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OBJECTIVE: This retrospective study aims to investigate the effect of the type of atlantoaxial dislocation due to os odontoideum on the sagittal alignment and balance of the cervical spine after posterior atlantoaxial fusion. METHODS: Data of 48 consecutive patients who underwent posterior C1-C2 fusion to treat atlantoaxial dislocation/instability due to os odontoideum were retrospectively reviewed. Radiographic variables, namely the T1 slope (T1S), C1-C2 angle, C2-C7 angle, C1-C2 sagittal vertical axis (SVA), C2-C7 SVA, and modified atlas-dens interval (MADI), were measured preoperatively, immediate postoperatively, and at final follow-up. Patients were divided into three groups based on the preoperative MADI. Differences within and between groups in radiographic variables and relationships between the investigated variables were analyzed. RESULTS: The MADI was correlated with the preoperative to postoperative changes in the C1-C2 angle (r = 0.776, P < 0.05) and C2-C7 angle (r = - 0.357, P < 0.05). In the group with anterior atlantoaxial dislocation, the C1-C2 angle and C2-C7 SVA were significantly enlarged at final follow-up (P < 0.05), while the C2-C7 angle was significantly reduced (P < 0.05). The changes in C1-C2 angle and C2-C7 angle were opposite between the posterior group and the anterior dislocation group. CONCLUSION: The direction/type of atlantoaxial subluxation correlates with the changes in lower cervical curvature after atlantoaxial fusion. Patients with atlantoaxial posterior dislocation and atlantoaxial instability are less likely than those with atlantoaxial anterior dislocation to develop loss of lordosis after posterior atlantoaxial fusion.
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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.
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Articulação Atlantoccipital , Fossa Craniana Posterior , Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Adulto Jovem , Adolescente , Atlas Cervical/diagnóstico por imagem , Imageamento por Ressonância Magnética , Idoso , Criança , Tomografia Computadorizada por Raios XRESUMO
Traumatic posterior atlantoaxial dislocation combined with Jefferson fracture and odontoid process fracture with vertebral artery injury is rare. The management of such injury raises controversial issues and is still open to debate. A 74-year-old Chinese male presented with sustained neck pain and stiffness after falling from height. The patient was neurologically intact. Preoperative radiographs demonstrated a Jefferson burst fracture with a posterior dislocation of the atlantoaxial joints and odontoid process Anderson and D'alonzo type II fracture. A computed tomography angiography (CTA) showed an occluded left vertebral artery. Coil embolization in the proximal portion of the occluded vertebral artery was performed to prevent further cerebral infarction due to distal embolization of the thrombus. Then a second stage occipito-cervical fusion was performed to reconstruct cervical spine stability. A systematic screening of blunt trauma vertebral artery injuries through CTA is required when dealing with upper cervical fracture. For cases with vertebral artery occlusion secondary to cervical spine injury, endovascular treatment preceding cervical spine surgery is a feasible and a safe treatment.
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OBJECTIVE: To investigate (1) lateral atlantoaxial articulation (LAA) morphology in patients with basilar invagination (BI) with atlantoaxial dislocation (AAD) and healthy individuals and its relationship with the severity of dislocation and (2) the effect of the LAA morphology on reduction degree (RD) after surgery. METHODS: In this retrospective propensity score matching case-control study, imaging and baseline data of 62 patients with BI and AAD from 2011 to 2022 were collected. Six hundred thirteen participants without occipitocervical junctional deformity served as controls. Logistic regression and receiver operating characteristic (ROC) curve were used for analysis. RESULTS: The age, BMI and sex did not differ significantly between the two groups after propensity score matching. Sagittal slope angle (SSA) and coronal slope angle (CSA) was lower and greater, respectively, in the patient group than in the control group. A negative SSA value usually indicates anteverted LAA. Regression analysis revealed a significant negative correlation between SSA and severity of dislocation. However, no relationship was found between CSA and the severity of dislocation. The multivariate logistic regression analysis revealed that minimum-SSA emerged as an independent predictor of satisfactory reduction (RD ≥ 90%). The ROC curve demonstrated an area under the curve of 0.844, with a cut-off value set at -40.2. CONCLUSION: SSA in patients group was significantly smaller and more asymmetric than that in the control group. Dislocation severity was related to SSA but not to CSA. Minimum-SSA can be used as a predictor of horizontal RD after surgery.
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Articulação Atlantoaxial , Luxações Articulares , Humanos , Masculino , Feminino , Articulação Atlantoaxial/cirurgia , Articulação Atlantoaxial/diagnóstico por imagem , Luxações Articulares/cirurgia , Luxações Articulares/diagnóstico por imagem , Luxações Articulares/etiologia , Estudos Retrospectivos , Adulto , Pessoa de Meia-Idade , Estudos de Casos e Controles , Índice de Gravidade de Doença , Resultado do Tratamento , Platibasia/diagnóstico por imagem , Platibasia/cirurgia , Pontuação de Propensão , Adulto Jovem , Fusão Vertebral/efeitos adversos , Tomografia Computadorizada por Raios XRESUMO
INTRODUCTION AND IMPORTANCE: Os odontoideum is a rare condition commonly associated with atlantoaxial instability (AAI) and leading to atlantoaxial dislocation. The incidence of Os odontoideum is higher in patients with Down syndrome. Similar to odontoid fractures, atlantoaxial dislocation in patients with Os odontoideum can result in neurological deficits, disability, and even mortality. CASE PRESENTATION: We present two cases of Os odontoideum accompanied by Down syndrome. Both patients were hospitalized due to progressive tetraparesis after falls several months prior. Upon examination, the patients exhibited myelopathy and were unable to walk or stand. MRI revealed spinal stenosis at the C1-C2 level due to atlantoaxial dislocation. C1-C2 fixation using Harms' technique was performed in both cases. One case experienced a complication involving instrument failure, necessitating revision surgery. CLINICAL DISCUSSION: Due to the characteristics of transverse ligament laxity, low muscle tone, excessive joint flexibility, and cognitive impairment, children with both Down syndrome and Os odontoideum are at a high risk of disability and even mortality from spinal cord injury. Most authors recommend surgical management when patients exhibit atlantoaxial instability. Additional factors such as low bone density, cognitive impairment, and a high head-to-body ratio may increase the risk of surgical instrument failure and nonunion postoperatively in patients with Down syndrome. CONCLUSION: Os odontoideum is a cause of AAI in patients with DS. Indication of surgery in the presence of AAI helps to resolve neurological injury and prevent further deterioration. The use of a cervical collar is considered to prevent instrument failure postoperatively.
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OBJECTIVE: To develop posterior reduction forceps for atlantoaxial dislocation and evaluate the preliminary clinical application of this forceps in assisting simple posterior screw-rod system reduction and fixation in the treatment of irreducible atlantoaxial dislocation. METHODS: Based on the posterior atlantoaxial screw-rod system, posterior reduction forceps was developed to assist simple posterior screw-rod system for the treatment of irreducible atlantoaxial dislocation. From January 2021 to October 2022, 10 cases with irreducible atlantoaxial dislocation were treated with this technique. The Japanese Orthopaedic Association (JOA) score was applied before and after surgery to evaluate the neurological status of the patient, and the Atlanto-dental interval (ADI) was measured before and after surgery to evaluate the atlantoaxial reduction. X-ray and CT were performed to evaluate internal fixation, atlantoaxial sequence and bone graft fusion during regular follow-up. MRI was performed to evaluate the status of atlantoaxial reduction and spinal cord compression after surgery. RESULTS: All 10 patients were successfully operated, and there were no complications such as spinal nerve and vascular injury. Postoperative clinical symptoms were significantly relieved in all patients, and postoperative JOA score and ADI were significantly improved compared with those before surgery (P < 0.05). CONCLUSIONS: The developed posterior reduction forceps for atlantoaxial dislocation can assist the simple posterior screw-rod system in the treatment of irreducible atlantoaxial dislocation to avoid the release in anterior or posterior approach and reduce the difficulty of surgery. The preliminary results of this technique are satisfactory and it has a good application prospect.
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Articulação Atlantoaxial , Luxações Articulares , Humanos , Articulação Atlantoaxial/cirurgia , Articulação Atlantoaxial/diagnóstico por imagem , Luxações Articulares/cirurgia , Luxações Articulares/diagnóstico por imagem , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Fusão Vertebral/métodos , Fusão Vertebral/instrumentação , Parafusos Ósseos , Adulto Jovem , Resultado do Tratamento , AdolescenteRESUMO
PURPOSE: To evaluate the clinical feasibility of atlantoaxial intra-articular cage (AIC) fusion via intermuscular approach for treating reducible atlantoaxial dislocation (AAD). METHODS: An analysis was conducted on the data of 10 patients who underwent C1-C2 segmental fixation and AIC fusion for AAD by unilateral intermuscular approach and contralateral open approach. Outcome assessments included Japanese Orthopaedic Association score (JOA) and Visual Analog Scale Score for Neck Pain (VASSNP). The duration of surgical exposure, screw insertion and cage insertion, and postoperative drainage volume were also compared between two approaches. Bone fusion was evaluated through computed tomography (CT) reconstruction. Postoperative paravertebral tissue edema was evaluated by paravertebral tissue cross-sectional area (CSA) and signal intensity on T2 weighted sequence of magnetic resonance imaging (MRI) at 3 days postoperatively. RESULTS: The intermuscular approach exhibited a longer exposure time but lower drainage postoperatively compared to the open approach (P < 0.05). After operation, JOA scores significant improved (P < 0.05), while VASSNP scores significantly decreased (P < 0.05). There was no significant difference in preoperative CSA between two approaches (P > 0.05). However, compared to the open approach, the intermuscular approach exhibited less CSA (P < 0.05) and lower T2 signal intensity on MRI postoperatively, indicating less invasive to the paravertebral tissues. CONCLUSIONS: AIC fusion by intermuscular approach is an effective and safe technique in the treatment of reducible AAD. Intermuscular approach could reduce the postoperative drainage volume and the extent of paravertebral tissue edema compared to open approach.
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Articulação Atlantoaxial , Luxações Articulares , Fusão Vertebral , Humanos , Articulação Atlantoaxial/cirurgia , Articulação Atlantoaxial/diagnóstico por imagem , Luxações Articulares/cirurgia , Luxações Articulares/diagnóstico por imagem , Masculino , Fusão Vertebral/métodos , Feminino , Adulto , Pessoa de Meia-Idade , Resultado do TratamentoRESUMO
The combination of atlantoaxial joint dislocation accompanied by an odontoid process fracture is exceptionally rare, with only a few cases reported. The estimated frequency of these cases is < 2% of all upper cervical spine injuries. In this report, the authors describe an unusual case of traumatic atlantoaxial dislocation with a type III odontoid fracture in a 44-year-old male patient. Before the diagnosis, the patient had a history of seeking a masseur for a neck massage. Subsequently, the patient underwent occipitocervical stabilization to address the underlying condition. This procedure aims to treat the instability between the skull and cervical spine and should be considered in the treatment planning if the patient's anatomy suits it.
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Transient receptor potential vanilloid 4 channel ( TRPV4 ) gene mutations have been described in skeletal system and peripheral nervous system pathology. The case described here is a 9-year-old male child patient, born to a nonconsanguineous marriage with normal birth history who had difficulty in walking and stiffness of joints for the last 7 years, and progressive weakness of all four limbs and urine incontinence for 1 year following falls. Physical examination showed below-average weight and height and short trunk. Musculoskeletal examination revealed bony prominence bilaterally in the knee joints and contractures in knee and elbow joints with brachydactyly; muscle tone was increased, with brisk deep tendon reflexes. Skeletal survey showed platyspondyly with anterior beaking with metaphyseal dysplasia. Magnetic resonance imaging of the spine revealed atlantoaxial instability with hyperintense signal changes at a cervicomedullary junction and upper cervical cord with thinning and spinal canal stenosis suggestive of compressive myelopathy with platyspondyly and anterior beaking of the spine at cervical, thoracic and lumbar vertebrae. Exome sequencing revealed a heterozygous de novo variant c.2389G > A in exon 15 of TRPV4 , which results in the amino acid substitution p.Glu797Lys in the encoded protein. The characteristics observed indicated spondylometaphyseal dysplasia, Kozlowski type (SMD-K). The child underwent surgical intervention for compressive myelopathy by reduction of atlantoaxial dislocation with C1 lateral mass and C2 pars fusion using rib graft and fixation using screws and rods. To conclude, for any child presenting with progressive kyphoscoliosis, short stature, platyspondyly, and metaphyseal changes, a diagnosis of SMD-K should be considered and the patient and family should be advised to avoid spinal injuries.
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BACKGROUND: Klippel-Feil syndrome (KFS) is a rare congenital disorder characterized by the fusion of two or more cervical vertebrae during early prenatal development. This fusion results from a failure of segmentation during the first trimester. Although six genes have previously been associated with KFS, they account for only a small proportion of cases. Among the distinct subtypes of KFS, "sandwich fusion" involving concurrent fusion of C0-1 and C2-3 vertebrae is particularly noteworthy due to its heightened risk for atlantoaxial dislocation. In this study, we aimed to investigate novel candidate mutations in patients with "sandwich fusion." METHODS: We collected and analyzed clinical data from 21 patients diagnosed with "sandwich fusion." Whole-exome sequencing (WES) was performed, followed by rigorous bioinformatics analyses. Our focus was on the six known KFS-related genes (GDF3, GDF6, MEOX1, PAX1, RIPPLY2, and MYO18). Suspicious mutations were subsequently validated through in vitro experiments. RESULTS: Our investigation revealed two novel exonic mutations in the FGFR2 gene, which had not previously been associated with KFS. Notably, the c.1750A > G variant in Exon 13 of FGFR2 was situated within the tyrosine kinase domain of the protein, in close proximity to several established post-translational modification sites. In vitro experiments demonstrated that this certain mutation significantly impacted the function of FGFR2. Furthermore, we identified four heterozygous candidate variants in two genes (PAX1 and MYO18B) in two patients, with three of these variants predicted to have potential clinical significance directly linked to KFS. CONCLUSIONS: This study encompassed the largest cohort of patients with the unique "sandwich fusion" subtype of KFS and employed WES to explore candidate mutations associated with this condition. Our findings unveiled novel variants in PAX1, MYO18B, and FGFR2 as potential risk mutations specific to this subtype of KFS.
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Síndrome de Klippel-Feil , Humanos , Síndrome de Klippel-Feil/genética , Síndrome de Klippel-Feil/complicações , Síndrome de Klippel-Feil/diagnóstico , Sequenciamento do Exoma , Mutação/genética , Receptor Tipo 2 de Fator de Crescimento de Fibroblastos/genéticaRESUMO
Purpose: To assess the accuracy of freehand cervical C1 C2 screws placement by knock and drill (K and D) technique in craniovertebral anomalous bony anatomy. Materials and Methods: From January 2017 to December 2022, 682 consecutive C1 C2 screws in 215 patients with craniovertebral junction (CVJ) anomalies were enrolled. All patients underwent posterior fixation with K and D technique without any fluoroscopic guidance. The patient's demographic details, clinical details, radiological details, major intraoperative events, and postoperative complications were noted. The screws malposition grades and direction on CT images in the axial and sagittal plane were defined as new per proposed "SGPGI accuracy criteria." All patients had a clinical evaluation at 3-month follow-up. Results: Total 682 C1, C2 screws were placed in 215 patients for CVJ anomalies using K and D technique. The accuracy of screws placement by freehand technique was 84.46% (576/682). So with technique explained the rate of malplacement in simple (16.35%) and complex (15.19%) groups were almost comparable and comparison difference was not significant (P = 0.7005). Conclusion: The freehand technique, as described, is effective in cases of anomalous bony anatomy, and it is mandatory in complex CVJ anomalies. The accuracy of screw placement and VA injury is comparable with major studies. This technique is supposedly cost-effective and less hazardous to both health-care workers and patients.
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Aims: To study the clinicoradiological features and treatment outcomes of atlantoaxial dislocation (AAD) in Down syndrome. Settings and Design: Retrospective case series. Subjects and Methods: A retrospective chart and radiology review of 9 Down syndrome patients with AAD managed at our center from 2007 to 2018. Statistical Analysis Used: Chi-squared/Fisher's exact test. Results: There were 4 males and 5 females (n = 9). The median age was 14 years (interquartile range [IQR]: 7-15.5). 77.7% (7/9) of patients had severe spasticity (Nurick Grades 4 and 5). The median duration of symptoms was 9 months (IQR: 5-39). The AAD was reducible in all (n = 9) cases. Eight (88.8%) patients had os odontoideum. The mean atlantodental interval (ADI) was 8.5 mm (±2.9). T2W cord hyperintensity was seen in 66.6% (6/9). Posterior C1-2 transarticular fixation was done in 8 and occipitocervical fusion in 1 patient. Follow-up of more than 6 months (7-57 months) was available in 8/9 (88.9%) patients. There was a significant improvement in spasticity (n = 8, mean Nurick Grade 1.7 (±1.1), P = 0.003). Follow-up radiographs (n = 8) showed good reduction and fusion. A preoperative bedbound patient with poor respiratory reserve expired at 10 months following surgery. There were no other complications. Conclusions: Posterior surgical approach for AAD in Down syndrome resulted in good alignment and fusion, with excellent clinical improvement. Patients with elevated PCO2 are poor surgical candidates and require home ventilation facility.
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Objective: To investigate the biomechanical properties of the retropharyngeal reduction plate by comparing the traditional posterior pedicle screw-rod fixation by finite element analysis. Methods: Two three-dimensional finite element digital models of the retropharyngeal reduction plate and posterior pedicle screw-rod fixation were constructed and validated based on the DICOM (Digital Imaging and Communications in Medicine) data from C1 to C4. The biomechanical finite element analysis values of two internal fixations were measured and calculated under different conditions, including flexion, extension, bending, and rotation. Results: In addition to the backward extension, there was no significant difference in the maximum von Mises stress between the retropharyngeal reduction plate and posterior pedicle screw fixation under other movement conditions. The retropharyngeal reduction plate has a more uniform distribution under different conditions, such as flexion, extension, bending, and rotation. The stress tolerance of the two internal fixations was basically consistent in flexion, extension, left bending, and right bending. Conclusion: The retropharyngeal reduction plate has a relatively good biomechanical stability without obvious stress concentration under different movement conditions. It shows potential as a fixation option for the treatment of atlantoaxial dislocation.
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Neurosurgical management of basilar invagination (BI) has traditionally been aimed at direct cervicomedullary decompression through transoral dens resection or suboccipital decompression with supplemental instrumented fixation. Dr. Goel introduced chronic atlantoaxial dislocation (AAD) as the etiology in most cases of BI and described a technique for distracting the C1-C2 joint with interfacet spacers to achieve reduction and anatomic realignment. We present our modification to Goel's surgical technique, in which we utilize anterior cervical discectomy (ACD) cages as C1-C2 interfacet implants. A young adult male presented to our institution with BI, cervicomedullary compression, occipitalization of C1, and Chiari 1 malformation. There was AAD of C1 over the C2 lateral masses. This reduced some with preoperative traction. He underwent successful C1-C2 interfacet joint reduction and arthrodesis with anterior cervical discectomy (ACD) cages and concomittant occiput to C2 instrumented fusion. BI can be effectively treated through reduction of AAD and by utilizing ACD cages as interfacet spacers.
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Articulação Atlantoaxial , Luxações Articulares , Adulto Jovem , Masculino , Humanos , Articulação Atlantoaxial/diagnóstico por imagem , Articulação Atlantoaxial/cirurgia , Luxações Articulares/diagnóstico por imagem , Luxações Articulares/cirurgia , Descompressão Cirúrgica/métodosRESUMO
A small number of case reports have documented a link between atlantoaxial dislocation (AAD) and vertebral artery dissection (VAD), but this association has never been described in patients with hereditary connective tissue disorders. We present a case of an 18-year-old female patient, diagnosed with Marfan syndrome since the age of one, who underwent brain MRA for intracranial aneurysm screening revealing tortuosity of the internal carotid and vertebral arteries as well as atlantoaxial dislocation. Since the patient was asymptomatic, a wait-and-see approach was chosen, but a follow-up MRA after 18 months showed the appearance of a dissecting pseudoaneurysm of the V3 segment of the left vertebral artery. Despite the patient being still asymptomatic, it was decided to proceed with C1-C2 stabilization to prevent further vascular complications. Follow-up imaging showed realignment of the atlantoaxial joint and reduction of the dissecting pseudoaneurysm of the left vertebral artery. In our patient, screening MRA has led to the discovery of asymptomatic arterial and skeletal abnormalities which, if left untreated, might have led to severe cerebrovascular complications. Therefore, AAD correction or close monitoring with MRA should be provided to MFS patients with this craniovertebral junction anomaly, even if asymptomatic.
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Falso Aneurisma , Aneurisma Intracraniano , Luxações Articulares , Síndrome de Marfan , Dissecação da Artéria Vertebral , Feminino , Humanos , Adolescente , Dissecação da Artéria Vertebral/diagnóstico , Dissecação da Artéria Vertebral/diagnóstico por imagem , Síndrome de Marfan/complicações , Síndrome de Marfan/diagnóstico , Falso Aneurisma/diagnóstico , Falso Aneurisma/diagnóstico por imagem , Artéria Vertebral/diagnóstico por imagem , Artéria Vertebral/anormalidades , Luxações Articulares/complicações , Luxações Articulares/diagnósticoRESUMO
Background: Difficult airway remains a great challenge in patients with atlantoaxial dislocation (AAD). Preoperative evaluation and reliable prediction are required to facilitate the airway management. We aimed to screen out reliable radiological indicators for prediction of difficult laryngoscopy in patients with AAD. Methods: A retrospective nested case-control study within a single center longitudinal AAD cohort was conducted to investigate the radiological indicators. All the patients with difficult laryngoscopy from 2010 to 2021 were enrolled as the difficult laryngoscopy group. Others in the cohort without difficult laryngoscopy were randomly selected as the non-difficult laryngoscopy group by individually matching with the same gender, same surgery year, and similar age (±5 years) at a ratio of 6:1. Radiological data on preoperative lateral X-ray images between the two groups were compared. Bivariate logistic regression model was applied to screen out the independent predictive indicators and calculate the odds ratios of indicators associated with difficult laryngoscopy. Receiver operating characteristic curve and area under the curve (AUC) were used to describe the discrimination ability of indicators. Results: A total of 154 patients were finally analyzed in this study. Twenty-two patients with difficult laryngoscopy and matched with 132 controls. Four radiological parameters showed significant difference between the two groups. Among which, ΔC1C2D (the difference of the distance between atlas and axis in the neutral and extension position), owned the largest AUC. Conclusions: ΔC1C2D could be a valuable radiologic predictor for difficult laryngoscopy in patients with AAD.
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Background and aim: Direct posterior reduction and manipulation of the C1-2 joints, accompanied by placement of spacers, is the state-of-the-art technique for treating basilar invagination (BI) and atlantoaxial dislocation (AAD). The hindrance of occiput to reaching up to the true atlantoaxial facets (AAF) during the surgery remains challenging for cage placement. The aim of this study was to explore an objective and precise method of measuring the effect of the hindrance of occiput to reaching up to the true AAF and cage placement during surgery. Method: We collected the clinico-imaging data of 58 patients with BI and AAD (Group A) who underwent surgery in our hospital, and 78 control cohorts (Group B) were retrieved retrospectively. We measured facet-occiput slope angle (FOSA) in midsagittal CT. Patients were positioned prone for surgery based on preoperative flexion O-C2a, and access to the true AAF was observed intraoperatively. The cut-off value of FOSA for the feasibility of cage placement in BI and AAD patients was appointed when access to the true AAF was impossible due to the hindrance of occiput during surgery. Results: The cut-off value of FOSA for the feasibility of cage placement was 34o with an area under the curve AUC of 0.800 (95 % CI: 0.672-0.928, P < 0.001) and the Youden index of 0.607. In patients with FOSA >34o, reaching up to the true AAF and 3D-printed cage placement was impossible. FOSA was negative in Group A and positive in Group B, significantly larger in females compared to males in both groups and significantly larger postoperatively in Group A. Conclusion: FOSA can objectively measure the feasibility of cage placement when the patient is positioned prone per preoperative flexion O-C2a. A FOSA >34o is contraindication for cage placement.
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BACKGROUND: To evaluate the difficulty of reduction of congenital atlantoaxial dislocation with or without os odontoideum or basilar invagination based on computed tomography (CT) quantitative analysis. METHODS: From March 2018 to December 2022, the CT features of 108 patients with atlantoaxial dislocation with or without os odontoideum or basilar invagination were analyzed. Quantitative scores were defined according to imaging features, including sloping of the lateral mass; osteophyte between the lateral mass joint; ball-and-socket deformity of the lateral mass joint; vertical interlocking of the lateral mass joint; callus between the lateral mass joint; and atlanto-odontoid joint hyperplasia, blocking, or fusion. Grades were calculated according to the sum of points of the atlanto-odontoid joint and lateral mass joints, as follows: I, 0-1 points; â ¡, 2-3 points; â ¢, 4-6 points; IV, 7-10 points. After 1 week of bidirectional cervical traction, CT scans were performed, and atlantodens interval and vertical distance from dens to Chamberlain line were measured. The vertical reduction rate, horizontal reduction rate, and overall reduction rate of atlantoaxial dislocation were calculated. RESULTS: The vertical distance from dens to Chamberlain line values after traction were significantly reduced compared with before traction, including grades I, II, III, and IV. The overall reduction rates were 85.1% ± 11.8%, 65.8% ± 8.3%, 45.0% ± 8.5%, and 38.4% ± 13.0% respectively, after 1 week of bidirectional cervical traction. CONCLUSIONS: The CT quantitative score system is an effective noninvasive evaluation to judge the reduction difficulty of atlantoaxial dislocation with or without os odontoideum or basilar invagination.
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OBJECTIVE: To explore correlations of 3 novel radiographic parameters with myelopathy induced by posterior atlantoaxial dislocation (PAAD) secondary to os odontoideum (OO) and assess their reproducibility. METHODS: Of the 51 patients with OO with PAAD enrolled in this study, 28 developed PAAD-induced myelopathy (myelopathy group), and the other 23 patients had no myelopathy (control group). Neurologic function was evaluated by the neurologic function rating system and the Japanese Orthopaedic Association score system. Three novel radiographic parameters (OP [median sagittal diameter of the spinal canal from the posteroinferior edge of the ossicle to the anterosuperior edge of the spinous process of C2]/C4 SAC [space available for spinal cord] ratio, C1 posterior inclination angle, and posterior dislocation index) were measured by lateral cervical dynamic radiography. Their correlations with neurologic function were analyzed, and their reproducibility was assessed by the intraclass correlation coefficient (ICC). In addition, receiver operating characteristic curve analysis was performed. RESULTS: A significant correlation was observed between the OP/C4 SAC ratio and the neurologic function (P < 0.01), and between the C1 posterior inclination angle and the neurologic function (P < 0.01). Furthermore, their interobserver and intraobserver reliability was excellent (ICC ≥ 0.912). Receiver operating characteristic curve analysis showed that the optimal threshold value relating to myelopathy of the OP/C4 SAC ratio and C1 posterior inclination angle was 0.93 and 20°, respectively. CONCLUSIONS: The OP/C4 SAC ratio and the C1 posterior inclination angle seem to be 2 effective and objective radiographic parameters for relating myelopathy in patients with OO with PAAD. When the OP/C4 SAC ratio is <0.93 and/or the C1 posterior inclination angle is >20°, the risk of developing myelopathy should be highly suspected in patients with OO with PAAD.
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Background: Chiari malformation type 1 (CM-1) is characterized by cerebellar tonsil herniation through the foramen magnum and can be associated with additional craniovertebral junction anomalies (CVJA). The pathophysiology and treatment for CM-1 with CVJA (CM-CVJA) is debated. Objective: To evaluate the trends and outcomes of surgical interventions for patients with CM-CVJA. Methods: A systematic review of the literature was performed to obtain articles describing surgical interventions for patients with CM-CVJA. Articles included were case series describing surgical approach; reviews were excluded. Variables evaluated included patient characteristics, approach, and postoperative outcomes. Results: The initial query yielded 403 articles. Twelve articles, published between 1998-2020, met inclusion criteria. From these included articles, 449 patients underwent surgical interventions for CM-CVJA. The most common CVJAs included basilar invagination (BI) (338, 75.3%), atlantoaxial dislocation (68, 15.1%) odontoid process retroflexion (43, 9.6%), and medullary kink (36, 8.0%). Operations described included posterior fossa decompression (PFD), transoral (TO) decompression, and posterior arthrodesis with either occipitocervical fusion (OCF) or atlantoaxial fusion. Early studies described good results using combined ventral and posterior decompression. More recent articles described positive outcomes with PFD or posterior arthrodesis in combination or alone. Treatment failure was described in patients with PFD alone that later required posterior arthrodesis. Additionally, reports of treatment success with posterior arthrodesis without PFD was seen. Conclusion: Patients with CM-CVJA appear to benefit from posterior arthrodesis with or without decompressive procedures. Further definition of the pathophysiology of craniocervical anomalies is warranted to identify patient selection criteria and ideal level of fixation.