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Study Design: Retrospective longitudinal study., Objective: To investigate the association between lumbar intervertebral disk degeneration (DD) and the vertebral bone quality (VBQ) score., Background: The VBQ score that is based on magnetic resonance imaging has been proposed as a measure of lumbar spine bone quality and is a significant predictor of healthy versus osteoporotic bone. However, the role of segmental contributing factors on VBQ is unknown., Methods: Nonsurgical patients who underwent repeated lumbar magnetic resonance imaging scans, at least three years apart primarily for low back pain were retrospectively included. VBQ was assessed as previously described. DD was assessed using the Pfirrmann grading (PFG) scale. PFG grades were summarized as PFG L1-4 for the upper three lumbar disk levels, as PFG L4-S1 for the lower two lumbar disc levels, and as PFG L1-S1 for all lumbar disc levels. Multivariable linear mixed models were used with adjustments for age, sex, race, body mass index, and the clustering of repeated measurements., Results: A total of 350 patients (54.6% female, 85.4% White) were included in the final analysis, with a median age at baseline of 60.1 years and a body mass index of 25.8 kg/m 2 . VBQ significantly increased from 2.28 at baseline to 2.36 at follow-up ( P = 0.001). In the unadjusted analysis, a significant positive correlation was found between PFG L1-4 , PFG L1-S1 , and VBQ at baseline ( P < 0.05) that increased over time ( P < 0.005). In the adjusted multivariable analysis, PFG L1-4 ( β = -0.0195; P = 0.021), PFG L4-S1 ( β = -0.0310; P = 0.007), and PFG L1-S1 ( β = -0.0160; P = 0.012) were independently and negatively associated with VBQ., Conclusions: More advanced and long-lasting DD is associated with lower VBQ indicating less bone marrow fat content and potentially stronger bone. VBQ score as a marker of bone quality seems affected by DD., Competing Interests: J.A.C. reports consulting fees from Pfizer, Inc., Eli-Lilly, Globus Medical Inc., Regeneron, and AstraZeneca; membership of the scientific advisory board of Carestream, Image Analysis Group, and Image Biopsy Lab; A.A.S. reports royalties from Ortho Development, Corp.; private investments for Vestia Ventures MiRUS Investment, LLC, ISPH II, LLC, ISPH 3, LLC, and VBros Venture Partners X Centinel Spine; consulting fees from Clariance, Inc., Kuros Biosciences AG, and Medical Device Business Service, Inc.; speaking and teaching arrangements of DePuy Synthes Products, Inc.; membership of the scientific advisory board of Clariance Inc., and Kuros Biosciences AG; and trips/travel of Medical Device Business research support from Spinal Kinetics Inc., outside the submitted work. F.P.C. reports royalties from NuVasive, Inc.; private investments for 4WEB Medical/4WEB, Inc., Bonovo Orthopedics, Inc., Healthpoint Capital Partners, LP, ISPH II, LLC, ISPH 3 Holdings, LLC, Ivy Healthcare Capital Partners, LLC, Medical Device Partners II, LLC, Medical Device Partners III, LLC, Orthobond Corporation, Spine Biopharma, LLC, Synexis, LLC, Tissue Differentiation Intelligence, LLC, VBVP VI, LLC, VBVP X, LLC (Centinel) and Woven Orthopedics Technologies; consulting fees from 4WEB Medical/4WEB Inc., DePuy Synthes Spine, NuVasive Inc., Spine Biopharma, LLC, and Synexis, LLC; membership of scientific advisory board/other offices of Healthpoint Capital Partners, LP, Medical Device Partners III, LLC, Orthobond Corporation, Spine Biopharma, LLC, Synexis, LLC, and Woven Orthopedic Technologies; and research support from 4WEB Medical/4WEB Inc., Mallinckrodt Pharmaceuticals, Camber Spine, and Centinel Spine, outside the submitted work. Girardi reports royalties from Lanx Inc., and Ortho Development Corp.; private investments for Centinel Spine, and BCMID; stock ownership of Healthpoint Capital Partners, LP; and consulting fees from NuVasive, Inc., and DePuy Synthes Spine, outside the submitted work. Hughes reports research support from NuVasive Inc. and Kuros Biosciences AG; and fellowship support from NuVasive Inc. and Kuros Biosciences AG, outside the submitted work. The remaining authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective cross-sectional study., Objective: To evaluate the relationship between lumbar foraminal stenosis (LFS) and multifidus muscle atrophy., Background: The multifidus muscle is an important stabilizer of the lumbar spine. In LFS, the compression of the segmental nerve can give rise to radicular symptoms and back pain. LFS can impede function and induce atrophy of the segmentally innervated multifidus muscle., Methods: Patients with degenerative lumbar spinal conditions who underwent posterior spinal fusion for degenerative lumbar disease from December 2014 to February 2024 were analyzed. Multifidus fatty infiltration (FI) and functional cross-sectional area (fCSA) were determined at the L4 upper endplate axial level on T2- weighted MRI scans using dedicated software. Severity of LFS was assessed at all lumbar levels and sides using the Lee classification (Grade: 0 - 3). For each level, Pfirrmann and Weishaupt gradings were used to assess intervertebral disc disease (IVDD) and facet joint osteoarthritis (FJOA), respectively. Multivariable linear mixed models were run for the LFS grade of each level and side separately as the independent predictor of multifidus FI and fCSA. Each analysis was adjusted for age, sex, BMI, as well as FJOA and IVDD of the level corresponding to the LFS., Results: A total of 216 patients (50.5% female) with a median age of 61.6 years (IQR=52.0 - 69.0) and a median BMI of 28.1 kg/m2 (IQR=24.8 - 33.0) were included. Linear mixed model analysis revealed that higher multifidus FI (Estimate [Confidence interval]=1.7% [0.1 - 3.3], P=0.043) and lower fCSA (-18.6 mm2 [-34.3 - -2.6], P=0.022) were both significantly predicted by L2-L3 level LFS severity., Conclusion: The observed positive correlation between upper segment LFS and multifidus muscle atrophy points towards compromised innervation. This necessitates further research to establish the causal relationship and guide prevention efforts., Competing Interests: Declaration of conflicting interest: The Authors declare that there is no conflict of interest concerning materials or methods used in this study or the findings specified in this paper., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective review, single-institution cohort studies., Objective: To compare patients with earlier (i.e. <1.5 y) and later (i.e. >1.5 y) repeat lumbar surgery to patients with no repeat surgery according to clinical characteristics at index surgery., Background: Grouping patients as earlier or later repeat surgery may reveal different associations when compared to patients with no repeat surgery., Methods: Patients undergoing index surgery for diverse conditions reported preoperative demographic/clinical variables, including comorbidity and depressive symptoms. Extent (i.e. complexity) of surgery was assigned based on a valid index that included decompression, fusion and instrumentation. Co-existing disease at non-operated levels was ascertained from imaging reports. Postoperative records of all medical visits up to the time of this study (12 y) were reviewed for repeat surgery. Patients were grouped as earlier (<1.5 y) or later surgery (≥1.5 y) and compared to patients with no repeat surgery in separate multivariable analyses., Results: Among 1,334 patients (51% men, mean age 59), 82% did not have repeat surgery, 7% had earlier and 11% had later repeat surgery. Compared to no surgery, earlier surgery was associated with more comorbidity (OR 1.7, CI 1.1-2.6, P=0.02), positive depression screen (OR 1.9, CI 1.2-2.9, P=0.006), opioid use (OR 1.8, CI 1.2-2.8, P=0.008), and greater extent of index surgery (OR 1.1, CI 1.0-1.1, P=0.0009). Compared to no surgery, later surgery was associated with pre-index lumbar surgery (OR 1.9, CI 1.3-2.8, P=0.0005) and disease at non-operated levels at index surgery (OR 1.6, CI 1.0-2.4, P=0.05). Earlier surgeries were more likely to involve only the same vertebra as index surgery (51% vs. 16%) and later surgeries were more likely to involve only other levels (5% vs. 36%, P=0.01)., Conclusions: Earlier and later repeat lumbar surgeries differed in complexity and residual disease compared to no repeat surgery. These findings have implications for patient counseling regarding short and long-term postoperative spine health., Competing Interests: There are no conflicts of interest to disclose., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective review of a prospective cohort study., Objective: To identify the association between Oswestry Disability Index (ODI) subsections and overall improvement 2 years after lumbar surgery for degenerative lumbar spondylolisthesis (DLS)., Background: DLS often necessitates lumbar surgery. The ODI is a trusted measure for patient-reported outcomes (PROMs) in assessing spinal disorder outcomes. Surgeons utilize the ODI for baseline functional assessment and post-surgery progress tracking. However, it remains uncertain if and how each subsection influences overall ODI improvement., Methods: This retrospective cohort study analyzed patients who underwent lumbar surgery for DLS between 2016 and 2018. Preoperative and 2-year postoperative ODI assessments were conducted. The study analyzed postoperative subsection scores and defined ODI improvement as ODIpreop-ODIpostop >0. Univariate linear regression was applied, and receiver operating characteristic (ROC) analysis determined cut-offs for subsection changes and postoperative target values to achieve overall ODI improvement., Results: 265 patients (60% female, mean age 67±8 y) with a baseline ODI of 50±6 and a postoperative ODI of 20±7 were included. ODI improvement was noted in 91% (242 patients). Achieving a postoperative target score of ≤2 in subsections correlated with overall ODI improvement. Walking had the highest predictive value for overall ODI improvement (AUC 0.91, sensitivity 79%, specificity 91%). Pain intensity (AUC 0.90, sensitivity 86%, specificity 83%) and changing degree of pain (AUC 0.87, sensitivity 86%, specificity 74%) were also highly predictive. Sleeping had the lowest predictability (AUC 0.79, sensitivity 84%, specificity 65%). Except for sleeping, all subsections had a Youden-index >50%., Conclusion: These findings demonstrate how the different ODI subsections associate with overall improvement post-lumbar surgery for DLS. This understanding is crucial for refining preoperative education, addressing particular disabilities, and evaluating surgical efficacy. Additionally, it shows that surgical treatment does not affect all subsections equally., Competing Interests: Declaration of conflicting interest: The Authors declare that there is no conflict of interest concerning materials or methods used in this study or the findings specified in this paper., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective cohort study., Objective: To analyze the relationship of abdominal aortic calcification (AAC) and a reduction in the cross-sectional area (CSA) and the fatty infiltration (FI) of the paravertebral muscles in patients undergoing lumbar fusion surgery., Background: Both AAC and paraspinal muscle degeneration have been shown to be associated with poorer outcomes after surgical treatment of degenerative diseases of the lumbar spine. However, there is a lack of data on the association between AAC and paraspinal muscle changes in patients undergoing spine surgery., Methods: We retrospectively analyzed patients undergoing lumbar fusion for degenerative spinal pathologies. Muscular and spinal degeneration were measured on magnetic resonance imaging (MRI). AAC was classified on lateral lumbar radiographs. The association of AAC and paraspinal muscle composition was assessed by a multivariate regression analysis adjusted for age, sex, body mass index (BMI), comorbidities, and lumbar degeneration., Results: A total of 301 patients was included. Patients with AAC showed significantly higher degrees of intervertebral disc and facet joint degeneration as well as higher total endplate scores at the L3/4 level. The univariable regression analysis showed a significant positive correlation between the degree of AAC and the FI of the erector spinae (b=0.530, P<0.001) and multifidus (b=0.730, P<0.001). The multivariable regression analysis showed a significant positive correlation between the degree of AAC and the FI of the erector spinae (b=0.270, P=0.006) and a significant negative correlation between the degree of AAC and the CSA of the psoas muscle (b=-0.260, P=0.003)., Conclusion: This study demonstrates a significant and independent association between AAC and degeneration of the erector spinae and the psoas muscles in patients undergoing lumbar fusion. As both AAC and degeneration of paraspinal muscles impact postoperative outcomes negatively, preoperative assessment of AAC may aid in identifying patients at higher risk after lumbar surgery., Competing Interests: Declaration of Conflicting Interest: The Authors declare that there is no conflict of interest concerning materials or methods used in this study or the findings specified in this paper., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective review of prospectively collected data., Objective: The authors aim to investigate the association between muscle functional group characteristics and sagittal alignment parameters in patients undergoing anterior cervical discectomy and fusion., Summary of Background Data: The relationship between the morphology of cervical paraspinal muscles and sagittal alignment is not well understood., Materials and Methods: Patients with preoperative cervical magnetic resonance imaging and cervical spine lateral radiographs in standing position who underwent anterior cervical discectomy and fusion between 2015 and 2018 were reviewed. Radiographic alignment parameters included C2 to 7 lordosis, C2 to 7 sagittal vertical axis (SVA), C2 slope, neck tilt, T1 slope, and thoracic inlet angle. Muscles from C3 to C7 were categorized into four functional groups: sternocleidomastoid group, anterior group, posteromedial group, and posterolateral group (PL). A custom-written Matlab software was used to assess the functional cross-sectional area (fCSA) and percent fat infiltration (FI) for all groups. Multivariable linear regression analyses were conducted and adjusted for age, sex, and body mass index., Results: A total of 172 patients were included. Regression analyses demonstrated that a greater C2 to 7 SVA was significantly associated with a greater FI of the anterior group from C3 to C5 and with a higher fCSA of the PL group at C3 to C4, and C6 to 7. A larger C2 slope was significantly correlated with a greater FI of the anterior group at C3 to C4 and a higher fCSA of the PL group from C3 to C5., Conclusion: This work proposes new insights into the complex interaction between sagittal alignment and cervical paraspinal muscles by emphasizing the importance of these muscles in sagittal alignment. The authors hypothesize that with cervical degeneration, the stabilizing function of the anterior muscles decreases, which may result in an increase in the compensatory mechanism of the PL muscles. Consequently, there may be a corresponding increase in the C2 to C7 SVA and a larger C2 slope., Competing Interests: S.A.A. reports royalties from Ortho Development, Corp.; private investments for Vestia Ventures MiRUS Investment, LLC, IVY II, LLC, ISPH II, LLC, ISPH 3, LLC, HS2, LLC, HSS ASC Development Network, LLC, and Centinel Spine (Vbros Venture Partners V); consulting fee from Depuy Synthes Products Inc., Clariance Inc., Kuros Biosciences AG, Ortho Development Corp., Medical Device Business Service Inc.; speaking and teaching arrangements of DePuy Synthes Products Inc.; membership of scientific advisory board of Depuy Synthes Products Inc., Clariance Inc., and Kuros Biosciences AG; Medical Device Business Service Inc. and trips/travel of Medical Device Business; research support from Spinal Kinetics Inc., outside the submitted work. C.F.P. reports royalties from NuVasive Inc. Accelus; ownership interest for 4WEB Medical/4WEB Inc.; Healthpoint Capital Partners, LP; ISPH II LLC; ISPH 3 Holdings LLC; Ivy Healthcare Capital Partners LLC; Medical Device Partners II LLC; Medical Device Partners III LLC; Orthobond Corporation; Spine Biopharma LLC; Tissue Differentiation Intelligence LLC; VBVP VI LLC; VBVP X LLC; Woven Orthopedics Technologies; consulting fees from 4WEB Medical/4WEB Inc., DePuy Synthes, NuVasive Inc., Spine Biopharma LLC, and Synexis LLC, Accelus; membership of scientific advisory board/other office of Healthpoint Capital Partners, Medical Device Partners II LLC, Orthobond Corporation, Spine Biopharma LLC, and Woven Orthopedic Technologies; and research support from 4WEB Medical/4WEB Inc., Mallinckrodt Pharmaceuticals, Camber Spine, and Centinel Spine, outside the submitted work. G.F.P. reports royalties from Lanx Inc., and Ortho Development Corp.; private investments for BCIMD; and stock ownership of Healthpoint Capital Partners, LP, outside the submitted work. H.A.P. reports research support from Kuros Biosciences AG and Expanding Innovations Inc.; and fellowship support from NuVasive Inc. and Kuros Biosciences BV, outside the submitted work. The remaining authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective study., Objective: The aim of this study was to evaluate the association between severity and level of cervical central stenosis (CCS) and the fat infiltration (FI) of the cervical multifidus/rotatores (MR) at each subaxial levels., Summary of Background Data: The relationship between cervical musculature morphology and the severity of CCS is poorly understood., Methods: Patients with preoperative cervical magnetic resonance imaging (MRI) who underwent anterior cervical discectomy and fusion (ACDF) were reviewed. The cervical MR were segmented from C3 to C7 and the percent FI was measured using a custom-written Matlab software. The severity of the CCS at each subaxial level was assessed using a previously published classification. Grade 3, representing a loss of cerebrospinal fluid space and deformation of the spinal cord > 25%, was set as the reference and compared to the other gradings. Multivariable linear regression analyses were conducted and adjusted for age, sex, and body mass index., Results: 156 consecutive patients were recruited. A spinal cord compression at a certain level was significantly associated with a greater FI of the MR below that level. After adjustment for the above-mentioned confounders, our results showed that spinal cord compression at C3/4 and C4/5 was significantly associated with greater FI of the MR from C3 to C6 and C5 to C7, respectively. A spinal cord compression at C5/6 or C6/7 was significantly associated with greater FI of the MR at C7., Conclusion: Our results demonstrated significant correlations between the severity of CCS and a greater FI of the MR. Moreover, significant level-specific correlations were found. A significant increase in FI of the MR at the levels below the stenosis was observed in patients presenting with spinal cord compression. Given the segmental innervation of the MR, the increased FI might be attributed to neurogenic atrophy., Level of Evidence: 3., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A retrospective analysis of prospectively collected data., Objective: To assess the association between intervertebral disk degeneration and hip and knee osteoarthritis (OA) in patients with degenerative lumbar spondylolisthesis., Background: The co-occurrence of hip OA and degenerative spinal pathologies was first described as the "hip-spine syndrome" and has also been observed in knee OA. It remains unclear whether both pathologies share an underlying connection beyond demographic factors., Materials and Methods: Intervertebral disk degeneration was classified by the Pfirrmann Classification and intervertebral vacuum phenomenon. Intervertebral vacuum phenomenon was classified into mild (1 point), moderate (2 points), and severe (3 points) at each level and combined into a lumbar vacuum score (0-15 points). Similarly, a lumbar Pfirrmann grade was calculated (5-25 points). Patients with previous hip or knee replacement surgery were classified as having an OA burden. We used multivariable regression to assess the association between OA and disk degeneration, adjusted for age, body mass index, and sex., Results: A total of 246 patients (58.9% female) were included in the final analysis. Of these, 22.3% had OA burden. The multivariable linear regression showed an independent association between OA burden and lumbar vacuum (β = 2.1, P <0.001) and Pfirrmann grade (β = 2.6, P <0.001). Representing a 2.1 points higher lumbar vacuum and 2.6 points higher lumbar Pfirrmann grade after accounting for demographic differences., Conclusions: Our study showed that OA burden was independently associated with the severity of the intervertebral disk degeneration of the lumbar spine. These findings give further weight to a shared pathology of OA of large joints and degenerative processes of the lumbar spine., Level of Evidence: 3., Competing Interests: A.A.S. reports royalties from Ortho Development, Corp.; private investments for Vestia Ventures MiRUS Investment, LLC, IVY II, LLC, ISPH II, LLC, ISPH 3, LLC, HS2, LLC, HSS ASC Development Network, LLC, and Centinel Spine (Vbros Venture Partners V); consulting fee from Depuy Synthes Products Inc., Clariance Inc., Kuros Biosciences AG, Ortho Development Corp., Medical Device Business Service Inc.; speaking and teaching arrangements of DePuy Synthes Products Inc.; membership of scientific advisory board of Depuy Synthes Products Inc., Clariance Inc., and Kuros Biosciences AG; Medical Device Business Service Inc. and trips/travel of Medical Device Business; research support from Spinal Kinetics Inc., outside the submitted work. Dr. F.P.C. reports royalties from NuVasive Inc. Accelus; ownership interest for 4WEB Medical/4WEB Inc.; Healthpoint Capital Partners, LP; ISPH II, LLC; ISPH 3 Holdings, LLC; Ivy Healthcare Capital Partners, LLC; Medical Device Partners II, LLC; Medical Device Partners III, LLC; Orthobond Corporation; Spine Biopharma, LLC; Tissue Differentiation Intelligence, LLC; VBVP VI, LLC; VBVP X, LLC; Woven Orthopedics Technologies; consulting fees from 4WEB Medical/4WEB Inc., DePuy Synthes, NuVasive Inc., Spine Biopharma, LLC, and Synexis, LLC, Accelus; membership of scientific advisory board/other office of Healthpoint Capital Partners, Medical Device Partners II, LLC, Orthobond Corporation, Spine Biopharma, LLC, and Woven Orthopedic Technologies; and research support from 4WEB Medical/4WEB, Inc., Mallinckrodt Pharmaceuticals, Camber Spine, and Centinel Spine, outside the submitted work. F.P.G. reports royalties from Lanx Inc., and Ortho Development Corp.; private investments for BCIMD; and stock ownership of Healthpoint Capital Partners, LP, outside the submitted work. Hughes reports research support from Kuros Biosciences AG and fellowship support from NuVasive Inc. and Kuros Biosciences BV, outside the submitted work. The remaining authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective cohort analysis., Objective: To elucidate trends in the utilization of intraoperative neuromonitoring (IONM) during anterior cervical discectomy and fusion (ACDF) procedures in NY state using the Statewide Planning and Research Cooperative System and to determine if utilization of IONM resulted in a reduction in postoperative neurological deficits., Summary of Background Data: IONM has been available to spinal surgeons for several decades. It has become increasingly prevalent in all facets of spinal surgery including elective ACDF procedures. The utility of IONM for preventing a neurological deficit in elective spine procedures has recently been called into question., Materials and Methods: The Statewide Planning and Research Cooperative System database were accessed to perform a retrospective cohort study comparing monitored versus unmonitored ACDF procedures between 2007 and 2018 as defined by the International Classification of Disease-9 and 10 Procedural Coding System (ICD-9 PCS, ICD-10 PCS) codes. Patient demographics, medical history, surgical intervention, pertinent in-hospital events, and urban versus rural medical centers (as defined by the United States Office of Management and Budget) were recorded. Propensity-score-matched comparisons were used to identify factors related to the utilization of IONM and risk factors for neurological deficits after elective ACDF., Results: A total of 70,838 [15,092 monitored (21.3%) and 55,746 (78.7%) unmonitored] patients' data were extracted. The utilization of IONM since 2007 has increased in a linear manner from 0.9% of cases in 2007 to 36.7% by 2018. Overall, baseline characteristics of patients who were monitored during cases differed significantly from unmonitored patients in age, race/ethnicity, insurance type, presence of myelopathy or radiculopathy, and Charlson Comorbidity Index; however, only race/ethnicity was statistically significant when analyzed using propensity-score-matched. When comparing urban and rural medical centers, there is a significant lag in the adoption of the technology with no monitored cases in rural centers until 2012 with significant fluctuations in utilization compared with steadily increasing utilization among urban centers. From 2017 to 2018, reporting of neurological deficits after surgery resembled literature-established norms. Pooled analysis of these years revealed that the incidence of neurological complications occurred more frequently in monitored cases than in unmonitored (3.0% vs. 1.4%, P < 0.001)., Conclusions: The utility of IONM for elective ACDF remains uncertain; however, it continues to gain popularity for routine cases. For medical centers that lack similar resources to centers in more densely populated regions of NY state, reliable access to this technology is not a certainty. In our analysis of intraoperative neurological complications, it seems that IONM is not protective against neurological injury., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Cross-sectional preoperative and intraoperative imaging study of L4-L5 lumbar degenerative spondylolisthesis (LDS)., Objective: To determine if alternate imaging modalities would identify LDS instability that did not meet the criteria for instability based on comparison of flexion and extension radiographs., Summary of Background Data: Pain may limit full flexion and extension maneuvers and thereby lead to underreporting of true dynamic translation and angulation in LDS. Alternate imaging pairs may identify instability missed by flexion-extension., Materials and Methods: Consecutive patients scheduled for surgery for single-level L4-L5 LDS had preoperative standing radiographs in the lateral, flexion, and extension positions, supine computed tomography (CT) scans, and intraoperative fluoroscopic images in the supine and prone positions after anesthesia but before incision. Instability was defined as translation ≥3.5 mm or angulation ≥11° between the following pairs of images: (1) flexion-extension; (2) CT-lateral; (3) lateral-intraoperative supine; (4) lateral-intraoperative prone; and (5) intraoperative supine-prone., Results: Of 240 patients (mean age 68 y, 54% women) 15 (6%) met the criteria for instability by flexion-extension, and 225 were classified as stable. Of these 225, another 84 patients (35% of total enrollment) were reclassified as unstable by comparison of CT-lateral images (21 patients) and by lateral-intraoperative images (63 patients). Nine of the 15 patients diagnosed with instability by flexion-extension had fusion (60%), and 68 of the 84 patients reclassified as unstable by other imaging pairs had fusion (81%) ( P =0.07). The 84 reclassified patients were more likely to undergo fusion compared with the 141 patients who persistently remained classified as stable (odds ratio=2.6, 95% CI: 1.4-4.9, P =0.004)., Conclusions: Our study provides evidence that flexion and extension radiographs underreport the dynamic extent of LDS and therefore should not be solely relied upon to ascertain instability. These findings have implications for how instability should be established and the extent of surgery that is indicated., Competing Interests: The authors report no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective descriptive study., Objective: The aim of this study was to create topographical maps of occipital bone thickness and venous sinus (VS) presence to assess the risks of screw insertion in four commercially available occipital plates., Summary of Background Data: Craniocervical junction instability and deformity are serious pathological conditions that require posterior fixation of the occipital bone to the cervical vertebrae. Insertion of occipital bone screws requires evaluation of both occipital bone thickness for effective internal fixation and intracranial VS presence for vascular injury prevention. Despite the surgical risks, there is a paucity of research on safe screw placement., Methods: We created a matrix of 231 standardized measurement points to analyze the occipital bone thickness and VS presence in cervical spine CT angiograms. These measurements were used to create topographical maps of occipital bone thickness and likelihood of VS presence, which we then compared to the screw hole configurations of four occipital plates., Results: Hundred patients were assessed. Maximum occipital bone thickness of 13.9 ± 3.3 mm was midline in the occipital bone, 45 mm from the foramen magnum, around the external occipital protuberance (EOP). Regions with thicknesses >8 mm were 2 cm lateral to the EOP at the level of the superior nuchal line and 2.5 cm inferior to the EOP. The area with the highest VS presence rate was around the EOP and the superior nuchal line. The right transverse VS was more prominent in both sexes., Conclusion: There is a limited area of the occipital bone with thicknesses for enough screw purchase. Previous studies have shown 8 mm as the minimum screw length to reduce the risk of implant failure. In our analysis, only "T"-shaped plates had configurations with thicknesses >8 mm for each screw hole. For every screw hole in the analyzed occipital plates, there was a possibility of VS presence ranging from 8% to 33%.Level of Evidence: 5., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective observational study., Objective: The aim of this study was to investigate the spinal cord safety margins for C2 instrumentation., Summary of Background Data: Intraoperative spinal cord injury during C2 spine surgery is a rare, but potentially life-threatening complication. Preoperative planning for C2 instrumentation mainly focuses on C2 pedicle bony dimensions on CT and the vertebral artery location and few studies have evaluated C2 spinal cord safety margins., Methods: We measured two distances in C2 bilaterally: C2 pedicle to dura distance (P-D), defined as a transverse line that measured the shortest distance between the medial wall of the C2 pedicle and the dural sac, and C2 pedicle to spinal cord (P-SC), defined as a transverse line that measured the shortest distance between the medial wall of the C2 pedicle and spinal cord. We defined the distances >4 mm as safe for instrumentation., Result: A total of 146 patients (mean age 71.2, 50.7% female) were included. The average distances were 5.5 mm for C2 left PD, 5.9 mm for C2 right P-D, 10.1 mm for C2 left P-SC, and 10.6 mm for C2 right P-SC. Twenty-eight (21.4%) patients had C2 P-D distances <4 mm and of those two (7%) patients had distances <2 mm. There were more female patients with C2 P-D distances under 4 mm compared to males. No patient had C2 P-SC distances <4 mm., Conclusion: We demonstrated that around 20% of patients had C2 P-D distance <4 mm, but no patient had C2 P-SC distance <4 mm. Since a lateral misplacement can lead to a potentially fatal vertebral artery injury, medial screw trajectory is recommended for C2 pedicle instrumentation with consideration of these safety margins.Level of Evidence: 3., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective analysis of 73 standalone lateral lumbar interbody fusion (LLIF) procedures to identify any association between the amount of coronal curve correction and lumbosacral plexus injuries and/or postoperative pain., Objective: To address if there is any association between the amount of correction in both the coronal and sagittal planes and the development of postoperative neurological deficit and/or anterior thigh/groin pain., Summary of Background Data: LLIF is a powerful tool for the restoration of spinal alignment including correction of small degenerative curves of the lumbar spine and increase of lumbar lordosis. Concerns remain about its safety regarding injuries of the lumbosacral plexus, which occur with a prevalence ranging from 0.7% to 23%., Methods: The medical records and spinal radiographs of patients undergoing standalone LLIF for symptomatic degenerative scoliosis of the lumbar spine were retrospectively reviewed during a 6-year period., Results: Thirty patients (73 levels) met the inclusion criteria and were followed for a mean of 21 months (range, 9-39 mo). Average age at the time of surgery was 67 years (range, 50-78 yr). Immediately after surgery, a motor deficit was recorded in 6 patients and a sensory deficit in 17 patients. Statistical analysis did not reveal any significant association between the amount of coronal curve correction, restoration of lumbar lordosis or increase in lumbar spine height, and the development of postoperative motor or sensory deficits. Seventeen patients complained of anterior thigh/groin pain immediately postoperative. A statistically significant association was identified between postoperative anterior thigh/groin pain and the magnitude of curve correction (P = 0.005), as well as the increase in lumbar lordosis (P = 0.040)., Conclusion: There is a strong association between the development of postoperative anterior thigh/groin pain and the amount of coronal curve correction, as well as the increase in lumbar lordosis., Level of Evidence: 4.