Minimally Invasive Spine Surgery: Surgical Techniques and Disease Management 9783030190064, 9783030190071, 3030190064

Table of contents :
Preface
Contents
Contributors
Part I: Introduction to Minimally Invasive Spine Surgery
1: History and Evolution of Minimally Invasive Spine Surgery
1.1 Introduction
1.2 Minimally Invasive Surgery in the Lumbar Spine
1.2.1 Minimally Invasive Treatment of Lumbar Intervertebral Disc Herniation
1.2.2 Tubular Retractors
1.2.3 Unilateral Approach for Bilateral Decompression
1.2.4 Posterior Lumbar Fixation and Fusion
1.2.5 Anterior and Lateral Lumbar Fusion: Indirect Neural Decompression
1.3 Minimally Invasive Surgery in the Thoracic Spine
1.4 Minimally Invasive Surgery in the Cervical Spine
1.4.1 Anterior Approaches to the Cervical Spine
1.4.2 Posterior Approaches to the Cervical Spine
1.5 Computer-Assisted Navigation in Spine Surgery
1.6 Benefits of Minimally Invasive Spine Surgery
1.7 Limitations of Minimally Invasive Spine Surgery
1.8 Conclusion
Quiz Questions
Answers
References
2: Philosophy and Biology of Minimally Invasive Spine Surgery
2.1 Philosophy of Minimally Invasive Spine Surgery
2.2 Spine Surgery: Anatomical Consideration
2.2.1 Posterior Paraspinal Muscle Anatomy
2.2.2 Multifidus Muscle
2.2.3 Erector Spinae Muscles
2.2.4 The Interspinales, Intertransversarii, and Short Rotator Muscles
2.2.5 Innervation of the Posterior Paraspinal Muscles
2.3 Biology of Iatrogenic Paraspinal Muscle Injury
2.4 Correlation of Muscle Injury with Clinical Outcomes
2.5 Potential Causes of Paraspinal Muscle Injury During Surgery
2.5.1 Dissection
2.5.2 Retraction
2.5.3 Nerve Injury
2.5.4 Thermal Injury Related to Electrocautery
2.6 Evidence for Benefits of MISS
2.6.1 Preservation of Muscle Tissue
2.6.2 Preservation of the Bone- Ligament Complex
2.7 Conclusions
Quiz Questions
Answers
References
3: Economics of Minimally Invasive Spine Surgery
3.1 Introduction
3.2 Health Economic Evaluations (HEEs)
3.2.1 The Importance of Health Economic Evaluations
3.2.2 The Language of Health Economic Analysis
3.2.3 Definitions of HEEs
3.2.4 Cost-Effectiveness (CEA) and Utility (CUA) Analyses
3.2.5 Components of A CEA
3.2.5.1 Direct Costs
3.2.5.2 Indirect Costs
3.2.6 Effectiveness
3.3 Clinician’s Approach to HEE for MIS of the Spine
3.4 Economic Comparison of MIS Versus Open Fusion
3.5 Current MIS Versus Open Lumbar Fusion Health Economic Evaluations
3.6 Current Limitations
3.7 Conclusion
Quiz Questions
Answers
References
4: Learning Curve for Minimally Invasive Spine Surgery
4.1 Introduction
4.2 History
4.3 The Learning Curve
4.4 The Learning Curve in MISS
4.5 “Bending” The Learning Curve in MISS
4.6 Conclusion
Quiz Questions
Answers
References
5: The Role of MI Spine Surgery in Global Health: A Development Critique
5.1 Introduction
5.2 Global Surgery 2030 and the Burden of Spinal Disease in the Global South
5.3 Biosocial Analysis
5.4 Global Surgery 2030 and the Effective Implementation of Assistance
5.5 Conclusions
Quiz Questions
Answers
References
Part II: Enabling Technologies for Minimally Invasive Spine Surgery
6: Microscopes and Endoscopes
6.1 Introduction
6.2 Microscope
6.3 Endoscopes
6.3.1 History
6.3.2 The Endoscope
6.3.3 The Endoscope and Spine Surgery
Quiz Questions
Answers
References
7: Intraoperative Neurophysiology Monitoring
7.1 Introduction
7.2 Anesthesia Requirements and Preparation for IONM
7.3 Introduction to IONM Modalities
7.3.1 Spontaneous or Free-Run Electromyography (EMG)
7.3.2 Triggered Electromyography (TrEMG)
7.3.3 Somatosensory-Evoked Potentials (SSEP)
7.3.4 Motor-Evoked Potentials (MEP)
7.3.5 Multimodality Monitoring
7.4 IONM and MISS
7.4.1 IONM and Percutaneous Pedicle Screw Placement
7.4.2 IONM and the Lateral Transpsoas Approach and XLIF
7.4.3 IONM in MISS Laminectomy and Transforaminal Lumbar Interbody Fusion (TLIF)
7.4.4 IONM with MISS Thoracolumbar Corpectomy and Cervical Surgeries
7.5 Surgeon-Driven, Attended, and Remotely Supervised Monitoring
Quiz Questions
Answers
References
8: Image Guidance in Minimally Invasive Spine Surgery
8.1 Introduction
8.2 Improved Accuracy of Pedicle Screw Placement
8.3 Impact on Clinical Outcomes and Surgical Efficiency
8.4 Further Applications of IG
8.5 Image Guidance Systems
8.6 Radiation Exposure
8.7 Technique for Image-Guided Pedicle Screw Insertion
Quiz Questions
Answers
References
9: Robotic-Assisted Spine Surgery
9.1 Introduction
9.2 The Robotic System
9.3 General Results of Robotic-Assisted Spine Surgery
9.3.1 Accuracy and Safety
9.3.2 Learning Curve
9.3.3 Time
9.3.4 Radiation Exposure
9.4 Spinal Deformity and Revision Surgeries
9.5 Minimal and Less Invasive Surgical Techniques
9.6 Clinical Outcome and Cost-Effectiveness
9.7 Conclusion
Quiz Questions
Answers
References
10: Fusion Biologics and Adjuvants in Minimally Invasive Spine Surgery
10.1 Introduction
10.2 Biologics
10.2.1 Autologous Graft
10.2.1.1 Autologous Bone Graft: Iliac Crest Bone Graft
10.2.1.2 Bone Marrow Aspirate
10.2.1.3 Platelet-Rich Plasma
10.2.2 Allograft
10.2.3 Demineralized Bone Matrix
10.2.4 Ceramics
10.2.5 Bone Morphogenetic Proteins
10.2.6 Miscellaneous: Cell Therapy and Peptides
10.3 Structural Cage Technology
10.4 Conclusion
Quiz Questions
Answers
References
11: Use of Stem Cells in Spinal Treatments
11.1 Introduction
11.2 Intervertebral Disc Anatomy
11.2.1 Nucleus Pulposus
11.2.2 Annulus Fibrosus
11.3 Intervertebral Disc Degeneration
11.3.1 Basic Science
11.3.2 Clinical Correlation
11.4 Stem Cell Therapy
11.4.1 Mesenchymal Stem Cells (MSC)
11.4.2 MSC Therapy for IVD Degeneration: Preclinical Studies
11.4.3 Clinical Trials of MSC Therapy
11.4.4 Induced Pluripotent Stem Cell Therapy in IVDD
11.4.5 Clinical Correlation for Spine Fusion
Quiz Questions
Answers
References
12: Lasers
12.1 Introduction
12.2 Basic Physics of Lasers
12.3 Laser Interaction with Tissue
12.4 History of Lasers in Spine Surgery
12.5 Types of Lasers
12.5.1 CO2
12.5.2 HOL:YAG
12.5.3 ND:YAG
12.5.4 ER:YAG
12.5.5 KTP
12.6 Current Uses in Spine Surgery
12.6.1 Percutaneous Posterolateral Laser Discectomy: Indirect Decompression
12.6.2 Laser-Assisted Spinal Endoscopy (LASE)
12.6.3 Selective Endoscopic Discectomy with Direct Visualization
12.6.4 Forainoplasty: Decompression of Foraminal Stenosis
12.6.5 Adjunct in MIS Laminectomies
12.6.6 Shrinkage of Spinal Metastasis
12.6.7 Facet Nerve Ablation
12.6.8 Revision Spine Surgery
12.7 Advantages of Lasers for MIS
12.8 Complications/Hazards of Lasers
Quiz Questions
Answers
References
13: Radiation Exposure and Avoidance in Minimally Invasive Spine Surgery
13.1 Introduction
13.2 Physics and Biological Effects of Ionizing Radiation
13.3 Radiation Exposure during Various Procedures
13.3.1 Overview
13.3.2 Tubular/Endoscopic Microdiscectomy
13.3.3 Vertebral Augmentation
13.3.4 Percutaneous Pedicle Screw Placement
13.3.5 MIS Transforaminal and Lateral Lumbar Interbody Fusions
13.4 Radiation Safety and Methods to Minimize Exposure
13.4.1 Overview
13.4.2 Imaging Considerations
Quiz Questions
Answers
References
Part III: Surgical Techniques: Minimally Invasive Decompression
14: Posterior Cervical Decompression
14.1 Introduction
14.2 Indications for Procedure
14.3 Contraindications
14.4 Technique
14.4.1 Equipment
14.4.2 Positioning
14.4.3 Docking and Exposure
14.4.4 Ipsilateral Decompression
14.4.5 Central, Bilateral, or Multilevel Decompression
14.4.6 Wound Closure and Postoperative Care
14.5 Complications and Management
14.6 Conclusion
Quiz Questions
Answers
References
15: Thoracic Decompression
15.1 Introduction
15.2 Clinical Presentation
15.3 Indications and Patient Selection
15.4 Imaging
15.5 Surgical Technique
15.6 Surgical Approaches
15.6.1 Microendoscopic Discectomy (MED) for a Paracentral Thoracic Disc Herniation
15.6.2 Microendoscopic Lateral Extracavitary Corpectomy for Thoracic Vertebral Body Disease
15.7 Pearls and Pitfalls
15.7.1 Important Points
15.7.2 Clinical/Surgical Pearls
15.7.3 Clinical/Surgical Pitfalls
15.8 Avoiding and Treating Surgical Complications
15.9 Wound Closure and Postoperative Care
Quiz Questions
Answers
References
16: Lumbar Decompression Using a Tubular Retractor System
16.1 Surgical Indications
16.2 Technique
16.2.1 Incision and Exposure
16.2.2 Ipsilateral Decompression
16.2.3 Bilateral Decompression
16.2.4 Wound Closure and Postoperative Care
16.3 Complications and Management
16.4 Conclusion
Quiz Questions
Answers
References
17: Endoscopic Decompression
17.1 Introduction
17.2 Patient Selection
17.2.1 Clinical Assessment
17.2.2 Radiographic Assessment
17.2.3 Diagnostic Injection
17.2.4 Awake Surgery
17.2.5 Indications
17.2.6 Contraindications and Limitations
17.3 Lumbar Transforaminal Decompression
17.3.1 Anesthesia Considerations
17.3.2 Patient Positioning
17.3.3 Skin Markings
17.3.4 Targeted Needle Placement
17.3.5 Instruments
17.3.6 Intra-discal Inside Out Technique
17.3.7 Extra-discal Technique
17.3.8 Foraminoplasty Techniques
17.3.9 Avoiding Complications
17.4 Lumbar Interlaminar Decompression
17.4.1 Patient Positioning
17.4.2 Anesthesia Considerations
17.4.3 Skin Markings
17.4.4 Needle Placement
17.4.5 Discectomy
17.4.6 Laminectomy
17.5 Posterior Cervical Decompression
17.5.1 Patient Positioning
17.5.2 Anesthesia Considerations
17.5.3 Skin Markings
17.5.4 Needle Placement
17.5.5 Discectomy/Foraminotomy
17.6 Training Considerations
Quiz Questions
Answers
References
18: Interspinous and Interlaminar Devices for Decompression
18.1 Introduction
18.2 Indications for Procedure
18.3 Contraindications
18.4 Operative Technique: Insertion of Coflex® Interlaminar Implant
18.4.1 Positioning
18.4.2 Exposure and Decompression
18.4.3 Implant Insertion
18.4.4 Wound Closure and Post-Operative Care
18.5 Complications and Management
18.6 Discussion
18.7 Outcome Studies
18.7.1 Coflex® Interlaminar Stabilization Device
18.7.2 Superion® Interspinous Device
18.8 Conclusion
Quiz Questions
Answers
References
19: Minimally Invasive Posterior Cervical Fixation
19.1 Evolution of the Minimally Invasive Technique
19.2 MIS Posterior Cervical Fixation Surgical Technique
19.2.1 Anatomic Considerations
19.2.2 Patient Preparation, Imaging, Neuromonitoring
19.2.3 Tubular Dilation, Exposure, Visualization
19.2.4 Lateral Mass Instrumentation
19.2.5 Cervical Pedicle Screw Instrumentation
19.2.6 Transfacet Instrumentation
19.2.7 Closure
19.3 Clinical Experience
Quiz Questions
Answers
References
20: Percutaneous Pedicle Screws
20.1 Indications and Contraindications
20.2 Surgical Technique
20.2.1 Percutaneous Pedicle Screw Fixation Using 2-D Fluoroscopy
20.2.2 Percutaneous Pedicle Screw Fixation Using Intraoperative 3-D Imaging Navigation
20.3 Avoiding and Treating Complications
20.4 Postoperative Care
Quiz Questions
Answers
References
21: Minimally Invasive Facet Screw Fixation
21.1 Introduction
21.2 Indications
21.3 Contraindications
21.4 Patient Positioning
21.5 Surgical Technique
21.5.1 Mini-Open Translaminar Facet Screw Fixation
21.5.2 Percutaneous Translaminar Facet Screw Fixation
21.5.3 Percutaneous Transfacet Screw Fixation
21.6 Postoperative Care
21.7 Potential Complications
21.8 Clinical Studies
21.9 Summary
Quiz Questions
Answers
References
22: Minimally Invasive Transforaminal Lumbar Interbody Fusion
22.1 Introduction
22.2 Biomechanical Goals
22.3 Surgical Indications
22.4 Preoperative Planning
22.4.1 Imaging
22.5 Surgical Anatomy
22.6 Surgical Technique
22.6.1 Patient Positioning
22.6.2 Approach
22.6.3 Pedicle Screw Cannulation
22.6.4 Serial Dilation
22.6.5 Laminectomy, Facetectomy, and Foraminotomy
22.6.6 Disk Space Preparation and Interbody Graft
22.6.7 Pedicle Screw Placement
22.6.8 Posterolateral Fusion
22.6.9 Wound Closure
22.6.10 Postoperative Care
22.7 Procedure Summary
22.8 Pearls and Pitfalls
22.8.1 General Considerations
22.9 Outcomes and Literature
Quiz Questions
Answers
References
23: Minimally Invasive Midline Pars-Cortical Screw Techniques
23.1 Introduction
23.2 Screw Biomechanics
23.3 Anatomy
23.4 Insertion Technique
23.5 Biomechanical Analysis
23.6 Clinical Considerations
23.7 Conclusion
Quiz Questions
Answers
References
24: Minimally Invasive Spinous Process Fixation and Fusion
24.1 Introduction
24.2 Background
24.2.1 Interspinous Fixation Devices Versus Interspinous Spacers
24.3 Indications
24.4 Biomechanical Data
24.5 Surgical Technique
24.5.1 Surgical Technique Pearls
24.5.2 Surgical Technique Pitfalls
24.6 Clinical Outcomes
24.7 Complications
24.8 Conclusions
Quiz Questions
Answers
References
25: Mini-open Anterior Lumbar Interbody Fusion
25.1 Introduction
25.2 Indications
25.3 Contraindications
25.4 Clinical and Radiographic Evaluation
25.5 Relevant Anatomy
25.6 Avoiding and Treating Complications
25.7 Surgical Technique
25.7.1 L5–S1 Exposure
25.7.2 Exposure Above L5
25.8 Postoperative Care
25.9 Outcomes
25.10 Conclusion
25.11 Surgical Technique Review
25.11.1 L5–S1 Exposure
25.11.2 Exposure Above L5
Quiz Questions
Answers
References
26: Minimally Disruptive Lateral Transpsoas Approach for Thoracolumbar Anterior Interbody Fusion
26.1 Introduction
26.1.1 Background
26.1.2 Mini-open Lateral Transpsoas Approach
26.1.3 Surgical Indications and Contraindications
26.2 Surgical Procedure
26.2.1 Anatomical Considerations
26.2.2 Preoperative Planning
26.2.3 Preoperative Treatment
26.2.4 Considerations
26.2.5 Required Equipment Specific to the Lateral Trans Psoas Fusion Procedure
26.2.6 Operating Room Setup and Patient Positioning
26.2.7 Anatomic and Level Identification
26.2.8 Retroperitoneal Access
26.2.9 Transpsoas Approach
26.2.10 Disc Space Preparation
26.2.11 Implantation
26.2.12 Closure
26.2.13 Supplemental Internal Fixation
26.2.14 Postoperative Management
26.3 Point-by-Point Summary of the Lateral Transpsoas Technique
26.4 Pearls and Pitfalls
26.4.1 Positioning
26.4.2 The Lateral Retroperitoneal Exposure
26.4.3 Transpsoas Approach
26.4.4 High Iliac Crest at L4–L5
26.4.5 Avoidance of Subsidence
26.4.6 Avoidance of Nonunion
26.4.7 Avoidance of Nerve Injury
26.5 Technique Modifications
26.5.1 Literature Results and Controversies
26.6 Future Directions
26.6.1 Oblique Anterior to the Psoas Approach Corridor
26.6.2 Anterior Column Realignment
26.6.3 Expandable and Alternative Implant Designs
26.6.4 Advanced Neurodiagnostics
26.6.5 Global Health Impact
26.7 Conclusion
Quiz Questions
Answers
References
27: Anterior Column Reconstruction for Sagittal Plane Deformity Correction
27.1 Introduction
27.2 Relevant Anatomy
27.3 Surgical Technique
27.4 Indications, Contraindications, Pearls, and Pitfalls
27.5 Biomechanics
27.6 Review of Literature
Quiz Questions
Answers
References
28: Thoracoscopic Fusion
28.1 Introduction
28.2 Indications and Contraindications
28.3 Instruments and Implants
28.4 Surgical Procedure
28.4.1 Anesthesia
28.4.2 Patient Positioning
28.4.3 Portal Positioning
28.4.4 Spinal Exposure
28.4.5 Fusion Techniques
28.4.5.1 Discectomy and Fusion
28.4.5.2 Corpectomy and Fusion
28.5 Complications
28.6 Postoperative Care
28.7 Conclusion
Quiz Questions
Answers
References
29: Pre-psoas Approaches for Thoracolumbar Interbody Fusion
29.1 Background
29.2 Anatomy
29.3 Surgical Technique
29.4 Results
29.5 Summary
29.6 Pearls and Pitfalls
Quiz Questions
Answers
References
30: Endoscopic Spinal Fusion
30.1 Introduction
30.2 Endoscopic Lumbar Fusion
30.2.1 Relevant Anatomy
30.2.2 Endoscopic Minimally Invasive Transforaminal Lumbar Interbody Fusion
30.2.2.1 Indications and Exclusions
30.2.2.2 Anesthetic and Surgical Technique
30.2.2.3 Results
30.2.3 Anterior and Lateral Approaches to the Lumbar Spine
30.2.3.1 Gas Laparoscopy for ALIF
30.2.3.2 Balloon-Assisted Endoscopic Retroperitoneal Gasless (BERG) Approach
30.2.3.3 Endoscopic Lateral Transpsoas Lumbar Fusion
30.3 Endoscopic Cervical Fusion
30.3.1 Indications
30.3.2 Surgical Technique
30.3.3 Results
Quiz Questions
Answers
References
31: Navigated Spinal Fusion
31.1 Introduction
31.2 Historical Perspective
31.3 Principles of Image-Guided Spinal Navigation
31.3.1 Image Acquisition
31.3.2 Registration System
31.3.2.1 Point-Matching Registration Technique
31.3.2.2 Surface-Matching Registration Technique
31.3.2.3 Automated Registration
31.3.3 Tracking System
31.3.3.1 Optical Tracking (OT)
31.3.3.2 Electromagnetic (EM) Registration Systems
31.4 Types of Navigational Systems
31.4.1 Preoperative (CT)-Based Navigation/Computer-Based Tomography
31.4.2 Intraoperative Image-Based Navigation
31.4.2.1 2D Navigation: Fluoroscopy Based
31.4.2.2 3D Navigation: Fluoroscopy Based
31.4.2.3 Intraoperative CT (iCT) Scan Navigation
31.4.2.4 Robotic Navigation
31.5 Implementing Navigation in Minimally Invasive Spine Surgery
31.5.1 Tips and Pearls for a Successful Introduction to Computer-Assisted Surgery in Minimally Invasive Surgery
31.5.2 Surgical Workflow Pearls
31.5.2.1 Operating Room Setup
31.5.2.2 Generic Setup of the iCT NAV for Total Navigation
31.5.2.3 Generic Workflow for Lumbar/Lower Thoracic Spine Surgery with Pedicle Screw Instrumentation
31.5.2.4 Generic Workflow for Localization of Spinal Pathology
31.6 Examples of Clinical Applications
31.6.1 Cervical
31.6.2 Thoracic
31.6.3 Lumbar
31.7 Indications, Pitfalls, and Controversies
31.7.1 Pitfalls
31.7.2 Controversies/Navigation Pros and Cons
Quiz Questions
Answers
References
32: Cervical Herniated Nucleus Pulposus and Stenosis
32.1 Introduction
32.2 Anterior-Based Approaches
32.2.1 Herniations
32.2.1.1 Microsurgical Anterior Foraminotomy
Indications
Limitations
Approach
32.2.1.2 Foraminotomy
Complications
32.2.1.3 Unilateral Single or Multilevel Microsurgical Anterior Foraminotomy Approach for Cervical Spondylotic Myelopathy
Indications
Outcomes
32.2.1.4 Percutaneous Nucleoplasty
Indications
Outcomes
Outcomes and Complications
32.2.2 Anterior Endoscopic Cervical Discectomy and Fusion (AECD)
32.2.2.1 Percutaneous Endoscopic Cervical Decompression (PECD)
32.2.2.2 Anterior Endoscopic Cervical Discectomy and Fusion (AECD) Indications
32.2.2.3 Percutaneous Endoscopic Cervical Decompression (PECD) Indications
32.2.2.4 Surgical Methodology and Technique
32.2.2.5 Outcomes and Complications
32.2.3 Laser Anterior Endoscopic Cervical Fusion
32.2.3.1 Surgical Technique
32.2.3.2 Outcomes and Complications
32.3 Posterior-Based Approaches
32.3.1 Herniation
32.3.1.1 Microscopic and Endoscopic Laminoforaminotomy
32.3.1.2 Microscopic Tubular-Assisted Posterior Laminoforaminotomy
Indications: Foraminal Compression of the Nerve Root
Endoscopic Laminoforaminotomy Surgical Technique
32.3.1.3 Outcomes
Microscopic Tubular-Assisted Posterior Laminoforaminotomy (MTPL)
Endoscopic Laminoforaminotomy Versus ACDF
Endoscopic Laminoforaminotomy Versus Open Laminoforaminotomy
32.3.1.4 Posterior Cervical Transfacet Fusion
Indications
32.3.1.5 Percutaneous Cervical Transfacet Screws
Indications
Limitations
Outcomes, Complications, and Pearls
32.4 Conclusion
Quiz Questions
Answers
References
33: Thoracic Herniated Nucleus Pulposus
33.1 Clinical Presentation of Thoracic Disc Herniations
33.2 Physical Examination
33.3 Diagnostic Imaging
33.4 Nonoperative Treatment
33.5 Surgical Decision-Making
33.6 Historical Treatment Plans and Open Procedures
33.7 Minimally Invasive Approaches, Outcomes, and Complications
33.7.1 Posterolateral
33.7.2 Lateral
33.7.3 Anterolateral
33.7.4 Percutaneous Laser Decompression
33.8 Conclusion
Quiz Questions
Answers
References
34: Lumbar Herniated Nucleus Pulposus
34.1 Introduction
34.2 Pathophysiology
34.3 Classification
34.4 Diagnosis and Clinical Exam
34.5 Imaging
34.6 Nonoperative Management
34.7 Operative Management
34.8 Minimally Invasive Techniques
34.9 Conclusion
Quiz Questions
Answers
References
35: Lumbar Spinal Stenosis
35.1 Introduction
35.2 Indications
35.3 Outcomes
35.4 Outcomes in Cases of Spinal Instability
35.5 Complications
35.5.1 Interspinous Process Device Unique Complications
35.5.2 Wound Problems
35.5.3 Excessive Bleeding
35.5.4 Recurrence
35.5.5 Aborting Miss
35.5.6 Iatrogenic Instability
35.5.7 Neurologic Deficits
35.5.8 Dural Tear
35.6 Conclusion
Quiz Questions
Answers
References
36: Lumbar Spondylolisthesis
36.1 Introduction
36.1.1 Advantages of MIS Approach
36.1.2 Disadvantages of MIS/Minimal Access Surgical Technique (MAST)
36.2 Indications and Contraindications
36.2.1 Contraindications to MIS-TLIF
36.2.2 Contraindications to XLIF
36.3 Outcomes
36.4 Technique: Transforaminal Lumbar Interbody Fusion
36.4.1 Positioning and Approach
36.4.2 Decompression and Pedicle Screw Implantation
36.4.3 Technical Pearls
36.5 Technique: Extreme Lateral Interbody Fusion
36.5.1 Positioning and Approach
36.5.2 Incision and Insertion of Dilator
36.5.3 Discectomy and Cage Placement
36.5.4 Technical Pearls
36.6 Selection of Operative Approach
Quiz Questions
Answers
References
37: Adolescent Scoliosis
37.1 Introduction
37.2 Fusion Procedures
37.2.1 Posterior
37.2.1.1 Authors’ Preferred Technique
37.2.1.2 Case Example
37.2.2 Anterior
37.2.2.1 Anterior Release
37.2.2.2 Anterior Instrumentation and Fusion
37.3 Fusion-Less Treatment of Scoliosis
37.3.1 Growth Modulation
37.3.2 Vertebral Body Stapling
37.3.2.1 Surgical Technique
37.3.2.2 Postoperative Protocol
37.3.2.3 Results
37.3.2.4 Case Example
37.3.3 Vertebral Body Tethering
37.3.3.1 Technique
37.3.3.2 Postoperative Protocol
37.3.3.3 Results
37.3.3.4 Case Example
37.4 Chapter Summary
Quiz Questions
Answers
References
38: Adult Scoliosis
38.1 Introduction
38.2 Epidemiology
38.3 Classification
38.4 Clinical Presentation and Evaluation
38.5 Radiographic Evaluation
38.6 Nonoperative Care
38.7 Operative Care
38.7.1 Preoperative Planning
38.7.2 Surgical Considerations
38.7.3 Anterior Approaches
38.7.4 Lateral Transpsoas Lumbar Interbody Fusion
38.7.5 Posterior Approaches
38.7.6 Summary and Selection of Surgical Techniques
38.8 Conclusion
Quiz Questions
Answers
References
39: Anterior Column Realignment (ACR): Minimally Invasive Surgery for the Treatment of Adult Sagittal Plane Deformity
39.1 Introduction
39.2 Normal Sagittal Alignment
39.3 The Clinical Impact of Sagittal Malalignment
39.4 Classification
39.5 Is “Minimally Invasive Surgery (MIS)” Worth It?
39.6 Patient Selection
39.7 Minimally Invasive Surgery in Correction of Sagittal Spinal Deformity
39.8 Surgical Technique: Anterior Column Realignment (ACR)
39.9 Results and Outcomes
39.10 Classification of ACR
39.11 Complications
39.12 Conclusion
Quiz Questions
Answers
References
40: Thoracolumbar Spine Trauma
40.1 Introduction
40.2 Rationale
40.3 Indications for MISS in TL Trauma
40.4 Operative Techniques
40.4.1 Percutaneous Pedicle Screw Approach
40.4.2 Thoracoscopic Approach
40.4.3 Lateral Mini-Open Approach
40.4.4 Hybrid MISS Approach
40.4.5 Lumbopelvic Fixation Technique
40.5 MISS for Damage Control
40.6 Conclusion
Quiz Questions
Answers
References
41: Minimally Invasive Surgery for Spinal Tumors
41.1 Introduction
41.2 Surgical Planning
41.3 Minimally Invasive Approaches to Spinal Tumors
41.3.1 Resection of Intradural-Extramedullary Lesion Using Posterior Midline Mini-Open Approach
41.3.2 Resection of Intramedullary Tumor Using Tubular Retractor
41.3.3 Thoracic Tumors
41.3.3.1 Treatment of Thoracic Spinal Metastases Using Video-Assisted Thoracoscopy
41.3.3.2 Treatment of Thoracic Spinal Metastases Using Mini-Open Transpedicular Corpectomy
41.3.4 Lumbar Tumors
41.3.4.1 Treatment of Lumbar Spinal Metastases Using a Mini-Open Transpedicular Approach
41.3.4.2 Treatment of Lumbar Metastases Using a Lateral Transpsoas Approach
41.3.4.3 Treatment of Metastases of the Thoracolumbar Junction Using a Direct Lateral Approach
41.3.5 Augmentation for Vertebral Metastases: Kyphoplasty and Vertebroplasty
41.3.5.1 Overview
41.3.5.2 Technique
41.3.6 Radiofrequency Ablation
41.4 Comparison of Conventional and Minimally Invasive Approaches
41.4.1 Tumors of the Spinal Cord and Meninges
41.4.2 Vertebral Metastases
41.5 Considerations for Minimally Invasive Techniques
41.6 Current and Future Developments
41.7 Conclusion
Quiz Questions
Answers
References
42: Pathologic Fractures
42.1 Introduction
42.2 Epidemiology
42.3 Human Cost
42.4 Indications for Treatment
42.5 Spinal Stabilization Considerations
42.6 Specific Techniques
42.6.1 Vertebroplasty and Kyphoplasty
42.6.2 Minimally Invasive Posterior Approach
42.6.2.1 Mini-Open Transpedicular Corpectomy
42.6.2.2 Endoscopically Assisted Posterolateral Thoracic Approach
42.6.3 Minimally Invasive Anterior Approaches
42.6.3.1 Simultaneous Thoracoscopic and Posterior Decompression and Stabilization
42.6.3.2 Endoscopic Lumbar Approach
42.6.3.3 Direct Lateral Approach
42.6.3.4 Transthoracic/Transpleural Access
42.6.3.5 Retropleural/Extracavitary Access
42.6.3.6 Retroperitoneal/Transpsoas Access
42.6.3.7 Retroperitoneal/Anterior to Psoas Access
42.7 Case Reports
42.7.1 Kyphoplasty
42.7.2 Mini-Open Posterior Approach
42.7.3 Direct Lateral Approach
42.8 Outcomes and Complications
42.8.1 Kyphoplasty and Vertebroplasty
42.8.2 Thoracoscopy
42.8.3 Mini-Open Transpedicular Corpectomy
42.8.4 Direct Lateral Corpectomy
Quiz Questions
Answers
References
43: How and When to Incorporate Minimally Invasive Surgery for Treatment of Deformity: Decision-Making
43.1 Introduction
43.2 How to Incorporate MIS Techniques in the Treatment of Deformity
43.2.1 Standalone MIS Constructs
43.2.2 Circumferential MIS Constructs
43.2.3 Hybrid Constructs
43.3 When Should MIS Techniques Be Considered in the Treatment of Deformity
43.3.1 The Minimally Invasive Spinal Deformity Surgery Algorithm
43.3.2 Profile of Patients Undergoing MIS Treatment of Deformity
43.3.3 Preoperative Radiographic Assessment of Patients Undergoing MIS Surgery
43.3.3.1 Vascular Anatomy
43.3.3.2 Bony Anatomy
43.3.3.3 Transitional Anatomy
43.3.3.4 Thoracolumbar Junction
43.3.3.5 Radiographic Indicators of Success or Failure
43.4 Outcomes and Current Limitations
43.5 Conclusion
References
44: Sacroiliac Joint Dysfunction
44.1 Introduction
44.2 Background
44.3 Anatomy and Biomechanics
44.4 Pathology
44.5 Diagnosis
44.5.1 Clinical History
44.5.2 Physical Exam
44.5.3 Imaging
44.5.4 Diagnostic Injection
44.6 Nonsurgical Treatment
44.6.1 Medication Management
44.6.2 Physical Therapy
44.6.3 Pelvic Bracing
44.6.4 SI Injections
44.6.5 Radiofrequency Ablation (RFA)
44.7 Surgical Treatment
44.8 Summary
Quiz Questions
Answers
References
45: Minimally Invasive Spine Surgery in the Elderly
45.1 Introduction
45.2 MIS Decompression
45.2.1 Cervical
45.2.2 Lumbar
45.2.3 Discectomy
45.2.4 Endoscopic Decompression
45.3 MIS Fusion
45.3.1 Lateral Lumbar Interbody Fusion
45.3.2 MIS Transforaminal Lumbar Interbody Fusion (MIS TLIF)
45.3.3 MIS Vertebral Cement Augmentation
45.3.4 Midline Lumbar Interbody Fusion (MIDLIF) with Cortical Bone Trajectory (CBT) Screw Fixation
45.4 Outcomes
45.4.1 Microendoscopic Cervical Foraminotomy
45.4.2 Minimally Invasive Lumbar Discectomy
45.4.3 MIS Versus Open TLIF
45.4.4 Lateral Lumbar Interbody Fusion
45.4.5 Midline Lumbar Fusion with Cortical Bone Trajectory Screws
Quiz Questions
Answers
References
Part IV: Surgical Techniques: Minimally Invasive Fusion
46: Clinical and Economic Advantages of Out-Patient Spine Surgery
46.1 Introduction
46.2 Clinical Advantages
46.3 Economic Advantages
46.4 Market Evolution
Quiz Questions
Answers
References
47: Clinical Outcomes of Outpatient Spine Surgery
47.1 Introduction
47.2 Complication and Infection Prevention
47.3 Outcomes, Major Complications, Hospital Transfers, and Readmissions
47.4 Patient Selection
47.5 Patient Education
47.6 Pain Management
47.7 Best Practices to Reduce Complication Risk
47.8 Conclusion
Quiz Questions
Answers
References
48: Selection of Appropriate Patients for Outpatient Spine Surgery
48.1 Introduction
48.2 Examples of Minimally Invasive Spine Surgery
48.2.1 Microlumbar Discectomy (MLD)
48.2.2 Spinal Decompressions
48.2.3 Lumbar Lateral Interbody Fusion (LLIF)
48.3 Procedural Considerations
48.4 Patient Selection Considerations
48.4.1 Outpatient Lumbar Fusion
48.5 Literature Results
48.6 Conclusion
Quiz Questions
Answers
References
49: Analgesia and Anesthesia to Enable Outpatient Spine Surgery
49.1 Introduction
49.2 Preoperative Evaluation
49.2.1 Airway
49.2.2 Obstructive Sleep Apnea
49.2.3 Obesity
49.2.4 Opioids
49.3 Anesthetic Technique
49.3.1 Light to Moderate Sedation
49.3.2 Neuraxial
49.3.3 General
49.4 Analgesia
49.4.1 Opioid Reduction
49.4.2 Gabapentinoids
49.4.3 Antispasmodics
49.4.4 Low-Affinity Opioid
49.4.5 Nonsteroidal Anti-inflammatory Drugs
49.4.6 Acetaminophen
49.4.7 Lidocaine
49.5 Postoperative Care
49.6 Special Considerations
Quiz Questions
Answers
References
50: Postoperative Care Following Outpatient Spine Surgery
50.1 Introduction
50.2 Preop Counseling/Coaching for Outpatient Spine Surgery (OPSS)
50.3 Informed Consent for Outpatient Surgery
50.4 Pain Management, Diet, Drain(s), AND Wound Care
50.5 Home Support Network
50.6 Written Instructions
50.6.1 Discharge Parameters
50.7 Post-discharge Analgesia
50.8 Post-discharge Early Mobilization
50.9 Post-discharge Wound Care
50.10 Post-discharge Rehabilitation
50.11 Safety Net
Quiz Questions
Answers
References
51: Choice of Minimally Invasive Approaches: A Review of Unique Risks and Complications
51.1 Introduction
51.2 Cervical Approach Complications
51.2.1 General Considerations for Minimally Invasive Cervical Spine Surgery
51.2.2 Complications from the Anterior Approach
51.2.2.1 Anterior Cervical Foraminotomy
51.2.2.2 Anterior Cervical Discectomy Without Fusion
51.2.2.3 Anterior Cervical Discectomy and Fusion (ACDF)
51.2.3 Complications from the Posterior Cervical Approach
51.2.3.1 Posterior Cervical Foraminotomy and Laminotomy
51.2.3.2 Posterior Cervical Arthrodesis
51.3 Thoracic Procedures
51.3.1 General Considerations for Minimally Invasive Thoracic Spine Surgery
51.3.2 Anterior Transpleural Approach
51.3.3 Anterior Retropleural Approach
51.3.4 Thoracoscopic Discectomy
51.3.5 Posterior Approach
51.4 Lumbar Approach Complications
51.4.1 Minimally Invasive Lumbar Microdiscectomy and Laminoforaminotomy
51.4.2 Minimally Invasive Posterior (PLIF) and Transforaminal (TLIF) Lumbar Interbody Fusion
51.4.3 Transpsoas Approaches: Direct, Lateral, or Extreme Lateral (DLIF, LLIF, or XLIF)
51.4.4 Oblique Lumbar/Anterior to Psoas (ATP) Interbody Fusion
51.4.5 Presacral and Axial Lumbar Interbody Fusion (AxiaLIF)
51.5 Conclusion
Quiz Questions
Answers
References
52: Minimally Invasive Spine Surgery Complications with Implant Placement and Fixation
52.1 Introduction
52.2 Learning Curve
52.3 Microdiscectomy
52.4 Microdecompression
52.5 Interspinous Spacers
52.6 Percutaneous Pedicle Screw Fixation
52.7 Lateral Lumbar Interbody Fusion
52.8 Transforaminal Lumbar Interbody Fusion
52.9 Anterior Lumbar Interbody Fusion
52.10 Oblique Lumbar Interbody Fusion
52.11 Transacral Interbody Fusion
Quiz Questions
Answers
References
53: Neural and Dural Injury in Minimally Invasive Surgery
53.1 Introduction
53.2 Dural Tears
53.3 Decompression
53.4 Discectomy
53.5 Fusion
53.6 Transforaminal Fusion and Posterior Interbody Fusion
53.7 Reduction of Complications in TLIF
53.8 Pedicle Screw Placement
53.9 Intraoperative Neuromonitoring
53.10 Anterior Approaches
53.11 Transpsoas Approaches
53.12 Anatomy/Approach
53.13 Nerve Injury with XLIF/DLIF
53.14 Reducing the Risk of Injury in XLIF/DLIF
53.15 OLIF
53.16 Summary
Quiz Questions
Answers
References
54: Pseudarthrosis
54.1 Introduction
54.2 Background
54.3 Diagnosis
54.4 Treatment
Quiz Questions
Answers
References
Index

Citation preview

Frank M. Phillips Isador H. Lieberman David W. Polly Jr. Michael Y. Wang Editors

Minimally Invasive Spine Surgery Surgical Techniques and Disease Management Second Edition

123

Minimally Invasive Spine Surgery

Frank M. Phillips  •  Isador H. Lieberman David W. Polly Jr.  •  Michael Y. Wang Editors

Minimally Invasive Spine Surgery Surgical Techniques and Disease Management Second Edition

Editors Frank M. Phillips Department of Orthopedic Surgery Rush University Medical Center Chicago, IL USA David W. Polly Jr. Department of Orthopedic Surgery University of Minnesota Minneapolis, MN USA

Isador H. Lieberman Texas Back Institute Texas Health Presbyterian Hospital Plano Scoliosis and Spine Tumor Center Plano, TX USA Michael Y. Wang Department of Neurological Surgery University of Miami/Jackson Memorial Hospital Miami, FL USA

ISBN 978-3-030-19006-4    ISBN 978-3-030-19007-1 (eBook) https://doi.org/10.1007/978-3-030-19007-1 © Springer Nature Switzerland AG 2014, 2019 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Preface

Minimally invasive procedures in medicine have developed rapidly over the past decades and in many instances have become the “standard of care.” Concomitantly, in spinal surgery, there has been a move to reduce the surgical collateral damage associated with open morbid approaches and instead perform more targeted procedures with less collateral damage to the essential structures of the spine. As enabling technologies have advanced, more conditions are becoming amenable to treatment with less invasive approaches. With the dire consequences of complications in spinal surgery, these minimally invasive procedures must be safe and reproducible, and adequate training of surgeons is critical to achieving these goals. In many instances, outstanding traditional “open” surgeons do not have the ability to easily transfer their skill set to minimally invasive approaches. Minimally invasive approaches require unique skills and the ability to assimilate tactile information as well as one-dimensional visualization of the spine (as with x-ray images) into a three-dimensional appreciation of the patient’s anatomy. Critical to advancing the field is rigorous education. This text is designed to provide surgeons of varied skill levels with a thoughtful and evidence-based approach to minimally invasive spinal surgery. Minimally Invasive Spine Surgery: Surgical Techniques and Disease Management emphasizes the principals behind the surgical approach as well as the steps required to execute successfully on the surgical plan while highlighting the evidence around these procedures by renowned experts and pioneers in the field. It is important to realize that MIS surgery need not be an all-or-none phenomenon and is rather a progressive journey of acquiring knowledge and skills. Our goal with this book is to provide a comprehensive text covering more established as well as innovative techniques of MIS surgery. This has only been possible because of the collective expertise and wisdom of the outstanding contributors to this book, many of whom have played significant roles in the development and advancement of the field. We hope this book will serve as a resource for trainees as well as experienced spine surgeons. Chicago, IL, USA

Frank M. Phillips

v

Contents

Part I Introduction to Minimally Invasive Spine Surgery 1 History and Evolution of Minimally Invasive Spine Surgery���������������������������������   3 R. Nick Hernandez, Jonathan Nakhla, Rodrigo Navarro-­Ramirez, and Roger Härtl 2 Philosophy and Biology of Minimally Invasive Spine Surgery�������������������������������  19 Pawel Glowka, Choll W. Kim, and Kris Siemionow 3 Economics of Minimally Invasive Spine Surgery�����������������������������������������������������  29 Robert A. Ravinsky and Y. Raja Rampersaud 4 Learning Curve for Minimally Invasive Spine Surgery �����������������������������������������  41 Victor P. Lo and Neel Anand 5 The Role of MI Spine Surgery in Global Health: A Development Critique���������  47 Carlyn R. Rodgers and W. B. Rodgers Part II Enabling Technologies for Minimally Invasive Spine Surgery 6 Microscopes and Endoscopes�������������������������������������������������������������������������������������  61 Harel Deutsch 7 Intraoperative Neurophysiology Monitoring�����������������������������������������������������������  69 Mihir Gupta, Sandra E. Taylor, Richard A. O’Brien, William R. Taylor, and Laura Hein 8 Image Guidance in Minimally Invasive Spine Surgery�������������������������������������������  83 Ryan B. Kochanski, Hussein Alahmadi, and John E. O’Toole 9 Robotic-Assisted Spine Surgery���������������������������������������������������������������������������������  93 Anthony E. Bozzio, Xiaobang Hu, and Isador H. Lieberman 10 Fusion Biologics and Adjuvants in Minimally Invasive Spine Surgery����������������� 101 Gurmit Singh and Wellington K. Hsu 11 Use of Stem Cells in Spinal Treatments ������������������������������������������������������������������� 117 S. Mohammed Karim, Shuanhu Zhou, and James D. Kang 12 Lasers��������������������������������������������������������������������������������������������������������������������������� 127 Christopher A. Yeung and Anthony T. Yeung 13 Radiation Exposure and Avoidance in Minimally Invasive Spine Surgery����������� 139 Bryan S. Lee, Dominic W. Pelle, Nicholas R. Arnold, and Thomas E. Mroz

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Part III Surgical Techniques: Minimally Invasive Decompression 14 Posterior Cervical Decompression���������������������������������������������������������������������������� 147 Neil M. Badlani and Frank M. Phillips 15 Thoracic Decompression ������������������������������������������������������������������������������������������� 155 Mena G. Kerolus, Mazda K. Turel, Albert P. Wong, Zachary A. Smith, and Richard G. Fessler 16 Lumbar Decompression Using a Tubular Retractor System ��������������������������������� 167 Mark A. Shapses, Arjun Balakumar, and D. Greg Anderson 17 Endoscopic Decompression ��������������������������������������������������������������������������������������� 175 James J. Yue 18 Interspinous and Interlaminar Devices for Decompression����������������������������������� 189 Saqib Hasan and Hyun Bae 19 Minimally Invasive Posterior Cervical Fixation������������������������������������������������������ 201 Larry T. Khoo, Zachary A. Smith, and Roya Gheissari 20 Percutaneous Pedicle Screws������������������������������������������������������������������������������������� 215 Jonathan N. Sembrano, Sharon C. Yson, and David W. Polly Jr. 21 Minimally Invasive Facet Screw Fixation����������������������������������������������������������������� 227 Anthony E. Bozzio, Xiaobang Hu, and Isador H. Lieberman 22 Minimally Invasive Transforaminal Lumbar Interbody Fusion ��������������������������� 235 Ankur S. Narain, Fady Y. Hijji, Miguel A. Pelton, Sreeharsa V. Nandyala, Alejandro Marquez-Lara, and Kern Singh 23 Minimally Invasive Midline Pars-Cortical Screw Techniques ������������������������������� 245 Daniel L. Cavanaugh, Kunwar (Kevin) S. Khalsa, Nitin Khanna, and Gurvinder S. Deol 24 Minimally Invasive Spinous Process Fixation and Fusion ������������������������������������� 255 Jonathan N. Sellin, G. Damian Brusko, and Michael Y. Wang 25 Mini-open Anterior Lumbar Interbody Fusion������������������������������������������������������� 263 Amir M. Abtahi, Douglas G. Orndorff, Jocelyn M. Zemach, and Jim A. Youssef 26 Minimally Disruptive Lateral Transpsoas Approach for Thoracolumbar Anterior Interbody Fusion����������������������������������������������������������������������������������������� 277 Dorcas Chomba, W. C. Rodgers III, and W. B. Rodgers 27 Anterior Column Reconstruction for Sagittal Plane Deformity Correction��������� 317 Gurpreet S. Gandhoke, Zachary J. Tempel, and Adam S. Kanter 28 Thoracoscopic Fusion������������������������������������������������������������������������������������������������� 329 Rodrigo Navarro-Ramirez, Christoph Wipplinger, Sertac Kirnaz, Eliana Kim, and Roger Härtl 29 Pre-psoas Approaches for Thoracolumbar Interbody Fusion ������������������������������� 337 James D. Lin, Jamal N. Shillingford, Joseph M. Lombardi, Richard W. Schutzer, and Ronald A. Lehman Jr. 30 Endoscopic Spinal Fusion������������������������������������������������������������������������������������������ 345 Jason Ilias Liounakos, Gregory Basil, Karthik Madhavan, and Michael Y. Wang 31 Navigated Spinal Fusion��������������������������������������������������������������������������������������������� 355 Ana Luís, Rodrigo Navarro-Ramirez, Sertac Kirnaz, Jonathan Nakhla, and Roger Härtl

Contents

Contents

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32 Cervical Herniated Nucleus Pulposus and Stenosis������������������������������������������������� 375 Pablo R. Pazmiño and Carl Lauryssen 33 Thoracic Herniated Nucleus Pulposus ��������������������������������������������������������������������� 397 Krystin A. Hidden, Safdar N. Khan, and Elizabeth M. Yu 34 Lumbar Herniated Nucleus Pulposus����������������������������������������������������������������������� 407 Philip K. Louie and Gregory D. Lopez 35 Lumbar Spinal Stenosis��������������������������������������������������������������������������������������������� 417 Kenneth C. Nwosu, Safdar N. Khan, and Thomas D. Cha 36 Lumbar Spondylolisthesis ����������������������������������������������������������������������������������������� 429 Timothy Y. Wang, Vikram Mehta, John Berry-Candelario, Isaac O. Karikari, and Robert E. Isaacs 37 Adolescent Scoliosis ��������������������������������������������������������������������������������������������������� 439 Daniel J. Miller, Todd J. Blumberg, Susan E. Nelson, Per D. Trobisch, and Patrick J. Cahill 38 Adult Scoliosis������������������������������������������������������������������������������������������������������������� 455 Teja Karukonda, Steven M. Presciutti, Isaac L. Moss, and Frank M. Phillips 39 Anterior Column Realignment (ACR): Minimally Invasive Surgery for the Treatment of Adult Sagittal Plane Deformity ��������������������������������������������� 477 Gregory M. Mundis Jr., Pooria Hosseini, Amrit Khalsa, and Behrooz A. Akbarnia 40 Thoracolumbar Spine Trauma ��������������������������������������������������������������������������������� 491 Kelley E. Banagan, Daniel L. Cavanaugh, Ian Bussey, Alysa Nash, Jael E. Camacho-Matos, M. Farooq Usmani, and Steven C. Ludwig 41 Minimally Invasive Surgery for Spinal Tumors������������������������������������������������������� 503 Zach Pennington, Camilo A. Molina, and Daniel M. Sciubba 42 Pathologic Fractures��������������������������������������������������������������������������������������������������� 531 Alexandra Carrer, William W. Schairer, Dean Chou, Murat Pekmezci, Vedat Deviren, and Sigurd H. Berven 43 How and When to Incorporate Minimally Invasive Surgery for Treatment of Deformity: Decision-Making��������������������������������������������������������������������������������� 549 Andrew C. Vivas, Jason M. Paluzzi, and Juan S. Uribe 44 Sacroiliac Joint Dysfunction ������������������������������������������������������������������������������������� 557 Vinko Zlomislic and Steven R. Garfin 45 Minimally Invasive Spine Surgery in the Elderly ��������������������������������������������������� 571 Oliver Tannous and R. Todd Allen Part IV Surgical Techniques: Minimally Invasive Fusion 46 Clinical and Economic Advantages of Out-Patient Spine Surgery ����������������������� 587 Neil M. Badlani, Joel Lehr, and Frank M. Phillips 47 Clinical Outcomes of Outpatient Spine Surgery����������������������������������������������������� 595 Richard N. W. Wohns, Laura A. Miller Dyrda, and Kenneth C. Nwosu 48 Selection of Appropriate Patients for Outpatient Spine Surgery��������������������������� 605 William D. Smith, Karishma Gupta, Maritza Kelesis, and Joseph L. Laratta 49 Analgesia and Anesthesia to Enable Outpatient Spine Surgery����������������������������� 619 Ramesh M. Singa and Asokumar Buvanendran

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50 Postoperative Care Following Outpatient Spine Surgery��������������������������������������� 629 Troy I. Mounts and Gil Tepper 51 Choice of Minimally Invasive Approaches: A Review of Unique Risks and Complications ����������������������������������������������������������������������������������������������������� 639 William P. Mosenthal, Srikanth N. Divi, Jason L. Dickherber, and Michael J. Lee 52 Minimally Invasive Spine Surgery Complications with Implant Placement and Fixation ��������������������������������������������������������������������������������������������� 653 Joseph S. Butler and Mark F. Kurd 53 Neural and Dural Injury in Minimally Invasive Surgery��������������������������������������� 665 Clifton W. Hancock, Donna D. Ohnmeiss, and Scott L. Blumenthal 54 Pseudarthrosis������������������������������������������������������������������������������������������������������������� 679 Philip K. Louie, Bryce A. Basques, Nicollette M. Pepin, and Grant D. Shifflett Index������������������������������������������������������������������������������������������������������������������������������������� 687

Contents

Contributors

Editors Frank M. Phillips, MD  Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA Isador H. Lieberman, MD, MBA, FRCSC  Texas Back Institute, Texas Health Presbyterian Hospital Plano, Scoliosis and Spine Tumor Center, Plano, TX, USA David  W.  Polly Jr., MD Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN, USA Michael Y. Wang, MD  Department of Neurological Surgery, University of Miami/Jackson Memorial Hospital, Miami, FL, USA

Authors Amir M. Abtahi, MD  Spine Colorado PC, Durango, CO, USA Behrooz  A.  Akbarnia, MD Department of Orthopedics, San Diego Spine Foundation, San Diego, CA, USA Hussein Alahmadi, MD  Department of Neurosurgery, Hartford Healthcare Medical Group, New Britain, CT, USA R.  Todd  Allen, MD, PhD Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, USA Neel  Anand, MD Department of Orthopedics/Spine, Cedars-Sinai Medical Center, Los Angeles, CA, USA D.  Greg  Anderson, MD Departments of Orthopaedic Surgery and Neurological Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, PA, USA Nicholas R. Arnold, MD  Department of Orthopaedic Surgery, Cleveland Clinic Foundation, Cleveland, OH, USA Neil M. Badlani, MD, MBA  The Orthopedic Sports Clinic, Houston, TX, USA Nobilis Health Corporation, Houston, TX, USA Hyun Bae, MD  Cedars Sinai Spine Center, Los Angeles, CA, USA Arjun Balakumar, BA  Department of Orthopedics, Thomas Jefferson University Hospital, Philadelphia, PA, USA Kelley E. Banagan, MD  Department of Orthopaedics, Spine Division, University of Maryland School of Medicine, Baltimore, MD, USA

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Gregory  Basil, MD Department of Neurological Surgery, University of Miami/Jackson Memorial Hospital, Miami, FL, USA Bryce  A.  Basques, MD Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA John Berry-Candelario, MD, MPH  Department of Neurological Surgery, Duke University Medical Center, Durham, NC, USA Sigurd  H.  Berven, MD Department of Orthopaedics and Neurosurgery, University of California San Francisco, San Francisco, CA, USA Todd  J.  Blumberg, MD  Department of Orthopaedics and Sports Medicine, University of Washington/Seattle Children’s Hospital, Seattle, WA, USA Scott L. Blumenthal, MD  Center for Disc Replacement, Texas Back Institute, Plano, TX, USA Anthony E. Bozzio, MD  Texas Back Institute, Plano, TX, USA G. Damian Brusko, BS  Department of Neurosurgery, University of Miami Miller School of Medicine, Miami, FL, USA Ian Bussey, BS  Department of Orthopaedics, Spine Division, University of Maryland School of Medicine, Baltimore, MD, USA Joseph S. Butler, PhD, FRCS  National Spinal Injuries Unit, Dublin, Ireland Mater Misericordiae University Hospital, Dublin, Ireland Mater Private Hospital, Dublin, Ireland Tallaght University Hospital, Dublin, Ireland Asokumar  Buvanendran, MD Department of Anesthesiology, Rush University Medical Center, Chicago, IL, USA Patrick  J.  Cahill, MD Division of Orthopaedic Surgery, The Children’s Hospital of Philadelphia, Philadelphia, PA, USA Jael  E.  Camacho-Matos Department of Orthopaedics, Spine Division, University of Maryland School of Medicine, Baltimore, MD, USA Alexandra Carrer, MD  Department of Orthopaedic Surgery, Lenox Hill Hospital, New York, NY, USA Daniel  L.  Cavanaugh, MD Department of Orthopaedic Surgery, University of North Carolina, Chapel Hill, NC, USA Thomas  D.  Cha, MD, MBA Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA Dorcas  Chomba, MBCHB, MMED  Department of Orthopaedic Surgery, University of Nairobi, Nairobi, Kenya Dean Chou, MD  Department of Neurosurgery and Orthopaedic Surgery, UC San Francisco, San Francisco, CA, USA Gurvinder S. Deol, MD  Wake Orthopaedics, WakeMed Health and Hospitals, Raleigh, NC, USA Harel Deutsch, MD  Department of Neurosurgery, Rush University Medical Center, Chicago, IL, USA

Contributors

Contributors

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Vedat  Deviren, MD Department of Neurosurgery and Orthopaedic Surgery, UC San Francisco, San Francisco, CA, USA Jason L. Dickherber, MD  Department of Orthopaedic Surgery and Rehabilitation, University of Chicago Medical Center, Chicago, IL, USA Srikanth N. Divi, MD  Department of Orthopaedic Surgery and Rehabilitation, University of Chicago Medical Center, Chicago, IL, USA Laura A. Miller Dyrda  Becker’s Healthcare, Chicago, IL, USA Richard G. Fessler, MD, PhD  Department of Neurosurgery, Rush University Medical Center, Chicago, IL, USA Gurpreet S. Gandhoke, MD, MCh  Saint Luke’s Hospital and Marion Bloch Neuroscience Institute, Kansas City, MO, USA Steven  R.  Garfin, MD  Department of Orthopaedic Surgery, University of California, San Diego, San Diego, CA, USA Roya  Gheissari, MS  The Spine Clinic of Los Angeles, University of Southern California Neuroscience Center at Good Samaritan Hospital, Los Angeles, CA, USA Pawel Glowka, MD  Department of Spine Disorders and Pediatric Orthopedics, University of Medical Sciences, Poizna, Wielkopolska, Poland Department of Orthopaedics, University of Illinois at Chicago, Chicago, IL, USA Karishma  Gupta, BS, MPH Western Regional Center for Brain and Spine Surgery, Las Vegas, NV, USA Mihir Gupta, MD  Department of Neurosurgery, University of California San Diego Health System, San Diego, CA, USA Clifton W. Hancock, MD  Texas Back Institute, Plano, TX, USA Roger Härtl, MD  Department of Neurosurgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY, USA Saqib Hasan, MD  Cedars Sinai Spine Center, Los Angeles, CA, USA Laura  Hein, MSc Department of Neurosurgery, University of California San Diego, San Diego, CA, USA R. Nick Hernandez, MD  Department of Neurosurgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY, USA Krystin  A.  Hidden, MD Department of Orthopaedic Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA Fady  Y.  Hijji, BS Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA Pooria Hosseini  Department of Orthopedics, San Diego Spine Foundation, San Diego, CA, USA Wellington  K.  Hsu, MD Department of Orthopaedic Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, USA Xiaobang Hu, PhD  Texas Back Institute, Texas Health Presbyterian Hospital Plano, Scoliosis and Spine Tumor Center, Plano, TX, USA Robert E. Isaacs, MD  Department of Neurological Surgery, Duke University Medical Center, Durham, NC, USA

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James D. Kang, MD  Department of Orthopaedic Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA Adam S. Kanter, MD  Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA Isaac  O.  Karikari, MD Department of Neurological Surgery, Duke University Medical Center, Durham, NC, USA S.  Mohammed  Karim, MD Department of Orthopaedic Surgery, Brigham and Women’s Hospital, Boston, MA, USA Teja  Karukonda, MD Department of Orthopaedic Surgery, University of Connecticut, Farmington, CT, USA Maritza  Kelesis, BS Western Regional Center for Brain and Spine Surgery, Las Vegas, NV, USA Mena  G.  Kerolus, MD Department of Neurosurgery, Rush University Medical Center, Chicago, IL, USA Amrit Khalsa  Department of Orthopedics, Scripps Hospital, La Jolla, CA, USA Kunwar (Kevin) S. Khalsa, MD  Spine Department, OrthoArizona, Scottsdale, AZ, USA Safdar N. Khan, MD  Division of Spine Surgery, Department of Orthopaedic Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA Nitin Khanna, MD  Orthopaedic Specialists of Northwest Indiana, Munster, IN, USA Larry  T.  Khoo, MD  The Spine Clinic of Los Angeles, University of Southern California Neuroscience Center at Good Samaritan Hospital, Los Angeles, CA, USA Choll W. Kim, MD, PhD  Minimally Invasive Spine Center of Excellence, Spine Institute of San Diego, San Diego, CA, USA Eliana  Kim, BA Department of Neurosurgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York, NY, USA Sertac Kirnaz, MD  Department of Neurological Surgery, Weill Cornell Medicine, New York, NY, USA Ryan  B.  Kochanski, MD Department of Neurosurgery, Rush University Medical Center, Chicago, IL, USA Mark F. Kurd, MD  Rothman Institute, Thomas Jefferson University, Philadelphia, PA, USA Joseph  L.  Laratta, MD Department of Orthopaedic Surgery, University of Louisville Medical Center, Louisville, KY, USA Department of Orthopaedic Surgery, Norton Leatherman Spine Center, Louisville, KY, USA Carl Lauryssen, MB ChB(UCT)  St. Davids Round Rock, Austin, TX, USA Bryan S. Lee, MD  Department of Neurosurgery, Cleveland Clinic, Cleveland, OH, USA Center for Spine Health, Cleveland Clinic, Cleveland, OH, USA Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA Michael J. Lee, MD  Department of Orthopaedic Surgery and Rehabilitation, University of Chicago Medical Center, Chicago, IL, USA Ronald A. Lehman Jr., MD  Department of Spine Surgery, The Daniel and Jane Och Spine Hospital at New York-Presbyterian/Allen, New York, NY, USA

Contributors

Contributors

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Columbia University Department of Orthopedic Surgery, Division of Spine Surgery, The Spine Hospital at New York Presbyterian/Allen, New York, NY, USA Joel Lehr, BBA, Finance  Nobilis Health Corporation, Investor Relations, Houston, TX, USA James  D.  Lin, MD,MS Department of Spine Surgery, The Daniel and Jane Och Spine Hospital at New York-Presbyterian/Allen, New York, NY, USA Jason  Ilias  Liounakos, MD Department of Neurological Surgery, University of Miami/ Jackson Memorial Hospital, Miami, FL, USA Victor P. Lo, MD, MPH  Mischer Neuroscience Associates, Houston, TX, USA Memorial Hermann Hospital, Houston, TX, USA University of Texas Health Science Center at Houston, Vivian L.  Smith Department of Neurosurgery, Houston, TX, USA Joseph M. Lombardi, MD  Department of Spine Surgery, The Daniel and Jane Och Spine Hospital at New York-Presbyterian/Allen, New York, NY, USA Gregory  D.  Lopez, MD Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA Philip K. Louie, MD  Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA Steven C. Ludwig, MD  Department of Orthopaedics, Spine Division, University of Maryland School of Medicine, Baltimore, MD, USA Ana  Luís, MD Department of Neurosurgery, Hospital Egas Moniz-Centro Hospitalar de Lisboa Ocidental, Lisbon, Portugal Karthik Madhavan, MD  Department of Neurological Surgery, University of Miami/Jackson Memorial Hospital, Miami, FL, USA Alejandro  Marquez-Lara, MD Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA Vikram Mehta, MD, MPH  Department of Neurological Surgery, Duke University Medical Center, Durham, NC, USA Daniel  J.  Miller, MD Department of Orthopaedic Surgery, Gillette Children’s Specialty Healthcare, St. Paul, MN, USA Camilo A. Molina, MD  Department of Neurosurgery, Johns Hopkins School of Medicine, Baltimore, MD, USA William  P.  Mosenthal, MD Department of Orthopaedic Surgery and Rehabilitation, University of Chicago Medical Center, Chicago, IL, USA Isaac L. Moss, MD, CM, MASc, FRCS  Department of Orthopaedic Surgery, UConn Health, Farmington, CT, USA Troy  I.  Mounts, MD, MA  Department of Orthopaedics, Miracle Mile Medical Center, Los Angeles, CA, USA Thomas E. Mroz, MD  Department of Neurosurgery, Cleveland Clinic, Cleveland, OH, USA Center for Spine Health, Cleveland Clinic, Cleveland, OH, USA Department of Orthopaedic Surgery, Cleveland Clinic Foundation, Cleveland, OH, USA Gregory M. Mundis Jr., MD  Scripps Clinic Torrey Pines, La Jolla, CA, USA Department of Orthopedics, San Diego Spine Foundation, San Diego, CA, USA Department of Orthopedics, Scripps Hospital, La Jolla, CA, USA

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Jonathan Nakhla, MD  Department of Neurosurgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY, USA Sreeharsa V. Nandyala, MD  Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA Ankur S. Narain, BA  Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA Alysa Nash, BS  Department of Orthopaedics, Spine Division, University of Maryland School of Medicine, Baltimore, MD, USA Rodrigo Navarro-Ramirez, MD, MS  Department of Neurosurgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY, USA Susan  E.  Nelson, MD, MPH  Department of Orthopaedic Surgery, Children’s Hospital of Philadelphia, Philadelphia, PA, USA Kenneth C. Nwosu, MD Department of Spine Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA Richard A. O’Brien, MD, FRCP(C), MBA  Safeop Surgical, Inc., Hunt Valley, MD, USA Donna D. Ohnmeiss, DrMed  Texas Back Institute Research Foundation, Plano, TX, USA Douglas G. Orndorff, MD  Spine Colorado PC, Durango, CO, USA John E. O’Toole, MD, MS  Department of Neurosurgery, Rush University Medical Center, Chicago, IL, USA Jason M. Paluzzi, MD  Department of Neurosurgery, University of South Florida, Tampa, FL, USA Pablo R. Pazmiño, MD  SpineCal, Santa Monica, CA, USA Murat Pekmezci, MD  Department of Orthopaedic Surgery, UC San Francisco, San Francisco, CA, USA Dominic W. Pelle, MD  Department of Neurosurgery, Cleveland Clinic, Cleveland, OH, USA Center for Spine Health, Cleveland Clinic, Cleveland, OH, USA Miguel A. Pelton, MD  Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA Zach  Pennington, BS Department of Neurosurgery, Johns Hopkins School of Medicine, Baltimore, MD, USA Nicollette M. Pepin  University of California, Irvine, San Diego, CA, USA Steven M. Presciutti, MD  Department of Orthopaedic Surgery, Emory University, Atlanta, GA, USA Y. Raja Rampersaud, MD  University Health Network, Toronto Western Hospital, University of Toronto, Department of Surgery, Division of Orthopaedics, Toronto, ON, Canada Robert A. Ravinsky, MDCM, MPH  University Health Network, Toronto Western Hospital, University of Toronto, Department of Surgery, Division of Orthopaedics, Toronto, ON, Canada Carlyn  R.  Rodgers, MSc Centre of Latin American Studies, University of Cambridge, Cambridge, UK W. B. Rodgers, MD  University of Quadra, Heriot Bay, BC, Canada

Contributors

Contributors

xvii

W.  C.  Rodgers III Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT, USA William  W.  Schairer, MD Department of Orthopaedic Surgery, UC San Francisco, San Francisco, CA, USA Daniel M. Sciubba, MD  Department of Neurosurgery, Johns Hopkins School of Medicine, Baltimore, MD, USA Richard  W.  Schutzer, MD Department of Vascular Surgery, New York-Presbyterian/ Columbia University Medical Center, New York, NY, USA Jonathan N. Sellin, MD  Department of Neurosurgery, University of Miami Miller School of Medicine, Miami, FL, USA Jonathan N. Sembrano, MD  Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN, USA Mark  A.  Shapses, BS Department of Orthopedics, Rothman Institute, Thomas Jefferson University, Philadelphia, PA, USA Grant D. Shifflett, MD  DISC Sports & Spine Center, Marina Del Rey, CA, USA Jamal N. Shillingford, MD  Department of Spine Surgery, The Daniel and Jane Och Spine Hospital at New York-Presbyterian/Allen, New York, NY, USA Kris Siemionow, MD, PhD  Department of Orthopaedics, University of Illinois at Chicago, Chicago, IL, USA Ramesh  M.  Singa, MD, MHS Department of Anesthesiology, Rush University Medical Center, Chicago, IL, USA Gurmit Singh, BS  Department of Orthopaedic Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, USA Kern  Singh, MD Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, IL, USA William D. Smith, MD  Department of Neurosurgery, University Medical Center of Southern Nevada, Las Vegas, NV, USA Western Regional Center for Brain and Spine Surgery, Las Vegas, NV, USA Zachary A. Smith, MD  Department of Neurological Surgery, Feinberg School of Medicine of Northwestern University, Chicago, IL, USA Oliver  Tannous, MD Department of Orthopaedics, Georgetown University Hospital, Washington, DC, USA Sandra E. Taylor, BS, MS  Scrips Research Institute, Scripps Health, La Jolla, CA, USA William R. Taylor, MD  Department of Neurosurgery, University of California San Diego, San Diego, CA, USA Zachary J. Tempel, MD  Mayfield Brain & Spine, Cincinnati, OH, USA Gil Tepper, MD  Department of Orthopaedics, Miracle Mile Medical Center, Los Angeles, CA, USA Per  D.  Trobisch, MD Department of Spinal Surgery, Eifelklinik St. Brigida, Simmerath, Germany Mazda  K.  Turel, MCh (Neurosurgery) Department of Neurosurgery, Rush University Medical Center, Chicago, IL, USA

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Juan  S.  Uribe, MD Department of Neurological Surgery, Barrow Neurological Institute, Phoenix, AZ, USA M.  Farooq  Usmani  Department of Orthopaedics, Spine Division, University of Maryland School of Medicine, Baltimore, MD, USA Andrew C. Vivas, MD  Department of Neurosurgery, University of South Florida, Tampa, FL, USA Timothy  Y.  Wang, MD Department of Neurological Surgery, Duke University Medical Center, Durham, NC, USA Christoph  Wipplinger, MD Department of Neurosurgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York, NY, USA Richard N. W. Wohns, MD, JD, MBA  NeoSpine, Puyallup, WA, USA Albert P. Wong, MD  Department of Neurosurgery, Cedars-Sinai Hospital, Los Angeles, CA, USA Anthony T. Yeung, MD  Department of Orthopedic Spine Surgery, Desert Institute for Spine Care, Phoenix, AZ, USA Christopher A. Yeung, MD  Department of Orthopedic Spine Surgery, Desert Institute for Spine Care, Phoenix, AZ, USA Jim A. Youssef, MD  Spine Colorado PC, Durango, CO, USA Sharon  C.  Yson, MD Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN, USA Elizabeth M. Yu, MD  Division of Spine Surgery, Department of Orthopaedic Surgery, The Ohio State University Wexner Medical Center, Columbus, OH, USA James J. Yue, MD  Department of Orthopaedic Surgery, Frank H. Netter School of Medicine, Quinnipiac University, Hamden, CT, USA Jocelyn M. Zemach  Spine Colorado PC, Durango, CO, USA Shuanhu Zhou, PhD  Department of Orthopaedic Surgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA Vinko  Zlomislic, MD Department of Orthopaedic Surgery, University of California, San Diego, San Diego, CA, USA

Contributors

Part I Introduction to Minimally Invasive Spine Surgery

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History and Evolution of Minimally Invasive Spine Surgery R. Nick Hernandez, Jonathan Nakhla, Rodrigo Navarro-­Ramirez, and Roger Härtl

Learning Objectives

• Identify the three surgical objectives that have driven the evolution of MISS • Identify the four principles that aid in the safe and successful implementation of an MISS practice • Identify the history and evolution of MISS in the treatment of lumbar herniated intervertebral disc disease • Identify the history and evolution of MISS in the treatment of lumbar spine disease • Identify the history and evolution of MISS in the treatment of thoracic spine disease • Identify the history and evolution of MISS in the treatment of cervical spine disease • Identify the history and evolution of computerassisted navigation and its importance to MISS • Identify the benefits and limitations of MISS

1.1

Introduction

Hippocrates, who performed extensive study and descriptions of the human spine, as well as detailed methods for the treatment for spinal deformity, is often credited as the father of spine surgery. He proposed the first traction procedure in 390 BC with devices now termed the “Hippocratic Ladder” and “Hippocratic Board” [1]. Just as Hippocrates

labored to better understand spinal anatomy and treatment of spinal pathology, modern spine surgeons are constantly innovating to improve and advance the field of spine surgery. With advancements in our understanding of human spinal anatomy and biomechanics, instrumentation, illumination, microscopy and endoscopy, imaging, bone graft and graft substitutes, and technology, the field of minimally invasive spine surgery (MISS) has flourished. Three surgical objectives have driven the evolution of MISS: (1) limit tissue disruption and destabilization of the spinal column to leave the smallest operative footprint possible, (2) achieve bilateral decompression via a unilateral approach, and (3) achieve indirect neural decompression. With these objectives in mind, the development of tools such as tubular retractors, endoscopes, and the operative microscope, in combination with computer-assisted navigation, has made significant changes to the contemporary spine surgeon’s arsenal of operative techniques and approaches. Decreased recovery time, postoperative pain, and hospital length of stay, in addition to smaller incisions and resultant cosmetic appeal, have led patients to seek out minimally invasive options for common spinal pathologies. Less invasive techniques that can achieve the same result as traditional approaches are desirable to the patient and the surgeon, and, as technology continues to advance, the arsenal of minimally invasive techniques, in turn, continues to grow. This chapter will discuss the history and evolution of MISS with the three aforementioned surgical objectives in mind.

R. N. Hernandez (*) ∙ J. Nakhla ∙ R. Navarro-Ramirez ∙ R. Härtl Department of Neurosurgery, Weill Cornell Brain and Spine Center, Weill Cornell Medicine, New York-Presbyterian Hospital, New York, NY, USA e-mail: [email protected] © Springer Nature Switzerland AG 2019 F. M. Phillips et al. (eds.), Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-3-030-19007-1_1

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R. N. Hernandez et al.

Key Point

Three surgical concepts have driven the evolution of MISS: (1) limit tissue disruption and destabilization, (2) achieve bilateral decompression through a unilateral approach, and (3) achieve indirect neural decompression. Adopting Minimally Invasive Spine Surgery: The Four Ts  As MISS continues to evolve, several principles, represented by the “four Ts,” have been identified that facilitate the adoption and safe and successful performance of MISS. The first is Target, which refers to appropriate patient selection and individualizing treatment for each patient so as to choose the correct surgery. While the clinical applications of MISS are ever-expanding, not all spinal surgeries are amenable to minimally invasive techniques. Surgeons continue to innovate and strive to identify new surgical procedures that lead to improved patient outcomes, but surgeons must also ensure that appropriate surgery is being performed for the specific pathology and that they are able to perform such procedures safely. The second T is Tools/Technology. The advancement of MISS has closely paralleled advancements in instrumentation and technology. MISS requires specialized instruments to perform surgery efficiently and safely. Some of the fundamental tools include tubular retractors, microscope or endoscope, curved or bayoneted instruments, and 2D or 3D navigation systems. Although all of these tools may not be necessary for every MISS procedure, the accessibility to these tools can help overcome many challenges or complications encountered intraoperatively. The third T is Technique, which is innately related to the surgeon’s operative skill and training, in addition to his or her existing MISS experience. Despite adequate training, some surgeons may still find some complex MISS techniques too challenging to safely incorporate into their practice. The final T is Teaching/Training. Because MISS is not universally performed, nor the standard of care presently, not all surgical trainees are exposed to MISS techniques during their residencies. This results in some surgeons being first exposed to MISS as attending surgeons, which, due to the learning curve, can limit the ability of surgeons to comfortably and safely perform MISS. Attending MISS courses can be immensely valuable and should be sought after for any surgeon embarking on the incorporation of MISS procedures into his or her practice. Fortunately, as MISS becomes more prominent in the field, trainees are being exposed more often to MISS during their training and now may be graduating proficient in several MISS techniques.

1.2

 inimally Invasive Surgery M in the Lumbar Spine

Advances in minimally invasive techniques in the lumbar spine have progressed more rapidly than in the thoracic and cervical spine. This is partly due to the frequency of lumbar surgeries, increased safety of lumbar procedures due to the termination of the spinal cord in the upper lumbar segments and resultant lower risk of neurologic injury when compared to cervico-thoracic procedures. Additionally, surgeons are able to retract gently on the thecal sac with less risk of neurologic injury, a technique not allowed in the thoracic and cervical regions. MISS techniques often developed first in the lumbar spine and were subsequently applied to the thoracic and cervical spine. The evolution of MISS began with treatments for lumbar intervertebral disc herniations, and we will therefore begin this chapter discussing this topic.

Key Point

The first MISS techniques were developed for the treatment of lumbar intervertebral disc herniation.

1.2.1 Minimally Invasive Treatment of Lumbar Intervertebral Disc Herniation In the early 1900s, several clinicians had identified tissue masses originating from the intervertebral discs compressing neural structures resulting in neurologic symptoms and physical exam findings [2–4]. These clinicians, however, mistakenly identified the herniated disc material as cartilaginous neoplasms arising from the disc termed “chondromata.” In extensive autopsy study, Schmorl identified posterior prolapse of the intervertebral disc beneath the posterior longitudinal ligament, but did not believe this would lead to any clinical symptoms [5]. Then, in a landmark paper published in 1934 by Mixter and Barr (Fig. 1.1), the authors concluded that herniation of the nucleus pulposis is “a not uncommon cause of symptoms” and that this disc herniation had been mistaken for a cartilaginous neoplasm. Furthermore, removal of the herniated disc resulted in improvement of symptoms [6]. These conclusions revolutionized the understanding and treatment of intervertebral disc herniations. The discectomy performed by Mixter and Barr included an intradural approach to the herniated disc. In 1938, Love described the interlaminar, extradural approach that entailed removal of ligamentum flavum with minimal bony removal [7]. Yasargil first applied the operative microscope to lumbar discectomy in 1967 and its use became popular among neurosurgeons [8]. This application of the microscope to lumbar dis-

1  History and Evolution of Minimally Invasive Spine Surgery

Fig. 1.1  The landmark paper by Mixter and Barr in 1934 that associated herniated intervertebral disc with sciatica and reported improvement in symptoms with discectomy. (With permission from Mixter and Barr [6])

cectomy has led Yasargil to be credited as the father of the modern microdiscectomy. In 1978, Williams reported his experience with lumbar microdiscectomy in 532 patients with 91% of patients achieving “satisfactory results” [9]. With Kambin’s arthroscopic, anatomic description of “Kambin’s triangle” in 1990, the microsurgical treatment of far-lateral disc herniations was advanced [10]. Kambin’s triangle was identified as a safe, posterolateral, working zone through which larger instruments could be introduced without injuring the nearby neural structures. The description of this triangle allowed microsurgery to outgrow percutaneous discectomy techniques, which were limited by the use of small instruments. The excellent clinical results of the microdiscectomy coupled with low complication rates made this procedure the gold standard treatment for herniated lumbar intervertebral disc, and the procedure to which all new procedures were and are compared.

Key Point

Mixter and Barr identified herniated lumbar intervertebral discs as a common cause of sciatica. Yasargil’s application of the microscope to lumbar discectomy led him to be credited with the creation of the modern microdiscectomy.

The first description of a percutaneous approach to the spine was reported by Pool in 1938. Examining the lumbosacral spine, Pool first performed a diagnostic technique using an otoscope; however, due to the size of the otoscope and resultant hemorrhage that obscured the view, Pool described “only a fleeting glimpse of the lumbosacral nerve roots.” He then modified the technique using a small endoscope, which he termed a “myeloscope,” to visualize the lumbosacral nerve roots and surrounding anatomy [11]. The first percutaneous spinal intervention in humans was performed by Smith in 1963 [12]. Chymopapain, a proteolytic enzyme isolated from the Carica papaya fruit in 1941 [13] that induces chemonucleolysis and polymerization of the nucleus pulposus, was injected into the intervertebral disc for the treatment of sciatica. This led to decreased water content of the disc and decreased intradiscal pressure, and subsequent disc height

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and bulge shrinkage. After its introduction by Smith in 1963, chymopapain for decades remained an accepted conservative intervention for management of intervertebral disc herniation and was approved by the Food and Drug Administration in 1982. By 1984, thousands of patients had undergone treatment with chymopapain injection [14]. Despite its widespread use, its questionable long-term efficacy and side effect profile, including epidural scarring and rare cases of anaphylaxis and transverse myelitis, led the intervention to fall out of favor [15]. In 1975, Hijikata described a percutaneous posterolateral approach to the intervertebral disc in which he used a 2.6 mm diameter cannula to fenestrate the annulus and partially resect a portion of the nucleus pulposus utilizing specialized curettes and grasping forceps. The limitation of this technique, while the procedure decreased intradiscal pressure and thus relieved irritation of the nerve root achieving 72% patient satisfaction, was the inability to resect the herniated disc fragment [16]. In 1983, Friedman introduced a direct lateral percutaneous discectomy as an alternative to chemonucleolysis (i.e., chymopapain) [17]. As the risk of vascular or bowel injury was high, the technique faltered [18]. Two years later, Onik and Maroon introduced the automated percutaneous lumbar discectomy (APLD) that employed a 2 mm blunt-tipped reciprocating suction cutter probe termed a “nucelotome” with 75% successful treatment in well-­selected patients (Fig. 1.2) [19, 20]. To overcome the lack of direct visualization with such techniques, Forst and Hausman reported the insertion of a modified rigid arthroscope into the center of the intervertebral disc space after nucleotomy to assess the extent of disc removal [21]. Using this technique, in 1986, Schreiber et al. introduced “discoscopy” whereby they combined arthroscopy with percutaneous nucleotomy. However, a success rate of 72% with a complication rate of 19% in 109 patients precluded widespread adoption of the technique [22]. As laser technology emerged in the late 1980s and early 1990s, its reach extended to the treatment of herniated lumbar discs. Using an Nd:YAG laser, Choy et  al. performed the first percutaneous laser nucleolysis in a human patient in 1986 [23]. The delivery of thermal ablation to the intervertebral disc resulted in evaporation of the water content of the nucleus pulposus resulting in reduction of intradiscal pressure, and similar to chemonucleolysis, hypothesized to cause decreased disc height and bulge. A recently published randomized clinical trial comparing traditional microdiscectomy with percutaneous laser discectomy, while no significant difference in clinical outcome was identified at 2 years, found a 2-year reoperation rate within the laser group of 52%, over two times greater than that observed in the microdiscectomy group [24]. In the late 1990s, Saal and Saal introduced intradiscal electrical thermocoagulation (IDET) for patients with discogenic low back pain. Using a similar concept as laser discectomy, heat is applied to the intervertebral disc

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Fig. 1.2  Intraoperative photograph of percutaneous nucleotome placement. (With permission from Helms et al. [110])

using a thermoresistant coil. The authors reported significant improvement in pain and physical function at 1-year and 2-year follow-up [25]. While these percutaneous techniques have shown benefit in select patients, specifically patients with contained lumbar disc herniations, the techniques have limited clinical relevance for large, free, or migrated fragments, or bony compression of the nerve root in the lateral recess or foramen. A Cochrane review published in 2007 concluded that “at present, unless or until better scientific evidence is available, automated prec discectomy, coblation therapy, and laser discectomy should be regarded as research techniques” [26]. For these reasons, microdiscectomy remained the gold standard treatment for herniated lumbar intervertebral discs. Key Point

While percutaneous techniques for the treatment of herniated intervertebral discs showed some positive effect, none achieved the same clinical outcomes as microdiscectomy, which remained the gold standard treatment.

(MED) in the lumbar spine (Fig. 1.3). The system consisted of a series of concentric, thin-walled, tubular dilators that could access the lumbar spine via a muscle-sparing, percutaneous approach. The procedure left the midline ligamentous and muscular attachments intact. Once the bony anatomy was accessed via serial tubular dilation, an endoscope was inserted into the tubular retractor and traditional discectomy was performed while the surgeons viewed the surgical field on a monitor [28]. The learning curve with MED was not insignificant, with early studies showing increased rates of incidental durotomy compared to traditional open microdiscectomy. Studies that have specifically examined the learning curve have identified a plateau at around 20–40 cases [29–31]. Nevertheless, the MED was quickly adopted by orthopedic surgeons likely due to their comfortability with arthroscopy, while neurosurgeons were slower to adopt the technique. In 2002, Kim et al. described the application of the operative microscope to the METRx-MD system (Medtronic Sofamor Danek, Inc., Memphis, TN) [32], and as neurosurgeons were familiar with the use of the operative microscope, the tubular microdiscectomy began to achieve widespread use. The adoption of the tubular discectomy, whether with the use of the endoscope or microscope, has been further bolstered by positive outcomes when compared to the gold standard open microdiscectomy. A 2016 meta-analysis examined five randomized controlled trials (RCTs) comparing only MED to open discectomy found MED to have less blood loss, shorter hospitalization, and longer operative time, with no significant differences in pre- and postoperative visual analog scale or Oswestry disability index, dural leak, or nerve root injury [33]. A separate meta-analysis of 6 RCTs compared minimally invasive discectomy with open discectomy and found no significant differences in operative time, relief of leg pain, total complication rates, or reoperation for recurrent herniation, though incidental durotomy occurred more frequently with MISS [34].

1.2.3 U  nilateral Approach for Bilateral Decompression 1.2.2 Tubular Retractors Tubular access to the lumbar disc was first reported by Faubert and Caspart in 1991 for percutaneous discectomy [27]. This concept of minimal soft tissue disruption during the approach to the spinal column, thus leaving a small operative footprint, is a key principle of MISS.  In 1997, Foley and Smith described the use of an endoscope and tubular retractors for performing microendoscopic discectomy

In concurrence with the evolution of instrumentation and techniques in MISS, surgeons also evolved the ideas of MISS in its application to the treatment of common spinal pathologies. An important development was the idea of a unilateral approach to achieve bilateral decompression for lumbar spinal stenosis. This concept was applied to the open lumbar laminectomy by Spetzger et al. in 1997 [35]. The unilateral approach for bilateral decompression (UABD) continued to evolve when, in 2002, three sepa-

1  History and Evolution of Minimally Invasive Spine Surgery Fig. 1.3  Drawing of the microendoscopic tubular retractor system introduced by Foley. (With permission from Perez-Cruet et al. [111]). (a) The first tubular dilator is used to identify the bony anatomy of the target lamina and is used to scrape tissue off of the spinous process and lamina. (b) Tubular dilators of sequentially enlarging size are passed until the target diameter dilator is reached. (c) The tubular retractor is locked in place using an arm attached to the operating table and the integrated light system is attached

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rate groups described bilateral decompression for lumbar stenosis using a unilateral tubular retractor approach [36–38]. Visualization of the ipsilateral and contralateral anatomy was achieved by combining the views afforded by the microscope, adjusting the trajectory of the tubular retractor, referred to as “wanding,” and, if necessary, tilting the operating table toward or away from the surgeon. A meta-analysis comparing minimally invasive UABD to open laminectomy found the minimally invasive group had a higher satisfaction rate, lower postoperative VAS score, less blood loss, shorter hospitalization, and lower reoperation rate but longer operative time, compared to the open laminectomy group. Additionally, dural injury and CSF leak rates were comparable [39]. Mayer and Heider later described a “slalom” technique by which multi-­level laminectomies were performed through separate, alternating cross-over approaches [40]. In our practice, we have begun to employ two microscopes to perform multi-level “sla-

lom” laminectomies, thus allowing two surgeons to operate simultaneously and decreasing operative time. Further evolving the use of UABD in the lumbar spine, it was theorized that UABD would result in less destabilization of the spinal column when compared to open laminectomy. A meta-analysis examined this concept, comparing secondary fusion rates following minimally invasive UABD or open laminectomy in patients with lumbar stenosis with low-grade spondylolisthesis. The authors reported lower reoperation and fusion rates, less slip progression, and greater patient satisfaction with minimally invasive UABD compared to open laminectomy [41]. Presently, the tubular retractor system, with UABD when necessary, is used to treat a number of thoracolumbar pathologies, including synovial cysts [42], far-lateral disc herniations [43], extradural and intradural tumors [44], and tethered cord syndrome [45], as well as fusion techniques which will be described below.

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Key Point

Tubular retractors were initially introduced for the treatment of lumber intervertebral disc herniation and were quickly thereafter applied for the treatment of a number of lumbar spine diseases. The unilateral approach for bilateral decompression was an important progression in the field of MISS.

1.2.4 Posterior Lumbar Fixation and Fusion The technique for posterior lumbar interbody fusion (PLIF) was described by Cloward in 1953 [46]. Since then, advances in imaging, instrumentation, and bone graft substitutes have facilitated the development of minimally invasive techniques for spinal fusion, allowing fusion procedures through minimal access corridors with comparable results to traditional, open fusion procedures. The first description of percutaneous instrumentation was introduced in 1982 by Magerl who reported the use of pedicle screws with long shafts connected to an external fixator (Fig. 1.4) [47]. The limitations, as may be expected, were infection, patient discomfort, and the need for hardware removal once fusion had been achieved. Building upon Magerl’s external fixation technique, in 1996 Leu and Hauser reported the results of a 3-stage fusion procedure. The first stage involved percutaneous pedicle screw fixation with an external fixator. The second stage inserted bilateral cannulae approximately 10 cm from the midline to access the intervertebral disc. A nucleotomy was then performed and the endplates were prepared after

Fig. 1.4  A photograph of the external pedicle screw fixation device introduced by Magerl. (With permission from Magerl [47])

which iliac bone autograft was inserted into the disc space. The third stage involved removal of the external fixator once fusion had been achieved [48]. In an attempt to eliminate the external hardware of Magerl’s technique, Mathews and Long used subcutaneous plates that were connected to the pedicle screw shafts under direct endoscopic visualization [49]. In 2000, Lowery and Kulkarni’s adaptation included the use of subcutaneous rods instead of plates for posterior pedicle screw fixation; however, the later removal of the hardware once fusion had been achieved was still required [50]. The use of subcutaneous longitudinal connectors was limited by patient irritation and the fact that the longer moment arms created, compared to traditional open fusions, did not result in effective biomechanical stability leading to higher rates of potential failure. The placement of subfascial rods was introduced in 2001 by Foley et  al. who described the use of removable extenders applied to the pedicle screws. These extenders allowed for the pedicle screw heads to be aligned without direct visualization, thus permitting the passage of subfascial rods percutaneously (Fig.  1.5) [51]. This system was named Sextant™ (Medtronic Inc., Minneapolis, MN). Since then, multiple other percutaneous pedicle screw systems have been invented. Percutaneous pedicle screw fixation is now used in a variety of spinal pathologies, including trauma, infection, neoplasms, and deformity [52]. Key Point

The ability to pass a subfascial rod via a minimally invasive technique was a major advancement in the percutaneous pedicle screw fixation procedure.

In the same year Foley introduced the Sextant™ system, he also described the first minimally invasive PLIF with the use of tubular retractors and percutaneous placement of pedicle screws and rods [53] and soon thereafter performed the first tubular minimally invasive TLIF (MIS-TLIF) [54]. Wong et  al., well experienced with the MIS-TLIF, reported their 4-year prospective follow-up data on minimally invasive versus open TLIF and found that MIS-TLIF had shorter operative time, less blood loss and fewer postoperative transfusions, shorter hospitalization, similar fusion rates (92.5% vs. 93.5%), similar intraoperative complications, including incidental durotomy, and similar long-term outcomes compared to open TLIF. Open TLIF also had higher rates of respiratory and urinary tract infections and deep venous thrombosis, all partially attributed to the more rapid mobilization and decreased length of stay in the MIS-TLIF group. Furthermore, open TLIF had higher rates of both superficial and deep wound infections, with associated greater rates of wound revision and irrigation and debridement [55]. A meta-­analysis comparing MIS-TLIF

1  History and Evolution of Minimally Invasive Spine Surgery

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Fig. 1.5  Intraoperative photographs showing the Sextant™ percutaneous pedicle screw fixation system introduced by Foley. (a) Intraoperative photograph depicting the pedicle screw extenders. (b)  The Sextant™

arm is attached to the screw extenders, and a subfascial rod is passed through the screw heads. (c) Upon removal of the Sextant arm, the rod is left in its final position. (With permission from Khoo et al. [112])

versus open TLIF reported 94.8% and 90.9% fusion rates and complication rates of 7.5% and 12.6%, respectively [56]. As more surgeons continue to overcome the learning curve with MISS fusion techniques, the improved complication profile and speedier postoperative recovery will likely continue to emerge in the literature, and with comparable fusion rates to open fusion procedures, the MISS approaches will continue to gain popularity.

While a direct lateral approach to the lumbar spine for percutaneous discectomy had been described in 1983 [17], in 1997, Mayer reported a direct lateral, retroperitoneal approach for interbody fusion with the patient in the lateral decubitus position [61]. This approach, years later, has been termed the oblique lateral interbody fusion or anterior to psoas approach. The extreme lateral interbody fusion (XLIF®, Nuvasive, Inc., San Diego, CA) technique was introduced in 2006. Pimenta and colleagues accessed the disc space via a lateral retroperitoneal, transpsoas approach using dilators and a modified tubular retractor placed under fluoroscopic guidance [63]. This lateral, minimally invasive approach has been widely adopted and has various names, including the transpsoas approach, direct lateral interbody fusion, and lateral lumbar interbody fusion. An important aspect of the anterior and lateral interbody fusion procedures is the concept of minimally invasive approaches for the achievement of indirect neural decompression. By increasing the disc height with the interbody cage, the neural foramen is widened, resulting in indirect nerve root decompression. This indirect decompression has been quantified in multiple studies, including Inoue et al. who examined the degree of nerve root compression via computed tomography (CT) myelogram pre- and postoperatively in patients who underwent ALIF [64] and Oliveira et al. who examined pre- and postoperative magnetic resonance imaging (MRI) in patients who underwent XLIF [65]. The approaches also avoid removal of the posterior bony elements and disruption of the posterior muscular and ligamentous attachments.

1.2.5 A  nterior and Lateral Lumbar Fusion: Indirect Neural Decompression The anterior approach to the spine for the treatment of spondylolisthesis was theorized by Carpenter in 1932 [57] and performed in 1933 by Burns [58]. Burns accessed the anterior lumbar spine via a transperitoneal approach, and after drilling a hole into the anterior L5 vertebral body, malleted a tibial autograft into L5, through the L5-S1 disc space, and into the S1 vertebral body (Fig. 1.6). Laparoscopy was first applied to anterior lumbar surgery in 1991 by Obenchain for discectomy [59] and in 1995 Zucherman et  al. reported the first use of laparoscopy for anterior lumbar interbody fusion (ALIF) via a transperitoneal approach [60]. In the later 1990s, a number of modified approaches to the anterior lumbar spine were reported including mini-open retroperitoneal and transperitoneal approaches [61]. Due to the critical anatomical structures in the region, including the iliac arteries and veins and bowel, and a steep learning curve with the laparoscopic technique, most surgeons still prefer mini-open exposures for ALIF in order to adequately visualize and protect these critical structures, and allow for quick access if injury should occur. Additionally, a meta-analysis in 2015 revealed higher complication rates with laparoscopic and transperitoneal procedures compared to mini-open retroperitoneal approaches [62].

Key Point

The anterior and lateral interbody fusion techniques employ the concept of indirect neural decompression, a key surgical principle of MISS.

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Fig. 1.6  Illustration of the ALIF procedure described by Burns (a) and a lateral x-ray demonstrating the position of the tibial autograft (b). (with permission from Burns [58])

1.3

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 inimally Invasive Surgery M in the Thoracic Spine

Traditional open approaches to the thoracic spine include anterior approaches (e.g., transsternal, anterolateral transthoracic, lateral extracavitary) and posterior or posterolateral approaches (e.g., transpedicular, costotransversectomy). These techniques carry significant morbidity due to the regional anatomy and number of critical neurovascular structures encountered during the approaches. The first thoracoscopic procedure was performed by Jacobaeus in 1910 with the use of a cystoscope [66], which pioneered videoassisted thoracoscopic surgery (VATS). Mack et al. [67] and Rosenthal et al. [68] described the first uses of thoracoscopy for treatment of spinal disease, including anterior release for deformity correction, discectomy for herniated disc, and biopsy, in the early 1990s. Nowadays, VATS has been applied for the treatment of infectious processes, biopsies, drainage, thoracic disc herniations, sympathectomies, tumor resection, and anterior releases for deformity correction [69]. In 1997, Jho reported the use of an endoscope to perform thoracic discectomy for disc herniation via a transpedicular approach [70], and the use of tubular retractors and endoscopy for treatment of thoracic spine disease was reported by Jho [71] and Perez-Cruet et al. [72] in the early 2000s. Similar to lumbar tubular access, a series of muscle dilators is used to access the bony anatomy. This technique has since been used to perform thoracic laminectomies via UABD, resection of thoracic disc herniations, and resection of intradural and extradural thoracic tumors [69]. Lateral minimal access approaches to the thoracic spine have also been reported using tubular and expandable retractors for tumor removal, trauma, corpectomy,

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and placement of expandable cages [73, 74]. Additionally, minimally invasive, percutaneous thoracic pedicle screw fixation is now widely used for a variety of pathologies, including trauma, infectious, neoplastic, and degenerative disease with acceptable rates of accuracy and safety [75, 76].

1.4

 inimally Invasive Surgery M in the Cervical Spine

1.4.1 Anterior Approaches to the Cervical Spine The anterior cervical discectomy and fusion (ACDF) was first reported by Smith and Robinson [77] and Cloward [78] in 1958. Each described discectomy followed by insertion of bone graft into the disc space without the use of anterior plating, which was later described by Orozco Delclos and Llovet Tapies in 1970 [79]. The advancement of MISS in the cervical spine has progressed at a much slower pace than that within the lumbar spine. This is partly due to the number of critical anatomic structures within the anterior neck, including the trachea, esophagus, carotid and vertebral arteries, jugular veins, and vagus and other cranial nerves, which challenge the safe application of percutaneous techniques. Additionally, the ACDF achieves the key surgical concepts of MISS: it allows access to the anterior cervical spine via the natural tissue planes between the sternocleidomastoid and infrahyoid (strap) muscles through a small incision and enjoys a low complication rate, short length of stay with good clinical outcomes. These highly favorable characteristics of the ACDF have not spawned a strong need

1  History and Evolution of Minimally Invasive Spine Surgery

to identify an alternative approach. Nevertheless, in 2008, Ruetten et al. described a minimally invasive ACDF technique utilizing an endoscope and compared, via a randomized clinical trial, to traditional open ACDF. They found no difference in clinical outcomes between the groups [80]. The endoscope had been previously applied to anterior cervical surgery by Horgan et  al. in 1999 for the percutaneous treatment of odontoid fractures in cadavers [81] and Chi examined the safety and efficacy of a percutaneous technique for odontoid screw placement in 2007, with no reported complications in 10 patients [82]. Even so, the risk of injury to the critical structures within the neck, in addition to the steep learning curve and lack of long-term data, has limited widespread use of these anterior percutaneous techniques. As an alternative to ACDF for patients with radiculopathy, in 1989 Snyder and Bernhardt [83] developed the anterior cervical fractional interspace decompression in an effort to avoid fusion and prevent the segmental collapse seen with discectomy without fusion, a technique originally described by Hankinson and Wilson in 1975 [84]. Sixty-four percent of patients experienced good or excellent results [83]. In the 1990s, Jho popularized the microsurgical anterior cervical foraminotomy for the treatment of cervical radiculopathy and spondylotic myelopathy [85, 86].

1.4.2 Posterior Approaches to the Cervical Spine With regard to minimally invasive approaches to the dorsal cervical spine, Fessler and colleagues in 2000 described a microendoscopic foraminotomy (MEF) using the MED system in cadavers [87] and later reported the clinical results in 25 patients [88]. Adamson described his initial experience with this technique in 100 patients in 2001 [89]. Both studies reported outcomes similar to open foraminotomy. A recent systematic review compared microsurgical (e.g., endoscopic, microendoscopic, microscopic) and open approaches for cervical foraminotomy and found microsurgical foraminotomy had less blood loss, shorter operative time, and shorter hospitalization with no difference in clinical outcome measures or complication rates [90]. In an attempt to limit the amount of muscle dissection required with open approaches to the posterior cervical spine, Wang et al. described a minimally invasive lateral mass fusion using tubular retractors for traumatic facet dislocation in the cervical spine in 2003. The authors later reported their experience in 25 patients with short segment (up to two levels) lateral mass fusion [91]. The limitations of this technique were the limited number of levels able to be treated and the need for a mini-open exposure to facilitate rod placement. In 2003, Wang et al. also

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explored tubular access for cervical laminoplasty in cadavers [92] and reported their clinical experience in 2008 [93]. Recent attempts at minimally invasive posterior cervical fusion have focused on the facet joint. Ahmad et al. reported a technique in 2012 for the percutaneous placement of screws that traversed the facet joint, primarily as a means of supplemental fusion following anterior fusion procedures to lower the risk of pseudoarthrosis or kyphosis [94]. In 2011, Goel and Shah reported a technique for the placement of metallic spacers into the cervical facets after facet distraction via a standard open posterior cervical approach for the treatment of spondylotic radiculopathy or myelopathy [95]. McCormack et al. adapted the technique in order to perform percutaneous placement of an intrafacet screw and expandable washer (DTRAX®, Providence Medical Technology, Inc., Walnut Creek, CA) for indirect nerve root decompression in patients with cervical radiculopathy. The authors found significant improvement in pain scores and, although not the primary goal of surgery, found a 93% fusion rate across the treated facet joints [96].

1.5

Computer-Assisted Navigation in Spine Surgery

Navigation technology has been instrumental in the evolution of modern MISS.  Within the field of neurosurgery, navigation developed first in cranial surgery where anatomic localization of unseen pathology was critically important to limit the damage to normal brain tissue [97]. In the field of spine surgery, where traditional open exposures allowed for direct visualization of the spinal anatomy, there was not a need for computer-assisted navigation. As MISS became more popular, however, the need for intraoperative navigation became imminent. The first feasible application of frameless navigation to the spine was reported in 1995 using an ultrasonic probe to register the patient’s intraoperative anatomy to a CT scan obtained preoperatively, thus providing 3-dimensional (3D) computer-assisted navigation [98]. The ultrasonic system was soon replaced by systems that used infrared light or active or passive light emitting diode arrays to track surgical instruments in space, and electromagnetic-based systems have also been developed. However, these early navigation systems required surgeons to manually register the patient’s bony anatomy to the preoperative CT, which could be cumbersome and created a potential for registration error and resultant inaccuracy [97]. The focus for development of navigation technologies shifted to systems that used intraoperative imaging data so as to avoid the manual registration process. A survey conducted in 2009 identified that the majority of spine surgeons used fluoroscopy as the primary means of image guidance for pedicle screw placement [99]. Therefore, fluoroscopy-

12 Fig. 1.7  Photographs of the “virtual fluoroscopy” navigation system. (With permission from Foley et al. [100]). (a) Photograph depicting the operating room set up of the “virtual fluoroscopy” navigation system. (b) Photograph depicting a surgeon using the navigation system. (c) Photograph of the navigation system computer screen demonstrating where the instrumentation is in space relative to the patient’s anatomy

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based navigation, or virtual fluoroscopy, was an appealing technology described in a cadaveric study [100] and subsequently multiple systems have been developed (Fig. 1.7). The limitations, however, included the variable intraoperative image quality obtained depending on the patient’s body habitus and bone quality and radiation exposure to the surgical team. Additionally, virtual fluoroscopy was only able to provide 2-dimensional navigation, importantly excluding the axial view. The introduction of intraoperative CT (iCT) systems revolutionized computer-assisted spinal navigation by allowing an automated registration process, providing high-quality imaging data, and including the axial view, not attainable with virtual fluoroscopy, for 3D views. Additionally, imaging is obtained while the patient is in the operative position versus supine as in preoperative CT, further adding to the

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accuracy. A final positive of iCT navigated systems is the decreased, or elimination of, radiation exposure to the surgical team. The advancements of spinal navigation systems have assisted tremendously in the innovation of MISS techniques. MISS often precludes the capability for surgeons to localize and orient via direct visualization of the bony anatomy. Therefore, reliable computer-assisted navigation is advantageous for the safe and efficient performance of complex MISS techniques. The ability to confirm anatomic location using navigation ensures correct level surgery and aids in avoiding complications, such as neural tissue injury. Multiple meta-analyses have emphasized the increased pedicle screw placement accuracy using computer-assisted navigation [101, 102]. A key concept of MISS, to limit soft tissue disruption in order to achieve the required exposure of the rele-

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vant surgical anatomy, is facilitated with navigation. With the use of iCT and computer-assisted navigation, the concept of “total 3D navigation surgery” has been described by the senior author of this chapter [103]. This concept allows for intraoperative 3D navigation of the spinal anatomy, completely eliminates radiation exposure to the surgical ­ staff, and thus the need for lead aprons, and eliminates the need for K-wires and cannulated instruments. As navigated systems continue to improve and evolve, so too will MISS techniques.

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may reach statistical significance, contributing to even greater healthcare-related cost savings. As more studies are reported in the literature, the economic data suggest both direct and indirect cost savings in favor of MISS [104–107]. And while there is potential for increased upfront costs due to the cost of MISS implants and equipment necessary to perform such operations, the lower downstream costs and gains in quality-­adjusted life years results in overall cost savings [105]. Key Point

Key Point

The use of intraoperative CT allowed for automatic patient registration and led to improved accuracy of navigation systems. Computer-assisted navigation has facilitated and advanced MISS techniques.

Cost-effectiveness studies have demonstrated direct and indirect cost savings in favor of MISS over open surgery.

1.7 1.6

 enefits of Minimally Invasive B Spine Surgery

 imitations of Minimally Invasive L Spine Surgery

The learning curve to acquire the skills necessary for MISS is not insignificant. This learning curve is a well-reported There are clear advantages to minimally invasive surgery phenomena that can be challenging for spine surgeons to and the field is burgeoning across all surgical specialties. overcome, and certainly acts as a deterrent to the w ­ idespread The emergence of MISS has allowed for comparable clinical use of MISS techniques [29–31, 108, 109]. The anatomical outcomes to traditional, open approaches including patient-­ views, although similar, vary when using a tubular retractor reported outcomes, fusion rates, and complication rates. The and a thorough understanding of the 3D anatomy is necesadded benefits of decreased blood loss, shorter hospital stays, sary to utilize this skill safely. The tools used to perform the decreased postoperative narcotic requirements, decreased surgery are longer and bayonetted, which requires practice. infection rates, fewer inpatient rehabilitation discharges, There is an increasing reliance on fluoroscopy and especially and decreased risk of postoperative spinal instability in non-­ image guidance for complex cases, which if not used propfusion cases reiterate the importance of MISS on the future erly can lead to wrong-level surgery or have devastating neuof spine surgery [33, 34, 40, 41, 55, 56]. Furthermore, the rological consequences. Lastly, with limited surgical views iatrogenic muscle and soft tissue injury that results from and space for manipulating instruments, the management large, open exposures is further decreased via minimally of complications, such as repairing an incidental durotomy, invasive approaches. is more challenging than with traditional, open procedures. An additional benefit of MISS is the potential healthcare-­ The use of the “four Ts,” described earlier in the chapter, can related cost savings. Studies consistently demonstrate that aid significantly in overcoming this learning curve. when compared to open procedures, MISS procedures, while no difference in operative time, have reduced blood Conclusion loss and shorter hospital stays, and multiple systematic 1.8 reviews and meta-analyses support these findings. Importantly, studies also consistently show no difference in As technology advances, new techniques will continue to patient-reported outcomes or fusion rates between MISS emerge that will allow surgeons to further reduce the degree and open surgery. Most studies also report no significant dif- of tissue injury and approach-related morbidity while achievferences in overall complication rates [33, 34, 40, 41, 55, ing similar clinical outcomes traditionally obtained with 56]. However, one meta-­analysis found a trend for fewer open surgery. While MISS techniques have a documented complications in MISS [104], and a European cost-effec- learning curve that can be a challenge to overcome, multiple tiveness model demonstrated increased cost savings due to meta-analyses and randomized clinical trials have demonfewer complications in MISS, such as surgical site infection strated equivocal or improved patient-reported outcomes and [105]. As an increasing number of surgeons perform MISS fusion rates when compared to open surgery, with decreased and become more familiar with the techniques, this trend hospital length of stay, less blood loss, and in many reports,

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decreased overall complication rates. The field of MISS has progressed at an incredible pace over the past decade. As our understanding of the human spine continues to advance concurrently with the rapid advancement in technology, ­ MISS concepts and approaches to the spine will continue to improve, leading to even safer procedures with better clinical outcomes, and allowing more spine surgeons to adopt these techniques.

Summary

• MISS has evolved based upon three surgical objectives: limiting tissue disruption in order to leave a small operative footprint, achieving bilateral decompression via a unilateral approach, and indirect neural decompression. • Four principles can facilitate the adoption and safe and successful performance of MISS, represented by the “four Ts”: Target, Tools/Technology, Technique, and Teaching/Training. • The first MISS procedures were developed for the treatment of intervertebral disc herniation. • Many percutaneous procedures were developed for the treatment of disc herniation, but none achieved the clinical outcomes seen with the gold standard microdiscectomy. • The application of tubular retractors to microdiscectomy drastically altered the direction of MISS, as tubular access was later applied for the treatment of a variety of pathologies in the cervical, thoracic, and lumbar spine. • The concept of a unilateral approach for bilateral decompression led to significant advancements in the field of MISS. • The need for improved visualization with MISS procedures prompted the application of endoscopy, laparoscopy, and operative microscopy to MISS. • MISS operations achieve similar patient-reported and fusion outcomes compared to open procedures, with less blood loss and shorter hospital stays. • As technology advances, new MISS techniques quickly follow. This is demonstrated by the evolution of computer-assisted navigation and its impact on MISS. • There is a steep learning curve with MISS techniques that limit widespread use, but with the use of the “four Ts,” surgeons can overcome this learning curve. • Economic data suggest both direct and indirect cost savings in favor of MISS over open surgery.

Quiz Questions 1. Which of the following is not a surgical objective that has driven the evolution of MISS? (a) Achieve indirect neural decompression (b) Limit tissue disruption (c) Achieve bilateral decompression via a unilateral approach (d) Excessive bony resection resulting in destabilization 2. Minimally invasive techniques to the spine were first developed for treatment of which of the following pathologies? (a) Cervical disc herniation (b) Lumbar disc herniation (c) Lumbar spondylolisthesis (d) Thoracic disc herniation 3. Which of the following comparisons of MI-TLIF versus open TLIF is accurate? (a) Better fusion rates, long-term outcome, and patient satisfaction with MI-TLIF (b) Better fusion rates, long-term outcome, and patient satisfaction with open TLIF (c) Less blood loss and shorter hospital stay with MI-TLIF (d) Less blood loss and shorter hospital stay with open TLIF 4. Automatic patient registration, which significantly improved computer-assisted navigation and facilitates MISS, is a characteristic of which of the following navigation systems? (a) Intraoperative CT (b) Preoperative MRI (c) Preoperative CT (d) Cross-table XR

Answers 1. 2. 3. 4.

d b c a

References 1. Marketos SG, Skiadas P. Hippocrates: the father of the spine surgery. Spine (Phila Pa 1976). 1999;24:1381–7. 2. Elsberg CA. Extradural spinal tumors: primary, secondary, metastatic. Surg Gynec and Obst. 1928;46:1. 3. Clymer G, Mixter WJ, Mella H. Experience with spinal cord tumors during the past ten years. Arch Neurol Psychiatr. 1921;5:213. 4. Stookey B.  Compression of the spinal cord due to ventral extradural cervical chondromas. Arch Neurol Psychiatr. 1928; 20:275.

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R. N. Hernandez et al. 65. Oliveira L, Marchi L, Coutinho E, Pimenta L.  A radiographic assessment of the ability of the extreme lateral interbody fusion procedure to indirectly decompress the neural elements. Spine (Phila Pa 1976). 2010;35(Suppl 26):S331–7. https://doi. org/10.1097/BRS.0b013e3182022db0. 66. Jacobaeus HC.  Possibility of the use of cystoscope for investigation of serious cavities. Munch Med Wochenschr. 1910;57:2090–2. 67. Mack MJ, Regan JJ, Bobechko WP, Acuff TE.  Application of thoracoscopy for diseases of the spine. Ann Thorac Surg. 1993;56:736–8. https://doi.org/10.1016/0003–4975(93)90966-L. 68. Rosenthal DJ, Rosenthal DR, Simone A. Removal of a protruded thoracic disc using microsurgical endos- copy: a new technique. Spine (Phila Pa 1976). 1994;19:1087–91. 69. Kasliwal MK, Tan LA, Fessler RG.  Minimally invasive spinal decompression and stabilization techniques II: clinical applications and results. In: Steinmetz MP, Benzel EC, editors. Benzel’s spine surgery: techniques, complication avoidance, and management. 4th ed. Philadelphia: Elsevier; 2017. p. 1474–98. 70. Jho HD. Endoscopic microscopic transpedicular thoracic discectomy. Technical note. J Neurosurg. 1997;87:125–9. https://doi. org/10.3171/jns.1997.87.1.0125. 71. Jho HD. Endoscopic transpedicular thoracic discectomy. Neurosurg Focus. 2000;9:e4. https://doi.org/10.3171/foc.2000.9.4.5. 72. Perez-Cruet MJ, Kim BS, Sandhu F, Samartzis D, Fessler RG.  Thoracic microendoscopic discectomy. J Neurosurg Spine. 2004;1:58–63. https://doi.org/10.3171/spi.2004.1.1.0058. 73. Smith WD, Dakwar E, Le TV, Christian G, Serrano S, Uribe JS. Minimally invasive surgery for traumatic spinal pathologies: a mini-open, lateral approach in the thoracic and lumbar spine. Spine (Phila Pa 1976). 2010;35(Suppl 26):S338–46. https://doi. org/10.1097/BRS.0b013e3182023113. 74. Uribe JS, Dakwar E, Le TV, Christian G, Serrano S, Smith WD.  Minimally invasive surgery treatment for thoracic spine tumor removal: a mini-open, lateral approach. Spine (Phila Pa 1976). 2010;35(Suppl 26):S347–54. https://doi.org/10.1097/ BRS.0b013e3182022d0f. 75. Holly LT, Foley KT. Three-dimensional fluoroscopy-guided percutaneous thoracolumbar pedicle screw placement. Technical note. J Neurosurg. 2003;99(Suppl 3):324–9. https://doi.org/10.3171/ spi.2003.99.3.0324. 76. Ringel F, Stoffel M, Stuer C, Meyer B.  Minimally invasive transmuscular pedicle screw fixation of the thoracic and lumbar spine. Neurosurgery. 2006;59(Suppl 2):ONS361–6. https://doi. org/10.1227/01.NEU.0000223505.07815.74. 77. Smith GW, Robinson RA. The treatment of certain cervical spine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone Joint Surg Am. 1958;40:607–24. 78. Cloward R. The anterior approach for removal of ruptured cervical disks. J Neurosurg. 1958;15:602–17. 79. Orozco Delclos R, Llovet Tapies J.  Osteosintesis en las fracturas de raquis cervical. Nota de tecnica. Rev Ortop Traumatol. 1970;14:285–8. 80. Ruetten S, Komp M, Merk H, Godolias G. Full-endoscopic anterior decompression versus conventional anterior decompression and fusion in cervical disc herniations. Int Orthop. 2009;33:1677– 82. https://doi.org/10.1007/s00264–008–0684-y. 81. Horgan MA, Hsu FP, Frank EH.  A novel endoscopic approach for anterior odontoid screw fixation: technical note. Minim Invasive Neurosurg. 1999;42:142–5. https://doi.org/10.105 5/s-2008–1053387. 82. Chi YL, Wang XY, Xu HZ, Lin Y, Huang QS, Mao FM, et  al. Management of odontoid fractures with percutaneous anterior odontoid screw fixation. Eur Spine J. 2007;16:1157–64. https:// doi.org/10.1007/s00586–007–0331–0.

1  History and Evolution of Minimally Invasive Spine Surgery 83. Snyder GM, Bernhardt M. Anterior cervical fractional interspace decompression for treatment of cervical radiculopathy. A review of the first 66 cases. Clin Orthop. 1989;246:92–9. 84. Hankinson HL, Wilson CB.  Use of operating microscope in anterior cervical discectomy without fusion. J Neurosurg. 1975;43:452–6. https://doi.org/10.3171/jns.1975.43.4.0452. 85. Jho HD. Microsurgical anterior cervical foraminotomy for radiculopathy: a new approach to cervical disc herniation. J Neurosurg. 1996;84:155–60. https://doi.org/10.3171/jns.1996.84.2.0155. 86. Jho HD. Decompression via microsurgical anterior foraminotomy for cervical spondylotic myelopathy: technical note. J Neurosurg. 1997;86:297–302. https://doi.org/10.3171/jns.1997.86.2.0297. 87. Roh SW, Kim DH, Cardoso AC, Fessler RG. Endoscopic foraminotomy using MED system in cadaveric specimens. Neurosurg Focus. 2000;4:E4. https://doi.org/10.3171/foc.1998.4.2.5. 88. Fessler RG, Khoo LT.  Minimally invasive cervical microendoscopic foraminotomy: an initial clinical experience. Neurosurgery. 2002;51(Suppl 2):S37–45. https://doi. org/10.1097/00006123–200211002–00006. 89. Adamson TE. Microendoscopic posterior cervical laminoforaminotomy for unilateral radiculopathy: results of a new technique in 100 cases. J Neurosurg. 2001;95(Suppl 1):51–7. https://doi. org/10.3171/spi.2001.95.1.0051. 90. Song Z, Zhang Z, Hao J, Shen J, Zhou N, Xu S, et al. Microsurgery or open cervical foraminotomy for cervical radiculopathy? A systematic review. Int Orthop. 2016;40:1335–43. https://doi. org/10.1007/s00264–016–3193–4. 91. Wang MY, Levi AD. Minimally invasive lateral mass screw fixation in the cervical spine: initial clinical experience with long-­ term follow-up. Neurosurgery. 2006;58:907–12. https://doi. org/10.1227/01.NEU.0000209929.38213.72. 92. Wang MY, Green BA, Coscarella E, Baskaya MK, Levi A, Guest JD.  Minimally invasive cervical expansile laminoplasty: an initial cadaveric study. Neurosurgery. 2003;52:370–3. https://doi. org/10.1227/01.NEU.0000043933.32287.EE. 93. Benglis DM, Guest JD, Wang MY. Clinical feasibility of minimally invasive cervical laminoplasty. Neurosurg Focus. 2008;25:E3. https://doi.org/10.3171/FOC/2008/25/8/E3. 94. Ahmad F, Sherman JD, Wang MY. Percutaneous trans-facet screws for supplemental posterior cervical fixation: technical case report. World Neurosurg. 2012;78:716.e1–4. https://doi.org/10.1016/j. wneu.2011.12.092. 95. Goel A, Shah A.  Facetal distraction as treatment for single and multilevel cervical spondylotic radiculopathy and myelopathy: a preliminary report. Technical note. J Neurosurg Spine. 2011;14:689–96. https://doi.org/10.3171/2011.2.SPINE10601. 96. McCormack BM, Bundoc RC, Ver MR, Ignacio JM, Berven SH, Eyster EF.  Percutaneous posterior cervical fusion with the DTRAX Facet System for single-level radiculopathy: results in 60 patients. J Neurosurg Spine. 2013;18:245–54. https://doi. org/10.3171/2012.12.SPINE12477. 97. Grunert P, Darabi K, Espinosa J, Filippi R. Computer-aided navigation in neurosurgery. Neurosurg Rev. 2003;26:73–99. https:// doi.org/10.1007/s10143–003–0262–0. 98. Kalfas IH, Kormos DW, Murphy MA, McKenzie RL, Barnett GH, Bell GR, et al. Application of frameless stereotaxy to pedicle

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2

Philosophy and Biology of Minimally Invasive Spine Surgery Pawel Glowka, Choll W. Kim, and Kris Siemionow

Learning Objectives

• Key concepts of minimally invasive spine surgery (MISS) • Paraspinal muscle anatomy and innervation • Potential causes for iatrogenic muscle injury during the surgery • The biology of surgery-related iatrogenic muscle injury • Methods for soft tissue preservation • Advantages and disadvantages of MISS

Key Point

Key concepts of minimally invasive spine surgery (MISS).

2.1

 hilosophy of Minimally Invasive P Spine Surgery

The goals of MISS do not differ from those of traditional open spine surgery (OSS); however, there is the added goal of limiting soft tissue damage [1–4]. The key concepts that guide MISS approaches are as follows: (1) decrease muscle crush injuries during retraction; (2) avoid detachment of ten-

dons to the posterior bony elements, especially the multifidus attachments to the spinous process and superior articular processes; (3) maintain the integrity of the dorsolumbar fascia; (4) limit bony resection; (5) utilize known neuromuscular planes; and (6) decrease the size of the surgical corridor to coincide with the area of the surgical target site. Recent advancements in instrumentation, combined with refinement of surgical techniques, have allowed treatment of an ever broader array of spinal disorders. Many studies emphasize the clinical benefits of MISS. These early outcomes point to a reduction in infection rates [5], decreased postoperative pain [6–9], shorter length of hospital stay [6, 7], earlier rehabilitation, shorter recovery time before ambulation [6, 8], less blood loss [6– 9], decreased need of transfusion [6, 8], decreased paraspinal muscle atrophy [9], and improvement in spine extension strength [5, 9–11]. MISS vs. open spine surgery (OSS) results in improvements in quality of life with clinical benefit ­demonstrated on both physical and mental components of health quality outcome measurement tools [12].

Key Point

Paraspinal muscle anatomy and innervation.

2.2 P. Glowka Department of Spine Disorders and Pediatric Orthopedics, University of Medical Sciences, Poizna, Wielkopolska, Poland Department of Orthopaedics, University of Illinois at Chicago, Chicago, IL, USA C. W. Kim Minimally Invasive Spine Center of Excellence, Spine Institute of San Diego, San Diego, CA, USA K. Siemionow (*) Department of Orthopaedics, University of Illinois at Chicago, Chicago, IL, USA

 pine Surgery: Anatomical S Consideration

2.2.1 Posterior Paraspinal Muscle Anatomy The posterior lumbar paraspinal muscles are part of a larger biomechanical system that includes the abdominal muscles and their fibrous attachment to the spine through the lumbosacral fascia. This network of muscles is responsible for generating movements of the spine while maintaining its stability (Fig.  2.1). In addition to maintaining spinal pos-

© Springer Nature Switzerland AG 2019 F. M. Phillips et al. (eds.), Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-3-030-19007-1_2

19

20

Fig. 2.1  The posterior lumbar paraspinal muscles. (IT, intertransversarii; QL, quadratus lumborum; M, multifidus; IL, iliocostalis lumborum; LO, longissimus), PSOAS muscle

ture in its neutral position, the paraspinal muscles guard the spine from excessive bending that would otherwise endanger the integrity of the intervertebral discs and ligaments [13]. Panjabi et al. have proposed that the paraspinal muscles apply minimal resistance inside the neutral zone (NZ), but increase their stiffness exponentially once the range of motion falls outside this NZ [14–16]. This dynamic stabilizing system is controlled by an interconnected chain of mechanoreceptors imbedded in the muscle fascicles, the disc annulus, and the spinal ligaments [17]. Functional EMG studies reveal that spinal stability is achieved by the simultaneous contraction of several agonistic and antagonistic muscles [13]. Architectural studies suggest that the individual paraspinal muscles may have different primary roles at different times as either movers or stabilizers of the spinal column [18].

2.2.2 Multifidus Muscle The posterior paraspinal muscles are composed of two muscle groups: the deep paramedian transversospinalis muscle group that includes the multifidus, interspinales, intertransversarii, and short rotators, and the more superficial and lateral erector spinae muscles that include the longissimus and iliocostalis. These muscles run along the thoracolumbar spine and attach caudally to the sacrum, the sacroiliac joint, and the iliac wing. The multifidus is the most medial of the major back muscles and is the largest muscle that spans the lumbosacral junction. It is believed to be the major posterior stabilizing muscle of the spine [13, 19]. Compared to other paraspinal muscles, the multifidus muscle has a large physiological cross-sectional area (PCSA) and short fibers. This unique architectural anatomy is designed to create large forces over relatively short dis-

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tances. Furthermore, the multifidus sarcomere length is positioned on the ascending portion of the length-tension curve. When our posture changes from standing erect to bending forward, the multifidus is able to produce more force as the spine flexes forward. This serves to protect the spine at its most vulnerable position. The multifidus is the only muscle that is attached both to the posterior elements of the L5 and S1 vertebrae and is, therefore, the sole posterior stabilizer that both originates and inserts to this segment. The morphology of the lumbar multifidus is complex [20]. Unlike the other paraspinal muscles that have specific origins and insertions, the multifidus muscle is formed by five separate bands, each having its own origin and several different insertion sites. Each band consists of several fascicles arising from the tip of the spinous process and the lateral surface of the vertebral lamina. Caudally, the different fascicles diverge to separate attachments into the mammillary processes of the caudal vertebrae two to five levels below their origin and downward through each vertebra to the sacrum. For example, fibers from the L1 band insert into the mammillary processes of the L3, L4, and L5 vertebrae, to the dorsal part of S1, and to the posterior superior iliac spine. Biomechanical analysis, based on the multifidus muscle anatomy, has shown that it produces posterior sagittal rotation of the vertebra, which opposes a counter rotation generated by the abdominal muscles. The multifidus can further increase lumbar spine stability through a “bowstring” mechanism in which the muscle, positioned posterior to the lumbar lordosis, produces compressive forces on the vertebrae interposed between its attachments [18–21].

2.2.3 Erector Spinae Muscles The erector spinae muscles are composed of the longissimus, the iliocostalis, and the spinalis in the thoracic area (Fig. 2.1) [22, 23]. In the lumbar spine, the longissimus is positioned medially and arises from the transverse and accessory processes and inserts caudally into the ventral surface of the posterior superior iliac spine. The laterally positioned iliocostalis arises from the tip of the transverse processes and the adjacent middle layer of thoracolumbar fascia and inserts into the ventral edge of the iliac crest caudally. Unilateral contraction of the lumbar erector spinae laterally flexes the vertebral column; bilateral contraction produces extension and posterior rotation of the vertebrae in the sagittal plane. In addition to their role as the major extensor muscles of the trunk, the iliocostalis and the longissimus also exert a large compressive load as well as lateral and posterior shear forces at the L4 and L5 segments. While these forces increase the stiffness and stability of the normal vertebral column, the shearing forces could also exacerbate instability and deformity in a malaligned spine [24]. In contrast to the multifidus

2  Philosophy and Biology of Minimally Invasive Spine Surgery

muscle, micro-architectural studies reveal that these muscles are designed with long muscle fascicles with relatively small PCSA. This anatomical morphology suggests that they serve to move the trunk to extension, lateral bending, and rotation. With this type of design, they are less likely to act as primary stabilizers of the vertebral column [25].

2.2.4 T  he Interspinales, Intertransversarii, and Short Rotator Muscles The interspinales, intertransversarii, and short rotator muscles are short flat muscles that lie dorsal to the intertransverse ligament (Fig. 2.1). The intertransversarii and interspinales run along the intertransverse and the interspinous ligaments of each segment. The short rotators originate from the posterior superior edge of the lower vertebra and attach to the lateral side of the upper vertebral lamina. Because of their small PCSA, they are not able to generate the forces needed for movement or stability of the spinal column. More likely, they act as proprioceptive sensors rather than force-generating structures.

2.2.5 Innervation of the Posterior Paraspinal Muscles The innervation of all of the posterior paraspinal muscles is derived from the dorsal rami. The iliocostalis is innervated by the lateral branch, while the lumbar fibers of the longissimus receive innervation from the intermediate branch. The multifidus is innervated by the medial branch of the dorsal rami (Fig. 2.2). The medial branch curves around the root of

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the superior articular process and passes between the mammillary and accessory processes to the vertebral lamina where it branches to supply the multifidus muscle, the intertransversarii and the interspinales muscles, and the zygapophyseal joints. During its extra-muscular course, the medial branch is strongly attached to the vertebral body in two locations. The first attachment is to the periosteum lateral to the zygapophyseal joints by fibers of the intertransverse ligament. The mamillo-accessory ligament provides the second attachment in the lumbar spine. This strong ligament covers the medial branch and is often ossified. These attachments to the vertebra are of clinical importance as they expose the medial branch to possible damage during a midline posterior surgical approach.

Key Point

The biology of surgery-related iatrogenic muscle injury

2.3

 iology of Iatrogenic Paraspinal B Muscle Injury

Muscle response to injury caused by surgery is well documented in both animals and humans. To assess the magnitude of muscle destruction, one can use systemic and histological parameters. Muscle cell damage leads to release into the circulation and an increase in peripheral blood concentrations of creatinine phosphokinase (CK), especially MM isoenzyme, and aldolase [1–3, 26, 27]. Significant elevations are observed on first and third day postoperatively [26]. One can

a

b L1

L1 medial branch of posterior rami

L2 L3 L4 L5

Fig. 2.2 (a, b) Multifidus innervation by the medial branch of the dorsal rami

L1 multifidus band

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observe changes in pro-inflammatory (IL-6, IL-8) and antiinflammatory (IL-10, IL-1ra) cytokine serum levels [26]. All of the mentioned substances (CK, IL-6, IL-8, IL-10, IL-1ra, CPK-MM) reach maximum serum value 1 day after surgery, and most of them (CK, IL-6, IL-1ra, CPK-MM) are followed by recovery to baseline levels 7 days after surgery [28]. Histological studies show that muscle fiber necrosis and edema occur 3 h after surgery [1]. Coagulation necrosis is associated with macrophage infiltration and occurs at 48 h [1]. During follow-up, muscle atrophy can be observed as a decrease in muscle size [10, 11, 27, 29], fat tissue infiltration [10, 27], and deposition of the connective tissue. Various authors have measured muscle atrophy assessing the muscle cross-sectional area on the MRI, CT, and USG images [10, 11, 27, 29]. Decrease of paraspinal muscle CSA occurs after surgical approach and related injury of the muscle [10, 11, 27, 29]. In some cases, muscle CSA may not decrease due to fat tissue infiltration in the muscle fascicles [30]. Waschke et al. observed significant increase of the paraspinal percentage share of fatty tissue parallel to substantial decrease of the percentage share of muscle tissue 12  months after open posterior lumbar interbody fusion and instrumentation [27]. Fat infiltration is a latestage sign of muscle degeneration [30]. Muscle CSA could even increase when the amount of fat within the muscle increased [10]. Che-Wei Hung proposed a fat infiltration ratio to assess the muscle atrophy: the ratio of fat CSA and multifidus muscle CSA.  He observed increased fat CSA/ muscle CSA in multifidus muscle in patients who had undergone posterior lumbar spine surgery [10]. In patients who had undergone spine surgery, the authors observe a substantial reduction of Neuronal nitrite oxide syntheses (n-NOS) in multifidus muscle. Zoidlet et  al. suggest that

a

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decrease of n-NOS quantity is caused by the local denervation of the medial branch of the dorsal rami of the lumbar spinal nerve [31] (Fig. 2.3).

2.4

 orrelation of Muscle Injury C with Clinical Outcomes

Paravertebral muscles are damaged during posterior lumbar spine surgery, resulting in muscles atrophy, biochemical and histological changes, electrophysiological abnormality, and decrease in trunk extension strength [9], which affects clinical outcomes. Iatrogenic paraspinal muscle or medial branch of dorsal rami [31] injury leads to loss of functional muscular support, disturbed segmental mobility, increased mechanical strain, thereby contributing to persistent back pain, and failed back surgery syndrome (FBSS) [10, 32]. Back musculature in patients who had undergone a second surgery demonstrated severe histological damage [1, 33]. Rantanen et al. concluded that persistent pathological changes in paraspinal muscles were noted in the patient with poor outcomes after the lumbar spine surgery [34]. Muscle injury, presented by the increases in creatine kinase (CK) levels postoperatively, positively correlated with clinical outcomes: VAS and ODI score [35]. Muscle cross-sectional area represents muscle potential contractile force and strength [29]. Decreased muscle CSA decreases muscle force production capacity. Multifidus fat infiltration occurs in patient who had undergone spine surgery [9, 27] and is strongly associated with lumbar back pain [30]. Waschke et al. revealed a significant correlation between EMG denervation signs with worse physical and mental outcomes assessed by the Short Form (36) Health Survey (SF-­ 36) questionnaire and visual analog scale (VAS) [27] and

b

Fig. 2.3 (a) Postoperative MRI changes associated with the traditional midline approach and (b) demonstrate preservation of muscle architecture with the paramedian approach

2  Philosophy and Biology of Minimally Invasive Spine Surgery

significant correlation between muscle atrophy measured by CT and worse clinical outcome assessed with the same scales: SF-36 and VAS for pain [27]. They also demonstrated a positive correlation between worse functional state of paraspinal muscle 1 year after surgery (reduced interference pattern in EMG examinations) and elevated serum levels for CK and myoglobin 2  days after surgery, suggesting that direct muscle trauma during open surgery partially contributes to muscle dysfunction and, finally, muscle atrophy [27]. Key Point

Potential causes for iatrogenic muscle injury during the surgery

2.5

 otential Causes of Paraspinal Muscle P Injury During Surgery

Conventional dorsomedial approach for thoracolumbar decompression and fusion traumatizes paravertebral muscles in multiple manners: dissection [9], retraction [1, 4], nerve injury [36, 37], thermal injury [38, 39], wound exposure [1, 4], operative time [1, 4], and spinal fusion [8].

2.5.1 Dissection Traditional open midline approach to posterior spinal surgery requires extensive soft tissue dissection and retraction [9]. In order to expose the operative field, the paravertebral muscles are dissected subperiosteally from the spinous processes, laminas, and, if a posterolateral fusion is planned, also the transverse processes. This compromises the nerve supply to muscles and affects the equilibrium between muscles, ligaments, and bony structures. Tissue dissection impairs muscle vascularization and leads to ischemic necrosis. Muscle insertions are compromised as are the anatomical compartments of the multifidus. Without the spinous processes, the multifidus muscles from both sides heal together by scar tissue formation which impacts their physiological function. Moreover ligament impairments destabilize the spine and increase the pathological range of motion in spinal segment, which leads to further complications [8, 40, 41].

2.5.2 Retraction Appropriate exposure of the operative field requires the use of retractors. Retractors apply direct pressure to muscle structures and cause injury. The pressure leads to isch-

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emia [33, 42] and direct muscle damage. Kawaguchi et al. reported that concentration of phosphokinase MM isoenzyme serum level is directly related to muscle retraction pressure [33]. Styf and Willen measured the intramuscular pressure in patients who underwent posterior midline lumbar spinal surgery. Before surgery the intermuscular pressure was 7.7  mmHg and varied between 61  mm and 158  mm when self-retaining retractors were applied [28]. External compression and muscle strain from retractor blades during surgery increased intermuscular pressure in paravertebral muscles to levels that impair local blood flow-induced ischemia in the muscles [28, 43]. The magnitude of muscle damage depends not only on retraction pressure but also on its duration [4, 6, 33, 44]. Several studies reported that when high pressure and prolonged retraction are applied to the muscle, neurogenic change occurs in the muscle [1, 45]. Gejo et al. emphasize the role of the duration of the pressure applied to the muscle by the retractors in causing muscle injury [44]. They observed, in patients who underwent discectomy through bilateral laminectomy, 6  months after surgery a longer relaxation T2 time of multifidus muscle in patients with long retraction time (80–125 min) compared to short-retraction-­ time group (40–80 min). Longer T2 relaxation time appears as a high signal intensity on T2-weighted images and is observed in edema, denervated muscle, inflammatory myopathies, muscle injury caused by exertion, and muscle necrosis [44]. Kawaguchi et  al. noted that patients with retractor time more than 135  min had changes in muscle structure characterized by edema, opaque fibers, and myofibrillar destruction [28, 45]. Additionally, Gejo et al. evaluated trunk extensor muscle strength. Muscle strength in the long-­retraction-­time group (80–125 min) was significantly lower than in the short-retraction-time group (40–80 min) [44]. These changes imply delayed muscle recovery time in patients with longer retraction time [44]. Moreover, the incidence of postoperative low back pain is significantly higher when retractors are applied longer [44].

2.5.3 Nerve Injury Muscle atrophy is not only a result of direct muscle injury, but it could also be caused by nerve injury and muscle denervation. The multifidus muscle is innervated by the medial branch of the dorsal rami (MBN) without intersegmental nerve supply as in the other paraspinal muscles [41]. The medial branch is particularly vulnerable to injury; it passes through the groove between the accessory process and the maxillary process, where it is fixed by the mamillo-­accessory ligament, and next courses medially and caudally across the vertebral lamina deeply to the multifidus muscle [37].

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Subperiosteal dissections in this region could transect that nerve. Dorsomedial approach to the thoracolumbar spine has a potential risk to compromise the MBN when the approach is laterally extended to the articular process by retracting the paraspinal muscles [46]. The MBN is vulnerable to direct injury during transpedicular screw insertion [10, 29] than could be transected [42]. Cawley et  al. assessed the multifidus muscle cross-­ sectional area (CSA) and electromyography in patients treated with both OSS and MISS.  Based on neurological findings, the authors demonstrated that damage to the MBN contributes to a greater portion of postoperative neuromuscular deficit [29]. Waschke et  al. found signs of denervation in EMG in patients 6 and 12 months after open posterior lumbar interbody fusion [27]: pathological spontaneous activity (PSA) with the detection of fibrillation potentials and positive sharp waves (PSW) [27]. Denervation of the paraspinal muscles after injury to the dorsal MBN is associated with the occurrence of muscle atrophy, and the finding has already been documented by experimental research [27, 47].

2.5.4 T  hermal Injury Related to Electrocautery Hemostasis during spine surgery is of paramount importance. The high temperature leads to nerve root injury [39]. Regrettably electrocautery could lead to the soft tissue thermal injury, dependently on a type of cautery in use: unipolar and bipolar. When unipolar is used, the current flow from the active electrode to the ground plate passes through all conductive tissues at the rate proportional to their conductivity, decreasing in current density with the distance from the point at which electrode is applied. Current passes throw main trunk blood vessels, the branches of which could be coagulated, through neural structures, cerebrospinal fluid, muscle, and bone. The significant amount of current and heat appear in a distance of 1–2  cm from the point of coagulation. In the bipolar forceps system, the current flows mainly between the forceps tips. If the bipolar coagulator and the unipolar coagulator are set at the same output power, all the energy will be concentrated between the bipolar forceps tips, whereas the same energy will be dispersed from the contact point to the ground in the unipolar connection [38]. Damage from the unipolar system is far greater than that from the bipolar system. In humans, coagulation with bipolar system ordinarily requires only approximately 5% of power required using the unipolar system [38]. For this reason, the use of unipolar coagulation has been restricted to exposure [38].

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Key Point

Advantages of MISS

Key Point

Methods for soft tissue preservation

2.6

Evidence for Benefits of MISS

2.6.1 Preservation of Muscle Tissue Minimally invasive spine surgery techniques strive to minimize muscle injury during surgery. By eliminating the use of self-retaining retractors, intramuscular retraction pressure is reduced and thereby leads to less crush injury. In addition, focusing the surgical corridor directly over the surgical target site allows for less muscle stripping which may otherwise disrupt muscle attachments or damage their neurovascular supply. The use of a muscle-splitting, tubular retraction system further limits injury to ipsilateral paraspinous musculature, resulting in decreased postoperative pain and preservation of healthy muscle tissue [48]. There are multiple studies that demonstrate the muscle preservation associated with MISS approaches. As mentioned before, increased creatine kinase (CK) in early postoperative period indicates the muscle cell injury and is proportional to the level of injury. Comparing MISS surgery with open spine surgery (OSS), there is decreased muscle damage correlated with significantly lower CK levels in early postoperative period in patient who underwent the MISS [26]. Decreases in tissue trauma not only have local effects but have systemic effects as well. Proinflammatory (IL6, IL-8) and anti-inflammatory (IL-10, IL-1ra) cytokine serum levels were measured in patients who had undergone OSS and MISS, respectively [26]. A two- to sevenfold increase in all markers was observed in the open surgery group. The greatest difference among the groups occurred on the first postoperative day. Most markers returned to baseline in 3 days for the MISS group, whereas the open surgery group required 7  days. IL-6 and IL-8 are known cytokines that participate in various systemic inflammatory reactions [49–51]. It is possible that such elevations in inflammatory cytokines have direct effects beyond the surgical site. The cortical bone trajectory (CBT) technique introduced by Santoni et  al. [52] provides the same stability as open conventional PLIF procedure enabling less tissue dissection and retraction [10, 52]. Paramedian fascial (Wiltse) approach

2  Philosophy and Biology of Minimally Invasive Spine Surgery

has been shown to generate less peak pressure and preserve muscle volume when compared to the traditional middle approach [42, 53, 54]. Decrease of paraspinal muscle CSA and muscle fat infiltration occurs after surgical approach-related injury of the muscle, which depends on the extent of the approach. MISS spine surgery demonstrates preservation of muscle CSA when compared to open approaches [11, 29]. Hung observed an increase in fat CSA/CSA ratio in lumbar multifidus muscle in patients who underwent the open approach PLIF compared to the CBT group [10]. CBT avoids wide dissection of the superior facet joint and reduced incision light and muscle dissection. In CBT group the fat CSA/ CSA ratio was less than in open conventional PLIF [10]. Muscle CSA represents muscle potential contractile force and strength [29]. Kim et  al. compared the back muscle CSA and muscle strength between patients treated with open posterior instrumentation vs. percutaneous instrumentation. Patients undergoing percutaneous instrumentation displayed over 50% improvement in extension strength, while patients undergoing open surgery had no significant improvement in lumbar extension strength [9]. They also observed a significant decrease in the CSA of multifidus muscle in the open posterior instrumentation group. In contrast, there was no statistically significant difference between preoperative and follow-up MRI in the percutaneous instrumentation group [9]. Percutaneous pedicle screw insertion has been shown to cause less paraspinal muscle atrophy and weakness than open pedicle screw insertion [9, 42]; moreover it could have a positive effect on postoperative trunk muscle performance [9]. Nerve traction, cautery, and dissection during pedicle cannulation are the most likely causes of MBN injury [29]. The medial branch of the dorsal rami of the spinal nerve is vulnerable to direct injury during lateral displacement of muscle mass by the retractor or during pedicle screw insertion [10]. The risk of the medial branch transection is significantly higher in open spine surgery compared with MISS in terms of pedicle screw insertion [42] (Fig. 2.4).

2.6.2 Preservation of the BoneLigament Complex Less invasive techniques with unilateral paraspinal approach preserves the natural posterior tension band created by the inter- and supraspinous ligaments [48]. Excessive facet resection leads to altered motion and hence spinal instability [55]. Furthermore, a laminectomy leads to loss of the midline supraspinous ligament complex which can contribute to flexion-extension instability [56, 57]. In cases where

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Fig. 2.4 The minimally invasive translumbar interbody approach using lighted tubular retractors

significant bony resection is required, or when there is an underlying relative instability (such as in spondylolisthesis), concomitant fusion is often recommended following a decompressive laminectomy. Efforts to limit such potentially destabilizing surgery have been pursued via unilateral laminotomies in which the spinous processes and corresponding tendinous attachments of the multifidus muscle and the supraspinous and interspinous ligaments are preserved. When this technique is combined with minimally invasive tubular retractors, bilateral decompression for stenosis can be achieved with good clinical results [58, 59]. The long-­term outcome of such mini-invasive surgery (MIS) procedures and their effect on spinal stability have yet to be shown clinically. However, biomechanical studies suggest that such MIS techniques do maintain spinal stability [58]. Fessler and co-workers compared three decompressive techniques to treat 2-level spinal stenosis: open laminectomies vs. interlaminar midline decompression (which retains the spinous process but sacrifices the interspinous/supraspinous ligaments) vs. MIS unilateral laminotomies [60]. Standard open laminectomy produces marked increases in flexion, extension, and axial rotation. For flexion-extension, there is a greater than two-fold increase in motion which leads to increased stress on the annulus. No changes in flexion were noted when the interlaminar or MIS models were studied. Axial rotation increased by 2.5-fold in the open and interlaminar groups but only 1.3-fold in the MIS group. These findings lend further support to the concept that MIS techniques have relevant effects on spinal motion and stability.

Key Point

Advantages and disadvantages of MISS

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2.7

Conclusions

The main aim of minimally invasive spine surgery is to reduce the trauma inflicted on the patient, while achieving the maximum therapeutic effect [9]. Minimally invasive spine surgery techniques have many advantages with a distinct set of disadvantages: steep learning curve, radiation exposure, and increased operative time, especially during learning period [6, 11, 48]. Minimally invasive spine surgery compared to open approach surgery results in better short-term clinical outcome with excellent good long-term functional results. Minimally invasive techniques have become the method of choice for many surgical procedures [14]. When properly performed minimally invasive techniques help preserve paraspinal muscular anatomy and have been shown to diminish iatrogenic soft tissue injury significantly [14, 33]. Basic science reports, imaging studies, and functional outcome questionnaires demonstrated that MISS techniques have multiple of advantages compared to traditional open surgery.

Summary

• The main aim of minimally invasive spine surgery is to minimize soft tissue trauma, while achieving maximum therapeutic effect. • The key to successfully performing MISS procedures is a thorough understanding of various anatomical relationships between soft tissue planes, approach corridors, bony anatomy, and neurological structures. • Potential causes of muscle injury during surgery include: dissection, retraction, nerve injury, thermal injury, wound exposure, operative time and spinal fusion. • Preservation of paraspinal muscle and nerve supply lead to outcomes. Compared to traditional open surgery, MISS demonstrates reduction in infection rates, decreased postoperative pain, shorter length of hospital stay, earlier rehabilitation, shorter recovery time before ambulation, less blood loss, decreased need of transfusion, decreased paraspinal muscle atrophy, improvement in spine extension strength, better cosmetic outcomes, improvement in quality of life, and clinical benefits demonstrated on both physical and mental components of health quality outcome measurement tools. • Minimally invasive procedures are technically demanding and require advanced training and mentorship. Steep learning curve, radiation exposure, and increased operative time, especially during learning period are the main disadvantages of MISS.

Quiz Questions 1. The potential causes of muscle injury are: (a) Dissection, retraction, and nerve injury. (b) Wound exposure and operative time. (c) Wound exposure, operative time, and spinal fusion. (d) All above answers are correct. 2. Which nerve supplies the lumbar multifidus muscle: (a) Medial branch of the dorsal rami of the spinal nerve. (b) Intermediate branch of the dorsal rami of the spinal nerve. (c) Lateral branch of the dorsal rami of the spinal nerve. (d) None of above answers is correct. 3. Which answer includes only the advantages of MISS? (a) Lower infection rates, decreased postoperative pain, shorter length of hospital stay, decreased blood loss, and decreased paraspinal muscle atrophy. (b) Lower infections rates, shorter length of hospital stay, decreased blood loss, decreased paraspinal muscle atrophy, and shorter operative time. (c) Decreased radiation exposure, decreased operative time, decreased postoperative pain, and shorter length of hospital stay. (d) Improvement in spine extension strength, better cosmetic outcomes, and decreased radiation exposure.

Answers 1. d 2. a 3. a

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2  Philosophy and Biology of Minimally Invasive Spine Surgery 8. Hu ZJ, Fang XQ, Fan SW. Iatrogenic injury to the erector spinae during posterior lumbar spine surgery: underlying anatomical considerations, preventable root causes, and surgical tips and tricks. Eur J Orthop Surg Traumatol. 2014;24(2):127–35. 9. Kim DY, Lee SH, Chung SK, Lee HY. Comparison of multifidus muscle atrophy and trunk extension muscle strength: percutaneous versus open pedicle screw fixation. Spine (Phila Pa 1976). 2005;30(1):123–9. 10. Hung CW, Wu MF, Hong RT, Weng MJ, Yu GF, Kao CH. Comparison of multifidus muscle atrophy after posterior lumbar interbody fusion with conventional and cortical bone trajectory. Clin Neurol Neurosurg. 2016;145:41–5. 11. Fan S, Hu Z, Zhao F, Zhao X, Huang Y, Fang X. Multifidus muscle changes and clinical effects of one-level posterior lumbar interbody fusion: minimally invasive procedure versus conventional open approach. Eur Spine J. 2010;19:316–24. 12. Perez-Cruet MJ, Hussain NS, White GZ, Begun EM, Collins RA, Fahim DK, Yacob SA.  Quality-of-life outcomes with minimally invasive transforaminal lumbar interbody fusion based on long-­ term analysis of 304 consecutive patients. Spine (Phila Pa 1976). 2014;39(3):191–8. 13. Cholewicki J, Panjabi M, Khachatryan A.  Stabilizing function of trunk flexor-extensor muscles around a neutral spine posture. Spine (Phila Pa 1976). 1997;22(19):2207–12. 14. Panjabi MM. The stabilizing system of the spine. Part II. Neutral zone and instability hypothesis. J Spinal Disord. 1992;5:390–6; discussion 7. 15. Panjabi MM.  The stabilizing system of the spine. Part I. function, dysfunction, adaptation, and enhancement. J Spinal Disord. 1992;5:383–9; discussion 97. 16. Panjabi MM, Lydon C, Vasavada A, Grob D, Crisco JJ 3rd, Dvorak J.  On the understanding of clinical instability. Spine (Phila Pa 1976). 1994;19:2642–50. 17. Panjabi MM, White AA 3rd. Basic biomechanics of the spine. Neurosurgery. 1980;7:76–93. 18. Donisch E, Basmajian J. Electromyography of deep back muscles in man. Am J Anat. 1972;133(1):25–36. 19. Ward SR, Kim CW, Eng CM, Gottschalk LJ 4th, Tomiya A, Garfin SR, Lieber RL. Architectural analysis and intraoperative measurements demonstrate the unique design of the multifidus muscle for lumbar spine stability. J Bone Joint Surg Am. 2009;91:176–85. 20. Macintosh JE, Bogduk N. The biomechanics of the lumbar multifidus. Clin Biomech. 1986;1:205–13. 21. Marras WS, Davis KG, Granata KP. Trunk muscle activities during asymmetric twisting motions. J Electromyogr Kinesiol. 1998;8:247–56. 22. MacIntosh JE, Bogduk N. The morphology of the lumbar erector spinae. Spine (Phila Pa 1976). 1987;12:658–68. 23. Macintosh JE, Bogduk N. The attachments of the lumbar erector spinae. Spine (Phila Pa 1976). 1991;16:783–92. 24. Bogduk N, Macintosh JE, Pearcy MJ.  A universal model of the lumbar back muscles in the upright position. Spine (Phila Pa 1976). 1992;17:897–913. 25. Delp SL, Suryanarayanan S, Murray WM, Uhlir J, Triolo RJ. Architecture of the rectus abdominis, quadratus lumborum, and erector spinae. J Biomech. 2001;34(3):371–5. 26. Kim KT, Lee SH, Suk KS, Bae SC. The quantitative analysis of tissue injury markers after mini-open lumbar fusion. Spine (Phila Pa 1976). 2006;31:712–6. 27. Waschke A, Hartmann C, Walter J, Dünisch P, Wahnschaff F, Kalff R, Ewald C. Denervation and atrophy of paraspinal muscles after open lumbar interbody fusion is associated with clinical outcome— electromyographic and CT-volumetric investigation of 30 patients. Acta Neurochir. 2014;156(2):235–44. 28. Styf JR, Willén J. The effects of external compression by three different retractors on pressure in the erector spine muscles during

27 and after posterior lumbar spine surgery in humans. Spine (Phila Pa 1976). 1998;23(3):354–8. 29. Cawley DT, Alexander M, Morris S.  Multifidus innervation and muscle assessment post-spinal surgery. Eur Spine J. 2014;23(3): 320–7. 30. Kjaer P, Bendix T, Sorensen JS, Korsholm L, Leboeuf-Yde C. Are MRI-defined fat infiltrations in the multifidus muscles associated with low back pain. BMC Med. 2007;5(1):2. 31. Zoidl G, Grifka J, Boluki D, Willburger RE, Zoidl C, Krämer J, Faustmann PM.  Molecular evidence for local denervation of paraspinal muscles in failed-back surgery/postdiscotomy syn­ drome. Clin Neuropathol. 2002;22(2):71–7. 32. Sihvonen T, Herno A, Paljärvi L, Airaksinen O, Partanen J, Tapaninaho A.  Local denervation atrophy of paraspinal muscles in postoperative failed back syndrome. Spine (Phila Pa 1976). 1993;18(5):575–81. 33. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine surgery: 2. Histologic and histochemical analyses in humans. Spine (Phila Pa 1976). 1994;19:2598–602. 34. Rantanen J, Hurme M, Falck B, Alaranta H, Nykvist F, et al. The lumbar multifidus muscle five years after surgery for a lumbar intervertebral disc herniation. Spine (Phila Pa 1976). 1993;18:568–74. 35. Matsukawa K, Yato Y, Kato T, Imabayashi H, Asazuma T, Nemoto K.  In vivo analysis of insertional torque during pedicle screwing using cortical bone trajectory technique. Spine (Phila Pa 1976). 2014;39:240–5. 36. Bogduk N.  The lumbar mamilloaccessory ligament. Its ana tomical and neurosurgical significance. Spine (Phila Pa 1976). 1981;6:162–16. 37. Bogduk N, Wilson AS, Tynan W. The human lumbar dorsal rami. J Anat. 1982;134:383–97. 38. Malis LI.  Electrosurgery: technical note. J Neurosurg. 1996;85(5):970–5. 39. Konno S, Olmarker K, Byröd G, Nordborg C, Strömqvist B, Rydevik B.  Acute thermal nerve root injury. Eur Spine J. 1994;3(6):299–302. 40. Kim CW. Scientific basis of minimally invasive spine surgery: prevention of multifidus muscle injury during posterior lumbar surgery. Spine (Phila Pa 1976). 2010;35(26S):281–6. 41. Kim CW, Siemionow K, Anderson DG, Phillips FM. The current state of minimally invasive spine surgery. J Bone Joint Surg Am. 2011;93(6):582–96. 42. Regev GJ, Lee YP, Taylor WR, Garfin SR, Kim CW.  Nerve injury to the posterior rami medial branch during the insertion of pedicle screws: comparison of mini-open versus percutaneous pedicle screw insertion techniques. Spine (Phila Pa 1976). 2009;34(11):1239–42. 43. Styf J, Lysell E. Chronic compartment syndrome in the erector spinae muscle. Spine (Phila Pa 1976). 1987;12(7):680–2. 44. Gejo R, Matsui H, Kawaguchi Y, Ishihara H, Tsuji H. Serial changes in trunk muscle performance after posterior lumbar surgery. Spine (Phila Pa 1976). 1999;24:1023–8. 45. Kawaguchi Y, Matsui H, Tsuji H. Back muscle injury after posterior lumbar spine surgery: 1. Histologic and histochemical analyses in humans. Spine (Phila Pa 1976). 1994;19:2590–7. 46. Boelderl A, Daniaux H, Kathrein A, Maurer H. Danger of damaging the medial branches of the posterior rami of spinal nerves during a dorsomedian approach to the spine. Clin Anat. 2002;15(2): 77–81. 47. Hayashi N, Tamaki T, Yamada H. Experimental study of denervated muscle atrophy following severance of posterior rami of the lumbar spinal nerves. Spine (Phila Pa 1976). 1992;17:1361–7. 48. Peng CWB, Yue WM, Poh SY, Yeo W, Tan SB.  Clinical and radiological outcomes of minimally invasive versus open transforaminal lumbar interbody fusion. Spine (Phila Pa 1976). 2009;34(13):1385–9.

28 49. Baggiolini M, Dewald B, Moser B. Interleukin-8 and related chemotactic cytokines—CXC and CC chemokines. Adv Immunol. 1994;55:97–179. 50. Hirano T, Yasukawa K, Harada H, Taga T, Watanabe Y, Matsuda T, Kashiwamura S, Nakajima K, Koyama K, Iwamatsu A, et  al. Complementary DNA for a novel human interleukin (BSF-2) that induces B lymphocytes to produce immunoglobulin. Nature. 1986;324:73–6. 51. Igonin AA, Armstrong VW, Shipkova M, Lazareva NB, Kukes VG, Oellerich M. Circulating cytokines as markers of systemic inflammatory response in severe community-acquired pneumonia. Clin Biochem. 2004;37:204–9. 52. Santoni BG, Hynes RA, McGilvray KC, Rodriguez-Canessa G, Lyons AS, Henson MA, Womack WJ, Puttlitz CM.  Cortical bone trajectory for lumbar pedicle screws. Spine (Phila Pa 1976). 2009;9:366–73. 53. Hyun SJ, Kim YB, Kim YS, Park SW, Nam TK, Hong HJ, Kwon JT. Postoperative changes in paraspinal muscle volume: comparison between paramedian interfascial and midline approaches for lumbar fusion. J Korean Med Sci. 2007;22(4):646–51. 54. Stevens KJ, Spenciner DB, Griffiths KL, Kim KD, Zwienenberg-­ Lee M, Alamin T, Bammer R. Comparison of minimally invasive and conventional open posterolateral lumbar fusion using magnetic

P. Glowka et al. resonance imaging and retraction pressure studies. J Spinal Disord Tech. 2006;19(2):77–86. 55. Abumi K, Panjabi MM, Kramer KM, Duranceau J, Oxland T, Crisco JJ. Biomechanical evaluation of lumbar spinal stability after graded facetectomies. Spine (Phila Pa 1976). 1990;15:1142–7. 56. Tuite GF, Doran SE, Stern JD, McGillicuddy JE, Papadopoulos SM, Lundquist CA, Oyedijo DI, Grube SV, Gilmer HS, Schork MA, et al. Outcome after laminectomy for lumbar spinal stenosis. Part II: radiographic changes and clinical correlations. J Neurosurg. 1994;81:707–15. 57. Johnsson KE, Willner S, Johnsson K. Postoperative instability after decompression for lumbar spinal stenosis. Spine (Phila Pa 1976). 1986;11:107–10. 58. Palmer S. Use of a tubular retractor system in microscopic lumbar discectomy: 1 year prospective results in 135 patients. Neurosurg Focus. 2002;13:E5. 59. Guiot BH, Khoo LT, Fessler RG. A minimally invasive technique for decompression of the lumbar spine. Spine (Phila Pa 1976). 2002;27:432–8. 60. Bresnahan L, Ogden AT, Natarajan RN, Fessler RG. A biomechanical evaluation of graded posterior element removal for treatment of lumbar stenosis: comparison of a minimally invasive approach with two standard laminectomy techniques. Spine (Phila Pa 1976). 2009;34:17–23.

3

Economics of Minimally Invasive Spine Surgery Robert A. Ravinsky and Y. Raja Rampersaud

Learning Objectives

• Gain an understanding of the importance of and role for economic studies in minimally invasive spine surgery from the clinician’s perspective. • Describe the different types of health economic evaluations and their respective advantages and drawbacks. • Describe the difference between direct and indirect costs. • Provide a summary of the literature as it relates to the economics of minimally invasive spine surgery • Identify the current knowledge gaps and directions for future investigation.

3.1

Introduction

In most countries, the cost of healthcare has progressively increased at a rate greater than the respective national economic growth [1]. Consequently, healthcare delivery in its present state is unsustainable and, in many countries, has already resulted in increased taxation as well as decreased government funding of other vital societal services. From a macroeconomic perspective, the economic impact of healthcare interventions is critically important to all stakeholders. As stakeholders in healthcare management and delivery attempt to mitigate increasing expenditures, greater demands are made upon all therapies to describe their proven indications, report adverse events, and delineate their objective and subjective outcomes [2]. With increasing costs, it also becomes necessary for health providers and payers to assess the value (defined as R. A. Ravinsky · Y. R. Rampersaud (*) University Health Network, Toronto Western Hospital, University of Toronto, Department of Surgery, Division of Orthopaedics, Toronto, ON, Canada e-mail: [email protected]

the relative worth, utility, or importance) of an intervention compared to alternative interventions. These needs have been highlighted by the Institute of Medicine (IOM) as comparative effectiveness research (CER). As per the IOM, “Comparative effectiveness research is the generation and synthesis of evidence that compares the benefits and harms of alternative methods to prevent, diagnose, treat, and monitor a clinical condition or to improve the delivery of care. The purpose of CER is to assist consumers, clinicians, purchasers, and policy makers to make informed decisions that will improve health care at both the individual and population levels.” [3–5] Physicians have traditionally understood and taken the perspective of safety and clinical efficacy of an intervention. However, physicians are often less familiar with the perspective and language of purchasers and policy makers, which also includes the health economic aspect of not only the intervention of interest to a specific health provider but also its impact and relevance to other relevant interventions and healthcare delivery at a macro level.

3.2

Health Economic Evaluations (HEEs)

3.2.1 T  he Importance of Health Economic Evaluations From the perspective of musculoskeletal surgery, the increasing demands for surgical services will only continue to increase [6–13]. It is estimated that by the year 2030, over half of the adults in the US population will be aged over 65  years. The economic effects of degenerative disorders such as arthritis of the spine (i.e., spinal stenosis), hip, and knee within this aging population will have profound implications on the future affordability and availability of quality spine care [6–13]. Within spine surgery, the SPORT studies [14–17] have documented the sustainable efficacy and cost-­ effectiveness of interventions using traditional open surgical

© Springer Nature Switzerland AG 2019 F. M. Phillips et al. (eds.), Minimally Invasive Spine Surgery, https://doi.org/10.1007/978-3-030-19007-1_3

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techniques for lumbar disk herniation, spinal stenosis, and degenerative spondylolisthesis compared to nonsurgical care at 4 years of follow-up. However, CER within the spine surgery literature from an economic perspective was until more recently generally lacking. In recent years, an increasing interest in this type of research including economic analyses has emerged. This is likely due to increasing pressure on the part of healthcare providers to justify health expenditures to payers and demonstrate that the treatments they provide are of value. Nevertheless, although the need for economic data in the current healthcare climate is increasingly important, there is a general paucity of cost-effectiveness analyses (CEA) across all surgical and nonsurgical interventions [18]. In addition, societal perceptions regarding spine surgery and its benefits, risk, and associated costs may also have an impact on the perceived value of spinal intervention, regardless of whether it demonstrated cost-effectiveness. Unfortunately, the substantial variability in results along with differences in clinical indications and techniques used further confounds existing external opinions regarding spine surgery and surgical techniques [8]. The prevailing perspectives from nonspine surgeons (i.e., payers and nonsurgical spine specialist) seem to be that much of what is done in spine surgery is for the management of low back pain and is ineffective. Our day-to-day outcomes for common diagnoses such as radiculopathy or claudication would say otherwise, but we need to continue to prove it. With these aforementioned challenges in mind, it is important to quantify the value of surgical intervention for degenerative conditions, and these interventions must be appraised from the perspectives of the patient, direct payer, and society. As diminishing healthcare resources must be stretched further and further, resource allocation for competing pathologies including cancer and chronic conditions such as cardiovascular disorders, diabetes, and arthritis currently demands the largest portion of available funds. In a publication by Martin et al. that looked at expenditures and health status among US adults with back and neck problems, the authors noted significantly escalating cost (the vast majority of which is nonoperative) with no appreciable improvement in health status compared to non-back/neck individuals [19]. The estimated annual US expenditures for back and neck disorders ($86 billion) in 2005 have reached levels comparable to diabetes ($98 billion), cancer ($89 billion), and arthritis ($80 billion) in a similar period. These are all second to heart and stroke expenditures which are estimated at $260 billion. A discussion of societal and payer prioritization regarding relative healthcare resource allocation is clearly a complex issue which is not within the scope of this chapter but is worthy of mention to enable the reader to keep the broader perspective of payers and policy makers in mind as they increase their personal understanding of CER.

R. A. Ravinsky and Y. R. Rampersaud

3.2.2 T  he Language of Health Economic Analysis A detailed description of HEE is not within the scope of this text and thus only fundamental concepts relevant to the surgeon, from the perspective of the clinician/surgeon will be provided [20]. A common misconception from physicians and surgeons is that all HEEs are the same and only consider the bottom line, cost. There are, in fact, several types of HEE that are not interchangeable and require a more profound understanding when a clinician is considering the merit of an HEE. Some HEEs only consider cost and assume that the clinical efficacy is equal between the interventions of interest, whereas others consider both the relative cost and efficacy of the intervention. Additionally, it is important to understand the perspective of the costing data sources and whether it only considers some or all healthcare costs attributable to a specific intervention and whether societal cost, such as productivity, has been included in the analysis [20, 21]. Another important aspect of an HEE is the time horizon in which the analysis has been considered, for some studies may consider the perioperative period only whereas others evaluate costs over the lifetime of the patient. Given the potential differences in study time horizon being evaluated, one must also consider whether the assumptions and variability associated with critical analytic parameters are a­ ccurate and accounted for in the study. For HEEs where the outcome measure and cost are estimated for the lifetime of the patient, future costs and utilities are typically discounted to adjust for society’s relative value placed on immediate costs and benefits compared to those in the future, a concept known as time preference [21]. Commonly, resources in the present are preferred over future resources since benefit can be derived from present resources in the interim. Most importantly when comparing interventions within the same analysis or across different analyses, it is necessary to ensure that compatible clinical, costing, analytic model assumptions, and overall economic analysis and perspective were employed between groups. Variations in these parameters can grossly impact the outcome and subsequent interpretation of an HEE. Consequently, an important

Key Points

• In the setting of limited healthcare resources, economic evaluation of therapeutic interventions is needed to demonstrate that the financial cost of the intervention is justified by the amount of value that the intervention creates for the patient. • In healthcare, policy makers must make careful decisions about how finances are allocated such that the amount of created value is optimized while minimizing cost. This is accomplished through HEEs.

3  Economics of Minimally Invasive Spine Surgery

part of an HEE is the inclusion sensitivity analysis within the methodology. This enables relevant and realistic variation of important clinical and economic parameters to assess the robustness of the HEE findings and allows the reader to interpret the results based on alternate parameters that may be more consistent with their local healthcare system [21]. As HEEs can be carried out in many ways and customized to specific objectives, the outcome will be potentially interpreted differently based on the perspective taken by different stakeholders. For example, from the perspective of a private payer, the primary goal might be to obtain the greatest return on their investment. From a physician’s perspective, patient outcomes and clinical outcomes such as procedural time or adverse events, regardless of the economic aspect, might be the major issues of consideration. From the patient’s or a societal viewpoint, personal factors such as quality of life post-surgery, recovery time, and ongoing costs along with activity factors such as days of work missed and productivity losses may be most relevant.

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3.2.4 C  ost-Effectiveness (CEA) and Utility (CUA) Analyses The primary premise of a CEA is the measurement of the incremental cost and patient benefit that result from choosing one intervention option over another [22, 23]. The purpose is to assist decision-makers in determining how to allocate resources across a defined number of competing needs to optimize health outcomes while adhering to budgetary constraints [23]. CEA is distinct from the aforementioned economic analyses such as a CA or CBA, as it simultaneously considers clinical effectiveness and cost. Within healthcare, CEA is utilized in scenarios where assigning a monetary value to a health state may be inappropriate. A CEA is typically calculated using an incremental cost-­effectiveness ratio (ICER), which equals the cost of a new strategy less the cost of current practice, divided by the clinical change in outcome of the new strategy, minus the current practice [24]. ICER =

3.2.3 Definitions of HEEs The most basic type of economic analysis is cost analysis (CA) which compares the cost of healthcare interventions and does not consider differences in health outcomes [20]. This type of analysis is obviously very “payer” focused; it evaluates interventions based on their costs only, and from a clinical perspective this type of analysis is not useful for CER, but represents the most common analysis in the surgical literature. Another type of economic analysis is cost-­minimization analysis (CMA) which determines and evaluates the least expensive interventions among the interventions that have demonstrated the same outcomes. This type of analysis may be tedious to complete because one must first demonstrate that the resulting outcomes between interventions are, in fact, the same, which can prove to be a challenging task on its own. A CMA can be effective at any level where reducing expenditure is a priority and therapeutic equipoise from high-quality evidence has been established between two interventions for the same clinical scenario. A cost-benefit analysis (CBA) refers to an HEE where both the cost of the interventions and their outcome are assessed in terms of dollars. It is reflected as the ratio of the difference in outcome (e.g., cost difference of length of stay between two interventions) over the difference in cost. A CBA ratio greater than 1 suggests a cost-benefit of the intervention under evaluation. From a CER perspective, a cost-­effectiveness analysis (CEA) which simultaneously considers both the comparative clinical effectiveness and cost of intervention is the HEE method of choice [20]. Thus, being cost-­effective does not necessarily mean an intervention is less expensive up front.



Cost new strategy - Cost current practice Effect new strategy - Effect current practice

The ICER analysis typically assumes that the new strategy is likely to cost more but has a clinically greater effect and is hence used to determine the cost per incremental difference in outcome.

Key Points

All of the following are different types of HEEs: • Cost analysis (CA)—Compares the costs of two or more interventions without taking outcomes into consideration. • Cost-minimization analysis (CMA)—Compares the costs of two or more interventions, whose outcomes have been demonstrated to be equivalent. • Cost-benefit analysis (CBA)—HEE where two interventions are compared and both the cost and the outcomes of the intervention are measured in monetary units. • Cost-effectiveness analysis (CEA) and cost-utility analysis (CUA)—HEEs which compare interventions while considering both financial cost and clinical effectiveness.

3.2.5 Components of A CEA As stated previously, economic analysis can be a complex and difficult task, especially when cause-and-effect relationships are not very easily measured. Another aspect which

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increases difficulty is the sheer volume of variables that can contribute to the overall cost of a health intervention. Thus, collecting detailed costing data is very time-consuming and costly and represents a significant barrier in performing CEAs. Often, it can be beneficial to break down the analysis into two smaller analyses: factors that directly contribute to cost and factors which have an indirect effect on cost.

3.2.5.1 Direct Costs Direct costs are tangible costs such as the cost of medical tests, implants, operating room time, rehabilitation, or out-­of-­pocket cost for payment of healthcare services that an individual may no longer be able to perform as a direct result of a disease state. Proponents [25–31] of minimally invasive procedures frequently cite that the advantage of MIS versus open surgery is its ability to lower postoperative morbidity. In a review by Allen and Garfin, the authors outlined the factors in open procedures that may increase cost relative to MIS [32]. Factors such as increased blood loss and subsequently transfusion rates, extended OR time, and the use of open posterior approach to the spine can increase the likelihood of adverse events, such as infection, and procedure-related morbidity, such as pain [32–34]. For example, the costs surrounding a unit of blood transfused are estimated to be just under $1200, and this measure is often associated with increased LOS and resource utilization [32]. Kalanithi et  al. reported that each in-hospital complication for patients undergoing surgery for acquired spondylolisthesis was associated with an increased cost of approximately 10,000 USD, with the total cost rising to over three times the cost of the index procedure if any readmission and revision surgeries were performed [33]. Khan et  al. reported that a single complication may increase hospital costs for a patient in general surgery by up to 79% [35]. Broken down further, the median costs per complication resulted in costs of 4278 USD (range, 2511–25,168 USD) and as a result increased LOS by 11–297% [35]. When complications occur, significant increases in LOS, mean total charges, and in-hospital mortality are observed [33]. Consequently, taking steps to decrease the probability of adverse events and reduce LOS by using MIS techniques, as well as other available interventions, may help lower these associated costs substantially [36]. 3.2.5.2 Indirect Costs Indirect costs are more variable and depend on what is considered to be indirectly associated with a given disease state or intervention. Consequently, the determination of indirect cost is typically much more difficult. In their simplest form, indirect cost can be those associated with direct medical cost (e.g., the estimated institutional overhead to provide a ser-

R. A. Ravinsky and Y. R. Rampersaud

vice). More commonly, indirect costs refer to societal cost such as lost productivity. However, it is also important to consider that many indirect costs from a societal perspective may also be very closely related to direct costs, further increasing complexity. For example, postoperative complications such as infections following surgery may result in longer hospital stays, greater recovery time, and additional medication costs contributing to an overall decline in health. These direct costs also influence societal indirect costs as the individual may be out of the work force for a longer time, thereby decreasing their productivity. Thus, isolating and analyzing costs independently of each other can be challenging, and results must be interpreted within a defined context and in relation to other factors as opposed to individually. Low back pain (LBP) is a good example of indirect costs from a macroeconomic perspective. The societal costs of LBP can be substantial. LBP has become the second most common reason for patients to visit primary care providers [37]. A systematic review of studies published in 2005, evaluating the cost of low back pain noted that costs resulting from lost productivity and early retirement were the largest component of total costs, representing a median of 85% of overall costs [38]. Consequently, indirect cost, particularly from a societal perspective, is an important measure of postoperative ongoing cost beyond discharge from hospital and provides a more comprehensive allocation of the costs associated with any intervention. In a 2004 study, Fritzell et al. reported that treating an individual with open lumbar fusion surgery was less expensive (and thus more beneficial) than to have the person not contribute to societal productivity while receiving conservative care treatment [39, 40]. It follows that those indirect benefits would decrease if the surgical intervention resulted in less morbidity, faster recovery, and resumption of functional activity (e.g., work); in other words, the promise of MIS should result in reduced cost.

3.2.6 Effectiveness Effectiveness can be measured in a variety of ways depending on the most relevant outcome of the interventions assessed. For example, if mortality rate was the best outcome measure for a new therapy, the cost-effectiveness could be represented as the incremental cost per additional life saved or cost per adverse event avoided if the outcome of interest is morbidity. For elective surgical procedures, the most common form of a CEA is a cost-utility analysis (CUA), which measures effectiveness using a generic health utility score that allows the comparison of different health states by measuring them all in terms of a single unit—the quality-adjusted life year (QALY). A QALY is a measure of the burden of a disease on life and encompasses

3  Economics of Minimally Invasive Spine Surgery

both the quality and quantity of life lived [18, 21]. Thus, for HEEs, it represents both the effect size and durability of a given intervention. A QALY is an index number that is calculated by multiplying the utility score associated with that treatment by the duration of treatment effect. The utility score represents the health-related quality-of-life value in a range from 0 to 1, with 0 representing death and 1 representing the best or perfect health state. The utility score used to calculate the QALY of an intervention has been derived from several existing generic health-related measures, such as the EQ-5D, Health Utilities Index, Quality of Well-Being Scale, and SF-36 (expressed as SF-6D) [41–49]. Consequently, the QALY is an outcome measure that enables decision-makers to compare the effectiveness of interventions across many different areas of medicine and different disease states. For this purpose, decision-makers utilize CEAs (and specifically CUAs) to identify the costs associated in achieving a single QALY (i.e., the relative value of a given intervention). It is important to note that currently available health utility scores are not interchangeable as they often generate different values from within the same population, and thus the cost/ QALY values may differ depending on which utility score was utilized [41, 48, 49]. Equally important to the QALY effect size of an intervention on the health utility index of an individual or population is the ability of an intervention to maintain that improved health state, or the durability of the treatment effect [14, 18, 21]. Tosteson et  al. have demonstrated this concept in the spine literature [14]. In their landmark report of the 4-year cost-effectiveness of surgery versus nonoperative treatment from the SPORT studies, the authors demonstrated sustainable superior results (QALYs gained) from surgical compared to nonsurgical treatment. This corresponded to an improvement in the dollars spent/QALY gained ratio (ICUR) at 4 years compared to 2 years for all three subpopulations studied. For spinal stenosis, the 2- and 4-year ICUR for surgery compared to nonoperative treatment was $77,600 and 59,400. For the treatment of intervertebral disk herniation, the ICUR decreased from $34,355 at 2 years to $20,600 at 4 years. The greatest improvement was seen for the degenerative spondylolisthesis cohort, where the ICUR went down to $64,300 at 4 years compared to $115, 600 at 2 years. In more traditional economic models, where the QALY is estimated over the lifetime of the patient based on reference case data, the ICUR will typically reduce below $10,000/ QALY for musculoskeletal interventions such as hip and knee replacement or 1–2-level spinal stenosis surgery [50]. For MISS lumbar fusion, both Rouben et al. and Harris et al. have demonstrated good durability beyond the 2-year mark for MIS-TLIFs [51, 52].

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Finally, when faced with a cost per QALY evaluation, recommendations exist regarding the threshold for which an intervention is considered cost-effective. Generally, an ICUR greater than $100,000 per QALY is considered too costly for the utility gained [53, 54]. This number can vary from country to country and typically ranges 50–100  K USD/QALY [21]. Furthermore, the number may vary depending on the clinical context that is being considered based on the local societal value of the given intervention (e.g., life-extending cancer surgery vs. improvement on quality of life).

Key Points

• Direct healthcare costs: Tangible costs incurred by the payer, related to healthcare resource utilization in the care of a patient. These may include the costs of diagnostic tests, the operating room, costs associated with hospitalization, and the costs associated with rehabilitation. • Indirect healthcare costs: These are most common costs from the societal perspective, related to patient time away from the workforce and caregiver burden (i.e., loss of productivity). In addition, indirect cost may also include infrastructure and operational cost associated with direct cost items.

3.3

 linician’s Approach to HEE for MIS C of the Spine

Table 3.1 demonstrates the possible relationships between cost and effectiveness and can be utilized to better discern when a CEA might be worthwhile [20]. Simply put, if a new intervention provides better outcomes and reduced cost, it has greater value than the current treatment and should be adopted. Conversely, if a new procedure is less effective and cost more, it should not be supported in its current form. All other scenarios typically will require a formal CEA to determine the relative value of an intervention compared to its alternatives [20]. From this fundamental approach, the first step would be the need to answer the question of if minimally invasive spine surgery (MISS) is clinically more or less effective when compared to open surgery. In the last several years, an increasing number of observational studies and randomized trials comparing open versus MIS lumbar fusion techniques for degenerative conditions have been published. Across the literature, several different outcome measures have been considered to make this comparison. Details of outcomes for specific techniques are avail-

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R. A. Ravinsky and Y. R. Rampersaud

Table 3.1  Principle approach to determining the need for a formal cost-effectiveness analysis (CEA) Effectiveness of new strategy More effective

Costs of new strategy Costs more CEA relevant

Less effective

New strategy is ineffective—abandon

Costs less New strategy is dominant—adopt CEA relevant

able in chapters specific to certain MIS techniques. Recently, Goldstein et  al. have published a systematic review of randomized and nonrandomized studies comparing the health economics of MIS to open techniques for posterior lumbar interbody fusion [55]. This systematic review found 45 studies, with a total of 9396 subjects that met inclusion criteria, studies comparing MIS to open trans-foraminal and posterior lumbar interbody fusion, with a minimum of 10 patients in each arm, with at least one of the following types of outcome measures: clinical, perioperative, radiographic, adverse event or economic outcome. This included 3 prospective randomized controlled trials, 17 prospective cohort studies, and 25 retrospective cohort studies. Using the GRADE system, the quality of evidence was low (19 studies) to very low (26). The perioperative outcomes included operating room (OR) time, estimated blood loss (EBL), and length of hospital stay (LOS). While there was variability in the outcomes of OR time when comparing MIS to open interbody fusion in the various studies, with some studies demonstrating longer operative times in MIS while others demonstrated reduced operative times, the MIS cohorts performed better than the open cohorts with regard to both EBL and LOS. The only radiographic outcome considered in the included studies was the rate of nonunion, of which no statistically significant difference was noted in any of the 23 studies reporting on this outcome. Complication rates were included in 35 of the included studies, and nine studies found there to be a higher complication rate in open surgery compared to MIS, while the remainder of the studies did not note a difference. Thirty-two studies included some form of patient-reported outcomes, including the VAS, ODI, SF-36, SF-12, and EQ-5D.  With respect to VAS, no significant difference was reported between the MIS and open cohorts in the majority of studies. Moreover, no significant differences were noted between the MIS and open cohorts with respect to ODI, SF-36, SF-12, and EQ-5D. With respect to economic outcomes, 9 of the 45 studies included HEEs. All nine of these studies found reduced cost/charges in the MIS cohorts when compared to open surgery [55]. In addition to the aforementioned systematic review, Phan et al. performed a systematic review and economic evaluation of studies comparing the cost-utility and perioperative costs of minimally invasive (MI) versus open TLIF [56]. They searched six electronic databases for comparative studies comparing MIS versus open TLIF and reporting direct hospi-

tal costs. Studies were excluded if they contained fewer than ten patients per group or did not have a comparator group. The primary outcome of interest was direct hospital costs of MIS and open TLIF. All costs were reported in USD. Baseline data collected for all patients included age, sex, and preoperative VAS and ODI scores. Perioperative outcomes of interest included OR duration, EBL, total complication rates, and hospitalization. Two independent reviewers performed risk of bias assessment according to the Dutch Cochrane Working Group MOOSE recommendations for systematic reviews and observational studies. Clinical outcomes were assessed using standard meta-analysis techniques for calculating relative risk (RR) for binomial variables and weighted mean difference (WMD) for continuous variables. Both fixed effects and random effects models were used to calculate RR and WMD. Tests for heterogeneity were carried out. Publication bias was assessed using the funnel plot method. After completing the literature search, six articles had met inclusion criteria, three were prospective observational studies, while three were retrospective observational studies. In their results, the authors noted that direct hospital costs for MI-TLIF ranged from $10,770 to $24,201, while those for open-TLIF ranged from $12,011 to $37,681. For each study, the direct hospital cost of MI-TLIF was less than that of open-TLIF, and in the meta-analysis this finding was statistically significant (WMD, −$2820, 95% CI −4020, −1630; I2  =  61%, p