Vertebral Columns, Spring 2022

COLUMNS

Anatomical Considerations of Prone Single-Position Lateral Lumbar Interbody Fusion

International Society for the Advancement of Spine Surgery

SPRING 2022

Vertebral

INSIDE

Facet Cyst: To Fuse or Not To Fuse?

History, Efficacy, and Safety of the Barricaid Annular Closure Device: A Brief Commentary Multimodal Pain Management After Spine Surgery Hypermobility Following Cervical Disc Arthroplasty

PLUS

Reimbursement Trends in Spine Surgery

Editor in Chief

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EDITORIAL

Kern Singh, MD

Reimbursement Trends in Spine Surgery

Editorial Board Peter Derman, MD, MBA

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LUMBAR SPINE

Brandon Hirsch, MD

Anatomical Considerations of Prone Single-Position Lateral Lumbar Interbody Fusion

Sravisht Iyer, MD Yu-Po Lee, MD Sheeraz Qureshi, MD, MBA

DEGENERATION Facet Cyst: To Fuse or Not To Fuse?

MEDICAL DEVICES History, Efficacy, and Safety of the Barricaid Annular Closure Device: A Brief Commentary

Managing Editor Audrey Lusher Designer CavedwellerStudio.com

PAIN MANAGEMENT Multimodal Pain Management After Spine Surgery

PATIENT OUTCOMES Hypermobility Following Cervical Disc Arthroplasty Vertebral Columns is published quarterly by the International Society for the Advancement of Spine Surgery. ©2022 ISASS. All rights reserved.

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

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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-2022

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

EDITORIAL

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Reimbursement Trends in Spine Surgery Kevin C. Jacob, BS

Madhav R. Patel, BS

Alexander W. Parsons, MS

Despite being consistently positioned as a top 5 specialty for earnings, only about half of full-time practicing orthopedic surgeons feel adequately compensated. In 2020, 60% of orthopedic surgeons reported being satisfied with their compensation compared to only 52% in 2022.1,2 Furthermore, 67% of orKern Singh, MD thopedic surgeons believe they should see a pay increase of at least 11%. 3 The question as to why nearly half of all practicing orthopedic surgeons are dissatisfied with their compensation may be less about the actual dollar amount and more about the methods behind how their compensation is determined. In 2018, more than half of orthopedic surgeons stated that the ever-changing rules and regulations that govern the way they practice, along with the variability of reimbursement coupled with its declining trend, remain the most challenging part of their specialty’s outlook. 3 More recently, orthopedic surgeons reported that 18% of their claims were denied or had to be resubmitted, adding frustration and additional administrative costs to their practices.1 Decreasing reimbursement and its uncertainty have kept surgeons awake at night for years. Prior to 1992, before the resource-based value system of physician payment, there

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EDITORIAL

From 2000 to 2021, inflation, as measured by the consumer price index, increased by nearly 60%; however, the reimbursement rate in spinal procedures increased by only 5.36% was an annual rate increase of 10.8% on physician services.4 The 2007 publication on Medicare Physician Reimbursement found a 28% decline in reimbursement trends for orthopedics from 1992 to 2007 when adjusting for inflation.4 Even without adjustments for inflation, reimbursement over the same period increased by only 4%, which pales in comparison to the increase rates prior to the changes established in 1992.4 Today, declining reimbursement to surgeons along with increased inflation costs and expensive technological advancement brings different complications.

During discussions on healthcare reform in 2010, orthopedic surgeons were primarily concerned about moving funding from specialty care to primary care facilities and the associated revenue loss. In 2010, the country faced one of the most significant recessions in modern history. The weakened economy, lost jobs and health benefits lead to a decrease in elective procedures, further decreasing revenue. 5 As part of the actions taken around 2010 to curb the unsustainable growth in healthcare-related costs, reforms specifically targeted physician reimbursement.6 The issue here was reducing reimbursement while failing to reduce operating expenditures, which have

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inevitably left loose ends and issues with sustainability, particularly in orthopedic spine procedures.6 The most recent information published on reimbursement of spinal procedures from 2000-2021 confirms the current downward trend in reimbursement amounts.7 From 2000 to 2021, inflation, as measured by the consumer price index, increased by nearly 60%; however, t he reimbursement rate in spinal procedures increased by only 5.36%.7 When Haglin et al adjusted this rate for inflation for the procedures reviewed, average reimbursement for spinal procedures decreased by 33.8%.7 Further complicating matters is the geographic variation in reimbursement scales.

Overall, state-by-state comparisons found all states to have negative reimbursement rates over the 2 decades being analyzed, with Wisconsin being the most affected (-40.8%) and Montana the least (-31.4%).7 Declining physician pay and Medicare reimbursement, however, don’t align with the value many patients believe their surgeon should be reimbursed for. In 2013, Badlani et al published a report on patient perceptions of spine surgeon reimbursement and found their patients believed total compensation should be increased by 10 to 20 times more than current Medicare reimbursement amounts.6 The divisions and disconnect between the payer, the patient, and the physician continues to grow. The declining reimbursement and coverage offered through Medicare continues to be a burden to both the patient and the surgeon.

Patients face increased out-of-pocket costs for their care. Patients utilizing Medicare

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EDITORIAL

spend nearly 30% of their income on outof-pocket costs. 8 The consequences of increasing out-ofpocket costs is decreasing adherence to treatment plans, skipped appointments, and fewer elective procedures in the elderly population. 8 Surgeons also face the challenge of what to do with Medicare. The A ARP (American Association of Retired Persons) is uniquely positioned to understand not only the hesitancy of the patient to pursue medical care but also the physician struggling to make ends meet and the ensuing contemplation of how many and for how long they can accept patients utilizing Medicare plans. 8 The last thing the health care system needs is spine surgeons walking away from Medicare and poorly paying insurance programs in frustration with reimbursement policies. However, recent survey data of orthopedic surgeons found that 36% of orthopedic surgeons believe they will not accept insurers that pay poorly. 3 It appears to be more of a question of when, not if, orthopedic surgeons will cease to accept Medicare, potentially leaving elderly patients without options for orthopedic care.

Furthermore, these actions have caused def icits in ot her areas of spine surger y practice in addition to slowing the potential earnings for physicians and their teams. In 2004, the chief medical editor of Orthopedics Today discussed declining reimbursement with leaders in the academic orthopedic spine community. 9 Specifically, he asked how declining reimbursement rates would affect specific areas of technological developments in spine surgery. The responses

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to this question, almost 20 years old now, sou nds eer i ly fa m i l ia r. T he su rgeons’ responses included limiting the hire of orthopedic spine surgeons to a hospital in need of orthopedic care due to “losing too much money” on the spine surgeons they already employ. 9 Additional answers to the challenges of decreasing reimbursements led to the idea of creating a committee to evaluate and debate whether the systems, products, and implants were genuinely worth the cost and whether patients and surgeons could manage with older technology instead. Another surgeon stated that institutions would need to restrict what instrumentation and new technologies spine surgeons would be allowed to use due to budget constraints. 9 The addition of committees leads to increased time away from patient care and additional levels of bureaucracy, which is already a significant problem in all of healthcare. Hospital care

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EDITORIAL

and other administrative costs make up a significant majority of healthcare spending in the US, while physician services had the lowest rate of increase from 2018 to 2019.10,11 Federal policies often target physician reimbursement as the means to reign in excessive healthcare expenditure.12 However, even a superficial analysis of healthcare spending reveals that physicians are not the problem and should not receive limited reimbursement in any field, particularly one that that is highly regarded by not only patients but also technology and business industries.

Limiting reimbursement limits the advancement of spine surgery as a whole; it becomes a limiting factor in advancing patient care; the limiting factor in training for residents, fellows, and young surgeons; and the limiting factor in creating and affording

innovative new technologies. Spine surgeons stand as a uniquely tight-knit group whose collective voice could challenge the status quo to improve all areas of medicine.

Despite all of these factors, the vast majority of orthopedic surgeons surveyed are inclined to continue taking new and current Medicare and Medicaid patients,1,3 which demonstrate the attitudes many spine surgeons have toward caring for their patients despite the complex and often frustrating daily challenges with reimbursement and regulations. Spine surgeons continually prove their worth and value to those they serve and should only be faulted for not saying or doing more to combat declining reimbursement as it hurts not only the surgeons, but their patients and the future of the field as well. n

References 1. Kane L. Medscape Physician Compensation Report 2020. Published online May 14, 2020. https://www. medscape.com/slideshow/2020-compensation-overview-6012684 2. Kane L. Medscape Physician Compensation Report 2022: Incomes Gain, Pay Gaps Remain. Published online April 15, 2022. https://www. medscape.com/slideshow/2022-compensation-overview-6015043 3. Kane L. Medscape Physician Compensation Report 2018. Published online 2018. https://www.medscape.com/slideshow/2021-compensation-overview-6013761 4. Hariri S, Bozic KJ, Lavernia C, Prestipino A, Rubash HE. Medicare physician reimbursement: past, present, and future. J Bone Joint Surg Am. 2007;89(11):2536-2546.

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5. Dunn L. 11 Challenges and Opportunities for Orthopedic and Spine Practices in 2010. Becker’s ACS Review. January 4, 2010. https://www.beckersasc. com/news-analysis/11-challenges-and-opportunities-for-orthopedic-and-spine-practices-in-2010.html

9. Jackson DW. Reimbursements for spine surgical implants a growing problem. Orthopedics Today.

May 1, 2004. https://www.healio. com/news/orthopedics/20120325/ reimbursements-for-spine-surgical-implants-a-growing-problem

6. Badlani N, Foran JR, Phillips FM, et al.

Patient perceptions of physician reimbursement for spine surgery. Spine (Phila Pa 1976). 2013;38(15):1288-1293.

10. Rama A. Policy Research Perspectives: National Health Expenditures, 2019: Steady Spending Growth Despite Increases in Personal Health Care Expenditures in Advance of the Pandemic. American Medical Association. 2021. https://www. ama-assn.org/system/files/2021-05/ prp-annual-spending-2019.pdf

7. Haglin JM, Zabat MA, Richter KR, et al.

Over 20 years of declining Medicare reimbursement for spine surgeons: a temporal and geographic analysis from 2000 to 2021 [published online ahead of print March 25, 2022]. J Neurosurg Spine. doi:10.3171/2022.2.SPINE211368 8. Bozic KJ, Cramer B, Albert TJ. Medicare and the orthopaedic surgeon: challenges in providing, financing, and accessing musculoskeletal care for the elderly. J Bone Joint Surg Am. 2010;92(6):1568-1574.

11. Norbeck TB. Drivers of health care costs: a Physicians Foundation white paper--first of a three-part series. Mo Med. 2013;110(1):30-35.

12. Benzil DL, Zusman EE. Defining the value of neurosurgery in the new healthcare era. Neurosurgery. 2017;80(4S):S23-S27.

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

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Anatomical Considerations of Prone Single-Position Lateral Lumbar Interbody Fusion Since the initial conceptualization of lumbar arthrodesis in the early 20th century, fusion of the lumbar spine has been widely explored, leaving modern spine surgeons with several different approaches for lumbar interbody fusion (LIF). Traditionally, the anterior (ALIF) approach has been considered optimal for restoration of lordosis due to its direct access to the anterior spinal column and disc space, allowing for the placement of larger intervertebral cages. The ALIF technique, however, does not exist without limitations.

Considerable maneuvering through abdominal viscera is required, often necessitating the assistance of an access surgeon, and the required incision leaves a larger wound than minimally invasive (MIS) techniques such as the MIS transforaminal (TLIF) and lateral (LLIF) approaches to lumbar fusion. The LLIF procedure, involving a transpsoas approach to the spine, delivers the unique value of direct access to the anterior spinal column without the need for abdominal navigation.

The LLIF, developed in 2006,1 is traditionally performed with the patient in the lateral position. Through the use of tubular retractors, the surgeon traverses the psoas muscle to reach the anterior disc space for discectomy and implant insertion. If further stabilization is sought, the patient must be moved to the

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prone position for pedicle screw fixation. As pedicle screw stabilization is commonly used to facilitate fusion and as repositioning necessitates extended operative time, surgeons have recently begun to consider single-position LLIF options. In lateral decubitus single-position LLIF procedures, pedicle screw fixation is achieved without the need for intraoperative reposiMichael C. Prabhu, BS tioning, though this technique may lend itself to unwanted pedicle screw malpositioning.2 On the flip side, the prone position has recently seen considerable exploration as a single-position Madhav R. Patel, BS LLIF option (Figure 1). Preliminary studies3 have reported safety and feasibility of the prone transpsoas approach, with Walker et al4 finding greater improvement in segmental lordosis for prone single-position LLIF patients Kevin C. Jacob, BS when compared with traditional dual-position patients. Guiroy et al’s5 recent systematic review discovered similar perioperative outcomes between prone single-position and dual-position LLIF procedures with shorter Kern Singh, MD

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operative times and hospital stays for prone single-position patients. Soliman et al6 compared the prone transpsoas approach to the transforaminal lumbar interbody fusion (TLIF) and found the prone LLIF approach to be superior in postoperative disability outcomes as well as superior improvement in lumbar lordosis and pelvic tilt. Although initial results appear promising, further investigation is needed to confirm technical efficacy.

Martirosyan et al’s7 case report highlights the ability of prone positioning to optimize correction of lumbar lordosis, indicating that segmental lordosis was achieved through patient positioning and stabilized w ith instrumentation. This report suggests that the prone position holds an inherent anatomical advantage to the lateral decubitus position, such that the sought-after lordosis can be ensured during positioning before vertebrae are fixed. Amaral et al8 recently evaluated the effect of patient positioning on lordosis, finding the prone position to be significantly associated with increased lumbar and segmental lordosis relative to the lateral decubitus position. Additionally, the prone LLIF differs from the lateral decubitus single-position LLIF in that it does not compromise the surgeon’s traditional posterior approach to pedicle screw fixation, which may in turn reduce postoperative pedicle screw breach rates.

During intervertebral implant insertion, however, compromise may be given with the surgeon performing a lateral technique in a nontraditional manner. When traversing the psoas muscle in the lateral approach to the lumbar spine, the surgeon risks damage

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Figure 1. Patient positioning for lateral surgery. Top: traditional lateral decubitus, taped to a breaking surgical table; Middle: prone – early experience, taped to Jackson frame-style surgical table and using contralateral supports to counter lateral instrument forces; Bottom: PTP as evolved, positioned using customized system to more robustly stabilize patient and control the torso while eliminating the use of tape. Image and caption acquired from: Smith TG, Joseph Jr. SA, Ditty B, et al. Initial multi-centre clinical experience with prone transpsoas lateral interbody fusion: feasibility, perioperative outcomes, and lessons learned. Spine J. 2021;6:100056.11 Licensed under Creative Commons Attribution (CC BY 4.0). https:// creativecommons.org/licenses/by/4.0/

to the genitofemoral and other significant nerves of the lumbar plexus. 9 Damage to such nerves can result in unwanted postoperative complications affecting sensation in the upper thigh and groin areas. As such, surgeons performing prone single-position LLIF must take careful consideration while dissecting the psoas muscle, a task that can prove more challenging than when in the traditional lateral decubitus position (Figure 2).

A preliminary analysis of 9 patients by North et al10 reported postoperative complications of bilateral hip flexor weakness and left knee extension weakness in 1 patient, as well as

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Figure 2. Surgeons have the choice to sit or stand during PTP. Ample space is available for staff maneuverability in a simplified setup. Image and caption from: Stone LE, Wali AR, Santiago-Dieppa DR, Taylor WR. Prone-transpsoas as single-position, circumferential access to the lumbar spine: a brief survey of index cases. Spine J. 2021;6:100053.12 Licensed under Creative Commons Attribution (CC BY 4.0). https://creativecommons.org/licenses/by/4.0/

right lateral thigh numbness and dysesthesia in another, after prone single-position LLIF using navigation and robotic assistance, further highlighting the need to remain aware of the risks of employing a lateral approach to the spine with the patient in the prone position.

Multiple preliminary analyses have indicated the prone single-position LLIF to be

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a potentially safe and feasible alternative to the traditional technique of repositioning the patient between implant insertion and pedicle screw fixation. Armed with the ability to significantly reduce time in the operating room and under anesthesia, as well as the ability to potentially provide improved lumbar lordotic correction, this may prove to be a valuable operative innovation. Despite these advantages, however, the inherent compromise given to the lateral approach implant insertion stage of the procedure must be accounted for, and surgeons looking to adopt such a technique must be particularly aware of the potential neurologic complications that may arise when passing through the psoas muscle.

Further investigation is required to determine the ultimate feasibility of performing this procedure in comparison to the traditional dual-position LLIF technique. n

References 1. Ozgur BM, Aryan HE, Pimenta L, Taylor WR. Extreme lateral interbody fusion (XLIF): a novel surgical technique for anterior lumbar interbody fusion. Spine J. 2006;6(4):435-443.

2. Mills ES, Treloar J, Idowu O, Shelby T, Alluri RK, Hah RJ. Single position lumbar fusion: a systematic review and meta-analysis. Spine J. 2022;22(3):429-443.

3. Lamartina C, Berjano P. Prone single-position extreme lateral interbody fusion (Pro-XLIF): preliminary results.

Eur Spine J. 2020;29(Suppl 1):6-13.

4. Walker CT, Farber SH, Gandhi S, Godzik J, Turner JD, Uribe JS. Single-position prone lateral interbody fusion improves segmental lordosis in lumbar spondylolisthesis.

World Neurosurg. 2021;151:e786-e792.

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5. 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.

6. Soliman MAR, Aguirre AO, Ruggiero N, et al. Comparison of prone transpsoas lateral lumbar interbody fusion and transforaminal lumbar interbody fusion for degenerative lumbar spine disease: a retrospective radiographic propensity score-matched analysis. Clin Neurol Neurosurg. 2022;213:107105.

7. Martirosyan NL, Uribe JS, Randolph BM, Buchanan RI. Prone lateral lumbar interbody fusion: case report and technical note. World Neurosurg. 2020;144:170-177.

8. 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.

9. Epstein NE. Review of risks and complications of extreme lateral interbody fusion (XLIF). Surg Neurol Int. 2019;10:237.

10. 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.

11. Smith TG, Joseph SA Jr, Ditty B, et al.

Initial multi-centre clinical experience with prone transpsoas lateral interbody fusion: feasibility, perioperative outcomes, and lessons learned. Spine J. 2021;6:100056.

12. Stone LE, Wali AR, Santiago-Dieppa DR, Taylor WR. Prone-transpsoas as single-position, circumferential access to the lumbar spine: a brief survey of index cases. Spine J. 2021;6:100053.

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

Facet Cyst: To Fuse or Not To Fuse?

The facet joints are located between the vertebrae and are lubricated by synovial fluid contained in a membrane called the synovial sac. Synovial fluid allows for smooth movements to occur within this cartilaginous joint. Facet joints are the only synovial joints in the spine and can be involved in many pathological processes including arthropathy, infection, inflammation, trauma, and tuRobert Kamil, BS mors.1 With degeneration of the facet joint, synovial f luid production increases to compensate for decreased motion, and excess f luid accumulation within the s y nov ia l sac ca n i nduce t he formation of a facet cyst.

Junho Song, BS Facet cysts are usually common i n a n older popu lat ion (average age of 66 years) with frequencies ranging from 0.6% to 7.3%. 2 Sy nov ial cysts most commonly occur at the L4–L5 facets, the site of maximum mobility, and are a common cause Pratyush Shahi, MBBS, MS(Ortho) of symptomatic nerve root compression. 2,3 Facet cysts are often associated with spondylosis and degenerative spondylolisthesis, and they can lead to radiculopathy, neurogenic claudication, and cauda equina syndrome. 3,4 Advanced imaging studies have Sravisht Iyer, MD

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increased the diagnosis of cysts; however, optimal treatment of facet cysts remains controversial.

Initial treatment involves nonsurgical therapies, which include physical therapy, nonsteroida l a nt i-inf la m mator y dr ugs (NSAIDs), and/or draining the cyst with a facet injection. 3,5 Failure of conservative approaches and ongoing patient pain warrant surgical management that includes decompression a nd possibly f usion. 4 ,6 Spinal instability has been the most common cause of facet cyst recurrence and the return of patient symptoms.7 Ideal treatment has been prioritized to prevent the recurrence of symptoms. In this review, we compare the treatment of a facet cyst with decompression alone versus decompression with fusion.

Decompression Without Fusion Although the primary proposed reason for performing fusion in the setting of facet cysts is the association of facet cysts with spinal instability, which leads to recurrence of sy mptoms, there is little accordance in current literature, with some studies demonstrating no significant difference in clinical outcomes. 8-10 Van Dijke et al 11 demonst rated t hat a f ter adjust i ng for potential confounders, there was no difference in recurrence of radiculopathy or back pain between patients undergoing decompression without fusion and those

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Khan et al10 showed that patients who underwent decompression with fusion had better outcomes than decompression alone, with a higher proportion of patients (80% vs 70%) achieving long-term resolution of symptoms. unstable spondylolisthesis). Nevertheless, careful preoperative risk assessment is necessar y to evaluate the risk of spinal instability and cyst recurrence.

undergoing concomitant fusion. In this analysis, the authors accounted for the level of the cyst, bilateral cysts, spondylolisthesis, prior spine surgery, and number of decompressed levels.11 In an assessment of long-term outcomes with nearly a 10-year average follow-up, Weiner et al12 reported that there were no differences in symptom recurrence, need for additional surgery, or patient satisfaction between patients undergoing fusion versus decompression alone. These findings suggest that with appropriate patient selection, decompression alone without fusion is a reasonable option for the surgical treatment of facet cysts in absence of other concurrent pathology (eg,

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Decompression With Fusion Proponents of fusion for the management of facet cysts argue that because underlying segmental instability is a potential cause, decompression alone may augment the recurrence of the facet cyst. Fusion is seen as a more reliable modality of surgical treatment as it nullifies the chances of recurrence by preventing motion and further degeneration at the affected level. A large cyst requiring complete facetectomy for excision may also necessitate fusion.

K ha n et a l 10 showed t hat pat ients who under went decompression w it h f usion had better outcomes than decompression alone, with a higher proportion of patients (80% vs 70%) achieving long-term resolution of symptoms. Xu et al 9 demonstrated a higher risk of cyst recurrence and back pain with decompression alone compared to decompression with fusion. Bydon et al, 8 in their systematic review, showed a cyst recurrence rate of 1.8% after decom-

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DEGENERATION

pression alone compared to no reported c a se of rec u r rence a f ter f u sion. T he y concluded that although decompression leads to s y mptomat ic i mprovement i n most patients, the value of fusion in the treatment of facet cyst should be further investigated.

Conclusion Current literature has long debated the necessity of fusing a facet cyst. Although f usion prevents seg mental mot ion and negates the chances of cyst recurrence, it is more invasive than decompression alone and is associated w it h higher risk and complication rates and slower recover y.

It also requires a higher level of surgical fitness, which can preclude some patients from undergoing it. Postoperative complications include pseudarthrosis, adjacent segment disease, and implant-related is-

sues. Current evidence for the treatment of facet cysts shows that decompression alone is effective, with most patients improving significantly over the long term.

Reported cyst recurrence rates after decompression have mostly been <5%. The advent of minimally invasive techniques for decompression further supports this argument as there is minimal concern of postlaminectomy instability causing cyst recurrence after a unilateral laminotomy for bilateral decompression. At the same time, fusion is indicated in cases with evidence of instability, a large cyst requiring complete facetectomy, and bilateral cysts causing symptoms. The treatment protocol for facet cysts should be decided on a caseby-case basis with an inclination toward the less invasive option of decompression alone and supplementing it with a fusion when appropriate indications are present. n

References 1. Almeer G, Azzopardi C, Kho J, et al. Anatomy and pathology of facet joint. J Orthop. 2020;22:109-17.

2. Al Habsi S, Al Ghafri K, Elsaid M, et al. Lumbar facet cyst as a rare cause of L5 radiculopathy: a case report.

Case Rep Orthop Res. 2020;3:34-41.

3. Boody BS, Savage JW. evaluation and treatment of lumbar facet cysts. J Am Acad Orthop Surg. 2016;24:829-42.

4. Denis DR, Hirt D, Shah S, et al. Minimally invasive surgery for lumbar synovial cysts with coexisting degenerative spondylolisthesis. Int J Spine Surg. 2016;10:37.

5. Splavski B, Rotim A, Brumini I, et al.

Lumbar spine synovial cyst: a case series report and review of surgical strategies.

Acta Clin Croat. 2019;58:491-496.

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6. Wun K, Hashmi SZ, Maslak J, et al.

The variability of lumbar facet joint synovial cyst recurrence requiring revision surgery after decompression-only and decompression/fusion.

Clin Spine Surg. 2019;32:E457-E461.

7. Lutz GE, Nicoletti MR, Cyril GE, et al.

Percutaneous rupture of zygapophyseal joint synovial cysts: a prospective assessment of nonsurgical management. PM R. 2018;10:245-253.

8. Bydon A, Xu R, Parker SL, et al. Recurrent back and leg pain and cyst reformation after surgical resection of spinal synovial cysts: systematic review of reported postoperative outcomes. Spine J. 2010;10:820-826.

9. Xu R, McGirt MJ, Parker SL, et al. Factors associated with recurrent back pain and cyst recurrence after surgical resection of one hundred ninety-five spinal synovial cysts: analysis of one hundred sixty-seven consecutive cases. Spine (Phila Pa 1976). 2010;35:1044-1053.

10. Khan AM, Synnot K, Cammisa FP, et al. Lumbar synovial cysts of the spine: an evaluation of surgical outcome. J Spinal Disord Tech. 2005;18:127-131.

11. van Dijke M, Janssen SJ, Cha TD, et al. Comparison of decompression with and without fusion for patients with synovial facet cysts. Clin Spine Surg. 2017;30:E1399-E1404.

12. Weiner BK, Torretti J, Stauff M. Microdecompression for lumbar synovial cysts: an independent assessment of long term outcomes. J Orthop Surg Res. 2007;2:5.

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

MEDICAL DEVICES

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History, Efficacy, and Safety of the Barricaid Annular Closure Device A Brief Commentary An ongoing quest to develop and refine the gold standard of surgical treatment for lumbar disc herniation has yielded multiple techniques since the description of the original intervention in the 1930s.1,2 Current trends in practice favor the use of a minimally invasive surgical (MIS) approach, the origins of which can be found in the tubular discectomy system introduced by Smith and Foley in 1997. 3 Although several studies comparing minimally invasive approaches to alternatives have not reached a consensus, some suggest this evolution toward MIS techniques has yielded superior clinical and surgical outcomes while simultaneously reducing complication rates; despite these advances, the problem of recurrent disc herniation looms.4-7 According to the literature, 4.7% to 6.7% of patients can expect to experience lumbar disc reherniation following MIS discectomy. 8,9 The underlying mechanism of lumbar disc herniation lends itself to recurrence. Once penetrated by the extrusion of the nucleus pulposus or iatrogenically during the surgical intervention itself, the anulus fibrosus often remains compromised. This can partially be attributed to the avascular nature and poor cellularity of the annulus.10 Lack of an intact annulus fibrosus potentially portends the reherniation of nucleus pulposus rem-

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nants and the loss of natural disc function postoperatively, as no “barrier” remains to retain nuclear material and maintain hydrostatic pressure in the intervertebral disc space.

Furthermore, prior studies have elucidated the relationship between increasing annular defect sizes and a heightened risk for Sidhant Dalal, BS disc reherniation.11,12 In recent years, attention has shifted toward exploring supplemental interventions for the en ha ncement of d iscectomy outcomes in the context of reherniation. Investigators have Daniel Shinn, BS adopted a wide variety of strategies, including suture application systems, biologic compounds, polyurethane scaffolds, and implantable mesh barriers.13-15 Each of these concepts represent a formulation of 2 basic doctrines: (1) the provision of mechanical Omri Maayan, BS support and (2) the enhancement of intrinsic disc-healing capabilities. However, evaluation of existing literature for clinical relevanc y revea ls t hat many studies regarding these proposed interventions are preliminary in Sheeraz Qureshi, MD, MBA

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nature and limited to in vitro environments and small populations.15 Avoiding the aforementioned limitations associated with alternatives, the Barricaid Annular Closure Device (ACD) has risen to prominence in the discourse on recurrent lumbar herniation. Developed by Barricaid Intrinsic Therapeutics, the Barricaid ACD received FDA approval in 2019.16 Intended to be a permanently implantable 2-part device, it consists of a woven radio-opaque polymer affixed to a titanium bone anchor.

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The polymer functions to provide mechanical occlusion to the annular defect, and the bone anchor maintains device positioning following insertion into either a cranial or caudal vertebral body.12 Intraoperatively, a surgeon would measure defect size against polymer dimensions to determine candidacy. If the defect does not exceed the polymer-constrained height/width threshold, the surgeon would then obtain radiographic confirmation of optimal device positioning and drive the anchor into the vertebral body under fluoroscopic guidance, thus completing the procedure.

In vivo studies examining both the clinical and surgical outcomes of Barricaid ACD with ample cohort populations and multi-year duration of follow-up have previously been performed. Of these, two notable randomized controlled trials discovered that Barricaid ACD in combination with discectomy was more effective in the prevention of disc reherniation when compared to discectomy alone.17,18 One RCT found the rate of reherniation to be 3.33% (ACD) vs 20.0% (non-ACD) at 2-year follow-up, and the other reported a rate of 18.8% (ACD) vs 31.6% (Non-ACD) at 5-year follow-up, with both studies calculating a statistically significant difference in reherniation between cohorts.17,18 The observed postoperative reherniation rate of the discectomy only cohort in the 5-year trial exceeds that reported previously in this article, which could be attributed to the lengthy follow-up of the study and the selection of patients with large annular defects.

Additional comparative studies on Barricaid with lower levels of evidence have arrived at similar conclusions.19

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MEDICAL DEVICES

Commonly observed following discectomy, disc height loss has been associated with both worse clinical outcomes and further surgical intervention. 20 Multiple processes contribute to this phenomenon, the most prominent of which are the removal of disc material and loss of hydrostatic pressure inside the nucleus pulposus.21 In the same vein, the benefits of Barricaid in relation to disc height are twofold. First, although disc-sparing discectomy enhances t he preservation of native spinal kinematics over subtotal discectomy, an increase in retained disc-material volume in the presence of an unsealed annular defect poses a greater risk of reherniation.11,22 Occlusion of an annular defect with mesh in combination with conservative discectomy would provide the same kinematic benefits while avoiding concerns of reherniation. Secondly, through the same occlusion mechanism, Barricaid can assist in maintaining hydrostatic pressure and therefore attenuate further loss of disc height.21,23 However, findings in the literature regarding any differential disc height loss in ACD vs non-ACD patients are contradictory, necessitating further investigation. Interestingly, Modic endplate changes and endplate penetration by device mesh have been observed following implantation, though endplate findings were not correlated with a corresponding worsening of clinical outcomes. 24 In terms of safety, studies report that patients receiving Barricaid ACD experience non-device related complications at a similar rate to their discectomy-only counterparts.17-19,24,25 With regard to device-related

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complications, the most frequently reported are device migration and mesh detachment/migration. 24 Device deficiencies can necessitate reoperation; yet only a portion of patients experiencing such deficiencies opted for corrective intervention.24 The ultimate destination of device/mesh migration may be a differentiating factor, especially in terms of potential cord impingement and ensuing symptomatology. Regardless, reported incidents of mesh detachment and device migration suggest the potential for improving the bone-anchor fixation mechanism as well as the durability of the mesh-anchor connection. Comparative studies have found improvement in clinical outcome scores across both ACD and non-ACD cohorts; a greater improvement in patient-reported outcome measures such as the visual analog scale for back pain and leg pain and the Oswestry Disability Index (ODI) in those receiving ACD with discectomy vs discectomy only was statically significant in some studies19 but not in others.17,18 Ultimately, Barricaid has demonstrated both clinical efficacy and safety with regard to the prevention of reherniation, thus achieving its primary goal. Secondary benefits such as the maintenance of intradiscal hydrostatic pressure, an attenuation of disc-height loss, and greater improvements in patient-reported outcome measures over discectomy alone are not immediately apparent in the literature. Continued investigation would shed light not only on the validity of these claimed secondary benefits but also highlight areas of concern for continued device improvement and development. n

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References 1. Dandy WE. Loose cartilage from intervertebral disk simulating tumor of the spinal cord. By Walter E. Dandy, 1929.

Clin Orthop Relat Res. 1989;(238):4-8.

2. Mixter WJ. Pitfalls in the surgery of the ruptured intervertebral disk. J Fla Med Assoc. 1952;39(3):159-167.

3. Foley KT, Smith MM, Rampersaud YR. Microendoscopic approach to far-lateral lumbar disc herniation.

Neurosurg Focus. 1999;7(5):e5.

4. Kanno H, Aizawa T, Hahimoto K, Itoi E. Minimally invasive discectomy for lumbar disc herniation: current concepts, surgical techniques, and outcomes.

Int Orthop. 2019;43(4):917-922.

5. Wang J, Zhou Y, Zhang ZF, Li CQ, Zheng WJ, Liu J. Minimally invasive or open transforaminal lumbar interbody fusion as revision surgery for patients previously treated by open discectomy and decompression of the lumbar spine.

Eur Spine J. 2011;20(4):623-628.

6. Evaniew N, Bogle A, Soroceanu A, et al. Minimally invasive tubular lumbar discectomy versus conventional open lumbar discectomy: an observational study from the Canadian Spine Outcomes and Research Network [published online ahead of print July 9, 2021]. Global Spine J. doi:10.1177/21925682211029863.

7. Jarebi M, Awaf A, Lefranc M, Peltier J. A matched comparison of outcomes between percutaneous endoscopic lumbar discectomy and open lumbar microdiscectomy for the treatment of lumbar disc herniation: a 2-year retrospective cohort study. Spine J. 2021;21(1):114-121.

8. Kosztowski TA, Choi D, Fridley J, et al.

Lumbar disc reherniation after transforaminal lumbar endoscopic discectomy. Ann Transl Med. 2018;6(6):106.

9. Li X, Han Y, Di Z, et al. Percutaneous endoscopic lumbar discectomy for lumbar disc herniation. J Clin Neurosci. 2016;33:19-27.

10. Sloan SR, Lintz M, Hussain I, Hartl R, Bonassar LJ. Biologic annulus fibrosus repair: a review of preclinical in vivo investigations. Tissue Eng Part B Rev. 2018;24(3):179-190.

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11. Bouma GJ, Barth M, Ledic D, Vilendecic.

The high-risk discectomy patient: prevention of reherniation in patients with large anular defects using an anular closure device. Eur Spine J. 2013;22(5):1030-1036.

12. Kienzler JC, Fandino J, Van de Kelft E, et al. Risk factors for early reherniation after lumbar discectomy with or without annular closure: results of a multicenter randomized controlled study. Acta Neurochir (Wien). 2021;163(1):259-268.

13. Bateman AH, Balkovec C, Akens MK, et al. Closure of the annulus fibrosus of the intervertebral disc using a novel suture application device—in vivo porcine and ex vivo biomechanical evaluation. Spine J. 2016;16(7):889-895.

14. Li J, Yuan X, Li F, et al. A novel full endoscopic annular repair technique combined with autologous conditioned plasma intradiscal injection: a new safe serial therapeutic model for the treatment of lumbar disc herniation.

Ann Palliat Med. 2021;10(1):292-301.

15. Agnol LD, Gonzalez Dias FT, Nicoletti NF, Falavigna A, Bianchi O. Polyurethane as a strategy for annulus fibrosus repair and regeneration: a systematic review. Regen Med. 2018;13(5):611-626.

16. Strenge KB, DiPaola CP, Miller LE, Hill CP, Whitmore RG. Multicenter study of lumbar discectomy with Barricaid annular closure device for prevention of lumbar disc reherniation in US patients: a historically controlled post-market study protocol.

Medicine (Baltimore). 2019;98(35):e16953.

17. Cho PG, Shin DA, Park SH, Ji GY. Efficacy of a novel annular closure device after lumbar discectomy in Korean patients: a 24-month follow-up of a randomized controlled trial. J Korean Neurosurg Soc. 2019;62(6):691-699.

18. Thomé C, Kuršumovic A, Klassen PD, et al. Effectiveness of an annular closure device to prevent recurrent lumbar disc herniation: a secondary analysis with 5 years of follow-up. JAMA Netw Open. 2021;4(12):e2136809.

19. Parker SL, Grahovac G, Vukas D, et al.

Effect of an annular closure device (Barricaid) on same-level recurrent disk herniation and disk height loss after primary lumbar discectomy: two-year results of a multicenter prospective cohort study.

Clin Spine Surg. 2016;29(10):454-460.

20. McGirt MJ, Eustacchio S, Varga P, et al. A prospective cohort study of close interval computed tomography and magnetic resonance imaging after primary lumbar discectomy: factors associated with recurrent disc herniation and disc height loss. Spine (Phila Pa 1976). 2009;34(19):2044-2051.

21. Bostelmann R, Steiger HJ, Cornelius JF. Effect of annular defects on intradiscal pressures in the lumbar spine: an in vitro biomechanical study of diskectomy and annular repair. J Neurol Surg A Cent Eur Neurosurg. 2017;78(1):46-52.

22. Carragee EJ, Spinnickie AO, Alamin TF, Paragioudakis S. A prospective controlled study of limited versus subtotal posterior discectomy: shortterm outcomes in patients with herniated lumbar intervertebral discs and large posterior anular defect. Spine (Phila Pa 1976). 2006;31(6):653-657.

23. Wang Y, Bai B, Hu Y, et al. Hydrostatic pressure modulates intervertebral disc cell survival and extracellular matrix homeostasis via regulating Hippo-YAP/TAZ pathway.

Stem Cells Int. 2021;2021:5626487.

24. Kuršumović A, Kienzler JC, Bouma GJ, et al. Morphology and clinical relevance of vertebral endplate changes following limited lumbar discectomy with or without bone-anchored annular closure. Spine (Phila Pa 1976). 2018;43(20):1386-1394.

25. Martens F, Lesage G, Muir JM, Stieber JR. Implantation of a bone-anchored annular closure device in conjunction with tubular minimally invasive discectomy for lumbar disc herniation: a retrospective study. BMC Musculoskelet Disord. 2018;19(1):269.

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From UCI Health in Orange County, California.

PAIN MANAGEMENT

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Multimodal Pain Management After Spine Surgery Surgical dissection results in the release of substances such as bradykinin, histamine, lactic acid, prostaglandins, serotonin, glutamate, and substance P.1 The release of these substances results in an inflammatory response that may induce a sensation of pain for the patient. Nociceptive and neuropathic pain from iatrogenic physical and nerve damage, respectively, may also contribute to pain.2 In the setting of spinal surgery, perioperative pain can be severe in nature, particularly for invasive surgeries that cause substantial interruptions to a multitude of anatomical structures (ie, subcutaneous tissue, vertebrae, ligaments).2 Effective postoperative pain management after spine surgery is therefore important and may allow for earlier recovery, a more favorable complication profile, and improved patient satisfaction.3 Opioids have been widely utilized for many years to alleviate pain after spinal surgery; however, this method of pain control may result in several negative side effects, such as constipation, nausea and vomiting, delirium, and respiratory failure, and it comes with a risk of dependency and tolerance.4 Thus, it has become important to innovate novel pain control methods to limit the amount of narcotic use following surgery. One such method, termed multimodal pain management, involves the use of nonpharmacologic methods, nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen, ketamine,

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gabapentin, serotonin inhibitors, and regional techniques, along with opioids as needed.3,5,6 By including a combination of various nonnarcotic modalities for pain management, spine surgeons may be able to effectively reduce the Yu-Po Lee, MD amount of narcotics required in the acute postoperative period.6 As the importance of multimodal analgesia continues to gain recognition, this article introduces several nonnarcotic options that have been reported in the literature.

Nonnarcotic Pain Management Options One nonpharmacological pain control method is the application of cryotherapy, or the use of a cooling system, to decrease postoperative pain. For example, Yoo et al described the effective use of ice packs on postoperative day 0.6 A separate study demonstrated that the use of cryo-compression therapy provided positive results following elective spine surgery when compared with the use of painkillers alone.7 Patients can be provided cooling therapy at the surgery center and be advised to continue with around-the-clock application of ice after discharge to assist in pain alleviation.

Medications such as acetaminophen, NSAIDs, and gabapentinoids are also effective nonnarcotic options.6 Acetaminophen has been shown to reduce postoperative narcotic consumption and possibly pain related to the

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PAIN MANAGEMENT

surgical incision.5 Preoperative administration of 1 to 2 grams of acetaminophen, as well as administration of a multimodal combination including acetaminophen, have demonstrated lower postoperative opioid utilization following spine surgery.6 Acetaminophen may also be provided intraoperatively or postoperatively in combination with hydromorphone.6 By blocking COX enzymes, NSAIDs help alleviate inflammation-induced pain from prostaglandins. A combined regimen of NSAIDs and opioids has repeatedly been shown to reduce pain and the amount of opioid consumption after spine surgery.6 Of note, bleeding risk is a concern with perioperative NSAID exposure given the anti-platelet effects of cyclooxygenase-1 (COX-1) inhibitors. Nonetheless, bleeding times and incidence of postoperative bleeding events do not appear significantly influenced

by NSAIDs at usual doses, and this risk may be further mitigated by using COX-2 selective agents.8 It is important to note, however, that while some literature do suggest an association of NSAIDs with pseudarthrosis, especially at high doses,6 short-term NSAID use at normal doses may not affect spinal fusion rates.3 For instance, Kurd et al found that celecoxib, a selective COX-2 inhibitor, may not be associated with the aforementioned concerns of NSAID use in the setting of spine surgery.3 Oral gabapentin is often included as a component of multimodal pain regimens. Gabapentin is an anticonvulsant originally developed to treat epileptic seizures resistant to traditional therapies. While the mechanism is not fully understood, gabapentin is believed to alter neurotransmission by interrupting voltage-gated calcium channels in the dorsal horn of the

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spinal cord. This leads to decreased effects due to hyperexcitability in those regions caused by tissue damage.9 Studies have shown that gabapentin is effective in decreasing the need for postoperative opioids in surgical patients.9 Gabapentin can be titrated in doses of 1200 to 3600 milligrams per day given in three doses.

But attention to the side effects associated with this medication should be considered, especially within an elderly population. For instance, the use of gabapentin to treat or prevent pain may be associated with dizziness, tiredness, and altered mentation.10 The use of local anesthetics may additionally be helpful in postoperative pain control after spine surgery. Administration of lidocaine and epinephrine prior to surgery, along with ropivacaine use during wound closure has demonstrated the ability to reduce pain and opioid utilization following surgery.6 The main limitation of local anesthetics, however, is their duration of action, which diminishes their ability to provide opioid-sparing analgesia for multiple postoperative days. One strategy for extending the clinical duration of regional anesthesia is the addition of pharmacologic adjuvants such as dexamethasone, clonidine or dexmedetomidine, and/or epinephrine.11 While additives to local anesthetics may extend duration of peripheral nerve blockade by as much as 6 to 10 hours and are supported by clinical practice guidelines, total duration of action for single-shot injections will still likely be limited to less than 24 hours.11 Ketamine is another drug that can be used as part of multimodal pain management. It is a N-methyl-D-aspartate (NMDA) receptor antagonist and dissociative agent with high potency, yet it lacks the respiratory depressant

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PAIN MANAGEMENT

effects that opioids possess.12 Intraoperative intravenous (IV) ketamine infusions have been successfully used in multimodal approaches to manage pain for spine surgery.5,6 Murphy et al found that ketamine combined with methadone offered lower pain scores and lower acute postoperative hydromorphone utilization at postoperative days 1 and 2 and overall over 3 days compared to methadone alone.13 Examination of spinal fusion literature has shown ketamine to achieve the aforementioned positive results in chronic opioid users as well.14 While side effects of ketamine are important to consider, a recent meta-analysis found that opioid consumption and pain scores were effectively lowered at multiple timepoints through the 24-hour postoperative period by perioperative ketamine use, with no significant increase in risk of nausea/vomiting, respiratory failure,

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heart complications, dysphoria, hallucinations, or unwanted dreams.15

Conclusion A preoperative patient assessment is an opportunity for healthcare providers to identify baseline pain levels, current pain medication intake, successful past pain medication strategies, and past medical and surgical histories.

By gathering this information, we are better able to educate the patient on the most suitable options for pain management preoperatively, intraoperatively, and/or postoperatively. This manuscript provides a supporting case for the use of a multimodal approach to pain management, which appears to effectively minimize opioid utilization and improve several measures of patient care (ie, length of stay, recovery time, complication rates) and satisfaction. n

References 1. Elmallah RK, Chughtai M, Khlopas A, et al. Pain control in total knee arthroplasty. J Knee Surg. 2018;31(6):504-513.

2. Bajwa SJS, Haldar R. Pain management following spinal surgeries: an appraisal of the available options. J Craniovertebr Junction Spine. 2015;6(3):105-110.

3. Kurd MF, Kreitz T, Schroeder G, Vaccaro AR. The role of multimodal analgesia in spine surgery. J Am Acad Orthop Surg. 2017;25(4):260-268.

4. Benyamin R, Trescot AM, Datta S, et al.

Opioid complications and side effects. Pain Physician. 2008;11(2 Suppl):S105-S120.

5. Maheshwari K, Avitsian R, Sessler DI, et al. Multimodal analgesic regimen for spine surgery: a randomized placebo-controlled trial. Anesthesiology. 2020;132(5):992-1002.

6. Yoo JS, Ahn J, Buvanendran A, Singh K. Multimodal analgesia in pain management after spine surgery. J Spine Surg. 2019;5(Suppl 2):S154-S159.

7. Nabıyev VN, Ayhan S, Adhıkarı P, Cetın

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E, Palaoglu S, Acaroglu RE. Cryo-compression therapy after elective spinal surgery for pain management: a cross-sectional study with historical control. Neurospine. 2018;15(4):348-352.

8. Martinez L, Ekman E, Nakhla N. Perioperative opioid-sparing strategies: utility of conventional NSAIDs in adults.

Clin Ther. 2019;41(12):2612-2628.

9. Hah J, Mackey SC, Schmidt P, et al. Effect of perioperative gabapentin on postoperative pain resolution and opioid cessation in a mixed surgical cohort: a randomized clinical trial. JAMA Surg. 2018;153(4):303-311.

10. Fleet JL, Dixon SN, Kuwornu PJ, et al.

Gabapentin dose and the 30-day risk of altered mental status in older adults: a retrospective population-based study.

PLoS One. 2018;13(3):e0193134.

11. Albrecht E, Chin KJ. Advances in regional anaesthesia and acute pain management: a narrative review. Anaesthesia. 2020;75 Suppl 1:e101-e110.

12. Edwards DA, Hedrick TL, Jayaram J, et al. American Society for Enhanced Recovery and Perioperative Quality Initiative Joint Consensus Statement on Perioperative Management of Patients on Preoperative Opioid Therapy.

Anesth Analg. 2019;129(2):553-566.

13. Murphy GS, Avram MJ, Greenberg SB, et al. Perioperative methadone and ketamine for postoperative pain control in spinal surgical patients: a randomized, double-blind, placebo-controlled trial.

Anesthesiology. 2021;134(5):697-708.

14. Nielsen RV, Fomsgaard JS, Siegel H, et al.

Intraoperative ketamine reduces immediate postoperative opioid consumption after spinal fusion surgery in chronic pain patients with opioid dependency: a randomized, blinded trial. Pain. 2017;158(3):463-470.

15. Pendi A, Field R, Farhan SD, Eichler M, Bederman SS. Perioperative ketamine for analgesia in spine surgery: a meta-analysis of randomized controlled trials. Spine. 2018;43(5):E299-E307.

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From the Mike O’Callaghan Military Medical Center at Nellis Air Force Base, Nevada (Dr Shenoy) and the Texas Back Institute in Plano, Texas (Drs Derman and Satin).

Hypermobility Following Cervical Disc Arthroplasty Cervical disc arthroplasty (CDA) is a well-accepted surgical treatment for many pat ients w it h cervical radiculopathy and/or myelopat hy who have fa i led appropriate nonoperative treatKartik Shenoy, MD ment. Long-term results from numerous US Food and Drug Administration investigational dev ice exemption trials have demonstrated that CDA patients have less adjacent level degeneration (ALD) and undergo fewer Peter B. Derman, MD, MBA reoperations than patients who undergo anterior cervical discectomy and fusion (ACDF).1-6 As one would expect, the number of CDAs being performed is increasing.7 ACDF relies on the elimination of segmental motion and successAlexander Satin, MD ful fusion of adjacent vertebrae.

ALD is a major concern after ACDF and is thought to develop, in part, from the increased stress placed on adjacent levels following the loss of segmental motion.8-12 The rationale for spinal arthroplasty is that maintenance of index-level range of motion will decrease adjacent level stresses and ultimately reduce the development of ALD compared to ACDF.13-16 Recently, Spivak et al17 investigated the relationship between

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radiographic ALD and index-level segmental range of motion (ROM) in CDA patients using the 7-year follow-up data from the ProDisc-C investigational device exemption trial. The rate of progressive ALD trended significantly with final ROM (P = 0.01). The authors concluded that the reduced radiographic ALD seen in CDA is related to the preservation of motion at the index level and resultant preservation of kinematics and forces across the adjacent disc space.

Despite the benefits of preserved motion seen with CDA, recent concerns regarding too much motion (ie, hypermobility) have arisen, especially with unconstrained implants.18 The classification of cervical arthroplasty devices is complex, with particular ambiguity regarding the terms unconstrained, constrained, and semi-constrained.19,20 In general, unconstrained devices have the capacity to translate independent of rotation. Since these prostheses lack an internal constraint, the constraint is supplied by the tension in the ligaments and annulus and by the facet joints. As a result, the prosthesis is capable of adopting different centers of rotation. 20 To further complicate the discussion, there remains little consensus regarding what amount of motion constitutes hypermobility. Nevertheless, we will review the available literature discussing hypermobility following CDA.

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Kerferd et al 21 reviewed 2 cases of focal hypermobility following CDA with an unconstrained implant. The implant features a mobile ultra-high molecular weight polyethylene core, which repositions in response to movement of the superior endplate. The authors surmised that the hypermobility in their cases was occurring due to excessive core translation. The first patient was noted to have 12° of motion and marked anterolisthesis on flexion at 3-month follow-up after a C5/6 ACDF and C6/7 CDA. The second patient had focal hypermobility on extension with 15.6° of motion at 6 weeks. Interestingly, both patients were asymptomatic and had sustained symptom relief at more than 1-year follow-up.

In another case report, Kim et al22 reported a case of hypermobility following unconstrained CDA implantation leading to severe neck pain 1 year postoperatively. However, the authors state that wide removal of the uncovertebral joint was necessary in this case in order to achieve adequate neural decompression. They posit that this likely contributed to instability and, therefore, the hypermobility was iatrogenic due to surgical factors. To that end, biomechanical studies have demonstrated that bilateral resection of the uncovertebral joints in conjunction with CDA can lead to significantly increased range of motion. 23 Patel et al18 performed a retrospective cohort study evaluating unconstrained CDA’s effect on segmental ROM. They included 148 CDA patients (58 single-level, 90 two-level) from a single institution in their analysis.

Hypermobility was classified as ≥11° in ROM from baseline to follow-up or >3 mm trans-

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Despite the benefits of preserved motion seen with CDA, recent concerns regarding too much motion (ie, hypermobility) have arisen, especially with unconstrained implants. lation. Age, gender, and body mass index were similar between normal and hypermobile groups. Hypermobile patients had a significantly higher Charlson Comorbidity Index. According to their definition, 40% of single-level patients developed hypermobility at follow-up. Follow-up ROM (12.2° ± 6.8°, P = 0.003) was significantly higher compared to the average baseline ROM (9.2° ± 4.9°). C5-C6 had significantly higher follow-up ROM (C5C6: 13.7° ± 6.9°, P = 0.003) than baseline ROM (C5-C6: 9.2° ± 4.9°). Multivariate regression analysis of implant factors, patient demographics, and disc level demonstrated no risk factors for hypermobility except a slightly shorter implant depth (13.6 ± 0.9 mm vs 14.3 ± 1.2 mm, P = 0.004; OR: 0.565, P = 0.005). The mechanism by which hypermobility occurs in patients has yet to be defined.

In conclusion, the concept of hypermobility and its clinical implications following CDA are poorly defined. While published reports predominantly include unconstrained, mobile core implants, direct comparison of implants has not taken place. Further research is needed to determine which patients and/or implants are susceptible to developing clinically meaningful hypermobility after CDA. n

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References 1. Gornet MF, Burkus JK, Shaffrey ME, Schranck FW, Copay AG. Cervical disc arthroplasty: 10-year outcomes of the Prestige LP cervical disc at a single level. J Neurosurg Spine. 2019;31(3):317-325.

2. Gornet MF, Lanman TH, Burkus JK, et al. Two-level cervical disc arthroplasty versus anterior cervical discectomy and fusion: 10-year outcomes of a prospective, randomized investigational device exemption clinical trial. J Neurosurg Spine. 2019;31(4):508-518.

3. Janssen ME, Zigler JE, Spivak JM, Delamarter RB, Darden BV 2nd, Kopjar B. ProDisc-C total disc replacement versus anterior cervical discectomy and fusion for single-level symptomatic cervical disc disease: seven-year follow-up of the prospective randomized US Food and Drug Administration Investigational Device Exemption Study. J Bone Joint Surg Am. 2015;97(21):1738-1747.

4. Vaccaro A, Beutler W, Peppelman W, et al. Long-term clinical experience with selectively constrained SECURE-C cervical artificial disc for 1-level cervical disc disease: results from seven-year follow-up of a prospective, randomized, controlled investigational device exemption clinical trial. Int J Spine Surg. 2018;12(3):377-387.

5. Radcliff K, Davis RJ, Hisey MS, et al. Long-term evaluation of cervical disc arthroplasty with the Mobi-C© cervical disc: a randomized, prospective, multicenter clinical trial with seven-year follow-up.

Int J Spine Surg. 2017;11(4):31.

6. Wang Q-L, Tu Z-M, Hu P, et al.

Long‐term results comparing cervical disc arthroplasty to anterior cervical discectomy and fusion: a systematic review and meta‐analysis of randomized controlled trials.

Orthop Surg. 2020;12(1):16-30.

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7. Niedzielak TR, Ameri BJ, Emerson B, et al. Trends in cervical disc arthroplasty and revisions in the Medicare database. J Spine Surg. 2018;4(3):522-528.

8. 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.

9. Elsawaf A, Mastronardi L, Roperto R, et al. Effect of cervical dynamics on adjacent segment degeneration after anterior cervical fusion with cages.

Neurosurg Rev. 2009;32(2):215-224.

10. Park D-H, Ramakrishnan P, Cho T-H, et al. Effect of lower two-level anterior cervical fusion on the superior adjacent level. J Neurosurg Spine. 2007;7(3):336-340.

11. Sugawara T, Itoh Y, Hirano Y, Higashiyama N, Mizoi K. Long term outcome and adjacent disc degeneration after anterior cervical discectomy and fusion with titanium cylindrical cages. Acta Neurochi (Wien). 2009;151(4):303-309.

12. Eck JC, Humphreys SC, Lim T-H, et al. Biomechanical study on the effect of cervical spine fusion on adjacent-level intradiscal pressure and segmental motion. Spine (Phila Pa 1976). 2002;27(22):2431-2434.

13. Luo J, Gong M, Huang S, Yu T, Zou X. Incidence of adjacent segment degeneration in cervical disc arthroplasty versus anterior cervical decompression and fusion meta-analysis of prospective studies. Arch Orthop Trauma Surg. 2015;135(2):155-160.

14. Chang U-K, Kim DH, Lee MC, Willenberg R, Kim S-H, Lim J. Changes in adjacent-level disc pressure and facet joint force after cervical arthroplasty compared with cervical discectomy and fusion. J Neurosurg Spine. 2007;7(1):33-39.

15. Laxer EB, Darden BV, Murrey DB, et al. Adjacent segment disc pressures following two-level cervical disc replacement versus simulated anterior cervical fusion. Stud Health Technol Inform. 2006;123:488-492.

16. Verma K, Gandhi SD, Maltenfort M, et al. Rate of adjacent segment disease in cervical disc arthroplasty versus single-level fusion: meta-analysis of prospective studies. Spine (Phila Pa 1976). 2013;38(26):2253-2257.

17. Spivak JM, Zigler JE, Philipp T, Janssen M, Darden B, Radcliff K. Segmental motion of cervical arthroplasty leads to decreased adjacent-level degeneration: analysis of the 7-year postoperative results of a multicenter randomized controlled trial.

Int J Spine Surg. 2022;16(1):186-193.

18. Patel H, Norris Z, O’Malley N, et al. 163. Unconstrained cervical disc replacements: is segmental hypermobility a concern? The Spine Journal. 2021;21:S82.

19. Patwardhan AG, Havey RM. Biomechanics of Cervical Disc Arthroplasty-A Review of Concepts and Current Technology. Int J Spine Surg. 2020;14:S14-S28.

20. Sears WR, McCombe PF, Sasso RC. Kinematics of cervical and lumbar total disc replacement. Sem Spine Surg. 2006;18(2):117-129.

21. Kerferd JW, Abi-Hanna D, Phan K, Rao P, Mobbs RJ. Focal hypermobility observed in cervical arthroplasty with Mobi-C. J Spine Surg. 2017;3(4):693-696.

22. Kim KJ, Gang MS, Bae J-S, Jang JS, Jang I-T. Cervical instability following artificial disc replacement.

Surg Neurol Int. 2019;10:183.

23. Snyder JT, Tzermiadianos MN, Ghanayem AJ, et al. Effect of uncovertebral joint excision on the motion response of the cervical spine after total disc replacement. Spine (Phila Pa 1976). 2007;32(26):2965-2969.

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