Vertebral Columns Winter 2025

When Peak Performers Stumble: Surgical Complications in Spine Surgery and Compassion for the Second Victim Neuraxial Anesthesia and Regional Nerve Blocks: What Is Being Utilized to Decrease Postoperative Spine Pain?

Role of Psychosocial Factors in Chronic Low Back Pain: A Contemporary Review What Is the Evidence for Bone Growth Stimulators?

Adjacent Segment Disease Following CDR and Cervical Fusion Evolution of Lumbar Disc Replacement in the United States Understanding and Managing Intraoperative Neuromonitoring Changes in Spinal Deformity Surgery Cost-Effectiveness Assessment in Spine Surgery

Vertebral

COLUMNS International Society for the Advancement of Spine Surgery

Vitamin D The Backbone of Health

WINTER 2025

PLUS:

Winter 2025

Editor in Chief Kern Singh, MD Editorial Board Brandon Hirsch, MD

EDITORIAL 3 Vitamin D: The Backbone of Health SURGEON FOCUS 7 When Peak Performers Stumble: Surgical Complications in Spine Surgery and Compassion for the Second Victim

10 CLINICAL OUTCOMES

Neuraxial Anesthesia and Regional Nerve Blocks: What Is Being Utilized to Decrease Postoperative Spine Pain?

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

MENTAL HEALTH 16 Role of Psychosocial Factors in Chronic Low Back Pain: A Contemporary Review

TECHNOLOGY 21 What Is the Evidence for Bone Growth Stimulators?

CERVICAL SPINE 23 Adjacent Segment Disease Following CDR and Cervical Fusion

LUMBAR SPINE 28 Evolution of Lumbar Disc Replacement in the United States

SPINE DEFORMITY 31 Understanding and Managing Intraoperative Neuromonitoring Changes in Spinal Deformity Surgery

ECONOMICS OF SPINE SURGERY 37 Cost-Effectiveness Assessment in Spine Surgery

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Vertebral Columns is published quarterly by the International Society for the Advancement of Spine Surgery. ©2025 ISASS. All rights reserved.

Opinions of authors and editors do not necessarily reflect positions taken by the Society.

This publication is available digitally at https://isass.org/category/news/ vertebral-columns/

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

EDITORIAL

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Vitamin D The Backbone of Health

Of all the vitamins people have access to, vitamin D is one of the more well known.

Whether people think about vitamin D in terms of sun exposure, bone strength, or foods, the majority of the population knows about this particular vitamin. However, people may be unaware of the importance of vitamin D and its critical link to musculoskeletal health.1 In the United States, around 41.6% of adults are deficient in vitamin D, and in the world, around 1 billion people have low vitamin D levels across all ethnicities and age groups.2 In terms of spine health, a study conducted by Kim et al highlighted that 74.3% of patients with a diagnosis of lumbar spinal stenosis were deficient in vitamin D.3 This particular study underscored the importance of vitamin D’s role in musculoskeletal health as the authors found greater pain was linked to low vitamin D levels and existing osteoporosis. 3 Vitamin D can be described as a critical nutrient for the establishment and maintenance of human bone health.4,5 In terms of maintenance, the vitamin is crucial in protecting against cancer, osteoarthritis, cardiovascular disease, and diabetes.6 Improving immune system function, muscle function, and balance can also be attributed to the role of vitamin D.6 Additionally, spine surgeons have found vitamin D to be essential for bone health and maintaining calcium balance in the body.6 By exploring

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the importance of vitamin D in the human body we can acquire a deeper understanding of how deficiency affects spine health and thus identif y possible interventions.

Sloane Ward, BS

Overview of Vitamin D Shriya Patel, BS As noted previously, vitamin D is a critical mineral for the human body. Vitamin D is involved in various aspects of helping the body, but some of its main functions are to assist with calcium absorption and bone mineralKern Singh, MD ization.6 Literature shows that calcium is absorbed from the small intestine when vitamin D is present.7 Absorption of calcium is critical to allow for adequate mineralization of the bone.7 Vitamin D heightens the efficacy of this absorption to help the overall function of the human body.7 On the other hand, bone mineralization is also highly important in regards to bone mineral density (BMD). Low bone mineral density can mean the presence of osteoporosis, which has the ability to lead to a greater risk of spine fractures.8 A healthy level of bone mineral density is good not just for spine health but overall bone health. Deficiency of vitamin D can even cause decreased immune function or autoimmune conditions.9 There are various ways to keep a healthy

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EDITORIAL

level of vitamin D in the body at all times, and these options are expanded upon later in this article.

Spine Health and the Role of Vitamin D Vitamin D has a strong correlation to maintaining the integrity of various aspects of the human body, including the spine. Patients Figure 1. Vitamin D gummy supplements. lacking in the vitamin can be predisposed to a heightened risk for worse clinical outcomes postoperatively.4 This may be due to the fact that when people lack vitamin D, their bones are weaker and they have lower bone density and lower calcium absorption. 6,7 Thus, it is critical to maintain one’s bone health, thereby preserving spine health in the process. Maintaining spinal health leads to an increase in positive postoperative surgical outcomes and greater spinal stability.6 To maintain one’s spine health, the risk of fractures, deformities, and degenerative spine conditions must be minimized, and vitamin D can assist with all of this.

Vitamin D Deficiency Vitamin D deficiency can be identified by various clinical risk factors such as deficient dietar y intake to meet the body’s nutritional needs combined with restricted sun exposure.10 Additionally, gastrointestinal, hepatic, and renal conditions can lead to

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vitamin D deficiencies.10 Low vitamin D levels can result in bone loss due to reduced absorption of calcium in the intestine.10 Therefore, clinicians should regularly test for vitamin D deficiency in patients presenting with musculoskeletal pain and generalized weakness.10 Particularly, those with low bone mineral density, a history of low-impact skeletal fractures, or an increased risk of falling should be evaluated for vitamin D deficiency, as treatment can help reduce the risk of skeletal fractures.10 A randomized controlled trial found supplementation of vitamin D reduced the number of falls by around 50% among elderly women.11 Assessing vitamin D levels is crucial to determine whether there are deficiencies.

Vitamin D obtained from our diets or sunlight exposure is rapidly converted to 25(OH)D, with a small amount becoming the active form, 1,25(OH)2D.10 Levels of 1,25(OH)2D are not measured to diagnose hypovitaminosis D because of its short half-life,12 and the body increases parathyroid hormone production in response to low vitamin D levels to help regulate calcium.10 Notably, this can keep calcium levels normal in blood tests and makes 25(OH)B a more reliable indicator of vitamin D status.10 Vitamin D deficiency is defined as 25(OH)D levels below 20 ng/mL and vitamin D insufficiency ranges from 2129 ng/mL of detected 25(OH)D.12 If patients are presenting with chronic back pain, it is important to consider testing for vitamin D deficiency. Maintaining an optimal level of 25(OH)D can support spinal health and potentially alleviate pain associated with underlying bone weakness.13

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EDITORIAL

Prevention and Management By addressing vitamin D deficiency through proper nutrition or supplementation, chronic pain, including low back pain, may be alleviated. Research has shown that an insufficient uptake of vitamin D and calcium in the diet is strongly linked to chronic low back pain, particularly in women.14 Omega-3 polyunsaturated fatty acids have been found to significantly reduce pain levels, specifically in patients with rheumatoid arthritis.14 Vitamin D can be obtained through dietary sources, sunlight, and supplements.15 Some of the few foods rich in vitamin D include oily or fatty fish, egg yolk, cod liver oil, and fortified foods such as milk and cereal.15,16 For adults, the recommended daily intake of vitamin D is 600-800 IU/day.15 To prevent falls and fractures in adults older than 65 years, the American Geriatric Society (AGS) and the National Osteoporosis Foundation (NOF) suggest higher intakes of 800-1000 IU per day.15,17 If daily intake is not met, supplementation is recommended. Vitamin D supplementation is in the form of cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2).18 A systematic review comparing the efficacy of each supplement concluded that cholecalciferol, or vitamin D3, had greater improvements in vitamin D status in individuals by raising serum 25(OH)D concentrations.18 Along with diet and supplementation, another source of vitamin D is ultraviolet (UV) sun radiation.

Srivastava et al recommended 5 to 30 minutes of sunlight exposure at least twice a week without sunscreen, which blocks the effective production of vitamin D without UVB ray absorption from the body.19 Sunscreen

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should be applied at appropriate SPF levels after the short recommended time frame in the sun.19 It is important to maintain our vitamin D levels through sufficient dietary intake, vitamin D supplementation, and daily walking.20 These practices contribute to stronger bones and greater spine health, reducing the risk of fractures associated with vitamin D deficiency.

Special Considerations for Spine Surgery Ko et al analyzed clinical outcomes following lumbar spine surgery in patients with vitamin D deficiencies and divided cohorts based on whether they were taking supplementation for vitamin D.21 The outcome measures included the Oswestry Disability Index, the 36-item Short Form Survey (SF-36) Mental Component Score (MCS), and the SF-36 Physical Component Score (PCS). 21 There were no significant differences found in preoperative scores; however, at the 1-year and 2-year postoperative follow-ups, patients who were not taking vitamin D supplementation reported significantly worse ODI, SF-36 MCS, and SF-36 PCS scores. 21 Ko et al suggested checking vitamin D levels preoperatively and prescribing vitamin D supplementation to help long-term postoperative outcomes such as quality of life.21 Conclusion Vitamin D plays a crucial role in maintaining spinal health by supporting bone density and reducing the risk of fractures. As mentioned previously, if patients are experiencing chronic back pain, it may be due to vitamin D deficien-

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cy. Therefore, it is important to regularly test vitamin D levels to address any deficiencies proactively. To maintain healthy vitamin D levels, it is necessary to maintain a healthy diet filled with omega-3 polyunsaturated fatty acids such as fish and fortified foods.

Additionally, getting regular and safe sun exposure is crucial for increasing vitamin D levels. The recommended daily intake of vitamin D is 600-800 IU/day for adults, supplementation is recommended to achieve the

desired amount. Maintenance of vitamin D levels is particularly important if undergoing spinal surgery for lumbar spinal stenosis.

Research shows taking supplementation for vitamin D levels results in significantly better outcomes in physical health, mental health, and disability scores compared to patients who do not. Recognizing the role of vitamin D can be transformative in terms of maintaining spine health and improving overall quality of life. l

References 1. Forrest KY, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutr Res. 2011;31(1):48-54.

2. Palacios C, Gonzalez L. Is vitamin D deficiency a major global public health problem? J Steroid Biochem Mol Biol. 2014;144(Pt A):138-145.

3. Kim TH, Lee BH, Lee HM, et al. Prevalence of vitamin D deficiency in patients with lumbar spinal stenosis and its relationship with pain. Pain Physician. 2013;16(2):165-176.

4. Bajaj A, Shah RM, Goodwin AM, Kurapaty S, Patel AA, Divi SN. The role of preoperative vitamin D in spine surgery. Curr Rev Musculoskelet Med. 2023;16(2):48-54.

5. Stoker GE, Buchowski JM, Bridwell KH, Lenke LG, Riew KD, Zebala LP. Preoperative vitamin D status of adults undergoing surgical spinal fusion. Spine (Phila Pa 1976). 2013;38(6):507-515.

6. Mayo BC, Massel DH, Yacob A, et al. A review of vitamin D in spinal surgery: deficiency screening, treatment, and outcomes. Int J Spine Surg. 2020;14(3):447-454. Published 2020 Jun 30. doi:10.14444/7059 7. Khazai N, Judd SE, Tangpricha V. Calcium and vitamin D: skeletal and extraskeletal health. Curr Rheumatol Rep. 2008;10(2):110-117.

8. Wu M, Du Y, Zhang C, et al. Mendelian randomization study of lipid metabolites reveals causal associ-

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ations with heel bone mineral density. Nutrients. 2023;15(19):4160.

9. Johnson CR, Thacher TD. Vitamin D: immune function, inflammation, infections and auto-immunity. Paediatr Int Child Health. 2023;43(4):29-39.

10. Kennel KA, Drake MT, Hurley DL. Vitamin D deficiency in adults: when to test and how to treat. Mayo Clin Proc. 2010;85(8):752-758.

11. Bischoff HA, Stahelin HB, Dick W, et al. Effects of vitamin D and calcium supplementation on falls: a randomized controlled trial. J Bone Miner Res. 2003;18:343-351.

12. Holick MF. Vitamin D status: measurement, interpretation, and clinical application. Ann Epidemiol. 2009;19(2):73-78.

13. Cai C. Treating vitamin D deficiency and insufficiency in chronic neck and back pain and muscle spasm: a case series. Perm J. 2019;23:18-241.

14. Al-Rawaf HA, Gabr SA, Alghadir AH. Vitamin D deficiency and molecular changes in circulating microRNAs in older adults with lower back pain. Pain Res Manag. 2021;2021:6662651.

15. Chang SW, Lee HC. Vitamin D and health - the missing vitamin in humans.

Pediatr Neonatol. 2019;60(3):237-244.

16. Nagaria TD, Shinde RK, Shukla S, Acharya S, Acharya N, Jogdand SD. The sunlight-vitamin D connection:

implications for patient outcomes in the surgical intensive care unit.

Cureus. 2023;15(10):e46819.

17. American Geriatrics Society Workgroup on Vitamin D Supplementation for Older Adults. Recommendations abstracted from the American Geriatrics Society Consensus Statement on Vitamin D for Prevention of Falls and Their Consequences. J Am Geriatr Soc. 2014;62(1):147-152.

18. Tripkovic L, Lambert H, Hart K, et al.

Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. Am J Clin Nutr. 2012;95(6):1357-1364.

19. Srivastava SB. Vitamin D: do we need more than sunshine? Am J Lifestyle Med. 2021;15(4):397-401.

20. Ohta H, Kuroda T, Onoe Y, et al. The impact of lifestyle factors on serum 25-hydroxyvitamin D levels: a cross-sectional study in Japanese women aged 19-25 years. J Bone Miner Metab. 2009;27(6):682-688. doi:10.1007/s00774-009-0095-1 21. Ko S, Chae S, Choi W, Kwon J, Choi JY. The effectiveness of vitamin D supplementation in functional outcome and quality of life (QoL) of lumbar spinal stenosis (LSS) requiring surgery.

J Orthop Surg Res. 2020;15(1):117. doi:10.1186/s13018-020-01629-2

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SURGEON FOCUS

From the Department of Orthopaedic Surgery at UC Davis School of Medicine in Sacramento, California.

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When Peak Performers Stumble Surgical Complications in Spine Surgery and Compassion for the Second Victim Healthcare professionals, particularly those in high-stakes env ironments like spine surger y, are at the forefront of complex patient care and are thus susceptible to profound emotional and psychological impacts when adverse events occur. The term “second victim” was first introduced by Wu in 20001 to describe healthcare providers who experience emotional trauma following a patient-related adverse event. The first victim is the patient who is struggling with the untoward effects of the complication, while the third victim is the health system where the event occurred.

Second victim syndrome (SVS) refers to the emotional and psychological trauma experienced by healthcare providers who are directly responsible for an adverse patient event. The prevalence of SVS among surgeons is notably high due to the highst ress a nd hig h-pressure env ironment and the inherent risks and complexities of surgical procedures. Studies indicate approximately 30% to 50% of surgeons experience symptoms associated with SVS at some point in their careers.2 Spine surgeons are acutely prone to losing confidence and second-guessing their skills, and symptoms can range from acute stress reactions to long-term psychological conditions such as anxiety, depression, burnout, excessive caution, communication breakdown, and

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posttraumatic stress disorder Safdar N. Khan, MD (PTSD). However, in promptly approaching the second victim in a nonjudgmental manner, one can ensure compassion and peer support to prevent the development of depression, burnout, and emotional exhaustion.

Factors Contributing to SVS in Spine Surgery High-Pressure Environment Spine surgery is a high-pressure specialty where the margin for error is minimal.

Surgeons are often expected to perform complex procedures with precision, and any deviation from the expected outcome can lead to pat ient complicat ions. Additionally the culture of “preop/postop” conferences is often highly judgmental and punitive with little support provided to untoward outcomes.

Adverse Events Adverse events, such as surgical complications, patient deaths, or near misses, are significant triggers for SVS. Surgeons often feel personally responsible for these outcomes, leading to intense feelings of guilt and self-doubt. Such events can lead to loss of confidence in surgical ability and are t ypically coupled concurrently with

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impaired clinical judgement, improper decision-making, and communication failures.

Professional Expectations The culture of perfectionism and high expectations in the spine surgery profession can exacerbate feelings of failure when adverse events occur. Surgeons may fear reputational damage, litigation, and loss of professional standing. This can be exacerbated within a toxic culture where colleague surgeons assume intent and look at any adverse event with a monochromatic lens.

Lack of Support The stigma associated with admitting emotional distress or seeking help can prevent spine surgeons from accessing necessary support. Additionally, institutional support systems may be inadequate or non-existent, leaving spine surgeons to cope with SVS on their own. It is extremely important for divisional and departmental leaders to codify a compassion-centric pathway of nonjudgmental peer support and a nonpunitive action plan to help struggling surgeons.

Effects of Second Victim Syndrome The impact of SVS on surgeons can be profound and multifaceted, impacting psychological health, professional performance, and personal relationships. 3 • Psychological Impact: Spine surgeons experiencing SVS may suffer from anxiety, depression, and PTSD. These conditions can affect their mental health and overall

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well-being. In addition, empathy exhaustion and depersonalization may occur with a lower sensation of personal accomplishment.

• Professional Performance: SVS can lead to decreased job satisfaction, burnout, and reduced clinical performance. Spine surgeons may become overly cautious, leading to delays in decision-making and procedural hesitations, which may cause a domino effect of further adverse events.

• Personal Relationships: The emotional toll of SVS can spill over into surgeons' personal lives, affecting relationships with family, colleagues, and friends. The stress and anxiety associated with SVS can lead to social withdrawal and strained personal interactions.

Strategies for Mitigation and Support Addressing SVS requires a multifaceted approach involving individual, peer, and institutional support.4 It is incumbent on div isional, depar t mental, and hospital leadership to ident if y surgeons at r isk immediately after the adverse event occurs, set up a peer support system within 12 to 24 hours, and approach the actual adverse events with a lens of compassion and curiosity. When the surgeon is ready and capable, a nonjudgmental root cause analysis with full operational transparency is a must.

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SURGEON FOCUS

Individual Strategies Spine surgeons should be encouraged to seek professional help, such as counseling or therapy, to address the emotional impact of adverse events. It is essential to practice mindfulness, use stress management techniques, and maintain a healthy work-life balance.

Peer Support Creating a culture of openness and support within spine surgical teams is crucial and perhaps the most important part of the process. Peer support programs, such as mentorship and nonjudgmental debriefing sessions, can provide surgeons with a safe space to share their experiences and receive emotional support as well as technical advice. Such programs do not occur in toxic environments with a “gotcha culture,” and leaders must be educated and trained to prevent such occurrences.

Institutional Support Healthcare institutions should develop comprehensive support systems for spine surgeons, including access to mental health

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services, regular training on coping strategies, and policies that promote a nonpunitive response to adverse events. Establishing a second victim support program can ensure that affected spine surgeons receive timely and appropriate assistance.

Identification of any toxic individuals who tr y to weaponize complications/adverse events against the second victim should be dealt with accordingly.

Conclusion SVS is a significant issue in the field of spine surgery, with the potential to impact the mental health, professional performance, and personal lives of spine surgeons. This issue affects both experienced and inexperienced surgeons equally. Recognizing the prevalence and effects of SVS is the first step toward addressing this critical issue.

By implementing effective support systems, deconstructing toxic environments, and fostering a culture of openness and support, the surgical profession can better support its practitioners and mitigate the impact of adverse events regarding their well-being. l

References 1. Wu AW. Medical error: the second victim. The doctor who makes the mistake needs help too. BMJ. 2000;320(7237):726-727.

2. Seys D, Scott S, Wu A, et al. Supporting involved health care professionals (second victims) following an adverse health event: a literature review. Int J Nurs Stud. 2013;50(5):678-687.

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3. Waterman AD, Garbutt J, Hazel E, et al. The emotional impact of medical errors on practicing physicians in the United States and Canada. Jt Comm J Qual Patient Saf. 2007;33(8):467-476.

4. Scott SD, Hirschinger LE, Cox KR, McCoig M, Brandt J, Hall LW. The natural history of recovery for the healthcare provider “second victim” after adverse patient events. Qual Saf Health Care. 2009;18(5):325-330.

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

Neuraxial Anesthesia and Regional Nerve Blocks Jonathan Markowitz, MD

What Is Being Utilized to Decrease Postoperative Spine Pain?

R e g i o n a l a n e s t h e s i a (R A) , which includes bot h neura xia l a nest hesia a nd reg iona l nerve blocks, is an anesthetic technique employed in spine Gregory Lopez, MD su rger y to prov ide ef fec t ive pain management and enhance patient outcomes. The literature has noted numerous advantages of R A over genera l anesthesia (GA), including reduced risk of respirator y complications, improved hemody namic stabilit y, reduced blood loss, decreased postoperative cognitive dysfunction, and reduced rates of venous thrombosis. Centers are employing Enhanced Recovery After Surgery protocols that streamline patient processes before, during, and after surgeries. These protocols generally include regional or neura x ial anesthesia to shorten the length of inpatient stays and facilitate early mobilit y and recovery while improving outcomes and patients’ overall experiences. In this article, we review the various neuraxial and regional nerve blocks currently employed to decrease postoperative pain, decrease perioperative anesthetic morbidit y, and increase patient satisfaction for patients undergoing spine surgery.

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Neuraxial Anesthesia Neuraxial anesthesia, which includes both epidural anesthesia (EA) and spinal anesthesia (SA), involves the administration of local anesthetic and/or opioid into the epidural (EA) or subarachnoid space (SA).

The injection of local anesthetic into the cerebrospinal f luid provides anesthesia, analgesia, as well as motor and sensor y blockade. SA is typically administered as a single injection and must be given below the level of the conus medullaris to avoid injury to the spinal cord. EA can be given anywhere along the vertebral column and can be administered continuously through a catheter. This allows for the redosing of the anesthetic during and potentially after surgery, providing continuous pain relief.

Neuraxial anesthesia has several proposed advantages over GA. It has been associated with reduced intraoperative blood loss, lower mortality, fewer hypoxic episodes in the post-anesthesia care unit, and a decreased incidence of postoperative cognitive dysfunction.1-3 In the context of spine surgery, spinal anesthesia, when compared to GA, has been show n to lower postoperative pain scores, 2,4,5 improve levels of patient satisfaction,4-6 and decrease postoperative

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nausea and vomiting (PONV). 5,6 The literature has also shown that combined EA/GA with postoperative EA produced better pain control, less bleeding, and lower surgical stress response than GA with postoperative systemically administered narcotics.7 While neuraxial anesthesia has demonstrated some perioperative and postoperative benefits, as described above, it is still not widely accepted for spine procedures, and GA remains the most frequently used anesthetic technique for several reasons, such as a greater acceptance of GA by patients, as well as the fact that GA allows for more flexible management of the anesthetic duration during surgery. Many anesthesiologists prefer GA because it provides a more secure air way, especially before the patient is positioned in the prone position. If an epidural catheter is placed, it is generally in the operating field and can be an obstacle during surgery. Although a continuous infusion of anesthetic through a catheter can reduce postoperative pain scores, patients are often restricted to bed rest while the catheter is in place due to the motor blockade it induces below the level of anesthesia. These various factors have limited the use of neuraxial anesthesia for spine surgery.

Regional Nerve Block Modalities Thoracic and Lumbar Regional Anesthetic Blocks Erector Spinae Plane Block The erector spinae plane block (ESPB) is a relatively newer regional anesthetic

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technique first described in 2016. 8 It has garnered a lot of attention because of its ease of administration and relative safety. 9 The ESPB is a fascial plane block that deposits local anesthetic in the fascial plane between the erector spinae muscle group and the transverse process of the vertebra.

ESPBs consistently block the dorsal rami of the exiting spinal nerves that innervate the vertebra, skin, and dorsal musculature, thus providing somatic analgesia. There is extensive cranial and caudal spread through the paraspinal musculature through a single injection point, allowing for analgesic coverage of multiple vertebral levels with a single injection. A local anesthetic may also diffuse anteriorly to the ventral rami of the spinal nerves facilitating visceral analgesia.

A n ESPB is com mon ly ad m i n istered under ultrasound guidance. A needle is advanced toward the transverse process in a craniocaudal direction and confirmed by the linear spread of the injected anesthetic solution between the transverse process and the erector spinae muscle.10 Most studies have described a single shot of 10 to 30 mL of 0.25%-0.5% bupivacaine/ levobupivacaine or 0.25%-0.5% ropivacaine as the agent of choice.10 While an ESPB is commonly administered preoperatively by an anesthesia provider under ultrasound guidance, surgeons can administer this block under fluoroscopic guidance prior to making an incision or during the surgical procedure.

The ESPB is the most well-studied regional nerve block for patients undergo-

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The literature has noted numerous advantages of regional anesthesia over general anesthesia, including reduced risk of respiratory complications, improved hemodynamic stability, reduced blood loss, decreased postoperative cognitive dysfunction, and reduced rates of venous thrombosis.

ing spinal surgery. Multiple randomized controlled trials and meta-analyses have demonstrated that patients who receive a n ESPB repor t reduced postoperat ive pain scores, lower postoperative opioid consumption, fewer episodes of PON V, reduced opioid-related adverse effects, and better patient satisfaction compared with control groups. 5,10-13 Not only is the ESPB effective for posterior-only procedures, but the literature also shows that this block is associated with decreased postoperative inpatient opioid requirements and a shorter length of stay for patients undergoing circumferential fusions via anterior lumbar interbody fusion (ALIF) with concomitant posterior open procedures.14 While there is a theoretical concern that an ESPB may cause motor deficits due to potential anesthetic spread to the lumbar nerve roots, a clinically significant motor block is rarely, if ever, reported in the literature. Most studies emphasize the block's effectiveness in providing sensory analgesia without causing major motor impairment.

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Thoracolumbar Interfascial Plane Block T he t horacolu mba r i nter fascia l pla ne (TLIP) block was first described in 201515 and targets the dorsal rami of the thoracolumbar nerves. This is a more superficial injection compared to the ESPB and i nvolves i nject i ng a nest het ic bet ween the multifidus and longissimus muscles, aiming to block the branches of the dorsal rami as they traverse this intermuscular plane. The modified TLIP (mTLIP) block, which is performed laterally to the standa rd T LIP block, is a lso descr ibed. In this technique, a needle is advanced in a mediolateral orientation, and anesthetic is administered between the longissimus and iliocostal muscles.

The TLIP block has gained attention as an effective alternative to the ESPB due to several purported advantages. First, some believe that the TLIP block targets a more defined and reliable plane. Because t he primar y site of inject ion and loca l anesthetic deposition in the TLIP block is somewhat farther from the lumbar nerve roots and plexus compared to the ESPB, there is a theoretical lower risk of motor blockade and interference with intraoperative neuromonitoring. Additionally, by focusing on the interfascial plane where the lumbar nerve roots exit, the TLIP block may provide superior analgesia.

W hile t he available literat ure on t he TLIP block is less abundant than that on ESPBs, st ud ies demonst rate t hat T LIP blocks reduce pain scores at rest and with movement for up to 24 hours, decrease

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total analgesic consumption, and lower the incidence of PONV.16,17 Wang et al conducted a randomized controlled trial (RCT) comparing ESPB, TLIP, and a control group (no block) for patients undergoing 2- to 3-level lumbar fusion surgeries. They found that patients who underwent an ESPB had better analgesic effects, lower pain scores in stat ic states, and a lower f requenc y of patient-controlled analgesia requirements and opioid analgesic consumption compared with those who underwent the TLIP block.18 A second RCT by Cifti et al randomized 90 patients undergoing lumbar microdiscectomy into three groups: ESPB, mTLIP, and cont rol. They found that postoperative opioid consumption was significantly lower in both the ESPB and mTLIP groups compared to the control group. However, there was no significant difference in intra- and postoperative opioid consumption between the ESPB and mTLIP groups.19 The authors concluded that there is no superiority between ESPB and mTLIP but that either block is superior to not receiving one.19 Further high-quality randomized studies are needed to compare the results of these blocks.

Transversus Abdominis Plane Block The transversus abdominis plane (TAP) block is a regional anesthetic technique f irst descr ibed in 2001 as a met hod of prov iding analgesia for abdominal surgeries. 20 The TAP block is now being used as part of multimodal analgesia protocols for patients undergoing anterior and lateral lumbar f usions. 21,22 The TA P block

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utilizes ultrasonography to administer a single injection of local anesthetic in the potential space between the transversus abdominis and internal oblique muscles, which allows for effective analgesia to the anterior and lateral abdominal wall.

The literature reports mixed findings regarding whether a TAP block improves outcomes and reduces postoperative opioid consumption. Multiple retrospective st udies have demonst rated sig nif icant benefits of a TAP block after ALIF, including significantly shorter length of stay, less PONV, and lower opioid consumption. 22,23 In contrast, Coquet et al conducted an RCT in which patients were randomized to receive a TAP block performed at the end of surgery with either ropivacaine or a placebo (isotonic saline). They found that the TAP block, regardless of whether ropivacaine or placebo was used, provided similar postoperative analgesia between the groups. 24 Larger RCTs are essential to establish the safet y and efficacy of TAP block s for a nter ior a nd latera l lu mba r interbody fusions.

Cervical Regional Anesthetic Blocks Regional anesthetic blocks are less commonly employed for cervical spine surgery than for thoracic and lumbar spine surgery.

Both the multifidus cervicis plane (MCP)25 and inter-semispinal plane (ISP) 26 blocks have been descr ibed to help decrease postoperative pain and opioid requirements for patients undergoing posterior cer v ica l spine surger y. The a nest het ic agent targets the branches of the dorsal

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rami of cervical nerves traversing in the intermuscular plane.

The MCP block was first described as a case report of cervical laminoplasty perioperative analgesia and exploited the fascial plane bet ween multif idus cer v ices and semi-spinalis cervices muscles at the level of the C5 spinous process. 25 The ISP block is more superficial, and local anesthetic is deposited between the semispinalis cervicis and semispinalis capitis muscles. In one study, patients undergoing posterior cervical spine surgery were randomized to receive either GA alone (the control group) or bilateral ultrasound-guided ISP blocks at the C5 level with 20 mL of bupivacaine 0.25% in each side with GA (the ISP group).

The authors found that after 30 minutes, 6 hours, 8 hours, and 12 hours postoperatively, the visual analog scale (VAS) scores of patients in the ISP group were considerably lower than those of patients in the control group. 27 While this study shows promising results, further high-quality studies are necessary to prove their efficacy and make these blocks more mainstream.

The cervical plexus block (CPB) is a regional anesthetic technique that can be used in anterior cervical spine surgery as a part of the multimodal treatment plan to mitigate postoperative pain. The cervical plexus is formed by the anterior rami of C1-4 and lies deep to the prevertebral fascia on the scalenus medius muscle. To perform a CPB, an ultrasound probe is centered over the posterior edge of the sternocleidomastoid. The cervical plexus is identified through the interscalene groove, and about

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15 mL of anesthetic solution is injected, anesthetizing 4 superficial branches of the cervical plexus. 28 In a single-center RCT, 46 patients were randomized to either receive a superficial cervical plexus block or no block. The authors found that while early quality of recovery improved, measured by a 40-item quality of recovery questionnaire, both groups had similar opioid consumption and discharge times. 29

Conclusion Neuraxial anesthesia and regional nerve blocks represent valuable techniques in the management of postoperative pain for patients undergoing spine surgery. Techniques such as the ESPB and TLIP have demonstrated efficacy in reducing pain scores and opioid consumption and enhancing patient satisfaction. However, the effectiveness of these blocks can vary depending on the technique, surgical procedure, and patient factors. W hile some blocks, such as the ESPB, show promise for reducing pain and improving recovery outcomes, other regional blocks require further high-quality research to establish their full potential. As the field of regional anesthesia continues to evolve, it is essential to refine these techniques through continued investigation, allowing clinicians to tailor pain management strategies to the individual needs of spine surgery patients.

Ultimately, the integration of regional anesthesia into multimodal analgesia protocols holds significant potential for improving outcomes, accelerating recovery, and enhancing the overall surgical experience for patients undergoing spine procedures. l

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References 1. Lee JK, Park JH, Hyun SJ, Hodel D, Hausmann ON. Regional anesthesia for lumbar spine surgery: can It be a standard in the future? Neurospine. 2021:18(4):733-740.

2. Attari MA, Mirhosseini SA, Honarmand A, Safavi MR. Spinal anesthesia versus general anesthesia for elective lumbar spine surgery: a randomized clinical trial. J Res Med Sci. 2011;16(4):524-9.

3. Greenbarg PE, Brown MD, Pallares VS, Tompkins JS, Mann NH. Epidural anesthesia for lumbar spine surgery.

J Spinal Disord. 1988;1(2):139-43.

4. Baenziger B, Nadi N, Doerig R, et al.

Regional versus general anesthesia: effect of anesthetic techniques on clinical outcome in lumbar spine surgery: a prospective randomized controlled trial. J Neurosurg Anesthesiol. 2020;32(1):29-35.

5. De Cassai A, Bonvicini D, Correale C, Sandei L, Tulgar S, Tonetti T. Erector spinae plane block: a systematic qualitative review. Minerva Anestesiol. 2019;85(3):308-319.

6. Vural C, Yorukoglu D. Comparison of patient satisfaction and cost in spinal and general anesthesia for lumbar disc surgery. Turk Neurosurg. 2014;24(3):380-384.

7. Ezhevskaya AA, Mlyavykh SG, Anderson DG. Effects of continuous epidural anesthesia and postoperative epidural analgesia on pain management and stress response in patients undergoing major spinal surgery. Spine (Phila Pa 1976). 2013;38(15):1324-30.

8. Forero M, Adhikary SD, Lopez H, Tsui C, Chin KJ. The erector spinae plane block: a novel analgesic technique in thoracic neuropathic pain. Reg Anesth Pain Med. 2016;41(5):621-7.

9. Rizkalla JM, Holderread B, Awad M, Botros A, Syed IY. The erector spinae plane block for analgesia after lumbar spine surgery: a systematic review. J Orthop. 2021;24:145-150.

10. Liang X, Zhou W, Fan Y. Erector spinae plane block for spinal surgery: a systematic review and meta-analysis.

Korean J Pain. 2021;34(4):487-500.

11. Singh S, Choudhary NK, Lalin D, Verma VK. Bilateral ultrasound-guided erector spinae plane block for postoperative analgesia in lumbar spine surgery: a randomized control trial. J Neurosurg Anesthesiol. 2020;32(4):330-334.

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12. Finnerty D, Eochagáin AN, Ahmed M, Poynton A, Butler JS, Buggy DJ. A randomised trial of bilateral erector spinae plane block vs. no block for thoracolumbar decompressive spinal surgery.

Anaesthesia. 2021;76(11):1499-1503.

22. Reisener MJ, Hughes AP, Okano I, et al.

The association of transversus abdominis plane block with length of stay, pain and opioid consumption after anterior or lateral lumbar fusion: a retrospective study. Eur Spine J. 2021;30(12):3738-3745.

13. Zhu L, Wang M, Wang X, Wang Y, Chen L, Li J. Changes of opioid consumption after lumbar fusion using ultrasound-guided lumbar erector spinae plane block: a randomized controlled trial. Pain Physician. 2021;24(2):E161-e168.

23. Esmende SM, Solomito MJ, Eisler, et al.

Utility of the transversus abdominis plane and rectus sheath blocks in patients undergoing anterior lumbar interbody fusions. Spine J. 2022;22(10):1660-1665.

14. Colón LF, Miles D, Scheinberg M, Wilson A, Shepherd B, Miller J. Erector spinae plane blocks for circumferential lumbar spinal fusion: retrospective cohort study.

Int J Spine Surg. 2023;17(5):715-720.

15. Hand WR, Taylor JM, Harvey NR, et al.

Thoracolumbar interfascial plane (TLIP) block: a pilot study in volunteers. Can J Anaesth. 2015;62(11):1196-200.

16. Long G, Liu C, Liang T, Zhan X. The efficacy of thoracolumbar interfascial plane block for lumbar spinal surgeries: a systematic review and meta-analysis.

J Orthop Surg Res. 2023;18(1):318.

17. Chen K, Wang L, Ning M, Dou L, Li W, Li Y. Evaluation of ultrasound-guided lateral thoracolumbar interfascial plane block for postoperative analgesia in lumbar spine fusion surgery: a prospective, randomized, and controlled clinical trial. PeerJ. 2019;7:e7967.

18. Wang L, Wu Y, Dou L, Chen K, Liu Y, Li Y. Comparison of two ultrasound-guided plane blocks for pain and postoperative opioid requirement in lumbar spine fusion surgery: a prospective, randomized, and controlled clinical trial. Pain Ther. 2021;10(2):1331-1341.

19. Ciftci B, Ekinci M, Celic EC, Yayik AM, Aydin ME, Ahiskalioglu A. Ultrasound-guided erector spinae plane block versus modified-thoracolumbar interfascial plane block for lumbar discectomy surgery: a randomized, controlled study. World Neurosurg. 2020;144:e849-e855.

24. Coquet A, Sion A, Bourgoin A, Ropars M, Beloeil H. Transversus abdominis plane block for anterior lumbar interbody fusion: a randomized controlled trial. Spine J. 2023;23(8):1137-1143.

25. Ohgoshi Y, Izawa H, Kori S, Matsukawa M. Multifidus cervicis plane block is effective for cervical spine surgery.

Can J Anaesth. 2017;64(3):329-330.

26. Ohgoshi Y, Nishizakura R, Takahashi Y, et al. Novel ultrasound-guided inter-semispinal plane block: a comparative pilot study in healthy volunteers.

J Anesth. 2018;32(1):143-146.

27. Mostafa SF, Abu Elyazed MM, Eid GM, Belal AM. Inter-semispinal plane (ISP) block for postoperative analgesia following cervical spine surgery: a prospective randomized controlled trial. J Clin Anesth. 2022;83:10974.

28. Mulcahy MJ, Elalingam T, Jang K, D’Souza M, Tait M. Bilateral cervical plexus block for anterior cervical spine surgery: study protocol for a randomised placebo-controlled trial. Trials. 2021;22(1):424.

29. Mariappan R, Mehta J, Massicotte E, et al. Effect of superficial cervical plexus block on postoperative quality of recovery after anterior cervical discectomy and fusion: a randomized controlled trial.

Can J Anaesth. 2015;62(8):883-890.

20. Rafi AN. Abdominal field block: a new approach via the lumbar triangle.

Anaesthesia, 2001;56(10):1024-1026.

21. Colón LF, White CC, Miles DT, et al. Transversus abdominis plane block as part of a multimodal analgesic regimen in patients undergoing anterior lumbar interbody fusion: a retrospective cohort study.

Int J Spine Surg. 2023;17(3):426-433.

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

Role of Psychosocial Factors in Chronic Low Back Pain A Contemporary Review Luis M. Salazar, MD

Chronic low back pain represents a significant global health burden, with annual healthcare expenditures exceeding $90 billion in the United States alone.1 While anatomical and biomechanical factors contribute to Vincent P. Federico, MD pain genesis, mounting evidence demonstrates that psychosocial factors play a crucial role in pain chronification and treatment outcomes. 2 The present review synthesizes current evidence regarding the complex interplay Arash Sayari, MD between psychological, social, and biological factors in chronic low back pain, with particular emphasis on implications for surgical decision-making and perioperative care.

The Biopsychosocial Model of Pain Contemporary understanding of chronic low back pain has evolved from a purely biomechanical model to the recognition of pain as a complex biopsychosocial phenomenon. 3 Psychological distress and chronic pain demonstrate a bidirectional relationship— pain can trigger or exacerbate psychological symptoms, while pre-existing psychological conditions may amplify pain perception and disability.4 This relationship appears

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particularly relevant in degenerative spine conditions, where objective pathology often correlates poorly with symptom severity.

Psychological Risk Factors: Depression and Anxiety Studies have reported rates of preoperative depression in patients undergoing spine surgery ranging from 29% to 54%, which may significantly affect surgical outcomes.5 A recent study by Deshpande et al involving patients from the Michigan Spine Surgery Improvement Collaborative registry who underwent lumbar spine surgery demonstrated that patients with anxiety and depression reported worse baseline and postoperative back and leg pain resolution.6 Patients solely with depression faced over a 30% higher risk of readmission compared to those without depression or anxiet y. 6 Furthermore, in a 10-year longitudinal study, Tuomainen et al found that patients who underwent surgery for lumbar spinal stenosis and who had preoperative depression exhibited persistently worse outcomes in terms of pain and disability compared to patients without depression.7 Additionally, a recent systematic review of 44 studies examining the impact of preoperative depression on outcomes after lumbar spine surgery revealed that while patients with depression showed compa-

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rable improvements in disability, pain, and physical function, their overall outcomes remained poorer. 8 Notably, patients with depression experienced a similar extent of improvement in their depressive symptoms compared to those without depression.8 However, these patients had worse postoperative depression severity. Therefore, identifying patients with preoperative depression may help improve outcomes in this challenging population. Collectively, these findings may be related to the known association between depression and inadequately controlled pain postoperatively.9 Similarly, previous research has suggested an association between preoperative anxiety and postoperative pain intensity.10 Pain-related anxiety and avoidance behavior are physiological responses following an acute incident. However, maladaptive coping mechanisms, such as catastrophizing and fear-avoidance behaviors, can contribute to the development or persistence of anxiety and depression after spine surgery.11 The fear-avoidance model suggests that catastrophizing leads to pain-related fear, resulting in activity avoidance and subsequent physical deconditioning.11 This cycle appears especially relevant in musculoskeletal conditions, where fear of movement can perpetuate disability independent of pain intensity. Therefore, the bidirectional relationship between pain and anxiety may create a negative feedback loop that could impair recovery if not adequately addressed.4 This also may explain why anxiety disorders demonstrate a significant association with chronic postsurgical pain, with meta-analy-

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ses suggesting a 55% to 110% increased risk of developing chronic postsurgical pain in patients with anxiety across various surgical procedures.10

Preoperative Optimization Strategies Addressing psychosocial factors preoperatively through cognitive behavioral therapy (CBT), mindfulness-based stress reduction, and pain neuroscience education has shown promise in improving pain and disability in the short term.12 While limited evidence exists regarding the impact of preoperative psychological intervention on lumbar spine surger y outcomes, several studies have examined this relationship in cervical spine procedures. In a prospective study of 27 patients undergoing anterior cervical discectomy and fusion (ACDF), Adogwa et al demonstrated significantly improved postoperative neck pain at 1-year follow-up among patients who received preoperative anxiety treatment compared to untreated controls.13 Similarly, Elsamadicy et al evaluated 140 ACDF patients, including 25 with preoperative depression who underwent psychological intervention.14 At 24-month follow-up, treated patients showed comparable objective and patient-reported outcomes to those without depression, suggesting that preoperative psychological optimization may help mitigate historically observed outcome disparities. While these findings suggest potential benefits of psychological intervention, the optimal timing, duration, and specific treatment protocols remain undefined and warrant further investigation through well-designed prospective studies.

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Pain-related anxiety and avoidance behavior are physiological responses following an acute incident.

However, maladaptive coping mechanisms, such as catastrophizing and fearavoidance behaviors, can contribute to the development or persistence of anxiety and depression after spine surgery.

Access to Psychological Care and Healthcare Disparities While evidence supports the value of preoperative psychological optimization, access to mental health services varies significantly across populations. Mental health providers with expertise in chronic pain are not uniformly available, and insurance coverage for psychological services remains variable.

Language barriers and cultural factors may further complicate psychological screening and intervention. For example, validated translations of common screening tools may not be available in all languages, and cultural differences in expressing psychological distress may affect the interpretation of standard assessments.15 Therefore, cultural background and health literacy may inf luence expectations and how patients communicate about their symptoms and

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satisfaction.16 Structured preoperative education programs that address both physical and psychological aspects of recovery, delivered in a culturally competent manner, may help align expectations with likely outcomes.

These disparities in access to psychological care parallel broader inequities in spine care delivery. An analysis of 9941 patients with lumbar spondylolisthesis revealed that Black, Indigenous, and People of Color (BIPOC) were 32% less likely to receive surgical intervention despite reporting higher baseline pain interference scores. 2 This disparity highlights systemic barriers to equitable spine care access, such as implicit provider bias and socioeconomic obstacles.

Similarly, Medicaid beneficiaries demonstrated significantly lower odds of achieving minimal clinically important difference (MCID) in pain and disability compared to

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privately insured patients. Addressing these inequities requires healthcare systems to implement culturally tailored education programs, increase diversity among spine care providers, and ensure policy changes that promote insurance parity and access to specialized care.

Patient Expectations and Satisfaction Patient expectations significantly influence satisfaction with surgical outcomes. Studies show that patients with depression and anxiety often report different expectations regarding postoperative pain improvement compared to those without mental health conditions. Notably, while patients with greater preoperative pain might intuitively be expected to have higher expectations for improvement, research suggests the opposite pattern. Jacob et al found that patients with worse mental health scores demonstrated lower expectations for pain improvement, despite having higher baseline pain levels following lumbar fusion.17 This counterintuitive finding may be explained by the psychological impact of chronic pain combined with depression—specifically, the hopelessness often experienced by patients with depression may lead them to have reduced expectations for symptom improvement.

Postoperative Rehabilitation Considerations Psychological factors significantly influence engagement in postoperative rehabilitation, with implications that vary across racial and ethnic groups. Studies demonstrate that patients with elevated anxiety or cat-

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astrophizing scores show lower adherence to physical therapy and increased activity avoidance due to fear of pain.18 Enhanced recovery after surgery (ERAS) protocols that incorporate psychological support and standardized pain coping strategies show promise in improving rehabilitation participation and outcomes.19 However, recent evidence suggests that even with standardized ERAS protocols, significant disparities persist in postoperative outcomes between racial/ ethnic groups.

Research indicates that BIPOC patients face greater challenges during the rehabilitation period, with significantly longer hospital stays (3.8 vs 3.4 days) and higher rates of discharge to rehabilitation facilities compared to White patients (20.9% vs 11.8%).20 These disparities persist even after controlling for comorbidities, suggesting that social determinants of health and systemic barriers play important roles. ERAS protocols present an opportunity to provide consistent, high-quality postoperative care, but evidence shows that adherence to preoperative process measures may be lower among non-White patients (24.2% vs 36.6%). 20 Early identification of high-risk patients using validated tools like the Risk Assessment and Prediction Tool along with culturally competent delivery of rehabilitation services may help address these disparities. 20

Future Directions and Conclusion Several opportunities exist to improve the integration of psychological care in spine surgery. The development of more sophisticated risk stratification tools incorporating

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MENTAL HEALTH

both psychological and social factors could improve patient selection and guide individualized intervention strategies. Additionally, the implementation of virtual care platforms may help address disparities in access to psychological services. However, careful attention must be paid to the digital divide that may affect certain populations.

Psychological and social factors play crucial roles in the development, persistence, and

treatment outcomes of chronic low back pain.

Comprehensive preoperative screening and targeted interventions addressing these factors appear essential for optimizing surgical outcomes. Future research should focus on developing more sophisticated screening tools, identifying optimal timing for psychological interventions, and addressing healthcare disparities to ensure equitable access to effective treatment. l

References 1. Dieleman JL, Cao J, Chapin A, et al. US health care spending by payer and health condition, 1996-2016.

JAMA. 2020;323(9):863-884.

2. Massaad E, Mitchell TS, Duerr E, et al. Disparities in surgical intervention and health-related quality of life among racial/ethnic groups with degenerative lumbar spondylolisthesis.

Neurosurgery. 2024;95(3):576-583.

3. Gatchel RJ, Peng YB, Peters ML, Fuchs PN, Turk DC. The biopsychosocial approach to chronic pain: scientific advances and future directions. Psychol Bull. 2007;133(4):581-624.

4. Gan TJ. Poorly controlled postoperative pain: prevalence, consequences, and prevention. J Pain Res. 2017;10:2287-2298.

5. Purvis TE, Neuman BJ, Riley LH, Skolasky RL. Comparison of PROMIS Anxiety and Depression, PHQ-8, and GAD-7 to screen for anxiety and depression among patients presenting for spine surgery. J Neurosurg Spine. 2019;30(4):524-531.

6. Deshpande N, Hadi M, Mansour TR, et al. The impact of anxiety and depression on lumbar spine surgical outcomes: a Michigan Spine Surgery Improvement Collaborative study. J Neurosurg Spine.

Published online March 1, 2024.

7. Tuomainen I, Pakarinen M, Aalto T, et al. Depression is associated with the long-term outcome of lumbar spinal stenosis surgery: a 10-year follow-up study. Spine J. 2018;18(3):458-463.

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8. Javeed S, Benedict B, Yakdan S, et al.

Implications of preoperative depression for lumbar spine surgery outcomes: a systematic review and meta-analysis.

JAMA Netw Open. 2024;7(1):e2348565.

9. Mohan S, Lynch CP, Cha EDK, et al.

Baseline risk factors for prolonged opioid use following spine surgery: systematic review and meta-analysis. World Neurosurg. 2022;159:179-188.e2.

10. Theunissen M, Peters ML, Bruce J, Gramke HF, Marcus MA. Preoperative anxiety and catastrophizing: a systematic review and meta-analysis of the association with chronic postsurgical pain. Clin J Pain. 2012;28(9):819-841.

11. Held U, Burgstaller JM, Deforth M, Steurer J, Pichierri G, Wertli MM. Association between depression and anxiety on symptom and function after surgery for lumbar spinal stenosis. Sci Rep. 2022;12(1):2821.

12. Scarone P, Van Santbrink W, Koetsier E, Smeets A, Van Santbrink H, Peters ML. The effect of perioperative psychological interventions on persistent pain, disability, and quality of life in patients undergoing spinal fusion: a systematic review. Eur Spine J. 2023;32(1):271-288.

13. Adogwa O, Elsamadicy AA, Cheng J, Bagley C. Pretreatment of anxiety before cervical spine surgery improves clinical outcomes: a prospective, single-institution experience. World Neurosurg. 2016;88:625-630.

14. Elsamadicy AA, Adogwa O, Cheng J, Bagley C. Pretreatment of depression before cervical spine surgery improves patients’

perception of postoperative health status: a retrospective, single institutional experience. World Neurosurg. 2016;87:214-219.

15. Chen Q, Vella SP, Maher CG, Ferreira GE, Machado GC. Racial and ethnic differences in the use of lumbar imaging, opioid analgesics and spinal surgery for low back pain: a systematic review and meta-analysis. Eur J Pain. 2023;27(4):476-491.

16. Joshi M, Prasad PA, Hubbard CC, et al. Racial, ethnic, and language-based inequities in inpatient opioid prescribing by diagnosis from internal medicine services, a retrospective cohort study.

Pain Res Manag. 2023;2023:1658413.

17. Jacob KC, Patel MR, Park GJ, et al.

Mental health as a predictor of preoperative expectations for pain and disability following lumbar fusion. World Neurosurg. 2022;161:e401-e407.

18. Archer KR, Motzny N, Abraham CM, et al. Cognitive-behavioral–based physical therapy to improve surgical spine outcomes: a case series.

Phys Ther. 2013;93(8):1130-1139.

19. Flanders TM, Ifrach J, Sinha S, et al.

Reduction of postoperative opioid use after elective spine and peripheral nerve surgery using an enhanced recovery after surgery program. Pain Med. 2020;21(12):3283-3291.

20. Howard SD, Aysola J, Montgomery CT, et al. Post-operative neurosurgery outcomes by race/ethnicity among enhanced recovery after surgery (ERAS) participants.

Clin Neurol Neurosurg. 2023;224:107561.

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TECHNOLOGY

From UCI Health in Orange County, California.

21

What Is the Evidence for Bone Growth Stimulators?

The estimated cost spent on bone growth stimulators in 2022 was $1.4 billion.1 The current projections are that expenditures on bone growth stimulators will continue to grow. The use of bone growth stimulators in spine fusion surgeries is a key contributor to the increase in expenditure on bone growth stimulators (Figure 1). However, the health care system is facing numerous challenges, one of which is the rising cost of health care.

As the practice of medicine becomes more expensive, physicians will be asked to find ways to cut costs. So, what is the evidence for the use of bone growth stimulators?

The earliest studies on bone growth stimulators sought to determine their ability to aid in fracture healing. In 1966, Friedenberg and Brighton published an article in The Journal of Bone and Joint Surgery evaluating the effects of sustained direct currents on skin, the periosteum, growing bone, and fractured bone.2 Friedenberg et al subsequently published another article describing the use of direct currents on fracture healing in rabbits.3 The authors concluded that fracture healing was stimulated by the use of direct currents. In 1974, Dw yer and Wick ham published an article describing the use of direct current to assist lumbar spinal fusion.4 The authors used direct current stimulation in 12 patients undergoing lumbar spinal fusion. They achieved successful fusion in 11 of those patients, noting a mature solid

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fusion. In 1988, Kane published an article evaluating the use of Yu-Po Lee, MD direct current bone stimulation in patients undergoing lumbar spinal fusions.5 Kane noted 82 patients in the direct current stimulation group had a successful fusion of 91.5% while a control group had an 80.5% fusion. Kane also had a cohort of patients who were considered challenging patients. Fusion conditions were considered difficult in patients who had one or more previous failed fusions, a grade II or worse spondylolisthesis, multilevel fusion, or the presence of another high-risk factor such as obesity. Successful fusion was achieved in 15 of 28 control patients (54%) compared with 25 of 31 (81%) of patients who were treated with direct current stimulation (p = 0.026).

The concept of bone stimulation w ith electric currents has evolved to pulsed electromagnetic field stimulation and capacitive coupled electrical stimulation because of the advantages of decreased operating time, instrumentation removal, and infection risk. Tong et al studied the cellular effects of pulsed electromagnetic fields on the proliferation and differentiation of osteoblasts.6 Pulsed electromagnetic field stimulation increased the proliferation and differentiation of osteoblasts and related gene expressions, such as insulin-like growth factor 1, alkaline phosphatase, runt-related transcription factor 2, and osteocalcin.

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A

B Figure 1. Lateral lumbar fusion. (A) Anteroposterior view. (B) Lateral view.

Clinical studies have a l s o be en per for me d eva luat i ng t he f usion rates with pulsed electromagnetic fields. Weinstein et al performed a prospective multicenter st udy invest igat ing pulsed electromagnetic f ields as an adjunct therapy to lumbar spinal f usion procedures in 142 patients at risk for pseudarthrosis.7 Patients with a prior failed fusion, multilevel fusion, nicotine use, osteoporosis, or diabetes were considered high risk patients. Fusion status was assessed at 12 mont hs w it h 88.0% of patients (n = 125/142) demonstrating successful fusion. Fusion success for patients with 1, 2+, or 3+ risk factors were

88.5%, 87.5%, and 82.3%, respectively. In another study, Foley et al performed a prospective multicenter randomized study on 323 patients undergoing anterior cervical discectomy and fusion who were either smokers or undergoing multilevel cervical fusion.8 The authors found that at 6 months postoperatively, the pulsed electromagnetic field group had a significantly higher fusion rate than the control group (83.6% vs. 68.6%, p = 0.0065). At 12 months after surgery, the stimulated group had a fusion rate of 92.8% compared with 86.7% for the control group (p = 0.1129). So, while there do seem to be beneficial effects with using a bone growth stimulator at 6 months, there was no significant difference at 1 year.

Hence, there is still some controversy regarding the use of bone growth stimulators.

There is evidence for the use of bone growth stimulators, especially in high-risk patients such as patients with diabetes, smokers, and patients undergoing multilevel fusion.

However, more studies are needed to have a better understanding of the benefit bone growth stimulators truly provide. l

References 1. Bone growth stimulator market to reach $1.4 billion by 2022: growing inclination of patients toward non-invasive and minimally invasive surgical treatments - research and markets [press release]. Markets Insider. May 16, 2017.

2. Friedenberg ZB. Bioelectric potentials in bone. J Bone Jt Surg. 1966;48A:915.

3. Friedenberg ZB, Roberts PG, Didizian NH, Brighton CT. Stimulation of fracture healing by direct current in the rabbit fibula. J Bone Jt Surg. 1971;53A:1400.

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4. Dwyer AF, Wickham GG. Direct current stimulation in spinal fusion.

Med J Aust. 1974;1:73–75.

5. Kane WJ. Direct current electrical bone growth stimulation for spinal fusion. Spine (Phila Pa 1976). 1988;13(3):363-365.

6. Tong J, Sun L, Zhu B, et al. Pulsed electromagnetic fields promote the proliferation and differentiation of osteoblasts by reinforcing intracellular calcium transients.

Bioelectromagnetics. 2017;38(7):541-549.

7. Weinstein MA, Beaumont A, Campbell P, et al. Pulsed electromagnetic field stimulation in lumbar spine fusion for patients with risk factors for pseudarthrosis.

Int J Spine Surg. 2023;17(6):816-823.

8. Foley KT, Mroz TE, Arnold PM, et al.

Randomized, prospective, and controlled clinical trial of pulsed electromagnetic field stimulation for cervical fusion. Spine J. 2008;8(3):436-442.

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From the 1Hospital for Special Surgery and 2 Weill Cornell Medical College, both in New York, New York.

CERVICAL SPINE

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Adjacent Segment Disease Following CDR and Cervical Fusion Over the past decade, total disc arthroplasty via cervical disc replacement (CDR) has continued to gain popularity in cervical spine surgery as a motion-preserving alternative to fusion. One potential contributor to this growth is the concern for the development of adjacent segment degenerat ion (A SDeg) a nd adjacent segment disease (ASDi). Consequently, recent literature has investigated whether TDR offers better protection than fusion.

Hilibrand and Robbins distinguished between ASDeg, which refers to radiological evidence of changes at levels adjacent to

a previous spinal fusion procedure without necessarily correlating to any patient symptoms, and ASDi, where new clinical signs arise that correlate with the radiographic observations of ASDeg adjacent to the level of a previous spinal fusion or other spine procedure (Figure 1).1 ASDeg is a common radiographic finding characterized by signs of degenerative changes and instability, such as loss of disc space height, disc impingement, osteophytosis, listhesis, central or

Adin Ehrlich, BA1

Andrea Pezzi, MD1

Kasra Araghi, BS1

Tomoyuki Asada, MD1,2

Figure 1. Adjacent segment disease in a 56-year-old 2.5 years after undergoing anterior cervical discectomy and fusion (ACDF) for cervical myelopathy. (A) T2-weighted sagittal magnetic resonance image, which shows adjacent segment degeneration at C3-C4. (B) X-ray image showing prior ACDF level.

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Sheeraz A. Qureshi, MD, MBA1,2

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ASDeg and ASDi are significant concerns following cervical spine surgery, with complex, multifactorial etiologies.

foraminal stenosis, and endplate irregularity. 2 ASDi generally involves radiographic signs of ASDeg and may present clinically as an isolated symptom or a combination of symptoms, including myelopathy, axial pain, and radicular pain.1,3 As a result, patients who develop ASDi have poor longterm outcomes and commonly require reoperation procedures to relieve symptoms that their initial surgery was intended to solve. Therefore, understanding the etiology of ASDi and its incidence following CDR and fusion is vital to prevent further operative intervention in this patient population.

Pathophysiology of ASDi Controversy remains over whether adjacent segment patholog y originates from surgical inter vention or if it follows the natural course of the degenerative process.

However, current literature suggests that no single factor alone explains its development.4-6 Instead, several etiologic factors have been proposed as contributors to the patholog y. Cer v ical spine degeneration often begins with age-related changes in the intervertebral discs and facet joints that are ultimately treated with primary CDR or cervical fusion at the most severe level(s)

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and continue at adjacent levels. Following the procedure, existing ASDeg progresses, inf luenced by several interrelated postoperative mechanical factors, including intradiscal pressure changes, anatomical disruption, and biomechanical alterations that result in ASDi when symptomatic.4,7 At the microscopic level, ASDeg is characterized by decreased hydration, reduced proteoglycan content, and loss of elasticity, resulting in microstructural alterations, including annular tears and fissures, which can then lead to a gradual decline in disc height and integrit y. 8 Macroscopically, following cervical fusion, there is a loss of motion at the operated level resulting in an altered mechanical load distribution of the adjacent segments.4,7,9,10 Fused vertebrae act as a single larger vertebra, which engages in compensatory hypermobility with adjacent segments and affects the natural curvature of the spine, leading to sagittal malalignment.7,9,10 In addition, malalignment can also be caused by improper implant size or cervical positioning intraoperatively, which may result in subsidence.11 Although CDR aims to preserve motion at the operative level, it can lead to compensatory hypermobility at adjacent levels.10,12 These alterations in the biomechanical environment increase intradiscal pressure and stress in adjacent discs, promoting further disc degeneration via herniation or collapse.4,7,9,10 Reduced or altered mobility at operated levels may impair microvascular circulation and nutrient diffusion in adjacent segments, accelerating degenerative processes.13 Adjacent facet joints are

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also affected by altered kinematics and increased loads, leading to hypertrophy, inf lammation, and osteophyte formation, which can narrow neural foramina and compress nerve roots.14 Together, existing adjacent disc degeneration at nonoperated levels, biomechanical changes, and facet joint degeneration can result in ASDi at levels that were previously asymptomatic.

Comparing Outcomes of ACDF vs CDR CDR and anterior cervical discectomy and fusion (ACDF) are established surgical treatments for degenerative cervical disc disease.

In single-level procedures, both techniques demonstrated comparable success in alleviating neck and arm pain, enhancing function, and achieving patient satisfaction.

The prevalence of ASDeg and ASDi following cervical procedures has been the subject of ongoing research, with studies reporting varying rates depending on the length of follow-up and specific criteria used for diagnosis.10,12,15-18 Prior studies have reported the incidence of ASDi following anterior cervical discectomy and fusion (ACDF) to be as high as 25.6% within 10 years, with an annual rate of 2.9%.10 More recently, a study of 219 ACDF patients reported a 21% ASDi incidence over a minimum 5-year follow-up, identif ying high BMI, severe osteoporosis, and a large C2-C7 cervical sagittal vertical axis as risk factors.15 Some studies have suggested that the incidence of ASDi may increase over time, potentially affecting long-term outcomes for patients who undergo cervical fusion.4,7

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The high prevalence of ASDi in ACDF patients has led to increased interest in mot ion-preser v ing techniques such as CDR, which aim to maintain more natural biomechanics of the cervical spine and potentially reduce the risk of adjacent segment complications and ASDi.19 Although initial studies showed similar rates of ASDi in ACDF and CDR patients, 20 current meta-analyses of randomized controlled trials with longer follow-up showed that ACDF patients had a higher prevalence beginning around 5 years after surgery based on operation rates.10,21 In addition, there are several studies with at least 2 to 5 years of follow-up that support a lower rate of ASDi in CDR patients, including a meta-analysis by Toci et al, who reported lower rates of ASDeg (14.4% vs. 19.7%), ASDi (3.8% vs. 6.1%), and reoperation (3.1% vs 6.1%) in CDR operations compared to ACDF.12,16-18 In addition to the lower rates of ASDi, CDR has also been shown to have better neck disability index (NDI) improvement, faster cervical range of motion (ROM) recover y, and a lower incidence of radiographic ASDeg changes.

Also, a small cohort study comparing CDR and ACDF for symptomatic ASDi suggested better NDI and ROM recovery in CDR over

CDR has shown lower rates of ASDeg and ASDi compared to ACDF, particularly in studies with longer follow-up periods.

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CERVICAL SPINE

While both CDR and ACDF are effective in treating cervical degenerative disc disease, the motion-preserving nature of CDR may offer long-term advantages in reducing adjacent segment complications.

Although both CDR and ACDF can be effective treatments for multilevel cervical disc disease in single-level operations, multilevel CDR offers significant advantages over ACDF, including better preservation of cer vical motion, lower rates of ASDi, and improved long-term outcomes. These findings support the use of CDR, particularly in multilevel procedures, to optimize patient outcomes. 25,26

ACDF. 2 3 Therefore, despite comparable success in improving pain, the lower rates of ASDi in CDR patients may suggest its superiority over ACDF. In multilevel procedures, the benefits of CDR become more pronounced. A meta-analysis comparing multilevel CDR to ACDF found that patients undergoing CDR ex hibited greater overall cer vical spine motion and reduced rates of ASDi. 9 Additionally, the incidence of adverse events was significantly lower in the CDR group, suggesting that CDR may be a safe and effective surgical strateg y for multilevel cervical degenerative disc disease. 9 Furthermore, long-term studies have reinforced the advantages of CDR in multilevel cases.

Research with 10-year follow-up data has demonstrated that CDR is superior to ACDF in terms of overall success rates, subsequent surgeries, and neurological success. The cumulative risk of adjacent-level surgery was notably lower in the CDR group, indicating a sustained benefit in preserving segmental motion and reducing ASDeg. 24

Conclusion It is important to note that this review focuses primarily on the difference between CDR and cervical fusion in developing ASDi and ASDeg. Despite better outcomes for these pathologies in CDR patients, both procedures have their place in cer vical spine surgery, and the choice between CDR and ACDF should be tailored to individual patient factors, including age, number of levels involved, and specific pathology.

ASDi and ASDeg are common complications of cervical fusion and CDR procedures that can result in additional operations and continued pain. The etiology of ASDi is multifactorial, involv ing age-related changes, biomechanical alterations, and surgical factors. While both CDR and ACDF have demonstrated efficacy in alleviating pain and improving function, long-term outcomes, particularly regarding ASDeg and ASDi, favor CDR as a superior option.

CDR, as a motion-preserving technique, aims to maintain more natural cervical spine biomechanics, producing additional advantages over ACDF, particularly in multilevel procedures. l

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References 1. Hilibrand AS, Robbins M. Adjacent segment degeneration and adjacent segment disease: the consequences of spinal fusion? Spine J. 2004;4.

2. Jeong TS, Son S, Lee SG, Ahn Y, Jung JM, Yoo BR. Comparison of adjacent segment disease after minimally invasive versus open lumbar fusion: a minimum 10-year follow-up. J Neurosurg Spine. 2021;36:525–533.

3. 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;81:519–528.

4. Chung JY, Park JB, Seo HY, Kim SK. Adjacent segment pathology after anterior cervical fusion. Asian Spine J. 2016;10:582–592.

5. Saavedra-Pozo FM, Deusdara RAM, Benzel EC. Adjacent segment disease perspective and review of the literature. Ochsner J. 2014;14:78.

6. Song KJ, Choi BW, Jeon TS, Lee KB, Chang H. Adjacent segment degenerative disease: Is it due to disease progression or a fusion-associated phenomenon?

Comparison between segments adjacent to the fused and non-fused segments.

Eur Spine J. 2011;20:1940–1945.

7. Huang X, Cai Y, Chen K, et al. Risk factors and treatment strategies for adjacent segment disease following spinal fusion [review]. Mol Med Rep. 2025;31:33.

8. Adams MA, Freeman BJC, Morrison HP, Nelson IW, Dolan P. Mechanical initiation of intervertebral disc degeneration. Spine (Phila Pa 1976). 2000;25:1625–1636.

9. Wu TK, Wang BY, Meng Y, et al. Multilevel cervical disc replacement versus multilevel anterior discectomy and fusion: a meta-analysis. Medicine. 2017;96:e6503.

10. Deng Y, Li G, Liu H, Hong Y, Meng Y. Mid- to long-term rates of symptomatic adjacent-level disease requiring surgery after cervical total disc replacement compared with anterior cervical discectomy and fusion: a meta-analysis of prospective randomized clinical trials.

J Orthop Surg Res. 2020;15:468.

11. Yamagata T, Takami T, Uda T, et al.

Outcomes of contemporary use of rectangular titanium stand-alone cages in

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anterior cervical discectomy and fusion: cage subsidence and cervical alignment.

J Clin Neurosci. 2012;19:1673–1678.

12. Chang KE, Pham MH, Hsieh PC. Adjacent segment disease requiring reoperation in cervical total disc arthroplasty: a literature review and update.

J Clin Neurosci. 2017;37:20–24.

13. Stokes IAF, Iatridis JC. Mechanical conditions that accelerate intervertebral disc degeneration: overload versus immobilization. Spine (Phila Pa 1976). 2004;29:2724–2732.

14. Jaumard N V., Welch WC, Winkelstein BA. Spinal facet joint biomechanics and mechanotransduction in normal, injury and degenerative conditions.

J Biomech Eng. 2011;133:71010.

15. Wei Z, Yang S, Zhang Y, Ye J, Chu TW. Prevalence and risk factors for cervical adjacent segment disease and analysis of the clinical effect of revision surgery: a minimum of 5 years’ follow-up [published online July 8, 2023]. Global Spine J. https:// doi.org/10.1177/21925682231185332 16. Toci GR, Canseco JA, Patel PD, et al. The incidence of adjacent segment pathology after cervical disc arthroplasty compared with anterior cervical discectomy and fusion: a systematic review and meta-analysis of randomized clinical trials.

World Neurosurg. 2022;160:e537–e548.

versus anterior cervical discectomy and fusion: a meta-analysis of rates of adjacent-level surgery to 7-year follow-up. J Spine Surg. 2020;6:217–232.

22. Tian W, Yan K, Han X, Yu J, Jin P, Han X. Comparison of the clinical and radiographic results between cervical artificial disk replacement and anterior cervical fusion.

Clin Spine Surg. 2017;30:E578–E586.

23. Lee SB, Cho KS. Cervical arthroplasty versus anterior cervical fusion for symptomatic adjacent segment disease after anterior cervical fusion surgery: review of treatment in 41 patients. Clin Neurol Neurosurg. 2017;162:59–66.

24. Nunley PD, Hisey M, Smith M, Stone MB. Cervical disc arthroplasty vs anterior cervical discectomy and fusion at 10 years: results from a prospective, randomized clinical trial at 3 sites. Int J Spine Surg. 2023;17:230.

25. Liao Z, Fogel GR, Pu T, Gu H, Liu W. Biomechanics of hybrid anterior cervical fusion and artificial disc replacement in 3-level constructs: an in vitro investigation. Med Sc Monitor. 2015;21:3348–3355.

26. Cardoso MJ, Rosner MK. Multilevel cervical arthroplasty with artificial disc replacement. Neurosurg Focus. 2010;28:E19.

17. Zhang Y, Lv N, He F, et al. Comparison of cervical disc arthroplasty and anterior cervical discectomy and fusion for the treatment of cervical disc degenerative diseases on the basis of more than 60 months of follow-up: a systematic review and meta-analysis. BMC Neurol. 2020;20:143.

18. 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;38:2253–2257.

19. Ontario HQ. Cervical artificial disc replacement versus fusion for cervical degenerative disc disease: a health technology assessment. Ont Health Technol Assess Ser. 2019;19:1.

20. Ueda H, Huang RC, Lebl DR. Iatrogenic contributions to cervical adjacent segment pathology. HSS J. 2015;11:26–30.

21. Badhiwala JH, Platt A, Witiw CD, Traynelis VC. Cervical disc arthroplasty

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LUMBAR SPINE

From DISC Sports and Spine Center in Newport Beach, California.

Evolution of Lumbar Disc Replacement in the United States Lumbar disc replacement (LDR) Brandon P. Hirsch, MD continues to gain popularity as a promising motion-preserving surgical treatment option for degenerative disc disease (DDD). While lumbar fusion remains the most common surgical technique used in the treatment of DDD, its limitations—such as adjacent segment degeneration and reduced spinal mobility—have driven interest in motion-preserving technologies. The first LDR device, the Charité artificial disc, was developed in Europe in the early 1980s and gained popularity there in the 1990s. Following its success in the European market, the implant then became the first LDR device to be introduced in the United States, receiving approval by the US Food and Drug Administration (FDA) in 2004. Despite favorable clinical data demonstrated in multiple large FDA trials, adoption of the technique has stagnated.1 A combination of adverse events and the litigation environment in the US during the early years of Charité negatively impacted the public and surgeon perception of the technology in the US.2 The Charité implant was subsequently taken off of the market in 2012. Debate still exists among experts today whether the decline of that implant was truly related to adverse clinical outcomes stemming from design flaws versus the combination of a hostile medicolegal environment and strategic business decisions made by the manufacturer.3

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Subsequent generation implants with more constrained bearing designs (ProDisc–L, Centinel; activL, Aesculap) were introduced in the United States in 2006 and 2015. Despite the proliferation of many different LDR designs in Europe, ProDisc-L and activL remained the only implants available in the US following the discontinuation of Charité. In 2024, Aesculap suspended US sales of its spine portfolio indefinitely, making ProDisc-L the only commercially available implant in the US at this time.

The limited adoption of LDR is difficult to reconcile with the favorable outcomes demonstrated in studies of long-term follow-up published during the past 5 years.

Wen et al recently published a systematic review of 22 studies involving 2284 patients with an average follow-up of 8.3 years. TDR was found to significantly reduce pain, as evidenced by improvements in the visual analog scale and Oswestry Disability Index (ODI), with mean reductions of 51 and 30 points, respectively. Clinical success and patient satisfaction rates were high, averaging 74.8% and 86.3%, respectively.4 Complications such as implant subsidence, adjacent seg ment degenerat ion, and reoperation were noted, with a mean reoperation rate of 13.6%. No significant differences were observed between midterm (5 years) and long-term (10 years or more) outcomes.

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Follow-up data on LDR patients more than 10 years after surgery were recently published with similarly favorable results.5 This study included 1187 patients who received 1- and 2-level procedures with ProDisc-L with an average follow-up duration of 11 years and 8 months. The authors reported a 50% to 60% reduction in ODI and pain scores with an exceptionally low rate of reoperation (4%).

Subgroup analyses comparing patients with 1-level and 2-level surgery with and without a history of prior discectomy revealed no significant differences in outcomes or reoperation between groups.

The longest reported follow-up data LDR was published in 2022. The study had an average follow-up of 17 years in 16 patients from a Workers’ Compensation cohort.6 Despite the challenges related to the patient population, authors reported a 6.4 point reduction in pain scores at the 17-year follow-up, with 94% of patients reporting they would choose to undergo the surgery again in similar circumstances.

As with any procedure in spine surgery, patient selection plays an important role in the success of LDR. Difficulty in identifying appropriate candidates for the procedure is often cited as an obstacle to widespread adoption.7 It is important to note that the vast majority of prospective studies on LDR had strict inclusion criteria related to patient age, disc height, presence of deformity or spondylolisthesis, and pain distribution. The prototypical candidate for LDR is a young patient with axial low back pain who has imaging findings of isolated 1 or 2-level disc degeneration with preserved disc height and without a history of prior surgery at the level

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Figure 1. Preoperative and postoperative images of a ProDisc-L implant at L5-S1.

of concern. Patients with significant stenosis, spinal deformity, or spondylolisthesis are not typically considered for the procedure because such populations were not studied in FDA trials. Similarly, patients with a history of fusion at an adjacent segment have historically not been considered for LDR. Although LDR is yet to be widely adopted in the US, surgeons who are experienced with the technique continue to explore its applications beyond these traditional indications.

Cuellar et al studied the impact of anterior lumbar interbody fusion (ALIF) at L5-S1 when performed in conjunction with disc replacement at the adjacent levels.8 The authors studied 46 patients receiving an L5-S1 ALIF simultaneously with 1, 2, or 3 LDRs at the adjacent levels. While the study did not have an ALIF-only control arm, the authors described a significant reduction in ODI and pain scores without any differences between groups with 1, 2, or 3 adjacent levels of disc replacement.

The appropriateness of LDR for persistent discogenic pain following microdiscectomy has also been debated due to the potentially destabilizing nature of laminotomy and partial facetectomy. Leahy et al evaluated this topic in a 2008 subgroup analysis of the Prodisc-L investigational device exemption

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trial, comparing outcomes for patients with and without a history prior discectomy.9 Patients in both cohorts improved significantly with regard to pain and disability following surgery. More than 80% of patients stated they would choose to undergo the procedure if faced with a similar circumstance again.

The authors found no significant differences in outcomes between the cohorts and concluded that LDR was a viable treatment for patients with disc degeneration in the setting of prior discectomy.

Historically, patients with severe disc space collapse have not been thought to be appropriate for LDR due to concerns regarding subsidence and/or compromised segmental motion from “overstuffing.” Debate exists around how much preoperative disc height loss is acceptable in patients undergoing the procedure. Yaszay et al studied the impact of pre and postoperative disc height on clinical and radiographic outcomes following LDR.10 While no differences in clinical outcomes were observed based on the degree of disc

height loss, the authors did find greater improvements in segmental range of motion in those with preoperative disc heights less than 9 mm. These findings would suggest that severe disc space collapse should not be considered a contraindication to LDR, more prospective data are needed.

Despite recent publications of favorable long-term clinical data and a track record spanning decades, adoption of LDR among US spine surgeons remains low. The significant body of literature around this technique deserves further attention from all spine surgeons interested in motion preservation, particularly those leading academic training programs. Surgeons experienced with LDR may be able to apply the technique to a wider variety of pathology than previously represented in industry device trials; however, further study in this area is needed. Diagnostic acumen and patient selection continue to be essential for the success of LDR even as our understanding of these topics continues to evolve. l

References 1. Mills ES, Shelby T, Bouz GJ, et al. A decreasing national trend in lumbar disc arthroplasty. Global Spine J. 2023;13:2271–2277.

2. Sandhu FA, Dowlati E, Garica R. Lumbar arthroplasty: past, present, and future. Neurosurgery. 2020;86:155–69.

3. Guyer RD, Shellock J, Blumenthal SL, et al. What happened to patients who received the Charite lumbar artificial disc? [abstract P77]. Spine J. 2022;22:S163.

4. Wen DJ, Tavakoli J, Tipper JL. Lumbar total disc replacements for degenerative disc disease: a systematic review of outcomes with a minimum of 5 years fol-

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low-up. Global Spine J. 2024;14:1827–1837.

5. Marnay TP, Geneste GY, Edgard-Rosa GW, et al. Clinical outcomes after 1 and 2-level lumbar total disc arthroplasty: 1,187 patients with 7 to 21-year follow-up.

J Bone Joint Surg Am. 2024;107:53.

6. Carlson J, Giblin M. Long-term results of Charité lumbar disc replacement: a 17-year follow-up in a workers’ compensation cohort. Int J Spine Surg. 2022;16:831–836.

7. Salzmann SN, Plais N, Shue J, et al. Lumbar disc replacement surgery—successes and obstacles to widespread adoption.

Curr Rev Musculoskelet Med. 2017;10:153.

8. Cuellar JM, Rasouli A, Lanman TH, et al.

Single and multilevel lumbar total disc replacement adjacent to L5-S1 ALIF (lumbar hybrid): 6 years of follow-up.

Int J Spine Surg. 2021;15:971–977.

9. Leahy M, Zigler JE, Ohnmeiss DD, et al. Comparison of results of total disc replacement in postdiscectomy patients versus patients with no previous lumbar surgery. Spine (Phila Pa 1976). 2008;33:1690–1693.

10. Yaszay B, Bendo JA, Goldstein JA, et al. Effect of intervertebral disc height on postoperative motion and outcomes after ProDisc-L lumbar disc replacement.

Spine (Phila Pa 1976). 2008;33:508–512.

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From the Department of Orthopedic Surgery at Midwest Orthopedics at Rush in Chicago, Illinois.

SPINE DEFORMITY

Understanding and Managing Intraoperative Neuromonitoring Changes in Spinal Deformity Surgery Preventing neurologic complications during spinal deformity surgery is a fundamental objective for spine surgeons. Despite ongoing advancements in surgical techniques and technology, the incidence of intraoperative neurologic injury can reach up to 23% in complex deformity cases.1-3 These injuries can have profound consequences, significantly diminishing a patient’s quality of life, increasing the likelihood of secondary health problems, and creating substantial challenges for both the patient and their family. As a result, intraoperative neuromonitoring (IONM) has become a standard practice in spinal deformity surgeries.4 To take full advantage of IONM, surgeons should be aware of the various IONM modalities, learn the correlation between IONM changes and injury patterns, and integrate systematic protocols to address IONM events.

IONM Modalities Somatosensory-Evoked Potentials Somatosensory-evoked potentials (SSEPs) monitor the integrity of the dorsal column of the spinal cord. As such, this modality is useful for monitoring during laminectomies, intradural tumor resections, sublaminar wire insertion, and hook implant insertions. SSEPs

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Nathan J. Lee, MD

measure fine touch and proprioception, but not pain, temperature, or motor function. Therefore, paralysis or significant postoperative motor deficits can occur despite preserved SSEPs.5 Halogenated anesthetic agents, nitrous oxide, hypothermia, and intraoperative hypotension may also affect SSEP readings.6 The warning criteria for SSEPs includes a decrease of more than 50% in amplitude or an increase of more than 10% in latency of signals.

Motor-Evoked Potentials Motor-evoked potentials (MEPs) reflect the function of the anterior column of the spinal cord, specifically the integrity of descending motor pathways along the corticospinal tract and spinothalamic tract. This modality is particularly useful for measuring spinal cord perfusion/ischemia (anterior spinal artery), insult from pedicle screw constructions, traction, and deformity correction. The stimulation site for transcranial MEP (tcMEP) is the cerebral cortex via subdermal electrodes or magnetic tcMEP. Subdermal electrodes can cause scalp edema and occasional unreliable recordings but are preferable given their low impedance and secure positioning in the scalps. Endpoint data are recorded from either the spinal cord (D-wave) or from end muscle compound motor

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action potentials (CMAP). The CMAP is best monitored at sites rich in corticospinal tract innervation, such as distal limb muscles. These commonly include abductor pollicis brevis, adductor hallucis brevis, vastus, and tibialis anterior. The warning criteria for tcMEP includes a decrease of more than 65% to 80% amplitude in the CMAP; however, this threshold currently varies between institutions.6-8 It is important to note that short-acting neuromuscular blockade should be used during intubation.

Therefore, total intravenous anesthesia (TIVA) is preferred for this modality.

Electromyography Electromyography (EMG) applications include both spontaneous EMG (sEMG) recordings and high stimulus triggered EMG (tEMG). In the former, subdermal needles are placed in myotomes that are preselected to coordinate with operative levels. Continuous electrical activity to a myotome may be recorded and provide real-time feedback on possible nerve root irritation. Bursts of activity may indicate possible nerve root impingement, whereas a train of activity is indicative of a more severe root irritation. Complete loss of electrical activity generally correlates with a nerve root being cleanly severed. Muscle relaxants must not be given due to their potential to suppress or dampen all activity. tEMG can provide information on the integrity of a cortical wall along the transpedicular tract through which a screw has been passed.

Bone has a high impedance that requires a high threshold to stimulate an adjacent nerve.

Therefore, if the tEMG requires a higher degree of stimulation, the pedicle cortex is likely

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intact. Lenke et al determined the intensity threshold for safe pedicle screw placement in the lumbar spine with the use of triggered EMG using animal models with clinical correlations.9 Pedicle screws with stimuli intensities larger than 8 milliamperes (mA) were found to be entirely within the pedicle. Those with intensities between 4 and 8 mA demonstrated a potential medial pedicle wall defect. Those with intensities less than 4 mA had a strong likelihood of medial pedicle wall defect and potential contact with neurologic structures. In a retrospective study of 4,857 lumbar pedicle screws, Raynor et al concluded the probability of detecting a medial pedicle breach in the lumbar spine increases with decreasing stimuli thresholds of triggered EMGs.10 In their study, the medial breach rate for screws that required a stimulation greater than 8 mA was 0.31%. For those with thresholds between 4-8 mA, <4 mA, and <2.8 mA, the breach rate was 17.4%, 54.2%, and 100%, respectively. In the thoracic spine, the triggered EMG threshold results vary, but generally thresholds less than 6 mA were indicative of a medial pedicle screw breach. Triggered EMG values lower than these thresholds warrant further tactile and radiographic evaluation.

Stagnara Wake-Up Test The Stagnara wake-up test was the original form of intraoperative spinal cord monitoring and continues to be used as a means of confirming gross neurologic function. It provides a gross assessment of the primary motor cortex and anterior motor pathways, but it does not provide information on sensory pathways or individual nerve roots. In this test, temporary

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reduction of anesthesia is required while assessing upper and lower extremity movement.

If properly administered, the wake-up test can be extremely accurate in detecting gross motor changes and alert the surgeon of the most clinically significant neurologic deficits, including paraparesis, paraplegia, and foot drop. Known risks associated with this test include self-extubation, postoperative recall of the event, loss of intravenous access, and air embolism. The major limitation of this test is that it is entirely reliant on patient compliance and cannot be used in patients who cannot follow commands, such as infants, those with cognitive or developmental disabilities, or those with preexisting extremity weakness.

Another limitation is that it tests the patient’s neurologic status at a single moment in time, and neurologic changes may still occur after the patients are placed back under anesthesia.

The intraoperative wake-up test is also used in patients with unobtainable spinal cord monitoring data and in those in whom the IONM has reached warning criteria without improvement after corrective measures.

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Correlating IONM Changes With Mechanism of Injury Recognizing the pattern of IONM data loss is critical to understanding the type of spinal cord injury and potential mechanism of injury.

Spinal cord injury can be caused by a multitude of factors, which can be categorized into either direct trauma or spinal cord ischemia (Table 1).

Direct Trauma Direct trauma includes misplaced implants, impingement of cord, or iatrogenic insult by an instrument. This may result in either complete cord injury, central cord syndrome, posterior cord syndrome, or Brown Sequard syndrome.

When bilateral MEP and bilateral SSEP meet warning criteria, this suggests that there is a complete cord injury or central cord syndrome.

This typically involves bilateral corticospinal tracts, spinothalamic tracts, and dorsal columns. Bilateral loss in SSEP with preservation of MEPs suggests a posterior cord syndrome.

Unilateral MEP data loss and unilateral SSEP loss typically indicates a Brown Sequard

Table 1. Correlation of Intraoperative Neuromonitoring Changes With Mechanism of Injury.

Motor-Evoked Potentials Injury

Somatosensory-Evoked Potentials

Corticosteroid

Spinothalamic

Dorsal Column

Unilateral

Unilateral

Bilateral

Unilateral

Bilateral

Bilateral

Direct Trauma Complete cord injury

No

Yes

No

Yes

No

Yes

Central cord syndrome

No

Yes

No

Yes

No

Yes

Posterior cord syndrome

No

No

No

No

Yes

Yes

Brown Sequard syndrome

Yes

No

Yes

No

Yes

No

No

Yes

No

Yes

No

No

Perfusion Injury Anterior cord syndrome

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syndrome, which involves the ipsilateral corticospinal tract, ipsilateral dorsal column, and contralateral spinothalamic tract are involved.

This may result from direct trauma such as from a Kerrison rongeur or misplaced pedicle screw. Surgical instrumentation may cause direct insult to the spinal cord, especially in cases where a significant portion of the dura is exposed. Surgeons should always be aware of the exposed neural elements. A “no fly zone,” where no instruments are passed, should be established when a significant amount of dura is exposed to prevent any instrument from falling into the operative field and inadvertently contacting the spinal neural elements. If there is any suspicion that the medial wall of the pedicle is perforated, the pedicle screw should be removed and the screw trajectory should be probed and interrogated, and a consideration for a laminotomy be made. The decision to use different instrumentation, redirect the pedicle screw, or avoid instrumenting at that level are all potential options for rescue.

Spinal Cord Ischemia Data loss in bilateral MEPs with preservation of SSEPs indicates anterior cord syndrome, which involves bilateral corticospinal and spinothalamic tracts. This pattern of injury is typically due to spinal cord ischemia involving the anterior spinal artery. Spinal cord ischemia can occur following manipulation of the spinal column, as such actions may stretch the anterior spinal artery and compromise blood flow, disrupting perfusion to the spinal cord. Spinal cord ischemia may also result from prolonged hypotension, hypoxia due to decreased hemoglobin, or vascular compro-

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mise due to ligation of segmental vessels and prolonged traction.

Timing of IONM Data Loss Determining the “last event” prior to IONM data loss is equally necessary to identify potential mechanisms of injury and for timely targeted interventions. Routine IONM MEP data should be run periodically throughout the surgery, especially prior to, during, and after critical portions of the surgery. For instance, if IONM data are lost prior to decompression laminectomy or osteotomy work, this may suggest positioning, traction, or screw placement issues. If IONM data loss occurs during decompression, there may be cord trauma from decompression or perfusion issues during decompression. If IONM data loss occurs after osteotomy closure, there may be residual bony anatomy requiring further decompression or over-tensioning of the neural elements.

Responding to IONM Data Loss Given the numerous possible etiologies for IONM data loss, having a systematic approach will aid surgeons in determining the causative factors and safely initiate the appropriate treatment in a timely manner. The best practice guidelines for adult and pediatric spinal deformity have been published already.11,12 When IONM data loss occurs, the first step is to confirm with the neuromonitoring and anesthesia teams that the signal changes are “real” and that all technical variables are ruled out. For example, the surgeon should discuss the status of anesthetic agents that may be causing some degree of paralysis. In addition, the electrode leads should be checked

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to confirm that they are in their appropriate positions. The proper position of the patient’s neck and limbs on the operative table should be confirmed as well.

Second, confirm adequate spinal cord perfusion, which may involve elevating mean arterial pressure (>90 mm Hg) and optimizing hematocrit. In a retrospective analysis of more than 12,000 spinal surgeries involving both adults and children, inadequate spinal cord perfusion emerged as the second most frequent cause of intraoperative neuromonitoring alerts.13 This issue accounted for roughly 12% of all alerts, following screw malposition, which was responsible for 30%. In a study by Lee et al, a drop in hematocrit (Hct) of ≥12 points from preoperative to intraoperative levels was a significant risk factor for IONM data loss.14 Interestingly, the volume of transfusion and estimated blood loss did not emerge as key variables. This finding implies that patients with higher preoperative Hct should be evaluated for transfusion if a substantial decline in Hct occurs, even when intraoperative Hct levels remain relatively elevated.

Third, identify the pattern of IONM loss in the context of the actions or events preceding data loss. For example, if there is loss in bilateral MEPs without changes in SSEPs in the setting of a corrective maneuver, then this suggests an anterior cord perfusion-based injury. The corrective maneuver should be released, and spinal cord perfusion should be optimized.

Reassessment of neuromonitoring data should be performed after each intervention. If there is improvement of IONM signals after the release of correction, the surgeon should consider a more moderate correction versus

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in situ fusion with minimal correction after spinal cord perfusion is optimized. If no improvement in IONM is observed, other causes of spinal cord compression or compromise should be contemplated. For instance, osteotomy sites should be inspected before and after corrective maneuvers. The relationship between bony structures and neural elements may change after deformity correction, and areas of the spinal cord, cauda equine, or nerve roots that initially seemed free may now be compressed by overhanging lamina, pedicles, or other neighboring structures. If there is no improvement after these actions, consider other modalities such as descending neurogenic evoked potentials, wake-up test, or potentially a staged procedure.

Implications of IONM Data Improvement IONM not only provides greater clarity for when IONM data loss occurs but also can reassure surgeons that data recovery after an intraoperative intervention indicates a reduced risk for neurologic deficit. In a recent study of 1,106 pediatric and adult spinal deformity patients, Lee et al reported an overall rate of cord-level IONM loss in 4.8% of patients and postoperative neurologic deficit in 1.6% of patients.15 The discrepancy between IONM loss and actual postoperative motor deficits was attributed to the recovery of IONM signals observed in 85% of cases after intraoperative interventions. Notably, all patients with IONM data loss underwent intraoperative corrective measures. Improvement in IONM data, whether partial (improvement out of warning criteria) or complete (baseline values), was significantly associated with a reduced risk

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of postoperative day (POD) 1 motor deficits, with absolute risk reductions of 59% and 89%, respectively. Conversely, patients whose IONM signals did not recover by closure uniformly developed new motor deficits on POD1.

Moreover, by the time of discharge, all but 1 patient (88%) without IONM improvement continued to exhibit motor deficits relative to their preoperative baseline. This highlights the critical role of intraoperative intervention and IONM recovery in mitigating postoperative neurologic complications.

Conclusion Managing IONM loss requires a structured and systematic approach to ensure timely

identification of the underlying causes and appropriate intervention. By collaborating with the neuromonitoring and anesthesia teams to rule out technical factors, optimizing spinal cord perfusion, and carefully reassessing surgical maneuvers and anatomy, surgeons can significantly mitigate the risk of permanent neurologic deficits. The recovery of IONM signals following intraoperative interventions serves as a crucial predictor of favorable postoperative outcomes, emphasizing the value of prompt and effective management. These strategies, supported by established best practice guidelines, underscore the importance of IONM in safeguarding neurological function during complex spinal deformity surgeries. l

References 1. Lenke LG, Fehlings MG, Shaffrey CI, et al.

Neurologic outcomes of complex adult spinal deformity surgery: results of the prospective, multicenter Scoli-RISK-1 study.

Spine (Phila Pa 1976). 2016;41(3):204-12.

2. Fehlings MG, Kato S, Lenke LG, et al.

Incidence and risk factors of postoperative neurologic decline after complex adult spinal deformity surgery: results of the Scoli-RISK-1 study.

Spine J. 2018;18(10):1733-1740.

3. Kato S, Fehlings MG, Lewis SJ, et al. An analysis of the incidence and outcomes of major versus minor neurological decline after complex adult spinal deformity surgery: a subanalysis of Scoli-RISK-1 study.

Spine (Phila Pa 1976). 2018;43(13):905-912.

4. Halsey MF, Myung KS, Ghag A, et al.

Neurophysiological monitoring of spinal cord function during spinal deformity surgery: 2020 SRS neuromonitoring information statement.

Spine Deform. 2020;8(4):591-596.

5. Deletis V, Sala F. Intraoperative neurophysiological monitoring of the spinal cord during spinal cord and spine surgery: a review focus on the corticospinal tracts.

Clin Neurophysiol. 2008;119(2):248-264.

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6. Devlin VJ, Schwartz DM. Intraoperative neurophysiologic monitoring during spinal surgery. J Am Acad Orthop Surg. 2007;15(9):549-560.

in spine deformity surgery: development of an intraoperative checklist to optimize response. Spine Deform. 2014;2(5):333-339.

7. Hilibrand AS, Schwartz DM, Sethuraman V, et al. Comparison of transcranial electric motor and somatosensory evoked potential monitoring during cervical spine surgery. J Bone Joint Surg Am. 2004;86(6):1248-1253.

12. Lenke LG, Fano AN, Iyer RR, et al. Development of consensus-based best practice guidelines for response to intraoperative neuromonitoring events in high-risk spinal deformity surgery.

Spine Deform. 2022;10(4):745-761.

8. Schwartz DM, Auerbach JD, Dormans JP, et al. Neurophysiological detection of impending spinal cord injury during scoliosis surgery. J Bone Joint Surg Am. 2007;89(11):2440-2449.

13. Raynor BL, Bright JD, Lenke LG, et al.

Significant change or loss of intraoperative monitoring data: a 25-year experience in 12,375 spinal surgeries. Spine (Phila Pa 1976). 2013;38(2):E101-E108.

9. Lenke LG, Padberg AM, Russo MH, Bridwell KH, Gelb DE. Triggered electromyographic threshold for accuracy of pedicle screw placement. An animal model and clinical correlation. Spine (Phila Pa 1976). 1995;20(14):1585-1591.

14. Lee NJ, Lenke LG, Arvind V, et al. A novel preoperative scoring system to accurately predict cord-level intraoperative neuromonitoring data loss during spinal deformity surgery: a machine-learning approach [published online November 20, 2024]. J Bone Joint Surg Am. https:// doi.org/10.2106/JBJS.24.00386

10. Raynor BL, Lenke LG, Bridwell KH, Taylor BA, Padberg AM. Correlation between low triggered electromyographic thresholds and lumbar pedicle screw malposition: analysis of 4857 screws. Spine (Phila Pa 1976). 2007;32(24):2673-2678.

11. Vitale MG, Skaggs DL, Pace GI, et al. Best practices in intraoperative neuromonitoring

15. Lee NJ, Lenke LG, Yeary M, et al. Does an improvement in cord-level intraoperative neuromonitoring data lead to a reduced risk for postoperative neurologic deficit in spine deformity surgery?

Spine Deform. 2025;13(1):261-272.

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From the 1Hospital for Special Surgery and 2Weill Cornell Medical College, both in New York, New York.

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Cost-Effectiveness Assessment in Spine Surgery Cost-effectiveness analysis (CEA) is a critical tool in healthcare, offering insights into the value of medical interventions relative to their costs. As healthcare systems worldwide face increasing economic pressures, CEA has become integral in guiding decision-making, resource allocation, and policy development.1 In the field of spine surgery, where procedures often involve substantial costs and complex care pathways, cost-effectiveness assessments are particularly valuable.2 They help determine whether interventions provide meaningful clinical benefits relative to their financial impact, ultimately supporting evidence-based practices.

A cornerstone of CEA is the use of standardized metrics to quantify value. Among these, quality-adjusted life years are widely used to capture the balance between the quality and length of life achieved through an intervention.3 The incremental cost-effectiveness ratio, another key metric, compares the additional cost of an intervention to its incremental benefit, helping to identify treatments that offer the most value. These metrics provide a foundation for comparing diverse treatment options in spine surgery, from traditional approaches to advanced technologies.4,5 To analyze the complexities of cost and outcomes in spine surgery, several analytical frameworks are employed. Markov models and decision trees, for example, are used to simulate patient outcomes and associated costs over time, accounting for uncertain-

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ties and variations in clinical pathways.6 These methodologies enable a nuanced understanding of cost-effectiveness, guiding the selection of interventions that optimize both patient outcomes and economic efficiency in spine surgery practice.

Sereen Halayqeh, MD1

Adrian Lui, MBBS1

Spine Surgery Procedures and Cost Considerations Spine surgery costs vary widely, ranging between $8,286 to $120,394.7,8 These costs are distributed across several major Ruvjee Patel, MBBS1 components, including surgeon compensation, medical devices, implants, hospitalization, facility fees, and operating room expenses. Operating time and hospital length of stay also significantly inf luence costs, especially in Tomoyuki Asada, MD1,2 complex cases requiring extensive preparation and postoperative care.9,10 Complications, including infections or hardware failures, escalate expenses by prolonging surgeries, extending hospital stays, or necessitating revision Sravisht Iyer, MD1,2 procedures. For example, postoperative readmissions due to infections and hardware failures can add $2,817 and $5,354, respectively.9

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Figure 1. Number of clinical-effectiveness studies regarding the lumbar spine indexed in PubMed per year (1992–2019). Reprinted from Eseonu et al, “Systematic Review of Cost-Effectiveness Analyses Comparing Open and Minimally Invasive Lumbar Spinal Surgery,” Int J Spine Surg, 2022;16(4)612-624.37

Spinal fusion, one of the most commonly performed procedures, exemplifies the cost distribution in spine surgery. In lumbar fusion surgeries, medical supplies constitute the largest expense, accounting for 43.8% of total costs. Instrumentation, interbody cages, and biological implants alone contribute up to 37.2% of total costs.7 Service costs, including operating room expenses, represent the second-highest cost driver at 36% to 37.6%.7,11 The surgical approach also impacts costs.

For example, circumferential approaches are generally more expensive than posterior approaches due to longer operative times and additional instrumentation requirements.7 Moreover, anterior cervical discectomy and fusions (ACDFs) follow a similar cost distribution pattern, with medical supplies and facility fees accounting for 39% and 37% of total costs, respectively.12 Among all spine procedures, adult spinal deformity (ASD) surgeries are the most costly, with an average cost of $103,143 for primary ASD procedures.8 This high cost is attributed to the involvement of multiple

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surgical levels, extensive instrumentation, and prolonged operative times. Additionally, ASD surgeries are associated with higher complication and construct failure rates, particularly among elderly and comorbid patients, further increasing total expenses.13 Disc replacement is an increasingly adopted alternative to fusion surgeries.14 For instance, Leibold et al found that cervical disc replacement (CDR) incurred £3,885 in additional costs compared to ACDF, primarily due to implant expenses.15 Although disc replacement procedures typically incur higher up-front costs due to expensive implants, many studies suggest CDR may offer long-term cost benefits by reducing the need for secondary surgeries.16,17 In contrast, decompression surgeries are generally less expensive because they do not require instrumentation or implants.18 Instead, their primary cost drivers include the surgical setting and hospital length of stay. Safaee et al reported total costs for lumbar decompression surgeries ranging from $10,609 to $11,074 for same-day surgeries, compared to $24,507 to $27,929 for inpatient procedures.18

Emerging Technologies Emerging technologies in spine surgery have also influenced cost considerations. Osteobiologics such as bone grafts (autografts and allografts), demineralized bone matrix, and bone morphogenic proteins (BMP) are designed to enhance bone fusion rates. While bone morphogenic proteins show promise in reducing complications such as pseudoarthrosis, its cost-effectiveness remains controversial due to inconsistent findings in the literature.19,20 Similarly, platelet-rich plasma

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has been introduced to promote tissue regeneration and reduce pseudoarthrosis rates, but its cost-effectiveness remains inconclusive due to limited supporting evidence.21 Minimally invasive surgery (MIS) techniques offer another avenue for cost optimization.

Lucio et al demonstrated that MIS reduced costs by 10.4% compared to open techniques in posterior lumbar interbody fusions.22 Uddin et al also highlighted MIS as a cost-effective option in ASD surgery, citing shorter operative times, reduced intraoperative blood loss, and shorter hospital stays.23 However, conflicting data exist; Twitchell et al found MIS could increase overall costs mediated by facility cost and supplies through a value-driven outcomes database.11 These discrepancies underscore the need for further high-quality research to clarify the cost implications of MIS compared to traditional open techniques.

Factors Influencing Cost-Effectiveness Variability in spine surgery costs can arise due to a combination of patient-specific, surgical, and healthcare system factors. Key cost drivers include procedural complexity, the number of spinal levels involved, and the adoption of advanced technologies such as specialized instrumentation and implants.9 The cost-effectiveness of spine surgical procedures and perioperative care is significantly influenced by patient characteristics, which can vary widely even within the same region or healthcare system. Key factors include older age, higher body mass index (BMI), and comorbidities. These elements contribute to increased severity, higher risks of complications, and greater overall costs.24

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Age is a particularly important factor, as it often correlates with increased resource utilization, including longer operating times and extended hospital stays, which drives up costs.24,25 The presence of two or more comorbidities further exacerbates this impact by heightening the risk of complications and adverse outcomes, thereby increasing resource utilization and costs.24,25 Whitmore et al demonstrated that comorbidities are closely associated with advanced age and higher BMI. These factors collectively elevate the risk of complications and are significantly associated with increased direct costs.26 Postoperative wound infections represent another major contributor to healthcare costs because they increase the likelihood of readmission and impose a substantial financial burden.27 Intraoperative neuromonitoring, advanced imaging, and costly innovations such as robotic-assisted technologies introduce additional financial considerations.9,28 Primary surgeries tend to be more cost-effective, as they require less intraoperative time, have fewer complications, and result in shorter hospital stays.29 Conversely, revision surgeries often entail longer care timelines, higher risks of complications, and the need for more extensive procedures, leading to increased costs. The number of fusion levels is a critical determinant of cost. Surgeries involving multiple fusion levels demand greater resources, including extended operating times, additional instrumentation, longer hospital stays, and increased complication risks. Yamamoto et al demonstrated a direct relationship between the number of fusion levels and higher costs.30

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Healthcare system factors, such as regional variations, insurance coverage, and payment models, significantly influence cost-effectiveness in spine surgery. Geographical variations in costs and payment structure can be attributed to varying demands based on local population demographics as well as hospital volumes.31 Lean methodologies, increasingly adopted by large hospital systems, have proven effective in minimizing waste, reducing errors, enhancing staff productivity, and lowering complication rates.32 These practices have shown notable cost-saving potential in spine surgery. Additionally, bundled payment models have emerged as a promising strategy for reducing overall healthcare costs while maintaining or improving care quality. 33

References

Challenges and Future Directions Key challenges in evaluating cost-effectiveness in spine surgery include a lack of standardized costing methodologies, which complicates the development of universal guidelines or recommendations. 35 Many studies fail to clearly define or include indirect costs in their analyses, despite these costs potentially add-

Global Spine J. 2020;10(1):39–46.

1. Jacobs J. HERC: Cost-Effectiveness Analysis. https://www.herc. research.va.gov/include/page.asp?id=cost-effectiveness-analysis 2. Wali AR, Brandel MG, Santiago-Dieppa DR, et al. Markov modeling for the neurosurgeon: a review of the literature and an introduction to cost-effectiveness research.

Neurosurg Focus. 2018;44(5):E20.

3. Sailer AM, van Zwam WH, Wildberger JE, Grutters JP. Cost-effectiveness modelling in diagnostic imaging: a stepwise approach.

Eur Radiol. 2015;25(12):3629–3637.

4. Yagi M, Ames CP, Keefe M, et al. A cost-effectiveness comparisons of adult spinal deformity surgery in the United States and Japan. Eur Spine J. 2018;27(3):678–684.

5. Al-Khouja LT, Baron EM, Johnson JP, Kim TT, Drazin D. Cost-effectiveness analysis in minimally invasive spine surgery.

Neurosurg Focus. 2014;36(6):E4.

6. McAnany SJ, Anwar MA, Qureshi SA. Decision analytic modeling in spinal surgery: a methodologic overview with review of current published literature.

Spine J. 2015;15(10):2254–2270.

7. Beckerman D, Esparza M, Lee SI, et al. Cost analysis of single-level lumbar fusions.

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However, implementing these models in spine surgery is challenging due to the inherent variability in clinical decision-making and cost structures. 33 Outpatient and ambulatory surgical practices for pre-selected patients have further contributed to cost-effectiveness by reducing hospitalization and facility expenses.34

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8. McCarthy IM, Hostin RA, Ames CP, et al.

Total hospital costs of surgical treatment for adult spinal deformity: an extended follow-up study. Spine J. 2014;14(10):2326–2333.

9. Sivaganesan A, Chotai S, Parker SL, McGirt MJ, Devin CJ. Drivers of variability in 90-day cost for elective laminectomy and fusion for lumbar degenerative disease.

Neurosurgery. 2019;84(5):1043–1049.

10. Salas-Vega S, Chakravarthy VB, Winkelman RD, et al. Late-week surgery and discharge to specialty care associated with higher costs and longer lengths of stay after elective lumbar laminectomy. J Neurosurg Spine. 2021;34(6):864–870.

11. Twitchell S, Karsy M, Reese J, et al. Assessment of cost drivers and cost variation for lumbar interbody fusion procedures using the value driven outcomes database. Neurosurg Focus. 2018;44(5):E10.

12. Reese JC, Karsy M, Twitchell S, Bisson EF. Analysis of anterior cervical discectomy and fusion healthcare costs via the value-driven outcomes tool.

Neurosurgery. 2019;84(2):485–490.

13. Williamson TK, Owusu-Sarpong S, Imbo B, et al. An economic analysis of early and late complications after

adult spinal deformity correction. Global Spine J. 2024;14(3):789–795.

14. McAfee PC. The indications for lumbar and cervical disc replacement. Spine J. 2004;4(6 Suppl):177S–181S. 15. Leibold A, Glener S, Sarikonda A, et al.

What is the true cost of motion preservation? A time-driven activity-based cost analysis of anterior cervical discectomy and fusion versus disc replacement.

World Neurosurg. 2024;192:e506–e512.

16. Radcliff K, Guyer RD. Economics of cervical disc replacement. Int J Spine Surg. 2020;14(s2):S67–S72.

17. Radcliff K, Zigler J, Zigler, J. Costs of cervical disc replacement versus anterior cervical discectomy and fusion for treatment of single-level cervical disc disease: an analysis of the Blue Health Intelligence database for acute and long-term costs and complications. Spine. 2015;40(8):521–529.

18. Safaee MM, Chang D, Hillman JM, et al.

Implementation of outpatient minimally invasive lumbar decompression at an academic medical center without ambulatory surgery centers: a cost analysis and systematic review. World Neurosurg. 2021;146:e961–e971.

19. Safaee MM, Dalle Ore CL, Zygourakis CC, Deviren V, Ames CP. Estimating a price

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ing significant value to the results and their generalizability.36 Additionally, the absence of sensitivity analyses that account for the complexity of clinical scenario in many reports limits the robustness of the conclusions.35 Future research should focus on employing standardized health economics-based methodologies and advanced statistical analyses across larger datasets to better understand cost-effectiveness trends in spine surgery.

Defining and incorporating both direct and indirect costs into analyses would enhance consistency and provide more comprehensive insights.

Conclusion Cost-effectiveness in spine surgery is shaped

point for cost-benefit of bone morphogenetic protein in pseudarthrosis prevention for adult spinal deformity surgery. J Neurosurg Spine. 2019;30(6):814–821.

20. Hsu WK, Hashimoto RE, Berven SH, Nassr A. Biological substitutes/extenders for spinal arthrodesis: which agents are cost-effective? Spine. 2014;39(22 Suppl 1):S86–S98.

21. Wang H, Zhu J, Xia Y, Li Y, Fu C. Application of platelet-rich plasma in spinal surgery.

Front Endocrinol. 2023;14:1138255.

22. Lucio JC, Vanconia RB, Deluzio KJ, et al.

Economics of less invasive spinal surgery: an analysis of hospital cost differences between open and minimally invasive instrumented spinal fusion procedures during the perioperative period. Risk Manag Healthc Policy. 2012;5:65–74.

23. Uddin OM, Haque R, Sugrue PA, et al. Cost minimization in treatment of adult degenerative scoliosis. J Neurosurg Spine. 2015;23(6):798–806.

24. Eli I, Whitmore RG, Ghogawala Z. Spine Instrumented Surgery on a Budget-Tools for Lowering Cost Without Changing Outcome.

Global Spine J. 2021;11(1 suppl):45S–55S. https://doi.org/10.1177/21925682211004895 25. Butrico C, Meisel HJ, Sage K. Patient comorbidities, their influence on lumbar

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by patient-specific, surgical, and healthcare system factors. Key drivers include age, comorbidities, procedural complexity, and technological advancements, with revision surgeries and multiple fusion levels significantly increasing costs. Emerging practices such as lean methodologies, outpatient surgeries, and bundled payments show promise in reducing expenses but face challenges due to variability in clinical decision-making. Standardizing costing met hodolog ies, incor porat ing indirect costs, and using larger datasets in future research are essential to develop consistent guidelines and enhance cost-effectiveness while maintaining high-quality care and outcomes. l

spinal fusion surgery, and recommendations to reduce unfavorable outcomes. J Am Acad Orthop Surg. 2024;32(24):1115–1121.

26. Whitmore RG, Stephen JH, Vernick C, et al. ASA grade and Charlson Comorbidity Index of spinal surgery patients: correlation with complications and societal costs. Spine J. 2014;14(1):31–38.

27. Rosenthal NA, Heinrich KH, Chung J, Yu H. Cost and hospital resource utilization of Staphylococcus aureus infection post elective posterior instrumented spinal fusion surgeries in U.S. hospitals: a retrospective cohort study. Spine. 2019;44(9):637–646.

28. Philipp LR, Leibold A, Mahtabfar A, et al. Achieving value in spine surgery: 10 major cost contributors. Global Spine J. 2021;11(1_suppl):14S–22S. https:// doi.org/10.1177/2192568220971288 29. Padula WV, Smith GA, Gordon Z, Pronovost PJ. Value defects in spine surgery: how to reduce wasteful care and improve value. J Am Acad Orthop Surg. 2024;32(18):833–839.

30. Yamamoto T, Yagi M, Suzuki S, et al.

Limited cost benefit of lateral interbody fusion for adult spinal deformity surgery. Spine. 2021;46(1):48–53.

31. Reyes SG, Bajaj PM, Alvandi BA, et al. Impact of social determinants of

health in spine surgery. Curr Rev Musculoskelet Med. 2023;16(1):24–32.

32. Sethi R, Yanamadala V, Burton DC, Bess RS. Using lean process improvement to enhance safety and value in orthopaedic surgery: the case of spine surgery. J Am Acad Orthopaedic Surg. 2017;25(11):e244–e250.

33. Hines K, Mouchtouris N, Getz C, et al.

Bundled payment models in spine surgery.

Global Spine J. 2021;11(1 suppl):7S–13S. 34. Purger DA, Pendharkar AV, Ho AL, et al.

Outpatient vs inpatient anterior cervical discectomy and fusion: a population-level analysis of outcomes and cost.

Neurosurgery. 2018;82(4):454–464.

35. Chang D, Zygourakis CC, Wadhwa H, Kahn JG. Systematic review of cost-effectiveness analyses in U.S. spine surgery.

World Neurosurg. 2020;142:e32–e57.

36. Alvin MD, Miller JA, Lubelski D, et al.

Variations in cost calculations in spine surgery cost-effectiveness research.

Neurosurg Foc. 2014;36(6):E1.

37. Eseonu K, Oduoza U, Monem M, Tahir M. Systematic review of cost-effectiveness analyses comparing open and minimally invasive lumbar spinal surgery.

Int J Spine Surg. 2022;16(4):612–624. https://doi.org/10.14444/8297

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