Using a microscope In minimally invasive spine surgery

Using a microscope In minimally invasive spine surgery (MISS) Author: Avelino Parajon AO Spine MISS Task Force Version: March 2021

Learning objectives • Identify advantages of using a surgical microscope for minimally invasive spine surgeries • Identify differences between microscopes and loupes • Recognize main characteristics of modern surgical microscopes • Describe how to place a surgical microscope in the OR • Apply basic techniques in the use of surgical microscopes Author: Avelino Parajon, AO Spine MISS Taskforce

History and reasons • House, Kurz, Donaghy, Yasargil, Caspar • • Light Magnification • Teaching, technological, ergonomics, digital documentation Author: Avelino Parajon, AO Spine MISS Taskforce

Magnification and illumination Author: Avelino Parajon, AO Spine MISS Taskforce

Fluorescence Author: Avelino Parajon, AO Spine MISS Taskforce

Fluorescence Author: Avelino Parajon, AO Spine MISS Taskforce

Teaching, co-observation/monitor in 3 -D Author: Avelino Parajon, AO Spine MISS Taskforce

Ergonomics Difficult co-observation Unstable view Cumbersome working postures especially during long surgeries Comfortable upright working position Author: Avelino Parajon, AO Spine MISS Taskforce

Loupes vs microscope • Loupes advantages • Loupes disadvantages • 3 -D vision • Interpupillary distance require longer incisions • Possibility of light • Do not have advanced functionalities: • Possibility of adjusting working distance - Video • Mobility - Pictures - Coaxial lighting - Assistant vision Author: Avelino Parajon, AO Spine MISS Taskforce

Loupes vs microscope 65 mm Incision Author: Avelino Parajon, AO Spine MISS Taskforce 22 mm Incision

Loupes vs microscope • Microscope advantages • Higher magnification and better illumination • Coaxial light • Natural light • Variable zoom and focus - Autofocus Video documentation More ergonomic position Screen—possibility of teaching Author: Avelino Parajon, AO Spine MISS Taskforce

Loupes vs microscope • Coaxial lighting • High contrast in deep fields • Natural light (Xe) paraxial coaxial Author: Avelino Parajon, AO Spine MISS Taskforce

Loupes vs microscope • Fluorescence possibilities of microscope Author: Avelino Parajon, AO Spine MISS Taskforce

Loupes vs microscope • Microscope disadvantages • Limited visual field • Detailed planning of the surgical procedure is needed (as visible field is reduced) • At the beginning of the learning curve, surgeons often have difficulties with hand-eye coordination • Microscope must often be repositioned • Personnel needs training for sterile draping Author: Avelino Parajon, AO Spine MISS Taskforce

Basics of a surgical microscope • • • Eye lens Receives the image and focuses it onto the retina Eyepiece = ocular Magnify the intermediate image and project it onto the exit pupils Binocular tube head Focuses the image information into the intermediate image in each of the optical paths Magnification changer Magnifies or minimizes the image by a given factor Objective lens Projects an image of the object Author: Avelino Parajon, AO Spine MISS Taskforce

Modern spine microscopes • • • Folding binoculars Stereoscopic co-observation Autofocus Long arms High range of field depth Movable arms Author: Avelino Parajon, AO Spine MISS Taskforce

Evolution of binoculars Fixed Tiltable Folding binoculars Author: Avelino Parajon, AO Spine MISS Taskforce

Handling of the surgical microscope Adjustment 1. 2. 3. 4. 5. 6. 7. 8. 9. Turn on the device Release brakes for microscope positioning Fine positioning with the XY-Drive Adjust focus Adjust zoom Increase light intensity Adjustment of binocular tubes Optional fluorescence modes Take pictures/film with integrated camera Author: Avelino Parajon, AO Spine MISS Taskforce of binocular tubes Take pictures or film with integrated camera Fine-positioning with the XY-Drive Adjust focus Adjust zoom Increase /decrease light Intensity Optional fluorescence modes Release brakes for microscope positioning

Handling of the surgical microscope • • • Rebalancing is necessary when the configuration of the microscope is changed Most modern microscopes have autobalance Do not perform autobalance over the patient! Author: Avelino Parajon, AO Spine MISS Taskforce

Adjustment of binocular tubes The correct position has been reached when the two eyepiece images merge into one Author: Avelino Parajon, AO Spine MISS Taskforce

Adjust focus Author: Avelino Parajon, AO Spine MISS Taskforce

Adjust zoom Author: Avelino Parajon, AO Spine MISS Taskforce

Increase light intensity Author: Avelino Parajon, AO Spine MISS Taskforce

Microscope adjustable parameters • • • Medium zoom speed Quick focus speed Submaximal light intensity (surgeon's preference) Not full magnification range (surgeon's preference) Lighting blind opened and adjusted to retractor size Author: Avelino Parajon, AO Spine MISS Taskforce

Optional fluorescence modes Author: Avelino Parajon, AO Spine MISS Taskforce

Go digital: connectivity in the OR, augmented visualization with navigation information Integration of preoperative navigation data into live surgical view for better orientation Author: Avelino Parajon, AO Spine MISS Taskforce

Set-up Author: Avelino Parajon, AO Spine MISS Taskforce

“Visual axis” Author: Avelino Parajon, AO Spine MISS Taskforce

Challenges and how to avoid and address Topic Common challenge or problem How this can be addressed/avoided 1. Suboptimal surgeon ergonomics Poor posture (especially neck) resulting from improper positioning Adjust microscope/OR table to improve surgeon posture 2. Inadequate microscope set-up • • Oculars at different diopters (impairs 3 -D) Scope not balanced Adjust oculars Balance scope before draping 3. Microscope in poor position relative to OR table Interference with access to surgical site or other equipment 4. Compromise of sterile field Touching undraped parts of Proper draping, avoid microscope touching undraped parts 5. Overmagnification or excessive lighting Overmagnification: small field of view with limited depth of field; excessive light impairs contrast Author: Avelino Parajon, AO Spine MISS Taskforce Plan for procedure-specific needs, position scope accordingly Adjust for enough but not too much magnification and illumination

Take-home messages • • 3 -D magnification Coaxial illumination Ergonomic position Short learning curve Reduction of IP distance = smaller incisions Teaching and recording Fluorescence and navigation possibilities Author: Avelino Parajon, AO Spine MISS Taskforce