The role of clivus and atlanto-occipital lateral mass height in basilar invagination with or without atlas occipitalization.

Basilar invagination (BI) is a common deformity. This study aimed to quantitatively evaluate the height of clivus and atlanto-occipital lateral mass (LM) in patients with BI with or without atlas occipitalization (AOZ). We evaluated 166 images of patients with BI and of controls. Seventy-one participants were control subjects (group A), 68 had BI with AOZ (group B), and 27 had BI without AOZ (group C). Parameters were defined and measured for comparisons across the groups. Multiple linear regression analysis was used to test the relationship between Chamberlain's line violation (CLV) and the clivus height ratio or atlanto-occipital LM height. Based on the degree of AOZ, the lateral masses in group B were classified as follows: segmentation, incomplete AOZ, complete AOZ. From groups A to C, there was a decreasing trend in the clivus height and clivus height ratio. There was a linear negative correlation between the clivus height ratio and CLV in the three groups. Generally, the atlanto-occipital LM height followed the order of group B < group C < group A. The atlanto-occipital LM height was included only in the equations of groups B. There were no cases of atlantoaxial dislocation (AAD) in group C. There was a decreasing trend in LM height from the segmentation type to the complete AOZ type in group B. BI can be divided into three categories: AOZ causes LM height loss; Clivus height loss; Both clivus and LM height loss. The clivus height ratio was found to play a decisive role in both controls and BI group, while the atlanto-occipital LM height loss caused by AOZ could be a secondary factor in patients with BI and AOZ. AOZ may be a necessary factor for AAD in patients with congenital BI. The degree of AOZ is associated with LM height in group B.

An exclusionary screening method based on 3D morphometric features to sort commingled atlases and axes.

In forensic commingled contexts, when the disarticulation occurs uniquely at the atlantoaxial joint, the correct match of atlas and axis may lead to the desirable assembly of the entire body. Notwithstanding the importance of this joint in such scenarios, no study has so far explored three-dimensional (3D) methodologies to match these two adjoining bones. In the present study, we investigated the potential of re-associating atlas and axis through 3D-3D superimposition by testing their articular surfaces congruency in terms of point-to-point distance (Root Mean Square, RMS). We analysed vertebrae either from the same individual (match) and from different individuals (mismatch). The RMS distance values were assessed for both groups (matches and mismatches) and a threshold value was determined to discriminate matches with a sensitivity of 100%. The atlas and the corresponding axis from 41 documented skeletons (18 males and 23 females), in addition to unpaired elements (the atlas or the axis) from 5 individuals, were superimposed, resulting in 41 matches and 1851 mismatches (joining and non-joining elements). No sex-related significant differences were found in matches and mismatches (p = 0.270 and p = 0.210, respectively), allowing to pool together the two sexes in each group. RMS values ranged between 0.41 to 0.77 mm for matches and between 0.37 and 2.18 mm for mismatches. Significant differences were found comparing the two groups (p < 0.001) and the highest RMS of matches (0.77 mm) was used as the discriminative value that provided a sensitivity of 100% and a specificity of 41%. In conclusion, the 3D-3D superimposition of the atlanto-axial articular facets cannot be considered as a re-association method per se, but rather as a screening one. However, further research on the validation of the 3D approach and on its application to other joints might provide clues to the complex topic of the reassociation of crucial adjoining bones.

Análisis de la Distancia entre Hueso Occipital y Atlas en Telerradiografía Lateral de Cráneo / Analysis of the Distance Between the Occipital Bone and Atlas in Lateral Cephalograms

El conocimiento del espacio suboccipital (OA) es esencial para el clínico debido a que su disminución se asocia a posible causa de cefaleas. El objetivo de este estudio fue determinar las diferencias entre la longitud del espacio suboccipital en telerradiografías laterales entre hombres y mujeres de distintos rangos etarios. En este estudio transversal se analizaron un total de 371 telerradiografías laterales de cráneo. Se realizó estadística descriptiva y la aplicación de prueba T-Student y ANOVA para evaluar la asociación entre el espacio suboccipital con el género y la edad. La distancia media del espacio suboccipital fue de 5.62 ± 2.7 mm, siendo mayor en hombres que en mujeres (6.49 ± 2.8 mm y 5.09 ± 2.5 mm respectivamente, p<0.001). Con respecto a la edad, la distancia del espacio suboccipital no presentó variaciones significativas. La longitud del OA entre los hombres y mujeres de distintos grupos tampoco mostró diferencias significativas. Existe una gran variabilidad en la distancia del espacio suboccipital, el cual se observa más disminuido en mujeres, por lo que se sugiere un análisis individual mediante telerradiografía lateral frente a pacientes con cefaleas.

SUMMARY: Knowledge of the suboccipital space (OA) is essential for clinicians because its decrease is associated with headache. The aim of this study was to determine the differences in the length of the suboccipital space in lateral cephalograms of men and women of different age ranges. In this cross-sectional study, a total of 371 lateral cephalograms were analyzed. Descriptive statistics and the application of Student's t-test and ANOVA were performed to evaluate the association between the suboccipital space with sex and age. The mean distance of the suboccipital space was of 5.62 ± 2.7 mm, being higher in men than women (6.49 ± 2.8 mm and 5.09 ± 2.5 mm respectively, p < 0.001). Regarding age, the distance of the suboccipital space did not show significant variations. The length of the OA between men and women of different age groups also showed no significant differences. There is a great variability in the distance of the suboccipital space, which is observed to be more decreased in women; therefore, an individual analysis by lateral cephalograms is suggested in patients with chronic headaches.

The telovelar approach for fourth ventricular tumors in children: is removal of the posterior arch of C1 necessary?

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.

Computed Tomography-Guided Radiofrequency Ablation for Glossopharyngeal Neuralgia: Comparison of Cervical Computed Tomography Angiography, Transverse Process of Atlas, and Styloid Process Localization to Styloid Process Localization Alone.

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.

The role of occipital condyle and atlas anomalies on occipital cervical fusion outcomes in Chiari malformation type I with syringomyelia: a study from the Park-Reeves Syringomyelia Research Consortium.

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.

Direct osteosynthesis in the treatment of atlas burst fractures: a systematic review.

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.

Pediatric atlas anatomy and its implications for fracture treatment: an anatomical and radiological study.

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.

Frecuencia de Ponticulus posticus en Telerradiografías Laterales de Cráneo / Frequency of Ponticulus posticus in Digital Lateral Cephalograms

En el arco posterior del atlas se describe una variación de tejido óseo denominada Ponticulus posticus (PP), la cual se ha relacionado con el desarrollo de dolor cervical. El objetivo de este estudio fue determinar la frecuencia de PP en telerradiografías laterales digitales. Este estudio correspondió a un estudio observacional descriptivo, donde se analizaron 450 telerradiografías laterales digitales obtenidas de la base de datos del Servicio de Imagenología Oral y Maxilofacial de la Facultad de Odontología de la Universidad Andrés Bello, Viña del Mar, Chile. Se analizó la presencia de PP en cada cefalograma, y se utilizó la clasificación de Cederberg y Stubbs para determinar los grados de osificación. Se aplicó la prueba de Chi-cuadrado para establecer una asociación entre la presencia de PP con el sexo y la edad. De las 450 telerradiografías laterales el 42,4 % presenta PP, con una mayor prevalencia entre el rango de 21-40 años. En cuanto al grado de osificación, el grado 2 fue el tipo más prevalente (25 %), seguido del grado 4 (9,5 %), el grado 3 (8 %). No se encontró asociación entre la presencia de PP con edad y género (P > 0,05). La PP es frecuente en la población y se observa a diferentes edades sin predilección por sexo.

SUMMARY: A bony tissue variation called Ponticulus posticus (PP) is described in the posterior arch of the atlas, which has been associated with the development of cervical pain. The aim of this study was to determine the frequency of PP in digital lateral cephalograms. This study was an observational descriptive study, in which 450 digital lateral cephalograms obtained from the database of the Oral and Maxillofacial Imaging Service of the Faculty of Dentistry of the Andrés Bello University, Viña del Mar, Chile, were analyzed. The presence of PP was analyzed in each cephalogram, and the Cederberg and Stubbs classification was used to determine the degrees of ossification. The Chi-square test was applied to establish an association between the presence of PP with gender and age. Of the 450 lateral cephalograms, 42.4 % presented PP, with a higher prevalence in the 21-40 year range. In terms of the degree of ossification, grade 2 was the most prevalent type (25 %), followed by grade 4 (9.5 %), and grade 3 (8 %). No association was found between the presence of PP with age and gender (P > 0.05). PP is common in the population and is observed at different ages without a sex preference.

Ponticulus Posticus: An Important Diagnostic Finding Often Missed in Lateral Cephalograms.

AIM: The purpose of the current study was to investigate the presence of the ponticulus posticus (PP) frequently encountered in lateral cephalograms. MATERIALS AND METHODS: About 500 patients of age 12-40 years were selected whose digital lateral cephalogram was recorded and traced to confirm the presence of the PP and categorize as: (A) Absent, as evidenced by lateral cephalograms. (B) Complete PP evidenced by the presence of circumferential bone bridge that connected the upper articular process to the atlas's posterior arch. (C) Partial PP: presented as a bone spike that protruded from the top articular process or the posterior arch of the atlas and extended above the vertebral artery sulcus. Symptoms of migraine, shoulder discomfort, orofacial pain, and headache were also evaluated on interaction with the patients. Using the Chi-square test, the relationship between the patient's gender and the presence of the PP was assessed. A p-value of 0.05 or less was regarded as statistically significant. RESULTS: About 10% of the patients reported with the presence of complete variant, 70% with partial variant and rest 20% of patients with neither a partial nor a complete form of PP. There was no statistically significant association between the PP and gender, as indicated by the Chi-square values (3.146; p = 0.526). CONCLUSION: On conclusion, according to the findings of the current study, patients with a complete form of PP experience more symptoms than those with a partial form of PP. In both groups, the PP frequency was higher in females. CLINICAL SIGNIFICANCE: In lateral cephalograms, the cervical spine region is typically ignored and given little weight. A common variation of atlas vertebrae is the PP, which is located in the posterior arch of the atlas. The PP exacerbates symptoms, such as migraine, tension headaches, shoulder pain, double vision, vertigo, stroke, and pain in the neck and orofacial region. Therefore, orthodontic specialists serve as initial diagnosticians and direct the patients to qualified physicians so that they can experience symptom relief.

Systematic review and meta-analysis of the prevalence of the retrotransverse foramen of the atlas.

The retrotransverse foramen (RTF) is a nonmetric variant of the atlas vertebra that can accommodate an anastomotic vertebral vein and occipital nerve. An understanding of this variation and its occurrence is crucial, as it could aid in explanation of the unidentified cause of the high prevalence of variability in this region. The aim of this meta-analysis was to obtain data on the prevalence of the RTF and its variations according to anatomy, sex, and ethnicity. A large-scale search was conducted through the major online databases to establish and determine the pool of studies reporting data relevant to the RTF. No date or language restrictions were applied. The data collection was categorized by prevalence, type (incomplete/complete), side, sex, ethnicity, laterality, and diameter. A total of 17 studies (n = 1979 subjects) were incorporated into our analysis. The overall pooled prevalence for a complete RTF was 11.4% and the overall pooled prevalence of an incomplete (partial) RTF was 9.6%. A complete RTF was most prevalent in Africa (Sub-Saharan population) (12.1%), followed by Europe (11.8%) and Asia (9.7%). As this variant occurs in a significant number of patients in all of the aforementioned populations, recognition, and awareness, especially with thorough investigation with computer tomography angiography (CTA) should be implemented, as it is the only possible way to visualize the possible contents of RTF.

Frequency and Type of Ponticulus Posticus and Lateralis in a Chinese Population: A CT-Based Analysis of 4047 Cases.

AIM: To investigate the prevalence and type of ponticulus posticus (PP) and ponticulus lateralis (PL) in the Chinese population by analyzing computed tomography (CT) scans, and to uncover the pathogenesis of PP and PL. MATERIAL AND METHODS: A total of 4,047 cases were included in this study. We evaluated cervical spine CT scans with three dimensional reconstructions and collected age, gender, and presence of PP and PL in each case. If either or both were present, location and type were recorded. RESULTS: The overall prevalence of PP was 8.01%. The age of patients with PP was significantly higher than those without. Men had a higher prevalence of PP than women. The presence of PP was more common on the left side than the right. According to our previous classification, the most common type of a PP was AC (32.41%), followed by CC (20.06%) and CA (16.98%). The overall prevalence of PL was 4.67%, with no differences between age groups, genders or by location. The most common type of PL was AC (43.92%), followed by CA (35.98%) and CC (20.11%). The prevalence of PP and PL occurring in the same patient was 1.26%. CONCLUSION: Based on cervical spine CT scans of 4,047 Chinese patients, we found that the prevalence of PP and PL were 8.01% and 4.67%, respectively. PP was more common in older patients, which strongly suggests that PP may be a congenital osseous anomaly of the atlas that mineralizes during aging.

Radiologic Features of Atlas Occipitalization and Its Clinical Implications.

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.

Posterior osteosynthesis with a new self-designed lateral mass screw-plate system for unstable atlas burst fractures.

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.

Morphometric analysis of dry atlas vertebrae in a northeastern Thai population and possible correlation with sex.

PURPOSE: The uppermost segment of the cervical vertebra or atlas (C1) is a critically important anatomical structure, housing the medulla oblongata and containing the grooves for the C1 spinal nerve and the vertebral vessels. Variations of the C1 vertebra can affect upper spine stability, and morphometric parameters have been reported to differ by population. However, there are few data regarding these parameters in Thais. The use of this bone to predict sex and age has never been reported. METHODS: This study aimed to examine C1 morphometry and determine its ability to predict sex. Twelve diameter parameters were taken from the C1 vertebrae of identified skeletons (n = 104, males [n, 54], females [n, 50]). Correlation analysis was also performed for sex and age, which were predicted using machine learning algorithms. RESULTS: The results showed that 8 of the 12 measured parameters were significantly longer in the male atlas (p < 0.05), while the remaining 4 (distance between both medial-most edges of the transverse foramen, transverse dimension of the superior articular surface, frontal plane passing through the canal's midpoint, and anteroposterior dimension of the inferior articular surface) did not differ significantly by sex. There was no statistically significant difference in these parameters on the lateral side. The decision stump classifier was trained on C1 parameters, and the resulting model could predict sex with 82.6% accuracy (root mean square error = 0.38). CONCLUSION: Assertation of the morphometric parameters of the atlas is important for preoperative assessment, especially for the treatment of atlas dislocation. Our findings also highlighted the potential use of atlas measurements for sex prediction.

Biomechanical analysis of odontoid and transverse atlantal ligament in humans with ponticulus posticus variation under different loading conditions: Finite element study.

PURPOSE: Ponticulus posticus (PP) is a variation of the bone bridge that appears in the first cervical vertebra and through which the vertebral artery passes. Odontoid fractures are common spinal bone fractures in older people. This study aims to investigate the effect of neck movements on the odontoid and transverse atlantal ligament (TAL) of people with PP variation from a biomechanical view. METHOD: C1, C2, and C3 vertebrae of the occipital bone were analyzed using the finite element method (FEM). In this study, solid models were created with the help of normal (N), incomplete (IC), and asymmetric complete (AC) PP tomography images. The necessary elements for the models were assigned, and the material properties were defined for the elements. As boundary conditions, models were fixed from the C3 vertebra, and 74 N loading was applied from the occipital bone. Stress and deformation values in the odontoid and transverse atlantal ligament were obtained by applying 1.8 Nm moment in flexion, extension, bending, and axial rotation directions. RESULTS: The stress and deformation values of all three models in odontoid and TAL were obtained, and numerical results were evaluated. In all models, stress and deformation values were obtained in decreasing order in rotation, bending, extension, and flexion movements. The highest stress and strain values were obtained in AC and the lowest values were obtained in N. In all movements of the three models, the stress and deformation values obtained in the TAL were lower than in the odontoid. CONCLUSION: The greatest stresses and deformations obtained in spines (AC) with PP were found in the odontoid. This may help explain the pathogenesis of odontoid fractures in older people. First, this study explains the mechanism of the formation of neck trauma in people with PP and the need for a more careful evaluation of the direction of impact. Secondly, the study reveals that the rotational motion of the neck independent of PP has more negative effects on the odontoid.

Atlas (C1) lateral mass screw placement using the intersection between lateral mass and inferomedial edge of the posterior arch: a cadaveric study.

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.

Risk Factors for Fracture Nonunion and Transverse Atlantal Ligament Injury After Isolated Atlas Fractures: A Case Series of 97 Patients.

BACKGROUND: The management of atlas fractures is controversial and hinges on the integrity of transverse atlantal ligament (TAL). OBJECTIVE: To identify risk factors for atlas fracture nonunion, with and without TAL injury. METHODS: All isolated, traumatic atlas fractures treated at our institution between 1999 and 2016 were analyzed. Multivariable logistic regression was used to identify variables associated with TAL injury confirmed on MRI, occult TAL injury seen on MRI but not suspected on computed tomography (CT), and with fracture nonunion on follow-up CT at 12 weeks. RESULTS: Lateral mass displacement (LMD) ≥ 7 mm had a 48.2% sensitivity, 98.3% specificity, and 82.6% accuracy for identifying TAL injury. MRI-confirmed TAL injury was independently associated with LMD > 7 mm ( P = .004) and atlanto-dental interval ( P = .039), and occult TAL injury was associated with atlanto-dental interval ( P = .019). Halo immobilization was associated with having a Gehweiler type 3 fracture ( P = .020), a high-risk injury mechanism ( P = .023), and an 18.1% complication rate. Thirteen patients with TAL injury on MRI and/or LMD ≥ 7 mm were treated with a cervical collar only, and 11 patients (84.6%) healed at 12 weeks. Nonunion rates at 12 weeks were equivalent between halo (11.1%) and cervical collar (12.5%). Only age independently predicted nonunion at 12 weeks ( P = .026). CONCLUSION: LMD > 7 mm on CT is not sensitive for TAL injury. Some atlas fractures with TAL injury can be managed with a cervical collar. Nonunion rates are not different between halo immobilization and cervical collar, but a strong selection bias precludes directly comparing the efficacy of these modalities. Age independently predicts nonunion.

Estudio morfológico de pontículus pósticus en telerradiografías laterales / Morphological study of pontículus pósticus in lateral teleradiographies

OBJETIVO establecer la prevalencia de Pontículus Pósticus (PP) en pacientes atendidos en el Servicio de Imagenología de la Universidad Finis Terrae en el periodo 2015-2020. METODOLOGÍA estudio de tipo transversal descriptivo, donde se analizaron 334 telerradiografías laterales (TL) obtenidas del Servicio de Imagenología de la Universidad Finis Terrae entre los años 2015 y 2019 adquiridas mediante el equipo marca SIRONA modelo Orthophos XG, seleccionándolas según criterios de inclusión y exclusión. Se analizó la primera vértebra cervical buscando la presencia de PP consignando: sexo, edad y tipo de osificación según clasificación de Cederberg y Stubbs, asignándoles valores numéricos para posteriormente realizar el análisis estadístico de tipo descriptivo uni y bivariado. RESULTADOS se seleccionaron 320 TL. La prevalencia de PP fue del 31,9% de las TL incluidas, de los cuales el 68,1% correspondió al tipo 1 de la clasificación de Cederberg y Stubbs, el 14,1% al tipo 2, 10,3% al tipo 4 y el 7,5% al tipo 3. La edad media en pacientes con PP presente correspondió a 30,63 años +/­ 15,888 D.E con un mínimo de 12 años y un máximo de 78. En cuanto a la presencia de PP y la variable sexo, el 53,9% correspondió al sexo femenino y el 46,1% al sexo masculino, en donde no se encontró una predilección estadísticamente significativa (p = 0,08). CONCLUSIONES el PP es una variante anatómica de prevalencia variada, siendo levemente mayor en esta población chilena en comparación con otros países. Además, su evidencia es escasa y no existe un consenso sobre su prevalencia y diversas variables como el género y la edad, difiriendo en varios estudios. Es importante conocer e investigar más sobre la epidemiología de esta anomalía y su relación con distintos desórdenes neurológicos

OBJETIVE to establish the prevalence of Ponticulus Posticus (PP) in patients attended in Radiology Service of Finis Terrae University between the years 2015 and 2020. METHODOLOGY descriptive cross-sectional study, 334 lateral cephalograms were analyzed obtained from the Radiology Service of Finis Terrae University between the years 2015 and 2020 acquired from SIRONA system model Orthophos XG, selecting them following the inclusion and exclusion criteria. The first cervical vertebrae were analyzed searching for the presence of PP, consigning: Type of ossification by Cederberg and Stubbs classification, Age and Sex, assigning them numerical values to subsequently perform the descriptive statistical analysis uni and bivariate. RESULTS the prevalence of PP found was 31,9% of the 320 included TL, of which 68,1% corresponded to Type 0 of Cederberg and Stubbs classification, 14,1% to Type 1, 10,3% to Type 3 and the 7,5% al Type 2. The average age of present PP patient's was 30,63 years +­ 15,888 S.D with a minimum of 12 years and a maximum de 78. As for the presence of PP and sex variable, 53,9% corresponded to female sex and 46,1% to males, where no statistically significant predilection was found (p = 0,08). CONCLUSIONS PP is an anatomical variant with varied prevalence worldwide, being slightly higher in Chile, compared to other countries. In addition, their evidence is scarce and there is no consensus on its prevalence and various variables such as gender and age, differing in several studies. It is important to know and research more about the epidemiology of this anomaly and its relationship with different neurological disorder