Background:Open-door cervical laminoplasty relies on greenstick fracture at the hinge side to maintain laminar elevation. The hinge reaction force secures hydroxyapatite (HA) spacers without additional fixation, but has never been quantitatively measured. This study aimed to quantify hinge reaction force using a strain gauge system, to identify factors correlated with it, to evaluate its predictive value for early postoperative hinge fracture, and to investigate mid-term bone healing of fractured hinges. Methods:This prospective study included 50 patients (173 laminae) who underwent open-door laminoplasty with stand-alone HA spacers [2015-2017]. Hinge reaction force was measured using a strain gauge-equipped Penfield dissector. Computed tomography (CT) images were evaluated at postoperative day 1 and delayed phase (mean 2.5 years). Results:Mean hinge reaction force was 0.70 kgf (6.87 N). Early hinge fracture occurred in 24/173 laminae (13.9%). The fracture group showed significantly lower force than the non-fracture group (0.46 vs. 0.74 kgf, P<0.001). Receiver operating characteristic (ROC) analysis revealed area under the curve (AUC) of 0.798 with optimal cutoff of 0.59 kgf. At delayed phase, 62% of early fractures (13/21) demonstrated bone healing, and the overall fracture rate decreased to 8.2%. No lamina showed subsidence exceeding 1 mm. Neither Japanese Orthopaedic Association (JOA) recovery rate (P=0.63) nor postoperative pain visual analog scale (VAS) scores differed between groups. Conclusions:This study provides the first quantitative characterization of greenstick fracture reaction force in cervical laminoplasty. The established force benchmarks and predictive threshold (0.59 kgf) offer foundational biomechanical data for developing simplified clinical assessment devices, force-guided selective fixation strategies, and objective surgical training standards.

Study Design: Prospective validation study of smartphone-based gait analysis technology. Objective: To establish the clinical feasibility, test-retest reliability, and criterion-related validity of a smartphone-based Three-Dimensional Pose Tracker for Gait Test (TDPT-GT) in patients with cervical myelopathy. Summary of Background Data: Objective dynamic assessment of cervical spine alignment during functional activities has been limited by the requirement for expensive motion capture systems. Recent advances in artificial intelligence enable markerless motion capture using standard smartphones, but clinical validation in cervical myelopathy patients is lacking. Methods: Ninety-two consecutive patients with cervical spondylotic myelopathy or ossification of the posterior longitudinal ligament underwent TDPT-GT assessment. The system uses deep learning algorithms to track body keypoints during circular walking. Two measurements were performed for reliability analysis. Clinical correlates included the Japanese Orthopaedic Association (JOA) score, the modified Rankin Scale (mRS), the instrumented Timed Up and Go (iTUG), and static radiographic parameters (C2–7 SVA, C2–7 angle, T1 slope). Results: All 92 patients completed the assessment (100% feasibility). Test-retest reliability for TDP neck angle was good [ICC(3,1)=0.851, 95% CI: 0.780–0.900], with SEM of 1.82° and MDC 95 of 5.06°. Bland-Altman analysis showed minimal bias (−0.10°) with 95% limits of agreement from −5.16° to 4.96°. TDP neck angle correlated significantly with JOA score ( ρ =–0.379, P <0.001), C2–7 SVA ( ρ =0.401, P <0.001), and iTUG time ( ρ =0.269, P =0.010). The correlation between dynamic and static cervical parameters supports the construct validity of smartphone-based assessment. Conclusion: TDPT-GT demonstrates good test-retest reliability and meaningful correlations with established clinical measures in cervical myelopathy patients. This accessible technology enables standardized dynamic cervical alignment assessment in routine clinical practice. Levels of Evidence:​​​ Level II—diagnostic study.

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.

Study Design.This was as clinical retrospective study.Objectives.We sought to evaluate the characteristics of Pediatric intramedullary spinal cord tumors (PISCTs) and to identify differences between pediatric and adult intramedullary spinal cord tumors.Summary of Background Data.PISCTs represent a rare clinical entity with limited evidence-base in the literature.Methods.This study is a subanalysis of the retrospective multicenter observational study authorized by the Neurospinal Society of Japan, including consecutive patients with spinal intramedullary tumors treated surgically at 58 institutions between 2009 and 2020. Data on 1080 intramedullary spinal cord tumors were obtained, consisting of 91 pediatric and 939 adult patients. Survival was compared using Cox hazard regression while clinical differences were evaluated using multivariable logistic regression that controlled for confounders.Results.Pediatric patients had a shorter overall, and progression-free, survival than adults. Pediatric patients with ISCTs were likely to have scoliosis [odds ratio (OR) = 6.49, 95% CI: 2.26-18.7], short preoperative symptom duration (OR = 0.99, 95% CI: 0.98-0.99), lower incidence of paresthesia (OR = 0.41, 95% CI: 0.22-0.77), higher incidence of paresis (OR = 2.10, 95% CI: 1.01-4.35), histopathology of astrocytoma (OR = 2.97, 95% CI: 1.19-7.43), and postoperative functional deterioration upon discharge (OR = 2.83, 95% CI: 1.43-5.58). Age was not a statistically significant prognostic factor of overall survival among the pediatric cohort.Conclusion.We found that the clinical characteristics of ISCTs differed between pediatric and adult patients. In terms of histopathological types, astrocytoma was most common in pediatric patients. ISCT occurring at an early age may not be an indicator for poor prognosis.

BACKGROUND A bipartite atlas is a rare congenital anomaly characterized by incomplete fusion of the anterior and posterior arches of the first cervical vertebra (C1). While typically asymptomatic, this condition can result in cervical myelopathy when accompanied by degenerative changes. This report presents a rare case of cervical myelopathy caused by a bipartite atlas in an older patient that required surgical intervention. OBSERVATIONS A 63-year-old male presented with progressive neurological symptoms, including impaired fine motor skills, pain, and paresthesias in both the upper and lower extremities. Imaging revealed a bipartite atlas accompanied by degenerative changes, resulting in significant spinal cord compression. The patient underwent a posterior decompression via C1 laminectomy and duraplasty, resulting in significant clinical improvement and a resolution of symptoms. LESSONS This case highlights the importance of recognizing a bipartite atlas as a potential cause of cervical myelopathy, particularly in older patients with degenerative changes. This is a rare case in which congenital and degenerative factors are intertwined, underscoring the importance of a comprehensive pathological analysis and the development of a personalized treatment strategy. Prompt diagnosis and appropriate surgical intervention are essential for favorable outcomes. https://thejns.org/doi/10.3171/CASE24688

The symptoms of mononeuritis associated with eosinophilic granulomatosis with polyangiitis (EGPA) resemble those of radiculopathy associated with spinal diseases. Herein, we report three cases of neuropathy caused by EGPA, which were suspected of spinal diseases.

To assess pathological gaits quantitatively, three-dimensional coordinates estimated with a deep learning model were converted into body axis plane projections. First, 15 healthy volunteers performed four gait patterns; that is, normal, shuffling, short-stepped, and wide-based gaits, with the Three-Dimensional Pose Tracker for Gait Test (TDPT-GT) application. Second, gaits of 47 patients with idiopathic normal pressure hydrocephalus (iNPH) and 92 healthy elderly individuals in the Takahata cohort were assessed with the TDPT-GT. Two-dimensional relative coordinates were calculated from the three-dimensional coordinates by projecting the sagittal, coronal, and axial planes. Indices of the two-dimensional relative coordinates associated with a pathological gait were comprehensively explored. The candidate indices for the shuffling gait were the angle range of the hip joint < 30° and relative vertical amplitude of the heel < 0.1 on the sagittal projection plane. For the short-stepped gait, the angle range of the knee joint < 45° on the sagittal projection plane was a candidate index. The candidate index for the wide-based gait was the leg outward shift > 0.1 on the axial projection plane. In conclusion, the two-dimensional coordinates on the body axis projection planes calculated from the 3D relative coordinates estimated by the TDPT-GT application enabled the quantification of pathological gait features.

BACKGROUND Ganglioneuroma is a benign and well-differentiated tumor derived from neural crest cells, which occurs infrequently, with most patients being female and adolescents. While predilection sites are the posterior mediastinum and retroperitoneal cavity, ganglioneuroma originating from the dorsal root ganglion is very rare. Here the authors report a case with C2 dorsal root ganglion-derived ganglioneuroma with some literature review. OBSERVATIONS A 45-year-old male patient complained of persistent right-side throbbing occipital headache for more than a year. Magnetic resonance imaging (MRI) of the cervical spine revealed a dumbbell-shaped intradural extramedullary tumor from the C2 posterior surface of the odontoid to right C1–2 intervertebral foramen with high T2- and low T1-weighted signal intensities. The tumor displayed homogeneous contrast enhancement by MRI. The authors suspected schwannoma and performed a tumorectomy for both diagnosis and treatment purposes. Intraoperative findings showed that the tumor originated from the dorsal root ganglion, and pathological examination revealed ganglioneuroma. Immediately after the tumorectomy, the throbbing occipital headache disappeared and the patient was discharged from the hospital without major complications. LESSONS Although ganglioneuroma derived from the dorsal root ganglion is very rare, a differential diagnosis of the ganglioneuroma should be made, when schwannoma is suspected.

BACKGROUND:This retrospective multicenter study aimed to analyze the characteristics and surgical outcomes of intramedullary spinal cord metastasis (ISCM) and to discuss the controversy regarding its surgical indications.METHODS:This study included 29 ISCM patients who underwent surgery between 2009 and 2020. Biopsy cases were excluded from analysis. For functional and neurological functional assessments, Karnofsky Performance Status (KPS, %) and modified McCormick Scale (MMS, 5-grade scale) scores were determined before and after surgery. Patients were divided into two groups: a mild-to-moderate disability group with preoperative MMS grades 1 to 3, and a severe disability group with preoperative MMS grades 4 to 5.RESULTS:The mean preoperative KPS was 45.9, and the mean duration from symptom onset to surgical intervention was 1 month. The ISCM was located in the cervical spine in 10 cases and the thoracic spine in 19 cases. The access route (myelotomy) for ISCM removal was via the posterior median sulcus in 9 cases and via the posterior lateral sulcus in 11 cases, while others were not recorded. The degree of removal was gross total resection in 20 patients (69%), subtotal resection in 0 patients, and partial removal in 9 patients (31%). No significant complications related to the surgical procedures were recorded. Postoperative adjuvant therapy included radiotherapy in 17 patients (58.6%) and chemotherapy or molecular targeted therapy in 13 patients (44.8%). Pathological findings of ISCM showed that colorectal cancer was the most common in 9 cases, followed by lung cancer in 7, renal cell carcinoma in 5, and breast cancer in 2. Twenty-one of the 29 patients (72.4%) were confirmed to have survived 6 months after surgery: 8 of the 10 patients (80%) in the mild-to-moderate disability group and 13 of the 19 patients (68.4%) in the severe disability group. At 6 months after surgery, 3 of the 8 patients (38%) in the mild-to-moderate group were able to maintain or improve their function. Eleven of the 13 patients (85%) in the severe disability group maintained their function despite being severely disabled.CONCLUSIONS:This study suggests that surgical treatment can maintain or improve neurological function in a limited number of patients with ISCM, although it had minimal impact on improving the survival rate after surgery.

To quantitatively assess pathological gait, we developed a novel smartphone application for full-body human motion tracking in real time from markerless video-based images using a smartphone monocular camera and deep learning. As training data for deep learning, the original three-dimensional (3D) dataset comprising more than 1 million captured images from the 3D motion of 90 humanoid characters and the two-dimensional dataset of COCO 2017 were prepared. The 3D heatmap offset data consisting of 28 × 28 × 28 blocks with three red–green–blue colors at the 24 key points of the entire body motion were learned using the convolutional neural network, modified ResNet34. At each key point, the hottest spot deviating from the center of the cell was learned using the tanh function. Our new iOS application could detect the relative tri-axial coordinates of the 24 whole-body key points centered on the navel in real time without any markers for motion capture. By using the relative coordinates, the 3D angles of the neck, lumbar, bilateral hip, knee, and ankle joints were estimated. Any human motion could be quantitatively and easily assessed using a new smartphone application named Three-Dimensional Pose Tracker for Gait Test (TDPT-GT) without any body markers or multipoint cameras.

Objective: To assess the current management of primary spinal cord tumors (PSCTs) and determine whether and to what extent there are differences in surgical strategies for PSCTs.Methods: The Neurospinal Society of Japan conducted a survey between April 1 and 30, 2021. Certified spine surgeons were requested for information on the frequency of surgeries in 2020 and the surgical strategies adopted for each PSCTs. The following tumor histologies were focused: schwannoma, meningioma, and cauda equina tumor as extramedullary tumors; and ependymoma, hemangioblastoma, astrocytoma, and cavernoma as intramedullary tumors. The participants were divided according to their response as follows: experts, who had experienced ≥ 100 surgeries for PSCTs, and nonexperts.Results: Among 308 participants (63%), 35 (11%) were experts. The total number of PSCTs in 2020 was 802 of which 564 tumors were extramedullary and 223 were intramedullary. Schwannoma accounted for 53% of the extramedullary tumors, and ependymoma accounted for 39% of the intramedullary tumors. Surgical strategies significantly differed among both the experts and nonexperts groups. Some discrepancies in the adopted surgical strategies were observed between groups. Some of the nonexperts, and none of the experts, ruled out surgery for schwannomas (Eden type 4), astrocytomas, or cavernomas. Five nonexperts (2.2%), and none of the experts, resected the entire dura for meningiomas.Conclusion: A nationwide survey revealed that a sufficient consensus did not exist regarding surgical strategies for PSCTs. A disease-specific registry for PSCTs is necessary in academic societies.

Objective We performed a retrospective observational study to demonstrate the surgical risks and long-term prognoses of intramedullary tumors in Japan using a multicenter registry authorized by the Neurospinal Society of Japan. Methods Data from 1,033 consecutive patients with intramedullary tumors, treated between 2009 and 2020, were collected from 58 centers. Patients with spinal lipomas or myxopapillary ependymomas were excluded. Patient characteristics, clinical presentations, imaging characteristics, treatments, and outcomes were analyzed. The modified McCormick scale was used to classify functional status. Survival was described using Kaplan-Meier curves, and multivariable logistic regression analyses were performed. Results The mean age of the patients was 48.4 years. Data of 361 ependymomas, 196 hemangioblastomas, 168 astrocytic tumors, 160 cavernous malformations, and the remaining 126 cases including subependymomas, metastases, schwannomas, capillary hemangiomas, and intravascular B-cell lymphomas were analyzed. Twenty-two patients were undiagnosed. The mean follow-up duration was 46.1 ± 38.5 months. Gross total tumor removal was achieved in 672 tumors (65.1%). On the modified McCormick scale, 234 patients (22.7%) had worse postoperative grades at the time of discharge. However, neurological status gradually improved. At 6 months postoperatively, 251 (27.5%), 500 (54.9%), and 160 patients (17.6%) had improved, unchanged, and worsened grades, respectively. Preoperative functional status, gross total tumor removal, and histopathological type were significantly associated with mortality and functional outcomes. Conclusion Our findings demonstrate better postoperative functional outcomes in patients with fewer preoperative neurological deficits. Degree of resection, postoperative treatments, and prognoses are closely related to the histology of intramedullary tumors.

Intradural extramedullary (IDEM) ependymoma except for tumors originated from the filum terminale or conus medullaris is rare. The present study showed a case of IDEM ependymoma. A 16-year-old boy was referred to our hospital with a complaint of right hypochondriac pain and motor weakness in his right leg. MRI revealed a solitary intradural tumor at Th5-8 level with syringomyelia at Th2-4 level. Microscopic total tumor resection was performed with right hemi-laminectomy of Th4-9. Histological diagnosis was ependymoma (WHO grade 2). Although his leg weakness was worsened transiently, he showed improvement in leg weakness being able to go up and down the stairs 1 month after the surgery. There was no tumor recurrence until now, 7 years after the surgery, without any adjunctive therapies. A total of 44 cases of IDEM ependymoma had been reported in the past literatures. They are thought to arise from ependymal cells which remained during the process of neural tube closure. Like intramedullary ependymomas, most of the IDEM ependymomas have clear border to surrounding tissue and often removed completely. However, a small number of recurrences and malignant transformations had been reported after complete resections despite benign histological features tumors. In the case of totally resected low grade IDEM ependymoma, it is thought to be reasonable to perform long-term periodical radiographic follow-up without postoperative adjunctive therapy.

The goal of surgery for degenerative spine disease is to decompress nerves; however, extensive spinal decompression may compromise spinal stability. Therefore, spinal fusion surgery is performed to immediately stabilize such anatomical disruption during a short hospital stay and to allow quick recuperation. Recently, implants such as pedicle screws and intervertebral cages have been regularly used in lumbar fusion surgery. These implants are used to reconstruct the functional unit of the failed spine, correcting any deformity if necessary and maintaining its fixation until complete bone fusion. In other words, the essence of spinal fusion surgery is not the placement of implants but the induction of bone fusion. Therefore, each case requires a carefully developed surgical plan to achieve sufficient bone fusion for spinal stabilization. In this article, we describe the mechanism and the surgical technique for achieving reliable interbody fusion.

The incidence of degenerative spine disease has been rapidly rising because of the increasing number of elderly. In recent years, minimally invasive spinal surgery has been an option for elderly patients who can often not undergo conventional surgical methods. As a result, the number of surgeries for degenerative spine disease has been increasing. Spinal degenerative diseases involve static and dynamic factors. Additionally, age‒associated degenerative changes induce anatomical spinal changes(in the ligamentum flavum, the intervertebral disc, etc.) that differ from the characteristics present in intracranial disorders. Neurosurgeons need to consider this when diagnosing spine disorders. In this article, we give an overview of minimally invasive spinal surgery for lumbar spinal degenerative diseases, focusing on the surgical options available for lumbar spinal canal stenosis. (Received January 31, 2020;accepted February 19, 2020)