Radiographic appearance of the odontoid lateral mass interspace in the occipitoatlantoaxial complex

Three-dimensional computed tomography analysis of the atlanto-dental interval in a healthy Karachi population: a single-center retrospective cross-sectional study

Background

The atlantoaxial joint has a complex anatomical configuration and has a wide range of mobility. Traumatic, inflammatory, and neoplastic joint pathologies frequently affect this joint. The aim of this retrospective cross-sectional study was to evaluate the atlanto-dental intervals (ADI) in patients who underwent computed tomography (CT) scans of the neck and cervical spine in at a Tertiary Care Hospital in Karachi, Pakistan.

Methods

This was a retrospective cross-sectional study conducted at a tertiary care hospital in Karachi between 1 January 2021 and 31 December 2021, following approval from the hospital ethical review committee. Patients above the age of 15 who underwent CT scans were included, while individuals with a history of cervical trauma, infection, rheumatoid arthritis, or congenital anomalies, as well as those younger than 15 years old, were excluded. CT scans were performed using a multidetector scanner utilizing a standardized protocol. Sagittal and coronal images were reconstructed. ADI measurements, including anterior ADI (AADI), posterior ADI (PADI), and lateral ADI (LADI) on both sides, were determined using appropriate bone window settings. A radiologist with a minimum of 3 years of experience analyzed the CT scans.

Results

The mean age of the patients was 49.3±17.7 years (age range: 16-85 years). The mean AADI was 1.4±0.4 mm, with a range of 0.0-2.1 mm. The mean PADI was 19.1±1.9 mm, with a range of 13.8-24.6 mm. The mean left LADI measurement was 3.3±1.2 mm with a range of 1.2-10.0 mm, and the mean right LADI measurement was 3.2±1.1 mm with a range of 1.2-6.3 mm.

Conclusion

Our study examined the ADI in patients who underwent CT scans of the neck and cervical spine in Karachi. The findings provide valuable insights into the relationship between ADI measurements, age, and sex. These results contribute to our understanding of the anatomical variations in this region, which may aid in the diagnosis and management of cervical spine disorders.

Diagnostic Benefit of MRI for Exclusion of Ligamentous Injury in Patients with Lateral Atlantodental Interval Asymmetry at Initial Trauma CT

Background Cervical spine CT is regularly performed to exclude cervical spine injury during the initial evaluation of trauma patients. Patients with asymmetry of the lateral atlantodental interval (LADI) often undergo subsequent MRI to rule out ligamentous injuries. The clinical relevance of an asymmetric LADI and the benefit of additional MRI remain unclear. Purpose To evaluate the diagnostic benefit of additional MRI in patients with blunt trauma who have asymmetry of the LADI and no other cervical injuries. Materials and Methods Patients who underwent cervical spine CT during initial trauma evaluation between March 2017 and August 2019 were retrospectively evaluated. Those who underwent subsequent MRI because of LADI asymmetry of 1 mm or greater with no other signs of cervical injury were identified and reevaluated by two readers blinded to clinical data and initial study reports regarding possible ligamentous injuries. Results Among 1553 patients, 146 (9%) had LADI asymmetry of 1 mm or greater. Of these, 46 patients (mean age ± standard deviation, 39 years ± 22; 28 men; median LADI asymmetry, 2.4 mm [interquartile range, 1.8-3.1 mm]) underwent supplementary MRI with no other signs of cervical injury at initial CT. Ten of the 46 patients (22%) showed cervical tenderness at clinical examination, and 36 patients (78%) were asymptomatic. In two of the 46 patients (4%), MRI revealed alar ligament injury; both of these patients showed LADI asymmetry greater than 3 mm, along with cervical tenderness at clinical examination, and underwent treatment for ligamentous injury. In 13 of the 46 patients (28%), signal intensity alterations of alar ligaments without signs of rupture were observed. Four of these 13 patients (31%) were subsequently treated for ligamentous injury despite being asymptomatic. Conclusion Subsequent MRI following CT of the cervical spine in trauma patients with lateral atlantodental interval asymmetry may have diagnostic benefit only in symptomatic patients. In asymptomatic patients without proven cervical injuries, subsequent MRI showed no diagnostic benefit and may even lead to overtreatment. © RSNA, 2021 Online supplemental material is available for this article.

Independent Correlation of the C1-2 Cobb Angle With Patient-Reported Outcomes After Correcting Chronic Atlantoaxial Instability

Objective

To investigate three-planar radiographic results and patient-reported outcomes (PROs) after correcting chronic atlantoaxial instability (AAI) by translaminar screw (TLS) and pedicle screw (PS) fixation, and to explore the potential association of atlantoaxial realignment with PRO improvements.

Methods

Twenty-three patients who underwent C1 lateral mass screw (LMS)-C2 TLS and 29 who underwent C1 LMS-C2 PS with ≥ 2 years of follow-up were retrospectively analyzed. Three-planar (sagittal, coronal, and axial) radiographic parameters were measured. PROs including the Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) score and the Short Form 36 Physical Component Summary (SF-36 PCS) were documented. Factors potentially associated with PROs were identified.

Results

The radiographic parameters significantly changed postoperatively except the C1–2 midlines’ intersection angle in the TLS group (p = 0.073) and posterior atlanto-dens interval in both groups (p = 0.283, p = 0.271, respectively). The difference in bilateral odontoid lateral mass interspaces at last follow-up was better corrected in the TLS group than in the PS group (p = 0.010). Postoperative PROs had significantly improved in both groups (all p < 0.05). Thereinto, NDI at last follow-up was significantly lower in the TLS group compared with PS group (p = 0.013). In addition, blood loss and operative time were obviously lesser in TLS group compared with PS group (p = 0.010, p = 0.004, respectively). Multivariable regression analysis revealed that a change in C1–2 Cobb angle was independently correlated to PROs improvement (NDI: β = -0.435, p = 0.003; JOA score: β = 0.111, p = 0.033; SF-36 PCS: β = 1.013, p = 0.024, respectively), also age ≤ 40 years was independently associated with NDI (β = 5.40, p = 0.002).

Conclusion

Three-planar AAI should be reconstructed by C1 LMS-C2 PS fixation, while sagittal or coronal AAI could be corrected by C1 LMS-C2 TLS fixation. PROs may improve after atlantoaxial reconstruction in patients with chronic AAI. The C1–2 Cobb angle is an independent predictor of PROs after correcting chronic AAI, as is age ≤ 40 years for postoperative NDI.

Torticollis Caused by Nontraumatic Craniovertebral Junction Abnormalities

Torticollis could be the only symptom and sign of craniovertebral junction (CVJ) abnormality. It could be difficult to identify CVJ abnormality as a cause of torticollis due to their rarity, especially for the subjects with torticollis caused by nontraumatic CVJ abnormalities. There has been no report to focus on nontraumatic CVJ abnormalities as a cause of torticollis. The objective of this study was to report 27 patients of torticollis caused by nontraumatic CVJ abnormalities, with the aim of helping clinicians to identify nontraumatic CVJ abnormalities as a cause of torticollis. This is a retrospective cohort study including 27 subjects who had torticollis caused by nontraumatic CVJ abnormalities. The CVJ was examined in terms of atlanto-occipital angle, atlanto-axial angle, and lateral and anterior atlanto-dens intervals for the evaluation of occipital condylar hypoplasia, rotation of atlanto-axial joint, and lateral and anterior shift of the dens, respectively. Abnormalities of the lower cervical or thoracic spine were also evaluated. Occipital condylar hypoplasia, rotation of atlanto-axial joint, and lateral shift of the dens were the most common CVJ abnormalities. The 18.5% of the subjects had concurrent anomalies of lower cervical or thoracic vertebrae along with CVJ abnormalities. Each subject had 2.22 ± 1.10 types of CVJ abnormalities on average. In conclusion, comprehensive evaluation of CVJ abnormalities is recommended for differential diagnosis of subjects with unexplained torticollis. Once CVJ abnormalities are identified, concurrent abnormalities of other vertebrae need to be evaluated.

Craniovertebral Junction Abnormalities in Surgical Patients With Congenital Muscular Torticollis

Our clinical experience led us to realize that craniovertebral junction (CVJ) abnormalities were common in surgical patients with congenital muscular torticollis (CMT). This study aimed to report the concurrence rate of CVJ abnormalities in surgical patients with CMT, along with comprehensive evaluation of type of concurrent CVJ abnormalities. This was a retrospective cohort study in a tertiary hospital, including 41 subjects who underwent surgical release for CMT at the mean age of 8.38 years. The presence of CVJ abnormalities was analyzed, using craniofacial 3-dimensional computed tomography images. The concurrence rate of CVJ abnormalities was 70% in surgical patients with CMT. Subjects with CVJ abnormalities had, on average, 1.48 abnormalities. The CVJ abnormalities were rotation and lateral shift of the atlanto-axial joint along with rotation of atlanto-occipital joint, where rotation of the atlanto-axial joint was most common (82.76%). There is no patient with anterior shift of the atlanto-axial joint. Chronic mechanical tension by the contracted unilateral sternocleidomastoid muscle of CMT could be responsible for concurrent CVJ abnormalities. The CVJ abnormalities are more common in the atlanto-axial joint than in the atlanto-occipital joint. In conclusions, CVJ abnormality seems to be a common concurrent skeletal complication of CMT, at least, in surgical patients. The CVJ abnormality might be included in the list of skeletal complications of CMT. If CVJ abnormalities are significantly more common in surgical patients with CMT, CVJ abnormalities might be one of predictors of surgical patients with CMT.

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.

Surface area congruence of atlas superior articulating facets and occipital condyles

OBJECTIVE

The purpose of this study was to compare the surface areas of 12 atlanto-occipital joints from 6 cadavers to determine how well their ipsilateral and contralateral surface areas matched.

METHODS

Three methods were used. Method 1 consisted of digitized photographs downloaded to the Able Image Analyser software program (Ljubljana, Slovenia; http://able.mulabs.com). The perimeters were measured and expressed as square millimeters. Method 2 consisted of a point count method using moulds of the joint surfaces produced by pressing aluminum paper, leaving a clear imprint for analysis. Method 3 consisted of drawing outlines of the molds from method 2 onto transparencies and assessing overlap.

RESULTS

Method 1 showed a moderate correlation of matched articular surfaces between the left C1 superior articulating surface and the left condyle (r = 0.573, P = .01). Method 2 showed moderate correlations between all surface areas that were analyzed. The matched pairs compared were left C1 superior articulating surface and left condyle (r = 0.588, P = .01) and right C1 and right condyle (r = 0.730, P = .001). The contralateral surfaces correlated were left C1 and right C1 (r = 0.596, P = .009) and right condyle and left condyle (r = 0.769, P = .000). Method 3 showed no statistically significant differences between surface areas.

CONCLUSIONS

All 3 methods revealed that the articular surfaces of the atlas and corresponding or contralateral condyle for specimens used in this study were not an exact match.

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.

Reproducibility of isometric strength: measurement of neck muscles

OBJECTIVE

To evaluate the repeatability of an advanced method of measuring the strength of functionally different groups of neck muscles using an isometric apparatus.

DESIGN

A repeated measures design was used within and between sessions.

BACKGROUND

Chronic neck pain has been associated with poor isometric neck strength. In rehabilitation, strength measurements may thus help to evaluate the basic condition and show whether or not treatments and exercises have been beneficial for improving strength. Previous tests have concentrated on testing strength while trying to bend forwards and backwards, but no biomechanics device, able to test rotator muscles, has been presented.

METHOD

The new isometric measurement device was used to test flexion, extension and also rotation strengths of normal subjects (n = 33).

RESULTS

Intratester repeatability was good with regard to all measured parameters.

CONCLUSIONS

With both tests performed on the same day and test comparisons between days, intratest repeatability was good with regard to all measured parameters.