Using an endoscope In minimally invasive spine surgery

Using an endoscope In minimally invasive spine surgery (MISS) Authors: Christoph Hofstetter and Jin. Sung Kim AO Spine MISS Task Force Version: March 2021

Learning objectives • • Describe characteristics and set-up of working channel endoscopes Identify differences between microscopes and endoscopes Describe how to handle an endoscope Explain key differences of working channel endoscopes for transforaminal vs interlaminar approaches Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Definition of “endoscopy” • • Use a thin, tubular and coaxial surgical instrument that contofains image transmission, illumination, and irrigation and a working channel Two Greek roots: • ἔνδον (éndon) = inside • σκοπεῖν (skopein) = to observe Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

History of endoscopy • Philipp Bozzini (Germany, 1805) • A candle-illuminated device to observe the living human body directly through a tube (Lichtleiter) to examine the urinary tract, rectum, and pharynx Philipp Bozzini Antoin Jean Desormeaux • Desormeaux (France, 1853) • Masaki Watanabe (Japan, 1950) Developed early arthroscopes during the 1950 with a superior handmade lens Masaki Watanbe Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

History of spinal endoscopy Lumbar spine—common pathology—disc herniation: (“blind” procedures) • APLD (automated percutaneous lumbar discectomy) • Laser decompression (Mayer & Brock): “PELD” (percutaneous endoscopic laser discectomy) • Knight (2001) “Foraminoplasty” • Kambin & Zhou: “Kambin’s triangle” (safe working zone) Kombin’s Triangle Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Working channel endoscope The endoscope has four components: • Optical system (typically a rod-lens system) • Illumination (xenon light) • Irrigation channel • Working channel Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Microscope vs working channel endoscope Microscope Endoscope Working distance 300 mm 3 mm Illumination 300 mm from target 3 mm from target Field of view Restricted by the tubular retractor Wide-angle panoramic viewing field Line of sight Straight 15– 30° off axis Image 3 -D 2 -D Instruments Standard bayonetted Specialized tools Retractor Bladed, tubular Tubular, irrigation fluid Working corridor Bimanual Single working channel Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Endoscope vs MISS ipsilateral recess decompression Microscope Endoscope The endoscope allows for decompression and direct visualization of the ipsilateral traversing nerve root due to: • Panoramic visualization • Off-angle (15– 25°) visualization • Narrow tubular retractor (endoscope: diameter 7– 10 mm vs 18 mm MIS) Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Endoscope vs MISS contralateral recess decompression Microscope Endoscope The endoscope facilitates undercutting of the contralateral recess: • Retraction of thecal sac by continuous irrigation • Protected side-biting burrs • Illumination and camera within the spinal canal Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Tubular retractor • Specialized tubular retractors exist for interlaminar and transforaminal applications • The tubular retractor serves the following functions: • Protects operative field from tissue creep • Bevel functions as elevator • Bevel can be used to retract neural structures Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Tubular retractor • Optimization of off-axis reach • A–B: Retracting the tubular retractor brings the shaft of the endoscope into contact with the bony edge and allows the blunt dissector to be closer to the lateral wall (blue arrow) • C–D: Given the eccentric working channel, turning the endoscope 180° and facing the bony edge brings the working channel into close proximity to the bony edge Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Interlaminar viewing angle: 15– 25° Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce Transforaminal viewing angle: 25– 30°

Transforaminal endoscope • General characteristics: • 200 mm length approximately 4 mm working channel diameter approximately 4 mm • Viewing angle 25– 30° • Selected indications: • Disc herniations • Foraminal stenosis • Lateral recess stenosis Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce 3. 7

How to handle the transforaminal endoscope • Hold endoscope with pistol grip • Control tubular retractor with index finger Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Interlaminar endoscope • General characteristics: • Approximately 200 mm length • Approximately 4. 5 mm working channel diameter • Viewing angle 15– 25° • Selected indications: • • • Lumbar disc herniations (L 4/5 and L 5/S 1) Lateral recess stenosis Spinal stenosis Facet joint cysts Contralateral foraminotomy Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Central stenosis endoscope • General characteristics: • Approximately 160 mm length • Approximately 6 mm working channel diameter • Viewing angle 15° • Selected indications: • • • Lateral recess stenosis Spinal stenosis Face joint cysts Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

How to handle the interlaminar endoscope • Rest endoscope in the “C” between thumb and index finger • Control tubular retractor with index finger Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce

Challenges and how to avoid and address Topic Common challenge or problem How this can be addressed/avoided 1. Holding the endoscope incorrectly Non-ergonomic position Position it correctly in the hand from beginning and keep doing it 2. Understand Eg, irrigation, light, and troubleshoot the parts of the camera problems endoscope Disassemble the parts—be able to assemble them all 3. Handling the working sleeve (tubular retractor) Retractor in wrong position— bad rotation and depth or endoscope Correct management of rotation and depth 4. No picture visible or field full of blood “I don’t see anything” Maneuvers and hemostasis management—train on simple models with water, etc 5. How to optimize the endoscope Do not just use it like a microscope (when you do not realize what it can do) Realize the full potential (use the depth to move almost anywhere) Authors: Christoph Hofstetter and Jin. Sung Kim, AO Spine MISS Taskforce