can be determined with the help of

color-coded three-dimensional CT scans, which provide a clear

picture of the individual anatomy The nature and extent

of previous operations in the target—or access—region

should also be taken into account, because they may

influ-ence the access strategy

dur-Each of the AOSpine principles can be applied and adapted

to different groups of pathologies, such as degeneration, trauma, deformity, tumor, and infection, or to metabolic, inflammatory, or genetic diseases

There is no general or natural consistency between the AOSpine principles and MISS tenets However, the goal should be that MISS techniques take into account AOSpine principles and put them into practice whenever appropriate

3 AOSpine principles for different pathologies3.1 Degeneration

In the treatment of degenerative disorders, the four AOSpine principles imply the protection of adjacent segments (stability), restoration of balance in the case of degenerative deformities (alignment), assessment of the outcome of in-terventions (function) as well as determination of the patho-genesis of spinal degeneration (biology) (Fig 1.2-2)

3.2 Trauma

In the treatment of traumatic disorders, stability means the application of biomechanical principles of internal fixation (Fig 1.2-3) Achieving alignment, ie, the reduction and resto-ration of pretraumatic alignment, is as vital as the protection

of neural elements and the enhancement of bone healing (biology) With regard to function, the preservation of healthy motion segments is of major importance

3.3 Deformity

The goal of achieving stability acquires particular cance, for instance in the case of surgical treatment of junc-tional instabilities at the end zones of a deformity (Fig 1.2-4)

signifi-In deformity surgery, correct spinal alignment depends

on proper balancing in all planes, while adequate function

1.8 Instruments and implants

Minimally invasive spine surgery is not possible without

the use of optical aids Light and magnification are needed,

and are introduced through small skin incisions to illuminate

and visualize the surgical target area that may lie deep

within the body The minimum prerequisites for the surgeon

are head lamps and loupes The surgical microscope and/

or endoscope are helpful, or even mandatory for certain

techniques Surgical instruments should be bayoneted and/

or sufficiently long to bridge the distance from the skin to

the target area The electrocautery instrument tips must be

isolated to prevent thermal damage to the tissues in the

access region

One of the major challenges over the coming years lies in

the further development of instruments and implants which

will allow for improved intraoperative spinal manipulation

(reduction, correction) and fixation Last but not least, tubes

or frame-type retractor systems are essential for keeping

the surgical corridor open

2 The AOSpine principles

AOSpine education has elaborated on four basic principles,

which can be universally applied to every diagnostic and

treatment strategy for different pathologies These principles

are: stability, alignment, function, and biology (Fig 1.2-1)

2.1 Stability

Each type of surgical treatment of the spine aims at the

restoration and preservation of segmental stability, and the

achievement of a specific therapeutic outcome For many

years, as far as spine surgery was concerned, stability

tend-ed to be synonymous with the rigid “fixation” of spinal

segments, ie, fusion This has changed in the last decade

with the introduction of procedures and implants which

enable the surgeon to achieve dynamic, motion-preserving

stability

2.2 Alignment

Alignment implies achieving spinal balance in three

dimen-sions For a number of years the importance of alignment,

especially in fusion surgery of the spine, was

underesti-mated Surgeons who performed surgery on anatomical

deformities were the first to realize the importance of

sag-ittal balance The fusion of spinal segments without fully

taking into account proper alignment limits the ability to

achieve a three-dimensional balance

Author H Michael Mayer

implies the preservation of as many mobile segments as

possible An evaluation of the etiology, pathogenesis, and

natural history of the spinal deformity in question forms

the basis of each therapeutic strategy

3.4 Infection

Achieving stability may also involve performing surgery to

treat any pathological instability due to infection Restoring

balance in the case of a postinfective deformity means

achieving alignment The other two principles that can be

seen in the treatment of spinal infection are the

preserva-tion of neurological funcpreserva-tion (funcpreserva-tion) and the use of

ad-equate and appropriate chemotherapy (biology) (Fig 1.2-5)

3.5 Tumors

The main reasons for applying surgical treatment to spinal

tumors are to decompress neural structures and to remove

the tumor The majority of tumors affecting the spinal

col-umn are malignant neoplasms En-bloc resection of the

tumor and the surrounding healthy structures, which can

“cure” the patient, is rarely possible In any type of surgical

treatment, however, the structural integrity of the spine

and its functional motion segments are affected So

restor-ing or keeprestor-ing a sufficient level of stability, usrestor-ing various

implants (pedicle screws, vertebral body relacement etc),

is a paramount goal in tumor surgery Stability is only

use-ful if it is achieved in a well aligned spine Destructing tumors

often leads to deformities, such as segmental kyphosis, which needs to be corrected in order to achieve good clinical outcomes Even though, in many tumors, larger surgical approaches that guarantee a maximum resection need to

be applied, MISS approach techniques have become very useful in palliative tumor treatment (eg, spinal metastasis)

The spectrum ranges from simple percutaneous plasty procedures, through to percutaneous pedicle screw stabilization, or thoracoscopic vertebrectomies These tech-niques reduce perioperative morbidity and enable a faster recovery, and thus have faster functional restoration, which

vertebro-is particularly important for patients with a limited life pectancy due to their malignant tumor MISS techniques currently do not allow radical tumor resection, however, reduced tissue trauma is important for better wound heal-ing, especially in patients that are immunosuppressed due

ex-to chemotherapy and/or irradiation (Fig 1.2-6)

3.6 Metabolic, inflammatory, and genetic

Assessment of the need for augmentation of an rotic spine addresses the principle of stability Alignment means the restoration of balance in any type of deformity associated with metabolic, inflammatory, or genetic disorders Biology implies the use of appropriate medical therapy, and a good functional outcome can be assessed by quality of life, and the satisfactory maintenance thereof (Fig 1.2-7)

and tissue healing.

Alignment Balancing the spine in three dimensions.

Function Preservation and restoration of function to prevent disability.

Fig 1.2-1 The four AOSpine principles to be considered as the foundation for proper spinal patient management.

Axial

Sagittal

Coronal

Author H Michael Mayer

of spinal arthrodesis on the adjacent mobile segments have led to the development of many nonfusion inter- ventions with the aim of achieving pain reduction and functional improvement without sacrificing mobility.

Biology Understand the pathogenesis of spinal degene- ration

Although spinal degeneration is a natural aging process, many patients develop disabilities due to pain, loss of function, or compressive neurological syndromes For therapeutic interventions aimed at relieving pain, restoring function, or decompressing neural elements the possibility of future progression of degeneration at treated and untreated levels must also

be considered Future biological interventions, such as stem cell implants or biomechanically active implants, may not be possible if previous surgical interventions preclude their use when they become available.

Biology Protect the neural elements and enhance bone healing

Protection of the spinal cord and spinal nerves following trauma is paramount Maintenance of adequate oxygenation and perfusion of the cord is essential during initial resuscitation In the presence of neurological deficit, early reduction of displacements and decompression of neural structures may improve neurological recovery Bone healing is vital for main- tenance of spinal alignment, stability, and function

Augmentation with bone grafts, bone growth factors, or vertebroplasty may be required.

Function Measure outcomes of interventions Functional outcome tools that measure the benefits and costs of therapeutic interventions for spinal dege- neration are essential to allow surgeons, physicians, patients, and funding bodies to assess their efficacy.

Function Preserve motion segments Early mobilization after spinal trauma minimizes the risks of recumbency Spinal trauma implants must be able to resist the stresses of spinal loading during bone healing or be protected by external supports Long- segment constructs resist deformity but sacrifice moti-

on at normal levels Short-segment fixation is preferred

in the lumbar region to maintain motion segments.

Alignment Restore balance in degenerative deformity Degenerative scoliosis, kyphosis, and spondylolis- thesis often result in spinal imbalance Particularly

in the elderly, imbalance of the sagittal plane is not well tolerated The goal of corrective surgery for degenerative deformity should be to restore alignment and balance In the lumbar spine this usually requires long fusions extending into the thoracic region above and the lumbosacral junction below in order to avoid decompensation if the fusion is too short.

Alignment Restore normal alignment Normal spinal alignment balances the head and thorax over the lower limbs In the sagittal plane the gravity line of the center of body mass passes through the junctional regions of the spine, then through the fe- moral heads In the coronal plane the head is centered over the sacrum Correction of malalignment following trauma is essential for optimal spinal function.

Fig 1.2-2 The AOSpine principles for the

treatment of degeneration.

Fig 1.2-3 The AOSpine principles for the

treatment of traumatic disorders.

Stabilize pathological instability in spinal infection Instability of the spine following infection can result from the destruction of bone by the infective process

or following surgical debridement or decompression

Reconstruction with interbody grafts or cages and rigid internal fixation is required Current evidence suggests that the addition of internal fixation does not increase the likelihood of recurrence of infection.

Biology Evaluate etiology, pathogenesis, natural history The underlying cause and specific pathogenesis of each spinal deformity determines the natural history of the condition Surgical interventions with their potential risks need to be balanced against the likelihood of improving the natural history, such as avoiding future complications of the untreated condition.

Biology Use appropriate chemotherapy Confirmation of the causative organism in spinal infection is best obtained by CT biopsy Appropriate antibacterial or antituberculous chemotherapy is the mainstay of treating spinal infection Duration of treatment is determined by the nature of the infection and the condition of the patient.

Function Preserve motion segments Long spinal fusions for deformity correction are often necessary and frequently involve extension into the lumbar spine or sacropelvic area, sacrificing motion segments Adequate preoperative planning and consi- deration of anterior instrumentation can often preserve levels for future mobility.

Function Preserve neurological function The presence of neurological compromise by extension

of an abscess into the epidural space or kyphotic compression requires surgical decompression, with or without reconstruction and stabilization.

Alignment Aim for balance in all planes Spinal imbalance in coronal and sagittal plane deformities is common During corrective surgery for scoliosis, kyphosis, and spondylolisthesis the goal is often to correct the deformity as much as possible, but restoration of balance does not necessarily involve complete correction of all deformities In some cases it may be better to partially correct the deformity in order

to maintain balance in all planes.

Alignment Restore balance in postinfective deformity The typical deformity following infection of the spine

is a localized kyphosis due to loss of vertebral body integrity While the local deformity may be significant, overall spinal balance is usually maintained However, realignment of the spine may be required for deformi- ties that threaten to compromise the spinal cord.

Fig 1.2-4 The AOSpine principles for the

treatment of deformity.

Fig 1.2-5 The AOSpine principles for the

treatment of bone infection.

Author H Michael Mayer

Stability

Stabilize pathological instability Spinal instability due to primary or secondary malignant disease may arise out of destruction of the spine by the tumor or following surgical resection

Stabilization may require internal fixation, anterior column reconstruction, and posterior fusion Anterior

or posterior or combined approaches may be needed

Long constructs offer greater stability Vertebral body reconstruction with biological implants is preferred

if the prognosis is greater than 12 months Artificial devices or PMMA may be used in palliative surgery.

Biology Use appropriate medical therapies Calcium content of bone is influenced by age, sex, diet, sunlight exposure, hormones, physical activity, and comorbidities The treatment of osteoporosis is a major public health issue The cost of disability related

to fractures is reduced by use of appropriate medical therapies.

Biology Determine likely prognosis and collaborate with oncology colleagues

Management of malignant spinal disease is usually dertaken by collaboration between surgeons, medical oncologists, radiation oncologists, and interventional radiologists The choice of optimal treatment depends

un-on the nature of the tumor and the likely prognosis

In primary tumors, surgical resection for cure usually requires clear margins For metastatic disease, surgical treatment may be for pain relief, neural decompres- sion, or debulking—and occasionally for excision of isolated metastases in suitable tumors.

Function Maintain quality of life Patients with osteoporotic spinal fractures or long- standing inflammatory spondyloarthropathies are often elderly and frail Therapeutic interventions must balance the desire for improved function against the possible loss of quality of life due to the development

of complications.

Function Preserve quality of life Preserving spinal function and minimizing disability must be considered in the context of maintaining quality of life in malignant spinal disease In all cases, the potential morbidity of surgical intervention must be balanced against the likely prognosis.

Alignment Restore balance in deformity associated with metabolic, inflammatory, and genetic disorders Deformity arising from osteoporotic collapse of the spine or inflammatory conditions such as rheumatoid arthritis and ankylosing spondylitis can result in loss

of spinal balance Corrective surgery requires an understanding of the specific features of the underlying condition to ensure enduring restoration of spinal alignment.

Alignment Restore balance in pathological deformity Collapse of the spine due to malignant disease typically results in a spinal deformity which in turn may produce neurological compression Restoration of normal align- ment, combined with decompression, often requires complex reconstructions The likely prognosis deter- mines whether realignment should be undertaken.

Fig 1.2-7 The AOSpine principles for the

treatment of metabolic, inflammatory, and

genetic disorders.

Fig 1.2-6 The AOSpine principles for the

treatment of tumor.