Zeitschrift für Wirbelsäule

Assessment of the Possibilities of B-Mode Ultrasonography in the Diagnosis of Atlanto-Axial Rotary Subluxation in Children

Abstract

Abdullaeiv RY, Sharmazanova EP, Voronzhev IA and Abdullaev RR

Introduction: Among the traumatic injuries of atlantoaxial joint (AAJ) in children, a rotational subluxation in the C1-C2 segment is more common. The frequency of its occurrence in children less than 10 years varies from 34% to 73%, in newborns this injury is the most frequent among all spinal injuries (upto 54%). Radiography is the most common method for diagnosing rotational subluxation of the atlas, but has a number of limitations due to poor visualization of the soft tissue structures. MRI study is difficult to organize in newborns, in addition, this method is the most expensive. Ultrasonography is a cheap method, it allows using high-frequency sensors to provide visualization of the ligamentous apparatus and the spinal cord, which is very important in severe forms of trauma. Objective: The aim of the study was to evaluate the possibilities of X-ray and ultrasound imaging methods in diagnosing the Atlanto-axial rotary subluxation (AARS).

Materials and methods: Our survey was based on 28 (45.2%) newborns (group I) and 34 (54.8%) children aged 4-6 years (group II) who were diagnosed with AARS as a result of birth and mechanical trauma, respectively. The comparative group (CG) comprised 50 children - of them 12 newborns, 15 - under the age of 1 year, 23 - at the age of 4-6 years. Everyone children were given radiography, ultrasound and only 12 (19.3%) of them - MRI. Ultrasonographically were determined the structure of the transverse ligament (TL), the distance from the edge of the odontoid process (OP) to the inner lateral masses (LM: Lateral Masses) surface on both sides. The smallest value of this distance was denoted by D1, the largest by D2. Normally the difference between D2 and D1 did not exceed 0.5 mm. The degree of asymmetry was estimated by the formula: D2-D1/D1 × 100%, and normally ranged from 7% to 15%.

Results: According to roentgenological data, in 40.9% of the newborns the ossification nucleus was in the anterior arc C1 and the width of the x-ray gap of the anterior-atlas-axial joint was 1.5-2.0 mm. The average distance between the LM at C1 level in newborns was 16.19 ± 0.78 mm, in children under 1 year of age it was 18.01 ± 1.08 mm, at the age of 4-6 years - 27.87 ± 0.98 mm. At the age of 1 to 3 years, the frontal and posterior arcs of the atlas are fused, its anterior tubercle is clearly pronounced and has the shape of an elongated oval with thickened end plates. Complete ossification of the tooth C2 and its fusion with the vertebral body occurs at the age of 4-6 years. In the lateral projection, apart from the Crucellus joint, the width of the retro-tracheal space was determined, which is 4.5 ± 2 mm at the C1-C3 level, the posterior wall of the larynx and the trachea is normally even, parallel to the vertebral bodies. Ultrasonographically the thickness of the TL averaged 1.92 ± 0.14 mm - in neonates, 2.31 ± 0.17 mm - in children under 1 year and 2.69 ± 0.24 mm in children 4-6 years. The thickness of the synovial bag (gap) between the OP and TL was normally more than 1.5 mm. Cruciform ligament (CL) on the echogram had a mediumlow echogenicity, an even contour and a thickness of 1.6 to 2.5 mm, and an average of 1.83 ± 0.17 mm in newborns, 2.14 ± 0.15 mm in children 1 year and 2.35 ± 0.21 mm - in 4-6 years. On the axial ultrasonic section, the anteriorposterior dimension of the dural sac, the spinal canal (SC) and the spinal cord was determined. The sagittal size of the SC at the C1-C2 level in a newborn was 10.04 ± 0.42 mm, up to a year of 11.23 ± 0.37 mm, at the age of 4-6 years - 14,15 ± 0.51 mm, and the size of the spinal cord was: 5.45 ± 0.26mm, 5.63 ± 0.26mm and 7.32 ± 0.42mm, respectively. Ultrasonographically, the width between LM varied from 15.4 to 18.05 mm, in children with neurological symptomatology (NS) averaged 17.3 ± 0.9 mm, and in the subgroup without NS - 16.3 ± 0.8 mm, in the comparison group (CG) - 16.2 ± 0.7 mm, without significant differences. The average value of D1 for children with NS was 4.4 ± 0.3 mm, without NS, 4.6 ± 0.4 mm, and for CG - 5.3 ± 0.4 mm. The value of D2 was significantly different (P<0.05) between the children with NS (7.6 ± 0.7mm), without NS (6.8 ± 0.5mm), and for CG (5.9 ± 0.4 mm). The D1/D2 index in the groups was 0.6 ± 0.07; 0.7 ± 0.04 and 0.9 ± 0.08, respectively. At the same time, the difference in the value of the D1/D2 index between newborns with AARS of both subgroups and healthy children had a high statistical significance (p<0.001). The degree of asymmetry of the position of OP with respect to LM in health newborns varied within the range of 6.9-15.1% and averaged 11.0 ± 4.1%. In the subgroup of children with AARS and NS, this indicator was 71.7 9.5%, without NS - 46.6 ± 8.3% (p<0.001). Moderate asymmetry in the range of 21-40% among children with NS was observed in 15.4 ± 10.4%, and without NS - in 60.0 ± 13.1% of cases (p<0.01).Expressed asymmetry over 40% among children with NS was observed in 84.6 ± 10.4%, and without NS - in 40.0 ± 13.1% of cases (p<0.01).

Conclusion: The ultrasound symptoms of the rotational subluxation of the atlas in children are: the asymmetry of the odontoid process relative to the lateral masses of more than 1 mm or 20%, the decrease in the gap between the odontoid process and the transverse ligament of less than 1 mm, the irregularity of the thickness of the transverse ligament, the asymmetry of the thickness of the pterygoid ligaments. Signs of a severe form of the rotational subluxation of the atlanta - the asymmetry of the odontoid process with respect to the lateral masses of more than 2.0 mm (or more than 60%), the D1/D2 index is less than 0.60, the absence of visualization of the gap between the odontoid process and the transverse ligament, deformation of the anterior dural space with the presence of a hyperechoic mass in it, an increase in the dimension of the posterior dural space.