Autologous rib grafts for craniocervical junction surgery in children: a clinical application.

OBJECTIVE: Autologous iliac bone is commonly used as a bone graft material to achieve solid fusion in craniocervical junction (CVJ) surgery. However, the developing iliac bone of children is less than ideal as a bone graft material. The matured rib bone of children presents a potential substitute material for iliac bone. The aim of this study was to evaluate the efficacy of autologous rib grafts for craniocervical junction surgery in children. METHODS: The outcomes of 10 children with abnormalities of the craniocervical junction who underwent craniocervical junction surgery between January 2020 and December 2022 were retrospectively reviewed. All patients underwent posterior fusion and internal fixation surgery with autologous rib grafts. Pre- and post-operative images were obtained and clinical follow-ups were conducted to evaluate neurological function, pain level, donor site complications, and bone fusion rates. RESULTS: All surgeries were successful. During the 8- to 24-month follow-up period, all patients achieved satisfactory clinical results. Computed tomography at 3-6 months confirmed successful bone fusion and regeneration of the rib defect in all patients with no neurological or donor site complications. CONCLUSION: Autologous rib bone is a safe and effective material for bone grafting in craniocervical junction fusion surgery for children that can reduce the risks of donor site complications and increase the amount of bone graft, thereby achieving a higher bone fusion rate.

Anatomy and mobility in the adult cadaveric craniocervical junction.

Genetic diseases with craniofacial malformations can be associated with anomalies of the craniocervical joint (CCJ). The functions of the CCJ are thus impaired, as mobility may be either limited by abnormal bone fusion causing headaches, or exaggerated in the case of hypermobility, which may cause irreparable damage to the spinal cord. Restoring the balance between mobility and stability requires surgical correction in children. The anatomy and biomechanics of the CCJ are quite unique, yet have been overlooked in the past decades. Pediatric evidence is so scarce, that investigating the adult CCJ is our best shot to disentangle the form-function relationships of this anatomical region. The motivation of the present study was to understand the morphological and functional basis of motion in the CCJ, in the hope to find morphological features accessible from medical imaging able to predict mobility. To do so, we have quantified the in-vitro kinematics of the CCJ in nine cadaveric asymptomatic adults, and estimated a wide range of mobility variables covering the complexity of spinal motion. We compared these variables with the shape of the occipital, the atlas and the axis, obtained using a dense geometric morphometric approach. Morphological joint congruence was also quantified. Our results suggest a strong relationship between bone shape and motion, with the overall geometry predicting best the primary movements, and the joint facets predicting best the secondary movements. We propose a functional hypothesis stating that the musculoligamental system determines movements of great amplitude, while the shape and congruence of joint facets determine the secondary and coupled movements, especially by varying the geometry of bone stops and the way ligaments are tensioned. We believe this work will provide valuable insights in understanding the biomechanics of the CCJ. Furthermore, it should help surgeons treating CCJ anomalies by enabling them to translate objectives of functional and clinical outcome into clear objectives of morphological outcome.

Anatomical determinants of occipitocervical fusion in skull base chordoma resection: a systematic review of the literature with illustrative cases.

OBJECTIVE: Skull base chordomas are rare, locally osseo-destructive lesions that present unique surgical challenges due to their involvement of critical neurovascular and bony structures at the craniovertebral junction (CVJ). Radical cytoreductive surgery improves survival but also carries significant morbidity, including the potential for occipitocervical (OC) destabilization requiring instrumented fusion. The published experience on OC fusion after CVJ chordoma resection is limited, and the anatomical predictors of OC instability in this context remain unclear. METHODS: PubMed and Embase were systematically searched according to the PRISMA guidelines for studies describing skull base chordoma resection and OC fusion. The search strategy was predefined in the authors' PROSPERO protocol (CRD42024496158). RESULTS: The systematic review identified 11 surgical case series describing 209 skull base chordoma patients and 116 (55.5%) who underwent OC instrumented fusion. Most patients underwent lateral approaches (n = 82) for chordoma resection, followed by midline (n = 48) and combined (n = 6) approaches. OC fusion was most often performed as a second-stage procedure (n = 53), followed by single-stage resection and fusion (n = 38). The degree of occipital condyle resection associated with OC fusion was described in 9 studies: total unilateral condylectomy reliably predicted OC fusion regardless of surgical approach. After lateral transcranial approaches, 4 studies cited at least 50%-70% unilateral condylectomy as necessitating OC fusion. After midline approaches-most frequently the endoscopic endonasal approach (EEA)-at least 75% unilateral condylectomy (or 50% bilateral condylectomy) led to OC fusion. Additionally, resection of the medial atlantoaxial joint elements (the C1 anterior arch and tip of the dens), usually via EEA, reliably necessitated OC fusion. Two illustrative cases are subsequently presented, further exemplifying how the extent of CVJ bony elements removed via EEA to achieve complete chordoma resection predicts the need for OC fusion. CONCLUSIONS: Unilateral total condylectomy, 50% bilateral condylectomy, and resection of the medial atlantoaxial joint elements were the most frequently described independent predictors of OC fusion in skull base chordoma resection. Additionally, consistent with the occipital condyle harboring a significantly thicker joint capsule at its posterolateral aspect, an anterior midline approach seems to tolerate a greater degree of condylar resection (75%) than a lateral transcranial approach (50%-70%) prior to generating OC instability.

Atlantoaxial dislocation in the setting of NMLFS.

BACKGROUND: Nablus mask-like facial syndrome (NMFLS) is an extremely rare genetic syndrome characterized by facial dysmorphia as well as developmental delay. In the present report we describe a potential association between non-traumatic atlanto-occipital dislocation and NMFLS in an 11-year old female lacking typical facial features of NMFLS. CASE DESCRIPTION: An 11-year-old female with autism presented with symptoms of persistent headache and vomiting as well as neck stiffness. Further investigation and CT imaging revealed congenital malformation of the skull base and craniocervical junction with complete posterior subluxation of the left occipital condyle. MRI findings later corroborated the findings on CT. CONCLUSIONS: The patient was successfully treated with occipitocervical fusion. The findings in this case suggest the possibility that atlanto-occipital instability and generalized occipitocervical may be associated with NMFLS.

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.

A Global Bibliometric and Visualization Analysis of Craniovertebral Junction Bony Abnormalities Based on VOSviewer and Citespace.

OBJECTIVE: Recent years have witnessed a rapidly growing interest in CVJ bony abnormalities, and a qualitative and quantitative analysis of relevant literatures is necessary. This study aims to identify and summarize the published articles related to craniovertebral junction bony abnormalities, to analyze and visualize the current research trends and major contributors. METHODS: We collected data from Web of Science, excluding certain article types. Two researchers screened articles for relevance. Data were organized with EndnoteX9, and analyzed using VOSviewer and CiteSpace for co-authorship, co-occurrence, keyword burst, and co-citation analyses to identify research trends and collaborations. RESULTS: A total of 2,776 articles were included, revealing an increasing trend in annual publications of CVJ bony abnormalities. The USA was the leading country. King Edward Memorial Hospital was the most prolific institution, and Seth GS Medical College had the most citations. The Spine is the most popular journal with the highest number of publications and citations. Professor Goel Atul from India emerged as the most influential pioneer in this field. Keyword analysis highlighted surgical techniques, diagnosis, and anatomy as the primary research hotspots and Fixation, Placement, and Basilar invagination gradually become the new research trend. However, there is a relative weakness in basic research and epidemiology. CONCLUSIONS: This study provides valuable insights into the current research trends and critical contributors in CVJ bony abnormalities, guiding evidence-based decisions and fostering international collaborations to advance knowledge in this field.

[Preoperative Simulation for Complication Control in Spinal Surgery].

The craniovertebral junction not only contains anatomically important structures such as the medulla oblongata, upper cervical spinal cord, and vertebral artery, but also controls the dynamic movements of flexion, extension, and rotation of the head and neck. Consequently, instability and spinal deformities can easily occur in the craniovertebral region, and appropriate treatment should be selected based on the specificity of the lesion. Basilar invagination often involves bone and vascular anomalies and fusion surgery is often required. Therefore, careful pre-operative simulations are necessary. The creation and use of three-dimensional bone models, including image navigation, are useful for surgical simulation.

Clinical characteristics of upper cervical spine injuries in children: a retrospective case series.

OBJECTIVE: Pediatric cervical spine injuries (CSI) can be devastating, and children < 8 years are particularly at risk for upper CSI given unique anatomical differences. Diagnosis of these injuries can be delayed due to variable clinical presentations and a paucity of existing literature. The authors aimed to characterize the spectrum of pediatric upper CSI. METHODS: This was a retrospective, single-center case series of trauma patients aged < 16 years who were assessed at a level I pediatric trauma center and diagnosed with upper CSI between 2000 and 2020. Patients were included if they had evidence of bony or ligamentous injury from the occiput to C2 on imaging or autopsy. Data were obtained from manual chart review and analyzed using descriptive statistics. RESULTS: In total, 502 patients were screened and 202 met inclusion criteria. Of these, 31 (15%) had atlanto-occipital (AO) joint distractions, 10 (5%) had atlanto-axial (AA) joint distractions, 31 (15%) had fractures of C1-2, and 130 (64%) had ligamentous injury without joint distraction. Of the patients with AO injury, 15 patients had complete dislocation. They presented as hemodynamically unstable with signs of herniation and 14 died (93%). In contrast, 16 had incomplete dislocation (subluxation). They usually had stable presentations and survived with good outcomes. Of the patients with AA injury, 2 had complete dislocation, presented with arrest and signs of herniation, and died. In contrast, 8 patients with subluxation mostly presented as clinically stable and all survived with little residual disability. The most common fractures of C1 were linear fractures of the lateral masses and of the anterior and posterior arches. The most common fractures of C2 were synchondrosis, hangman, and odontoid fractures. Overall, these patients had excellent outcomes. Ligamentous injuries frequently accompanied other brain or spine injuries. When these injuries were isolated, patients recovered well. CONCLUSIONS: Among upper CSI, AO and AA joint injuries emerged as particularly severe with high mortality rates. Both could be divided into complete dislocations or incomplete subluxations, with clear clinical differences and the former presenting with much more severe injuries. Lateral cervical spine radiography should be considered during resuscitation of unstable trauma patients to assess for these CSI subtypes. Fractures and ligamentous injuries were clinically heterogeneous, with presentations and outcomes depending on severity and associated injuries.

Anatomy of the craniocervical junction - A review.

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.

[Atlanto-occipital dislocation-A challenge with respect to making the diagnosis and treatment]. / Atlantookzipitale Dislokation ­ eine Herausforderung hinsichtlich der Diagnosestellung und Therapie.

BACKGROUND: The correct diagnosis and treatment of the atlanto-occipital dislocation (AOD) remains a major challenge. OBJECTIVE: To evaluate the different radiological diagnostic criteria for AOD and discuss potential treatment strategies based on a case with AOD and additional fracture of the atlas. MATERIAL AND METHODS: A 29-year-old male patient is presented who suffered from AOD with concomitant fracture of the anterior and posterior arches of the atlas with rotational atlantoaxial dislocation following an accident in forestry. The following parameters were evaluated for the diagnosis and assessment of postoperative reduction: Powers ratio, the X­lines-method, Wackenheim line, basion-dens interval (BDI), basion-axial interval (BAI) and occipital condyle-C1 interval (CCI). RESULTS: Stabilization was performed by occipitocervical spondylodesis from C0 to C2/3. For final reduction it was necessary to reduce the malrotation of the atlas. In the presented case, the revised CCI proved to be a sensitive and valid yet practical parameter. Powers' ratio and the BDI were less suited for assessing the diagnosis. The X­lines-method, Wackenheim line and the BAI did not adequately detect the pathological situation. DISCUSSION: The AOD is a severe injury requiring immediate correct diagnosis for later adequate treatment results. Among the published parameters, the revised CCI proved to be a practical and valid parameter to detect AOD. For definitive treatment, the operative occipitocervical stabilization is regarded as the method of choice.

Novelties for increased safety in cranio-vertebral surgery: a review.

The cranio-vertebral junction (CVJ) was formerly considered a surgical "no man's land" due to its complex anatomical and biomechanical features. Surgical approaches and hardware instrumentation have had to be tailored in order to achieve successful outcomes. Nowadays, thanks to the ongoing development of new technologies and surgical techniques, CVJ surgery has come to be widely performed in many spine centers. Accordingly, there is a drive to explore novel solutions and technological nuances that make CVJ surgery safer, faster, and more precise. Improved outcome in CVJ surgery has been achieved thanks to increased safety allowing for reduction in complication rates. The Authors present the latest technological advancements in CVJ surgery in terms of imaging, biomaterials, navigation, robotics, customized implants, 3D-printed technology, video-assisted approaches and neuromonitoring.

Reduction of Atlanto-Occipital Dislocation After Cervical Collar Removal.

A 39-year-old male pedestrian-hit-by-car was transferred to our institution with atlantooccipital dislocation (AOD) on outside computed tomography (CT) imaging. On arrival he had a rigid cervical collar in place. Given the reported AOD, we placed the patient flat, removed the cervical collar, and supported the head in neutral alignment with sandbags. Due to a technical issue uploading his prior imaging to our system, the patient underwent repeat CTs at our center. Subsequently, after the outside images were uploaded, we were able to compare his cervical spine CT images before and after removing his cervical collar. On comparison, we noted a substantial reduction in AOD after collar removal. We hope this serves as a reminder of this key step in managing a rare but deadly clinical entity and a small demonstration of the efficacy of this intervention.

Functional Anatomy and Biomechanics of the Craniovertebral Junction.

The craniovertebral junction (CVJ) involves the atlas, axis, and occiput along with the atlanto-occipital and atlantoaxial joints. The anatomy and neural and vascular anatomy of the junction render the CVJ unique. Specialists treating disorders that affect the CVJ must appreciate its intricate anatomy and should be well versed in its biomechanics. This first article in a three-article series provides an overview of the functional anatomy and biomechanics of the CVJ.

Cervical MRI assessment of traumatic anterior atlanto-occipital membrane complex injuries with evaluation of ancillary findings.

BACKGROUND AND PURPOSE: The purpose of this study was to identify and classify the different types of anterior atlanto-occipital membrane complex injuries on MRI and evaluate for the presence, size, and location of a prevertebral effusion on the preceding CT exams. MATERIALS AND METHODS: Patients who suffered an anterior atlanto-occipital membrane complex injury were identified retrospectively utilizing Nuance mPower software. An anatomic-based description of the location of the anterior atlanto-occipital membrane complex injury was recorded along with any additional osteoligamentous trauma of the craniocervical junction. The preceding cervical CT exams for these patients were reviewed for the presence and location of a prevertebral effusion. RESULTS: Fifty patients were identified with an acute, post-traumatic anterior atlanto-occipital membrane complex injury. Three distinct patterns of anterior atlanto-occipital membrane complex injury were observed. Nineteen patients demonstrated increased STIR signal with disruption of the anterior atlanto-occipital membrane, ten patients demonstrated increased STIR signal with disruption of the anterior atlanto-axial membrane, and twenty-one patients demonstrated increased STIR signal with disruption of both the anterior atlanto-occipital membrane and anterior atlanto-axial membrane. An effusion at the C1-C2 level was present in greater than 90% of patients with anterior atlanto-occipital membrane complex injury. CONCLUSIONS: The presence of a craniocervical prevertebral effusion on CT in trauma patients may raise suspicion for an injury to the anterior atlanto-occipital membrane complex and potentially trigger additional investigation with cervical MRI.

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.

Septic Arthritis of the Atlanto-Occipital Joint Caused By S. Intermedius in a 5-Year-Old Girl: A Case Report.

Septic arthritis of the atlanto-occipital joint caused by Streptococcus intermedius is extremely rare. We present the first case report of this entity in a fully immunocompetent 5-year-old girl. The magnetic resonance imaging and blood tests were consistent with septic arthritis, so she started empirical antibiotic therapy. Septic arthritis should be excluded in children with torticollis, fever and neck pain.

Atlanto-occipital dislocation with concomitant severe traumatic brain injury: A retrospective study at a level 1 trauma center / Luxación atlantooccipital con traumatismo craneoencefálico grave concomitante: estudio retrospectivo en un centro de trauma de nivel 1

Background: Traumatic atlanto-occipital dislocation (AOD) is a life-threatening injury. Although traumatic brain injury (TBI) is associated with increased mortality in AOD patients, a detailed individual analysis of these patients is lacking in the literature. Methods: Patients ≥16 years old who were diagnosed of AOD with concomitant severe TBI from 2010 to 2020 were included in this retrospective study. We examined the epidemiology, injury mechanisms, associated injuries, and outcomes of these patients. Results: Eight patients were included. Six patients died before any intervention could be performed, and two patients underwent an occipito-cervical fixation, showing a notorious neurologic improvement on follow-up. Cardiorespiratory arrest (CRA) was a strong predictor of subsequent death. CT signs of diffuse axonal injury (DAI) were present in most patients and were confirmed by magnetic resonance imaging (MRI) in survivors. Although TBI was not the main cause of death, it was responsible for the delayed neurological improvement and deferred stabilization. The average sensitivity of the different used methodologies for AOD diagnosis ranged from 0.50 to 1.00, being the Basion Dens Interval (BDI) and the Condyle-C1 interval (CCI) sum the most reliable criteria. Non-survivors tended to show greater distraction measurements. The high incidence of condylar avulsion fractures suggests that their visualization on the initial CT study should heighten the suspicion for AOD. Conclusions: Our data suggest that patients with AOD and concomitant severe TBI might be salvageable patients. In those who survive beyond the first hospital days and show neurological improvement, surgical treatment should be performed as they can achieve an important neurologic recovery. (AU)

Antecedentes: La luxación atlantooccipital (AOD) traumática es una lesión potencialmente mortal. Aunque el traumatismo craneoencefálico (TCE) se asocia con un aumento de la mortalidad en los pacientes con AOD, no existe en la literatura un análisis individual detallado de estos pacientes. Métodos: En este estudio retrospectivo se incluyeron pacientes mayores de 16 años que fueron diagnosticados de AOD con TCE grave concomitante durante el periodo 2010-2020. Estudiamos la epidemiología, los mecanismos lesionales, así como las lesiones asociadas y los resultados de estos pacientes. Resultados: Se incluyeron ocho pacientes. Seis pacientes fallecieron antes de que se pudiera realizar cualquier intervención y dos pacientes fueron sometidos a una fijación occipitocervical, mostrando una notoria mejoría neurológica durante el seguimiento. La parada cardiorrespiratoria fue un predictor de muerte. En la TC inicial, signos de lesión axonal difusa estaban presentes en la mayoría de los pacientes y se confirmaron mediante imágenes de resonancia magnética en los supervivientes. Aunque el TCE no fue la principal causa de muerte, fue responsable de una mejoría neurológica tardía y por ello una estabilización diferida. La sensibilidad de las diferentes metodologías utilizadas para el diagnóstico de AOD osciló entre 0,50 y 1,00, siendo el intervalo Basion Dens y la suma del intervalo Condylo-C1 los criterios más fiables. Además, los no supervivientes presentaban mayores medidas de distracción. La alta incidencia de fracturas de cóndilo por avulsión sugiere que su visualización en el estudio de TC inicial debería aumentar la sospecha de AOD. Conclusiones: Nuestros datos sugieren que los pacientes con AOD y TCE grave concomitante podrían ser pacientes salvables. En aquellos que sobreviven más allá de los primeros días de...(AU)Palabras clave:Luxación atlantooccipitalColumna cervicalUnión craneocervicalFusión occipitocervicalTraumatismo craneoencefálico

Atlanto-occipital dislocation with concomitant severe traumatic brain injury: A retrospective study at a level 1 trauma center.

BACKGROUND: Traumatic atlanto-occipital dislocation (AOD) is a life-threatening injury. Although traumatic brain injury (TBI) is associated with increased mortality in AOD patients, a detailed individual analysis of these patients is lacking in the literature. METHODS: Patients ≥16 years old who were diagnosed of AOD with concomitant severe TBI from 2010 to 2020 were included in this retrospective study. We examined the epidemiology, injury mechanisms, associated injuries, and outcomes of these patients. RESULTS: Eight patients were included. Six patients died before any intervention could be performed, and two patients underwent an occipito-cervical fixation, showing a notorious neurologic improvement on follow-up. Cardiorespiratory arrest (CRA) was a strong predictor of subsequent death. CT signs of diffuse axonal injury (DAI) were present in most patients and were confirmed by magnetic resonance imaging (MRI) in survivors. Although TBI was not the main cause of death, it was responsible for the delayed neurological improvement and deferred stabilization. The average sensitivity of the different used methodologies for AOD diagnosis ranged from 0.50 to 1.00, being the Basion Dens Interval (BDI) and the Condyle-C1 interval (CCI) sum the most reliable criteria. Non-survivors tended to show greater distraction measurements. The high incidence of condylar avulsion fractures suggests that their visualization on the initial CT study should heighten the suspicion for AOD. CONCLUSIONS: Our data suggest that patients with AOD and concomitant severe TBI might be salvageable patients. In those who survive beyond the first hospital days and show neurological improvement, surgical treatment should be performed as they can achieve an important neurologic recovery.

Exploring the Pathogenesis of Atlanto-Occipital Instability in Chiari Malformation With Type II Basilar Invagination: A Systematic Morphological Study.

BACKGROUND: Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI). OBJECTIVE: To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction. METHODS: Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ). RESULTS: Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI. CONCLUSION: Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI.