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.
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.
The atlantoaxial (C1–2) junction is among the most technically demanding regions for cervical spine surgery owing to its complex osseoligamentous anatomy and proximity to critical neurovascular structures. Numerous posterior fixation constructs have been developed to optimize biomechanical rigidity and promote arthrodesis. Since Gallie’s introduction of posterior wiring with autologous bone grafts in 1939, evolving techniques have focused on enhancing fusion rates while minimizing risk to adjacent structures. This paper outlines the historical evolution of C1–2 posterior instrumentation, current fixation strategies, bone fusion techniques, and reduction methods. A systematic literature search identified 61 relevant studies on C1–2 fusion. Additional references were manually reviewed to provide a comprehensive context. Of these, 41 studies were narratively summarized to outline the historical and conceptual evolution of C1–2 fusion techniques, while the remaining 20 post-2000 studies on contemporary surgical modifications were systematically reviewed and tabulated for technical details and clinical outcomes. C1–2 fusion techniques have evolved significantly over time. Early methods primarily involved posterior wiring with autologous bone grafts, but later transitioned to rigid segmental fixation using pedicle screw constructs, resulting in improved fusion rates and clinical outcomes. Interarticular fusion, when concurrently performed, enhances the biological fusion environment, contributing to favorable clinical results. C1 lateral mass, posterior arch, pedicle screws and C2 pedicle, lamina screws give us much stronger stability and higher fusion rates. Interarticular fusion using local bone also gives us technical easiness guaranteeing high fusion rate overcoming inconvenience of wiring and iliac bone harvest. Interarticular height reduction and interarticular fusion should be discriminated.
Objective Spinal fusion surgery is effective for treating various adult spinal deformities. However, spinal fusion surgery is associated with the risk of adjacent segment disease (ASD; 5%–30%), particularly proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). Proximal junctional tethering (PJT) has become a popular technique owing to increasing evidence that it can decrease the rate of PJK or PJF.
Methods A literature search was conducted using PubMed, Embase, and Cochrane Library. Twelve eligible studies were identified. These studies were predominantly retrospective in nature and compared the incidence of PJK or PJF in adults undergoing spinal fusion surgery with or without PJT. Risk of bias was assessed using the Newcastle-Ottawa scale. All outcomes were analyzed using R software (ver. 4.4.1).
Results We included 8 retrospective cohort studies and 3 propensity-score-matched analyses; these studies comprised 1,424 patients. PJT was associated with a significant decrease in the odds of development of PJK (odds ratio [OR], 0.44; 95% confidence interval [CI], 0.27–0.71) and PJF (OR, 0.36; 95% CI, 0.19–0.69) compared with control. Subgroup analysis results revealed no significant difference in ASD rates between geographical locations, between tethering with and without crosslinks, and between specific tethering techniques.
Conclusion PJT significantly reduces the odds of both PJK and PJF in adults undergoing spinal fusion surgery.
Objective Anterior odontoid screw fixation (AOSF) has several advantages over posterior C1–2 fusion for Grauer type II and shallow type III odontoid fractures. However, the risk factors for fusion failure, particularly in terms of 3-dimensional (3D) measurements, remain unclear. This study investigated the impact of fracture deficit volume (FDV), a novel 3D measurement, on fusion outcomes in patients undergoing AOSF.
Methods We enrolled 44 patients with Grauer type II or shallow type III odontoid fractures treated with AOSF at a single institution. Radiological assessments included preoperative and postoperative measurements of the fracture gap and fracture displacement on computed tomography (CT) scans. FDV was calculated through 3D CT reconstruction of preoperative and immediate postoperative CT to quantify the spatial gap between the edges of the fractures. Fusion outcomes were defined as solid union, fibrous union, or nonunion. Logistic regression and a generalized additive model (GAM) were used to identify risk factors for fusion failure after AOSF.
Results Solid fusion was achieved in 77.3% of patients. A reduction in the FDV with respect to the preoperative value was significantly associated with successful fusion (p=0.028), whereas patients presenting an increased FDV postoperatively were more likely to exhibit fusion failure (p=0.006). Age≥65 years, a fracture gap≥2 mm, and an increased FDV postoperatively were significant risk factors for fusion failure. GAM analysis revealed a linear relationship between a reduced FDV and improved fusion rates (adjusted R2=0.186, p=0.018).
Conclusion The risk of fusion failure is greater in elderly patients, those with a fracture gap greater than 2 mm, and those with an increased FDV postoperatively. Among the modifiable risk factors, FDV had the greatest impact on fusion outcomes after AOSF.
Objective Retro-odontoid pseudotumor (ROP) is a nonneoplastic mass associated with atlantoaxial instability (AAI). This study compared ROP-positive and ROP-negative AAI patients and evaluated cystic versus granulation-type ROP regarding regression patterns and surgical outcomes.
Methods We retrospectively analyzed 112 AAI patients who underwent pre- and postoperative imaging and clinical evaluations. Patients were classified as ROP-positive or ROP-negative, with ROP-positive cases further categorized as cystic or granulation-type. Imaging parameters—including atlantodental interval (ADI), ΔADI, and cervical range of motion (ROM) were compared along with regression time and postoperative outcomes.
Results Among 112 patients, 57 (50.9%) had ROP. The ROP-positive group was older (67.37±13.13 years vs. 56.90±15.15 years, p<0.001) and had lower ADI (5.63±2.77 mm vs. 6.99±2.33 mm, p=0.034), ΔADI (3.01±2.27 mm vs. 3.89±2.07 mm, p=0.006), and C2–7 ROM (30.78°±15.45° vs. 41.73°±16.58°, p<0.001). In ROP subgroups, the cystic group had greater C1–2 ROM (15.69°±6.34° vs. 10.00°±7.72°, p=0.013) and ADI (6.98±2.68 mm vs. 5.14±2.66 mm, p=0.042). Immediate postoperative ROP thickness remained greater in the cystic group (6.85±2.49 vs. 5.21±1.82 mm, p=0.042), while ROP thickness at 3 months and 1 year showed no significant differences. JOA recovery rates were similar.
Conclusion This study demonstrates that ROP-positive AAI patients exhibit distinct radiological characteristics, with reduced cervical mobility. Furthermore, cystic ROP shows delayed regression following posterior fusion. These findings underscore the importance of ROP subtypes in surgical planning, requiring closer monitoring and possibly earlier intervention.
Objective To develop a pedicle screw for posterior spinal fixation using this long fiber carbon fiber reinforced plastic (CFRP) technology and evaluate its strength and radiolucency compared with titanium (Ti)-alloy screws.
Methods In this preclinical study, the shear strength, torsional strength, loosening resistance, and image evaluation of long fiber type CFRP pedicle screws and Ti-alloy screws were compared. A series of tests was conducted for future clinical-use approval.
Results The long fiber type CFRP pedicle screw (mean±standard deviation: 11,377.7±245.1 N) had superior shear strength compared to the Ti-alloy pedicle screw (10,300.3±249.7 N). The long fiber type CFRP pedicle screw (4.4±0.5 Nm) had inferior torsional strength compared to the Ti-alloy pedicle screw (22.4±0.6 Nm), although it could withstand twice the maximum load applied during surgery, suggesting that this will not be a clinical concern. In terms of loosening resistance, maximum torque values of the long fiber type CFRP pedicle screw and Ti-alloy pedicle screw were 0.99±0.08 and 0.75±0.05 Nm, respectively. The long fiber type CFRP pedicle screw was significantly more resistant to loosening than the Ti-alloy pedicle screw. Moreover, artifacts in the radiographic images were smaller than those observed for the Ti alloy. Biosafety and magnetic resonance safety tests also yielded satisfactory results, supporting approval of the long fiber CFRP pedicle screws for clinical use.
Conclusion Compared to existing Ti-alloy screws, the long fiber type CFRP pedicle screw with innovative manufacturing technology has sufficient performance for clinical use, and its use may make spinal surgery safer and more effective.
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Biomechanical stability and pedicle screw loosening Chenxi Cui, Haisheng Yang Journal of Biomechanics.2026; 197: 113174. CrossRef
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