Basion-dens Interval Research Articles

Radiographic Indicators of Craniocervical Instability: Analyzing Variance of Normative Supine and Upright Imaging in a Healthy Population.

Single-institution retrospective review. To establish baseline ranges and variability of 7 radiographic measurements of the cervical spine in a healthy patient population as potential diagnostic tools for craniocervical instability. Craniocervical instability, common in patients with connective tissue disease such as Ehlers-Danlos Syndrome, often presents with a wide range of symptoms, including neck pain. Current diagnostic methods employ a range of clinical and radiographic features, but diagnostic challenges remain due to missed indications on static imaging and a lack of standardized measurement values and normalized variance. Seventy-two healthy patients with cervical imaging were analyzed. Surgimap software was used to annotate supine computed tomography images, flexion, extension, and neutral x-ray images for measurement. These measurements included the atlanto-dental interval, clival-axial angle, basion-dens interval, basion-axis interval, perpendicular basion to the inferior aspect of C2, also known as Grabb Oakes measurement, and the hard palate to C1 and hard palate to C2. Statistical analysis assessed differences among imaging modalities, and coefficients of variation were calculated for each measurement. Our cohort consisted of a total of 72 patients with a mean age of 64 (SD: 13.54). All measurements except for the basion-axial interval and atlanto-dental interval demonstrated a significant difference between extension and flexion x-ray measurements. clivo-axial angle, hard palate to C1, and hard palate to C2 demonstrated the lowest coefficients of variance across imaging modalities. Understanding normal variance in cervical measurements is invaluable for accurate CCI diagnosis. Using a cohort of healthy patients, this study delineates the distribution and spread of 7 cervical measurements, delineating reference values and variability in these key measurements and highlighting their potential for use as imaging markers for CCI. Level III.

Automated Segmentation and Diagnostic Measurement for the Evaluation of Cervical Spine Injuries Using X-Rays.

Accurate assessment of cervical spine X-ray images through diagnostic metrics plays a crucial role in determining appropriate treatment strategies for cervical injuries and evaluating surgical outcomes. Such assessment can be facilitated through the use of automatic methods such as machine learning and computer vision algorithms. A total of 852 cervical X-rays obtained from Gachon Medical Center were used for multiclass segmentation of the craniofacial bones (hard palate, basion, opisthion) and cervical spine (C1-C7), incorporating architectures such as EfficientNetB4, DenseNet201, and InceptionResNetV2. Diagnostic metrics automatically measured using computer vision algorithms were compared with manually measured metrics through Pearson's correlation coefficient and paired t-tests. The three models demonstrated high average dice coefficient values for the cervical spine (C1, 0.93; C2, 0.96; C3, 0.96; C4, 0.96; C5, 0.96; C6, 0.96; C7, 0.95) and lower values for the craniofacial bones (hard palate, 0.69; basion, 0.81; opisthion, 0.71). Comparison of manually measured metrics and automatically measured metrics showed high Pearson's correlation coefficients in McGregor's line (r = 0.89), space available cord (r = 0.94), cervical sagittal vertical axis (r = 0.99), cervical lordosis (r = 0.88), lower correlations in basion-dens interval (r = 0.65), basion-axial interval (r = 0.72), and Powers ratio (r = 0.62). No metric showed adjusted significant differences at P < 0.05 between manual and automatic metric measuring methods. These findings demonstrate the potential of multiclass segmentation in automating the measurement of diagnostic metrics for cervical spine injuries and showcase the clinical potential for diagnosing cervical spine injuries and evaluating cervical surgical outcomes.

Atlanto-occipital dislocation-A challenge with respect to making the diagnosis and treatment

The correct diagnosis and treatment of the atlanto-occipital dislocation (AOD) remains amajor challenge. To evaluate the different radiological diagnostic criteria for AOD and discuss potential treatment strategies based on acase with AOD and additional fracture of the atlas. A29-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 X‑lines-method, Wackenheim line, basion-dens interval (BDI), basion-axial interval (BAI) and occipital condyle-C1 interval (CCI). 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 asensitive and valid yet practical parameter. Powers' ratio and the BDI were less suited for assessing the diagnosis. The X‑lines-method, Wackenheim line and the BAI did not adequately detect the pathological situation. The AOD is asevere injury requiring immediate correct diagnosis for later adequate treatment results. Among the published parameters, the revised CCI proved to be apractical and valid parameter to detect AOD. For definitive treatment, the operative occipitocervical stabilization is regarded as the method of choice.

Reference values of four measures of craniocervical stability using upright dynamic magnetic resonance imaging

PurposeTo establish reference ranges for four most commonly used diagnostic measures of craniocervical instability (CCI) in three cervical sagittal positions. This necessitated development of a reliable measurement protocol using upright, dynamic MRI (udMRI), to determine differences in the extent of motion between positions, and whether age and sex correlate with these measures.Materials and MethodsDeidentified udMRIs of 50 adults, referred for reasons other than CCI, were captured at three positions (maximal flexion, maximal extension and neutral). Images were analyzed, providing measures of basion-axial interval, basion-axial angle, basion-dens interval (BDI) and the Grabb–Oakes line (GOL) for all three positions (12 measures per participant). All measures were independently recorded by a radiologist and neurosurgeon to determine their reliability. Descriptive statistics, correlations, paired and independent t-tests were used. Mean (± 2 SD) identified the reference range for all four measures at each craniocervical position.ResultsThe revised measurement protocol produced inter-rater reliability indices of 0.69–0.97 (moderate–excellent). Fifty adults’ (50% male; mean age 41.2 years (± 9.7)) reference ranges for all twelve measures were reported. Except for the BDI and GOL when moving between neutral and full flexion, significant extents of movement were identified between the three craniocervical positions for all four measures (p ≤ 0.005). Only a minor effect of age was found.ConclusionsThis is the first study to provide a rigorous standardized protocol for four diagnostic measures of CCI. Reference ranges are established at mid and ends of sagittal cervical range corresponding to where exacerbations of signs and symptoms are commonly reported.

Measuring the shape and dimensions of normal the bony structures in the craniovertebral junction from computed tomography images of the pediatric age group.

The aim of this study is to contribute to the literature by determining the morphometric reference values of the bony structures in the craniovertebral junction (CVJ) from computer tomography (CT) images of the pediatric age group. In this study, CT's of 151 simple trauma patients aged between 3 and 15 years between 2016 and 2020 were evaluated. All CT examinations were performed using a 32-slice CT and included images of the skull base and C1-C2 junction. A total of 10 measurements were obtained from these images, including Wachenheim clivus canal angle (WCA), Welcher basal angle (WBA), Cran-iocervical tilt angle (CCT), power ratio (PR), Atlantodens interval, McRae Line (MRL), McRae - Dens distance, basion-dens interval (BDI), basion-axis interval (BAI), and atlantooccipital measurement (AOM). In comparison between gender groups, MRL (p=0.011) and AOM (p<0.001) measurements were found to be significantly higher in males. McRae-Dens distance, BDI, and AOM were significantly higher in patients aged 3-9 years (respectively, p=0005, p=0.003, p<0.001), and BAI (p=0.001) was significantly higher in patients aged 10-15 years. The McRae - Dens distance (p=0.119) was similar between patients with and without terminal ossicle in odontoid apex. But BDI of patients without terminal ossicle was significantly higher (p=0.048). All parameters, except the WCA, WBA, CCT, and PR, were statistically significantly correlated with the patient age (respectively, p=0.21, p=0.13, p=0.70, p=0.99). In this study, the morphometric reference values of the bone structures at the CVJ were determined from the CT images of the pediatric age group.

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

BackgroundTraumatic 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. MethodsPatients ≥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. ResultsEight 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. ConclusionsOur 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.

Traumatic Atlanto-occipital Dislocation in Children Followed by Hydrocephalus – A Case Report and Literature Review

AbstractTraumatic atlanto-occipital dislocation (TAOD) are uncommon injuries associated with high immediate mortality rate and occurs more than twice in children than adults, due to biomechanical properties and immaturity of children's cervical spine. We report a pediatric patient with TAOD, who underwent occipitocervical stabilization and also developed a late hydrocephalus requiring a shunt procedure. A six-year-old boy was admitted to the emergency department after a car accident with refractory cervical pain. A cervical computed tomography (CT) scan showed an anterior C1–C2 level hematoma, and a dynamic CT scan demonstrated an increasing basion-dens interval on extension. Cervical magnetic resonance imaging (MRI) showed discontinuity of the tectorial membrane and diffused hyperintense signal on the left alar ligament. These findings were attributed to TAOD, and an occipitocervical fusion was performed. The pain and neurological status improved after surgery, but after 3 months he returned with persistent vomiting, headache, and a CT scan showing hydrocephalus. Then, a ventriculoperitoneal shunt was performed, improving the symptoms. One year after the injury, the patient remained asymptomatic, and a later radiography demonstrated satisfactory bone fusion. In conclusion, the decision-making process regarding treatment should consider several clinical and radiographic findings. Occipitocervical fusion is the treatment of choice, while hydrocephalus is not an unusual complication in children.

189. Radiographic predictors of mortality following atlanto-occipital dissociation

189. Radiographic predictors of mortality following atlanto-occipital dissociation

Analysis of Upper Cervical Spine Measurements in the Uninjured Pediatric Spine.

Only a small number of studies have offered normative data for the upper cervical spine in children and with some variation in findings. The aim of this study was to determine normal values for upper cervical spine measurements used in the assessment of upper cervical spine trauma in the pediatric population. One-hundred computed tomographic images of the cervical spine of children aged ≤16 years were included for analysis. All children were cleared of spinal injury. Anterior atlanto-dens interval (ADI), posterior atlanto-dens interval (PADI), basion-dens interval (BDI), Powers ratio, condylar-C1 interval (CCI), and lateral mass interval (LMI) were measured on the relevant sagittal or coronal images. Measurements for CCI and LMI were taken on each side. Mean age was 111 months (range 11-196 months). Sixty-two were male. Mean values (and ranges) of the measurements were as follows: BDI: 7.1 mm (3.6-12.2); ADI 2.8 mm (0.8-4.8); PADI 18.7 mm (14.1-23.2); Powers ratio 0.72 (0.59-1.0); CCI 2.0 and 2.0 (0.5-4.2); and LMI 3.2 and 3.3 mm (1.7-4.8). BDI (r = -0.488), ADI (r = -0.201), PADI (r = 0.264), and CCI (r = -0.468 and -0.454) all showed significant correlation with age. The Powers ratio was the most stable measurement across all age groups. Normal values were reported from a local pediatric population with a wide age range. Most values correlate with age to a degree, and so normal values may vary throughout childhood. A multicenter study is desirable to advance knowledge in this field. Current radiographic measures used to assess for possible ligamentous injury in the pediatric upper cervical spine correlate with age. Caution must be held when analyzing the upper cervical spine across a range of age groups in children.

Determination of cutoff values on computed tomography and magnetic resonance images for the diagnosis of atlantoaxial instability in small-breed dogs.

ObjectiveTo determine cutoff values for the diagnosis of atlantoaxial instability (AAI) based on cross‐sectional imaging in small‐breed dogs.Study designRetrospective multicenter study.Sample populationClient‐owned dogs (n = 123) and 28 cadavers.MethodsDogs were assigned to three groups: a control group, a “potentially unstable” group, and an AAI‐affected group, according to imaging findings and clinical signs. The ventral compression index (VCI), cranial translation ratio (CTR), C1‐C2 overlap, C1‐C2 angle, atlantoaxial distance, basion‐dens interval, dens‐to‐axis length ratio (DALR), power ratio, and clivus canal angles were measured on CT or T2‐weighted magnetic resonance (MR) images. Receiver operating characteristic (ROC) analysis was performed to define cutoff values in flexed (≥25°) and extended (<25°) head positions.ResultsCutoff values for the VCI of ≥0.16 in extended and ≥0.2 in flexed head positions were diagnostic for AAI (sensitivity of 100% and 100%, specificity of 94.54% and 96.67%, respectively). Cutoff values for the other measurements were defined with a lower sensitivity (75%‐96%) and specificity (70%‐97%). A combination of the measurements did not increase the sensitivity and specificity compared with the VCI as single measurement.ConclusionCutoff values for several imaging measurements were established with good sensitivity and specificity. The VCI, defined as the ratio between the ventral and dorsal atlantodental interval, had the highest sensitivity and specificity in both head positions.Clinical significanceThe use of defined cutoff values allows an objective diagnosis of AAI in small‐breed dogs. The decision for surgical intervention, however, should remain based on a combination of clinical and imaging findings.

Occult craniocervical dissociation on cervical CT: an under-appreciated presentation of craniocervical trauma requiring occipital cervical fusion.

Craniocervical dissociation is a rare and life-threatening injury that results from a significant hyperflexion-hyperextension force. Occult craniocervical dissociation is defined as an unstable craniocervical injury in the absence of atlanto-occipital joint space widening or other skull base line abnormality. The early and accurate diagnosis of craniocervical dissociation is crucial since the early diagnosis and subsequent stabilization with occipital-cervical fusion has been shown to reduce neurologic morbidity and mortality. Several normative skull base lines have been developed to predict craniocervical dissociation. The purpose of our study was to measure the atlanto-occipital joint space and four other common skull base lines in patients who underwent occipital-cervical fusion for post-traumatic craniocervical instability. Patients who underwent occipital-cervical fusion for craniocervical injury were identified retrospectively using a keyword search of radiology reports using Nuance mPower software. The cervical CT and MRI exams for these patients were reviewed and the atlanto-occipital joint space, Powers ratio, Wackenheim line, posterior axial line, and basion dens interval were measured. Detailed descriptions of craniocervical ligament injuries on MRI were recorded along with patient demographic information, clinical history, management, and outcome. Nine adult patients who underwent occipital-cervical fusion for an acute craniocervical injury were identified. Six patients demonstrated an atlanto-occipital joint space measuring 2mm or less on cervical spine CT with no additional abnormality in the Powers ratio, Wackenheim line, posterior axial line, or basion-dens interval. Three patients demonstrated widening of the atlanto-occipital joint space with two patients demonstrating an abnormality in at least two additional skull base lines. Clinical outcomes were variable with nearly half of the patients demonstrating persistent neurologic deficits, including one quadriplegic patient. A normal atlanto-occipital joint space and skull base line measurements on cervical CT demonstrated a low predictive value for detecting unstable craniocervical injuries. Occult craniocervical dissociation was present in two-thirds of patients who underwent occipital cervical fusion for acute, craniocervical trauma. A high clinical and radiologic index of suspicion for craniocervical trauma with subsequent follow-up cervical MRI to directly evaluate ligamentous integrity is necessary to accurately diagnose and triage patients with high velocity trauma.

Clinical and Radiological Clues of Traumatic Craniocervical Junction Injuries Requiring Occipitocervical Fusion to Early Diagnosis.

ObjectiveThe purpose of this study is to find the clinical and radiographic characteristics of traumatic craniocervical junction (CCJ) injuries requiring occipitocervical fusion (OC fusion) for early diagnosis and surgical intervention. MethodsWe retrospectively reviewed 12 patients with CCJ injuries presenting to St. Michaels Hospital in Toronto who underwent OC fusion and looked into the following variables; (1) initial trauma data on emergency room arrival, (2) associated injuries, (3) imaging characteristics of computed tomography (CT) scan and magnetic resonance imaging (MRI), (4) surgical procedures, surgical complications, and neurological outcome. ResultsAll patients were treated as acute spinal injuries and underwent OC fusion on an emergency basis. Patients consisted of 10 males and 2 females with an average age of 47 years (range, 18–82 years). All patients sustained high-energy injuries. Three patients out of 6 patients with normal BAI (basion-axial interval) and BDI (basion-dens interval) values showed visible CCJ injuries on CT scans. However, the remaining 3 patients had no clear evidence of occipitoatlantal instability on CT scans. MRI clearly described several findings indicating occipitoatlantal instability. The 8 patients with normal values of ADI (atlantodens interval interval) demonstrated atlantoaxial instability on CT scan, however, all MRI more clearly and reliably demonstrated C1/2 facet injury and/or cruciate ligament injury. ConclusionWe advocate measures to help recognize CCJ injury at an early stage in the present study. Occipitoatlantal instability needs to be carefully investigated on MRI in addition to CT scan with special attention to facet joint and ligament integrity.

The relationship between radiologic parameters and transverse atlantal ligament injury obtained from MRI scans in patients with an isolated atlas burst fracture: A retrospective observational study.

The treatment of an atlas burst fracture depends on whether transverse atlantal ligament (TAL) injury is present. We compared the radiologic parameters associated with the presence of a TAL injury as detected using magnetic resonance imaging (MRI), and verified whether the lateral mass displacement (LMD) criteria currently used to diagnose TAL injuries in atlas burst fractures are reliable or need revision.Thirty patients who presented with isolated atlas burst fractures were included in this retrospective observational study. We measured radiologic parameters, including LMD, atlanto-dental interval, basion-dens interval, internal lateral mass displacement, and external lateral mass displacement, in each patient at the time of initial presentation. The presence of TAL injury was evaluated using MRI. We compared the radiologic parameters and characteristics of patients who presented with TAL injury. We also determined the sensitivity and specificity of an LMD test to accurately diagnose TAL injury based on MRI. Finally, we compared the radiologic parameters according to the presence of surgical treatment and patient union status.Twenty patients presented with an intact TAL, while 10 patients had a TAL injury on MRI. LMD was significantly higher in patients with TAL injury (9.61 vs 3.73 mm, P < .001). In multivariable logistic regression analysis, LMD was also significantly higher in patients with TAL injury. The sensitivity and specificity of LMD for diagnosing TAL injury based on MRI in patients with isolated C1 fractures were 90% and 100%, respectively. The incidence of an LMD greater than 8.1 mm was statistically higher in patients than in those without TAL injury (90% vs 0%, P < .001).Nine patients underwent surgery for isolated atlas burst fractures, and 21 did not. LMD (9.56 vs 4.03 mm, P < .001) and fracture gap (7.96 vs 4.01 mm, P < .001) were significantly higher in patients who underwent surgery.Among the various radiologic parameters, LMD closely correlated with the presence of TAL injury, as patients with an LMD greater than 8.1 mm were more likely to have a TAL injury in the case of atlas burst fractures. LMD is a good method for predicting the presence of TAL injury if MRI is not available.

Radiologic predictors of in-hospital mortality after traumatic craniocervical dissociation.

Traumatic craniocervical dissociation (CCD) is the forcible dislocation of the skull from the vertebral column. Because most CCD patients die on scene, prognostication for those who arrive alive to hospital is challenging. The study objective was to determine if greater dissociation, based on radiologic measurements of CCD, is predictive of in-hospital mortality among patients surviving to the emergency department. All trauma patients arriving to our Level 1 trauma center (January 2008 to April 2019) with CCD were retrospectively identified and included. Transfers and patients without computed tomography head/cervical spine were excluded. Study patients were dichotomized into groups based on in-hospital mortality. Radiologic measurements of degree of CCD were performed based on the index computed tomography scan by an attending radiologist with Emergency Radiology fellowship training. Measurements were compared between patients who died in-hospital versus those who survived. After exclusions, 36 patients remained: 12 (33%) died and 24 (67%) survived. Median age was 55 years (30-67 years) versus 44 (20-61 years) (p = 0.199). Patients who died had higher Injury Severity Score (39 [31-71] vs. 27 [14-34], p = 0.019) and Abbreviated Injury Scale head/neck score (5 [5-5] vs. 4 [3-4], p = 0.001) than survivors. The only radiologic measurement that differed between groups was greater soft tissue edema at mid C1 among patients who died (12.37 [7.60-14.95] vs. 7.86 [5.25-11.61], p = 0.013). Receiver operating characteristic curve analysis of soft tissue edema at mid C1 and mortality revealed 10.86 mm or greater of soft tissue width predicted mortality with sensitivity and specificity of 0.75. All other radiologic parameters, including the basion-dens interval, were comparable between groups (p > 0.05). Among patients who arrive alive to hospital after traumatic CCD, greater radiologic dissociation is not associated with increased mortality. However, increased soft tissue edema at the level of mid C1, particularly 10.86 mm or greater, is associated with in-hospital death. These findings improve our understanding of this highly lethal injury and impart the ability to better prognosticate for patients arriving alive to hospital with CCD. Prognostic and Epidemiological, Level III.

Is It Necessary to Evaluate the Craniocervical Junction with Computed Tomoghraphy in Adolescent Spinal Deformities?

To assess the craniocervical junction (CCJ) by using radiological measurements in patients with adolescent idiopathic scoliosis (AIS) and Scheuermann?s kyphosis (SK), and to compare those reults with healthy adolescent population. Patients were assigned to three groups. Group 1 consisted of AIS patients, Group 2 consisted of patients with SK, and Group 3 was the control group who did not have any spinal disorder. The groups were matched based on age and gender. Major Cobb angle and kyphosis angle were measured on X-Ray. asion-axial interval (BAI), basion-dens interval (BDI), posterior atlantodental interval (PADI), anterior atlantodental interval (ADI), atlanto-occipital interval (AOI), and Power?s ratio were measured by computerized tomography. The results were compared in each group statistically. A total of 120 participants, comprised of 78 (65%) female and 42 (35%) male were included in the study. There was no statistically difference between 3 groups based on age and gender (p > 0.05). According to the measurements, Group 3 had significantly higher PADI measurements than Group 1 (p=0.01). The ADI measurements of Group 2 were significantly higher than those of Group 1 and Group 3 (p=0.01). Group 3 had significantly higher BDI measurements than Group 1 and Group 2. (p=0.01). The Power ratios of Group 1 and Group 3 were statistically higher than that of Group 2 (p=0.01). There were no statistically significant differences between the groups in terms of AOI and BAI measurements (p=0.84, p=0.18, respectively). The presence of AIS and SK may affect the measurement of CCJ, and it may be considered to evaluate instability of the region.

163. Is conservative treatment effective for unilateral sagitally split fractures of C1 lateral mass?

BACKGROUND CONTEXT A unilateral sagittal split fracture (USSF) of the C1 lateral mass (LM) is a rare variant of C1 atlas fracture. To date, definite treatment guideline of USSF of C1 LM has not been established. The integrity of transverse atlantal ligament (TAL) is a key factor to determine the stability in C1 atlas fracture. However, the effect of TAL injury on treatment outcomes is controversial in USSF of C1 LM. Previous study of small case series reported that despite the TAL competency, conservatively-treated USSF of C1 LM causes late deformity of occipitocervical junction requiring major reconstructive surgery. PURPOSE Therefore, we performed the current study to investigate these two issues in USSF of C1 LM and suggest appropriate treatment guideline. STUDY DESIGN/SETTING Retrospective case analyses. PATIENT SAMPLE Twenty-six consecutive cases of USSF of C1 LM were included from 5 trauma centers of tertiary university hospitals. The fractures associated with other cervical spines, such as C2 and occiput, were excluded from the study. The mean age was 52 years old; 16 were male and 10 were female. OUTCOME MEASURES The radiologic outcomes were evaluated by comparing initial presentation and last follow-up in two groups. Clinical outcomes were evaluated by visual analog scale (VAS) and Odom's criteria. METHODS Of the total cases,16 were TAL injury group (9 type I and 7 type II according to Dickman's classification) and 10 were TAL intact group. All cases were treated by conservative measures including rigid brace or halovest for 12 weeks. The mean follow-up was 16 months (range, 12-47 months). Three spine surgeons measured radiologic parameters on lateral radiograph and open mouth view of cervical spine, 2-dimensional reconstructed CT scans and MRI of initial and last follow-up: total LM displacement (LMD), unilateral LMD of fracture side, atlanto-dental interval (ADI), clivus canal angle (CCA), atlanto-occipital joint axis angle (AOJAA), and basion-dens interval (BDI). The averages of three measurements were used as final results. RESULTS At the last follow-up, for TAL intact group, total LM displacement (LMD), unilateral LMD of fracture side, atlanto-dental interval, basion-dental interval, clivus canal angle, and atlanto-occipital joint axis angle were maintained compared to initial presentation. However, for TAL injury group, all radiological parameters were worsened. The worsening of radiological parameters was more severe in type I injury than type II injury except for total LMD and unilateral LMD. Neck VAS significantly decreased and patient's satisfaction was higher in TAL intact group compared to TAL injury group. CONCLUSIONS Conservative treatment for USSF of C1 LM with TAL injury failed to achieve healing of fracture site, which caused deterioration of lateral displacement of C1 LM. This caused coronal and sagittal malalignment of occipitocervical junction, resulting in unsatisfactory clinical outcomes. Our results suggest that early surgical treatment should be considered as the first choice treatment for USSF of the C1 LM, especially type I TAL injury. However, conservative treatment may be sufficient for USSF of the C1 LM with TAL intact. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

Morphometric changes at the craniocervical junction during childhood.

Current understanding of how the pediatric craniocervical junction develops remains incomplete. Measurements of anatomical relationships at the craniocervical junction can influence clinical and surgical decision-making. The purpose of this analysis was to quantitatively define clinically relevant craniocervical junction measurements in a population of children with CT scans that show normal anatomy. A total of 1458 eligible patients were identified from children between 1 and 18 years of age who underwent cervical spine CT scanning at a single institution. Patients were separated by both sex and age in years into 34 groups. Following this, patients within each group were randomly selected for inclusion until a target of 15 patients in each group had been reached. Each patient underwent measurement of the occipital condyle-C1 interval (CCI), pB-C2, atlantodental interval (ADI), basion-dens interval (BDI), basion-opisthion diameter (BOD), basion-axial interval (BAI), dens angulation, and canal diameter at C1. Mean values were calculated in each group. Each measurement was performed by two teams and compared for intraclass correlation coefficient (ICC). The data showed that CCI, ADI, BDI, and dens angulation decrease in magnitude throughout childhood, while pB-C2, PADI, BAI, and BOD increase throughout childhood, with an ICC of fair to good (range 0.413-0.912). Notably, CCI decreases continuously on coronal CT scans, whereas on parasagittal CT scans, CCI does not decrease until after age 9, when it shows a continuous decline similar to measurements on coronal CT scans. These morphometric analyses establish parameters for normal pediatric craniocervical spine growth for each year of life up to 18 years. The data should be considered when evaluating children for potential surgical intervention.

Part 1: CBCT EVALUATION OF ATLANTOAXIAL/ATLANTO-OCCIPITAL JOINTS FOR CERVICAL INSTABILITY RISK ASSESSMENT

Background In dental radiography, the vertical atlantoaxial index (VAAI)1 measures the vertical relationship of the atlas and the axis. Based on prior studies, value less than 0.8 might present a predisposition toward cervical instability. The Powers ratio (PR) is the ratio between the distance of 2 lines: (B–P): from basion to posterior arch of C1 (O–A): from opisthion to the anterior arch of atlas. The normal ratio is 1:1, if the ratio exceeds 1, it indicates atlanto-occipital instability. The basion–axial interval (BAI) is the horizontal distance between basion and posterior dens.4 The basion–dens interval (BDI) is the distance between the basion and the tip of the dens.4 Objective The objective of this study was to determine the potential risk for atlantoaxial/atlanto-occipital instability2 in patients who underwent cone beam computed tomography (CBCT) imaging of the head. The research was conducted at the Oral and Maxillofacial Radiology clinic of the University of Pennsylvania School of Dental Medicine (Philadelphia, PA). Materials and Methods After institutional review board approval, a preliminary study was performed on patients undergoing either preimplantation assessment of jaws or evaluation of atypical facial pain, and measurements were recorded. A total of 50 CBCT volumes were identified for the selected craniocervical cephalometric measurements. Analysis of the CBCT volumes and cephalometry were performed to record various craniocervical measurements and determine the potential risk of atlantoaxial atlanto-occipital instability. The measurements were done by using the midsagittal-view CBCT images. These measurements included BAI, BDI, VAAI, and PR. It was anticipated that these measurements would provide a risk estimate for cervical instability that could potentially result in spinal cord injury. All CBCT volumes were acquired by using the Carestream CS9300 machine (Carestream, Atlanta, GA). Results Based on the preliminary results, the average VAAI measurement was 0.7626, the average BAI was 4.970 mm, the average BDI was 5.043 mm, and the average PR was 0.6961. Discussion Apart from VAAI, BDI, and BAI, the PR3 was utilized in this study to find out the atlantoaxial dissociation (normal PR = 1:1). A ratio over 1 indicates atlanto-occipital dissociation (AOD. BAI is the horizontal distance between basion and the posterior cortex of the axis (normal ≤12 mm). BDI is the distance between the basion and the tip of the dens (normal ≤8.5 mm). Both BAI and BDI are used to diagnose AOD injuries.

Measurements in cervical vertebrae CT of pediatric cases: normal values

This study aims to determine the normal limits of atlanto-dental interval (ADI), basion-dens interval (BDI), basion-cartilaginous dens interval (BCDI), and prevertebral soft tissue thickness (PVSTT) according to age groups for normal pediatric cases. CT images of 256 pediatric patients aged between 1 and 15years were retrospectively evaluated. ADI, BDI, BCDI and PVSTT measurements were performed. Upper normal limit (UNL) values for ADI were 2.65-4.8mm. UNL values for PVSTT were found to be 6.9mm at C1 level, 6.7mm at C2 level, 9.3mm at C3 level, 14.2mm at C4 level, 14.1mm at C5 level, 13.8mm at C6 level and 12.8mm at C7 level. The maximum value of BDI in the group with non-ossified os terminale was 12mm, and in the group with ossified os terminale it was 10mm. The UNL of BCDI determined for females was 5.1mm, while the UNL for males was 5.6mm. We propose the obtained values as the UNL values for ADI, BDI, BCDI and PVSTT on CT images in the pediatric population from 1 to 15years.

Basion-Cartilaginous Dens Interval: An Imaging Parameter for Craniovertebral Junction Assessment in Children.

Widening of the basion-dens interval is an important sign of cranioverterbral junction injury. The current literature on basion-dens interval in children is sparse and based on bony measurements with variable values. Our goal was to establish the normal values of a recently described new imaging parameter, the basion-cartilaginous dens interval in children. Three hundred healthy pediatric patients (0-10 years of age) were selected retrospectively. These patients were divided into 3 different groups: A (0-3 years), B (3-6 years), and C (6-10 years). The basion-cartilaginous dens interval was calculated on the sagittal MPR image of cervical spine CT in a soft-tissue window. The mean, SD, and the upper limit of normal (mean +2 SDs) of the 3 groups were calculated, and statistical tests were used to check for significant differences of the basion-cartilaginous dens interval among these 3 groups. The upper limits of the basion-cartilaginous dens interval for the 3 groups were 5.34 mm in group A, 5.64 mm in group B, and 7.24 mm in group C. There were statistically significant differences in the basion-cartilaginous dens interval values among the 3 groups. There was no statistically significant difference in basion-cartilaginous dens interval values between groups A and B; however, values in group C were significantly different from those in both A and B. There was no statistically significant difference in the basion-cartilaginous dens interval values between males and females. The basion-cartilaginous dens interval is a novel imaging parameter to assess cranioverterbral junction integrity in children, which includes the nonossified cartilage in the measurement.