Vertebral Columns Summer 2021 by International Society for the Advancement of Spine Surgery

INSIDE

The Mazor and ExcelsiusGPS Robotic Systems: A Comparison and Personal Experiences Promise for Intraoperative Ultrasonography Use in Image-Guided Spinal Surgery Venous Thromboembolism in Spine Surgery Regional Anesthesia for Postoperative Pain Control After Spine Surgery

Vertebral

COLUMNS International Society for the Advancement of Spine Surgery

VIRTUAL REALITY

AND ITS ROLE IN TRAINING THE NEXT GENERATION OF SPINE SURGEONS

SUMMER 2021

What’s on the Horizon for Cervical Disc Arthroplasty?

Editor in Chief

3 6 11 15 19 21

Kern Singh, MD

EDITORIAL Virtual Reality and Its Role in Training the Next Generation of Spine Surgeons

MEDICAL DEVICES What’s on the Horizon for Cervical Disc Arthroplasty?

Editorial Board Peter Derman, MD, MBA Brandon Hirsch, MD Sravisht Iyer, MD Yu-Po Lee, MD Sheeraz Qureshi, MD

ROBOTICS The Mazor and ExcelsiusGPS Robotic Systems: A Comparison and Personal Experiences

Managing Editor

INTRAOPERATIVE IMAGING

Designer

Promise for Intraoperative Ultrasonography Use in Image-Guided Spinal Surgery

CavedwellerStudio.com

Audrey Lusher

COMPLICATIONS Venous Thromboembolism in Spine Surgery

PAIN MANAGEMENT Regional Anesthesia for Postoperative Pain Control After Spine Surgery

Become a member today https://www.isass.org/about/membership/

Summer 2021 Vertebral Columns

Vertebral Columns is published quarterly by the International Society for the Advancement of Spine Surgery. ©2021 ISASS. All rights reserved. Opinions of authors and editors do not necessarily reflect positions taken by the Society. This publication is available digitally at www.isass.org/news/vertebralcolumns-Summer-2021

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From the Department of Orthopaedic Surgery at Rush University Medical Center in Chicago, Illinois

EDITORIAL

Virtual Reality and Its Role in Training the Next Generation of Spine Surgeons T he COV ID-19 pa ndem ic u ndoubted ly hampered operative experience for surgical trainees.1 With diminished elective caseloads, redeployment of essential health staff, and reprioritization imposed by public health demands, a comparison of 2019 and 2020 resident case logs showed up to a 50% reduction in operations with trainees as the primary operating surgeon. 2 Residency programs quickly adapted to pandemic-imposed in-person restrictions with increased emphasis on attending-led didactics, e-learning modules, telementoring, and simulation-based learning.1,3 The threat of the pandemic to traditional surgical education, however, gave program directors increased motivation to assess the opportunity to delineate the role of integrating technology into programs moving forward.1 Considering that spine surgery cases comprise roughly 6.2% of all total surgery cases for trainees in an orthopedic surgery residency,4 the goal of our article was to assess promising technological modalities that will play an increasing role in training the next generation of spine surgeons. Often talked about, but yet to be fully explored, virtual reality in spine surgery is still very much in its infancy. Before discussing further, it is important to define virtual reality (VR). In VR, an immersive, interactive environment impression is generated via a

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head-mounted display utilizing a computer three-dimensional image.5-7 The level of immersion is limited by the quality and resolution of the generated image, and authenticity to the user is Kevin C. Jacob, BS limited by haptic feedback.6 I n s p i n e s u r g e r y, s e v e ra l st ud ies on t he use of V R have demonstrated increased three-dimensional anatomic awareness, increased accuracy Madhav R. Patel, BS of cervical and thoracic pedicle screw placement, and improved pedicle screw technique.6-8 Recently, VR application in spine surgery has increasingly shifted to simulation of minimally invasive techniques demonKern Singh, MD strating efficacy in training for both novice and experienced surgeons.7 The application of VR in minimally invasive spine surgery is especially exciting given the degree of technical skill required and variable anatomy seen in spinal cases—sometimes limiting the amount of graded responsibility trainees receive. Two of t he most excit ing benef its afforded by VR applicable not only to spine surgical education but also to procedural proficiency as a whole are the democratization and range it enables. Trainees in an

Vertebral Columns Summer 2021

EDITORIAL

orthopedic residency are at the mercy of two constraints: the ethics of the learning curve and limited supply. As educators, we want to limit the amount of “practice” our trainees conduct on patients, and trainees have limited control over the cases they are exposed to. Immersive VR offers a natural solution to this conundrum, giving educators the ability to assess trainee proficiency as well as trainees’ responsibility over

Summer 2021 Vertebral Columns

case exposure. Additionally, as the pace of technology hastens with a trend toward increasingly complex and minimally invasive procedures, the library of procedural proficiency surgeons are expected to master has exploded. VR offers a solution in this context, as nov ice and expert surgeons alike can attempt a variety of novel and/or complex techniques in a virtual setting, thus helping to broaden their surgical repertoire.

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EDITORIAL

A sample surgical workflow for trainees in the not-so-distant future may see residents and fellows having the ability to perform full or portions of representative cases, with software tracking error/success rates and technical outcomes.7 The ability to increase caseload in an immersive environment with immediate feedback will enable trainees to have autonomy in their progression to increasingly complex cases and enable educators and administrators the potential to aggregate use-case data and to link the data to patient outcome measures. Furthermore, “multiplayer” options will enable attending surgeons to monitor and educate trainees in a virtual operating room setting, thus helping to drive down time and cost while increasing collaboration. Companies currently in the VR space with applications to spine surgery include Fundamental VR, ImmersiveTouch, Precision OS, and Osso VR. FundamentalVR is unique w it h its integ rat ion of high-end hapt ic feedback coupled with machine learning,

As the pace of technology hastens with a trend toward increasingly complex and minimally invasive procedures, the library of procedural proficiency surgeons are expected to master has exploded. and ImmersiveTouch is validating their platform to bring patient-specific anatomy to virtual operating rooms for surgeons to engage with prior to an actual procedure. Precision OS, based out of Vancouver, has recently been integrated into orthopedic residency training at 10 medical institutions in the United States and Canada. As validation continues and the need for adjunct training modalities rises, VR application provides a unique method of increasing spine surgery exposure and competency for residents in orthopedic training. n

References 1. Kogan M, Klein SE, Hannon CP, Nolte MT. Orthopaedic education during the COVID-19 pandemic. J Am Acad Orthop Surg. 2020;28(11):e456-e464. 2. Munro C, Burke J, Allum W, Mortensen N. Covid-19 leaves surgical training in crisis. BMJ. 2021;372:n659. 3. Joos E, Zivkovic I, Shariff F. Virtual learning in global surgery: current strategies and adaptation for the COVID-19 pandemic. IJS Global Health. 2021;4(1):e42.

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4. Pham MH, Jakoi AM, Wali AR, Lenke L. Trends in spine surgery training during neurological and orthopedic surgery residency: a ten-year analysis of ACGME case log data. Neurosurgery. 2019;66(Suppl 1). https://doi.org/10.1093/neuros/nyz310_113 5. Cao C, Cerfolio RJ. Virtual or augmented reality to enhance surgical education and surgical planning. Thorac Surg Clin. 2019;29(3):329-337.

7. Lohre R, Wang JC, Lewandrowski K-U, Goel DP. Virtual reality in spinal endoscopy: a paradigm shift in education to support spine surgeons. J Spine Surg. 2020;6(Suppl 1):S208-S223. 8. Clarke E. Virtual reality simulation— the future of orthopaedic training? A systematic review and narrative analysis. Adv Simul (Lond). 2021;6(1):2.

6. Godzik J, Farber SH, Urakov T, et al. “Disruptive technology” in spine surgery and education: virtual and augmented reality. Oper Neurosurg (Hagerstown). 2021;21(Suppl 1):S85-S93.

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MEDICAL DEVICES

From the Texas Back Institute in Plano, Texas

What’s on the Horizon for Cervical Disc Arthroplasty? Anterior cer v ical discectomy and fusion (ACDF) was first described in 19581 and eventually became the gold standard treatment for cervical radiculopathy and myelopathy. 2,3 While ACDF is safe and effective, concerns Alexander M. Satin, MD regarding pseudoarthrosis and adjacent segment degeneration ex ist. 4,5 Cer v ical disc arthroplasty (CDA) allows for removal of t he degenerat ive disc and neura l decompression whi le maintaining segmental motion, Joseph Albano, DO thus reducing the risk of adjacent segment degeneration requiring surgery compared to fusion.6,7 The first CDA device in the Un ited States received Food and Drug Administration (FDA) approval for single-level use in 2007 after completing prospecPeter B. Derman, MD tive, multicenter, randomized controlled investigational device exemption (IDE) trials. 8-11 Subsequently, eight additional devices have completed single-level FDA IDE trials along with three two-level trials.12-22 The rigorous evaluation of CDA outcomes over the past 2 decades has prov ided t he scientif ic communit y with robust data supporting their use. The FDA IDE trials, now w ith up to 10-year

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follow-up, and subsequent meta-analyses have demonstrated the long-term clinical superiority of modern CDA devices over ACDF for both one- and two-level cervical disease. 23-29 As a result, in appropriate cases, CDA has emerged as the preferred treatment for cervical radiculopathy and/ or myelopathy. Despite the excellent long-term results with first- and second-generation devices, there has been a continued effort by surgeons and industry to introduce novel technology and devices. Since 2019, new CDA devices with unique material and biomechanical properties have received one- and two-level FDA approval. 30-32 To that end, the study of novel CDA devices for the treatment of cervical disc disease is ongoing.

Ongoing IDE Trials ProDisc-C SK and ProDisc-C Vivo (Centinel Spine) The original ProDisc-C FDA IDE trial began enrollment in 2003, and the implant received one-level approval in 2007.11 Two new iterations of the device, the ProDisc-C SK and ProDisc-C Vivo, have been developed. Compared to the original ProDisc-C, the ProDisc-C SK offers a shorter keel on the superior and inferior endplates to allow for easier implantation at multiple levels. The titanium-alloy endplates are trapezoidal in

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MEDICAL DEVICES

shape to maximize endplate coverage and allow for a more anatomic fit in the disc space relative to the uncovertebral joints. The ProDisc-C Vivo eliminates the keeled endplates and instead uses multiple spikes for primary fixation on each endplate. It also features a convex superior endplate for improved fit with the endplate above. Like the SK, it also has trapezoidal endplates to allow for more anatomic fit. Both implants still utilize the original solid, fixed core, ball-in-socket articulation. Enrollment recently began for a two-level FDA trial (SMART) evaluating the ProDisc-C SK and ProDisc-C Vivo. 33 The study design calls for 390 participants to be randomized at a 2:1 ratio comparing study patients (two level ProDisc-C SK or ProDisc-C Vivo) to two-level Mobi-C controls. Patients in this randomized, multicenter trial will be blinded until after surgery. The primary outcome measures are composite clinical success of the two level ProDisc-C SK and ProDisc-C Vivo being non-inferior to the control at 24 months. Two additional ProDisc IDE trials have been registered and are awaiting patient en rol lment. T he f irst is a mu lt icenter, prospective, randomized controlled trial looking at clinical and radiographic outcomes comparing t wo-level ProDisc-C Vivo to a hybrid construct. The hybrid will include a one-level ProDisc-C Vivo and one-level ACDF. 34 The other study is also a multi-center, prospective, randomized controlled trial and will compare clinical and radiographic outcomes of one-level ProDisc-C Vivo to one-level ACDF. 35

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Despite the excellent long-term results with first- and secondgeneration devices, there has been a continued effort by surgeons and industry to introduce novel technology and devices. Baguera-C (Spineart) The Baguera-C is a three-component device that allows for six degrees of freedom. The endplates are made of titanium and coated with a diamond-like composite internally and are porous-coated externally. 36-38 The diamond-like composite coating decreases wear while also having low friction rates, and it is also more magnetic resonance imaging compatible than other titanium implants. 39 The nucleus is a ultrahigh molecular weight polyethylene that allows for 0.15 mm of compression for shock absorption. 36-38 Enrollment for the one- and two-level Baguera-C FDA IDE trials began in March 2021.40,41 The studies are multicenter prospective randomized trials comparing the safety and effectiveness of Baguera-C CDA to a Mobi-C control at one and two levels. The plans are to enroll 270 and 300 participants for the one- and two-level studies, respectively. Patients will be enrolled in a 2:1 ratio of Baguera-C to Mobi-C. The participants will be blinded to their treatment group prior to surgery. The primary outcome measures for the studies will consist of at least 15% Neck Disability Index (NDI) improvement, maintenance or improvement

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MEDICAL DEVICES

in neurologic status, no secondary surgical intervention, and absence of procedure- or device-related serious adverse events. Synergy (Synergy Disc Replacement Ltd) The Synerg y Disc is a three-component device with a ultrahigh molecular weight polyethylene mobile core, allowing for anteroposterior translation and preservation of the physiologic center of rotation.42 Primary fixation is achieved via keels on the superior and inferior endplates. The mobile core is available in 0° or 6° lordotic options.

Recruitment for a one-level FDA trial began in April 2021.43 Investigators are seeking to enroll 190 participants in a multicenter prospective non-randomized study using historical ACDF cont rols. The primar y outcome measures are NDI, neurological assessment maintenance or improvement, avoidance of surgical site infections, and absence of major device-related failures at 24 months. Secondary outcome measures include Health Survey (SF-36) at baseline and up to 24 months, visual analog scale improvement of at least 20 mm, patient

References 1. 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-a(3):607-624. 2. Bohlman H, Emery S, Goodfellow D, Jones P. Robinson anterior cervical discectomy and arthrodesis for cervical. J Bone Joint Surg Am. 1993;75(9):1298-1307. 3. Buttermann GR, Thorson TM, Mullin WJ. Outcomes of posterior facet versus pedicle screw fixation of circumferential fusion: a cohort study. Eur Spine J. 2014;23(2):347-355. 4. Phillips FM, Carlson G, Emery SE, Bohlman HH. Anterior cervical pseudarthrosis: natural history and treatment. Spine. 1997;22(14):1585-1589. 5. Hilibrand AS, Carlson GD, Palumbo MA, Jones PK, Bohlman HH. Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis. J Bone Joint Surg Am. 1999;81(4):519-528. 6. Xie L, Liu M, Ding F, Li P, Ma D. Cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) in symptomatic cervical degenerative disc diseases (CDDDs): an updated meta-analysis of prospective randomized controlled trials (RCTs). SpringerPlus. 2016;5(1):1188. 7. Zhu Y, Zhang B, Liu H, Wu Y, Zhu Q.

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Cervical disc arthroplasty versus anterior cervical discectomy and fusion for incidence of symptomatic adjacent segment disease: a meta-analysis of prospective randomized controlled trials. Spine. 2016;41(19):1493-502. 8. Mummaneni PV, Burkus JK, Haid RW, Traynelis VC, Zdeblick TA. Clinical and radiographic analysis of cervical disc arthroplasty compared with allograft fusion: a randomized controlled clinical trial. J Neurosurg Spine. 2007;6(3):198-209. 9. Murrey D, Janssen M, Delamarter R, et al. Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the ProDisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1-level symptomatic cervical disc disease. Spine J. 2009;9(4):275-286. 10. Tillman D-B. P060018, PRESTIGE Cervical Disc System [letter]. July 16, 2007. https:// www.accessdata.fda.gov/cdrh_docs/pdf6/ P060018A.pdf. Accessed June 13, 2021. 11. Melkerson MN. P070001, ProDisc-C Total Disc Replacement [letter]. December 17, 2007. https://www.accessdata. fda.gov/cdrh_docs/pdf7/P070001A. pdf. Accessed June 13, 2021. 12. Heller JG, Sasso RC, Papadopoulos SM, et al. Comparison of BRYAN cervical disc

arthroplasty with anterior cervical decompression and fusion: clinical and radiographic results of a randomized, controlled, clinical trial. Spine. 2009;34(2):101-107. 13. Phillips FM, Lee JY, Geisler FH, et al. A prospective, randomized, controlled clinical investigation comparing PCM cervical disc arthroplasty with anterior cervical discectomy and fusion: 2-year results from the US FDA IDE clinical trial. Spine. 2013;38(15):E907-E918. 14. Gornet MF, Burkus JK, Shaffrey ME, Argires PJ, Nian H, Harrell FE. Cervical disc arthroplasty with PRESTIGE LP disc versus anterior cervical discectomy and fusion: a prospective, multicenter investigational device exemption study. J Neurosurg Spine. 2015;23(5):558-573. 15. Vaccaro A, Beutler W, Peppelman W, et al. Clinical outcomes with selectively constrained SECURE-C cervical disc arthroplasty: two-year results from a prospective, randomized, controlled, multicenter investigational device exemption study. Spine. 2013;38(26):2227-2239. 16. Hisey MS, Bae HW, Davis R, et al. Multi-center, prospective, randomized, controlled investigational device exemption clinical trial comparing Mobi-C Cervical Artificial Disc to anterior discectomy and fusion in the treatment of symptomatic degenerative disc disease in the cervical spine. Int J Spine Surg. 2014;8:7.

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MEDICAL DEVICES

satisfaction questionnaire, Bazaz Dysphagia Score at 24 months, and Odom’s Criteria at 24 months.

Anticipated IDE Trial Triadyme-C (Dymicron) The Triadyme-C is a two-component device with a trilobed articulation and two keels for provisional fixation. The bearing surface is composed of a polycrystalline diamond (PCD) material which is purported to exhibit lower wear rates and superior structural integrity than other substances

References 17. Phillips FM, Coric D, Sasso R, et al. Prospective, multicenter clinical trial comparing M6-C compressible six degrees of freedom cervical disc with anterior cervical discectomy and fusion for the treatment of single-level degenerative cervical radiculopathy: 2-year results of an FDA investigational device exemption study. Spine J. 2021;21(2):239-252. 18. Coric D, Guyer RD, Carmody CN, et al. Cervical disc replacement using a PEEK-on-ceramic implant: prospective data from seven sites participating in an FDA IDE trial for single-level surgery. Spine J. 2020;20(9):S80. 19. Coric D, Nunley PD, Guyer RD, et al. Prospective, randomized, multicenter study of cervical arthroplasty: 269 patients from the Kineflex C artificial disc investigational device exemption study with a minimum 2-year follow-up. J Neurosurg Spine. 2011;15(4):348-58. 20. Guyer RD, Nunley PD, Strenge KB, Ohnmeiss DD. Two-level cervical disc replacement using a PEEK-on-ceramic device: prospective outcome data from an FDA IDE trial. Spine J. 2020;20(9):S80-S81. 21. Gornet MF, Lanman TH, Burkus JK, et al. Cervical disc arthroplasty with the Prestige LP disc versus anterior cervical discectomy and fusion, at 2 levels: results of a prospective, multicenter randomized controlled clinical trial at 24 months. J

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Neurosurg Spine. 2017;26(6):653-67. 22. Davis RJ, Kim KD, Hisey MS, et al. Cervical total disc replacement with the Mobi-C cervical artificial disc compared with anterior discectomy and fusion for treatment of 2-level symptomatic degenerative disc disease: a prospective, randomized, controlled multicenter clinical trial. J Neurosurg Spine. 2013;19(5):532-45. 23. Lanman TH, Burkus JK, Dryer RG, Gornet MF, McConnell J, Hodges SD. Long-term clinical and radiographic outcomes of the Prestige LP artificial cervical disc replacement at 2 levels: results from a prospective randomized controlled clinical trial. J Neurosurg Spine. 2017;27(1):7-19. 24. Davis RJ, Nunley PD, Kim KD, et al. Two-level total disc replacement with Mobi-C cervical artificial disc versus anterior discectomy and fusion: a prospective, randomized, controlled multicenter clinical trial with 4-year follow-up results. J Neurosurg Spine. 2015;22(1):15-25. 25. Hu Y, Lv G, Ren S, Johansen D. Mid-to long-term outcomes of cervical disc arthroplasty versus anterior cervical discectomy and fusion for treatment of symptomatic cervical disc disease: a systematic review and meta-analysis of eight prospective randomized controlled trials. PLoS One. 2016;11(2):e0149312.

26. Zou S, Gao J, Xu B, Lu X, Han Y, Meng H. Anterior cervical discectomy and fusion (ACDF) versus cervical disc arthroplasty (CDA) for two contiguous levels cervical disc degenerative disease: a meta-analysis of randomized controlled trials. Eur Spine J. 2017;26(4):985-97. 27. Zhang Y, Liang C, Tao Y, Zhou X, Li H, Li F, et al. Cervical total disc replacement is superior to anterior cervical decompression and fusion: a meta-analysis of prospective randomized controlled trials. PLoS One. 2015;10(3):e0117826. 28. McAfee PC, Reah C, Gilder K, Eisermann L, Cunningham B. A meta-analysis of comparative outcomes following cervical arthroplasty or anterior cervical fusion: results from 4 prospective multicenter randomized clinical trials and up to 1226 patients. Spine (Phila Pa 1976). 2012;37(11):943-52. 29. Upadhyaya CD, Wu JC, Trost G, et al. Analysis of the three United States Food and Drug Administration investigational device exemption cervical arthroplasty trials. J Neurosurg Spine. 2012;16(3):216-28. 30. Melkerson MN. P170036, M6-C Artificial Cervical Disc [FDA letter of approval]. Approved Febuary 6, 2019. https://www. accessdata.fda.gov/cdrh_docs/pdf17/ p170036a.pdf. Accessed June 13, 2021.

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used in CDAs. The three convex articulations on the cephalad component have smaller radii than the corresponding three concave pockets inferiorly, producing a design intended to better mimic natural kinematics.44,45 Despite the increased contact stresses imparted by the incongruous articulations, the PCD demonstrates lower wear rates compared to other CDAs. 44 A proposed prospective cohort study w ill consist of 100 patients treated at one and two levels.46

Conclusion Prospective multicenter randomized controlled arthroplast y trials represent the benchmark for device evaluation and the safe introduction of new technology. As we approach the third decade of CDA implantation in the United States, a number of exciting efforts to introduce new biomaterials and designs are underway. Many of the next generation of devices seek to replicate disc kinematics more closely and will hopefully produce even better clinical outcomes. n

References 31. Jean RP. P200022, Simplify Cervical Artificial Disc [FDA letter of approval]. Approved September 18, 2020. https://www. accessdata.fda.gov/cdrh_docs/pdf20/ P200022A.pdf. Accessed June 13, 2021. 32. Jean RP. P200022/S003, Simplify Cervical Artificial Disc [FDA letter of approval]. April 1, 2021. https://www.accessdata. fda.gov/cdrh_docs/pdf20/P200022S003A. pdf. Accessed June 13, 2021. 33. 2-Level cervical disc replacement comparing Prodisc C SK & Vivo to Mobi-C (SMART). ClinicalTrials.gov identifier: NCT04012996. Updated April 29, 2021. Accessed June 15, 2021. https://clinicaltrials.gov/ct2/show/NCT04012996. 34. Clinical and radiological outcomes: two-level cervical ProDisc-C Vivo versus Hybrid construct. ClinicalTrials.gov identifier: NCT03367052. Updated December 8, 2017. Accessed June 15, 2021. https:// clinicaltrials.gov/ct2/show/NCT03367052. 35. A multi-center prospective randomized controlled study on clinical and radiographic analysis of ProDisc-C Vivo. ClinicalTrials.gov identifier: NCT03367039. Updated December 8, 2017. Accessed June 15, 2021. https://clinicaltrials. gov/ct2/show/NCT03367039. 36. Fransen P, Pointillart V. Arthroplasty with the Baguera® C cervical disc prosthesis: a review of the scientific

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background, clinical and radiographic evidences. J Spine Neurosurg. 2016;5(6). 37. Fransen P, Noriega D, Chatzisotiriou A, Pointillart V. One- or two-levels treatment by arthroplasty of cervical degenerative disease: preliminary results after 5 years postoperative controls. J Spine. 2018;7:1. 38. Fransen P, Hansen-Algenstaedt N, Chatzisotiriou A, Noriega DCG, Pointillart V. Clinical results of cervical disc replacement with the Baguera C prosthesis after two years follow-up. Acta Orthopædica Belgica. 2018;84:345-351. 39. Reeks J, Liang H. Materials and their failure mechanisms in total disc replacement. Lubricants. 2015;3(2):346-364. 40. A clinical trial comparing the BAGUERA®C to the marketed Mobi-C® for the treatment of single level cervical disc disease. ClinicalTrials.gov identifier: NCT04520776. Updated July 6, 2021. Accessed August 16, 2021. https://clinicaltrials.gov/ct2/show/NCT04520776. 41. A clinical trial comparing the BAGUERA®C to the marketed Mobi-C® for the treatment of cervical disc disease at 2 contiguous levels. ClinicalTrials.gov identifier: NCT04564885. Updated July 6, 2021. Accessed August 16, 2021. https:// clinicaltrials.gov/ct2/show/NCT04564885.

42. Lazaro BC, Yucesoy K, Yuksel KZ, et al. Effect of arthroplasty design on cervical spine kinematics: analysis of the Bryan Disc, ProDisc-C, and Synergy Disc. Neurosurg Focus. 2010;28(6):E6. 43. The synergy disc to anterior cervical discectomy and fusion. ClinicalTrials.gov identifier: NCT04469231. Updated April 26, 2021. Accessed June 15, 2021. https:// clinicaltrials.gov/ct2/show/NCT04469231. 44. Havey RM, Khayatzadeh S, Voronov LI, et al. Motion response of a polycrystalline diamond adaptive axis of rotation cervical total disc arthroplasty. Clin Biomech (Bristol, Avon). 2019;62:34-41. 45. Patwardhan AG, Havey RM. Biomechanics of cervical disc arthroplasty—a review of concepts and current technology. Int J Spine Surg. 2020;14(s2):S14-S28. 46. Triadyme-C, a polycrystalline diamond compact cervical disc replacement (cTDR). ClinicalTrials.gov identifier: NCT02967575. Updated November 29, 2018. Accessed June 15, 2021. https:// clinicaltrials.gov/ct2/show/NCT02967575.

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ROBOTICS

From the Hospital for Special Surgery in New York, New York

The Mazor and ExcelsiusGPS Robotic Systems: A Comparison and Personal Experiences Overview of Current Robotics Systems Spine surger y is a field that can benefit hugely from robotic assistance, as procedures require precise, repetitive movements during lengthy operations.1-3 Augmented with improved navigation technologies, robotic systems have remarkable potential to improve patient outcomes while limiting complications and costs. Currently, three robotic systems have been approved by the U.S. Food and Drug Administration (FDA) for specific indications in spine surgery, two of the most heavily utilized being the Mazor system (models include Mazor X Stealth Edition, Mazor X, SpineAssist, and Renaissance; Mazor Robotics, Caesareas, Israel) and ExcelsiusGPS (Globus Medical, Audubon, Pennsylvania).1 These platforms use a shared-control system that allows both the surgeon and the robot to concurrently control surgical motions.1,2 The Mazor robotics system, cleared by the FDA for use in spine surgery in 2004, is by far the most-studied robotic-assisted surgical platform. The next generation Mazor Renaissance operates with three different outrigger arms that allow for 6 degrees of freedom in positioning surgical instruments.1,3,5 The device is attached directly to a spinous process in an open surgery, or to a frame triangulated

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by percutaneously placed guide wires for minimally invasive procedures. A preoperative computed tomography (CT) scan is required for constructing the three-dimensional (3D) spinal map and virtual templating and trajectory Sravisht Iyer, MD planning. The templating of desired screw entry point, trajectory, and screw size can be done in the operating room (OR) or preoperatively using the spinal map and transferred to the intraoperative workstation. After the virtual Yeo Eun Kim, MD instrumentation template has been created, a brief verification procedure is performed intraoperatively. This process ensures that the actual implant is less than 1.5-mm deviated from the preoperative template. Once the software determines the optimal screw trajectory, a cortical punch is drilled at the desired entry point, and a guide wire is inserted into the vertebral body to assist the drilling of a screw pilot hole. The surgeon then inserts the appropriate screw into the pilot hole. The most recent model, Mazor X, integrates both intraoperative fluoroscopy and 3D surface scanning, but it still requires fixation to the operative bed and bone mounting to the patient.1-4

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ROBOTICS

The ExcelsiusGPS system, approved by the FDA in 2017, is the latest addition to robotic spine surgery and addresses several drawbacks of previous robotic systems.1,6,7 This device operates with a highly rigid robotic arm with 6 degrees of freedom fixed to a floor unit. Unlike the Mazor system, trajectory planning can be performed with preoperative or intraoperative imaging, including both f luoroscopy and CT, which allows for real-time intraoperative navigation for instrumentation placement and enhanced imaging versatility. Its rigid external arm facilitates direct transpedicular drilling and screw placement without the need for Kirschner wires. This functionality allows for potential adaptation of additional tools to be mounted to the robotic arm and eliminates the dependence on patient-mounted frames and K-wires, which is a major drawback associated w ith the Mazor system

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and is often associated with unnecessary neurovascular injuries. The ExcelsiusGPS system has integrated neuronavigation, which is not included in the Mazor system. It also utilizes a surveillance marker to detect registration loss and a lateral force meter to identify skiving.1,7 Several randomized controlled trials have validated the accuracy of these robotic systems. In 2012, Ringel et al8 evaluated 60 patients who received 298 pedicle screws and found t hat Mazor SpineAssist was associated with reduced screw placement accuracy compared to the freehand group. The diminished accuracy was attributed to bone mount movement due to insufficient fixation and dislocation of the implantation cannula causing lateral deviation of screws.8 Another similarly designed study by Hyun et al9 examined the accuracy of the Mazor Renaissance model. Results showed that the

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ROBOTICS

robotic-assisted group achieved an accuracy rate of 100% (130 pedicle screws placed in 30 patients) compared to 98.6% in the freehand group (140 screws placed in 30 patients). Although no prospective randomized controlled trials of the ExcelsiusGPS system have been reported, initial case reports suggest high accuracy and safety with rates on par with those of other robotic systems.1,7,10 After measuring the actual screw placement to the preplanned trajectory, Jiang et al10 found that the mean screw tip deviation was 2.1 mm and the mean tail deviation was 3.2 mm. These results were comparable to what Devito et al reported in their analysis of planned versus actual placements of 646 screws using the Mazor SpineAssist system.10,11

Our Personal Experience In clinical practice, both systems offer a similar end result through vastly different approaches. Both systems allow for intraoperative 3D image acquisition and templating and/or the ability to template based on preoperative CT images. Similarly, both systems allow for “segmental” registration, which is important in multistage procedures (ie, posterior screws placed after anterior cages). The benefits of a preoperative CT scan are the ability to pre-plan screws (saves time and is helpful in multilevel cases to ensure trajectories that allow for easy rod passage), whereas the benefit of an intraoperative spin is theoretically increased accuracy compared to a “merged” registration. There are, however, subtle differences between the robotic systems that make them uniquely suited to certain case types. Both

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The introduction of robotics to spine surgery has allowed surgeons to more quickly adopt novel techniques. More than just “placing screws,” the current generation of robotics serves as a navigation platform that enables surgeons to adapt novel procedures more easily and safely systems work well for single-level posterior cases, such as transforaminal lumbar interbody fusions. In their latest iteration, both systems also allow for robust navigation of interbody instruments and implant placement. The Mazor system is a more “closed” ecosystem in that it is only compatible with an O-arm for 3D image acquisition, whereas Excelsius is capable of work ing w ith third-party imaging solutions (eg, Ziehm or Aero). For most single-position applications, the freestanding nature of the Excelsius (vs the tablemounted Mazor) allows for increased flexibility. The Excelsius allows for multilevel single position constructs including placement of iliac fixation in the lateral position. Furthermore, the interbody navigation capabilities and the “modular” robotic arm allow surgeons to incorporate the robot into their lateral approaches. This modularity is also helpful as surgeons adopt prone-lateral techniques; the robot can move seamlessly from posterior screw and interbody placement to lateral navigation and retraction.

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Conversely, the Mazor system has a robust segmentation and registration system. When performing “multi-step” procedures (eg, anterior lumbar interbody fusion, lateral lumbar interbody fusion, and posterior fixation), the Mazor is frequently quicker to recognize the angular change within the disc and more seamlessly merge with a preoperative CT image. The software algorithm frequently allows for this merge across multiple segments using a single anteroposterior and lateral x-ray image. This allows for quicker registration and screw placement compared to the Excelsius. Note that these types of cases (multilevel, complex procedures) benefit the most from planning on a preoperative CT, which makes intraoperative CT a relatively less attractive alternative. Furthermore, the latest iteration of the Mazor has been merged with the Medtronic burr (Midas Rex); this allows for a high-speed, high-torque intro-

duction to the pedicle, which minimizes the risk of skiving.

Conclusion The introduction of robotics to spine surgery has allowed surgeons to more quickly adopt novel techniques. More than just “placing screws,” the current generation of robotics serves as a navigation platform that enables surgeons to adapt novel procedures more easily and safely (eg, prone lateral, single position surgery). The two most widely utilized robotics systems (Mazor X and ExcelsiusGPS) offer largely similar capabilities; however, the robots have been developed with different approaches. Given the large capital expenditure required to acquire these systems, interested surgeons and hospital systems might find it helpful to consider their strengths and weaknesses in the context of their own practices. n

References 1. Vo CD, Jiang B, Azad TD, Crawford NR, Bydon A, Theodore N. Robotic spine surgery: current state in minimally invasive surgery. Global Spine J. 2020;10(2 suppl):34S-40S. 2. Roser F, Tatagiba M, Maier G. Spinal robotics: current applications and future perspectives. Neurosurgery. 2013;72(suppl 1):A12-A18. 3. Louw DF, Fielding T, McBeth PB, Gregoris D, Newhook P, Sutherland GR. Surgical robotics: a review and neurosurgical prototype development. Neurosurgery. 2004;54(3):525-536; discussion 536-7. 4. Overley SC, Cho SK, Mehta AI, Arnold PM. Navigation and robotics in spinal surgery: where are we now? Neurosurgery. 2017;80(3S):S86-S99.

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5. Khan A, Meyers JE, Siasios I, Pollina J. Next-generation robotic spine surgery: first report on feasibility, safety, and learning curve. Oper Neurosurg (Hagerstown). 2019;17(1):61-69. 6. Zygourakis CC, Ahmed AK, Kalb S, et al. Technique: open lumbar decompression and fusion with the Excelsius GPS robot. Neurosurg Focus. 2018;45(video suppl 1):V6. 7. Ahmed AK, Zygourakis CC, Kalb S, et al. First spine surgery utilizing real-time image-guided robotic assistance. Comput Assist Surg (Abingdon). 2019;24(1):13-17.

9. Hyun SJ, Kim KJ, Jahng TA, Kim HJ. Minimally invasive robotic versus open fluoroscopic-guided spinal instrumented fusions. Spine (Phila Pa 1976). 2017;42(6):353-358. 10. Jiang B, Ahmed AK, Zygourakis CC, et al. Pedicle screw accuracy assessment in ExcelsiusGPS® robotic spine surgery: evaluation of deviation from pre-planned trajectory. Chin Neurosurg J. 2018;4:23. 11. Devito DP, Kaplan L, Dietl R, et al. Clinical acceptance and accuracy assessment of spinal implants guided with SpineAssist surgical robot: retrospective study. Spine (Phila Pa 1976). 2010;35(24):2109-2115.

8. Ringel F, Stüer C, Reinke A, et al. Accuracy of robot-assisted placement of lumbar and sacral pedicle screws: a prospective randomized comparison to conventional freehand screw implantation. Spine (Phila Pa 1976). 2012;37(8):E496-E501.

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From the Department of Orthopaedic Surgery at Rush University Medical Center in Chicago, Illinois

INTRAOPERATIVE IMAGING

Promise for Intraoperative Ultrasonography Use in ImageGuided Spinal Surgery Image-guided surgical techniques have exponentially increased over the past decade in large part due to improvements in spinal technology and the ability to move imaging into the operating room. Modalities such as f luoroscopy, magnetic resonance imaging, and ultrasonography have improved treatment-related parameters and clinical outcomes. The increased use of patient-reported outcomes to determine “success” in spinal surgical procedures will require surgeons to explore new ways to decrease operative time through increased utilization of minimally invasive procedures, which shorten recovery time and ensure quicker return to health for patients after surgery. A possible means of achieving these goals will be incorporating intraoperative ultrasonography as a surgeon’s go-to tool. Oncological surgery, for example, is a spine discipline that has utilized intraoperative ultrasonography extensively. Surgery is the standard treatment for spinal tumors. However, this treatment can result in significant impairment of the nervous system. Many patients who undergo intradural tumor inter-

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ventions suffer neurological damage after their surgery. Iatrogenic trauma during tumor intervention can even lead to complications of vascular impairment, cerebrospinal fluid leakage, or contamination. Recent literature has further shown the utility of intraoperative ultrasonography in mitigating such challenges in oncology surgical interventions. Mitigating iatrogenic surgical complications presents an excellent area of focus for increasing the use of intraoperative ultrasonography in other surgical fields, particularly those rapidly transitioning to minimally invasive procedures that carry a high risk of severe complications, such as orthopedic spine surgeries. In the following paragraphs, we identify areas where intraoperative ultrasonography has improved various dimensions of surgery in orthopedic and neurosurgical spinal practice.

Anatomical and Neurovascular Identification Surgical techniques have advanced with intraoperative computed tomography (CT), magnetic resonance imaging (MRI), and fluoroscopy, leading to clin-

Madhav R. Patel, BS

Kevin C. Jacob, BS

Alexander W. Parsons, MS

Kern Singh, MD

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ically significant improvements such as lower reoperation rates and decreased postoperative length of stay after surgery.1 Professionals in the surgical community have welcomed the advantages of improved imaging; however, radiation exposure is a serious concern for both patients and surgeons.1 It has been shown that various intraoperative ultrasonography techniques can help minimize the risk of iatrogenic vascular injury, which can be a potentially deadly consequence of spinal surgeries, highlighting the importance of identifying anatomical structures that need to be avoided.2-4 Furthermore, those undergoing spinal surgeries are significantly more likely to suffer permanent disabling nerve damage than those undergoing nonspinal procedures.5 During lateral fusion procedures, intraoperative ultrasonography has been shown to prevent damage to vertebral and lumbar arteries by allowing improved visualization for the surgical team and decreasing iatrogenic harm.6 Further advancements in ultrasonography software technology now allow specific identification of nerves and arteries by highlighting these structures on screens in the operating room.6 These software advancements for identifying anatomical landmarks have become so precise that several studies reported near-perfect structure identification.7-9 W hile ultrasonography use in various medical fields has been applied for decades, integrating ultrasonography with artificial intelligence (AI) navigation to identify neural structures in the operative field is currently being explored and could turn into the future use of intraoperative ultrasonography.10 For

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instance, machine learning applied by SonoVision™ Tissue Differentiation Intelligence has demonstrated promise in combining AI with intraoperative ultrasonography for infield localization of neural elements, bony landmarks, muscle, and the intervertebral disc spaces.10 This intraoperative technology has also been shown to accurately identify vascular structures using Doppler color mode, which may help prevent adverse patient outcomes and resulting expenditures.10

Tumor Excision In addition to assisting surgeons in navigating a minimally invasive surgical field locating critical structures, intraoperative ultrasonography is also used to help guide the intricacies of tumor excision. The delineation between healthy tissue and tumor tissue can define success in oncological procedures.11 Numerous articles have examined intraoperative ultrasonography for the excision of various tumors, including pilocytic astrocytomas, anaplastic astrocytomas, glioblastomas, subependymomas, ependymomas, hemangioblastomas, neurocytomas, and post-traumatic cysts.12 Studies have reported high success rates in identifying tumors and, more importantly, distinguishing the surgical borders between healthy tissue and that of the tumor, confirming its efficacy.11,13 Furthermore, tumor resection is complicated by those with highly intricate vascular networks in the surgical field; however, current ultrasonography techniques allow surgeons to identify and ligate the vascular supply without image distortion, showing how ultrasonography can be applied effectively.12

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Intraoperative ultrasonography has consistently proven its utility as an economical and practical tool, but more recent data expand upon its capabilities, contributing to surgical workflow and success with its procedural use in spinal oncological intervention.

Pedicle Screw Placement With Navigation In addition to improving visualization and understanding of a patient’s anatomy, intraoperative ultrasonography can assist in providing precise pedicle screw placement. Using ultrasonography modalities during screw insertion offers high efficacy and accuracy, suggesting its use could significantly reduce postoperative complications seconda r y to ped icle ma lposit ion i ng. Innovations in spinal navigation technologies allow for capturing and mapping preoperative computed tomographic (CT) images and using them for intraoperative ultrasonographic-CT registration. Spinal navigation shows promise to expedite the pace of spinal fusion procedures that require pedicle screws.14 Despite numerous constraints, surgeons still rely on outdated, slow imaging modalities associated with increased radiation ex posure. 15 Not w it hstanding its st rong connection to past imaging modalities, spinal navigation technology may be the tool that pushes surgeons away from this habit. Nav igat ion technolog y creates a t hree-dimensional scan specif ic to t he patient, significantly improving treatments tailored to a patient’s particular needs.16 Spinal nav igation technolog y has been

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regularly used among anesthesiologists for anatomic and neurovascular localization for injections with excellent precision. While the use of navigation and intraoperative ultrasonography in spine surgery may be on the cusp of broader acceptance, specific clinical research teams have incorporated it in practice, as demonstrated by Helm et al,17 who reported that more than 12,000 pedicle screws were placed with a success rate of nearly 97%. Wit h cur rent literat ure repor t ing intraoperative ultrasonography having an acceptable efficacy and safety profile and no additional adverse influence on fusion rate, functional recovery, or infection risk, it may only be a matter of time before its use in pedicle insertion exponentially increases.18-20

Trauma and Fracture Fixation The field of spinal trauma has also benefited from intraoperative ultrasonography’s ability to provide immediate, real-time monitoring of surgical procedures. Specifically, Doppler ultrasonography has show n promise in techniques correcting thoracolumbar vertebral fractures with high success rates in identifying anatomical landmarks along with excellent generalizability and simplicity. 2,21 Additionally, intraoperative ultrasonography has been used in burst fracture management to help locate vertebral body fragments, check for additional hemorrhaging and iatrogenic bleeds, and confirm proper completion of the fixation procedure. 2 Aforementioned studies demonstrate promise for intraoperative ultrasonography in emergent trauma cases.

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Conclusion As an attractive alternative to intraoperative CT- or MRI-guided navigation, intraoperative ultrasonography has been shown to minimize radiation exposure, decrease iatrogenic organ damage, decrease costs, and demonstrate the potential to improve intraoperative treatment parameters and clinically significant out-

comes. Further literature on its application in varying spinal disciplines is warranted to increase the volume of data supporting its operative use. Meanwhile, current findings should encourage spinal surgeons to utilize intraoperative ultrasonography for a smoother and safer surgical workflow with the promise of improved operative and patient outcomes. n

References 1. Xiao R, Miller JA, Sabharwal NC, et al. Clinical outcomes following spinal fusion using an intraoperative computed tomographic 3D imaging system. J Neurosurg Spine. 2017;26(5):628-637.

8. Ungi T, Moult E, Schwab JH, Fichtinger G. Tracked ultrasound snapshots in percutaneous pedicle screw placement navigation: a feasibility study. Clin Orthop Relat Res. 2013;471(12):4047-4055.

15. Lener S, Wipplinger C, Hernandez RN, et al. Defining the MIS-TLIF: a systematic review of techniques and technologies used by surgeons worldwide. Global Spine J. 2020;10(2 Suppl):151S-167S.

2. Lofrese G, Cultrera F, Visani J, et al. Intraoperative Doppler ultrasound as a means of preventing vertebral artery injury during Goel and Harms C1-C2 posterior arthrodesis: technical note. J Neurosurg Spine. 2019:1-7.

9. Han B, Wu D, Jia W, Lin S, Xu Y. Intraoperative ultrasound and contrast-enhanced ultrasound in surgical treatment of intramedullary spinal tumors. World Neurosurg. 2020;137:e570-e576.

16. Shin BJ, James AR, Njoku IU, Härtl R. Pedicle screw navigation: a systematic review and meta-analysis of perforation risk for computer-navigated versus freehand insertion. J Neurosurg Spine. 2012;17(2):113-122.

3. Liu L, Li N, Wang Q, et al. Iatrogenic lumbar artery injury in spine surgery: a literature review. World Neurosurg. 2019;122:266-271. 4. Jiang J, Qian B-P, Qiu Y, Wang B, Yu Y, Zhu Z-Z. The potential risk of left subclavian artery injury from excessively long thoracic pedicle screws placed in the proximal thoracic regions of Lenke type 2 adolescent idiopathic scoliosis patients and normal teenagers: an anatomical study. Eur Spine J. 2016;25(10):3282-3287. 5. Kutteruf R, Wells D, Stephens L, Posner KL, Lee LA, Domino KB. Injury and liability associated with spine surgery. J Neurosurg Anesthesiol. 2018;30(2):156-162. 6. Nojiri H, Miyagawa K, Yamaguchi H, et al. Intraoperative ultrasound visualization of paravertebral anatomy in the retroperitoneal space during lateral lumbar spine surgery. J Neurosurg Spine. 2019;31(3):334-337. 7. Ivanov M, Budu A, Sims-Williams H, Poeata I. Using intraoperative ultrasonography for spinal cord tumor surgery. World Neurosurg. 2017;97:104-111.

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10. Carson T, Ghoshal G, Cornwall GB, Tobias R, Schwartz DG, Foley KT. Artificial intelligence-enabled, real-time intraoperative ultrasound imaging of neural structures within the psoas: validation in a porcine spine model. Spine. 2021;46(3):E146-E152. 11. Velho V, Kharosekar HU, Bhople L, Domkundwar S. Intraoperative ultrasound an economical tool for neurosurgeons: a single-center experience. Asian J Neurosurg. 2020;15(4):983-988. 12. Vetrano IG, Gennari AG, Erbetta A, et al. Contrast-enhanced ultrasound assisted surgery of intramedullary spinal cord tumors: analysis of technical benefits and intra-operative microbubble distribution characteristics. Ultrasound Med Biol. 2021;47(3):398-407. https://doi. org/10.1016/j.ultrasmedbio.2020.10.017 13. Moiyadi A, Shetty P. Objective assessment of utility of intraoperative ultrasound in resection of central nervous system tumors: a cost-effective tool for intraoperative navigation in neurosurgery. J Neurosci Rural Pract. 2011;02(01):004-011. https://doi.org/10.4103/0976-3147.80077 14. Drouin S, Kochanowska A, Kersten-Oertel M, et al. IBIS: an OR ready opensource platform for image-guided neurosurgery. Int J Comput Assist Radiol Surg. 2017;12(3):363-378.

17. Helm PA, Teichman R, Hartmann SL, Simon D. Spinal navigation and imaging: history, trends, and future. IEEE Trans Med Imaging. 2015;34(8):1738-1746. 18. Chen MJ-W, Niu C-C, Hsieh M-K, et al. Minimally invasive transforaminal lumbar interbody debridement and fusion with percutaneous pedicle screw instrumentation for spondylodiscitis. World Neurosurg. 2019;128:e744-e751. 19. Nakamura S, Ito F, Ito Z, Shibayama M. Methods and early clinical results of percutaneous lumbar interbody fusion. Neurospine. 2020;17(4):910-920. 20. Z hao Y, Yuan S, Tian Y, Liu X. Risk factors related to superior facet joint violation during lumbar percutaneous pedicle screw placement in minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF). World Neurosurg. 2020;139:e716-e723. https:// doi.org/10.1016/j.wneu.2020.04.118 21. Degreif J, Wenda K. Ultrasound-guided spinal fracture repositioning. Surg Endosc. 1998;12(2):164-169.

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From UCI Health in Orange County, California

COMPLICATIONS

Venous Thromboembolism in Spine Surgery Venous thromboembolism (VTE) is an uncommon complication of spine surgery but may lead to lethal complications such as pulmonary embolism (PE). VTE has been known to be associated with advanced age, smoking, obesity, major surgery, hospitalization, immobilization, neurological deficit, blood transfusion, malignancy, trauma, inherited hypercoagulable state, and oral contraceptive use.1 Approximately 15% of patients undergoing posterior spinal surgery develop a deep venous thrombosis (DVT).2 Most existing literature and international guidelines on DVT management emphasize that prevention is more important and cost-effective than treatment. DVT prophylaxis is primarily divided into two categories: mechanical and pharmacological prophylaxis. Compression stockings and pneumatic compression devices have been proven effective and are thus routinely used for mechanical prophylaxis. Epstein et al3 found that pneumatic compression stockings reduced the

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incidence of DVT (2.8%) and PE (0.7%) in a cohort of 139 patients undergoing multilevel lumbar laminectomies with instrumented fusions. The authors concluded that these complication rates Yu-Po Lee, MD compared favorably with those reported in other studies evaluating low dose heparin prophylaxis. Early mobilization and physical therapy should also be encouraged after spine surgery. This not only reduces the risk of DVT and pneumonia but also—importantly—postoperative hospital length of stay. However, most patients tend to stay in bed due to the pain from the procedure. As spine patients also tend to be older with other medical comorbidities, early mobilization is further hindered. If patients are unable to physically mobilize out of bed, they should be encouraged to partake in lower-limb exercise in bed to prevent lower extremity venous stasis and improve vascular circulation. There are limited data on when therapeutic pharmacologic anticoagulation can be safely initiated after spine surgery. Thus, there is no consensus on its role after degenerative spine surgery. McLynn et al4 evaluated the effectiveness of pharmacologic prophylaxis after spine surgery. The authors queried the NSQIP database and found 109,609 elective spine surgery patients. They compared this cohort

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to 2,855 patients from their own institution. Pharmacologic prophylaxis was performed in 56.3% of their patients, of whom 97.1% received unfractionated heparin. W hen controlling for patient and procedural variables, pharmacologic prophylaxis did not significantly influence the rate of VTE, but it was associated with a significant increase in hematoma requiring a return to the operating room (relative risk = 7.37, P = 0.048).4 A spinal epidural hematoma can have profound neurological consequences, so these authors advocated against pharmacological prophylaxis for routine spine surgery.4 In another study evaluating prophylactic chemoprophylaxis with low molecular weight heparin (LMWH) after spine surgery, Shapiro et al5 included 266 patients, of whom 79.3% were given mechanical prophylaxis alone and 20.7% were provided combined mechanical and chemical prophylaxis. Complications such as VTE (0.38%), delayed wound healing or infection (2.26%), and hematoma (0.75%) were comparable to those of similar existing studies, but the use of chemoprophylaxis and

continuation of perioperative aspirin were significantly associated with the development of a hemorrhagic complication. 5 However, Strom et al6 found that no patients receiving LMWH 24 to 36 hours after surgery developed postoperative hemorrhage. So what should spine providers do if their patients develop a DVT or PE? Cain et al7 evaluated the morbidity of heparin therapy after patients developed a PE by polling the members of the Scoliosis Research Society on their incidences of PE. Of the 9 patients who fit the inclusion criteria of this study, 6 (67%) had complications attributable to heparinization. Clinically significant complications of filter placement ranged from 0.12% to 10.1%. The authors thus concluded that heparinization after the development of pulmonary embolus in patients recently undergoing spinal fusion is associated with a high complication rate. The morbidity of vena cava filter placement was lower and thus should be considered as an alternative treatment option for pulmonary embolus after spinal surgery. n

References 1. Anderson FA Jr, Wheeler HB, Goldberg RJ, et al. A population-based perspective of the hospital incidence and case-fatality rates of deep vein thrombosis and pulmonary embolism. The Worcester DVT Study. Arch Intern Med. 1991;151(5):933-938. 2. Oda T, Fuji T, Kato Y, Fujita S, Kanemitsu N. Deep venous thrombosis after posterior spinal surgery. Spine (Phila Pa 1976). 2000;25(22):2962-2967. 3. Epstein NE. Efficacy of pneumatic compression stocking prophylaxis in the prevention of deep venous thrombosis and pulmonary embolism following 139 lumbar laminectomies with instrumented fusions. J Spinal Disord Tech. 2006;19(1):28-31.

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4. McLynn RP, Diaz-Collado PJ, Ottesen TD, et al. Risk factors and pharmacologic prophylaxis for venous thromboembolism in elective spine surgery. Spine J. 2018;18(6):970-978. 5. Shapiro JA, Stillwagon MR, Padovano AG, Moll S, Lim MR. An evidence-based algorithm for determining venous thromboembolism prophylaxis after degenerative spinal surgery. Int J Spine Surg. 2020;14(4):599-606.

6. Strom RG, Frempong-Boadu AK. Low-molecular-weight heparin prophylaxis 24 to 36 hours after degenerative spine surgery: risk of hemorrhage and venous thromboembolism. Spine (Phila Pa 1976). 2013;38(23):E1498-E1502. 7. Cain JE Jr, Major MR, Lauerman WC, West JL, Wood KB, Fueredi GA. The morbidity of heparin therapy after development of pulmonary embolus in patients undergoing thoracolumbar or lumbar spinal fusion. Spine (Phila Pa 1976). 1995;20(14):1600-1603.

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From The Core Institute in Mesa, Arizona

PAIN MANAGEMENT

Regional Anesthesia for Postoperative Pain Control After Spine Surgery The management of postoperative pain is an important determinant of short-term clinical outcomes after spine surgery. Advances in “enhanced-recovery” or “multimodal” analgesic regimens have significantly improved postoperative pain control while reducing the need for opioid pain medication. The majority of these advances involve the perioperative use of non-opioid medications such as acetaminophen, muscle relaxants, ketamine, lidocaine, and gabapentinoids. While this approach has been highly effective at reducing opioid intake and its associated side effects, the majority of spine surgery is still performed under a general anesthetic. As the concept of opioid-sparing pain management continues to evolve, alternatives to the use of general anesthesia have become of great interest. While regional anesthetic blocks have dramatically improved perioperative pain management in extremity surgery for quite some time, they are just now gaining popularity in spine surgery.1 The erector spinae plane block (ESPB) is a paravertebral interfascial plane block that targets the dorsal and ventral rami of spinal nerves at the junction of the erector spinae fascia and transverse process. 2 This block is typically performed under ultrasound guidance with a 21G needle. W hen per-

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formed correctly, the injectate should form a dark line dorsal to the transverse process and ventral to t he erector spinae fascia. Most published reports use 20 mL of either bupivacaine or ropivacaine in varying conBrandon P. Hirsch, MD centrations from 0.25-0.5%.2 The ESPB was originally described for treating chest wall pain related to shingles and chest wall trauma. 3 Subsequent work has shown excellent efficacy in reducing pain scores and opioid consumption in breast and abdominal surgery.4-6 Its use for pain management after thoracolumbar surgery was initially described by Ueshima and Otake in 2017.7 Since that time, 12 randomized controlled trials have studied ESPB in posterior lumbar surgery with instrumented fusion. A 2021 meta-analysis of these studies demonstrated substantial reduction in opioid intake and postoperative nausea/vomiting during the first 24 hours postoperatively. 2 In this meta-analysis, adverse events were limited to a lack of sensory blockade in 4 patients in a single study. Overall, the ESPB technique appears to be highly effective at reducing pain, opioid requirement, and opioid-related adverse effects during the first 24 hours after lumbar spine surgery.

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The thoracolumbar interfascial plane block (TLIPB) was originally described by Hand et al8 in 2015 as an alternative to ESPB. The proposed benefit over ESPB is a more superficial location, which is purported to reduce the likelihood of inadvertent neurological injury, dural puncture, and hematoma. The more dorsal location of the block also excludes involvement of the ventral rami that is sometimes seen in ESPB. Two techniques for TLIPB exist. The classic approach described by Hand et al8 places local anesthetic in the interfascial plane between the multifidus and longissimus muscles, with the needle directed in a lateral to medial trajectory. The modified approach places the needle in between the longissimus and iliocostalis muscles via a medial to lateral trajectory. 9 Both approaches target the dorsal rami of spinal nerve roots. A 2021 meta-analysis by Ye et al10 aggregated the results of 9 randomized controlled trials evaluating TLIPB in lumbar surgery. Overall, the technique was effective in reducing opioid consumption, pain scores, and opioid related adverse events during the first 24 hours after surgery. No block-related adverse events were reported in any study. Nearly all of the published studies used 20 mL of 0.25% bupivacaine per side. A recent head-to-head randomized trial11 compared ESPB to TLIPB in patients undergoing lumbar discectomy. Ninety patients were randomized to ESPB, TLIPB, or a control group receiving no block. As expected, both block groups had significant reductions in opioid consumption, pain scores, and opioid-related side effects when compared to controls. No significant differences in any outcome were

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noted between the ESPB and TLIPB groups. There were no block-related complications in the study either. The transversus abdominis plane (TAP) block is used to anesthetize the anterior and lateral abdominal wall. It was originally described as an abdominal field block using superficial landmark techniques in 2001.12 The needle is delivered through the triangle formed by the iliac crest, latissimus dorsi, and the external oblique and placed in the interfascial plane between the internal oblique and transversus abdominis. This technique targets the terminal branches of the lower thoracic and L1 nerve roots, which supply the anterior and lateral abdominal wall. Today, TAP blocks performed with ultrasound guidance have gained widespread use for abdominal and gynecological procedures.13 Despite their widespread use in abdominal surgery, there is limited literature on their use in anterior and lateral approaches to the spine. Only one retrospective series has been published on the use of TAP blocks in anterior and lateral lumbar interbody fusion.14 The study evaluated 250 patients undergoing anterior-only lumbar fusion via either a lateral or direct anterior approach. The cohorts received a multimodal analgesia regimen and comprised 129 patients receiving a TAP block and 121 patients treated without a TAP block. Decision-making regarding TAP block use was related to surgeon and anesthesiologist preference and patient cooperation. TAP blocks were performed with 20 to 30 mL of 0.5% bupivicane prior to incision. Small but statistically significant reductions were observed in length of stay (50 vs 54 hours, P =

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0.003) and opioid consumption in the recovery unit (17 vs 21 morphine milliquivalents, P = 0.012). The incidence of nausea/vomiting was significantly lower in patients receiving a TAP block (3% vs. 12%; P = 0.007). Further study of the efficacy of TAP blocks in anterior and lateral lumbar surgery is anticipated. Regional anesthesia techniques have significant potential to reduce opioid consumption and its related adverse effects following spine surgery. While the efficacy of posteriorly based techniques (TLIPB, ESPB) is well established, TAP blocks remain understudied in spine surgery. With the continued transition toward an older patient population and outpatient postoperative recovery, it will be important that spine surgeons become familiar with

the technical aspects and workflow related to ultrasound-guided fascial plane blocks. As familiarity with regional techniques becomes more commonplace, we may be able to join our counterparts in extremity surgery in moving away from use of routine general anesthetic. n

References 1. Garg B, Ahuja K, Khanna P, Sharan AD. Regional anesthesia for spine surgery [published online ahead of print]. Clin Spine Surg. https://doi. org/10.1097/BSD.0000000000001096 2. Ma J, Bi Y, Zhang Y, et al. Erector spinae plane block for postoperative analgesia in spine surgery: a systematic review and meta-analysis [published online ahead of print]. Eur Spine J. https://doi. org/10.1007/s00586-021-06853-w 3. Forero M, Adhikary SD, Lopez H, Tsui C, Chin KJ. The erector spinae plane block a novel analgesic technique in thoracic neuropathic pain. Reg Anesth Pain Med. 2016;41(5):621-627. 4. Gürkan Y, Aksu C, Kuş A, Yörükoğlu UH, Kılıç CT. Ultrasound guided erector spinae plane block reduces postoperative opioid consumption following breast surgery: a randomized controlled study. J Clin Anesth. 2018;50:65-68. 5. Chin KJ, Malhas L, Perlas A. The erector spinae plane block provides visceral abdominal analgesia in bariatric surgery: a report of 3 cases. Reg Anesth Pain Med. 2017;42(3):372-376.

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6. Altıparmak B, Toker KM, Uysal AI, Kuşçu Y, Demirbilek SG. Ultrasound-guided erector spinae plane block versus oblique subcostal transversus abdominis plane block for postoperative analgesia of adult patients undergoing laparoscopic cholecystectomy: randomized, controlled trial. J Clin Anesth. 2019;57:31-36. 7. Ueshima H, Otake Hop. Clinical experiences of ultrasound-guided erector spinae plane block for thoracic vertebra surgery. J Clin Anesth. 2017;38:137. 8. Hand WR, Taylor JM, Harvey NR, et al. Thoracolumbar interfascial plane (TLIP) block: a pilot study in volunteers. Can J Anaesth. 2015;62(11):1196-1200. 9. Ahiskalioglu A, Alici HA, Selvitopi K, Yayik AM. Ultrasonography-guided modified thoracolumbar interfascial plane block: a new approach. Can J Anaesth. 2017;64(7):775-776. 10. Ye Y, Bi Y, Ma J, Liu B. Thoracolumbar interfascial plane block for postoperative analgesia in spine surgery: a systematic review and meta-analysis. PLoS One. 2021;16(5):e0251980.

11. Ciftci B, Ekinci M, Celik EC, Yayik AM, Aydin M, Ahiskalioglu A. Ultrasound-guided erector spinae plane block versus modified-thoracolumbar interfascial plane block for lumbar discectomy surgery: a randomized, controlled study. World Neurosurg. 2020;144:e849-e855. 12. Rafi AN. Abdominal field block: a new approach via the lumbar triangle. Anaesthesia. 2001;56(10):1024-1026. 13. Abdallah FW, Laffey JG, Halpern SH, Brull R. Duration of analgesic effectiveness after the posterior and lateral transversus abdominis plane block techniques for transverse lower abdominal incisions: a meta-analysis. Br J Anaesth. 2013;111(5):721-735. 14. Reisener MJ, Hughes AP, Okano I, et al. The association of transversus abdominis plane block with length of stay, pain and opioid consumption after anterior or lateral lumbar fusion: a retrospective study [published online ahead of print]. Eur Spine J. https://doi. org/10.1007/s00586-021-06855-8

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