Sacral slanting—defined as the oblique tilt of the upper sacral endplate measurable on standing anteroposterior whole-spine radiographs—is a distinctive and clinically underappreciated finding in adolescent idiopathic scoliosis (AIS). Its etiology is multifactorial and incidence among AIS patients reaches 40%. The direction and degree of sacral slanting interact with the distal lumbar curve type (L4-left vs. L4-right) to influence the pattern of postoperative radiographic changes at the distal spine and shoulder. In patients with L4-left curves and left-sided slanting, stopping fusion at L3 generally prevents coronal decompensation. Furthermore, 5-year data show that the disc wedge angle below the lowermost instrumented vertebra (LIV) does not progress when LIV is L3, and patient-reported outcomes are preserved without revision surgery. When fusion extends to L4 in patients with high sacral slanting, coronal decompensation is more frequent, yet functional outcomes remain comparable and no revision has been required in published series to date, indicating that the decompensation observed is radiographically significant but clinically tolerable within the medium term. In Lenke 1A patients with right-sided sacral slanting (L4-right type), the slanting lowers the last touching vertebra and may facilitate distal adding-on. In Lenke 2A patients with right-sided slanting, distal adding-on serves as a natural shoulder-rebalancing mechanism and may be reasonably monitored conservatively rather than reflexively treated, pending further validation in independent cohorts, unless progressive or symptomatic. Across all scenarios, the optimal distal fusion level remains an unresolved dilemma requiring further long-term prospective study. This review synthesizes the available literature to characterize sacral slanting as a promising radiographic parameter that may serve as a potentially useful adjunct in distal fusion level planning, while highlighting the need for prospective multicenter validation before its routine incorporation into surgical decision-making in AIS.
Objective To investigate feasibility and effectiveness of minimally invasive scoliosis surgery (MISS) via posterior approach in patients with adolescent idiopathic scoliosis (AIS) presenting with very severe curve exceeding 80°.
Methods A total of 257 flexible AIS patients who underwent deformity correction using posterior MISS were retrospectively categorized into 3 groups based on the curve magnitude: moderate (M group, main Cobb angle <60°, n=142), severe (S group, 60°–80°, n=91), and very severe (VS group, ≥80°, n=24). Radiological parameters, perioperative outcomes, and complication rates were compared among the 3 groups.
Results The VS group required significantly longer operative times (p<0.001), more fused segments (p<0.001), and a greater number of rib resections during thoracoplasty (p=0.032) compared to the other groups. Despite these surgical demands, there were no statistical differences in the correction rate (p=0.954) and last follow-up thoracic kyphosis (p=0.830) among the 3 groups. Regarding complications, while the overall complication rate showed no statistical difference, the VS group required significantly more invasive management for pleural effusions (p=0.012).
Conclusion Posterior MISS demonstrated acceptable radiological and perioperative outcomes even in flexible AIS with Cobb angles ≥80°. These findings suggest the posterior MISS can be a feasible surgical option for selected very severe AIS patients with sufficient flexibility.
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From the Editor-in-Chief: Featured Articles in the July 2026 Issue Inbo Han Neurospine.2026; 23(3): 513. CrossRef
A Commentary on “Feasibility of Minimally Invasive Scoliosis Surgery in Adolescent Idiopathic Scoliosis Exceeding 80° of Curve Magnitude” Ibrahim Obeid Neurospine.2026; 23(3): 577. CrossRef
Objective This study aims to compare the risk of subsequent surgery following surgical treatment of clinical adjacent-segment pathology (CASP) after lumbar fusion, specifically evaluating decompression alone versus decompression with extension of the fusion.
Methods Using the Swespine registry, we included patients who had surgical treatment for CASP following index lumbar fusion surgery, 1997–2019. The cohort was divided according to CASP treatment: decompression alone or decompression with extended fusion. A comparison of subsequent surgeries was made with Kaplan-Meier analysis and Cox regressions adjusted for potential confounders (age, sex, body mass index, smoking status, number of operated levels at CASP surgery, number of fused levels at index fusion surgery, and diagnosis for CASP surgery).
Results A total of 2,521 patients were included, 1,176 (47%) in the decompression-group and 1,345 (53%) in the extended fusion group and the mean follow-up was 6.1±4.4 years. Mean age at CASP surgery was 61 years and 1,588 (63%) were females. The median time to subsequent surgery was 1.7 years (range, 0.9–3.7 years). Kaplan-Meier–estimated probability of subsequent surgeries at 5 years was 18% (95% confidence interval [CI], 15%–20%) for the decompression-group and 25% (95% CI, 22%–27%) for the extended fusion group. The hazard ratio was 1.26 (95% CI, 1.02–1.56; p=0.032) for those with extended fusion.
Conclusion Extension of fusion for CASP was associated with significantly higher risk of subsequent surgery, but causality should be interpreted with caution as radiographic information on instability, deformity, or foraminal stenosis could not be verified.
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A Commentary on “How to Treat Adjacent-Segment Pathology Following Lumbar Fusion Surgery: Decompression Alone or Decompression With Extended Fusion Surgery?” Jang W. Yoon Neurospine.2026; 23(3): 564. CrossRef
When Is Fusion Necessary in Addressing Symptomatic Adjacent Level Pathology – A Commentary on “How to Treat Adjacent-Segment Pathology Following Lumbar Fusion Surgery: Decompression Alone or Decompression With Extended Fusion Surgery?” Marc A. Arslanian, Vignessh Kumar, Lee A. Tan Neurospine.2026; 23(3): 561. CrossRef
From the Editor-in-Chief: Featured Articles in the July 2026 Issue Inbo Han Neurospine.2026; 23(3): 513. CrossRef
Objective Adjacent segment disease (ASD) is a recognized long-term complication after anterior cervical discectomy and fusion (ACDF). Cervical disc arthroplasty (CDA) was introduced as a motion-preserving alternative, thought to reduce stress at adjacent levels and lower ASD risk. This study aimed to compare the risk of ASD requiring reoperation after ACDF and CDA and identify factors associated with ASD.
Methods This retrospective cohort study used prospectively collected data from the Swedish Spine Registry (Swespine) and included adult patients undergoing anterior cervical surgery for degenerative cervical disease between 2006 and 2026. ASD was defined as a secondary operation at an adjacent level ≥12 months after the index procedure. Cumulative incidence was estimated using Kaplan-Meier analysis, and associations with ASD were evaluated using multivariable Cox proportional hazards regression. Radiological or conservatively treated ASD were not assessed.
Results A total of 9,338 patients were included (ACDF, n=9,005; CDA, n=333). During 45,666 person-years follow-up, 509 ASD events occurred (incidence rate 11.1 per 1,000 person-years). Cumulative incidence was 4.9% at 5 years and 10.4% at 10 years. CDA was associated with lower ASD hazard than ACDF (hazard ratio [HR], 0.61) though this association was not significant after propensity score matching (HR, 0.88). Multilevel procedures (HR, 0.61), increasing age (HR, 0.96 per year), and radiculopathy were associated with lower risk, while myelopathy or stenosis was associated with higher risk (HR, 1.22).
Conclusion The long-term risk of ASD requiring reoperation was lower than previously reported. After adjustment, CDA was associated with lower ASD risk compared to ACDF, although the absolute difference was small, and the clinical significance remains uncertain.
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A Commentary on “A Nationwide Registry Study Comparing Long-term Risk of Adjacent Segment Disease Requiring Reoperation Following Anterior Cervical Discectomy and Fusion Versus Cervical Disc Arthroplasty” Samuel K. Cho Neurospine.2026; 23(3): 536. CrossRef
From the Editor-in-Chief: Featured Articles in the July 2026 Issue Inbo Han Neurospine.2026; 23(3): 513. CrossRef
Anterior cervical decompression and fusion for Samartzis Type I Klippel–Feil syndrome complicated by cervical radiculopathy with radiographic spinal cord compression: a case report of sandwich-type interposed mobile segment Baopeng Zeng, Shengxing Liu Frontiers in Surgery.2026;[Epub] CrossRef
Objective Parkinson disease (PD) is frequently characterized by a forward-bent posture that increases biomechanical stress on the lumbar spine, which increases the rate of subsequent lumbar surgeries after spinal fusions. This study aimed to evaluate the rates of additional lumbar surgeries following spinal fusion in patients with PD.
Methods Data from the Health Insurance Review and Assessment Service of the Republic of Korea were retrospectively analyzed. PD was identified using the International Classification of Diseases, 10th Revision code G20. Patients with PD were matched with those without PD in a 3:1 ratio based on sex, age, and Charlson Comorbidity Index using the greedy nearest neighbor matching method. The primary outcome was the rate of subsequent lumbar surgeries following spinal fusion within the 7-year follow-up period. The timing of these reoperations was also assessed.
Results A total of 2,287 patients with PD and 6,861 matched patients without PD were included in this study. The prevalence of PD among patients undergoing lumbar fusion surgery remained stable throughout the study period. Patients with PD had 1.6-fold higher odds to undergo reoperation compared with the non-PD cohort. No significant difference was observed in the timing of additional surgeries between the groups.
Conclusion Patients with PD faced 1.6-fold higher odds of subsequent lumbar surgeries following spinal fusion compared to those without the disease. This finding suggests the need for a cautious treatment approach and thorough preoperative optimization when considering lumbar fusion in this population.
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A Commentary on “Rates of Subsequent Lumbar Surgery Following Spinal Fusion in Patients With Parkinson Disease: A Propensity-Score Matched Nationwide Cohort Analysis” Yusuke Nishimura Neurospine.2026; 23(3): 547. CrossRef
From the Editor-in-Chief: Featured Articles in the July 2026 Issue Inbo Han Neurospine.2026; 23(3): 513. CrossRef
Spine imaging represents a complex diagnostic frontier characterized by anatomical variability, motion artifacts, metallic instrumentation interference, and significant inter-reader diagnostic variability (κ=0.20 across institutions). While conventional discriminative artificial intelligence (AI) models achieve >95% accuracy in detecting degenerative changes, they remain limited by data scarcity, heterogeneous protocols, and poor generalizability. In the spine, these limitations are particularly relevant because clinical decisions can often depend on subtle distinctions (such as differentiating levels of canal or foraminal stenosis, characterizing Modic endplate changes, or assessing pedicle and vertebral morphology), where small inconsistencies can meaningfully alter management or surgical planning. Generative AI (GenAI) systems—including generative adversarial networks (GANs), diffusion models, and vision-language models (VLMs)—offer a paradigm shift by learning underlying data structures to generate high-quality synthetic outputs rather than merely classifying existing data. This narrative review, conducted using SANRA (scale for the assessment of narrative review articles) methodology across PubMed, Scopus, Embase, and Cochrane Library, examined GenAI applications in spine imaging. Eligible studies included observational designs through randomized controlled trials exploring image reconstruction, synthetic computed tomography (CT) generation, segmentation, and surgical planning applications. GAN-generated synthetic magnetic resonance imaging sequences reduce scan times by ~40% while maintaining diagnostic confidence; diffusion models enable radiation-free synthetic CT for preoperative planning; and VLMs generate structured radiology reports with hallucination rates <1.12%. However, critical barriers impede clinical translation: external validation gaps reveal AI performance collapse in real-world cohorts (sensitivity drops to 54.9% in cervical fracture detection); hallucinations and anatomical inaccuracies risk misguiding implant sizing; bias amplification magnifies demographic underrepresentation; and fragmented, small datasets lack standardized benchmarks. Technical fragility, computational demands, clinician trust deficits, and unresolved regulatory frameworks for iteratively-updating systems remain unaddressed. Successful integration requires coordinated development across 5 priorities: (1) multi-institutional datasets with cross-vendor harmonization, (2) federated learning frameworks preserving privacy, (3) uncertainty quantification and explainability tools, (4) outcome-linked clinical validation replacing technical metrics, and (5) workflow-integrated systems with DICOM-native interfaces and provenance tracking.
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A Commentary on “From Pixels to Precision: Generative Artificial Intelligence as a Paradigm Shift in Spine Imaging—Technical Foundations, Clinical Applications, and the Path to Safe Clinical Deployment” Fabrizio Russo, Luca Ambrosio, Gianluca Vadalà, Vincenzo Denaro Neurospine.2026; 23(2): 314. CrossRef
From the Editor-in-Chief: Featured Articles in the April 2026 Issue Inbo Han Neurospine.2026; 23(2): 227. CrossRef
Objective To evaluate whether combining clinical frailty with magnetic resonance imaging (MRI)-derived posterior paraspinal muscle degeneration identifies perioperative risk phenotypes in adults aged ≥75 years undergoing lumbar fusion.
Methods We retrospectively studied patients aged ≥75 years undergoing lumbar fusion with preoperative lumbar MRI. Frailty was assessed using the Fried phenotype (frail: score ≥3). Posterior paraspinal muscle degeneration across L1–S1 was quantified using automated segmentation and a composite posterior frailty index (PFI); severe degeneration was defined as the upper quartile of PFI. Patients were classified into 4 frailty×muscle phenotypes. Primary outcomes were any in-hospital complication and prolonged length of stay (LOS ≥16 days).
Results Among 248 patients, phenotypes A–D (A, nonfrail/nonsevere; B, frail/nonsevere; C, nonfrail/severe; D, frail/severe) comprised 132, 54, 20, and 42 patients, respectively. Any in-hospital complication occurred in 18.2% of phenotype A compared with 50.0%–57.1% in phenotypes B–D (p<0.001). Prolonged LOS (≥16 days; cohort 75th percentile) occurred in 0.8% of phenotype A versus 38.9% (B), 35.0% (C), and 78.6% (D) (p<0.001), corresponding to absolute risk increases of +34.2 to +77.8 percentage points. After adjustment, higher-risk phenotypes remained independently associated with increased odds of any complication and prolonged LOS; however, the prolonged-LOS odds estimates were imprecise due to sparse events in the reference group. Phenotype was not independently associated with 90-day readmission. Pain improvement (ΔVAS [visual analogue scale]) was attenuated in phenotypes B and D, while differences in ΔODI (Oswestry Disability Index) were not statistically significant.
Conclusion Integrating frailty and MRI-based posterior paraspinal degeneration provides actionable stratification of complication and prolonged LOS risk after lumbar fusion in older adults.
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From the Editor-in-Chief: Featured Articles in the April 2026 Issue Inbo Han Neurospine.2026; 23(2): 227. CrossRef
A Commentary on “Frailty-Muscle Phenotypes Predict Outcomes After Lumbar Fusion in Adults Aged ≥75 Years: A Retrospective Cohort Study” Julie L. Chan, Daniel J. Hoh Neurospine.2026; 23(2): 255. CrossRef
Objective To investigate the relationship between C1 screw trajectory and occipital bone erosion in C1–2 posterior fixation.
Methods This retrospective cohort study analyzed 27 patients (54 screws) who underwent C1–2 posterior fixation between March 2018 and March 2023 at a single institution by multiple surgeons. Screws were classified by trajectory: Tan technique (n=39) or Harms-Goel (HG) technique (n=15). Primary outcome was occipital bone erosion; the secondary outcome was breach of inner cortical layer. Per-screw analysis was performed using generalized estimating equations to account for bilateral screw clustering.
Results Mean follow-up was 48.3 (range, 24–84) months. Occipital bone erosion occurred in 51.3% (20 of 39) of Tan screws versus 6.7% (1 of 15) of HG screws (p<0.001). Breach of inner cortical layer occurred exclusively with the Tan technique (10.3% vs. 0%, p=0.302). In mixed Tan+HG cases (n=3), erosion occurred only on the Tan side (2 of 3 screws) with no erosion on HG side (0 of 3 screws). C1 upper line transgression was a critical risk factor; no erosion occurred in screws that did not exceed this anatomical landmark (adjusted relative risk [RR], 6.82; 95% confidence interval [CI], 2.41–19.31). Additional risk factors included height O–C1 ≤4.5 mm (RR, 3.81; 95% CI, 1.51–6.28) and height O–C1 extension ≤1 mm (RR, 4.86; 95% CI, 2.05–11.53). No patients required reoperation for erosion-related symptoms during follow-up.
Conclusion Screw trajectory is the primary determinant of occipital bone erosion following C1–2 fixation. The HG technique demonstrated significantly lower erosion rates (6.7% vs. 51.3%). When anatomically feasible, HG technique may be considered to reduce erosion risk.
Objective This study aims to evaluate the clinical and radiological outcomes of posterior reduction and fusion strategies, with or without interfacet joints distraction and cage implantation, based on reducibility, in the surgical management of atlantoaxial dislocation (AAD).
Methods Patients who underwent posterior reduction and fusion surgery for AAD in our institution were included. They were categorized into 2 groups based on reducibility. Japanese Orthopaedic Association (JOA), visual analogue scale (VAS), and patient-reported satisfaction scores were collected. The atlantodental interval, distance of the tip of the odontoid to Chamberlain’s line (DOCL), clivus-axial angle (CXA) and mean obliquity of the atlantoaxial articular facet (OAAF) were measured on computed tomography (CT) images. Fusion was evaluated using CT and dynamic x-rays.
Results A total of 90 patients (45 males and 45 females) were included. Among them, 54 patients in the reducible group underwent direct posterior reduction and fusion, and 36 patients in the irreducible group were treated with additional interfacet joint distraction and cage implantation. All patients showed significant improvements in JOA and VAS scores postoperatively. In the irreducible group, the preoperative CXA was smaller, whereas the OAAF was greater. Receiver operating characteristic curve analysis identified optimal cutoff value of OAAF in predicting reducibility was 32.4° (sensitivity: 86.1%, specificity: 81.5%). Postoperative changes in DOCL and CXA were more pronounced in irreducible group. The fusion rates were comparable in the 2 groups (92.6% vs. 94.4%, p=0.730).
Conclusion The reducibility-based posterior reduction fusion strategy achieves satisfactory clinical and radiological outcomes in the surgical management of AAD. For reducible cases, direct reduction under continuous intraoperative skull traction is preferred to minimize surgical trauma. In contrast, interfacet joints distraction and cage implantation are essential for irreducible cases. Preoperative OAAF may act as a potential predictor of reducibility.
Objective To quantify the effect of different hip positions on lumbar lordosis (LL) and spinopelvic parameters in the right lateral decubitus position (RLDP) and identify the configuration that most closely replicates physiologic standing alignment during lateral lumbar interbody fusion in minimally invasive spinal surgery.
Methods Thirty healthy volunteers (15 males, 15 females; mean age, 27.8±8.6 years) underwent lateral lumbar radiographs in standing position and 5 RLDP configurations: neutral hips (NN), 30° flexion of both hips (30FF), 30° flexion of the right hip with left hip neutral (30FN), 60° flexion of both hips (60FF), and 60° flexion of the right hip with left hip neutral (60FN). LL, pelvic tilt (PT), sacral slope (SS), and pelvic incidence (PI) were measured. Each position was compared to standing using paired t-tests. Intra- and interobserver reliability were evaluated using intraclass correlation coefficients (ICCs).
Results LL decreased significantly in all RLDP positions compared with standing (51.1°±3.8°). The 30FN position showed the smallest change (ΔLL=-4.9°, p<0.001), whereas 60FF showed the greatest (ΔLL=-15.0°, p<0.001). In 30FN, PT decreased (p=0.013) and SS increased (p=0.003), indicating mild anterior pelvic rotation. PI showed minimal variation across positions. Intra- and interobserver ICCs ranged from 0.92 to 0.99, confirming high measurement reliability.
Conclusion Hip position significantly influences lumbar and pelvic alignment in RLDP. Among tested configurations, the 30FN position (right hip flexed 30°, left neutral) showed the smallest numerical deviation from standing alignment and spinopelvic harmony relative to standing in RLDP.
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Reply Letter: Reconsidering Intraoperative Hip Positioning in Single-Position Lateral Lumbar Interbody Fusion – A Commentary on “Optimal Positioning for
Single-Position Lateral Lumbar Interbody Fusion” Worawat Limthongkul, Natavut Prasertkul, Pakawas Praisarnti, Maruay Tanayavong, Surachat Jaroenwareekul, Wicharn Yingsakmongkol, Weerasak Singhatanadgige, Vit Kotheeranurak Neurospine.2026; 23(3): 756. CrossRef
Reconsidering Intraoperative Hip Positioning in Single-Position Lateral Lumbar Interbody Fusion – A Commentary on “Optimal Positioning for Single-Position Lateral Lumbar Interbody Fusion” Jiayi Chen Neurospine.2026; 23(3): 754. CrossRef
Objective To evaluate long-term bone quality changes within the fusion construct (FC) after 2- to 3-level lumbar fusion using computed tomography (CT)-derived Hounsfield units (HUs).
Methods Among 520 screened patients, 222 who underwent 2- to 3-level posterior lumbar interbody fusion met the inclusion criteria. HU values were measured on CT scans preoperatively, at 1-year postoperative, and at final follow-up. The percentage change in HU (HU [final–pre]%) was calculated for each vertebral level.
Results At the final follow-up, the FC demonstrated a significant decline in HU compared to preoperative values (median [10th–90th percentile], 132.0 [86.5–220.4]; 95% confidence interval [CI], 116.0–142.5 vs. 124.5 [71.0– 210.0]; 109.8–135.1; HU (final–pre)%: -11.0 [-62.0 to 48.5]; -19.9 to -6.1; p<0.001). In contrast, HU increased significantly at the uppermost instrumented vertebra (HU (final–pre)%: median [10th–90th percentile], 28.3 [-19.9 to 102.9]; 95% CI, 21.1–36.4; p<0.001), likely reflecting increased mechanical demands. Subgroup analysis revealed a more pronounced decline in HU in patients with longer follow-up durations, particularly in the FC group (p=0.003).
Conclusion CT-derived HU revealed progressive trabecular bone loss within FC over time after lumbar fusion. In patients with longer postoperative intervals, clinicians should remain aware of the potential weakening of the FC, which has important implications when considering implant removal or planning revision surgery.
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A Commentary on “Disuse Bone Loss in Fusion Constructs After Multilevel Lumbar Fusion: A Computed Tomography Hounsfield Unit Analysis” Jiajun Deng, Hongsheng Lin Neurospine.2026; 23(2): 504. CrossRef
Reply Letter: A Commentary on “Disuse Bone Loss in Fusion Constructs After Multilevel Lumbar Fusion: A Computed Tomography Hounsfield Unit Analysis” Hyun-Jun Jang, Dongkyu Kim, Bong-Ju Moon, Kyung-Hyun Kim, Jeong-Yoon Park, Sung-Uk Kuh, Keun-Su Kim, Dong-Kyu Chin Neurospine.2026; 23(2): 506. CrossRef
Objective Transforaminal lumbar interbody fusion (TLIF) has become a mainstay technique for interbody fusion, allowing for large contact area between implant and endplate, and providing increased stability and greater area for fusion. The development of 3-dimensional (3D)-expandable implants that provide multidimensional (3D) expansion has shown to provide better height restoration and clinical outcomes when compared to static implants. Comparison of the endplate coverage between 3D-expandable and static TLIF implants has yet to be studied. This study compares endplate coverage achieved with static TLIF, 3D-expandable TLIF, and anterior lumbar interbody fusion (ALIF) implants.
Methods A retrospective review of patients undergoing interbody fusion with either static TLIF, 3D-expandable TLIF, or ALIF between the years 2014 and 2022 was conducted. Postoperative computed tomography (CT) imaging was used to measure endplate and implant dimensions. 3D-expandable TLIF interbody device areas were calculated using diameter measurements on postoperative CT. The coverage ratio was defined as the ratio of twice the area of the implant and the sum of the superior and inferior endplate areas at the operative level.
Results A total of 53 patients per cohort were included. The average endplate coverage ratios for static TLIF, 3D-expandable TLIF, and ALIF implants were 0.19±0.04, 0.35±0.06, and 0.46±0.13, respectively. Subgroup analysis showed comparable coverage of 3D-expandable TLIF to ALIF implants at L3–4 and L4–5, while ALIF remained superior at L5–S1.
Conclusion 3D-expandable TLIF interbody devices provide greater endplate coverage when compared to static TLIF devices and approach comparable coverage to ALIF implants.
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A Commentary on “Radiographic Analysis of Endplate Coverage of a 3-Dimensional-Expandable Transforaminal Lumbar Interbody Fusion (TLIF) Implant Compared to Static TLIF and Anterior Lumbar Interbody Fusion Implants” Kun Wang, Xiaofeng Lian Neurospine.2025; 22(4): 902. CrossRef
From the Editor-in-Chief: Featured Articles in the December 2025 Issue Inbo Han Neurospine.2025; 22(4): 877. CrossRef
Jun Jae Shin, Sun Joon Yoo, Se Jun Park, Dong Kyu Kim, Hyun Jun Jang, Bong Ju Moon, Kyung Hyun Kim, Jeong Yoon Park, Sung Uk Kuh, Dong Kyu Chin, Keun Su Kim, Yong Eun Cho, Chang Kyu Lee, Dong Ah Shin, Seong Yi, Keung Nyun Kim, Joongkyum Shin, Yoon Ha
Neurospine 2025;22(4):937-948. Published online December 31, 2025
Objective To evaluate the clinical significance of a negative K-line in the neck flexion position (FK-line [-]), which indicates that cervical ossification of the posterior longitudinal ligament (OPLL) crosses the K-line during flexion, and to compare surgical outcomes between laminoplasty (LP) and laminectomy with fusion (LF) for multilevel FK-line (-) cervical OPLL.
Methods A total of 349 patients with multiple cervical OPLL who underwent posterior decompression surgery (LP or LF) with a minimum of 2 years of follow-up were stratified by FK-line status. Clinical and radiological parameters were compared between the FK-line (+) and FK-line (-) groups. Subgroup analysis of FK-line (-) patients evaluated the efficacy of LP versus LF. Multivariate regression identified predictors of neurological recovery.
Results Patients with FK-line (-) OPLL exhibited a smaller FK-line distance, more kyphotic alignment, greater cervical flexion, and lower recovery ratios compared to those with FK-line (+). In the FK-line (-) subgroup, LF achieved a significantly greater increase in FK-line distance, better correction of the flexion angle, and more neurological recovery than LP. Multivariate analyses identified postoperative FK-line distance, C2–7 flexion angle, and preoperative dynamic extension reserve as independent predictors of neurological outcomes.
Conclusion FK-line status reflects the sagittal cord position and predicts surgical outcomes in cervical OPLL. In FK-line (-) patients, LF provides better neurological recovery and more effective posterior cord shift and kyphotic alignment correction than LP. Incorporating FK-line assessment to guide surgical planning could improve individualized treatment outcomes for multilevel OPLL.
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A Commentary on “Flexion K-Line Status Predicts Surgical Strategy in Multilevel Cervical Ossification of the Posterior Longitudinal Ligament: A Multicenter Comparison of Laminoplasty and Laminectomy With Fusion” John H. Chi Neurospine.2025; 22(4): 951. CrossRef
A Commentary on “Flexion K-Line Status Predicts Surgical Strategy in Multilevel Cervical Ossification of the Posterior Longitudinal Ligament: A Multicenter Comparison of Laminoplasty and Laminectomy With Fusion” Yutaro Kanda Neurospine.2025; 22(4): 949. CrossRef
From the Editor-in-Chief: Featured Articles in the December 2025 Issue Inbo Han Neurospine.2025; 22(4): 877. CrossRef
Objective To evaluate the biomechanical characteristics of 2 anterior fixation techniques (clival plate fixation [CPF], transoral atlantoaxial reduction plate [TARP]) versus posterior occipitocervical fixation (POCF) for basilar invagination with atlantoaxial dislocation (BI-AAD), under varying atlantoaxial lateral mass cage heights (4–10 mm).
Methods Seven fresh cadaveric specimens (occiput to C3, Oc–C3) were tested in the following conditions: (1) intact state; (2) BI-AAD state; (3) BI-AAD+CPF; (4) BI-AAD+TARP fixation; (5) BI-AAD+POCF. A pure 1.5 N·m moment loads to specimens in flexion/extension, lateral bending and axial rotation. Range of motion (ROM) and neutral zone (NZ) values at Oc–C2 were calculated and compared.
Results ROM of the C1–2 segment under the intact and BI-AAD states were as follows: 9.3°±4.6° versus 21.3°±8.3° in flexion, 4.6°±1.9° versus 9.3°±3.8° in extension, 3.6°±2.2° versus 12.0°±6.5° in lateral bending, and 68.9°±14.4° versus 76.6°±6.6° in axial rotation, respectively. Compared with BI-AAD states, all internal fixation techniques significantly reduced the ROM of the Oc–C2 segment. TARP fixation exhibited larger ROM in flexion-extension. While in lateral bending and axial rotation, the ROM values for the anterior plate constructs were smaller than that of POCF, with a statistically significant difference observed between CPF and POCF. Cage height variations showed no significant impact on overall biomechanical stability.
Conclusion Anterior plate fixation techniques demonstrated superior resistance to lateral bending and rotational forces compared to posterior approaches, with clival plate fixation exhibiting optimal biomechanical stability for BI-AAD. Variations in cage height exhibited negligible impact on stability when internal fixation achieved adequate rigidity.
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Reducibility-Based Posterior Reduction and Fusion Strategies for Atlantoaxial Dislocation: A Clinical and Radiological Study Guipeng Zhao, Haotian Long, Dingyu Du, Dean Chou, Longyi Chen, Junting Hu, Hailong Feng, Qidong Liu, Jinping Liu Neurospine.2026; 23(2): 411. CrossRef
Objective To elucidate the clinical outcomes of craniocervical realignment surgery in patients with craniovertebral junction (CVJ) kyphosis accompanied by negative sagittal imbalance, and to identify radiological predictors associated with favorable outcomes.
Methods A retrospective analysis was performed on 28 patients who underwent craniocervical realignment between 2014 and 2022 for CVJ kyphosis with accompanying negative sagittal imbalance. Clinical outcomes were evaluated using the Neck Disability Index (NDI), visual analogue scale for neck pain, and the Japanese Orthopaedic Association (JOA) score. Radiographic parameters included the C0–2 angle and the C2–7 sagittal vertical axis (SVA). Favorable outcomes were defined as an improvement of more than 20 points in the NDI and a JOA recovery rate exceeding 50%. Multiple linear regression and receiver operating characteristic (ROC) curve analyses were conducted to identify independent predictors and to determine optimal threshold values.
Results Significant improvements in both clinical outcomes and radiographic alignment were observed in association with craniocervical realignment surgery. Patients who achieved favorable outcomes exhibited greater postoperative changes in the C0–2 angle and the C2–7 SVA. Multivariate analysis identified changesm in the C0–2 angle (p=0.019) and C2–7 SVA (p=0.010) as independent predictors of NDI improvement, while age (p=0.033) and C2–7 SVA change (p=0.037) were independently associated with the JOA recovery rate. ROC curve analysis determined optimal cutoff values of ≥10.65° for C0–2 angle change and ≥19.2 mm for C2–7 SVA change, with corresponding area under the curve values of 0.872 and 0.802, respectively.
Conclusion Craniocervical realignment appears to be a viable surgical option for patients with CVJ kyphosis and negative sagittal imbalance. Postoperative changes in C0–2 angle and C2–7 SVA were found to be associated with favorable clinical and functional outcomes, suggesting their potential role as prognostic factors.
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Predictive value of C0–C2 and C1–C2 angles for postoperative lower cervical alignment following posterior atlantoaxial fixation and fusion: a retrospective single-center study Beiping OuYang, Hongyan Sun, Kaiwei Zhang, Li Zhang European Spine Journal.2026; 35(9): 5534. CrossRef
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