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Study Design: Narrative Review., Objectives: The premise of this review is to provide a review of the literature pertaining to studies describing outcomes of surgical cohorts when implementing C1 osteosynthesis for arch fractures with or without transverse atlantal ligamentous (TAL) injury., Methods: A comprehensive search strategy was implemented across several search engines to identify studies which evaluate the outcomes of C1 osteosynthesis for patients with C1 arch fractures with and without TAL injury., Results: Ten studies were identified. Parameters reported included osteosynthesis fusion rates, deformity correction, preservation of motion segments, patient reported outcome measures and overall complications. Overall, C1 osteosynthesis showed excellent fusion rates with complications comparable to traditional techniques denoted in literature. Furthermore, the osteosynthesis technique depicted good overall deformity correction and preservation of motion segments, in addition to good patient reported outcomes., Conclusion: It appears C1 osteosynthesis offers a safe and efficacious alternative option for the surgical treatment of C1 fractures with TAL rupture. It has the potential to reduce deformity, increase ROM, improve PROMs and has complication rates comparable with those of fusion techniques. However more robust prospective evidence is required., (© 2024. The Author(s).)

Purpose: Surgical stabilization of the Atlas vertebrae is indicated for severe atlantoaxial instability (AAI) in patients with Down syndrome (DS). This study aims to evaluate the morphological characteristics of the Atlas lateral mass (ALM) in patients with DS with regard to safe instrumentation for surgical stabilization and to compare them with non-syndromic group., Methods: This multicenter, retrospective, case-control study included age- and sex-matched patients with and without DS aged > 7 years with a cervical computed tomography (CT) scan. After three-dimensional CT reconstruction, nine parameters were evaluated for both groups. All included measurements were performed by a neuroradiologist who was blinded to clinical data., Results: Forty-three of 3,275 patients with DS were included in this study. Matching number of consecutive patients without DS were identified (mean age: 16 years). Patients with DS were significantly shorter than those without DS. Seven of nine parameters related to ALM were significantly lower in patients with DS than in those in the control group, including anterior wall height (AH), posterior wall height (PH), their ratio, and arch-ALM angle. On adjusting data for patient height, patients with DS had a smaller PH, lower PH/AH ratio, and steeper arch-ALM angle than the control group., Conclusions: Patients with DS had a smaller posterior ALM wall and a steeper arch-ALM angle than the control group without DS. This information is important for surgical planning of safe posterior ALM exposure and safe instrumentation for surgical stabilization in patients with DS., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Various surgical nuances of the telovelar approach have been suggested. The necessity of removing the posterior arch of C1 to accomplish optimal tumor exposure is still debated. Therefore, we report on our experience and technical details of the fourth ventricular tumor resection in a modified prone position without systematic removal of the posterior arch of C1., Methods: A retrospective analysis of all pediatric patients, who underwent a fourth ventricular tumor resection in the modified prone position between 2012 and 2021, was performed., Results: We identified 40 patients with a median age of 6 years and a M:F ratio of 25:15. A telovelar approach was performed in all cases. In 39/40 patients, the posterior arch of C1 was not removed. In the remaining patient, the reason for removing C1 was tumor extension below the level of C2 with ventral extension. Gross or near total resection could be achieved in 34/39 patients, and subtotal resection in 5/39 patients. In none of the patients, a limited exposure, sight of view, or range of motion caused by the posterior arch of C1 was encountered, necessitating an unplanned removal of the posterior arch of C1. Importantly, in none of the cases, the surgeon had the impression of a limited sight of view to the most rostral parts of the fourth ventricle, which necessitated a vermian incision., Conclusion: A telovelar approach without the removal of the posterior arch of C1 allows for an optimal exposure of the fourth ventricle provided that critical nuances in patient positioning are considered., (© 2024. The Author(s).)

Introduction and Objectives: The objective of the study was: (1) to describe changes in the shape of the atlas during growth, including gender and side differences; (2) to assess the dimension essential for identification of the optimal entry point; (3) to determine the age limit for a safe insertion of 3.5-mm screws into the lateral masses according to our own limiting parameters., Materials and Methods: Dimensions of the atlas were measured on 200 CT scans of the craniocervical junction in individuals aged 0-18 years and on 34 anatomical specimens of the first cervical vertebra (aged 2.5-18 years). Both series were divided according to the gender and age. The values measured on CT scans were used for statistical comparison of data in boys and girls and comparison of the right and left sides., Results: The atlas reaches its maximum growth rate between 0 and 2 years of age, then the growth decelerates and continues until the age of 18 years. The proportion of dimensions of C1 vertebral foramens changes with age. The youngest children show a relatively greater distance from the left to the right medial pedicle; around the age of 5 the values get even and subsequently the distance from the inner wall of anterior to posterior arch gets relatively greater. The transverse foramen has a slightly oval shape throughout the period of growth. Statistically significant differences between boys and girls were observed primarily between 12 and 18 years of age., Conclusion: The study has proved adequate size of lateral masses for insertion of 3.5-mm screws in all patients from the age of 5 years. In younger children, the patient´s anatomy should be respected and the surgical technique tailored accordingly., (Copyright © 2024. Published by Elsevier España, S.L.U.)

An in-depth understanding of the anatomy of the craniocervical junction (CCJ) is indispensable in skull base neurosurgery. In this paper, we discuss the osteology of the occipital bone, the atlas (C1) and axis (C2), the ligaments and the muscle anatomy of the CCJ region and their relationships with the vertebral artery. We will also discuss the trajectory of the vertebral artery and review the anatomy of the jugular foramen and lower cranial nerves (IX to XII). The most important surgical approaches to the CCJ, including the far lateral approach, the anterolateral approach of Bernard George and the endoscopic endonasal approach, will be discussed to review the surgical anatomy., (Copyright © 2023 Elsevier Masson SAS. All rights reserved.)

Background: Glossopharyngeal neuralgia (GPN) is a condition that causes simultaneous headache and facial pain. The treatment for GPN is similar to the treatment for trigeminal neuralgia. Craniotomy microvascular decompression (MVD) or radiofrequency (RF) therapy is needed if conservative treatment with oral drugs fails. Therefore, the choice of radiofrequency therapy target is essential when treating GPN. However, finding the glossopharyngeal nerve simply by styloid process positioning is challenging., Study Design: Prospective, clinical research study., Setting: Department of Anesthesiology and Pain Medical Center, Jiaxing, China., Objective: To compare the clinical effects of computed tomography (CT)-guided RF treatments on GPN when the triple localization of cervical CT, the transverse process of the atlas, and the styloid process is used to those achieved when the treatments are guided by the styloid process alone., Methods: From August 2016 to December 2019, 19 cases of GPN neuralgia were treated by radiofrequency under the guidance of CT guided by the styloid process only. (These patients comprised the single localization (SL) of styloid process group, in whom the target of the RF treatments was the posterior medial side of half of the styloid process). From January 2020 to December 2022, 16 cases of GPN were treated by RF under the guidance of CT with cervical CTA (CT angiography), the transverse process of the atlas, and the styloid process. (These patients were placed in the TL group, in whom the target of RF therapy was the gap between the internal carotid artery and the internal jugular vein behind the horizontal styloid process at the lower edge of the transverse process of the atlas). Two percent lidocaine was injected subcutaneously at the needle insertion site, and a stylet with a 21-gauge blunt RF needle (model: 240100, manufacturer: Englander Medical Technology Co., Ltd.) was slowly advanced toward the target. After that, an RF probe was introduced, then low (2 Hz)- and high (50 Hz)-frequency currents of the RF instrument (model: PMG-230, Canada Baylis company) were applied to stimulate. A successful test was defined as a 0.5-1.0 mA current stimulation that could induce the original pain area in the pharynx, the inner ear, or both, without any abnormal irritation of the vagus or accessory nerves. If the first test was unsuccessful, then in the SL group, the needle tip's position was adjusted to the distal end of the styloid process, and in the triple localization (TL) group, the needle tip depth's was fine-tuned. A continuous RF treatment was given after a successful test. The RF temperature was 95ºC for 180 seconds. The time that the first puncture reached the target, the puncture paths, the success rate of the first test, the time that the glossopharyngeal nerve was found, the frequency of adjustments to the position of the RF needle, the incidence of intraoperative and postoperative complications, and the therapeutic effects were recorded., Results: There were no significant differences in demographic data such as age, medical history, lateral classification, and pain score between the groups, but the TL group had a higher proportion of women than did the SL group. All patients' puncture targets were identified according to the designed puncture path before the operation. There was no difference between the 2 groups in the time of the first puncture to the target (5.05 ± 1.22 vs. 5.82 ± 1.51, P = 0.18), and the designed puncture depth (3.65 ± 0.39 vs. 4.04 ± 0.44). The difference in puncture angles (13.48 ± 3.56 vs. 17.84 ± 3.98, P < 0.01) was statistically significant, and in 8 cases in the SL group, the glossopharyngeal nerve could not be found after 60 minutes of testing, so the RF treatment was terminated. Meanwhile, this problem occurred in only 2 cases in the TL group. There were 3 cervical hematoma cases and 2 cases of transient hoarseness and cough in the SL group, whereas the TL group had, respectively, 0 and one cases of those issues. There was no death in either group., Limitations: More clinical data should be collected in future studies., Conclusion: When using RF as a treatment for GPN, the glossopharyngeal nerve is easier to find by using the triple positioning of the cervical CTA, the transverse process of the atlas and the styloid process as the target to determine the anterior medial edge of the internal carotid artery behind the styloid process at the level of the lower edge of the atlas transverse process. The glossopharyngeal nerve is more difficult to locate when only the posterior medial edge of the styloid process is targeted. The single-time effective rate of 180 seconds of RF ablation at 90ºC for GPN can reach 87.5% (14/16), suggesting the treatment's potential for clinical application.

Objective: Congenital anomalies of the atlanto-occipital articulation may be present in patients with Chiari malformation type I (CM-I). However, it is unclear how these anomalies affect the biomechanical stability of the craniovertebral junction (CVJ) and whether they are associated with an increased incidence of occipitocervical fusion (OCF) following posterior fossa decompression (PFD). The objective of this study was to determine the prevalence of condylar hypoplasia and atlas anomalies in children with CM-I and syringomyelia. The authors also investigated the predictive contribution of these anomalies to the occurrence of OCF following PFD (PFD+OCF)., Methods: The authors analyzed the prevalence of condylar hypoplasia and atlas arch anomalies for patients in the Park-Reeves Syringomyelia Research Consortium database who underwent PFD+OCF. Condylar hypoplasia was defined by an atlanto-occipital joint axis angle (AOJAA) ≥ 130°. Atlas assimilation and arch anomalies were identified on presurgical radiographic imaging. This PFD+OCF cohort was compared with a control cohort of patients who underwent PFD alone. The control group was matched to the PFD+OCF cohort according to age, sex, and duration of symptoms at a 2:1 ratio., Results: Clinical features and radiographic atlanto-occipital joint parameters were compared between 19 patients in the PFD+OCF cohort and 38 patients in the PFD-only cohort. Demographic data were not significantly different between cohorts (p > 0.05). The mean AOJAA was significantly higher in the PFD+OCF group than in the PFD group (144° ± 12° vs 127° ± 6°, p < 0.0001). In the PFD+OCF group, atlas assimilation and atlas arch anomalies were identified in 10 (53%) and 5 (26%) patients, respectively. These anomalies were absent (n = 0) in the PFD group (p < 0.001). Multivariate regression analysis identified the following 3 CVJ radiographic variables that were predictive of OCF occurrence after PFD: AOJAA ≥ 130° (p = 0.01), clivoaxial angle < 125° (p = 0.02), and occipital condyle-C2 sagittal vertical alignment (C-C2SVA) ≥ 5 mm (p = 0.01). A predictive model based on these 3 factors accurately predicted OCF following PFD (C-statistic 0.95)., Conclusions: The authors' results indicate that the occipital condyle-atlas joint complex might affect the biomechanical integrity of the CVJ in children with CM-I and syringomyelia. They describe the role of the AOJAA metric as an independent predictive factor for occurrence of OCF following PFD. Preoperative identification of these skeletal abnormalities may be used to guide surgical planning and treatment of patients with complex CM-I and coexistent osseous pathology.

Purpose: The treatment of unstable atlas fractures remains a controversial topic. The study aims at assessing the prognosis and efficacy of osteosynthesis for unstable atlas fractures through a review of the current literature and additionally aims to compare outcomes between the transoral and posterior approaches., Methods: A systematic review of databases including PubMed, EMBASE, Cochrane, Web of Science, CNKI, and Wanfang was conducted. Titles and abstracts were screened by two reviewers to identify studies meeting pre-defined inclusion criteria for comprehensive analysis., Results: The systematic review included 28 articles, 19 employing the posterior approach and 9 utilizing the transoral approach. It covered osteosynthesis in 297 patients with unstable atlas fractures, comprising 169 treated via the posterior approach and 128 via the transoral approach. Analysis revealed high healing rates and clinical improvement in both approaches, evidenced by improvements in the visual analog scale, range of motion, atlantodens interval, and lateral displacement distance post-surgery., Conclusion: Osteosynthesis offers effective treatment for unstable atlas fractures. Both transoral and posterior approaches can achieve good clinical outcomes for fracture, and biomechanical studies have confirmed that osteosynthesis can maintain the stability of the occipitocervical region, preserve the motor function of the atlantoaxial and occipito-atlantoaxial joints, and greatly improve the quality of life of patients. However, variations exist in the indications and surgical risks associated with each method, necessitating their selection based on a thorough clinical evaluation of the patient's condition., (© 2024. The Author(s).)

The posterior arch of the atlas is usually not considered one of the main stabilizers of the cranio-cervical junction, allowing surgeons to its removal when needed with a relative certainty to preserve the stability of the atlo-axial segment. However, these considerations do not reflect the importance to examine the integrity of the posterior arch in the whole biomechanics of the atlas. Authors like Gebauer and Panjabi revealed, respectively in experimental and clinical conditions, how the atlas responds to an axial loading force, proving that the whole atlas is involved into horizontal conversion of axial forces and providing evidence supporting the preservation of the posterior arch. Other authors evaluated the risk for anterior arch fracture following C1 laminectomy. In this technical note three different techniques of posterior atlas arch reconstruction after surgical iatrogenic disruption are presented, considering both neoplastic and degenerative disease.

Study Design: Retrospective radiographic analysis., Objectives: Evaluation of the anatomic features of the craniovertebral junction in patients with occipitalization with and without atlantoaxial dislocation (AAD)., Summary of Background Data: Atlas occipitalization is a common feature of congenital AAD and usually requires surgical intervention. However, not all instances of occipitalization necessarily lead to AAD. No study has specifically examined and compared the craniovertebral bony morphology in occipitalization with, and without, AAD., Materials and Method: We reviewed computed tomography (CT) scans of 2500 adult outpatients. Occipitalization cases without AAD (ON) were selected. Meanwhile, a series of 20 inpatient occipitalization cases with AAD (OD) were obtained in parallel. Another 20 control cases without occipitalization were also included. Multi-directional reconstructed CT images of all cases were analyzed., Results: A total of 18 adults with ON were found in all 2500 outpatients (0.7%). Both anterior height and posterior height of C1 lateral mass in the control group were significantly larger than those in both the ON and OD groups, whereas posterior height in the OD group was significantly less than that in the ON group. Three morphologic types of the occipitalized atlas posterior arch were identified: Type I, bilateral sides were unfused with opisthion; Type II, unilateral side was unfused with opisthion, whereas the other side was fused; and Type III, bilateral sides were fused with opisthion. In the ON group, three cases were type I (17%), six cases were type II (33%), and nine cases were type III (50%). In the OD group, all 20 cases were type III (100%)., Conclusions: Atlas occipitalization with, and without, AAD results from a distinctly different bony morphology at the craniovertebral junction. The novel classification system based on reconstructed CT images may be useful in prognosticating AAD in the setting of atlas occipitalization., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

The paracondylar process (PCP) and the persistent first intersegmental vertebral artery (PFIA) are both rare variations at the craniovertebral junction. We report the above two variations coexisting in one cadaveric head during the training of far lateral approach in our skull base lab. The specimen simultaneously had a left occipitalized atlas associated with a PFIA and a right PCP. The previous reports, the embryogenesis, and the clinical implications of the two variations were also reviewed. Preoperative recognition of the rare variations is essential to a safe far lateral approach.

BACKGROUND Although most unstable C1 fractures can be effectively treated either by conservative treatment with external immobilization or by surgical procedure of C1-ring osteosynthesis, those fractures involving the lateral mass are likely to lead to traumatic arthritis and persistent neck pain. Specific reports of treatment of unstable C1 fractures involving the lateral mass are still scarce. We therefore present this report to evaluate the effectiveness of posterior C1-C2 screw-rod fixation and fusion for unstable C1 fractures involving the lateral mass. MATERIAL AND METHODS From June 2009 to June 2016 in our hospital, 16 cases were diagnosed with C1 fractures involving the lateral mass and treated by posterior C1-C2 screw-rod fixation and fusion from June 2009 to June 2016. The patients' clinical data were retrospectively analyzed. Preoperative and postoperative images were taken to evaluate cervical sequence, location of screws, and bone fusion. Neurological status and neck pain levels were evaluated clinically on follow-up. RESULTS All patients underwent surgery successfully. The mean follow-up duration was 15.3±4.9 months (range 9-24 months). All patients obtained satisfying clinical outcomes with good neck pain alleviation, appropriate screw placement, and reliable bone fusion. None of the patients developed vascular or neurological complications during the operation or follow-up. CONCLUSIONS Posterior C1-C2 screw-rod fixation and fusion is an effective management for unstable C1 fractures involving the lateral mass. This operation can provide reliable stabilization and satisfactory bone fusion.

Background:  Atlantoaxial instability is an important disorder that causes serious symptoms such as difficulties in walking, limited neck mobility, sensory deficits, etc. Atlantal lateral mass screw fixation is a surgical technique that has gained important recognition and popularity. Because accurate drilling area for screw placement is of utmost importance for a successful surgery, we aimed to investigate morphometry of especially the posterior part of C1., Methods:  One hundred and fifty-eight human adult C1 dried vertebrae were obtained. Measurements were performed directly on dry atlas vertebrae, and all parameters were measured by using a digital caliper accurate to 0.01 mm for linear measurements., Results:  The mean distance between the tip of the posterior arch and the medial inner edge of the groove was found to be 10.59 ± 2.26 and 10.49 ± 2.20 mm on the right and left, respectively. The mean distance between the tip of the posterior arch and the anterolateral outer edge of the groove was 21.27 ± 2.28 mm (right: 20.96 ± 2.22 mm; left: 21.32 ± 2.27 mm). The mean height of the screw entry zone on the right and left sides, respectively, were 3.86 ± 0.81 and 3.84 ± 0.77 mm. The mean width of the screw entry zone on both sides was 13.15 ± 1.17 and 13.25 ± 1.3 mm., Conclusion:  Our result provided the literature with a detailed database for the morphometry of C1, especially in relation to the vertebral artery groove. We believe that the data in the present study can help surgeons to adopt a more accurate approach in terms of accurate lateral mass screw placement in atlantoaxial instability., Competing Interests: None declared., (Thieme. All rights reserved.)

Background: In the treatment of unstable atlas fractures using the combined anterior-posterior approach or the posterior monoaxial screw-rod system, factors such as severe trauma or complex surgical procedures still need to be improved despite the favourable reduction effect. This research described and evaluated a new technique for the treatment of unstable atlas fracture using a self-designed lateral mass screw-plate system., Methods: A total of 10 patients with unstable atlas fractures using this new screw-plate system from January 2019 to December 2021 were retrospectively reviewed. All patients underwent posterior open reduction and internal fixation (ORIF) with a self-designed screw-plate system. The medical records and radiographs before and after surgery were noted. Preoperative and postoperative CT scans were used to determine the type of fracture and evaluate the reduction of fracture., Results: All 10 patients were successfully operated with this new system, with an average follow-up of 16.7 ± 9.6 months. A total of 10 plates were placed, and all 20 screws were inserted into the atlas lateral masses. The mean operating time was 108.7 ± 20.1 min and the average estimated blood loss was 98.0 ± 41.3 ml. The lateral mass displacement (LMD) averaged 7.1 ± 1.9 mm before surgery and almost achieved satisfactory reduction after surgery. All the fractures achieved bony healing without reduction loss or implant failure. No complications (vertebral artery injury, neurologic deficit, or wound infection) occurred in these 10 patients. At the final follow-up, the anterior atlantodens interval (AADI) was 2.3 ± 0.8 mm and the visual analog scale (VAS) was 0.6 ± 0.7 on average. All patients preserved almost full range of motion of the upper cervical spine and achieved a good clinical outcome at the last follow-up., Conclusions: Posterior osteosynthesis with this new screw-plate system can provide a new therapeutic strategy for unstable atlas fractures with simple and almost satisfactory reduction., (© 2023. The Author(s).)

Purpose: To compare the Atlas (C1) lateral mass screw placement between screw trajectories of 0° and 15° medial angulation while using the intersection between lateral mass and inferomedial edge of the posterior arch., Methods: Forty-eight Atlas lateral masses were prepared and divided into 2 groups: Group 1; screws inserted at 3 mm lateral to the reference point with screw trajectory of 0° angulation(N = 24) and Group 2; those inserted with screw trajectory of 15° medial angulation(N = 24). We evaluated the atlas anatomy, screw purchase and the presence of any breaches using CT scan., Results: The radiographic parameters for Groups 1 and 2 were found statistically different (p-value < 0.05): bilateral intraosseous screw lengths (17.92 ± 1.47 mm. vs. 20.71 ± 2.4 mm.), bilateral screw length (29.92 ± 1.72 mm. vs. 33.13 ± 1.78 mm.), left screw medial angulation (x°) (0.67° ± 0.78° vs.14.17° ± 3.51°), right screw medial angulation (y°) (0.83° ± 1.03° vs.14.25° ± 2.53°) and bilateral screw medial angulation (0.75° ± 0.9° vs. 14.21° ± 2.99°). Twenty-two screws (91.67%) using the 0° medial angulation and nineteen screws (79.17%) using the 15° medial angulation had no cortical violations (Grade 0). However, two screws (8.33%) with 0° medial angulation and five screws (20.83%) with 15° medial angulation had breach less than 2 mm (Grade 1). There were no screws with breach between 2 and 4 mm (Grade 2) or greater than 4 mm. (Grade 3)., Conclusion: A starting point of 3-mm lateral to the intersection between lateral mass and inferomedial edge of the Atlas posterior arch can be safely and effectively used to insert C1 lateral mass using both 0° and 15° medial angulation., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Chiari 1 malformation has crowding at craniovertebral junction (CVJ), treated by Foramen magnum decompression (FMD) but is associated with high failure rates, which is explained by recently introduced concept of central instability. So, we propose a new concept of relieving this crowding without affecting stability., Objective: To derive a threshold for coring out of internal surface of C1 posterior arch instead of complete laminectomy accompanying FMD., Methods and Material: We prospectively included nine patients with a mean age of 25.33 ± 7.97 years, diagnosed with ACM-1 without AAD, who were operated with FMD and lax duraplasty and C1 laminectomy. The preoperative dural diameter and area covered under the dura at the level of C1 were measured and compared with the postoperative state. Results were analyzed to derive a cut-off threshold which could be drilled from the inner aspect of C1 arch., Results: The postoperative AP diameter of the dura increased statistically significantly from pre-op; however, the AP extension was less than the preoperative diameter with posterior arch included. Likewise, the area spanned by the dura increased statistically significantly from pre-op but was less than the cumulative area of dura with C1 arch included in pre-op. Analyzing all, a mean cut-off of 50.58% was achieved., Conclusion: The authors suggest FMD with partial coring (~50%) of the inner part of arch of C1, instead of full-thickness laminectomy with a wider length of coring as the target, and this will serve the purpose intended, without increasing mobility., Competing Interests: None

Background: The growth and development of the atlas in children has not been studied to date using a large sample size., Objective: To study whether a 3.5-mm screw is suitable for the atlas in children, to explore the anatomical size and development of the atlas in 0-14-year-old children, and to provide morphological basis for lateral mass screw internal fixation., Methods: A Computed Tomography (CT) morphometric analysis was performed on 420 pediatric atlases. In the atlas, D1, D2, D3, D4, and α of the atlas lateral mass were measured. Statistical analysis was performed using one-way ANOVA and Students' t test. The least square method was used for the regression analysis of the change trend in anatomical structure. The curve with the greatest goodness of fit was used as the anatomic trend regression curve., Results: D1, D2, D3, and D4 generally showed an increasing trend with age. The ranges of averages of D1, D2, D3, D4, and α in 0-14 year-old children were as follows: 4.576-9.202 mm, 9.560-25.100 mm, 3.414-10.554 mm, 11.150-27.895, and 12.41°-20.97°, respectively. The trends of the fitting curves of L1 and L3 were power functions, and those of L2 and L4 were logarithmic curves., Conclusions: CT examination could help in preoperative decision-making, and 3.5-mm screw was found to be suitable for lateral mass screw internal fixation in children aging 2 years and older. D1-D4 increased with age. This provided a certain reference to perform posterior atlantoaxial fusion in children and is of great significance to design posterior atlantoaxial screw in children., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: To investigate the radiologic and clinical outcomes of direct internal fixation for unstable atlas fractures., Materials and Methods: This retrospective study included 12 patients with unstable atlas fractures surgically treated using C1 lateral mass screws, rods, and transverse connector constructs. Nine lateral mass fractures with transverse atlantal ligament (TAL) avulsion injury and three 4-part fractures with TAL injury (two avulsion injuries, one TAL substance tear) were treated. Radiologic outcomes included the anterior atlantodental interval (AADI) in flexion and extension cervical spine lateral radiographs at 6 months and 1 year after treatment. CT was also performed to visualize bony healing of the atlas at 6 months and 1 year. Visual Analog Scale (VAS) scores for neck pain, Neck Disability Index (NDI) values, and cervical range of motion (flexion, extension, and rotation) were recorded at 6 months after surgery., Results: The mean postoperative extension and flexion AADIs were 3.79±1.56 (mean±SD) and 3.13±1.01 mm, respectively. Then mean AADI was 3.42±1.34 and 3.33±1.24 mm at 6 months and 1 year after surgery, respectively. At 1 year after surgery, 11 patients showed bony healing of the atlas on CT images. Only one patient underwent revision surgery 8 months after primary surgery due to nonunion and instability findings. The mean VAS score for neck pain was 0.92±0.99, and the mean NDI value was 8.08±5.70., Conclusion: C1 motion-preserving direct internal fixation technique results in good reduction and stabilization of unstable atlas fractures. This technique allows for the preservation of craniocervical and atlantoaxial motion., Competing Interests: The authors have no potential conflicts of interest to disclose., (© Copyright: Yonsei University College of Medicine 2022.)

Objective: To explore the corridor for atlas pedicle screw placement perpendicular to the coronal plane and to develop patient-specific navigation templates for pedicle screw placement., Methods: This study is a retrospective analysis. A total of 71 patients (41 males and 30 females) were involved in this study from June 2016 to June 2018, and they were divided into a template group (39 patients) and a conventional group (32 patients). The CT-based 3D reconstruction models were analyzed in the template group. From the perspective of the 3D atlas in a coronal view, the pedicle corridor was obtained. Taking the center of the tangential circle of the pedicle as the entry point, we simulated screw placement perpendicular to the coronal plane. Then, the individual navigation template was designed and used in surgery. In the conventional group, free-hand pedicle screw placement was performed perpendicular to the coronal plane. The diameter of the maximum tangential circle and screw length of the pedicle corridor were measured in the template group. The surgical time, radiation exposure time, screw grading criteria and so on were evaluated and compared between the two groups after surgery., Results: ;The diameter of the maximum tangential circle and the distance between the entry point and posterior tubercle were significantly greater in males than in females. The operation was successfully completed in all patients, without aggravation of nerve injury, and the follow-up was 12-20 months, with an average of 15.6 months. A total of 78 screws were inserted in the template group, and 64 screws were inserted in the conventional group. The surgical times in the template group and conventional group were 76.47±24.44 min and 125.63±36.41 min, respectively. The radiation exposure times in the template group and conventional group were 3.51±1.77 and 10.15±4.95, respectively, and there was a significant difference between the two groups. In the template group, the deviation in the screw entry point and screw angle were 1.92±1.67 mm and 2.08±1.98°, respectively. The medial angle deviation between the left and right sides was 2.71±1.88° in the template group, which was significantly less than the deviation of 3.76±2.22° in the conventional group., Conclusion: A pedicle screw trajectory perpendicular to the coronal plane can be quickly obtained based on the perspective of 3D models. The technique of screw placement perpendicular to the coronal plane assisted by navigation templates has a shorter operative time, lessintraoperative fluoroscopy and a higher safety of screw placement than traditional surgery.

Study Design: A retrospective study., Objective: Investigate the diagnosis and surgery strategy for treatment of development spinal canal stenosis (DSSA) at atlas plane based on computerized tography (CT) image characters., Summary of Background Data: The occurrence of spinal canal stenosis in the atlas plane is relatively rare compared with lower cervical., Methods: Fifteen patients diagnosed with DSSA were included from 2014 to 2018. They are divided into four subgroups based on the character of CT images: group I (small size atlas), group II (hypertrophy of posterior arch of the atlas [PAA]), group III (incurved of PAA), and group IV (hypertrophy odontoid)., Results: There are type I 7, type II 3, type III 2, and group IV 3 in the 15 cases. All the patients received different surgery procedures respectively: (1) posterior arch osteotomy were performed for group I/III//IV without atlantoaxial dislocation, (2) posterior arch resect and replantation were performed for group II, (3) occipital cervical fixation and fusion were added to the patients with associated atlantoaxial dislocation (AAD), (4) a new method of odontoid reduce and atlantoaxial fixation by transoral approach were performed for group IV with associated AAD. All cases underwent surgery successfully which included posterior occipitocervical fixation (OCF) + posterior arch resection (PAR) eight cases, PAR four cases, posterior arch remodeling and re-implantation (PARR) two cases, and Dens remodeling + trans-oral anterior reduction and plate fixation (DR+TARP) one case without severe complications. All patients show different improvement in the symptoms. Japanese orthopaedic association score improved from 9.2 to 14.7 in 1 year follow-up., Conclusion: DSSA could be easily diagnosed and divided into four subgroups according to the character of CT image, corresponding surgery strategy could receive a fine clinical result.Level of Evidence: 4., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Craniocervical injuries (CCJs) account for 10% to 30% of all cervical spine trauma. An increasing number of patients are surviving these injuries due to advancements in automobile technology, resuscitation techniques, and diagnostic modalities. The leading injury mechanisms are motor vehicle crashes, falls from height, and sports-related events. Current treatment with urgent rigid posterior fixation of the occiput to the cervical spine has resulted in a substantial reduction in management delays expedites treatment of CCJ injuries. Within CCJ injuries, there is a spectrum of instability, ranging from isolated nondisplaced occipital condyle fractures treated nonoperatively to highly unstable injuries with severely distracted craniocervical dissociation. Despite the evolution of understanding and improvement in the management of cases regarding catastrophic failure to diagnose, subsequent neurologic deterioration still occurs even in experienced trauma centers. The purpose of this article is to review the injuries that occur at the CCJ with the accompanying anatomy, presentation, imaging, classification, management, and outcomes., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: To characterize surgical treatment and outcomes of C1 fractures in a population-based setup., Methods: Patients with C1 fracture treated at Kuopio University Hospital Neurosurgery were retrospectively identified from January 1996 to June 2017. C1 fractures were classified according to the AO Spine Upper Cervical and Gehweiler classification systems. Patients were divided into 4 groups based on their treatment: group 1 (underwent C1 surgery as a primary option), group 2 (underwent C1 surgery as a secondary option after initial nonoperative treatment), group 3 (underwent surgery involving the C1 level with main indication being a concomitant cervical spine fracture), and group 4 (C1 fracture treatment was nonoperative)., Results: We identified 47 patients with C1 fracture (mean age, 60.3 ± 18.2 years; 83.0% men; American Society of Anesthesiologists score, 2.3 ± 0.8). Concomitant cervical spine fractures were present in 89.4% of cases, most commonly in the C2 vertebra (75.4%). In group 2, 3 of 5 fractures changed from AO Spine type A to B in control imaging after nonoperative treatment, indicating fracture instability and requiring secondary surgery. Good C1 fracture alignment was achieved for 10 of 10 followed-up patients in groups 1 and 2, and for 10 of 11 followed-up patients in group 3. Residual neck pain and stiffness were present in all groups. Neurologic symptoms were rare and mild., Conclusions: For unstable C1 fractures, surgery is safe treatment with good outcomes. Fractures initially determined as stable may require surgery if alignment is worsened in follow-up imaging. Magnetic resonance imaging is recommended to better detect unstable C1 fractures in diagnostic imaging., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: To introduce a novel transoral instrumentation in the treatment of unstable fractures of the atlas., Methods: From January 2008 to May 2018, 22 patients with unstable C1 fractures who received Jefferson-fracture reduction plate (JeRP) via transoral approach were retrospectively analyzed. The case history and the radiographs before and after surgery were noted. The type of fracture, the reduction of the fracture, and position of the internal fixation were assessed through preoperative and postoperative CT scans., Results: All 22 patients successfully underwent anterior C1-ring osteosynthesis using the JeRP system, with a follow-up of 26.84 ± 9.23 months. Among them, 9 patients had transverse atlantal ligament (TAL) injury, including 3 in Dickman type I and 6 in type II. The preoperative lateral mass displacement (LMD) decreased from 7.13 ± 1.46 mm to 1.02 ± 0.65 mm after the operation. Bone union was achieved in all patients without implant failure or loss of reduction. There were no surgery-related complications, such as wound infection, neurological deficit, or vertebral artery injury. However, atlantoaxial dislocation occurred in 3 patients with Dickman type I TAL injury 3 months postoperatively without any neurological symptoms or neck pain., Conclusions: Transoral C1-ring osteosynthesis with JeRP is an effective surgical strategy to treat unstable atlas fractures with a safe, direct, and satisfactory reduction. The primary indication for the JeRP system is an unstable fracture (Gehweiler type I/III) or/ and TAL injury (Dickman type II)., (© 2021. The Author(s).)

Case: We report a case of a 67-year-old male patient who underwent a C1 laminectomy with laminoplasty at C2-3 because of cervical ossification of the posterior longitudinal ligament. At 6 weeks after surgery, neck pain occurred after minor trauma without neurological deterioration. Computed tomography (CT) demonstrated C1 anterior atlas fracture with a 3-mm gap. After a 3-month brace therapy using a Philadelphia collar, the patient's neck pain disappeared with complete bone union according to the CT., Conclusion: Among 14 cases that were reported previously, none of the adult patients achieved bone union by brace therapy. Therefore, this is the only case report in which bone union could be achieved by brace therapy., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSCC/B582)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

We present a case of a pediatric patient with congenital unfused anterior and posterior arches of the atlas (C1), also known as bipartite atlas, who sustained a traumatic injury during gymnastics. A computed tomography (CT) scan of the cervical spine raised concern for abnormal separation of the midline cleft of the anterior arch of C1. Subsequent magnetic resonance imaging (MRI) showed focal, edema-like signal in the midline cleft of C1. She was advised by neurosurgery to remain in a hard cervical collar for 6 weeks. She recovered after conservative treatment and returned to gymnastics. This case shows that a congenital unfused anterior arch of the atlas identified on CT after cervical trauma should not always be interpreted as an incidental finding. If a superimposed injury is suspected, MRI helps evaluate for traumatic injury, particularly if it is associated with upper cervical pain and tenderness or pain with neck movements. An additional case reiterates our findings.

Atlas assimilation (AA) may be associated with atlantoaxial dislocation, Chiari malformation (CM), and basilar invagination. The importance of AA in the context of craniocervical junction (CVJ) anomalies is unclear. Considering this context, this study's objective is to discuss the role of AA in the management of CVJ anomalies, especially in CM. A comprehensive literature review was performed. In addition, some illustrative cases were discussed on the basis of our review. Finally, we propose a theoretic algorithm to evaluate patients with AA and CM. AA is a proatlas segmentation anomaly that may be complete or incomplete. It may be totally asymptomatic or symptomatic as the result of transferred shifted forces onto the C1-2 joints, leading to clear instability (atlantoaxial dislocation) or mild C1-2 instability. Cautious surgical planning may be required due to associated vertebral artery anomalies. AA with concomitant C2-C3 segmentation failure is highly associated with late C1-C2 instability. CVJ decompression failure was reported in patients with CM and a low clivus canal angle (<130-135 degrees). Patients with assimilated anterior C1 arches usually have evident AAD. CM patients with AA generally have type 1 BI or type 2 BI and are reported with higher rates of CVJ instabilities when compared with those "pure" CM. Dynamic examinations may provide additional evidence of atlantoaxial instability. Although AA per se is not considered an unstable configuration, further and detailed evaluations of patients with CM associated with AA are necessary. Some associated unstable configurations required concomitant CVJ fixation., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Objective: To develop and validate the efficacy of a 3D-printed screw-rod auxiliary system for unstable atlas fractures., Methods: This research is a retrospective analysis, and a total of 14 patients, including 11 males and three females, were enrolled in our hospital from January 2017 to March 2019 who underwent occipitocervical fusion assisted by the 3D-printed screw-rod auxiliary system were reviewed, and with an average age of 53.21 ± 14.81 years, an average body mass index (BMI) of 23.61 ± 1.93 kg/m 2 . The operation time, blood loss and radiation times during the operation were recorded. The maximum fracture displacement values of pre- and post-operation were measured based on CT imaging. All screw grades were evaluated after surgery. The occipital-cervical 2 (O-C 2 ) angle and occipitocervical inclination (OCI) angle of pre-operation, post-operation and the last following-up were measured. The dysphagia scale 3 months after surgery and at the last follow-up, the Neck Disability Index (NDI) 3 months after surgery and at the last follow-up were assessed., Results: All patients were completed the surgery successfully. There was no patient with severe dysphagia or aggravation of nerve injury. The follow-up was from 12 to 14 months, and with an average of 12.5 months. The average surgery time, average blood loss and average radiation times for the 14 patients were 112.14 min, 171.43 mL and 5.07 times, respectively. There was a significant difference in maximum fracture displacement between pre- and post-operation values (P < 0.05). A total of 56 screws were inserted in 14 patients, among them, three screws were classified as grade 1, and the other screws were classified as grade 0. There was a significant difference in the O-C 2 between pre-operation and 3 days after operation (P = 0.002); There was a significant difference in OCI angles between pre-operation and 3 days after operation (P < 0.05); there was no significant difference in the O-C 2 or OCI angle between 3 days after the operation and the last follow-up (P = 0.079; P = 0.201). The dysphagia scales of two patients were assessed as mild at 3 months after surgery, and the others were assessed as normal at 3 months after surgery. All patients' dysphagia scores returned to normal at the last follow-up. The average NDI and average neck Visual Analogue Scale (VAS) scores at the last follow-up were 2.53 and 8.41, respectively., Conclusion: It can objectively restore the OCI to normal with few post-operative complications under the assistance of a screw-rod auxiliary system to perform occipitocervical fusion for unstable atlas fractures and atlantooccipital joint instability., (© 2021 The Authors. Orthopaedic Surgery published by Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.)

Osteoid osteoma is a benign osteoblastic tumor, quite uncommon in the spine. We report a case of an osteoid osteoma involving the atlas in a 6-year-old boy, who presented with suboccipital pain and torticollis. Initial radiological findings were ambiguous as magnetic resonance imaging showed mainly edema of upper cervical soft tissues. The subsequent computed tomography depicted a lesion of left lamina of C1. As conservative treatment failed, the lesion was surgically resected and the patient became pain free. To our knowledge, this is the first case of osteoid osteoma involving the atlas associated with abnormal soft tissue reaction reported in literature., Competing Interests: None., (Thieme. All rights reserved.)

Background: Occipitocervical fusion is an important surgical procedure to treat instability of the upper cervical and craniocervical junction. Fixation to the dense cortical bone of the occiput, contemporaneously typically accomplished with a plate and screws, is known to be strong and durable, but there are many competing methods used to secure an adequate number of fixation points of sufficient strength at the cervical end. Extension of hardware to the midcervical region to acquire additional fixation points, however, results in loss of subaxial motion segments and additional potential morbidity. The C2 vertebra is unique in that its morphology and dimensions permit fixation with longer screws than are typically possible to place in the midcervical lateral masses. Translaminar and pars screw techniques, both commonly used to achieve C2 fixation, are not mutually exclusive, as their respective trajectories are considerably different and engage different portions of the bony anatomy., Methods: We describe a novel, 4-point C2 fixation technique for OC fusion that may avoid the need to extend fusion to the subaxial spine., Results: This technical note illustrates how 4-point C2 fixation can be employed in occiptocervical fusion., Conclusions: 4-point fixation of C2 combining translaminar and pars screw placement is technically feasible and may be a suitable strategy to spare subaxial motion segments in OC fusion procedures. Futher investigation may establish its applicability to additional surgical procedures., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Intraoperative vascular injuries in the cervical spine are rare, but carry significant morbidity and mortality when they do occur. There is a need to better characterize the risk of vertebral artery injury (VAI) after posterior C1-C2 fusion. The aim of this study was to investigate the rate of VAI in patients undergoing posterior C1-C2 cervical fusion., Methods: An electronic database search was performed to identify studies that reported rates of VAI following posterior cervical fusion at C1-C2 level. Patient-specific risk factors, surgical indication, surgical technique, and other data were collected for each study. Forest plots were created to outline the pooled ratios of VAI in the literature., Results: Eleven studies with 773 patients were identified. Mean age of patients was 48.47 years (range, 6-78 years), and most patients were female (61.7%, n = 399). Trauma was the most frequent indication for surgery (18.8%, n = 146), followed by inflammatory processes affecting the vertebrae (13.2%, n = 102). The rate of VAI per patient was 2% (95% confidence interval = 1%-4%) among 773 patients, while injury rate per screw was 1% (95% confidence interval = 0%-2%) among 2238 screws placed., Conclusions: The rate of VAI after C1-C2 posterior cervical fusion was found to be 2% for each operated patient and 1% for each screw placed., (Copyright © 2021 Elsevier Inc. All rights reserved.)

We previously introduced C1 pedicle screw placement to treat C1-2 pathology in a patient with normal vertebral artery anatomy.1 However, we should prepare to meet various anatomic variations. Ponticulus posticus is a bony prominence arising from the posterior arch or the superior articulating process of the atlas that completely or partially encircles the vertebral artery.2 We herein report a 79-yr-old female who presented with myelopathy and was diagnosed with compressive myelopathy at the C1 level in magnetic resonance imaging. A computed tomography showed ponticulus posticus (complete type to the right side) with duplication of vertebral artery.  She underwent surgical treatment of C1-2 pedicle screw placement and reduction of C1 vertebra under a microscopic view. After C1 laminectomy, both-side vertebral arteries were dissected with a microscissor. The mobilization of upper divisions of vertebral artery was identified to secure the entry point and pedicle to insert a C1 pedicle screw. After complete protection of the upper and lower divisions of vertebral artery and identification of pedicle, a C1 pedicle screw was inserted by a freehand technique. We inserted autologous bone chips in the distracted C1-2 facet joint for facet joint fusion, and the C1 vertebra was pulled out by a rod reducer.  After surgery, the patient's symptoms disappeared, and no vertebral artery injury was identified in postoperative 3-dimensional computed tomography angiography.  Patient consent was obtained prior to performing the procedure., (Copyright © 2020 by the Congress of Neurological Surgeons.)

Background: Several bone grafting techniques for posterior atlantoaxial arthrodesis have been reported. The techniques of placing a cancellous morselized bone graft (MBG) on decorticated surfaces of the atlantoaxial complex and securing a structural iliac bone graft (SBG) between C1 and C2 have been used widely. The aim of the present study was to compare the outcomes of these 2 bone grafting techniques for atlantoaxial arthrodesis., Methods: The data from 64 patients with reducible atlantoaxial dislocation treated using posterior C1-C2 screw-rod fixation and fusion were retrospectively reviewed. The MBG technique had been used in 32 patients and the SBG technique in 32 patients. The time required for bone fusion was recorded. The outcomes were evaluated using the Japanese Orthopaedic Association scale score, Neck Disability Index, visual analog scale (VAS) score for neck pain, patient satisfaction, and neck stiffness and compared between the 2 groups. The donor site complications were also compared, and donor site pain was assessed using a VAS., Results: At the final follow-up, the bone fusion rate was 100% in both groups. No significant differences were found in the bone fusion time or donor site pain between the 2 groups (P > 0.05). Postoperatively, The Japanese Orthopaedic Association scale scores, Neck Disability Index, and VAS score for neck pain had improved significantly within both groups (P < 0.05), with no statistically significant differences between the 2 groups (P > 0.05). Additionally, no differences were found between the 2 groups in patient satisfaction and neck stiffness postoperatively (P > 0.05)., Conclusions: The MBG and SBG techniques were both effective for atlantoaxial arthrodesis, with the advantages of reducing the potential risk of catastrophic bleeding of the epidural venous plexus and C2 nerve root injury., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Primary Chiari malformations (CMs) are congenital defects of the skull base and brain. Among the 4 CM types, type I (CM-I) occurs most frequently and may cause somatosensorimotor, autonomic and vision symptoms. Presently, posterior fossa decompression alone (PFD) or with duraplasty (PFDD) and cerebellar tonsil (CbT) shrinkage tactics are standard treatments, albeit inherent issues. There has been no report on devising CbT suspension (CTS) to manage CM-I., Objectives: 1) To design a CTS protocol that can be used with CbT coagulation (CTC) and PFDD; 2) to evaluate the regimen for feasibility, safety, and efficacy in a retrospective study; and 3) to obtain data for planning prospective studies to validate PFDD + CTC + CTS as a novel approach to treating adult CM-I., Methods: PFDD + CTC + CTS (n = 17), PFDD + CTC (n = 13), and PFDD (n = 12) were performed for 42 adult patients (age range, 18-55 years; female:male = 27:15) following a balanced study design. Neck Disability Index (NDI), Chicago Chiari Outcome Scale (CCOS), and /magnetic resonance imaging/computed tomography were used to determine postsurgery outcomes for approximately 20 months., Results: Comparing to PFDD + CTC or PFDD, patients receiving PFDD + CTC +CTS operation exhibited significantly improved group average NDI (10.72 ± 3.95%; P = 0.007), CbT elevation distance (7.06 ± 2.42 mm; P < 0.001, Kruskal-Wallis test; 55.7 ± 25.4% higher than the presurgery level; P < 0.001, analysis of variance), and syringomyelia syrinx retraction (P = 0.009, analysis of variance)., Conclusions: The PFDD + CTC + CTS regimen appeared to be safe and potentially more efficacious in patients with CM-I evaluated for the period, relative to PFDD + CTC or PFDD treatment. Future prospective studies were warranted., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Purpose: The purpose of this study was to gain new insights into the epidemiologic characteristics of patients with atlas fractures and to retrospectively evaluate complication rates after surgical and non-surgical treatment., Methods: In a retrospective study, consecutive patients diagnosed with a fracture of the atlas between 01/2008 and 07/2018 were analyzed. Data on epidemiology, concomitant injuries, fracture patterns and complications were obtained by chart and imaging review., Results: In total, 189 patients (mean age 72 years, SD 19; 57.1% male) were treated. The most frequent trauma mechanism was a low-energy trauma (59.8%). A concomitant injury of the cervical spine was found in 59.8%, a combined C1/C2 injury in 56.6% and a concomitant fracture of the thoraco-lumbar spine in 15.4%. When classified according to Gehweiler, there were: 23.3% type 1, 22.2% type 2, 32.8% type 3, 19.0% type 4 and 1.1% type 5. Treatment of isolated atlas fractures (n = 67) consisted of non-operative management in 67.1%, halo fixation in 6.0% and open surgical treatment in 26.9%. In patients with combined injuries, the therapy was essentially dictated by the concomitant subaxial cervical injuries., Conclusions: Atlas fractures occurred mainly in elderly people and in the majority of the cases were associated with other injuries of the head and spine. Most atlas fractures were treated conservatively. However, surgical treatment has become a safe and valid option in unstable fracture patterns involving the anterior and posterior arch (type 3) or those involving the articular surfaces (type 4)., Level of Evidence: IV (Retrospective cohort study). These slides can be retrieved under Electronic Supplementary Material.

Background: C1-ring osteosynthesis is a valid alternative to posterior C1-C2 or C0-C2 fusion to preserve important C1-C2 motion in the treatment of unstable atlas fractures. Nevertheless, the fixation instruments used in current studies for transoral anterior C1-ring osteosynthesis were not suitable for anterior anatomy of the atlas or did not have reduction mechanism. We therefore present this report to investigate preliminary clinical effects of transoral anterior C1-ring osteosynthesis using a laminoplasty plate in unstable atlas fractures., Methods: From January 2014 to December 2017, 13 patients with unstable atlas fractures were retrospectively reviewed. All patients were treated with transoral anterior C1-ring osteosynthesis using a laminoplasty plate. Pre- and postoperative images were obtained to assess reduction of the fracture, internal fixation placement, and bone union. Neurological function, range of motion, and pain levels were evaluated clinically on follow-up., Results: The surgeries were successfully performed in all cases. The average follow-up duration was 16.6 ± 4.4 months (range 12-24 months). One patient suffered screw loosening after operation and underwent replacement operation subsequently. Satisfactory clinical outcomes were achieved in all patients with ideal fracture reduction, reliable plate placement, well-preserved range of motion, and neck pain alleviation. All patients achieved bone union of fractures without loss of reduction or implant failure or C1-C2 instability during the follow-up. No vascular or neurological complication was noted during the operation and follow-up., Conclusions: Transoral anterior C1-ring osteosynthesis using a laminoplasty plate is a effective surgical treatment for unstable atlas fractures. This technique has a ingenious reduction mechanism, and can provide satisfactory bone union and preservation of C1-C2 motion.

Background: We herein outline the experience matured in our equipped Cranio-Vertebral Junction Laboratory for anatomic dissection., Methods: An extreme lateral approach (ELA) was performed on 4 fresh cadavers and submandibular approach was performed on 5. An endoscope and navigation-assisted far lateral approach (FLA) was performed in 5 injected specimens. In these specimens, a transoral approach was also performed, as well as a neuronavigation-assisted comparison between transoral and transnasal explorable distances., Results: As calculated with neuronavigation, statistically significant differences both in the explored craniocaudal (P = 0.003) and lateral (P = 0.008) distances were observed between the transoral approach and endoscopic endonasal approach. In FLA, neuronavigation facilitated identification and partial removal of the occipital condyle; in one case, during endoscopic intradural exploration, tearing of the emerging roots of the 11th cranial nerve occurred. In ELA, the site where the accessory nerve pierces into the sternocleidomastoid muscle was found at a distance from the tip of the mastoid between 3 and 4 cm., Conclusions: During dissections, as in the clinical setting, endoscope and image guidance give the surgeon a constant orientation, increasing the accuracy and the safety of the approach. Nonetheless, the encumbrance of the endoscope could represent a limit in deep and narrow corridors as those running across the craniovertebral junction, especially in "oblique" FLA and ELA, in which the surgical target is often hidden by a delicate tangle of nerves and vessels. Its use appears more suitable and safer in "straight" approaches as transoral and transnasal in which there are no neurovascular structures interposed., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: To summarize the progress in treatment of unstable atlas fracture, the existing problems, and the research direction., Methods: Related literature at home and abroad was reviewed. The stability evaluation of atlas fracture and treatment methods were introduced, and the selection of surgical approach and fixation instruments in treatment of unstable atlas fracture were summarized and analyzed., Results: At present, atlas fractures are considered as unstable fractures except single anterior arch fractures with complete transverse ligament or simple posterior arch fractures. The treatment of unstable atlas fracture has been developed from nonsurgical treatment and traditional fusion surgery to single-segment fixation. Nonsurgical treatment is less effective, while traditional fusion surgery has a disadvantage of limited the motion of the upper cervical spine. Single-segment fixation can not only restore and fix the fracture, but also preserve the upper cervical motion function. Single-segment fixation approaches include posterior and transoral approaches, and the fixation instruments are being constantly improved, mainly including screw-rod system, screw-plate system, and plate system., Conclusion: For unstable atlas fracture, single-segment fixation is an ideal surgical method, and has more advantages when compared with nonsurgical treatment and traditional fusion surgery. Single-segment fixation via transoral approach is more direct for atlas anterior arch fracture reduction, but there is a high risk of infection; and single-segment fixation via posterior approach is less effective for the reduction of atlas anterior arch fracture. Therefore, a better reduction method should be explored.

Background/objective: Atlantoaxial fusion procedures may be difficult in situations such as high-riding vertebral artery, a narrow C2 pedicle, and the presence of ponticulus posticus-arcuate foramen. With respect to vertebral artery (VA) anomalies, persistent first intersegmental artery, extracranial origin of the posterior inferior cerebellar artery at the C1-C2 level, and fenestration of the VA are all major risk factors for VA injury in C1-C2 fusion surgeries., Methods: To safeguard the VA, we designed the unilateral fusion procedure (all screws lie in the ipsilateral side, either the right side or left side): a unilateral transarticular screw combined with an ipsilateral-side C1 posterior arch screw and a C2 laminar screw (LS), with both C1-C2 screws inserted from opposite side, although the trajectory will be on the same side. In addition to atlantoaxial stabilization with screws and rod, autograft bony fusion was performed on the same side as modified Brook's procedure and augmented with sublaminar tapping., Results: We present a series of 3 cases operated for odontoid fracture with associated high risk for fusion on one side alone. The fact that the chance of VA injury is high in transarticular screw, in lateral mass screw, less in pars screw, and pedicle screw is well known. Alternate screw placement to avoid VA injury would be a posterior arch screw for C1 and laminar screw for C2, which was adopted in our technique., Conclusions: We combined a unilateral transarticular screw and modified Brook's procedure with sublaminar tapping for additional augmentation of fusion. We would like to highlight this C1 posterior arch screw as an alternative procedure for atlantoaxial fusion., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Chiari I malformation (CIM) is a disorder characterized by caudal displacement of the cerebellar tonsils below the foramen magnum. It is often associated with syringomyelia and occasionally with hydrocephalus. CIM is commonly treated by posterior fossa decompression with or without removal of the posterior arch of C1 and duraplasty, but the treatment for infants with symptomatic CIM is not well established. We present a case of symptomatic CIM in an infant that was successfully treated with a ventriculoperitoneal shunt (VPS) and discuss the importance of the pathophysiology in management decisions., Case Description: A 6-month-old male with a CIM and a cervicothoracic syrinx presented with stridor, lower cranial nerve dysfunction, and increased tone that worsened with crying. Magnetic resonance imaging studies revealed cerebellar tonsillar displacement extending to the level of C3-C4 with a syrinx extending from C4 to T4. In addition, there was compression of the cervicomedullary junction, fourth ventricular outflow obstruction, and obstructive hydrocephalus. The decision was made to place a ventriculoperitoneal shunt (VPS) instead of performing decompressive surgery as the initial treatment intervention. The infant had significant symptomatic relief at 6-, 9-, and 12-month follow-ups. Postoperative magnetic resonance imaging at 6-month follow-up revealed resolution of the syrinx and ventriculomegaly and ascent of the cerebellar tonsils., Conclusions: Ventriculoperitoneal shunting alone was successfully used to treat an infant with concurrent CIM, syrinx, and hydrocephalus. This case underscores not only the importance of hydrocephalus as the pathogenesis of CIM in some cases but also the possibility of avoiding the morbidity of decompressive surgery in infants., (Copyright © 2020 Elsevier Inc. All rights reserved.)

At present, the posterior cervical approach with open reduction and internal fixation (ORIF) remains a commonly effective treatment for unstable Atlas fracture. However, the inserted screws into the C1 lateral mass of some unstable atlas fracture are very difficult, so that the operation is forced to change into C0 to C2 fusion. In order to improve the successful rate of lateral mass screw placement, we introduced a method of fixing lateral mass with a towel clamp in posterior transpedicular fixation, and explore the efficacy and feasibility.Twenty-one consecutive patients with unstable atlas fracture were treated via this method from October 2012 to July 2017. All cases had neck pain and restricted motion of neck movement on admission. Electronic medical records and pre- and postoperative radiographs were reviewed. Screw and rod placement, bone fusion, and spinal cord integrity were assessed via long-term follow-up with anteroposterior and lateral radiographs and computed tomography. Follow-up included clinical assessment of neurological function, assessment of pain using the visual analog scale (VAS), and assessment of the activities of daily living using the neck disability index (NDI).The mean follow-up duration was 22.1 months (range: 12-54 months). No screw loosening or breakage, plate displacement, neurovascular injury, and severe complications occurred during follow-up. The mean operative time was 112.4 ± 14.9 min (range: 82-135 min), and mean blood loss was 386.2 ± 147.9 mL (range: 210-850 mL). One patient experienced continuous neck pain postoperatively, but this gradually disappeared with analgesic administration. At final follow-up, all patients had bone fusion, the VAS scores and NDI were significantly improved compared with preoperatively.Fixing the C1 lateral mass with a towel clamp during posterior transpedicular fixation for unstable atlas fracture appears to be a safe and reliable method, with the advantages of being a simple technique with few complications.

Background: Atlantoaxial spine surgery is a challenge to spinal surgeons because of its proximity to neurovascular structures. This study aimed to identify and analyze the scientific publications in atlantoaxial spine surgery from different countries and institutions., Methods: Clarivate Analytics Web of Science was used to search all articles for information on atlantoaxial spine surgery. The annual research, countries, journals, authors, institutions, citation frequency, and journal metrics were extracted. These results from countries and hotspots (keywords in publications) were subjected to co-occurrence analysis using VOSviewer, after which the top 100 most-cited articles were analyzed further., Results: A total of 3161 articles were included. A trend toward an increasing number of publications on atlantoaxial spine surgery in recent years was evident. Among all countries, the United States contributed the most publications. Seth Gordhandas Sundarda Medical College had the highest number of publications among institutions. Among all research categories, fixation and fusion were the most common areas discussed. The screw-rod system described in the most-cited article (cited 823 times) appeared to be the most popular fixation method. With the development of C1 and C2 screw technology, the screw-rod system is becoming increasingly popular., Conclusions: The atlantoaxial spine surgery literature has grown continuously in recent years. The United States is the largest contributor in this field. Fixation and fusion are the most common areas, and fixation-related studies should be closely followed. The screw-rod fixation system is becoming increasingly popular., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: There are few studies reporting the use of atlantoaxial pedicle screws and the long-term effects of C1-C2 posterior fusion in children. Our study is to investigate the initial results of C1-C2 pedicle screw fixation for pediatric atlantoaxial dislocation (AAD) and assessed spontaneous change of postoperative radiography after a long-term follow-up period., Methods: Posterior pedicle screw fixations were performed in 21 pediatric patients with AAD. All the patients underwent implant removal 1 year after their initial surgery and had regular follow-up with an average duration of 76.4 months (range, 52 to 117 mo). Clinical and radiographic data were then collected and compared., Results: Frankel Grade was significantly improved at 3 months follow-up compared with pretreatment values. All patients had good bony fusion at a mean of 4.2±0.9 months (range, 3 to 6 mo) after treatment. None of the patients experienced worsening neurological symptoms or injury to the vertebral artery. However, 2 cases experienced minor complications. Following removal of the implants, no spinal deformities or subaxial instabilities were found. The mean angle of sagittal curvature increased from 12.1±2.4 degrees (range, 0 to 22 degrees) immediately postoperatively to 19.1±2.7 degrees (range, 6 to 31 degrees) at the final follow-up (P>0.05)., Conclusions: The results demonstrated that C1-C2 pedicle screw fixation could achieve satisfactory initial results for the management of the pediatric AAD. Moreover, removal of the metal implant after bony fusion did not increase the risk of spinal deformity or subaxial instability at long-term follow-up.

Background: The C1 lateral mass and C2 pedicle screw with rod fixation system has been used commonly in recent years. Despite the numerous reports on this technique in the literature, there are no studies regarding the effect of the angle of the rod used. We investigated the effect of rod angle on subaxial lordosis, cervical sagittal balance, and pain scores., Methods: Clinical records and radiologic images of 58 patients who underwent procedures between 2011 and 2016 at our clinic were assessed retrospectively. We recorded clinical findings, visual analog scale (VAS) scores, angles of cervical and segmental lordosis, and the distance between the C2 sagittal vertical axis (SVA) and the C7 posterior-superior corner., Results: A total of 36 male and 22 female patients were enrolled. A negative correlation was found between the C1-C2 lordosis angle and the C2-C7 lordosis angle irrespective of surgical technique. In patients who were operated on using 30°-angled rods, there was a postoperative increase in C1-C2 lordosis degree and an improvement in C2 cervical SVA values. Postoperative month 6 VAS scores were significantly better in the patients who were operated on with angled rods compared with those who received straight rods., Conclusions: We believe this is because of the positive effect of the angled rod on sagittal balance. Nevertheless, prospective case-control studies should be conducted with larger groups of subjects. Furthermore, every patient should be evaluated considering the whole spinal sagittal balance., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The C1 lateral mass screw (LMS) is widely used as one of the screws for atlantoaxial fixation. Tight bicortical screwing from the posterior to anterior cortical margin of the atlas is recommended. However, important structures, such as the internal carotid artery, are located around this area so precision is required to avoid injuring them. We describe the usefulness of a new electronic conductivity device (ECD) with a pedicle probe and a multi-axis angiography unit for inserting the C1 LMS. Four consecutive patients who were treated with C1 and C2 posterior fixation using an ECD and a multi-axis angiography unit in the hybrid operating room were included. All patients were treated successfully. Seven of eight bicortical screws could be inserted into the perfectly ideal location. The median (interquartile range) distance from the anterior margin of the atlas to the tip of the screw was 0.81 mm (0.43, 1.21 mm). This study suggested that the ECD and multi-axis angiography unit are useful for inserting the C1 LMS safely and tightly.

Rationale: To our knowledge, this is the first report of traumatic combined vertical atlanto-occipital dislocation (AOD) and atlanto-axial dislocation (AAD) with 2-part fracture of the atlas., Patient Concerns: The first case was of a 31-year-old woman admitted to the emergency room comatose after a traffic accident. The second case was of a 21-year-old woman admitted to the emergency room comatose after a fall., Diagnoses: Traumatic combined vertical AOD and AAD with 2-part fractures of the atlas was diagnosed using plain radiography, 2-dimensional computed tomography, and/or magnetic resonance imaging of the cervical spine., Intervention: The first patient received immediate intubation and cardiopulmonary resuscitation in the emergency room. The second patient also received immediate intubation in the emergency room. After her vitals stabilized, she underwent occipitocervical fusion with instrumentation., Outcomes: The first patient died 2 days after the accident. The second patient remained quadriplegic in a ventilatory-dependent state at 1 year after surgery. She continues to receive comprehensive rehabilitation., Lessons: Immediate respiratory support and surgical stabilization are important for saving lives in this kind of extremely unstable and fatal complex upper cervical spine injury.

Background: Although C1 screw fixation is becoming popular, only a few studies have discussed about the risk factors and the patterns of C1 screw complications., Objective: To investigate the incidence of C1 screw complications and analyze the risk factors of the C1 screw complications., Methods: A total of 358 C1 screws in 180 consecutive patients were analyzed for C1 screw complications. Screw malposition, occipital neuralgia, major complications, and total C1 screw complications were analyzed., Results: The distribution of C1 screw entry point is as follows: inferior lateral mass, 317 screws (88.5 %); posterior arch (PA), 38 screws (10.7 %); and superior lateral mass, 3 screws (0.8 %). We sacrificed the C2 root for 127 screws (35.5 %). C1 instrumentation induced 3.1 % screw malposition, 6.4 % occipital neuralgia, 0.6 % vascular injury, and 3.4 % major complications. In multivariate analysis, deformity (odds ratio [OR]: 2.10, P = .003), traumatic pathology (OR: 4.97, P = .001), and PA entry point (OR: 3.38, P = .001) are independent factors of C1 screw malposition. C2 root resection can decrease the incidence of C1 screw malposition (OR: 0.38, P = .012), but it is a risk factor of occipital neuralgia (OR: 2.62, P = .034). Advanced surgical experience (OR: 0.09, P = .020) correlated with less major complication., Conclusion: The incidence of C1 screw complications might not be uncommon, and deformity or traumatic pathology and PA entry point could be the risk factors to total C1 screw complications. The PA screw induces more malposition, but less occipital neuralgia. C2 root resection can reduce screw malposition, but increases occipital neuralgia., (Copyright © 2019 by the Congress of Neurological Surgeons.)