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
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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 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.
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 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
Objective Paravertebral foramen screws (PVFSs) have been developed for better pullout strength than lateral mass screws do and lower the risk of vertebral artery and nerve injury than do pedicle screws. While the original method involves insertion using lateral fluoroscopy, its reliability may be limited. This report is the first to assess the accuracy of PVFS insertion under navigation. Given the inherent inaccuracies associated with navigation systems, the authors propose and evaluate a novel stepwise method of inserting PVFSs, called stepwise PVFS with a focus on achieving the correct screw tip location for good cortical bone purchase.
Methods The authors conducted a retrospective analysis of 12 patients (78 screws) who underwent cervical spine fixation with stepwise PVFS under O-arm navigation between October 2022 and February 2024. The accuracy of screw placement was evaluated using postoperative computed tomography (CT) scans.
Results A total of 78 PVFSs were inserted in 5 men and 7 women, with an average age of 75 years (range, 52–85 years). The mean follow-up period was 471 days (range, 47–834 days). There were no adverse events related to screw insertion. Postoperative CT scans revealed that 70 screws (90%) were placed in the ideal position. Among the 8 screws that did not achieve the ideal position, 4 had lateral deviation (located in a lateral mass), whereas the other 4 were too short. There were no cases of screw loosening at the final follow-up.
Conclusion The present study demonstrates that the stepwise PVFS method under navigation guidance achieves higher accuracy in PVFS placement compared with conventional fluoroscopy-guided PVFS, as reported in previous studies.
Objective To assess the effectiveness of vertebral cement augmentation (VCA) at upper instrumented vertebra (UIV) and UIV+1 in preventing proximal junction complications in correction surgery for adult spinal deformity patients.
Methods A literature search was conducted on Web of Science, PubMed, and Cochrane Library databases for comparative studies published before December 30th, 2024. Two reviewers independently screened eligible articles based on the inclusion and exclusion criteria, assessed study quality with Newcastle-Ottawa scale, and extracted data like study characteristics, surgical details, primary and secondary outcomes. Data analysis was performed using Review Manager 5.4 and Stata software.
Results Of all 513 papers screened, a meta-analysis was conducted on 7 articles, which included 333 cases in the VCA group and 827 cases in the control group. Patients in the VCA group had significantly older age and lower T score than patients in the control group. Although there was no statistically significant difference in the incidence of proximal junctional failure between the 2 groups, the results of the meta-analysis showed that the incidence of proximal junctional failure and the need for revision surgery were reduced by 36% and 71%, respectively, in the VCA group. One study reported 2 clinically silent pulmonary cement embolism and 1 patient requiring surgical decompression for cement leak into the spinal canal.
Conclusion This meta-analysis supported the use of VCA in corrective surgery for spinal deformities patients, especially in patients with advanced age and osteoporosis.
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Proximal Junctional Kyphosis Prevention in Adult Spinal Deformity Surgery: A Technical Review of Tethering and Adjunctive Strategies Paritash Tahmasebpour, Pawel P. Jankowski, Jason Liang, Joshua Lin, Kyriakos D. Chatzis, Peter S. Tretiakov, Spencer Matthews, Louis Boissiere, John F. Burke, Christopher I. Shaffrey, Aaron Hockley, Peter Passias Operative Neurosurgery.2026;[Epub] CrossRef
Vertebral Cement Augmentation is Associated With Reduced Rates of Proximal Junctional Failure in Adult Spinal Deformity Surgery: A Systematic Review and Meta-Analysis of 1211 Patients Stavros Matsoukas, Shaan Patel, Pavlos Texakalidis, Teleale F. Gebeyehu, Joshua E. Heller, Jack Jallo, James S. Harrop, Srinivas K. Prasad Operative Neurosurgery.2025;[Epub] CrossRef
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Purpose To identify factors associated with adjacent-level ossification development (ALOD) after anterior cervical discectomy and fusion (ACDF) and associated clinical outcomes.
Methods We retrospectively reviewed records of 140 adults who underwent primary ACDF for degenerative disc disease. We compared patients with and without ALOD after ACDF. Radiographic measurements and factors associated with ALOD were assessed preoperatively and at minimum 24-month follow-up. Clinical outcomes were incidence of clinical adjacent-segment pathologies (CASP), revision surgery, and patient-reported outcomes.
Results Factors associated with both cranial and caudal ALOD were short plate-to-disc distance (PDD), adjacent-segment kyphosis, hyperlordotic ACDF causing junctional segment kyphosis, and preoperative ossification of the anterior longitudinal ligament (OALL). Mean final adjacent-segment range of motion (ROM) was less in those with cranial ALOD (6.9° ± 2.8°) than in those without cranial ALOD (12° ± 4.2°) (p < 0.01). Mean final adjacent-segment ROM was also less in those with caudal ALOD (5.5° ± 2.4º) than in those without caudal ALOD (8.2º ± 3.7º) (p < 0.01). The incidence of CASP-required surgery was higher in those with caudal ALOD (p = 0.02) but no different in those with cranial ALOD (p = 0.69) compared with those without ALOD.
Conclusion Factors associated with ALOD were a kyphotic segment adjacent to ACDF, hyperlordotic fusion, preoperative OALL, and short PDD. ALOD was associated with less segmental ROM and, for those with caudal but not cranial ALOD, higher incidence of revision surgery for CASP.
This video presents a case of L4–5 unstable spondylolisthesis treated with full-endoscopic transforaminal lumbar interbody fusion (Endo-TLIF), emphasizing the GUARD (Glider Used as a Rotary Device) technique for nerve root protection. This innovative approach involves controlled rotation of the cage glider before cage insertion to minimize the risk of nerve root injury, a significant complication in Endo-TLIF procedures. The GUARD technique, validated in previous cadaveric studies, provides enhanced safety during cage insertion by protecting the nerve root. A 48-year-old woman with a 3-year history of progressive low back pain and bilateral lower extremity radiculopathy (right-sided predominance) was diagnosed with L4–5 unstable spondylolisthesis and spinal stenosis. After failure of conservative management, she underwent uniportal full-endoscopic facet-resecting transforaminal lumbar interbody fusion using the GUARD technique. Postoperatively, the patient experienced significant symptomatic improvement and resolution of radiculopathy, without any intraoperative nerve root injury or postoperative neurological deficits. This case demonstrates the effectiveness of the GUARD technique in reducing neurological complications and improving patient outcomes.
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This article aims to introduce a novel full-endoscopic anterior cervical discectomy and fusion (ACDF) procedure to treat cervical myelopathy. Adoption of endoscopic anterior cervical procedures has been lagging due to safety concerns and the necessity of placing an interbody cage. We have developed novel instrumentation and a modified percutaneous anterior cervical approach that allows a safe and reproducible full-endoscopic ACDF. Specially designed retractor blades facilitate percutaneous placement of a zero-profile cervical interbody cage. A 64-year-old male patient presents with chronic neck pain and bilateral paresthesia in his upper extremities, mild ataxia, and positive Hoffmann sign. He has a history of deep vein thrombosis 5 years prior. Preoperative magnetic resonance imaging and computed tomography scans show a degenerated disk, severe central canal stenosis with cord compression and a hyperintense cord signal at C5–6, compatible with cervical myelopathy. An electromyography of upper extrimities shows suspicion of myelopathy at C5–6. Full-endoscopic ACDF was performed at C5–6 to decompress the canal and restore disk height with a zero-profile interbody cage. Postoperatively the patient showed improvement of his symptoms with reduced pain and disability scores and was discharged from the hospital within 24 hours of the surgery. Outcome is satisfactory at 2-year postoperative follow-up. Full-endoscopic ACDF enables excellent visualization of the posterior endplates and cervical canal with constant irrigation, facilitating treatment of cervical myelopathy. No retraction is required during discectomy and decompression, decreasing the risk of postoperative dysphagia, hoarseness and bleeding. A zero-profile interbody cage can be percutaneously placed with special retractor blades.
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Objective The cervical spine presents challenges in treating metastatic cervical spinal tumors (MCSTs). Although the efficacy of cervical pedicle screw placement (CPS) has been well established, its use in combination with 5.5-mm rods for MCST has not been reported. This study aimed to evaluate the efficacy of CPS combined with 5.5-mm rods in treating MCST and compare it with that of CPS combined with traditional 3.5-mm rods.
Methods This retrospective study analyzed 58 patients with MCST who underwent posterior cervical spinal fusion surgery by a single surgeon between March 2012 and December 2022. Data included demographics, surgical details, imaging results, numerical rating scale score for neck pain, Eastern Cooperative Oncology Group performance status, and Spine Oncology Study Group Outcomes Questionnaire responses.
Results Preoperative Spinal Instability Neoplastic Scores were significantly higher in the 5.5-mm rod group. Greater kyphotic changes in the index vertebra were observed in the 3.5-mm rod group. Neck pain reduction was significantly better in the 5.5-mm rod group.
Conclusion CPS with 5.5-mm rods provides superior biomechanical stability and effectively resists forward bending momentum in posterior MCST fusion surgery. These findings support the use of 5.5-mm rods to enhance surgical outcomes.
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Objective Achieving successful fusion during spine surgery is dependent on rigid pedicle screw fixation. To assess fixation strength, the insertional torque can be measured during intraoperative screw fixation. This study aimed to explore the technical feasibility of measuring the insertional torque of a pedicle screw, while investigating its relationship with bone density.
Methods Thoraco-lumbar screw fixation fusion surgery was performed on 53 patients (mean age, 65.5 ± 9.8 years). The insertional torque of 284 screws was measured at the point passing through the pedicle using a calibrated torque wrench, with a specially designed connector to the spine screw system. The Hounsfield units (HU) value was determined by assessing the trabecular portion of the index vertebral body on sagittal computed tomography images. We analyzed the relationship between the measured insertional torque and the following bone strength parameters: bone mineral density (BMD) and HU of the vertebral body.
Results The mean insertion torque was 105.55 ± 58.08 N∙cm and T-score value (BMD) was -1.14 ± 1.49. Mean HU value was 136.37 ± 57.59. Screw insertion torque was positively correlated with BMD and HU in whole patients. However, in cases of osteopenia, all variables showed very weak correlations with insertional torque. In patients with osteoporosis, there was no statistically significant correlation between BMD and torque strength; HU showed a significant correlation.
Conclusion The insertional torque of screw fixation significantly correlated with bone density (BMD and HU). HU measurements showed greater clinical significance than did BMD values in patients with osteoporosis.
Citations
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