Using a burr with an endoscope In minimally invasive spine surgery (MISS) Presenter’s name (Arial 20 pt) Authors: Luke Kim, Christoph Hofstetter Presenter’s title (Arial 20 pt) AOSpine MISS Taskforce (May 2019)

Learning objectives Describe various types of burrs used in full endoscopic spine surgery Identify key differences between use of burrs in microscopic compared with endoscopic spine surgery Explain how to use burrs in full endoscopic surgery Describe strategies for avoiding complications related to burrs

Characteristics of endoscopic burrs Cutting - Pros: allows for aggressive and efficient resection of bone - Cons: difficult to adjust bone removal. Bone bleeding - Best application: foraminoplasty Diamond - Pros: allows for precise and controlled resection of bone. Minimal bleeding. - Cons: tedious - Best application: interlaminar decompression

Burr shape Round Barrel - Pros: efficient resection of bone (high rotational speed at equator) - Cons: difficult to use in tight spaces or next to neural elements - Best application: interlaminar, transforaminal Barrel - Pros: efficient trimming of bony surfaces and edges - Cons: difficult to control in cancellous bone and causes bleeding - Best application: trimming of the SAP, resection of caudal pedicle during posterior cervical foraminotomy

Shield Non-shielded Shielded - Pros: efficient bone resection - Cons: cutting burrs are prone to catch and damage neural elements - Best application: initial decompression for interlaminar, and transforaminal approaches Shielded - Pros: can be safely used next to neural elements - Cons: shield hinders efficient bony decompression - Best application: trimming of bone next to neural elements in interlaminar and transforaminal approaches

Burr drive shaft Straight Articulating - Pros: mechanically solid and durable - Cons: bone resection only in-line with scope - Best application: interlaminar Articulating - Pros: off-axis bone resection - Cons: mechanically complex - Best application: foraminotomy

Handling a burr with an endoscope Endoscopic burr is advanced into operative field via the working channel Off-axis movement (green arrows) is controlled by translating or angulating the tubular retractor and the endoscope - Any forces onto the drill shaft will lead to breakage of the bearings and the shaft In-line movement of the drill is controlled by advancing the drill into the working channel - Stabilizing the tubular retractor helps to achieve precise depth control (crucial when working in the cervical and thoracic spine)

Handling a burr with an endoscope Off-axis movement is controlled by translating and/or angling the tubular retractor together with the endoscope using the non-dominant hand (curved white arrow) In-line movement is controlled by placing a fingertip onto the drill shaft of the drill to prevent non- intentional advance of the instrument (green arrowhead). Advance of the endoscope is controlled using the same technique (red arrowhead). 8

Interlaminar decompression using endoscopic burr Round diamond burr Barrel-shaped cutting burr Bone removal is carried out along the attachment of the yellow ligament. Relatively large amounts of bone need to be resected efficiently. Adequate hemostasis is important.

Interlaminar lateral recess decompression with endoscopic burr Shielded side-biting burr Bone removal is carried out along the medial aspect of the superior articular process. The traversing nerve root is retracted with the shield of the drill.

Transforaminal foraminoplasty with endoscopic burr Articulating cutting burr Bone removal is carried out along the ventral aspect of the superior articular process with the tubular retractor held in position by the facet joint

Videos Video 1. Interlaminar approach endoscopic discectomy Video 2. Percutaneous endoscopic interlaminar decompression

Challenges and how to avoid and address Topic Common challenge or problem How this can be addressed/avoided 1. Plunge Injury to neural or vascular structures Always control drill shaft manually 2. Kick Burr direction and burring sequence 3. Dural laceration Adequate distance and retraction of thecal sac Retract neural elements with tubular retractor. Adequate distance 4. Bone bleeding Bone bleeding adjacent to the facet joint Use diamond burr 5. Endoscope damage Bending of endoscope Contact of burr with optics Avoid lateral forces onto the endoscope Have burr in visual field

Literature Lewandrowski KU. Readmissions after outpatient transforaminal decompression for lumbar foraminal and lateral recess stenosis. Int J Spine Surg. 2018 Aug 15;12(3):342–351. Sairyo K, Chikawa T, Nagamachi A. State-of-the-art transforaminal percutaneous endoscopic lumbar surgery under local anesthesia: discectomy, foraminoplasty, and ventral facetectomy. J Orthop Sci. 2018 Mar;23(2):229–236. Ahn Y, Kim WK, Son S, et al. Radiographic assessment on magnetic resonance imaging after percutaneous endoscopic lumbar foraminotomy. Neurol Med Chir (Tokyo). 2017 Dec 15;57(12):649–657. Lewandrowski KU. "Outside-in" technique, clinical results, and indications with transforaminal lumbar endoscopic surgery: a retrospective study on 220 patients on applied radiographic classification of foraminal spinal stenosis. Int J Spine Surg. 2014 Dec 1;8. Ahn Y, Oh HK, Kim H, et al. Percutaneous endoscopic lumbar foraminotomy: an advanced surgical technique and clinical outcomes. Neurosurgery. 2014 Aug;75(2):124–133; discussion 132–133. Lee SH, Kang HS, Choi G, et al. Foraminoplastic ventral epidural approach for removal of extruded herniated fragment at the L5-S1 level. Neurol Med Chir (Tokyo). 2010;50(12):1074–1078.