Vertebral Columns Spring 2023

INSIDE

Percutaneous Transforaminal Endoscopic Discectomy: Surgical Indications, Technique, and Patient Outcomes Do Lumbar Epidural Steroid Injections Increase Infections After Lumbar Spine Surgery?

Drains in Spine Surgery Strategies to reduce radiation exposure during spine surgery 3D Printing in Spine Surgery: Is the Hype Real?

Variability in Spine Surgery Training

Vertebral

COLUMNS International Society for the Advancement of Spine Surgery

Virtual Reality

for Preoperative Planning in Spine Surgery

SPRING 2023

XLIF: Single Position Lateral Versus Prone-Lateral

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EDITORIAL Virtual Reality for Preoperative Planning in Spine Surgery

SPINE FUSION XLIF: Single Position Lateral Versus ProneLateral

Editor in Chief Kern Singh, MD Editorial Board

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14 16 20 23 26

ENDOSCOPIC SPINE SURGERY Percutaneous Transforaminal Endoscopic Discectomy: Surgical Indications, Technique, and Patient Outcomes

PATIENT OUTCOMES Do Lumbar Epidural Steroid Injections Increase Infections After Lumbar Spine Surgery?

PATIENT OUTCOMES Drains in Spine Surgery

Brandon Hirsch, MD Sravisht Iyer, MD Yu-Po Lee, MD Sheeraz Qureshi, MD, MBA Managing Editor Audrey Lusher Designer CavedwellerStudio.com

IMAGING SAFETY Strategies to reduce radiation exposure during spine surgery

NEW TECHNOLOGY 3D Printing in Spine Surgery: Is the Hype Real?

TRAINING Variability in Spine Surgery Training

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

Spring 2023

Peter Derman, MD, MBA

Vertebral Columns

Vertebral Columns is published quarterly by the International Society for the Advancement of Spine Surgery. ©2023 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-Spring-2023

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

EDITORIAL

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Virtual Reality for Preoperative Planning in Spine Surgery James W. Nie, BS

Since the 1970s, preoperative planning in spine surgery has been reliant on computed tomography (CT) and magnetic resonance imaging (MRI) to constructing 2-dimensional (2D) cross-sections to examine patient anatomy.1 Using these modalities, the surgeon relies on mentally integrating a combination of these images to visualize a 3-dimensional (3D) model of the patient’s anatomy. Furthermore, these modalities do not correspond with the surgeon’s operative view.2–4 However, the introduction of virtual reality (VR) has allowed for a commercially available method in translating these 2D cross-sections into 3D virtual models.2 Using the head-mounted display (HMD) and controllers, the surgeon may manipulate the anatomical structures to obtain a better understanding of the patient’s anatomy and plan their surgical approach accordingly.

Improving visualization and providing tactile manipulation has been demonstrated to improve identification of anatomical abnormalities not typically visualized through conventional radiographic modalities.1,2 As such, VR preoperative planning has been increasingly utilized in decision-making in complex cranial procedures.1,5–8 Although VR preoperative planning has not seen as much adoption in spine surgery, some articles have published its utility in decision-making, satisfaction, and clini-

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cal outcomes. In this article, we discuss the affordability of incorporating VR preoperative planning in spine surger y as well as how VR planning may Timothy J. Hartman, MD influence decisions in surgical approach in the cervical and lumbar spine.

With advancements in commercially available VR systems, Keith R. MacGregor, BS forming 3D models from Digital Imaging and Communications in Medicine (DICOM) files has become increasingly affordable to implement in a surgeon’s Omolabake O. Oyetayo, BS practice. One of the most affordable VR systems is the Google Cardboard, a VR system formed by ca rdboa rd cutouts a nd a smartphone. Other commercially available VR headsets, Eileen Zheng, BS such as the Oculus systems, cost approximately $300. For preoperative planning, Salvatore et al compared preoperative planning techniques using Google CardKern Singh, MD board and conventional CT planning in 65 patients undergoing correction of adolescent idiopathic scoliosis.2 The authors systematically evaluated the number of fusion levels, screw direction, potential structural abnormalities, poten-

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EDITORIAL

tial bone abnormalities, type of approach, a nd number of required osteotom ies. 2 Patients who underwent VR planning had significantly lower operative times, blood loss, and hospital stay with higher surgeon satisfaction. 2 The authors reported that the improved visualization of the patient anatomy allowed for greater comprehension of delicate structures in the operative field and therefore provided greater awareness of potential risks. 2 As such, incorporating VR in preoperative planning in spine surgery is affordable and may provide significant benefits in perioperative outcomes.

The use of VR for preoperative planning may influence surgeons in the type of surgeries performed. Zawy Alsofy et al compared the impact of VR planning in minimally invasive and open single-level lumbar decompres-

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sion and/or fusion. 3 The authors reported that VR significantly influenced whether the surgeons utilized decompression only or decompression and fusion, minimally invasive or open technique, and type of surg ica l approach. 3 T he use of V R allowed for greater visualization of pars defects and arthritic changes in the facet joints, influencing surgeons to select decompression and f usion. 3 Additionally, as previous st ud ies have demonstrated the advantages of VR for learning surgical approaches, the improved visualization may allow for greater confidence in recognizing critical structures for surgeons to become comfortable with a minimally invasive approach.3,9,10 Furthermore, selection of a minimally invasive approach typically results in less blood loss and shorter postoperative length of stay with similar postoperative clinical outcomes, thus reducing healthcare expenditures. 3,11–13 As such, use of VR in preoperative planning may significantly influence surgical decision-making in the lumbar spine and lead to less invasive approaches when possible.

As in the lumbar spine, the use of V R planning may significantly impact surgical decision-making in the cervical spine. In a separate article by Zawy Alsofy et al, the

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EDITORIAL

authors examined the influence of VR on preoperative planning in patients with single-level cervical foraminal stenosis.4 Zawy Alsofy et al reported that VR influenced the style of anterior approach instrumentation utilized (ie, cage, cage+plate, or arthroplasty), with a trend toward significance in favoring a posterior over anterior surgical approach.4 Although Oshina et al did not utilize VR, the authors formed a 3D MRI/CT fusion image and reported that 18.1% of cervical radiculopathy cases had a change in strategy once the neuroforamen was fully visualized.14 Specifically, the surgeons in this study opted for more extensive decompression.14 As such,

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improved virtual visualization of the cervical spine may significantly impact surgical decision-making regarding approach and extent of decompression.

Preoperative surgical planning using VR allows for more intuitive visualization of patient anatomy compared to traditional radiographic evaluat ion. Furt hermore, improved visualization and tactile manipulation may allow surgeons to determine anatomical abnormalities not typically seen on CT or MRI. With commercially available VR systems, incorporating VR in preoperative planning is affordable and may significantly influence surgical decision-making. n

References 1. Lan L, Mao RQ, Qiu RY, Kay J, de Sa D. Immersive virtual reality for patient-specific preoperative planning: a systematic review. Surg Innov. 2023;30(1):109-122.

6. Steineke TC, Barbery D. Virtual reality preoperative planning to reduce procedure time of microsurgical clipping of MCA aneurysm. Neurosurgery. 2020;67(Supplement_1).

11. McClelland S 3rd, Goldstein JA. Minimally invasive versus open spine surgery: what does the best evidence tell us? J Neurosci Rural Pract. 2017;8(2):194-198.

2. De Salvatore S, Vadalà G, Oggiano L, Russo F, Ambrosio L, Costici PF. Virtual reality in preoperative planning of adolescent idiopathic scoliosis surgery using Google Cardboard.

Neurospine. 2021;18(1):199-205.

7. Kockro RA, Serra L, Tseng-Tsai Y, et al. Planning and simulation of neurosurgery in a virtual reality environment. Neurosurgery.

2000;46(1):118-135; discussion 135-137.

12. Mooney J, Michalopoulos GD, Alvi MA, et al. Minimally invasive versus open lumbar spinal fusion: a matched study investigating patient-reported and surgical outcomes. J Neurosurg Spine. 2021;36(5):753-766.

3. Zawy Alsofy S, Nakamura M, Ewelt C, et al. Retrospective comparison of minimally invasive and open monosegmental lumbar fusion, and impact of virtual reality on surgical planning and strategy. J Neurol Surg A Cent Eur Neurosurg. 2021;82(5):399-409.

4. Zawy Alsofy S, Stroop R, Fusek I, et al. Virtual reality-based evaluation of surgical planning and outcome of monosegmental, unilateral cervical foraminal stenosis. World Neurosurg. 2019;129:e857-e865.

5. Stadie AT, Kockro RA, Reisch R, et al. Virtual reality system for planning minimally invasive neurosurgery [technical note]. J Neurosurg. 2008;108(2):382-394.

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8. Anthony D, Louis RG, Shekhtman Y, Steineke T, Frempong-Boadu A, Steinberg GK. Patient-specific virtual reality technology for complex neurosurgical cases: illustrative cases. J Neurosurg Case Lessons. 2021;1(23):CASE21114.

9. McCloskey K, Turlip R, Ahmad HS, Ghenbot YG, Chauhan D, Yoon JW. Virtual and augmented reality in spine surgery: a systematic review.

World Neurosurg. 2023;173:96-107.

10. Lohre R, Wang JC, Lewandrowski KU, 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.

13. Holy CE, Corso KA, Bowden DE, et al. Evaluation of cost, payments, healthcare utilization, and perioperative and post-operative outcomes of patients treated with posterior lumbar spinal surgery using open versus minimally invasive surgical approaches. Med Devices. 2021;14:173-183.

14. Oshina M, Oshima Y, Tanaka S, et al.

Utility of oblique sagittal reformatted and three-dimensional surface reconstruction computed tomography in foraminal stenosis decompression. Sci Rep. 2018;8(1):16011.

Vertebral Columns

Spring 2023

ISASS23 23RD ANNUAL CONFERENCE

JUNE 1 – JUNE 3, 2023

MARRIOTT MARQUIS • SAN FRANCISCO, CA • Interactive meeting led by world-class faculty • Focused on new technologies and techniques • AMA PRA Category 1 Credit(s)™ available

President: Massimo Balsano, MD

Program Chair: Han Jo Kim, MD

Program Chair: Luis Tumialan, MD

Vice Chair: Praveen Mummaneni, MD

Vice Chair: Peter Passias, MD

JOINTLY PROVIDED BY:

LEARN MORE: ISASS.ORG

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

SPINE FUSION

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XLIF: Single Position Lateral Versus Prone Lateral Tomoyuki Asada, MD

Extreme lateral lumbar interbody fusion (XLIF) is a newer technique in spinal surger y that has the advantage of insertion of a larger cage leading to less subsidence and greater lumbar lordosis restoration.

The single-position (SP) XLIF focuses on inser t ing percutaneous pedicle screws (PPS) in the lateral position w ithout the need to “f lip” the patient to a prone position to save operative time. Traditionally, t he dual position (DP) X LIF involved a time-consuming process of modifying the patient positioning, in turn, “f lipping” the patient to assist with the insertion of pedicle screws.1 This predisposed patients to heavier anesthesia doses and increased operative time and required expertise in modif y ing t he pat ient posit ion. In t he present article, we discuss the benefits and potential drawbacks of SP X LIF.

Why Single Position?

T he SP tech n ique has t he potent ia l to reduce blood loss, operat ive t ime, and leng th of hospital stay while achiev ing the singular unified goal of lateral interbody fusion.1 In a systematic rev iew by Guiroy et al, patients who under went an SP approach were found to have reduced operat ive t i me, est i mated blood loss, length of hospital stay, and f luoroscopic radiat ion dosage compared to pat ients

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who under went a dua l position approach.1,2 Similarly, in a study by Ziino et al, repositioning, re-prep, and re-drape Nishtha Singh, MBBS while transitioning to a prone position in DP increased the overa ll operat ing room t ime by 44 minutes as compared to SP. 3 In terms of postoperative compl ic at ion s, t he reduc ed Sumedha Singh, MBBS, MD operative and occupancy time have been linked to decreased incidence of ileus, peritoneal injur y, and ipsilateral muscle injury in patients with SP procedures.4 Another advantage of Pratyush Shahi, MBBS, MS (Ortho) SP is the abilit y to minimize t he i nc ide nc e of i nc r e a s e d intraocular pressure, cortical blindness, and subconjunctival hemorrhage as compared to the DP procedure. 3 In terms of radiological outcomes, BlizSheeraz Qureshi, MD, z a rd et a l repor ted t hat t he MBA pedicle screw accuracy rates in their SP group were equivalent to those of the DP group, which made SP a feasible option for lateral interbody fusion. 5 T his ev idence f u r t her st reng t hens t he advent of SP lateral fusion as the preferred surgical treatment approach for various spinal pathologies. 6

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Characteristics of SP XLIF In addition to the numerous benefits of the SP approach for patients and surgeons, this approach has recently gained popularity due to its efficacy in operation. There are currently two options for SP: XLIF in lateral decubitus position (std-XLIF) and XLIF in prone single-position (pro-XLIF).

Std-XLIF is now the default option for SP due to its clinical data and experience. It involves conventional XLIF and pedicle screw insertion with a lateral position. In particular, the lateral decubitus position stabilizes patients’ spine firmly, providing surgeons with a safe procedure, including the approach to the intervertebral space and cage placement in XLIF. However, there are some difficulties with screw placement in the lateral position. One issue is the difficulty of setting up the radiographic and instrument handling in the lateral position.

During the PPS procedure in the lateral position, the f luoroscopic arm may be in the way and care must be taken to keep the operative field clean. Additionally, screw insertion on the “down” side, which is the right side in the right-side-down lateral position, requires particular attention. In patients with a high BMI and when inserting the L5 or S1 PPS, the instrument needs to be angled largely under the patient. Utilizing navigation, patient positioning and robotic arms are key to solving these problems.

Navigation provides a more comfortable procedure compared to a procedure with a C-arm, as there is no C-arm to barricade the surgical area. Regarding patients’ position, a slightly more forward-leaning posture

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Vertebral Columns

than the lateral decubitus position for cage placement can make it easier to handle the instruments during screw insertion.

Furthermore, a recent study reported that use of a robotic arm could improve the feasibility of PPS in lateral decubitus position.7 With such ingenuity and surgical proficiency, std-XLIF can be an effective tool to minimize the invasion.

Performing both XLIF and PPS insertion in the prone position, as in pro-XLIF, may be advantageous to many spine surgeons who are familiar with this position. It allows surgeons to insert PPS as normally as in the original version and to directly access the posterior spinal column and decompression if required. However, cage insertion in a prone position becomes unfamiliar contrary to the std-XLIF. The different points of prone-lateral XLIF were exposures and stabilization of the spine. Maintaining visual access to the surgical site in a sitting position can be challenging. An additional point of concern is the location of the nerve and organs, but previous studies have revealed that the iliopsoas muscle and the femoral nerve are typically more posteriorly located at the L4-5 disc space in the prone position compared to in the lateral decubitus position, which allows for a larger safe zone. 8,9 Regarding spine stabilization, it is possible to see where the spine is more mobile in the pro-XLIF surgical field than in the std-XLIF field, but again, navigation can help.

Pro-XLIF offers several advantages over conventional lateral single position for adjacent segmental disorders (ASD). Due to problems such as rod connection to the

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SPINE FUSION

previous surgical site, it has been difficult to achieve additional surgery for ASD using XLIF in the lateral position, requiring flipping the position. Pro-XLIF can make it simple, as every surgical procedure, including posterior dissection, can be achieved in one position. Furthermore, this position has been reported to be advantageous for obtaining lumbar lordosis.9 It is an effective approach in terms of lordosis acquisition and can be an effective means of preventing long-term malalignment, even in cases of adjacent intervertebral disorders in which there is a risk of developing flatback.

Most surgeons, including those in spine and urology specialties, find that surgeries in the lateral decubitus position are more comfortable. Moreover, this position also offers advantages in certain scenarios, such as when a urethral tract injur y requires salvage procedures. If accidental urethral tract injury occurs in the prone position, flipping to the lateral decubitus or the supine position may be required. In the cases of vascular injury, flipping is mandatory for the additional procedure by vascular surgeons, but changing position from lateral decubitus would be easier than from prone to supine.

Each institution needs to establish a consensus for salvage procedures and flipping in cases of intraoperative complications for both pro-XLIF and std-XLIF.

Clinical Outcomes of std-XLIF vs proXLIF W hen considering surg ica l techniques for patients, it is important to weigh the benefits and drawbacks of each approach.

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Regarding pro-XLIF, a cadaveric feasibility study and early experiences revealed its safety and reproducibility,10-12 and preliminary clinical results showed comparable clinical results to std-XLIF.13 Furthermore, prone-lateral LLIF was safely performed in the early analysis of the surgery for ASD.14 Based on these results, the pro-XLIF is safe enough for clinical application. However, the analysis for the surgical complications is lacking because the number of patients analyzed remains limited.

A CT-based assessment study found that the accuracy of PPS in the lateral position was lower than that in the prone position with higher breach rates (14.1% vs 7.2%), but none of them resulted in clinical sequelae.7 However, another report suggested that the accuracy of PPS in both positions may be comparable.15 It appears that proficiency in the technique, rather than the position itself, w ill be the key factor in achieving accurate PPS placement. Shortterm postoperative outcomes are generally equivalent for both procedures if performed sa fely, but no la rge-sca le st udies have been conducted to date. Further studies are needed to understand the impact on long-term results and complication rates resulting from differences in lumbar lordosis acquisition due to body position.

Summary and Future In summar y, X LIF allows the insertion of a larger interbody cage t hat has t he advantages of greater lordosis restoration and less subsidence. Traditionally, XLIF used to be done in t he lateral posit ion

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followed by an intraoperative f lip to the prone position for the insertion of pedicle screws. SP XLIF evolved mainly to avoid i nt raoperat ive reposit ion i ng a nd t hus decrease the operative time. The recent addition to the realm of X LIF has been prone to lateral surgery. XLIF in the prone position provides the advantages of a familiar position in PPS for spine surgeons, increased lumbar lordosis due to positioning, simultaneous posterior access for decompression/osteotomies, and possibly a more posterior location of the femoral

nerve. Although there have been various studies demonstrating the benefits of SP XLIF establishing it as a surgical option, there are fewer data available on the safety and efficacy of pro-XLIF, mainly because it is a relatively new surgery. In our experience, pro-XLIF has demonstrated similar outcomes as std-X LIF w it h a favorable side-effect profile. Future research with a larger sample size and longer follow-up is required to assess long-term outcomes and compare prone lateral with single-position lateral procedures. n

References 1. Guiroy A, Carazzo C, Camino-Willhuber G, et al. Single-position surgery versus lateral-then-prone-position circumferential lumbar interbody fusion: a systematic literature review. World Neurosurg. 2021;151:e379-e386.

5. Blizzard DJ, Thomas JA. MIS single-position lateral and oblique lateral lumbar interbody fusion and bilateral pedicle screw fixation: feasibility and perioperative results. Spine (Phila Pa 1976). 2018;43:440-446.

11. North RY, Strong MJ, Yee TJ, Kashlan ON, Oppenlander ME, Park P. Navigation and robotic-assisted single-position prone lateral lumbar interbody fusion: technique, feasibility, safety, and case series.

World Neurosurg. 2021;152:221-230.e1.

2. Buckland AJ, Ashayeri K, Leon C, et al.

Single position circumferential fusion improves operative efficiency, reduces complications and length of stay compared with traditional circumferential fusion. Spine J. 2021;21:810-820.

6. Hiyama A, Katoh H, Sakai D, Sato M, Tanaka M, Watanabe M. Comparison of radiological changes after single-position versus dual-position for lateral interbody fusion and pedicle screw fixation. BMC Musculoskelet Disord. 2019;20:601.

12. Farber SH, Naeem K, Bhargava M, Porter RW. Single-position prone lateral transpsoas approach: early experience and outcomes. J Neurosurg Spine. 2021:1-8.

3. Ziino C, Konopka JA, Ajiboye RM, Ledesma JB, Koltsov JCB, Cheng I. Single position versus lateral-then-prone positioning for lateral interbody fusion and pedicle screw fixation. J Spine Surg. 2018;4:717-724.

7. Fayed I, Tai A, Triano MJ, et al. Lateral versus prone robot-assisted percutaneous pedicle screw placement: a CT-based comparative assessment of accuracy.

J Neurosurg Spine. 2022;37(1):4-12.

4. Ouchida J, Kanemura T, Satake K, Nakashima H, Ishikawa Y, Imagama S. Simultaneous single-position lateral interbody fusion and percutaneous pedicle screw fixation using O-arm-based navigation reduces the occupancy time of the operating room. Eur Spine J. 2020;29:1277-1286.

8. Alluri R, Clark N, Sheha E, et al. Location of the femoral nerve in the lateral decubitus versus prone position. Global Spine J. 2021:21925682211049170.

9. Amaral R, Daher MT, Pratali R, et al.

The effect of patient position on psoas morphology and in lumbar lordosis.

World Neurosurg. 2021;153:e131-e140.

10. Godzik J, Ohiorhenuan IE, Xu DS, et al.

Single-position prone lateral approach: cadaveric feasibility study and early clinical experience. Neurosurg Focus. 2020;49:E15. doi:10.3171/2020.6.FOCUS20359

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13. Lamartina C, Berjano P. Prone single-position extreme lateral interbody fusion (Pro-XLIF): preliminary results. Eur Spine J. 2020;29:6-13.

14. Wang TY, Mehta VA, Sankey EW, et al. Single-position prone transpsoas fusion for the treatment of lumbar adjacent segment disease: early experience of twenty-four cases across three tertiary medical centers. Eur Spine J. 2022;31:2255-2261.

15. Hiyama A, Katoh H, Sakai D, Sato M, Tanaka M, Watanabe M. Accuracy of percutaneous pedicle screw placement after single-position versus dual-position insertion for lateral interbody fusion and pedicle screw fixation using fluoroscopy. Asian Spine J. 2022;16:20-27.

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

ENDOSCOPIC SPINE SURGERY

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Percutaneous Transforaminal Endoscopic Discectomy: Surgical Indications, Technique, and Patient Outcomes The emergence of endoscopic techniques in spine surgery represents more than 5 decades of surgical innovation.1 While these techniques have been historically limited by low-quality imaging, the advancement of appropriate surgical instrumentation and ancillary camera systems in recent years has led to the increasing utilization of endoscopic approaches in spine surgery.

Percutaneous transforaminal endoscopic discectomy (PTED) is one such technique that has been investigated as a potential alternative to tubular microdiscectomy (TM).

Although TM is still considered the gold standard for minimally invasive treatment of symptomatic lumbar disc herniation (LDH), PTED has been shown to offer several advantages regarding iatrogenic morbidity. These include minimal muscle dissection and soft tissue damage, decreased removal of bony structures, and negligible manipulation of neural elements allowing for reduced blood loss, rapid recovery, and preservation of segmental stability.1,2

Surgical Indications and Considerations Utilization of PTED is warranted for patients presenting with signs of radiculopathy and nerve root tension due to LDH after 12 weeks of failed conservative therapy. However,

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Omri Maayan, BS

several patient-level factors must be considered prior to surgical intervention. While PTED has been shown to effectively treat Anthony Pajak, BS extruded LDHs, far migrated or sequestered discs have been reported as potential contraindications. A disc that has migrated upward or downward may necessitate a pediculectomy or translaminar approach. 2 LikeMaximilian K. Korsun, BS wise, in patients with a steep iliac crest above t he mid-L5 pedicle in lateral radiography, insertion of the cannula through the intervertebral foramen may prove difficult. Prior reports Pratyush Shahi, MBBS, MS (Ortho) have recommended foraminoplasty for transforaminal access in t hese cases. 3,4 PTED w it h foraminoplast y has likew ise been introduced as a potential treatment for patients with concomitant spondylolisthesis, in Sravisht Iyer, MD comparison to traditional laminectomy and fusion. However, PTED alone should not be used for patients presenting with spondylolisthesis with segmental instability. 5 Patients with a prior history of conventional microdiscectomy and recurrent LDH may additionally have associated scar

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formation that alters local anatomy, obscures visualization, and is challenging to address with a transforaminal approach. Dissection of scar tissue from the medial facet joint via percutaneous interlaminar endoscopic discectomy has been suggested as a potential alternative.6 As such, there are several conditions surgeons should be wary of when considering PTED for treatment of LDH.

Surgical Technique Preoperatively, a reference line is drawn from the superior articular process to the midpoint of the superior endplate once the level of LDH is determined. Prior to incision, the patient is placed in the lateral decubitus position or traditional prone position on a Wilson frame.7,8 The primar y incision should be made within 8 to 12 cm lateral to the midline depending on the operated level. Operations at L2-L3, L3-L4, and L5-S1 should have incisions made 8 cm, 10 cm, and 12 cm from the midline, respectively.7 An 18-gauge needle is subsequently inserted through Kambin’s triangle. The angle of needle insertion should be approximately 55° to 65° in the craniocaudal direction and 30° to 40° on both the anteroposterior and axial views.

The disc material is then stained to aid in visualization when utilizing the endoscope.

Next, the guidewire is inserted through the needle. Dilation of the neuroforamen up to 8mm is conducted using dilators of varying sizes to prevent irritation of the exiting nerve root. Following dilation, the insertion of the cannula and endoscope may commence.

The surgeon must be able to visualize the

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intradiscal space and previously stained disc material through the endoscope. The high-resolution endoscopic camera system permits comprehensive visualization of the spine with an angled field view ranging from 20° to 90°. 9 A rongeur is then used to grasp and remove the disc material through the working channel of the endoscope. The procedure is deemed sufficient once mobilization of the nerve root and pulsations in line with the heart rate are achieved.10 The disc space is then visualized to ensure that no loose disc material remains. Corticosteroids may be applied around the nerve root to reduce pain.7,9 Finally, the endoscope is withdrawn, hemostasis is achieved, and closure is performed.

Outcomes A systematic review comparing outcomes between PTED and open microdiscectomy determined that there is a slightly increased risk of LDH recurrence among patients treated with PTED. However, PTED was also associated with a significantly decreased length of hospital stay and trended toward improved leg pain, functional recover y, and operative time.11 Another study implementing the American College of Surgeon’s National Surgical Qualit y Improvement Program database compared 175 patients u ndergoi ng endoscopic d iscectomy to 38,322 patients undergoing open discectomy and found that endoscopic discectomy resulted in a significantly shorter length of stay (0.81 vs. 1.15 days) and lower rate of adverse events (0.6% vs. 3.4%).12 Although previous studies have primarily focused

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on comparing open discectomy to MIS approaches, few have compared endoscopic to tubular techniques. One of the primary advantages of endoscopy is the ability to extract foraminal discs without removing bony components. Unlike endoscopy, removal of the foraminal disc using tubular techniques requires a facetectomy, thus necessitating subsequent fusion. Liu et al evaluated 60 PTED and 60 TM patients across a 20-month period and similarly found that the PTED group exhibited less intraoperative blood loss (18.0 mL vs 39.83 mL, p <0.001), shorter length of stay (5.4 days vs 10.6 days), and lower incidence of paresthesia (6.67% vs 16.67).13

13

Conclusion PTED is an innovative technique aimed at reducing tissue damage when treating LDH. Unlike open and tubular microdiscectomy, PTED eliminates the need for muscle d issect ion, bone remova l, a nd nerve root retraction by accessing the disc space through the intervertebral foramen.

Despite concerns raised by spine surgeons regarding the potential risks of PTED due to the narrow working corridor and uncertainty regarding successful decompression, research has demonstrated that PTED is a safe and effective treatment option for LDH among patients who meet the appropriate operative criteria. n

References 1. Jang JW, Lee DG, Park CK. Rationale and advantages of endoscopic spine surgery. Int J Spine Surg. 2021;15(suppl 3):S11-S20.

2. Kapetanakis S, Gkasdaris G, Angoules AG, Givissis P. Transforaminal percutaneous endoscopic discectomy using transforaminal endoscopic spine system technique: pitfalls that a beginner should avoid. World J Orthop. 2017;8(12):874-880.

3. 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.

4. Choi KC, Park CK. Percutaneous endoscopic lumbar discectomy for L5-S1 disc herniation: consideration of the relation between the iliac crest and L5-S1 disc. Pain Physician. 2016;19(2):E301-308.

5. Li XF, Jin LY, Lv ZD, et al. Efficacy of percutaneous transforaminal endo-

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scopic decompression treatment for degenerative lumbar spondylolisthesis with spinal stenosis in elderly patients.

Exp Ther Med. 2020;19(2):1417-1424.

6. Kim CH, Chung CK, Jahng TA, Yang HJ, Son YJ. Surgical outcome of percutaneous endoscopic interlaminar lumbar diskectomy for recurrent disk herniation after open diskectomy. J Spinal Disord Tech. 2012;25(5):E125-133.

7. Gadjradj PS, Harhangi BS. Percutaneous transforaminal endoscopic discectomy for lumbar disk herniation.

Clin Spine Surg. 2016;29(9):368-371.

8. Kapetanakis S, Gkasdaris G, Angoules AG, Givissis P. Transforaminal percutaneous endoscopic discectomy using transforaminal endoscopic spine system technique: pitfalls that a beginner should avoid. World J Orthop. 2017;8(12):874-880.

9. Yue JJ, Long W. Full endoscopic spinal surgery techniques: advancements, indications, and outcomes.

Int J Spine Surg. 2015;9:17.

10. Lee SG, Ahn Y. Transforaminal endoscopic lumbar discectomy: basic concepts and technical keys to clinical success. Int J Spine Surg. 2021;15(suppl 3):S38-S46.

11. Zhang B, Liu S, Liu J, et al. Transforaminal endoscopic discectomy versus conventional microdiscectomy for lumbar disc herniation: a systematic review and meta-analysis.

J Orthop Surg Res. 2018;13:169.

12. Page PS, Ammanuel SG, Josiah DT. Evaluation of endoscopic versus open lumbar discectomy: a multi-center retrospective review utilizing the American College of Surgeons’ National Surgical Quality Improvement Program (ACSNSQIP) database. Cureus. 14(5):e25202.

13. Liu L, Xue H, Jiang L, et al. Comparison of percutaneous transforaminal endoscopic discectomy and microscope-assisted tubular discectomy for lumbar disc herniation. Orthop Surg. 2021;13(5):1587-1595.

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Yu-Po Lee, MD

PATIENT OUTCOMES

Do Lumbar Epidural Steroid Injections Increase Infections After Lumbar Spine Surgery?

Epidural steroid injections (ESIs) have been demonstrated to successfully decrease pain in patients who have radiculopathy from disc herniations and stenosis.1-2 ESIs are available as a form of conservative treatment that offer potential in either avoiding or postponing surgical intervention. However, in cases in which patients do not have pain relief after epidural steroid injections, how long should surgeons wait before they can operate on the patient without an increased risk of a postoperative infection? Some authors have recommended waiting more than 3 months before spine surgery, a concept further promoted by evidence in joint arthroplasty.3-4 However, in a patients with pain refractory to ESI or with more rapid neurological deterioration, waiting an indeterminate period may not be the best option.5 Thus, determining an appropriate time to wait after epidural steroid injections would be helpful for spine surgeons. In this article, I review the current literature on the increased risk of infections in patients who have had lumbar spine surgery after ESI.

Infection Rates After ESI Some studies have reported increased infection rates in patients who have spine surgery after an epidural steroid injection. For example, Kreitz et al performed a retrospective review

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From UCI Health in Orange County, California.

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on 15,011 patients who had spine surgery.6 Among the patient population, 5108 underwent fusion and 9903 had a decompression only. The infection rate was 1.95% for fusion patients and 0.98% in patients who had only decompression.

The authors concluded that there was an increased risk of infection in patients who had a fusion but no increased risk in patients with decompression only. Although the authors noted an association between preoperative epidural steroid injections and fusion, BMI, and Charlson Comorbidity Index, there was no association between age and sex.

In another study, Singla et al performed a database search on patients who received ESI prior to surgery.7 The authors noted an increased infection rate in patients who had a lumbar spinal fusion performed within 3 months after ESI, but they did not find an increased infection rate if the injection was performed more than 3 months prior to surgery.

Yang et al performed a database search in the PearlDiver database.8 The authors evaluated infection rates in patients who had single-level lumbar decompression after ESI. The authors noted that having a lumbar decompression within 3 months after ESI may be associated with an increased rate of infection. As a result, these authors recommended delaying surgery for 3 months after an ESI. Li et al performed

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a retrospective review of patients who had a lumbar fusion after ESI and found a statistically significant difference in patients who had an ESI 1 month prior to surgery.9 Meanwhile, Donnely et al performed a database search on patients who had ESIs prior to lumbar decompression and found a statistically significant difference in patients who had an epidural steroid injection up to 6 months prior to surgery.10 Despite these reports, several papers have reported no association between infection rates and epidural steroid injections prior to surgery.

In a study by Hartveldt et al, the medical records of 56,311 patients who had spine surgery were reviewed. Of these patients, 11,945 had an epidural steroid injection within 90 days of surgery, and 134 (2.5%) developed a postoperative infection.11 The authors did not see an increased rate of infection in patients who had epidural steroid injections

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prior to surgery at any time points (within 30 days, 30-90 days, and greater than 90 days). Seavey et al performed a retrospective review on 6535 patients in the Military Heath Systems Repository and found no significant variation between an ESI cohort and a control cohort with regard to infection rates.12 This finding was further validated by a similar study by Pisano et al.13

Conclusion Overall, while conf licting data are present, current literature recommends delaying surgical intervention for at least 3 months after ESI in cases of lumbar fusion or increased patient comorbidity burden. However, some situations, such as increased progression of neurological deficits, may require surgeons to more critically discuss risks versus benefits with patients prior to surgical intervention. n

References 1. Fekete T, Woernle C, Mannion AF, et al.

The effect of epidural steroid injection on postoperative outcome in patients from the lumbar spinal stenosis outcome study. Spine. 2015;40(16):1303–1310.

2. Kaufmann TJ, Geske JR, Murthy NS, et al.

Clinical effectiveness of single lumbar transforaminal epidural steroid injections. Pain Med. 2013;14(8):1126–1133.

3. Kreitz TM, Mangan J, Schroeder GD, et al.

Do preoperative epidural steroid injections increase the risk of infection after lumbar spine surgery? Spine. 2021;46(3):E197.

4. Desai A, Ramankutty S, Board T, Raut V. Does intraarticular steroid infiltration increase the rate of infection in subsequent total knee replacements? Knee. 2009;16(4):262–264.

5. Støttrup CC, Andresen AK, Carreon L, Andersen MØ. Increasing reoperation rates and inferior outcome with prolonged symptom duration in lumbar disc herniation surgery: a prospective cohort

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study. Spine J. 2019;19(9):1463–1469.

6. Kreitz TM, Mangan J, Schroeder GD, et al.

Do preoperative epidural steroid injections increase the risk of infection after lumbar spine surgery? Spine. 2021;46(3):E197.

7. Singla A, Yang S, Werner BC, et al. The impact of preoperative epidural injections on postoperative infection in lumbar fusion surgery. J Neurosurg Spine. 2017;26(5):645–649 8. Yang S, Werner BC, Cancienne JM, et al. Preoperative epidural injections are associated with increased risk of infection after single-level lumbar decompression. Spine J. 2016;16(2):191–196.

9. Li P, Hou X, Gao L, Zheng X. Infection risk of lumbar epidural injection in the operating theatre prior to lumbar fusion surgery. J Pain Res. 2020;13:2181–2186.

10. Donnally CJ, Rush AJ, Rivera S, et al.

An epidural steroid injection in the 6 months preceding a lumbar decom-

pression without fusion predisposes patients to post-operative infections.

J Spine Surg. 2018;4(3):529–533.

11. Hartveldt S, Janssen SJ, Wood KB, et al. Is There an association of epidural corticosteroid injection with postoperative surgical site infection after surgery for lumbar degenerative spine disease? Spine. 2016;41(19):1542–1547.

12. Seavey JG, Balazs GC, Steelman T, Helgeson M, Gwinn DE, Wagner SC. The effect of preoperative lumbar epidural corticosteroid injection on postoperative infection rate in patients undergoing single-level lumbar decompression.

Spine J. 2017;17(9):1209–1214.

13. Pisano AJ, Seavey JG, Steelman TJ, Fredericks DR, Helgeson MD, Wagner SC. The effect of lumbar corticosteroid injections on postoperative infection in lumbar arthrodesis surgery.

J Clin Neurosci. 2020;71:66–69.

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From the Texas Back Institute, Plano, Texas.

Drains in Spine Surgery Dean Perfetti, MD, MPH

Alexander M. Satin, MD

Peter B. Derman, MD, MBA

As spine surgeons strive to improve patient outcomes, decrease complications, and control costs, they must determine which pharmacologic and surgical measures are worth implementing. Surgical drains are used by some in an effort to reduce the risk of complications, such as surgical site infection (SSI), compressive hematoma, and delayed wound hea ling. However, drain use could also increase infection risk and postoperative blood loss.

Given the lack of consensus on drain utilization, we review the literature on wound drains in spine surgery to help delineate their potential efficacy and limitations.

Cervical Spine Drain use in the cervical spine after treating degenerative cervical pathology is tailored to different risks associated with the anterior and posterior cervical approaches. Some spine surgeons place a drain following anterior cervical discectomy and fusion (ACDF) to prevent wound hematoma, which can lead to airway compromise. Upper airway compromise occurring in the immediate postoperative period most commonly stems from an expanding hematoma and has a reported prevalence of 0.2% to 1.9%.1 Clinically significant retropha-

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ryngeal hematomas typically appear within 6 to 12 hours postoperatively but can appear as late as 6 days after surgery.2 A retrospective cohort study found that patients with increased body mass index (BMI) and those undergoing ACDF at two or more levels had increased drain output and thus may benefit from surgical drain placement. 3 However, another retrospective review assessing 2,375 anterior cervical spine procedures found that only 0.7% of patients experienced a clinically significant postoperative hematoma, and 88% of patients with hematomas had a drain placed at the conclusion of the index surgery.4 Moreover, 27% of these patients still had their drains in place at the time of hematoma diagnosis.4 Drain placement may not be trivial even in multilevel cervical cases, as it is possible that drain removal can aggravate a vessel or muscle bed and lead to hematoma formation.

A retrospective study assessing 321 multi-level ACDF procedures comparing a drain cohort to a no-drain cohort found no difference in postoperative hematoma formation with a 14 times increased odds of postoperative allogenic blood transfusion in the drain cohort.5 A systematic review and meta-analysis using this evidence along with that of other studies concluded that utilization of a drain in anterior cervical spine surgery does not prevent hematoma formation and does not provide any additional benefits, although a definitive conclusion would require more randomized controlled trials (RCTs).6 It is

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therefore imperative that surgeons who use drains in the setting of ACDF do not allow this to provide them with a false sense of security— meticulous hemostasis should be obtained at the conclusion of every case regardless of whether or not a drain will be used.

Drains in posterior cervical spine surgery are often used in an effort to prevent epidural hematomas, wound breakdown, and SSIs. The incidence of a clinically significant postoperative epidural hematoma is about 0.1%.7 A retrospective study assessing risk factors for postoperative spinal epidural hematoma after 14,932 surgeries from 1984 to 2002 found patients to be at increased risk if they had one of the following associated variables: age greater than 60, pre-operative non-steroidal anti-inflammatory use, more than 5 operative levels, or blood loss greater than 1 liter.8 Drains were used in 72% of patients who experienced an epidural hematoma, and the lack of a subfascial drain was not associated with the development of a postoperative epidural hematoma.8 A more recent retrospective review assessing posterior cervical spine surgery also found that the rates of reoperation for hematoma did not differ between drain and no-drain cohorts (0.68% in drain, 0.48% no-drain, p = 0.62) even after adjusting for significant risk factors such as diabetes and number of operative levels (OR = 1.22, p = 0.77).9 However, patients with drains did have significantly lower odds of returning to the operating room for SSI (OR 0.48, p = 0.04) after adjusting for significant risk factors.9 SSI tends to be more common after posterior than anterior cervical spine surgery with reported rates as high as 18%.10 In a retrospective review, Sebastian et

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al found that among 5,441 patients, the incidence of SSI after posterior cervical surgery was 2.94%, and only a third of these patients required readmission.11 While Sebastian et al found obese patients (BMI >35) and those on chronic steroids to be at a significantly elevated risk of SSI, they did not assess for drain use.11 Nonetheless, suprafascial drain use in obese patients has been shown to significantly reduce postoperative deep infections in posterior cervical procedures.12

Lumbar Spine The rationale for drain use following the treatment of degenerative lumbar pathology is similar. The incidence of an asymptomatic early postoperative lumbar spine hematoma after lumbar discectomy on MRI has been found to be as high as 89% in patients without a subfascial drain and 36% in those with one.13 However, the incidence of a symptomatic epidural hematoma occurring in the majority of lumbar spine epidemiology studies is around 0.1% to 0.9%.14 A systematic review investigating wound drains in noncomplex lumbar spine surgery involving 1- or 2-level laminectomies and/or discectomies demonstrated that routine drain use does not prevent symptomatic postoperative epidural hematomas, nor does the absence of a drain lead to a significant change in the incidence of wound infection.15 Another meta-analysis assessing non-instrumented lumbar decompressions found no difference in risk of symptomatic epidural hematoma or postoperative infection between the 5,327 cases identified as having a drain and the 773 cases without a drain.16 A study of 1- to 3-level posterolateral fusions

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PATIENT OUTCOMES

with or without interbody fusion found that drain use increased length of stay but did not reduce complication rates.17 Moreover, a retrospective study by Walid et al found that patients with drains for 1- to 3-level lumbar fusions reported a statistically significantly higher incidence of post-hemorrhagic anemia compared to those without drains (23.5% vs 7.7%, p < 0.001) as well as an increased risk for allogenic blood transfusion (23.9% vs 6.8%, p < 0.001).18

Thoracolumbar Deformity Deformity operations are prone to wound breakdown and SSI due to their prolonged operative times, increased muscle dissection and retraction, and longer periods of relative immobility after surgery. A prospective RCT assessing drain use in adult deformity patients observed SSI in 12.7% of patients with a drain compared to 7% with no drain (p = 0.07).19 Of note, use of perioperative antibiotics for the entire drain duration versus the standard first 24 hours after surgery did not decrease the rate of SSI in the drain cohort.19 Drain utilization in pediatric spinal deformity correction has also not provided any additional benefit in reducing the risk of SSI or reoperation.6 A prospective RCT comparing a cohort with subfascial drains to a cohort with no drain in adolescent idiopathic scoliosis (AIS) cases found no advantage to subfascial drains—there was an identical number of wound healing complications.20 A multicenter retrospective analysis evaluating closed-suction wound drainage after posterior spinal fusion in AIS patients similarly reported no differences in the cohorts with regard to wound infection

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but did demonstrate more postoperative transfusions in the drain cohort (43% vs 22%, p < 0.001).21

Trauma and Tumor Although there have been several studies assessing the efficacy of closed-suction drainage after surgery for degenerative spine diseases, there is limited high level evidence on drain use in nonelective spinal pathologies such as trauma and tumor. In the setting of traumatic instability, utilization of a drain may not reduce the risk of SSI or provide additional benefits.6 In a randomized study of 110 patients assessing the impact of drain use in the setting of dorsolumbar spine surgery for trauma and neurologic deficits, Kumar et al found no statistically significant difference between groups in terms of postoperative wound infection rates, clinically significant hematomas, or risk of further neurological injury.22 Intradural involvement via trauma or tumor creates an additional problem: cerebrospinal fluid (CSF) leakage. Utilization of closed-suction drainage may promote continuous leakage of CSF even despite attempted dural repair.

A retrospective study assessed the benefit of closed-suction drainage and prevention of CSF leak-related complications after surgery for primary intradural spinal cord tumors.23 Among the 134 patients, postoperative MRI found CSF fluid collections in 9.7% of patients in the drain group and 10.8% of patients in the no-drain group (p = 0.87). These collections resolved uneventfully regardless of drain use, except in 2 patients in the no-drain group who required revision for wound-related problems (p = 0.20).23

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Conclusion Drain utilization continues to be utilized by some surgeons after spine surgery for degenerative conditions, deformity, trauma, and tumors. Nonetheless, the vast majority of literature demonstrates that the use of a drain does not lower the rate of symptomatic

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hematoma formation but instead may increase postoperative anemia, transfusion rates, SSI, and length of stay. While certain subgroups may benefit from drain placement for the prevention of wound complications (i.e., after posterior cervical surgery), this appears to be the exception rather than the rule. n

References 1. Palumbo MA, Aidlen JP, Daniels AH, Thakur NA, Caiati J. Airway compromise due to wound hematoma following anterior cervical spine surgery.

Open Orthop J. 2012;6:108-113.

2. Debkowska MP, Butterworth JF, Moore JE, Kang S, Appelbaum EN, Zuelzer WA. Acute post-operative airway complications following anterior cervical spine surgery and the role for cricothyrotomy. J Spine Surg. 2019;5(1):142-154.

3. Patil SR, Kishan A, Gabbita A, Varadharaju DN, Jagannath PM. Anterior cervical surgery: drain needed or not? J Spine Surg. 2015;2(2):37-41.

4. O’Neill KR, Neuman B, Peters C, Riew KD. Risk factors for postoperative retropharyngeal hematoma after anterior cervical spine surgery. Spine (Phila Pa 1976). 2014;39(4):E246-52.

5. Adogwa O, Khalid SI, Elsamadicy AA, Voung VD, Lilly DT, Desai SA, Sergesketter AR, Cheng J, Karikari IO. The use of subfascial drains after multi-level anterior cervical discectomy and fusion: does the data support its use?

J Spine Surg. 2018;4(2):227-232.

6. Muthu S, Ramakrishnan E, Natarajan KK, Chellamuthu G. Risk-benefit analysis of wound drain usage in spine surgery: a systematic review and meta-analysis with evidence summary.

Eur Spine J. 2020;29(9):2111-2128.

7. Schroeder GD, Hilibrand AS, Arnold PM, et al. Epidural hematoma following cervical spine surgery. Global Spine J. 2017;7(1 Suppl):120S-126S. 8. Awad JN, Kebaish KM, Donigan J, Cohen DB, Kostuik JP. Analysis of the risk factors for the development of post-operative spinal epidural haematoma. J Bone Joint

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Surg Br. 2005;87-B(9):1248-1252 9. Herrick DB, Tanenbaum JE, Mankarious M, et al. The relationship between surgical site drains and reoperation for wound-related complications following posterior cervical spine surgery: a multicenter retrospective study. J Neurosurg Spine. 2018;29(6):628-634.

10. Reier L, Fowler JB, Arshad M, Siddiqi J. Drains in spine surgery for degenerative disc diseases: a literature review to determine its usage.

Cureus. 2022;14(3):e23129.

11. Sebastian A, Huddleston P 3rd, Kakar S, Habermann E, Wagie A, Nassr A. Risk factors for surgical site infection after posterior cervical spine surgery: an analysis of 5,441 patients from the ACS NSQIP 20052012. Spine J. 2016;16(4):504-509.

12. Pahys JM, Pahys JR, Cho SK, et al.

Methods to decrease postoperative infections following posterior cervical spine surgery. J Bone Joint Surg Am. 2013;95(6):549-554.

13. Mirzai H, Eminoglu M, Orguc S. Are drains useful for lumbar disc surgery? A prospective, randomized clinical study.

J Spinal Disord Tech. 2006;19:171-177.

14. Butler AJ, Donnally CJ 3rd, Goz V, Basques BA, Vaccaro AR, Schroeder GD. Symptomatic postoperative epidural hematoma in the lumbar spine.

Clin Spine Surg. 2022;35(9):354-362.

15. Zijlmans JL, Buis DR, Verbaan D, Vandertop WP. Wound drains in non-complex lumbar surgery: a systematic review. Bone Joint J. 2016;98-B(7):984-989.

16. Davidoff CL, Rogers JM, Simons M, Davidson AS. A systematic review and me-

ta-analysis of wound drains in non-instrumented lumbar decompression surgery. J Clin Neurosci. 2018;53:55-61.

17. Molina M, Torres R, Castro M, et al.

Wound drain in lumbar arthrodesis for degenerative disease: an experimental, multicenter, randomized controlled trial. Spine J. 2023;23(4):473-483.

18. Walid MS, Abbara M, Tolaymat A, et al. The role of drains in lumbar spine fusion. World Neurosurg. 2012; 77(3-4):564-568.

19. Takemoto RC, Lonner B, Andres T, et al. Appropriateness of twenty-fourhour antibiotic prophylaxis after spinal surgery in which a drain is utilized: a prospective randomized study. J Bone Joint Surg Am. 2015;97(12):979-86.

20. Ovadia D, Drexler M, Kramer M, Herman A, Lebel DE. Closed wound subfascial suction drainage in posterior fusion surgery for adolescent idiopathic scoliosis: a prospective randomized control study. Spine (Phila Pa 1976). 2019;44(6):377-383.

21. Diab M, Smucny M, Dormans JP, et al. Use and outcomes of wound drain in spinal fusion for adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2012;37(11):966-973.

22. Kumar, V, Singh A, Waliullah S, Kumar D. Analysis of efficacy in postoperative use of closed suction drain in cases of traumatic dorsolumbar spine injury. J Orthoped Trauma Rehabil. 2019;1(1):1-5.

23. Sohn S, Chung CK, Kim CH. Is closed-suction drainage necessary after intradural primary spinal cord tumor surgery? Eur Spine J. 2013;22(3):577–583.

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IMAGING SAFETY

From The CORE Institute in Phoenix, Arizona.

Strategies to Reduce Radiation Exposure During Spine Surgery Brandon P. Hirsch, MD

During the past 2 decades, spine surgery has become increasingly reliant on intraoperative imaging.1 This trend has been driven by an evolution in minimally invasive techniques that preserve muscular attachments to the spine. Less invasive surgical techniques do not allow for visualization of the traditional topographic landmarks used to place instrumentation and instead rely on real-time images to guide surgical instruments. Despite recent advances in computerized navigation and robotics, fluoroscopy continues to be a widely used intraoperative imaging modality and imparts radiation exposure to the surgeon and operating room staff.

Health hazards related to radiation exposure during spine surgery have been well studied and include carcinogenesis, cataract formation, and mutagenesis within gonadal/hematopoietic tissue. 2 Hematopoietic, colon, lung, breast, and thyroid tissue are among the most radiosensitive tissue types.3 Multiple studies have demonstrated the increased risk of malignancy in surgeons who utilize fluoroscopy.4–6 To date, no large scale epidemiological study focused on cancer risk in spine surgeons has been performed.

However, a widely quoted study conducted at an orthopaedic hospital in 2005 found a 29% incidence of cancer among orthopaedic surgeons at the facility over a 24-year period,

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compared with 4% in other employees at the facility.7 Although the hospital was known to have substandard radiation protection practices in place during the study period, the incidence is alarming.

The International Commission on Radiological Protection sets radiation safety standards and recommends a maximum occupational radiation exposure of 20 millisievert (mSv) per year to both the body and the eye.8 Cumulative exposure of 1 Sievert (Sv) is thought to correspond to an absolute lifetime risk of 5% mortality from malignancy. 9 The precise exposure corresponding to increased risk of cataract formation is controversial, with most studies suggesting a threshold lifetime dose of 0.5 Sv.10 Multiple strategies can reduce radiation exposure to the spine surgeon. At a minimum, surgeons who utilize fluoroscopy during instrumentation should wear circumferential lead aprons with properly fit thyroid shields and leaded eyewear. Surgeons should avoid folding aprons as this can create defects in the shielding material. Protective aprons should be inspected on a yearly basis at a minimum.

Because ionizing radiation follows an inverse square law, surgeons should always attempt to position themselves as far from the patient as possible during fluoroscopy. Standing at a distance of just 2 feet from the beam source can lower exposure by a factor of 8.

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Specific settings on the C-arm can also be modified to improve radiation safety. Using “low dose” settings as well as pulsed rather than continuous f luoroscopy further reduces exposure. A 2013 study of minimally invasive transforaminal interbody fusion demonstrated an 80% reduction in fluoroscopy time per case compared with other published series by using a low-dose, pulsed technique.11 Collimation involves the use of lead shielding to narrow the radiation beam to only the area of interest. By doing this, the amount of scatter radiation that reaches the surgical team is significantly reduced.

Scatter radiation is the secondary radiation that is produced when the primary radiation beam interacts with the object being imaged (ie, the patient). Scatter accounts for the majority of radiation exposure to the surgeon in the operating room. A recent prospective study of spinal endoscopy demonstrated greater than 50% reduction in radiation exposure with the use of collimation.12 The type of C-arm used also impacts radiation exposure. Fluoroscopy machines can be categorized into two types: analog and digital. Analog fluoroscopy machines use a high-intensity x-ray beam to produce an image, which is then amplified by an image intensifier and captured by a camera. Digital fluoroscopy machines use a flat-panel

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detector to capture the radiographic image, which is then converted into a digital signal and displayed on a monitor. Due to the nature of the technology, digital machines use far less exposure to generate a high-quality image. While digital f luoroscopy became commercially available in the early 2000s, analog machines still remain in use today at many facilities due to cost considerations and lack of awareness regarding benefit. Digital fluoroscopy machines can lower radiation exposure by as much as 90%.13,14 Maintenance of protective equipment is also essential to limit radiation exposure to the surgeon. Lead aprons and thyroid shields should be inspected regularly for signs of wear and tear, such as cracks or

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holes. Lead aprons should be hung on a specially designed rack to prevent creasing or folding, which can cause the lead lining to break down over time. The aprons should be stored in a dry, cool location away from direct sunlight, as heat and moisture can also damage the lead lining. Lead aprons should be replaced periodically, even if they appear to be in good condition. The American Society of Radiologic Technologists recommends replacing lead aprons every 2 to 3 years, or sooner if they are damaged or show signs of wear.

Spine surgeons should be aware of the risks of ionizing radiation related to intraoperative imaging and take steps to minimize their exposure. Multiple strategies for exposure

reduction exist, including wearing and appropriately maintaining protective equipment, maximizing distance from the imaging device and patient, limiting unnecessary image acquisition, and using modern fluoroscopy technology and settings to minimize scatter radiation. Dosimeters should be used by all spine surgeons and readings should be reviewed regularly. Further adoption of navigation technology and robotics that does not require the surgeon to be within range of the patient during image acquisition is certain to lower radiation-related risks for spine surgeons in the future. As this technology becomes more commonplace, future study will need to consider its impact on radiation risks imparted to the patient. n

References 1. Yu E, Khan SN. Does less invasive spine surgery result in increased radiation exposure? A systematic review. Clin Orthop Relat Res. 2014;472:1738-1748.

2. Hadelsberg UP, Harel R. Hazards of ionizing radiation and its impact on spine surgery. World Neurosurg. 2016;92:353-359.

3. Hayda RA, Hsu RY, DePasse JM, Gil JA. Radiation exposure and health risks for orthopaedic surgeons. J Am Acad Orthop Surg. 2018;26(8):268-277.

4. Srinivasan D, Than KD, Wang AC, et al. Radiation safety and spine surgery: systematic review of exposure limits and methods to minimize radiation exposure. World Neurosurg. 2014;82(6):1337-1343.

5. Mastrangelo G, Fedeli U, Fadda E, Giovanazzi A, Scoizzato L, Saia B. Increased cancer risk among surgeons in an orthopaedic hospital. Occup Med (Lond). 2005;55(6):498-500.

6. Chou LB, Lerner LB, Harris AHS, Brandon AJ, Girod S, Butler LM. Cancer prev-

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alence among a cross-sectional survey of female orthopedic, urology, and plastic surgeons in the United States. Womens Health Issues. 2015;25(5):476-481.

7. Mastrangelo G, Fedeli U, Fadda E, Giovanazzi A, Scoizzato L, Saia B. Increased cancer risk among surgeons in an orthopaedic hospital. Occup Med (Lond). 2005;55(6):498-500.

8. Clement CH, Stewart FA, Akleyev A V., et al. ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs—threshold doses for tissue reactions in a radiation protection context.

Ann ICRP. 2012;42(1-2)1-322.

9. Pierce DA, Preston DL. Radiation-related cancer risks at low doses among atomic bomb survivors.

Radiat Res. 2000;154(2):178-186.

10. Vano E, Kleiman NJ, Duran A, et al. Radiation cataract risk in interventional cardiology personnel.

Radiat Res. 2010;174(4):490-495.

11. Clark JC, Jasmer G, Marciano FF, et al. Minimally invasive transforaminal lumbar interbody fusions and fluoroscopy: a low-dose protocol to minimize ionizing radiation.

Neurosurg Focus. 2013;35:E8.

12. Erken HY, Yilmaz O. Collimation reduces radiation exposure to the surgeon in endoscopic spine surgery: a prospective study. J Neurol Surg A Cent Eur Neurosurg. 2022;83:6-12.

13. Lee JJ, Venna AM, McCarthy I, et al. Flat panel detector C-arms are associated with dramatically reduced radiation exposure during ureteroscopy and produce superior images.

J Endourol. 2021;35:789-794.

14. Tzanis E, Raissaki M, Konstantinos A, et al. Radiation exposure to infants undergoing voiding cystourethrography: The importance of the digital imaging technology. Phys Med. 2021;85:123-128.

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From Rush University Medical Center in Chicago, Illinois.

NEW TECHNOLOGY

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3D Printing in Spine Surgery Is the Hype Real?

Although 3-dimensional (3D) printing, or additive manufacturing (AM), was first introduced in the 1980s, it really gained traction in spine surgery over the past 2 decades.1 In its infancy, 3D printing was used as a means to develop custom visual aids for preoperative planning. However, with the spread of popular terms, such as “customized,” “patient-specific,” and “personalized medicine,” 3D-printed osteotomy templates, cutting guides, pedicle screw guides, and even implants have begun to flood the market.

Custom i zed su rg ica l i mpla nt s ma ke sense—we can forgo many unnecessar y costs such as sterilizing and providing excessive items that do not match the needs

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of each patient. Furthermore, Arash J. Sayari, MD preoperatively planned implants may allow for more expeditious surgery, as surgeons can minimize the time it takes to template and trial sizing options.2 On the other hand, off-the-shelf (OTS) implants come in a variety of sizes, and one must question whether there are any significant differences in outcomes that would justify the increased cost of customized implants.

Current Evidence On one end of the spectrum, 3D printing in tumor surgery seems to make the most sense, but the literature is limited mostly to case reports.3,4 For example, AM has been used to address kyphotic deformities involved in excision of a hemangioendothelioma by matching a cage to the patient’s cranial and caudal endplates. 5 Similarly, Chin et al used a 3D-printed implant to not only fill the gap following an en bloc spondylectomy for a giant cell tumor but also to fit into the patient’s prior instrumented construct.6 Increased costs can be justified to match the unique anatomy, often involving the increased removal of native soft tissue and bone, or in cases of bone loss from osteoporosis or pat hologic

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NEW TECHNOLOGY

fractures.7 A more detailed review of 13 spine tumor cases in which a 3D-printed implant was successfully used highlights the potential utility in a specific cohort of patients with unique anatomic variants.8,9 Anatomic anomalies exist outside of tumor surgery, however. Even asymmetric anatomic wear of an endplate can change contact pressures of a surgical implant, directly affecting fusion rates.10 As such, limited bony work and reduced risk of endplate violation can contribute to postoperative outcomes.

Similarly, pelvic incidence–lumbar lordosis (PI-LL) mismatch has been linked to postoperative outcomes and adjacent segment degeneration,11-13 increasing the potential utility of 3D-printed implants directed toward achieving improved deformity correction.

Advantages of 3D-Printing in Spine Surgery 3D-printed spine implants, like OTS implants, are made of alloys, including titanium, Polyether Ether Ketone (PEEK), cobalt-chromium, and ceramics. The benefit of 3D printing with these alloys involves the freedom of design.

As in tumor surgery, most metal implants are made via an AM process called powder bed fusion, which allows for the building of complex structures that would be otherwise cost-prohibitive to build using conventional manufacturing techniques.

The AM process also helps with osseointegration, as it allows for a more simplified addition of porous surfaces. This offers developers an easier way to manage load transfer, surface area coverage, and mechanical properties while optimizing bone

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integration.14 In conventional methods, more significant post-processing steps to add such porosity contribute to increased costs.

The Federal Drug Administration 510(k) mechanism of implant approval also offers companies a unique and useful way to more readily introduce new, yet similar, products to the market. In AM, manufacturing methods may differ, but as long as the fundamental geometry remains the same as existing devices, there may be an accelerated approval process. This allows manufacturing companies to attempt various design features to an existing device with only minimal changes in the production process. In addition to manufacturing changes, 3D-printed implants allow for detailed data collection and computing analysis to evaluate how microscopic changes can have macroscopic effects—potentially slowing the course of pathology such as adjacent segment degeneration.15

Challenges of 3D-Printing in Spine Surgery The most relevant limitation surrounding 3D printing in spine surgery involves regulation.

The powder bed fusion process involves various parameters which may be intentionally or unintentionally varied. These parameters include printing strategies, powder particle size, purity of the alloy powder, laser beam versus electron beam usage, beam power, and subsequent heat treatments. Because there are only minimal requirements for the alloy microstructure in the 3D printing process, further variations may be seen in the mechanical and electrochemical properties of each utilized alloy.

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Furthermore, studies have demonstrated that 3D-printed devices have an inferior implant-alloy microstructure when compared to conventional wrought or cast alloys.16 This undeniably has a direct effect on the corrosion and fatigue properties of each implant.

Hot cracks, build defects and gas pores, and even alterations in implant brittleness, can result in catastrophic failure and fracture.

Fortunately, most impurities can be removed with post-processing and heating, though the lack of regulation and standardization

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limits the number of companies likely implementing this.

Final Thoughts The enthusiasm surrounding 3D implants and their ability to address in vivo variations in bony and soft tissue anatomy, size, and pathology is warranted. The benefits have been demonstrated in the literature to support its use. However, there is far less attention paid to the quality of manufacturing with no checks-and-balances in place evaluating the alloy use of 3D implants. n

References 1. Sheha ED, Gandhi SD, Colman MW. 3D printing in spine surgery. Ann Transl Med. 2019;7(Suppl 5):S164.

2. Wallace N, Schaffer NE, Aleem IS, Patel R. 3D-printed patient-specific spine Implants: a systematic review.

Clin Spine Surg. 2020;33(10):400-407.

3. Burnard JL, Parr WCH, Choy WJ, Walsh WR, Mobbs RJ. 3D-printed spine surgery implants: a systematic review of the efficacy and clinical safety profile of patient-specific and off-the-shelf devices. Eur Spine J. 2020;29(6):1248-1260.

4. Wilcox B, Mobbs RJ, Wu AM, Phan K. Systematic review of 3D printing in spinal surgery: the current state of play. J Spine Surg. 2017;3(3):433-443.

5. Choy WJ, Mobbs RJ, Wilcox B, Phan S, Phan K, Sutterlin CE 3rd.

Reconstruction of thoracic spine using a personalized 3D-printed vertebral body in adolescent with T9 primary bone tumor. World Neurosurg. 2017;105:1032.e13-e1032.e17.

6. Chin BZ, Ji T, Tang X, Yang R, Guo W. Three-level lumbar en bloc spondylectomy with three-dimensional-printed vertebrae reconstruction for recurrent giant cell tumor. World Neurosurg. 2019;129:531-537.e1.

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7. Siu TL, Rogers JM, Lin K, Thompson R, Owbridge M. Custom-made titanium 3-dimensional printed interbody cages for treatment of osteoporotic fracture-related spinal deformity.

World Neurosurg. 2018;111:1-5.

8. Girolami M, Boriani S, Bandiera S, et al.

Biomimetic 3D-printed custom-made prosthesis for anterior column reconstruction in the thoracolumbar spine: a tailored option following en bloc resection for spinal tumors: preliminary results on a case-series of 13 patients.

Eur Spine J. 2018;27(12):3073-3083.

9. Li X, Wang Y, Zhao Y, Liu J, Xiao S, Mao K. Multilevel 3D printing implant for reconstructing cervical spine with metastatic papillary thyroid carcinoma.

Spine. 2017;42(22):E1326-E1330.

10. Mobbs RJ, Parr WCH, Choy WJ, McEvoy A, Walsh WR, Phan K. Anterior lumbar interbody fusion using a personalized approach: is custom the future of implants for anterior lumbar interbody fusion surgery? World Neurosurg.

Published online January 8, 2019. doi:10.1016/j.wneu.2018.12.144 11. Rothenfluh DA, Mueller DA, Rothenfluh E, Min K. Pelvic incidence-lumbar lordosis mismatch predisposes to adjacent segment disease after lumbar spinal fusion. Eur Spine J. 2015;24(6):1251-1258.

12. Tempel ZJ, Gandhoke GS, Bolinger BD, et al. The influence of pelvic incidence and lumbar lordosis mismatch on development of symptomatic adjacent level disease following single-level transforaminal lumbar interbody fusion.

Neurosurgery. 2017;80(6):880-886.

13. Senteler M, Weisse B, Snedeker JG, Rothenfluh DA. Pelvic incidence-lumbar lordosis mismatch results in increased segmental joint loads in the unfused and fused lumbar spine.

Eur Spine J. 2014;23(7):1384-1393.

14. Kelly CN, Wang T, Crowley J, et al.

High-strength, porous additively manufactured implants with optimized mechanical osseointegration.

Biomaterials. 2021;279:121206.

15. Serra T, Capelli C, Toumpaniari R, et al. Design and fabrication of 3D-printed anatomically shaped lumbar cage for intervertebral disc (IVD) degeneration treatment. Biofabrication. 2016;8(3):035001.

16. Neto MQ, Radice S, Hall DJ, Mathew MT, Mercuri LG, Pourzal R. Alloys used in different temporomandibular joint reconstruction replacement prostheses exhibit variable microstructures and electrochemical properties. J Oral Maxillofac Surg. 2022;80(5):798-813.

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From the Department of Orthopedic Surgery, Division of Spine Surgery, Midwest Orthopaedics at Rush, Chicago, Illinois.

Variability in Spine Surgery Training Cameron Kia, MD

The route to becoming a spine surgeon, whether through orthopedic or neurosurgery residency, requires extensive and r igorous t raining. 1 A lt hough several similarities do exist, the minimum requirements and the quantit y and qualit y of cases Gregory Lopez, MD that trainees are exposed to have been shown to vary between and within subspecialty groups. 2-4 This has led to a recent focus on whether this variation in training has clinical implications on patient outcomes 5-7 and whether minimizing these differences could help the delivery of spine care in today’s rapidly evolving health care system. 8 This variation in training has been amplified by the COVID-19 pandemic, 9-11 which demonstrated a significant reduction in trainees’ case logs.11 The suspension of elective surgery and deployment of trainees to assist in other subspecialties has only f ur t her emphasized t he impor tance of fellowships in preparing future spine surgeons.12 With increasing numbers of spine surgeries and applicants applying into the subspecialty over the past 10 years,13,14 the demand for well-trained spine surgeons has become quite evident. This review will discuss the variations in training that exist in the current model,15 as well as potential

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changes that could positively affect the way spine surgeons deliver care to their patients.

Orthopedic and Neurosurgery Residency Training The Accreditation Council for Graduate Medical Education (ACGME) requires both orthopedic and neurosurgery residents to complete a minimum number of cases in both adult and pediatric spine for graduation.16,17 Despite this similarity, the emphasis on spine surgery in orthopedics is significantly less for graduation. Currently, of the 15 case categories required for by the ACGME, only one is within the field of spine surgery. In addition, of the 20 orthopedic milestones evaluated by program directors, none are devoted specifically to spine surgery.18 Daniels et al further examined this variability in training by comparing case logs bet ween orthopedic and neurosurgical residents. 2 The authors found that the average number of spine surgeries performed during orthopedic residency was 160 cases compared to 375 in neurosurgical training.2 Variations also existed within each cohort, as the top 90% of orthopedic residents by volume had nearly a 13-fold higher exposure to spinal arthrodesis compared to the bottom 10% in the same cohort. 2 Although both specialties are expected to have a similar understanding and

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technique in treating spinal disorders, there appears to be a significant variation in the t ypes of cases that residents are exposed too. 2,3 Orthopedic residents tend to be exposed to a greater number of t horacolumbar defor mit y cases and fewer cervical and intradural patholog y cases compared to t heir neurosurgical colleagues. 3 Dvorak et al surveyed senior orthopedic and neurosurgery residents to compare their self-perceived confidence in performing 25 different spine procedures. 3 T he aut hors fou nd t hat neu rosu rg ica l residents had significantly higher dedicated exposure to spine (37% compared to 16%) with higher levels of confidence in all 25 procedures. 3 This variation in training has only increased over the past

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10 years,19 emphasizing the importance of spine fellowships.

Spine Fellowship Although not required, the spine fellowship has become increasingly popular for both orthopedic surgeons and neurosurgeons.2,20 This extra year of training can be critical, as it provides an opportunity to correct for any deficiency in case exposure that was present during residency. With an estimated minimum of 250 spine cases required before starting practice, this is especially important for orthopedic residents.12,21 Silvestre et al compared the spine case volume of fellows to graduating orthopedic residents and found nearly a 4-fold increase in total spine cases in 1 year of fellowship compared to

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residency training. 22 Regardless of subspecialty, Konczalik et al found that those who did a spine fellowship were significantly more likely to feel comfortable with complex deformity and trauma compared to those who did not complete a fellowship. 21 Despite these many benefits, there continues to be some variation in training even within the spine fellowships. Malik et al analyzed case logs of orthopedic spine fellows between 2010 and 2015, noting an overall decline in pediatric cases performed during these years.23 The greatest variation was in deformity cases, with the top 90th percentile in cases logged having at least 43 deformity procedures, compared to zero in the bottom 10th percentile cohort.23 While these difference may just reflect geographic location and physician practice, it does open the door for a more standard requirement from the ACGME for fellowships and for the potential collaboration between spine departments.

Future Considerations Although several gaps between neurosurgical and orthopedic residency training can be f illed w it h fellowship t raining, during the global pandemic, many fellows faced decreased operative time and case volume. 9,12 In addition, having 2 routes to the same specialty with such variation in training and technique can lead to potential downstream effects on patient outcomes.

As such, the role of either an integrated or more spine-focused training in residency could be considered for future surgeons.

Daniels et al proposed the development

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of a spine residency, with dedicated focus on operative and nonoperative treatment modalities of spinal disorders.24 This would allow integration of both orthopedic and neurosurgical techniques to fully optimize physicians to start practice after residency.

W hile this would be ideal, institutional politics and economic barriers have made this difficult to come to fruition. 24 In a recent meta-ana lysis comparing orthopedic to neurosurgical surgeon outcomes, the only differences found were a lower transfusion rate and a longer operative time by neurosurgeons among several studies.15 This difference may be due to technique, as neurosurgeons require meticulous hemostasis during intra-cranial surger y; however, there were no differences in overall complications or 30-day readmission rates between cohorts.15 The authors did note that improvement in surgical outcome in certain studies were those from high volume providers or those who had department collaboration on complex cases.15,25 This highlights the importance of greater collaboration between neurosurgical and orthopedic surgeons to provide more consistent patient outcomes, research findings, and education to trainees.

Conclusion The current 2 routes to spine surgery are often vastly different in residency training, w it h limited cross-over in interact ion.

With resident work ing hours becoming limited, optimizing spine education has become critical for future trainees. Limiting variation in quantity and spectrum

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of cases observed, especially in residency, can provide a much greater confidence to graduating residents. While studies have not shown a difference between subtypes, a fellowship has been shown to significantly

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increase the confidence of a provider in performing several spine procedures. A future spine residency would be a large undertaking, but it would help fill the gaps of the current model. n

References 1. Lad M, Gupta R, Para A, et al. An ACGME-based comparison of neurosurgical and orthopedic resident training in adult spine surgery via a case volume and hours-based analysis. J Neurosurg Spine. 2021;35:553–563.

2. Daniels AH, Ames CP, Smith JS, Hart RA. Variability in spine surgery procedures performed during orthopaedic and neurological surgery residency training: an analysis of ACGME case log data. J Bone Joint Surg Am. 2014;96:e196.

3. Dvorak MF, Collins JB, Murnaghan L, et al.

Confidence in spine training among senior neurosurgical and orthopedic residents.

Spine (Phila Pa 1976). 2006;31:831–837.

4. Pham MH, Jakoi AM, Wali AR, Lenke LG. Trends in spine surgery training during neurological and orthopaedic surgery residency: a 10-year analysis of ACGME case log data. J Bone Joint Surg Am. 2019;101:e122.

5. Baek J, Malik AT, Khan I, et al. Orthopedic versus neurosurgery–understanding 90-day complications and costs in patients undergoing elective 1-level to 2-level posterior lumbar fusions by different specialties. World Neurosurg. 2019;131:e447–e453.

fusion. Spine. 2019;44:163–168.

9. 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.

10. Swiatek PR, Weiner JA, Butler BA, et al. Assessing the early impact of the COVID-19 pandemic on spine surgery fellowship education. Clin Spine Surg. 2021;34:E186-E193.

11. Munro C, Burke J, Allum W, Mortensen N. Covid-19 leaves surgical training in crisis. BMJ. 2021;372:n659.

12. Dowdell JE, Louie PK, Virk S, et al. Spine fellowship training reorganizing during a pandemic: Perspectives from a tertiary orthopedic specialty center in the epicenter of outbreak. Spine J. 2020;20:1381-1385.

13. Lopez CD, Boddapati V, Lombardi JM, et al. Recent trends in Medicare utilization and reimbursement for lumbar spine fusion and discectomy procedures. Spine J. 2020;20:1586–1594.

14. Ruddell JH, Eltorai AEM, DePasse JM, et al. Trends in the orthopaedic surgery subspecialty fellowship match: assessment of 2010 to 2017 applicant and program data.

J Bone Joint Surg Am. 2018;100:e139.

6. Esfahani DR, Shah H, Arnone GD, et al.

Lumbar discectomy outcomes by specialty: a propensity-matched analysis of 7464 patients from the ACS-NSQIP database.

World Neurosurg. 2018;118:e865–e870.

15. Lambrechts MJ, Canseco JA, Toci GR, et al. Spine surgical subspecialty and its effect on patient outcomes – a systematic review and meta-analysis. Spine. 2023;48(9):625-635.

7. Kim BD, Edelstein AI, Hsu WK, et al. Spine surgeon specialty is not a risk factor for 30-day complication rates in single-level lumbar fusion. Spine. 2014;39:E919–E927.

16. Review Committee for Orthopaedic Surgery. Orthopaedic surgery minimum numbers. Accreditation Council for Graduate Medical Education. September 10, 2014. https://www.acgme.org/ globalassets/pfassets/programresources/260_ors_case_log_minimum_numbers.pdf. Accessed April 16, 2023.

8. Snyder DJ, Neifert SN, Gal JS, et al.

Assessing variability in in-hospital complication rates between surgical services for patients undergoing posterior cervical decompression and

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17. Accreditation Council for Graduate Medical Education. ACGME program require-

ments for graduate medical education in neurological surgery. July 1, 2013. http:// www.acgme. org/acgmeweb/Portals/0/ PFAssets/ProgramRequirements/160_neurological_ surgery_07012013.pdf.

18. Accreditation Council for Graduate Medical Education. Orthopaedic surgery milestones. https://www.acgme. org/specialties/orthopaedic-surgery/ milestones/. Accessed April 1, 2023.

19. Pham MH, Jakoi AM, Wali AR, Lenke L. Trends in spine surgery training during neurological and orthopaedic surgery residency. J Bone J Surg Am. 2019;101:e122.

20. Chandra A, Brandel MG, Yue JK, et al. Trends in neurosurgical fellowship training in North America over two decades 1997 to 2016. Neurosurgery. 2019;66(Suppl 1):310-326.

21. Konczalik W, Elsayed S, Boszczyk B. Experience of a fellowship in spinal surgery: a quantitative analysis. Eur Spine J. 2014;23(Suppl 1):S40–S54.

22. Silvestre J, Wu HH, Thompson, TL, Kang JD. Utility of spine surgery fellowship training for orthopaedic surgeons in the United States. J Am Acad Orthop Surg. 2023;31:335-340.

23. Malik AT, Kim J, Ahmed U, Yu E, Khan SN. Understanding the trends and variability in procedures performed during orthopedic spine surgery fellowship training: an analysis of ACGME case log data.

J Surg Educ. 2021;78(2):686-693.

24. Daniels AH, Ames CP, Garfin SR, et al. Spine surgery training: Is it time to consider categorical spine surgery residency? Spine J. 2015;15:1513-1518.

25. Bauer JM, Yanamadala V, Shah SA, et al.

Two surgeon approach for complex spine surgery: rationale, outcome, expectations, and the case for payment reform. J Am Acad Orthop Sur. 2019;27:e408–e413.

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