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Computer-assisted neuronavigation (CAN) during spine fusions has increasingly been utilized in the United States. The aim of this study was to analyze the trends, health care utilization, and clinical outcomes associated with CAN use.The MarketScan database was queried using the ICD-9/10 and CPT 4th edition, from 2003 to 2019. We included patients aged ≥18 years with at least 2 years of follow-up. Outcomes were repeat/new fusions, length of stay (LOS), discharge disposition, hospital re-admissions, outpatient services, and medication refills for up to 24 months.Of 183,620 patients who underwent spine fusions, 5046 (2.75%) were identified to have CAN utilized. CAN is increasingly being utilized for spine fusions since 2010, reaching 10.76% of all fusions in 2017, compared to 0.38% in 2010. CAN had no impact on LOS, home discharge, or complications at index hospitalization and 30-days post discharge. CAN was associated with lower rates of repeat fusions at 6 months (1% vs. 2%) and 24 months (5% vs. 6%), P0.05. Patients who underwent CAN had lower payments at 6 months ($5186 vs. $5527, P = 0.0159), 12 months ($10,267 v.s $11,262, P = 0.0207), and 24 months ($21,453 vs. $24,355, P = 0.0021).CAN is increasing being used for spine fusions primarily for thoracolumbar procedures. No difference in complications, discharge disposition, and LOS were noted across the cohorts at index hospitalization, with higher index payments with CAN use. CAN was associated with lower rates of repeat fusions and corresponding health care utilization for up to 24 months.

Amyotrophic lateral sclerosis (ALS) involves progressive motor neuron loss, leading to paralysis and death typically within 3–5 years of diagnosis. Dysfunctional astrocytes may contribute to disease and glial cell line-derived neurotrophic factor (GDNF) can be protective. Here we show that human neural progenitor cells transduced with GDNF (CNS10-NPC-GDNF) differentiated to astrocytes protected spinal motor neurons and were safe in animal models. CNS10-NPC-GDNF were transplanted unilaterally into the lumbar spinal cord of 18 ALS participants in a phase 1/2a study (NCT02943850). The primary endpoint of safety at 1 year was met, with no negative effect of the transplant on motor function in the treated leg compared with the untreated leg. Tissue analysis of 13 participants who died of disease progression showed graft survival and GDNF production. Benign neuromas near delivery sites were common incidental findings at post-mortem. This study shows that one administration of engineered neural progenitors can provide new support cells and GDNF delivery to the ALS patient spinal cord for up to 42 months post-transplantation.

OBJECTIVE In degenerative cervical myelopathy (DCM) pathologies in which there exists a clinical equipoise in approach selection, a randomized controlled trial found that an anterior approach did not significantly improve patient-reported outcomes compared with posterior approaches. In this era of value and bundled payment initiatives, the cost profiles of various surgical approaches will form an important consideration in decision-making. The objective of this study was to compare 90-day and 2-year reimbursements for ≥ 2-level (multilevel) anterior cervical discectomy and fusion (mACDF), anterior cervical corpectomy and fusion (ACCF), posterior cervical laminectomy and fusion (LF), and cervical laminoplasty (LP) performed for DCM. METHODS The IBM MarketScan research database (2005–2018) was used to study beneficiaries 30–75 years old who underwent surgery using four approaches (mACDF, ACCF, LF, or LP) for DCM. Demographics, index surgery length of stay (LOS), complications, and discharge disposition were compared. Index admission (surgeon, hospital services, operating room) and postdischarge inpatient (readmission, revision surgery, inpatient rehabilitation), outpatient (imaging, emergency department, office visits, physical therapy), and medication-related payments were described. Ninety-day and 2-year bundled payment amounts were simulated for each procedure. All payments are reported as medians and interquartile ranges (IQRs; Q1–Q3) and were adjusted to 2018 US dollars. RESULTS A total of 10,834 patients, with a median age of 54 years, were included. The median 90-day payment was $46,094 (IQR $34,243–$65,841) for all procedures, with LF being the highest ($64,542) and LP the lowest ($37,867). Index hospital payment was 62.4% (surgery/operating room 46.6%) and surgeon payments were 17.5% of the average 90-day bundle. There were significant differences in the index, 90-day, and 2-year reimbursements and their distribution among procedures. CONCLUSIONS In a national cohort of patients undergoing surgery for DCM, LP had the lowest complication rate and simulated bundled reimbursements at 90 days and 2 years postoperatively. The lowest quartile 90-day payment for LF was more expensive than median amounts for mACDF, ACCF, and LP. If surgeons encounter scenarios of clinical equipoise in practice, LP is likely to result in maximum value because it is 70% less expensive on average than LF over 90 days.

Background Anterior cervical diskectomy and fusion (ACDF) is a procedure for effectively relieving radiculopathy. Opioids are commonly overprescribed in postsurgical settings and prescriptions vary widely among providers. We identify trends in opioid dependence before and after ACDF. Methods We used the Truven Health MarketScan data to identify adult patients undergoing ACDF for degenerative cervical spine conditions between 2009 and 2015. Patients were segregated in four cohorts of preoperative and postoperative opioid nondependence (ND) or dependence (D) with 15 months of postoperative follow-up. Results A total of 25,403 patients with median age of 52 years (18–92) who underwent ACDF met the inclusion criteria. Breakdown of the four cohorts was as follows: prior nondependent who remain nondependent (NDND): 62.76% (n = 15,944); prior nondependent who become dependent (NDD): 4.6% (n = 1,168); prior dependent who become nondependent (DND): 14.03% (n = 3,564); and prior dependent who remain dependent (DD): 18.61% (n = 4,727). Opioid dependence decreased 9.43% postoperatively. Overall payments and 30-day readmissions increased 1.96 and 1.79 times for opioid dependent versus nondependent cohorts, respectively. Adjusted payments at 3 to 15 months were significantly increased for dependent cohorts with 3.56-fold increase for the DD cohort when compared with the NDND cohort. Length of stay, complications, medication refills, outpatient measures, and hospital admissions were also higher in those groups with postoperative opioid dependence when compared with those who were not opioid dependent. Conclusions Opioid dependence after ACDF is associated with increased hospital readmissions, complication rates at 30 days, and payments within 3 months and 3 to 15 months postdischarge. Overall opioid dependence was decreased after ACDF procedure, however, a smaller number of opioid-dependent and opioid-naive patients became dependent postoperatively and should be followed carefully.

Retrospective cohort study.The aim was to compare 90-day and 2-year reimbursements for ≥2-level anterior cervical discectomy and fusion (mACDF), anterior cervical corpectomy and fusion (ACCF), posterior laminectomy and fusion (LF) and laminoplasty (LP) done for degenerative cervical myelopathy (DCM).In DCM pathologies where there exists a clinical equipoise in approach selection, a randomized controlled trial found that an anterior approach did not significantly improve patient-reported outcomes over posterior approaches. In the era of value and bundled payments initiatives, cost profile of various approaches will form an important consideration for decision making.IBM MarketScan Research Database (2005-2018) was used to study beneficiaries (30-75 y) who underwent surgery (mACDF, ACCF, LF, LP) for DCM. Index hospital stay (operating room, surgeon, hospital services) and postdischarge inpatient, outpatient and prescription medication payments have been used to simulate 90-day and 2-year bundled payment amounts, along with their distribution for each procedure.A total of 10,834 patients with median age of 54 years were included. The median 90-day payment was $46,094 (interquartile range: $34,243-$65,841) for all procedures, with LF being the highest ($64,542) and LP the lowest ($37,867). Index hospital was 62.4% (operating room: 46.6) and surgeon payments were 17.5% of the average 90-day bundle. There was significant difference in the index, 90-day and 2-year reimbursements and their distribution among procedures.In a national cohort of patients undergoing surgery for DCM, LP had the lowest complication rate, and simulated bundled reimbursements at 90 days and 2 years postoperatively. The lowest quartile 90-day payment for LF was more expensive than median amounts for mACDF, ACCF, and LP. If surgeons encounter scenarios of clinical equipoise in practice, LP is likely to result in maximum value as it is on an average 70% less expensive than LF over 90 days.

There is a wide variety of commercially available products on the market. This chapter categorizes the “toolkit” of specialized products commonly used for neurointerventional procedures. Understanding the basic differences in the uses and actions of these products is intended to assist providers in evaluating and choosing the appropriate agent or device.

To identify factors impacting long-term complications, reoperations, readmission rates, and health care utilization in patients with osteoporosis (OP) following lumbar fusions.We used International Classification of Disease, Ninth Revision, International Classification of Disease, Tenth Revision , and Current Procedural Terminology codes to extract data from MarketScan (2000-2016). Patients undergoing lumbar spine fusion were divided into 2 groups based on preoperative diagnosis: OP or non-OP. We used multivariable generalized linear regression models to analyze outcomes of interest (reoperation rates, readmissions, complications, health care utilization) at 1, 6, 12, and 24 months after discharge.MarketScan identified 116,749 patients who underwent lumbar fusion with ≥24 months of follow-up; 6% had OP. OP patients had a higher incidence of complications (14% vs. 9%); were less likely to be discharged home (77% vs. 86%, P0.05); had more new fusions or refusions at 6 months (2.9% vs. 2.1%), 12 months (5% vs. 3.8%), and 24 months (8.5% vs. 7.4%); incurred more outpatient services at 12 months (80 vs. 61) and 24 months (148 vs. 115); and incurred higher overall costs at 12 months ($22,932 vs. $17,017) and 24 months ($48,379 vs. $35,888). Elderly OP patients (65 years old) who underwent multilevel lumbar fusions had longer hospitalization, had higher complication rates, and incurred lower costs at 6, 12, and 24 months compared with young non-OP patients who underwent single-level lumbar fusion.Patients of all ages with OP had higher complication rates and required revision surgeries at 6, 12, and 24 months compared with non-OP patients. Elderly OP patients having multilevel lumbar fusions were twice as likely to have complications and lower health care utilization compared with younger non-OP patients who underwent single-level fusion.

Background Enhanced recovery after surgery (ERAS) represents an evidence-based multidisciplinary approach to perioperative management after major surgery that decreases complications and readmissions and improves functional recovery. Spine surgery is a traditionally invasive intervention with an extended recovery phase and may benefit from ERAS protocol integration. Methods We analyzed the use of ERAS in spine surgery by completing a search using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and the PICOS (Participants, Intervention, Comparison, Outcomes, Study Design) model through PubMed and Ovid databases to identify studies that fit our search criteria. We assess the outcomes and ERAS elements selected across protocols as well as the study design and internal validation methods. Results A total of 19 studies met the inclusion criteria and were used in our analysis. Patient populations differed significantly across all 4 studies. Reduction in length of stay was reported in 7 studies using the ERAS protocol. Comparative studies between ERAS and non-ERAS show improved pain scores and reduced opioid consumption postoperatively, but no differences in complications or readmissions between groups. Complication rates under ERAS protocols ranged from 2.0% to 31.7%. Significant pain reduction in visual analog scale scores was observed with 3 ERAS protocols. Direct, indirect, and total cost decreases were also observed with implementation of ERAS protocols. Conclusions A limited cohort of studies with significant variability in patient population and ERAS protocol implementation have evaluated the integration of ERAS within spine surgery. ERAS in spine surgery may provide reductions in complications, readmissions, length of stay, and opioid use, in combination with improvements in patient-reported outcomes and functional recovery.

Applications of machine learning (ML) in translational medicine include therapeutic drug creation, diagnostic development, surgical planning, outcome prediction, and intraoperative assistance. Opportunities in the neurosciences are rich given advancement in our understanding of the brain, expanding indications for intervention, and diagnostic challenges often characterized by multiple clinical and environmental factors. We present a review of ML in neuro-oncology, epilepsy, Alzheimer's disease, and schizophrenia to highlight recent progression in these field, optimizing machine learning capabilities in their current forms. Supervised learning models appear to be the most commonly incorporated algorithm models for machine learning across the reviewed neuroscience disciplines with primary aim of diagnosis. Accuracy ranges are high from 63% to 99% across all algorithms investigated. Machine learning contributions to neurosurgery, neurology, psychiatry, and the clinical and basic science neurosciences may enhance current medical best practices while also broadening our understanding of dynamic neural networks and the brain.

Applications of machine learning (ML) in translational medicine include therapeutic drug creation, diagnostic development, surgical planning, outcome prediction, and intraoperative assistance. Opportunities in the neurosciences are rich given advancement in our understanding of the brain, expanding indications for intervention, and diagnostic challenges often characterized by multiple clinical and environmental factors. We present a review of ML in neuro-oncology, epilepsy, Alzheimer's disease, and schizophrenia to highlight recent progression in these field, optimizing machine learning capabilities in their current forms. Supervised learning models appear to be the most commonly incorporated algorithm models for machine learning across the reviewed neuroscience disciplines with primary aim of diagnosis. Accuracy ranges are high from 63% to 99% across all algorithms investigated. Machine learning contributions to neurosurgery, neurology, psychiatry, and the clinical and basic science neurosciences may enhance current medical best practices while also broadening our understanding of dynamic neural networks and the brain.

Introduction Augmented reality (AR) is an advanced technology and emerging field that has been adopted into spine surgery to enhance care and outcomes. AR superimposes a three-dimensional computer-generated image over the normal anatomy of interest in order to facilitate visualization of deep structures without the ability to directly see them. Objective To summarize the latest literature and highlight AR from the annual “Spinal Navigation, Emerging Technologies and Systems Integration” meeting lectures presented by the Seattle Science Foundation (SSF) on the development and use of augmented reality in spinal surgery. Methods We performed a comprehensive literature review from 2016 to 2020 on PubMed to correlate with lectures given at the annual “Emerging Technologies” conferences. After the exclusion of papers that concerned non-spine surgery specialties, a total of 54 papers concerning AR in spinal applications were found. The articles were then categorized by content and focus. Results The 54 papers were divided into six major focused topics: training, proof of concept, feasibility and usability, clinical evaluation, state of technology, and nonsurgical applications. The greatest number of papers were published during 2020. Each paper discussed varied topics such as patient rehabilitation, proof of concept, workflow, applications in neurological and orthopedic spine surgery, and outcomes data. Conclusions The recent literature and SSF lectures on AR provide a solid base and demonstrate the emergence of an advanced technology that offers a platform for an advantageous technique that is superior, in that it allows the operating surgeon to focus directly on the patient rather than a guidance screen.

Machine learning has been applied to improve diagnosis and prognostication of acute traumatic spinal cord injury. We investigate potential for clinical integration of machine learning in this patient population to navigate variability in injury and recovery.We performed a systematic review using PRISMA guidelines through PubMed database to identify studies that use machine learning algorithms for clinical application toward improvements in diagnosis, management, and predictive modeling.Of the 132 records identified, a total of 13 articles met inclusion criteria and were included in final analysis. Of the 13 articles, 5 focused on diagnostic accuracy and 8 were related to prognostication or management of traumatic spinal cord injury. Across studies, 1983 patients with spinal cord injury were evaluated with most classifying as ASIA C or D. Retrospective designs were used in 10 of 13 studies and 3 were prospective. Studies focused on MRI evaluation and segmentation for diagnostic accuracy and prognostication, investigation of mean arterial pressure in acute care and intraoperative settings, prediction of ambulatory and functional ability, chronic complication prevention, and psychological quality of life assessments. Decision tree, random forests (RF), support vector machines (SVM), hierarchical cluster tree analysis (HCTA), artificial neural networks (ANN), convolutional neural networks (CNN) machine learning subtypes were used.Machine learning represents a platform technology with clinical application in traumatic spinal cord injury diagnosis, prognostication, management, rehabilitation, and risk prevention of chronic complications and mental illness. SVM models showed improved accuracy when compared to other ML subtypes surveyed. Inherent variability across patients with SCI offers unique opportunity for ML and personalized medicine to drive desired outcomes and assess risks in this patient population.

Anxiety and depression are associated with suboptimal outcomes, higher complications, and cost of care after elective spine surgery. The effect of combined anxiety-depression and preoperative antidepressant treatment in spinal fusion patients is not known.To study the burden of combined anxiety-depression and its impact on healthcare utilization and costs in patients undergoing spinal fusion and to study the prevalence and impact of antidepressant treatment preoperatively.This is a retrospective cohort study from the IBM MarketScan Research Database (2000-2018). Patients were studied in 7 different "phenotypes" of anxiety and depression based on combination of diagnoses and treatment. Outcome measures included healthcare utilization and costs from 1 year preoperatively to 2 years postoperatively. Bivariate and multivariable analyses have been reported.We studied 75 087 patients with a median age of 57 years. Patients with combined anxiety-depression were associated with higher preoperative and postoperative healthcare utilization and costs, as compared with anxiety or depression alone. The presence of depression in patients with and without anxiety disorder was a risk factor for postoperative opioid use and 2-year reoperation rates, as compared with anxiety alone. Patients with anxiety and/or depression on antidepressants are associated with significantly higher healthcare costs and opioid use. The adjusted 2-year reoperation rate was not significantly different between treated and untreated cohorts.Spine surgeons should use appropriate measures/questionnaires to screen depressed patients for anxiety and vice versa because the presence of both adds significant risk of higher healthcare utilization and costs over patients with 1 diagnosis, especially anxiety alone.

The aim of this retrospective cohort study was to study the impact of age on in-hospital complications and mortality following surgery for Ankylosing Spondylitis (AS) associated spine fractures.We extracted data from the Nationwide Inpatient Sample (NIS) database (1998-2018) using ICD-9/10 codes. Patients with a primary diagnosis of AS associated spine fractures who underwent fusion surgery were included. Complications and in-hospital mortality were analyzed.A total cohort of 8526 patients was identified. Overall, the median age of the cohort was 69 years. AS associated fractures were equally distributed among cervical and thoracolumbar regions. Overall, complications were noted in 48% of patients and pulmonary complications were the most common (32%) followed by renal (13%) and infection (12%). Complications were seen in 57.3% of patients ≥ 70 years of age compared to 38.4% of patients 70 years of age (p .0001). Also, 9.9 % of patients ≥ 70 years of age had in-hospital mortality compared to 3.1 % of patients 70 years of age (p .0001). Based on surgical approaches, elderly patients (≥70 years) who underwent anterior, posterior, and anterior + posterior approaches had 19.8%, 7.4% and 16.4% in-hospital mortality compared to 5.3%, 2.2% and 7.4% respectively for patients 70 years.Elderly patients (≥70 years of age) were 3.2 times more likely to have in-hospital mortality and higher complications compared to younger patients (57% vs. 38%). Cervical compared to thoracolumbar fractures and anterior compared to posterior surgical approaches were associated with higher complications and in-hospital mortality.

OBJECTIVE Ankylosing spondylitis (AS) is a chronic inflammatory disease affecting the sacroiliac joints and axial spine that is closely linked with human leukocyte antigen–B27. There appears to be an increased frequency of associated epidural hematomas in spine fractures in patients with AS. The objective was to review the incidence within the literature and a single-institution experience of the occurrence of epidural hematoma in the context of patients with AS requiring spine surgery. METHODS Deep 6 AI software was used to search the entire database of patients at a single level I trauma center (since the advent of the institution’s modern electronic health record system) to look at all patients with AS who underwent spinal surgery and who had a diagnosis of epidural hematoma. Additionally, a systemic literature review was performed of all papers evaluating the incidence of epidural hematoma in patients with spine fractures. RESULTS A single-institution, retrospective review of records from 2009 to 2020 yielded a total of 164 patients with AS who underwent spine surgery. Of those patients, 17 (10.4%) had epidural hematomas on imaging, with the majority requiring surgical decompression. These spine fractures occurred close to the cervicothoracic or thoracolumbar junction. The patients ranged in age from 51 to 88 years, and there were 14 males and 3 females in the cohort. Eight patients were administered an antiplatelet and/or anticoagulant agent, and the rest were not. All patients required surgical stabilization, with 64.7% of patients also requiring decompressive laminectomies for evacuation of the hematoma and spinal cord decompression. Only 1 death was reported in the series. There was a tendency toward neurological improvement after surgical intervention. CONCLUSIONS AS has been a well-described pathologic process that leads to an increased risk of three-column injury in spine fracture, with an increased incidence of symptomatic epidural hematoma compared with patients without AS. Early recognition of this entity is important to ensure that appropriate surgical management includes addressing compression of the neural elements in addition to surgical stabilization.

Background With the recent advances in technology and healthcare, increasing numbers of individuals over the age of 80 will require surgical intervention for spinal pathology. Given the risk of increased complications in the elderly, a limited number of spinal surgeries are performed on octogenarians every year. This makes it difficult to generalize the trends and outcomes of these surgeries to a greater population. This study attempts to understand the trends in the safety profile and healthcare utilization across the United States for octogenarians undergoing spinal fusion and/or decompression surgery for spinal stenosis and/or degenerative disease using the PearlDiver database. Methodology Patients who underwent fusion and/or decompression for stenosis and/or degenerative diseases were extracted using International Classification of Disease ninth and tenth revisions (ICD-9 prior to October 2015, ICD-10 after) from 2007 to 2016 in the PearlDiver database. Three comparative groups were considered: (1) primary fusion without concurrent decompression, (2) primary decompression with concurrent fusion, and (3) fusion with concurrent decompression. Outcomes of interest were patient characteristics, demographics, length of stay, surgery hospitalization payments, and discharge disposition. These outcomes were compared to patients over the age of 20 who also underwent spinal surgery. Results A total of 9,715 patients who underwent spinal surgery were identified in the search. Of the 9,139 patients, 503 were octogenarians and 73 were nonagenarians. Octogenarians and nonagenarians diagnosed with spinal stenosis were more likely to undergo decompression alone rather than fusion or both fusion and decompression (21 for both fusion and decompression; p < 0.0001). Patients diagnosed with both spinal stenosis and degeneration were more likely to undergo both fusion and decompression than fusion or decompression alone (239 for both, 208 for decompression alone, and 23 for fusion alone; p < 0.0001). No statistically significant difference was found in the percentage of patients discharged home following either fusion or decompression or both surgeries (p = 0.0737). The mean length of stay for patients in the 20-79-year age group was 2.79 days, whereas for the octogenarian and nonagenarian cohort it was 3.85 days. The index hospitalization pay for patients in the 20-79-year age group was $19,220, whereas for the octogenarians and nonagenarians cohort it was $15,091. Conclusions Patients over the age of 80 were more likely to undergo either a fusion procedure or a decompression procedure alone rather than both unless they were diagnosed with spinal degeneration. The PearlDiver database analysis indicates that the length of stay for octogenarians and nonagenarians is longer than that for patients in the 20-79-year age group, and that younger patients are more likely to be discharged earlier than patients over the age of 80. Moreover, we observed that the index hospitalization pay was higher for patients over the age of 20 than for octogenarians and nonagenarians in all cases except for a fusion procedure.

Background Surgical site infection (SSI) may lead to vertebral osteomyelitis, diskitis, paraspinal musculoskeletal infection, and abscess, and remains a significant concern in postoperative management of spinal surgery. SSI is associated with greater postoperative morbidity and increased health care payments. Methods We conducted a retrospective analysis using MarketScan to identify health care utilization payments and risk factors associated with SSI that occurs postoperatively. Known patient- or procedure-related risk factors were searched across those receiving spine surgery who developed postoperative infection. Results A total of 33,061 patients who developed infection after spinal surgery were identified in Marketscan. Overall payments at 6 months, including index hospitalization for those with infection, were $53,573 and $46,985 for the cohort with no infection. At 24 months, the infection group had overall payments of $83,280 and $66,221 for no infection. Risk factors with largest effect size most likely to contribute to infection versus no infection were depression (4.6%), diabetes (3.7), anemia (3.3%), two or more levels (2.8%), tobacco use (2.2%), trauma (2.1%), neoplasm (1.8%), congestive heart failure (1.3%), instrumentation (1.1%), renal failure (0.9%), intravenous drug use (0.8%), and malnutrition (0.5%). Conclusions SSIs were associated with significant health care utilization payments at 24 months of follow-up. The following clinical and procedural risk factors appear to be predictive of postoperative SSI: depression, diabetes, anemia, two or more levels, tobacco use, trauma, neoplasm, congestive heart failure, instrumentation, renal failure, intravenous drug use, and malnutrition. Interpretation of modifiable and nonmodifiable risk factors for infection informs surgeons of expected postoperative course and preoperative risk for this most common and deleterious postoperative complication to spinal surgery.

OBJECTIVEPosterior reduction with pedicle screws is often used for stabilization of unstable spondylolisthesis to directly reduce misalignment or protect against micromotion while fusion of the affected level occurs. Optimal treatment of spondylolisthesis combines consistent reduction with a reduced risk of construct failure. The authors compared the reduction achieved with a novel anterior integrated spacer with a built-in reduction mechanism (ISR) to the reduction achieved with pedicle screws alone, or in combination with an anterior lumbar interbody fusion (ALIF) spacer, in a cadaveric grade I spondylolisthesis model.METHODSGrade I slip was modeled in 6 cadaveric L5–S1 segments by creation of a partial nucleotomy and facetectomy and application of dynamic cyclic loading. Following the creation of spondylolisthesis, reduction was performed under increasing axial loads, simulating muscle trunk forces between 50 and 157.5 lbs, in the following order: bilateral pedicle screws (BPS), BPS with an anterior spacer (BPS+S), and ISR. Percent reduction and reduction failure load—the axial load at which successful reduction (≥ 50% correction) was not achieved—were recorded along with the failure mechanism. Corrections were evaluated using lateral fluoroscopic images.RESULTSThe average loads at which BPS and BPS+S failed were 92.5 ± 6.1 and 94.2 ± 13.9 lbs, respectively. The ISR construct failed at a statistically higher load of 140.0 ± 27.1 lbs. Reduction at the largest axial load (157.5 lbs) by the ISR device was tested in 67% (4 of 6) of the specimens, was successful in 33% (2 of 6), and achieved 68.3 ± 37.4% of the available reduction. For the BPS and BPS+S constructs, the largest axial load was 105.0 lbs, with average reductions of 21.3 ± 0.0% (1 of 6) and 32.4 ± 5.7% (3 of 6) respectively.CONCLUSIONSWhile both posterior and anterior reduction devices maintained reduction under gravimetric loading, the reduction capacity of the novel anterior ISR device was more effective at greater loads than traditional pedicle screw techniques. Full correction was achieved with pedicle screws, with or without ALIF, but under significantly lower axial loads. The anterior ISR may prove useful when higher reduction forces are required; however, additional clinical studies will be needed to evaluate the effectiveness of anterior devices with built-in reduction mechanisms.

Study design Survey analysis among spine surgeons. Objective To identify current consensus and discrepancies in managing adverse intraoperative events among spine surgeons. Summary of background data Major intraoperative events are not commonly the subject of formal medical training, in part due to the relative paucity of their occurrence and in part due to an insufficient evidence base. Given the clinical impact of appropriate complication management, it is important to identify where surgeons may be able to improve decision making when choosing interventions. Methods A survey was created including five hypothetical unpredicted scenarios affecting different organ systems to assess the respondents' preferred reactions. The five clinical vignettes that were selected by the researchers involved: 1) loss of spinal signals in neuro-monitoring, 2) prone position cardiac arrest, 3) prone position hypoxia during thoracic corpectomy and instrumentation, 4) supine cervical vertebral artery injury, and 5) sudden onset hypotension in major prone position reconstructive spine surgery. Twenty-eight surveys (Spine Fellows n = 11; Spine surgeon Faculty n = 17) were completed and returned to the investigators. Results were sorted and ranked according to the frequency each action was identified as a top five choice. Results Following formal statistical evaluation loss of signals in neuro-monitoring had the statistically significantly most uniform response while the scenario involving cardiac compromise had the most heterogeneous. Many "best" responses had near or complete consensus while some "distractor" possibilities that could harm a patient were also selected by the respondents. Conclusion The heterogeneity of responses in the face of "disaster scenario" intraoperative events shows there is room for more thorough and directed education of spine surgeons during training. As surgical teaching moves toward increased use of patient simulation and situational learning, these vignettes hopefully serve to provide direction for training future spine surgeons on how best to approach difficult situations. Level of evidence 4.

Objective Lumbar spinal stenosis (LSS) in octogenarians and beyond has a significant impact on quality of life requiring surgical decompression and hence impact on health care utilization. Risk of surgical failure and impact on health care resources is always a concern in this patient population (more so in nonagenarians). The aim of our study was to compare clinical outcomes and healthcare utilization in patients (80–89 vs.90+) undergoing decompression for LSS. Patients and methods Data was extracted using ICD9/10 and CPT codes from MarketScan (2001–2015) in this retrospective study. We defined the comparative groups based on the age groups (80–89 and 90+), in patients with LSS. Outcomes of interest were: length of hospital stay, discharge disposition and utilization in the index hospitalization, 6- months, 12 months following index procedure as well as the associated health care utilization. Patient characteristics and outcomes among cohorts were compared using univariate tests. Outcomes were further compared using adjusted multivariable regression models. Statistical analysis was performed with SAS 9.4. Results A cohort of 5387 was identified from the database, 96.38% were in the 80–89 age group and 3.62%were in the 90+ age group. The proportion of patients undergoing surgery for LSS among 80–89 (95.7–98.5%) and 90+ age group (1.5–4.3%) remained constant through the years. Interestingly, 13.83% and 16.92% of patients had Elixhauser comorbidity index of 3+ in 80–89 age group and 90+ age groups respectively. Decompression with fusion was performed in 19.4% of patients in 80–89 age group, compared to 9.74% of patients in 90+ age group. There was no difference in median length of hospital stay (3 days, p = 0.19) and complications across the cohorts (80–89: 16.7%; 90+: 18.46% p = 0.51). 70.6% of patients in 80–89 age groups were discharged to home compared to 60.5% in 90+ age group (p = 0.0023). At 6 months follow-up, overall rate of new decompression, new fusion, re-fusion at index level were 2.38%, 0.59% and 0.33% only, with no differences across the cohorts. Interestingly, patients in 80–89 age group incurred higher outpatient services, number of medication refills and related payments at 6-months and 12-months follow-up, compared to patients in 90+ age group. Overall, combined median post-discharge payments at 12 months were similar across the groups [80–89 (median $ 40,257) and 90+ (median$ 36,161), p = 0.14]. Conclusion Using MarketScan database, there has been a gradual decline in the number of decompressions being performed for LSS in elderly patients (>80 years of age), however there is no change in the proportion of octogenarians and nonagenarians undergoing decompression for LSS. There was no difference in rate of reoperations and overall health care utilization among the groups. Surgery for LSS can be offered to nonagenarians (in appropriately selected patients) with no difference in clinical outcomes and health care utilization, compared to octogenarians.

Background Bundled payments offer a lump sum for management of particular conditions over a specified period that has the potential to reduce health care payments. In addition, bundled payments represent a shift toward patient-centered reimbursement, which has the upside of improved care coordination among providers and may lead to improved outcomes. Objective To review the challenges and sources of payment variation and opportunities for restructuring bundled payments plans in the context of spine surgery. Methods We reviewed episodes of care over the past 10 years. We completed a search using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and the PICOS (Participants, Intervention, Comparison, Outcomes, Study Design) model in PubMed and Ovid databases to identify studies that met our search criteria. Results Ten studies met the search criteria, which were retrospective in design. The primary recipient of reimbursement was the hospital associated with the index procedure (59.7%–77% of the bundled payment), followed by surgeon reimbursement (12.8%–14%) and post–acute care rehabilitation (3.6%–7.3%). On average, the index hospitalization was $32,467, ranging from $11,880 to $107,642, depending on number of levels fused, complications, and malignancy. Readmission was shown to increase the 90-day payment by 50%–200% for uncomplicated fusion. Conclusions The implementation of spine surgery in bundled payment models offers opportunity for health care cost reduction. Patient heterogeneity, complications, and index hospitalization pricing are among factors that contribute to the challenge of payment variation. Development of standard care pathways, multidisciplinary coordination between inpatient and outpatient postoperative care, and empowerment of patients are also key elements of progress in the evolution of bundled payments in spine surgery. We anticipate more individualized risk-adjusted prediction models of payment for spine surgery, contributing to more manageable variation in payment and favorable models of bundled payments for payers and providers.

Background: Dabigatran is an anticoagulant (novel oral anticoagulant) that is a direct thrombin inhibitor and only recently has a reversal agent, idarucizumab, been made available (2015). Case Description: An 86-year-old male taking dabigatran for atrial fibrillation, acutely presented with the spontaneous onset of neck pain and quadriparesis. When the MRI demonstrated a C2-T2 spinal epidural hematoma, the patient was given the reversal agent idarucizumab. Due to his attendant major comorbidities, he was managed nonoperatively. Over the next 7 days, the patient’s neurological deficits resolved, and within 2 weeks, he had regained normal neurological function. Conclusion: In this case, a C2-T2 epidural cervical hematoma attributed to dabigatran that was responsible for an acute, spontaneous quadriparesis was successfully treated with the reversal agent idarucizumab without surgical intervention being warranted.

Objective Identify the impact of preoperative treatment of Osteoporosis (OP) on reoperation rates, complications and healthcare utilization following thoraco-lumbar (TL) spine fusions. Materials and Methods We used ICD9/10 and CPT codes to extract data from MarketScan (2000–2018). Patients were divided into two groups based on preoperative treatment of OP within one year prior to the index spinal fusion: medication (m-OP) cohort and non-medication (nm-OP) cohort. Outcomes (re-operation rates, re-admission, complications, healthcare utilization) were analyzed at 1-, 12-, 24- and 60-months. Results Of 3606 patients, 65% (n = 2330) of patients did not receive OP medications (nm-OP). At index hospitalization, there were no difference in LOS (median nm-OP: 3 days vs. m-OP:4 days), discharge to home (nm-OP 80% vs. m-OP 75%) and complications (nm-OP 13% vs. m-OP 12%). Reoperation rates were not different among the cohorts at 1- (nm-OP 5.7% vs. m-OP 4.2%), 2- (nm-OP 9.4% vs. m-OP 7.8) and 5 years (nm-OP 16.9% vs. m-OP 14.8%). Patients in m-OP cohort incurred higher overall median payments at 1 year ($17,866 vs. $ 16,010), 2 years ($38,634 vs. $34,454) and 5 years ($94,797 vs. $91,072) compared to nm-OP cohort. Conclusion Preoperative treatment of OP had no impact on complications, LOS, discharge disposition following TL fusions at index hospitalization. Similarly, no impact of preoperative treatment was noted in terms of reoperation rates at 12-, 24- and 60 months following the index spine fusion. Patients who received preoperative treatment for OP incurred higher health care utilization at 12-, 24- and 60 months following surgery.

Study Design: Retrospective cohort study. Objective: Recombinant human bone morphogenetic protein–2 (rhBMP-2) is used to achieve fusion in adult spinal deformity (ASD) surgery. Our aim was to investigate the long-term impact of rhBMP-2 use for clinical outcomes and health care utilization in this patient population. Methods: We conducted an analysis using MarketScan to identify health resource utilization of rhBMP-2 use for ASD after surgical intervention compared to fusion without rhBMP-2 at 24 months’ follow-up. Outcomes assessed included length of stay, complications, pseudoarthrosis, reoperation, outpatient services, and health care payments. Results: Of 7115 patients who underwent surgery for ASD, 854 received rhBMP-2 and 6261 were operated upon without use of rhBMP-2. One month after discharge, the rhBMP-2 cohort had a nonsignificant trend in fewer complications (15.38%) than those who did not receive rhBMP-2 (18.07%), P = .0558. At 12 months, pseudoarthrosis was reported in 2.8% of cases with no BMP and 01.14% of cases with BMP, P = .0048. Average payments at 12 months were $120 138 for the rhBMP-2 group and $118 373 for the no rhBMP-2 group, P = .8228. At 24 months, payments were $141 664 for the rhBMP-2 group and $144 179 for the group that did not receive rhBMP-2, P = .5946. Conclusions: In ASD surgery, use of rhBMP-2 was not associated with increased complications or reoperations at index hospitalization and 1-month follow-up. Overall payments, including index hospitalization, readmissions, reoperations, and outpatient services were not different compared to those without the use of rhBMP-2 at 12 months and 24 months after discharge.

Objective To identify the impact of different surgical approaches for lumbar degenerative disc disease (DDD) on complications, reoperations/readmissions, and health care utilization. Methods We used International Classification of Diseases, Ninth Revision and Tenth Revision and Current Procedural Terminology codes to extract data from MarketScan. Patients were divided into 6 groups: single-level anterior only (sA), single-level anterior + posterior (sAP), single-level posterior (sP), multilevel anterior (mA), multilevel anterior + posterior (mAP), and multilevel posterior only (mP). Outcomes of interest were cumulative complication rates, reoperation rates, readmission, and health care utilization at 6, 12, and 24 months. Results Of 148,499 patients, 3% had sA fusion and 54% had mP procedures. Patients in the mAP cohort incurred higher cumulative complication rates (21%) compared with sA (13%), sAP (15%), sP (14%), mA (18%), and mP (18%). Emergency room admissions within 30 days were highest in the mA cohort (14%) followed by mAP (11%) and mP (8%). At 12 and 24 months, patients with mA procedures were most likely to have either new fusion or refusion (8% and 12%) followed by sA (7% and 10%), sAP (4% and 7%), mAP (4% and 8%) mP (4% and 7%), and sP (3% and 7%). Compared with the mP cohort, patients in the mA cohort incurred 1.2 times the overall median payments, whereas mAP and sA incurred 1.1 times the payments at 12 months. This difference was further reduced at 24 months. Conclusions mAP procedures are associated with higher cumulative complications and health care utilization compared with other procedures and the difference in health care utilization tends to decrease over 12 and 24 months.

BACKGROUND Preoperative depression is a risk factor for poor outcomes after spine surgery. OBJECTIVE To understand effects of depression on spine surgery outcomes and healthcare resource utilization. METHODS Using IBM's MarketScan Database, we identified 52 480 patients who underwent spinal fusion. Retained patients were classified into 6 depression phenotype groups based on International Classification of Disease, 9th/10th Revision (ICD-9/10) codes and use/nonuse of antidepressant medications: major depressive disorder (MDD), other depression (OthDep), antidepressants for other psychiatric condition (PsychRx), antidepressants for physical (nonpsychiatric) condition (NoPsychRx), psychiatric condition only (PsychOnly), and no depression (NoDep). We analyzed baseline demographics, comorbidities, healthcare utilization/payments, and chronic opioid use. RESULTS Breakdown of groups in our cohort: MDD (15%), OthDep (12%), PsychRx (13%), NonPsychRx (15%), PsychOnly (12%), and NoDep (33%). Postsurgery: increased outpatient resource utilization, admissions, and medication refills at 1, 2, and 5 yr in the NoDep, PsychOnly, NonPsychRx, PsychRx, and OthDep groups, and highest in MDD. Postoperative opioid usage rates remained unchanged in MDD (44%) and OthDep (36%), and reduced in PsychRx (40%), NonPsychRx (31%), and PsychOnly (20%), with greatest reduction in NoDep (13%). Reoperation rates: 1 yr after index procedure, MDD, OthDep, PsychRx, NonPsychRx, and PsychOnly had more reoperations compared to NoDep, and same at 2 and 5 yr. In NoDep patients, 45% developed new depressive phenotype postsurgery. CONCLUSION EHR-defined classification allowed us to study in depth the effects of depression in spine surgery. This increased understanding of the interplay of mental health will help providers identify cohorts at risk for high complication rates, and health care utilization.

Introduction Despite the increasing use of national databases to conduct spine research, questions remain regarding their study validity and consistency. This study tested for similarity and inter-database reliability in reported measures between three commonly used national databases. Methods International Classification of Diseases, 9th edition (ICD-9) codes were used to identify elderly (80-100 years) who underwent spine surgery patients in Truven Health Analytics MarketScan® claims database, National (Nationwide) Inpatient Sample (NIS) discharge database and National Surgical Quality Improvement Program (NSQIP) database (2006-2016). Patient baseline characteristics, comorbid status, insurance enrollment, and outcomes were queried and compared. Results We analyzed 15,105 MarketScan, 40,854 NIS, and 7682 NSQIP patients between ages 80 to 100 years (median, 82 years) who underwent spine surgeries during the study period. A majority of patients in both MarketScan and NIS were insured by Medicare (97% vs. 94%). Patients in MarketScan had lower comorbidity scores (comorbidity, 0-2) compared to those in NIS and NSQIP databases. The most common diagnosis was spinal stenosis in MarketScan (54.4%), NIS (54.6%), and NSQIP databases (65.2%). Fusion was the most common procedure performed in MarketScan (48.9%) and NIS databases (46.2%), whereas decompression (laminectomy/laminotomy) was the most common procedure in the NSQIP database (51.84%). In-hospital complications (any) were 6.5% in the MarketScan cohort, 5.3% in the NIS, and 2.02% in the NSQIP cohort. In terms of 30-day complications (any), the MarketScan database reported higher complications rate (12.7%) compared to the NSQIP database (5.08%). In-hospital mortality was slightly higher in the NIS database (0.32%) compared to MarketScan (0.21%) and NSQIP database (0.2%). MarketScan and NIS databases showed an increased risk of complications with increasing age, whereas NIS and NSQIP showed increasing complications with a higher number of comorbidities. Male gender had higher complication at 30-day post-discharge using MarketScan and NSQIP database. Conclusions Patients in the NSQIP and NIS database have more comorbidities; patients in the MarketScan database had the highest number of perioperative and 30-day post-discharge complications with the highest number of fusion procedures performed. Patients in the NSQIP database had the lowest number of fusion procedures and complication rates. As databases gain popularity in spine surgery, clinicians and reviewers should be cautious in generalizing results to whole populations and pay close attention to the population being represented by the data from which the statistical significance was derived.

Early surgery after traumatic spinal cord injury (TSCI) has been associated with a greater neurological recovery and reduced secondary complications. In this study, we aimed to evaluate the trend of early TSCI surgery (within 24 hours) over two decades and the effect on length of hospitalization, complications, and hospital charges. We extracted emergency admissions of adults diagnosed with TSCI from the National Inpatient Sample database (1998-2016). We analyzed the trend of early surgery and concurrent trends of complication rate, length of stay (LOS) and hospital charges. These outcomes were then compared between early and late surgery cohorts. There were 3942 (53%) TSCI patients who underwent early surgery, and 3446 (47%) were operated after 24 hours. The combined patient group characteristics consisted of median age 43 years (IQR: 29-59), 73% males, 72% white, 44% private payer, 18% Medicare, 17% Medicaid, 51% cervical, 30% thoracic, 75% from large hospitals, and 79% from teaching hospitals. The trend of early surgery, adjusted for annual case-mix, increased from 45% in 1998 to 64% in 2016. Each year was associated with 1.60% more patients undergoing early surgery than the previous year (p-value

Background The cervical spine may be used as a harvesting site of local autograft material during anterior cervical discectomy and fusion procedures. We analyzed the quality and composition of bone grafts obtained from different parts of the cervical vertebrae in a cadaveric model. Methods Five fresh adult human cadavers with intact cervical spines were used. Using a Smith-Robinson anterior approach to expose C4-5 and C5-6 vertebrae, samples from 4 vertebral sites were harvested under a microscope. Anterior osteophytes were removed piecemeal by a Leksell rongeur (sample A). A high-speed burr was used to drill the endplates of C4-5 and C5-6 (sample C) and uncovertebral joints of C4-5 (sample B) and C5-6 (sample D). Then 20 slides (4 per cadaver) were prepared and analyzed. Results Tissue fragmentation was associated with use of the high-speed burr. Sample A had minimal tissue fragmentation. Samples B–D showed moderate to high fragmentation. Cartilage was found in all samples. Of the 20 slides, 6 contained soft tissues (sample A in 4, sample D in 2). Disc material was identified in 6 slides (sample A in 1, sample B in 4, sample D in 1). Sample A had the greatest number of intact osteocytes and chondrocytes, and sample B had the least. Conclusions Anterior osteophytes provide the highest number of osteocytes, with the highest osteocyte/chondrocyte ratio. Osteocyte viability is a function of vertebral body site and collection technique, with fragmentation caused by use of a high-speed burr decreasing the number of viable osteocytes.

Introduction Neurologic deficits from lumbar plexus nerve injuries commonly occur in patients undergoing lateral approaches. However, it is not yet clear what types of injury occur, where anatomically they are located, or what mechanism causes them. We aimed to study 1) the topographic anatomy of lumbar plexus nerves and their injuries in human cadavers after lateral transpsoas approaches to the lumbar spine, 2) the structural morphology of those injuries, and 3) the topographic anatomy of the lumbar plexus throughout the mediolateral approach corridor. Methods Fifteen adult fresh frozen cadaveric torsos (26 sides) underwent lateral approaches (L1-L5) by experienced lateral spine surgeons. The cadavers were subsequently opened and the entire plexus dissected and examined for nerve injuries. The topographic anatomy of the lumbar plexus and its branches, their injuries, and the morphology of these injuries were documented. Results Fifteen injuries were found with complete or partial nerve transections (Sunderland IV and V). Injuries were found throughout the mediolateral approach corridor. At L1/2, the iliohypogastric, ilioinguinal, and subcostal nerves were injured within the psoas major muscle, the retroperitoneal space, or the outer abdominal muscles and subcutaneous tissues. Genitofemoral nerve injuries were found in the retroperitoneal space. Nerve root injuries occurred within the retroperitoneal space and psoas muscle. Femoral nerve injuries were found only within the psoas major muscle. No obturator nerve injuries occurred. Conclusions Lateral approaches can lead to structural nerve damage. Knowledge of the complex plexus anatomy, specifically its mediolateral course, is critical to avoid approach-related injuries.

Study Design: Retrospective cohort study. Objectives: Lateral interbody fixation is being increasingly used for the correction of segmental sagittal parameters. One factor that affects postoperative correction is the resistance afforded by posterior hypertrophic facet joints in the degenerative lumbar spine. In this article, we describe a novel preoperative motion segment classification system to predict postoperative correction of segmental sagittal alignment after lateral lumbar interbody fusion. Methods: Preoperative computed tomography scans were analyzed for segmental facet osseous anatomy for all patients undergoing lateral lumbar interbody fusion at 3 institutions. Each facet was assigned a facet grade (min = 0, max = 2), and the sum of the bilateral facet grades was the final motion segment grade (MSG; min = 0, max = 4). Preoperative and postoperative segmental lordosis was measured on standing lateral radiographs. Postoperative segmental lordosis was also conveyed as a percentage of the implanted graft lordosis (%GL). Simple linear regression was conducted to predict the postoperative segmental %GL according to MSG. Results: A total of 36 patients with 59 operated levels were identified. There were 19 levels with MSG 0, 14 levels with MSG 1, 13 levels with MSG 2, 8 levels with MSG 3, and 5 levels with MSG 4. Mean %GL was 115%, 90%, 77%, 43%, and 5% for MSG 0 to 4, respectively. MSG significantly predicted postoperative %GL (P < .01). Each increase in MSG was associated with a 28% decrease in %GL. Conclusions: We propose a novel facet-based motion segment classification system that significantly predicted postoperative segmental lordosis after lateral lumbar interbody fusion.

Background Lateral approaches to the spine are increasing in popularity. However, details of the innervation pattern of the abdominal oblique muscles with the initial dissection have not been well studied. Methods Ten adult fresh-frozen cadavers (20 sides) were placed in the lateral position. On each side, the region in which transpsoas approaches are performed, between the iliac crest and the 12th rib, was dissected. The nerves, their course, and their muscular supply were studied. Results The subcostal nerve is the predominant nerve supply for the anterolateral abdominal muscle innervation. It is larger and has a wider field of distribution and more branches (8 on average) compared with the L1 (4 on average) and 11th intercostal nerves (2 on average 2). The proximal 6–10 cm of each nerve has few if any branches. The subcostal nerve is often (75%) located up to 5 cm inferior to the 12th rib in its initial course. The area of least concentration (“safe zone”) is located at an approximate midpoint between the lower edge of the 12th rib and the superior-most aspect of the iliac crest. A previously undescribed branch of the subcostal nerve was found traveling posterior to the quadratus lumborum and joining the remaining subcostal nerve in an anastomosis at or near the lateral position. Conclusions Knowledge of the innervation and nerve dominance patterns might help decrease postoperative complications such as sensory deficits or abdominal wall hernias. The subcostal nerve is the dominant nerve in both size and innervation of the oblique muscles in the lateral position, transpsoas approach.

Background Complications from lateral lumbar interbody fusion procedures range from neurologic deficits to organ and blood vessel injuries. Injury to the ureter has been reported though uncommon. The present study was performed to elucidate the anatomic relationship of the ureter to this surgical approach. Methods Eight adult cadavers (16 sides) were placed in the full lateral position, and the distal ureter was cannulated with a metal wire that was passed up to the kidney. Fluoroscopy was used to establish the position of the ureter in relation to the bony anatomy in this region. Results In the lumbar region, there was a posterior to anterior course of the left and right ureter. From the direct lateral position, the ureter was found to lie at or posterior to the anterior edge of the lumbar vertebral bodies. On 87.5% of sides, the ureter was on average 2.5 cm posterior to the anterior border of the vertebral bodies at L2, 3 cm posterior at L3, 1.0 cm posterior at L4, and on the margin of the anterior vertebral bodies at L5. In general, the ureter, from a lateral perspective, crossed the posterior third of the upper lumbar vertebrae, approached the middle third at L3, and reached the anterior third at L4/L5 before descending into the pelvis. Conclusions Owing to the proximity of the ureter to the lumbar vertebral bodies, it is imperative to verify that this structure is not in the surgical trajectory during lateral lumbar interbody fusion procedures if injury is to be avoided.