Dynamic computerized tomography of the occiput-atlas-axis complex in trauma patients with odontoid lateral mass asymmetry

Inter-examiner reliability of radiographic measurements from Open-mouth lateral bending cervical radiographs

Background

Following head and neck trauma, the involvement of the cranio-cervical junction (CCJ) and its contribution to a patients transition to chronic pain, is poorly understood. The detection of hypermobility in this region is dependent on clinical examination and static imaging modalities such as x-ray, CT and MRI. Sagittal plane hypermobility of the CCJ is evaluated using saggital view, flexion-extension cervical radiographs. Frontal plane hypermobility is typically assessed using lateral bending and open mouth cervical radiographs. Unfortunately there is no established reliability surrounding the use of these measures. This study explores the reliability of radiographic measurements of lateral-bending open-mouth cervical radiographs.

Methods

Cervical open-mouth lateral-bending X-ray images were collected from 56 different patients between 18 and 60 years of age patients following cervical spine injury. These images were interpreted by two musculoskeletal radiologists and two clinicians (physiatrist and chiropractor), using a standard set of measurements. Measurements included qualitative and quantitative assessments of the amount of asymmetry noted between various osseous landmarks. Reliability statistics were calculated for levels of agreement using kappa coefficients (κ) and Intraclass Correlation Coefficients (ICC) for dichotomous and continuous variables, respectively.

Results

Reliability (κ) for qualitative assessments were moderate to substantial for asymmetry of neutral C2 spinous position, dens-lateral mass spacing, and “step off” between the lateral borders of the articular pillars of C2 and C1 lateral mass (κ range = .47–.78). ICC values for the quantitative measurements of dens-lateral mass spacing and “step off” between the lateral borders of the C2 articular pillars and C1 lateral mass were moderate to excellent (ICC range = .56–.97).

Conclusions

The qualitative and quantitative measurements used in this study demonstrated good to excellent inter-examiner reliability. Correlation with clinical findings is necessary to establish the utility of these measurements in clinical practice.

Evaluation of lateral atlantodental interval asymmetry in the pediatric age group: normative values

OBJECTIVE The revelation of normative radiographic measurements for the developing pediatric spine is incomplete. The purpose of this analysis was to determine the normal range of asymmetry of the lateral atlantodental interval (LADI) and define age- and sex-related differences. METHODS A total of 3072 children aged 0-18 years who underwent CT scanning of the cervical spine were identified at Riley Hospital for Children between 2005 and 2017. Patients were stratified by sex and age (in years) into 36 cohorts. Following this stratification, patients within each group were randomly selected for inclusion until 15 patients in each group had been measured (quota sampling). A total of 540 patients were included for study. Right and left linear measurements were performed in the CT axial plane at the C-1 midlateral mass level. RESULTS The overall mean difference between the right and left LADI was 0.09 ± 1.23 mm (range -6.05 to 4.87 mm). The magnitude of this asymmetry remained statistically insignificant across age groups (p = 0.278) and sex (p = 0.889). The intraclass correlation coefficient was 0.805 (95% CI 0.779-0.829). CONCLUSIONS Asymmetry of the LADI is not unusual in asymptomatic children. There is no appreciable difference in magnitude of this asymmetry across age ranges and sex. Measurement of LADI asymmetry shows "good" reliability and is easy to perform. Pediatric neurosurgeons, emergency department physicians, and radiologists should be aware of normative values of asymmetry when interpreting CT scans of the cervical spine. This may prevent unnecessary further workup with dynamic CT or MRI.

Asymmetry of the Odontoid Lateral Mass Interval in Pediatric Trauma CT: Do We Need to Investigate Further?

BACKGROUND AND PURPOSE

Odontoid lateral mass interval asymmetry can be within the normal spectrum or the result of traumatic atlantoaxial injury. We sought to set radiographic guidelines for further investigation of odontoid lateral mass interval asymmetry in cervical spine CT studies of pediatric trauma patients.

MATERIALS AND METHODS

Fourteen children with C1-2 ligamentous injury or atlantoaxial rotational fixation/subluxation were retrospectively identified. We identified an additional 56 children fulfilling the following inclusion criteria: 1) They underwent C-spine CT to exclude traumatic injury, and 2) C-spine clearance and follow-up. Those were matched for age, sex, and severity of traumatic insult with the injured group. Clinical data were collected, and we measured the following parameters: anterior atlantodental interval; odontoid lateral mass interval; and the rotation of the head, C1, and C2.

RESULTS

A significant difference (P < .001) was found between the groups in cervical tenderness and torticollis. There was a significant difference in the atlantodental interval value (3.3 ± 0.8 mm in injured and 2.2 ± 0.5 mm in noninjured). The directionality of head, C1, and C2 rotation was significantly (P < .05) more toward the same direction in the noninjured group. We found significant linear correlation between head rotation and ipsilateral odontoid lateral mass interval asymmetry only in the noninjured at C1-2. With multivariant analysis, the presence of cervical tenderness and an abnormal atlantodental interval were the most significant variables.

CONCLUSIONS

Odontoid lateral mass interspace asymmetry in the absence of cervical tenderness and with a normal atlantodental interval is likely in the normal range and need not be further investigated.

A three-dimensional study of the atlantodental interval in a normal Chinese population using reformatted computed tomography

The atlantodental interval has been usually used for the evaluation of atlantoaxial instability. However, the asymmetry of the lateral atlantodental interval is occasionally found in healthy individuals. Controversy therefore exists as to the clinical significance of this asymmetry in patients after trauma. The purpose of this study was to determine the normal range of atlantodental intervals in normal individuals using reformatted computed tomography. In this study, C1-C2 vertebrae were imaged in 230 adult patients by a Lightspeed Vct CT (General Electric, CT, USA) with a slice thickness of 0.625 mm. After reformatting the original images, the anterior atlantodental interval (AADI) and lateral atlantodental interval (LADI) were measured. The AADI was found to be 1.83 ± 0.46 mm (0.9-3.4 mm) in males and 1.63 ± 0.43 mm (0.5-3.2 mm) in females. The AADI was significantly greater in males than in females (p < 0.05). The 95% confidence interval for AADI was 1.75-1.90 mm in males and 1.54-1.72 mm in females. No statistically significant differences were found between males and females in the left and right LADI, and LADI asymmetry. The left LADI was found to be 3.38 ± 0.87 mm (1.7-6.0 mm), and the right LADI was 3.42 ± 0.84 mm (1.7-5.9 mm) in males, while the left LADI was 3.30 ± 0.73 mm (1.5-5.3 mm) and the right LADI was 3.37 ± 0.92 mm (1.7-5.9 mm) in females. The 95% confidence interval for left LADI was 3.23-3.52 and 2.94-3.25 mm, and for right LADI was 3.27-3.56 and 3.18-3.56 mm in males and females, respectively. The mean asymmetry of LADI was 0.76 ± 0.66 mm (0.0-3.5 mm) in males and 0.73 ± 0.70 mm (0.0-3.7 mm) in females. The 95% confidence interval for LADI asymmetry was 0.65-0.87 mm in males and 0.59-0.88 mm in females. Most of the population was found to have an asymmetry ranging between 0.1 and 2.0 mm. The current study shows that LADI asymmetry is common in patients without any cervical spine abnormalities. LADI asymmetry may be a normal anatomic variant and there is no evidence to confirm that LADI asymmetry is a sensitive or specific indicator of traumatic atlantoaxial instability. Radiologists and clinicians should be aware of this normal range of asymmetry when interpreting CT scans of the atlantoaxial region.

The radiological assessment of injuries to the atlanto-axial-occipital complex (C1 and C2 vertebrae)

Upper cervical spine injuries are a source of diagnostic difficulty. While CT scanning is being used more widely in assessing the cervical spine, especially in unconscious patients, plain film radiology remains an important first point of assessment in the UK in less dramatic situations. We summarise relevant literature on plain film radiology of the upper cervical spine, and make some suggestions for structured evaluation of films under review.

Quantification of C2 cervical spine rotatory fixation by X-ray, MRI and CT

Atlanto-axial rotatory displacement is known to be a cause of childhood torticollis and may as well be responsible for chronic neck pain after rear-end automobile collisions. The objective was to determine whether quantification of C2 malrotation is possible by plain radiographs in comparison to CT as the golden standard. MR imaging was evaluated as to whether it was of equal value in the detection of bony landmarks. C2 vertebra of five human cadaveric cervical spine specimens, ligamentously intact, were rotated using a Steinmann pin in steps of 5 degrees up to 15 degrees right and 15 degrees left. Plain radiographs, CT and MRI images were taken in each rotational step. Data were analyzed for quantification of C2 rotation by three independent examiners. A rotation of 5 degrees led to a spinous process deviation (SPD) from the midline of 3 mm as measured on an a.p. plain radiograph. A coefficient of rotation was calculated (1.62 degrees mm(-1)). Data analyzed by three examiners revealed a small coefficient of variation (0.03). MRI and CT measurements showed comparable results for the quantification of rotation; however, in both techniques the 15 degrees rotation was underestimated. Quantification of upper cervical spine malrotation was possible on plain radiographs using the SPD and a rotation coefficient. MRI and CT were equally successful in the assessment of C2 malrotation.

Unusual mechanism of lethal cervical spinal cord injury in a case of atlanto-axial diastasis

A case of traumatic cervical spinal cord injury due to congenital craniocervical abnormalities is described. The autopsy revealed evidence of hyperextension of the neck due to frontal impact, congenital occipitalization of the atlas accompanied by basilar invagination of the odontoid process and atlanto-axial diastasis. The subsequent narrowing of the spinal canal led to a predisposition for this unusual mechanism of spinal cord injury.