Introduction: This study aimed to compare the outcomes in patients who received non-steroidal anti-inflammatory drugs (NSAIDs) ≤90 days or 90 days-1 year after posterior cervical fusion (PCF) with those in patients who did not receive NSAIDs after surgery.

Methods: Using the MarketScan^® Research Databases, we analyzed adults (18-90 years) who underwent PCF and adjusted for confounders with inverse probability of treatment weighting (IPTW) to compare outcomes in those receiving NSAIDs ≤90 days or 90 days-1 year after surgery and those not receiving NSAIDs within a year. In one analysis, we included single- and multi-level PCF, and in a sub-group analysis, we focused on single-level PCF. Outcomes included 30-day readmissions, pseudoarthrosis, hardware failure, and wound complications.

Results: After IPTW, NSAID use ≤90 days of single- and multi-level PCF was not associated with increased readmissions, pseudoarthrosis, or wound complications. However, NSAID use 90 days-1 year increased the odds of pseudoarthrosis and hardware failure (odds ratio 1.157, 95% confidence interval 1.075-1.245, p<0.001). In single-level PCF, NSAIDs use ≤90 days or 90 days-1 year of surgery was not associated with increased odds of complications. No difference was observed in postoperative complications between patients who took COX-2 selective inhibitors and those who took non-selective NSAIDs.

Conclusions: NSAID use ≤90 days of surgery does not increase the risk of adverse outcomes for either single- or multi-level PCF, suggesting it may be a viable option for pain management. Postoperative NSAID use 90 days-1 year does not seem to increase complications in single-level PCF. However, caution is advised for multi-level fusions or cases with complex clinical factors, in which NSAID use from 90 days-1-year postoperatively may increase the risk of pseudoarthrosis and hardware failure.

Introduction: Total disc replacement (TDR) using Mobi-C^® and Prestige LP^® was approved in Japan in 2017. To ensure effective surgical outcomes with TDR, the Japanese TDR guideline was established before its clinical use, and a registry system was developed to monitor the safety of early cases in Japan. This study assessed complications associated with TDR during the early post-approval period using this nationwide registry to evaluate the short-term safety of single-level TDR.

Methods: Data from the nationwide registry covering postoperative 2-year surveillance were analyzed for single-level TDR performed during the post-marketing surveillance period in Japan. The database included patient characteristics, surgical details, complications, and reoperations. Complication and reoperation rates were analyzed for the perioperative period during hospitalization and the postoperative period after discharge.

Results: In total, 332 patients were enrolled in this study, and 271 patients completed the 2-year follow-up (81.6%). Mobi-C^® and Prestige LP^® were used in 158 and 113 patients, respectively. Perioperative complications included hematoma (n=3) and airway obstruction (n=1). Three (1.1%) patients with hematoma underwent reoperation in the perioperative period during hospitalization. Overall, 20 (7.4%) patients experienced complications after discharge up to 2 years postoperatively, including recurrences of neurological symptoms (n=9), implant migration (n=2), implant subsidence (n=7), and others (n=3). Two (0.7%) patients who experienced a recurrence of neurological symptoms underwent additional posterior foraminotomy within 2 years postoperatively. One (0.4%) patient underwent implant removal and conversion to fusion due to implant subsidence.

Conclusions: The overall complication and reoperation rates of TDR were relatively low: 1.5% and 1.1% in the perioperative period during hospitalization and 7.4% and 1.1% within the 2-year postoperative period after discharge, respectively. TDR achieved favorable outcomes with acceptable complication rates when performed under appropriate surgical indications.

Introduction: In dropped head syndrome (DHS), the factors contributing to the prognosis due to conservative treatment have been unclear. The purpose of this study was to investigate the effect of spinal malalignment due to pre-existing thoracolumbar vertebral fractures on the improvement rate of conservative treatment of DHS.

Methods: Overall, 90 patients with DHS who visited our hospital and underwent conservative treatment for 6 months were included in the study. Patients were divided into 2 groups, Group F with and Group N without thoracolumbar vertebral fracture, and their improvement rate and spinal parameters were compared and statistically examined.

Results: Group F had a significantly larger sagittal vertical axis (SVA) and pelvic incidence minus lumbar lordosis (PI-LL). Cervicothoracic spine alignment did not differ between Groups F and N. The improvement rate of Group F was significantly lower than that of Group N (Group F: 18.8%, Group N: 54.1%).

Conclusions: DHS with thoracolumbar vertebral fracture has significantly large SVA and PI-LL, which would be a poor prognostic factor of conservative treatment.

Introduction: Degenerative cervical spondylolisthesis is associated with aging, neck pain, and myelopathy. While anterior spondylolisthesis (AS) has been extensively studied in relation to cervical sagittal parameters, posterior spondylolisthesis (PS) remains poorly understood despite its potential to cause myelopathy. This study investigates the association between PS and cervical sagittal parameters to elucidate its pathophysiology.

Methods: This retrospective study included 169 patients who underwent cervical spine surgery to treat cervical myelopathy, classified into 3 groups: PS, AS, and a control group without spondylolisthesis. Variables assessed included age, sex, body mass index, smoking history, T1 slope, sagittal vertical axis C2-C7 (SVA C2-C7), C2-C7 angle, C2-C7 range of motion, C1-C2 angle, and cervical disk degeneration (summed Pfirrmann grades). Logistic regression analysis was conducted to identify factors significantly associated with PS, and comparisons were made between the PS and AS groups.

Results: Of the 169 participants, 58 had PS, 22 had AS, and 89 formed the control group. A T1 slope ≥29° was significantly associated with PS (odds ratio: 1.090, p=0.005). PS was more common in younger men with mild disk degeneration, while AS was more frequent in older women with severe disk degeneration. Patients with PS exhibited larger C2-C7 angles and smaller SVA C2-C7 compared to those with AS. A high T1 slope appeared to induce a compensatory increase in the C2-C7 angle, generating posterior shear force that may have contributed to the development of PS.

Conclusions: A T1 slope of ≥29° was associated with PS. Our findings suggest that a compensatory mechanism related to a high T1 slope may play a role in the pathophysiology of PS, providing new insights into its development in cervical spinal disorders.

Introduction: Cervical spinal cord injury (CSCI) without major bone injury is increasing among older adults, particularly in aging societies like Japan. The optimal treatment strategies remain unclear, with conservative therapy often preferred, especially for older patients. However, surgery is frequently necessary due to poor improvement or progression of paralysis during conservative treatment. This study investigated the characteristics and outcomes of older patients with CSCI without major bone injury who transitioned from conservative treatment to surgery.

Methods: This nationwide, retrospective study examined data from patients aged ≥65 years with CSCI without major bone injury. The patients were categorized into 3 groups: conservative treatment, planned surgery, and those who switched from conservative treatment to surgery. The study aimed to identify the risk factors for conservative therapy failure that necessitate surgical intervention and to compare the outcomes between patients who had planned surgery and those who required surgery after conservative management failed.

Results: Among 615 patients, 422 (68.6%) received conservative treatment, 193 (31.4%) had planned surgery, and 116 (18.9%) transitioned from conservative to surgical treatment. Transition to surgery was mainly due to poor improvement or progression of neurological deficits. Significant risk factors for transitioning to surgery included younger age, presence of ossification of the posterior longitudinal ligament, and spinal cord signal changes on magnetic resonance imaging. Comparative analysis showed no significant differences in neurological outcomes between patients who had surgery as planned and those who required surgery after failed conservative treatment.

Conclusions: A significant proportion of older patients with CSCI without major bone injury who were initially managed conservatively eventually required surgery due to insufficient neurological improvement. The outcomes of patients who transitioned to surgery were similar to those who had surgery as initially planned, indicating that careful monitoring of conservative treatment followed by surgery, if necessary, may be an effective approach.

Introduction: This study investigated brace treatment for patients with adolescent idiopathic scoliosis (AIS) to comprehensively evaluate the factors associated with curve progression, including the effects of in-brace correction rate (ICR) and objective brace compliance. Additionally, it aimed to establish a clinically useful optimal ICR threshold for effective curve progression control.

Methods: In this single-center retrospective analysis of prospectively collected data, 116 patients with AIS, with Cobb angles of 20°-40° and at least 1-year follow-up were included. Patients whose Cobb angles progressed by >5° were classified into the progressed group, whereas the others were categorized into the non-progressed group. Bracing time was objectively assessed using a thermometer.

Results: In this study, 19 (16.4%) patients were assigned to the progressed group. Open triradiate cartilage was significantly more frequent in the progressed group (22.2% vs. 2.6%, p=0.011) whereas no significant differences were observed in demographics or pre-brace Cobb angles. The progressed group demonstrated a lower ICR (26.8% vs. 39.5%, p=0.002) and shorter bracing time at 6 months (14.0 hours vs. 17.4 hours, p=0.042). Multivariate logistic regression analysis revealed that Sanders grade (1-4), ICR, and bracing time were independently associated with Cobb angle progression (odds ratios: 7.01, 0.95, and 0.89, respectively; all p<0.05). Based on receiver operating characteristic curve analysis, the ICR threshold of 38.3% was identified to achieve a clinically significant negative predictive value of 95%.

Conclusions: Under objective bracing time monitoring, skeletal maturity, ICR, and bracing time were crucial factors in preventing curve progression 1 year after brace initiation in patients with Cobb angles of 20°-40°. An ICR of 38.3% is recommended as the target when bracing adjustments are feasible.

Introduction: Low bone mineral density (BMD), a history of vertebral fractures (VFs), and steroid use are established risk factors for VFs. Additionally, age, nutritional status, muscle mass, and spinal sagittal alignment have been linked to osteoporosis and fractures. This study aims to investigate the risk factors contributing to new occurrences of VFs.

Methods: We included 597 patients with osteoporosis who visited our outpatient department and were available for follow-up 1 year after the visit. The following data were collected: age at examination, presence of secondary osteoporosis, body mass index, lumbar spine BMD, femoral neck BMD, number of VFs, grip strength, trunk muscle mass, controlling nutritional status (CONUT) score, sagittal vertical axis (SVA), pelvic tilt, pelvic incidence-lumbar lordosis, thoracic kyphosis on whole-spine standing radiography, and osteoporosis treatment status at baseline. Patients who had new VFs confirmed on whole-spine standing radiography at the 1-year follow-up visit were included in the group with new VF occurrence. We performed between-group comparisons of each parameter. Additionally, to identify risk factors for new VFs, we conducted a multivariate analysis using the presence of new VFs as the dependent variable.

Results: A total of 60 new VFs occurred during the 1-year period, representing 10.1% of the study population. When comparing the new VF incidence group with the non-incidence group, the CONUT score and SVA were significantly higher in the new VF incidence group. There were no significant differences between the 2 groups for the other variables. Multiple logistic regression analysis indicated that both a high CONUT score and SVA were independent risk factors for the occurrence of new VFs.

Conclusions: The 1-year incidence of new VFs was 10.1% among patients with osteoporosis, despite appropriate osteoporosis treatment. These patients also exhibited malnutrition and spinal sagittal malalignment at baseline. Our findings suggest that malnutrition and spinal sagittal malalignment may be independent risk factors for the occurrence of new VFs.

Introduction: The geriatric nutritional risk index (GNRI) has emerged as a useful predictor of surgical risk and postoperative outcomes. This study aimed to explore the utility of GNRI as a semiquantitative tool for predicting systemic and local complications after multilevel thoracolumbar fusion surgery in older patients and to evaluate the broader implications of nutritional status on postoperative recovery and independence.

Methods: This multicenter study included 249 patients aged 65 years or older who underwent thoracolumbar fusion of at least four vertebrae. The nutrition-related risk grades were defined by the GNRI values, and the patients were divided into four groups: risk absent (GNRI >98), low risk (GNRI 92 to ≤98), moderate risk (GNRI 82 to <92), and major risk (GNRI <82). The occurrence of systemic complications, surgical site infection (SSI), length of stay in the hospital, place of discharge, and occurrence of proximal junctional kyphosis or failure (PJK/PJF) within 2 years after surgery were examined.

Results: The risk-absent group consisted of 165 patients, the low-risk group of 40, the moderate-risk group of 36, and the major-risk group of eight. The incidence of any systemic complications (p=0.016), PJK/PJF (p<0.001), and hospital stay (p=0.028) significantly increased with worsening GNRI. Furthermore, the number of patients who were discharged home significantly decreased as GNRI worsened (p<0.001). SSI occurred most frequently in the risk-absent group (4.2%).

Conclusions: The GNRI serves as a semiquantitative assessment tool that enables the identification of high-risk patients who may benefit from preoperative nutritional interventions.

Introduction: Accurate pedicle screw placement is critical in spinal fusion surgery to prevent complications such as neurological and vascular injuries. While conventional intraoperative computed tomography (iCT) navigation systems enhance placement accuracy and reduce radiation exposure compared to fluoroscopic guidance, they can encounter line-of-sight issues that disrupt surgical workflows. The NextAR iCT navigation system aims to overcome these challenges by integrating an infrared camera directly onto surgical instruments, streamlining navigation and improving procedural efficiency.

Methods: This retrospective study evaluated the accuracy and safety of pedicle screw insertion using the NextAR navigation system in lumbar spinal fusion for degenerative diseases. We analyzed 307 screws using a CT-based grading system.

Results: Among the 307 screws inserted, only 8 (2.6%) exhibited minor deviations (grade 1 or 2), with no severe perforations (grade 3 or 4). There were no neurological or vascular complications related to screw placement. The NextAR system enabled precise pedicle screw insertion without the need for fluoroscopic guidance, eliminating radiation exposure for the surgical team.

Conclusions: The NextAR navigation system demonstrated high accuracy and safety in pedicle screw placement for lumbar degenerative diseases. By addressing line-of-sight issues inherent in traditional navigation systems and eliminating intraoperative radiation exposure, it offers significant procedural advantages. Further randomized controlled trials are needed to compare its effectiveness with other advanced navigation systems.

Introduction: To predict the onset of dysphagia in hospitalized patients with osteoporotic vertebral fractures (OVF) early after admission and to investigate cutoff values for risk factors.

Methods: The subjects were 341 hospitalized patients with OVF. We excluded 30 cases as the required data could not be measured, and 25 cases with conditions that could contribute to dysphagia, such as neurological or respiratory comorbidities. Gender, age, number and level of OVF, collapse rate (CR) of OVF, thoracolumbar kyphosis angle (KA), bone mineral density (BMD), systemic skeletal muscle mass index (SMI), and body mass index (BMI) were examined by dividing the patients into those with dysphagia (the P group) and others (the N group).

Results: There were 26 cases in the P group and 260 cases in the N group, with no significant difference in the male-female ratio, number, and level of OVF. The mean values of CR (%), KA in the P group/the N group were 40.0/36.1, 16.7/17.8, and the mean values of age, BMD (%), SMI (kg/m²), and BMI (kg/m²) in the P group/the N group were 86.4/82.3, 64.5/71.6, 4.43/5.58, 20.0/22.1 in men, 85.7/83.4, 55.1/63.8, 4.43/4.99, 19.4/21.6 in women, with significant differences in SMI in men and women and BMD in women. Analysis of SMI and BMD in women using a multivariate logistic model with dysphagia as the dependent variable showed that low SMI was an independent risk factor. The cutoff value, sensitivity, specificity, and area under the receiver operating characteristic curve for SMI were calculated. For men, the values were 4.610 kg/m², 0.867, 0.750, and 0.829, respectively, and for women, 4.410 kg/m², 0.790, 0.571, and 0.687, respectively.

Conclusions: A correlation was found between dysphagia and SMI in patients with OVF. For patients with SMI below the cutoff value, early swallowing evaluation and training intervention are considered important.

Introduction: Diffuse idiopathic skeletal hyperostosis (DISH) -related fractures have a high frequency of delayed diagnosis and paralysis even if caused by low-energy trauma, which makes diagnosing vertebral fractures (VFs) with DISH challenging. This study compared the clinical and radiologic features of VFs with DISH.

Methods: This study included 252 patients (70 men and 182 women; mean age±standard deviation, 81.0±8.6 years) with VFs in this study. Patients were divided into two groups depending on DISH (group D) or not (group N). We measured the sex, age, body mass index, hemoglobin A1c, and bone mineral density. This study also measured the spinopelvic sagittal alignments, local angular motion, inflection point, number of VFs, intervertebral disk (IVD) injury, and signal changes on magnetic resonance image (MRI).

Results: The presence of DISH in VFs was identified in 104 patients (41.3%) (49/70 [70.0%] in men vs. 55/182 [30.2%] in women). Group D was related to male sex, older age, larger thoracic kyphosis, VF at lower lumbar lesion, number of VFs, IVD injury, inflection point at lower lumbar, local angular motion, diffuse low signals on T1 MRI, and high or diffuse low signals on T2 MRI on univariant analysis. Multiple logistic regression analysis showed that the predictive factors for DISH were male sex, angular motion, VF at lower lumbar lesion, IVD injury, inflection point at lower lumbar, and diffuse low signals on T1 MRI.

Conclusions: DISH was related to IVD injury, angular motion, and diffuse low signals on T1 MRI. In addition, VFs with DISH were more frequently found in men at the lower lumbar lesion than in women at thoracolumbar. When physicians detect these factors, attention should be given to VFs with DISH, and whole-spine computed tomography should be considered not to overlook the presence of DISH.

Introduction: We evaluated the effect of 3 high-angle cages on spinal alignment and clinical outcomes following posterior lumbar interbody fusion (PLIF).

Methods: A retrospective analysis was performed on 104 patients who underwent PLIF at the L4/5 level between January 2021 and August 2023. Patients were divided into 3 groups: 12° (L), 16° (M), and 22° (H) cage groups. Lumbar spine radiographs were taken preoperatively and one year postoperatively to assess slip rate (% slip), segmental lumbar lordosis (SLL), segmental intervertebral angle (SIA), lumbar lordosis (LL), pelvic incidence-LL, sagittal vertical axis (SVA), Japanese Orthopedic Association score, and lower back pain visual analog scale score. Bone union and cage subsidence rates were evaluated using computed tomography 6 months postoperatively. Statistical analyses were performed using either the Wilcoxon signed rank test, Kruskal-Wallis test, or z-test.

Results: Intragroup analysis showed significant improvements in local alignment, with notable SVA improvement in the H group. Intergroup comparisons revealed no significant differences in preoperative evaluation items. Postoperatively, the H group showed significantly greater improvements in SLL and SIA than the L group. Although no significant difference was observed in bone union, the cage subsidence rate was significantly higher in the H group than in other groups.

Conclusions: PLIF using high-angle cages (≥12°) significantly improved local alignment in all groups. The 22° cage showed greater improvements in SLL and SIA but a higher incidence of cage subsidence. No significant clinical differences were observed between groups. LL in the lower lumbar spine can be achieved relatively easily using a cage with a larger angle in PLIF. However, although a cage with a larger angle may be advantageous for lordosis formation, postoperative clinical outcomes do not differ; therefore, cage selection should consider the surgeon's skill and patient factors, such as the degree of preoperative lumbar disc degeneration, instability, and alignment.

Introduction: Awareness of the harmful effects of long-term low-dose radiation is increasing. There are few comprehensive reports that accurately evaluate the radiation exposure dose to spinal interventionalists during selective nerve root block (SNRB). The purpose of this study was to evaluate the radiation exposure doses from C-arm fluoroscopy to different body areas of the interventionalist and to assess the effectiveness of lead-equivalent protective gear in reducing radiation exposure during SNRB.

Methods: Seven fresh cadavers were irradiated for 1 and 3 minutes using C-arm fluoroscopy to stimulate the real clinical setting of SNRB. The X-ray source was positioned both under and over the table. Radiation exposure doses were measured using real-time dosimeters. Lead-equivalent protective gear was placed on each body part (crystalline lens, thyroid gland, chest, non-dominant hand, dominant hand, gonads, and foot).

Results: Scatter radiation exposure doses to the upper body of the interventionalist were much higher when the X-ray source was positioned over the table compared to when it was positioned under the table. Use of X-ray protective gear reduced radiation exposure to the interventionalist regardless of the X-ray source position. The direct radiation dose to the hand in the irradiated field was extremely high when the X-ray source was positioned over the table—approximately 85 times higher than when under the table. Notably, hand doses remained extremely high even when the interventionalist wore protective gloves, although X-ray-protective-gear reduced overall radiation exposure.

Conclusions: This is the first report to quantify both scattered and direct radiation doses to each body part, as well as the reduction effect of using X-ray protective gear, in detail using fresh cadavers instead of patients. Spinal interventionalists should preferentially use an under-table X-ray source during SNRB and should consistently wear adequate X-ray-protective gear to minimize occupational radiation exposure.

Introduction: Herniated lumbar intervertebral discs migrate into the rostral or caudal anterior epidural space (AES). Previous studies have reported varying frequencies of migration direction, and the factors influencing the migration direction include patient age, affected disc level, and AES structural differences. However, the relationship between AES volume and migration direction remains unclarified. The purpose of this study was to measure the AES volume using computed tomography (CT) imaging and investigate the factors affecting herniated nucleus pulposus (HNP) migration in the sagittal direction.

Methods: We reviewed 42 patients who were surgically treated for migrated lumbar intervertebral disc herniation between 2014 and 2023. The primary endpoint was the ratio of the AES volume between vertebrae adjacent to the herniated disc. The secondary endpoints were patient demographics, disc level, clinical symptoms, disc degeneration, and lumbar instability. AES volume was measured by calculating the area between the posterior vertebral wall concavity and a line connecting the posterior walls on CT images, with the total volume determined as the sum of the slice areas multiplied by the slice width.

Results: A total of 14 patients exhibited rostral HNP migration, while 28 exhibited caudal HNP migration. Rostral HNP migration was associated with a higher prevalence of double-root involvement (p<0.05) and a greater superior/inferior ratio of the AES volume (p<0.01). Multivariate analysis identified the AES volume superior/inferior ratio (odds ratio: 9.551) as a factor significantly associated with the direction of HNP migration.

Conclusions: The HNP tends to migrate toward the direction with a larger AES volume because the herniated material follows the path of least resistance. Clinical presentation of double-root symptoms was strongly indicative of rostral HNP migration.

Introduction: The prone transpsoas (PTP) approach is a novel, single-position lumbar fusion technique that enables lateral lumbar interbody fusion (LLIF) entirely in the prone position, allowing simultaneous access to both the anterior and posterior spinal columns. While it offers advantages such as achieving circumferential fusion without repositioning the patient, it also presents challenges, including hemodynamic shifts, pressure-related complications, and technical difficulties in navigating complex anatomical structures. This study describes anatomical shifts relative to the lumbar spine when transitioning from the supine to the prone position.

Methods: This retrospective review included patients who underwent posterior lumbar fusion between 2018 and 2024 and had both preoperative magnetic resonance imaging (MRI) and intraoperative prone computed tomography-guided imaging. Patients with deformity, infection, trauma, prior fusion, or malignancy were excluded. Anteroposterior (AP) and mediolateral (ML) distances (in mm) were measured on axial slices using reference lines aligned to vertebral endplates at each lumbar level. Measurements included AP and ML distances to the abdominal great vessels, psoas major, and intervertebral discs. Dependent samples t-tests and analysis of variance were used to assess anatomical shifts from supine to prone and to compare segmental differences.

Results: Among the 74 patients (47% female), the mean age was 62.7±12.2 years, and the mean body mass index was 29.8±5.8 kg/m². Significant AP translation was observed at L2-L3 and L3-L4 for the inferior vena cava (p<0.001) and aorta (p<0.01), and at L4-L5 for the common iliac arteries (p<0.001) and right iliac vein (p<0.05). Symmetric AP excursion of the psoas major muscle was noted at L2-L3 and L4-L5 in the prone position (p<0.05). No significant differences in mean translation were found across lumbar levels.

Conclusions: Prone positioning induces measurable anterior translation of both the psoas major muscle and great vessels, potentially altering the operative corridor utilized in the PTP approach. These discrepancies between supine MRI and prone intraoperative anatomy emphasize the need to account for positional anatomical changes to minimize neurovascular risk during PTP LLIF.