Analysis of the mutual influence of cervical sagittal balance parameters in children in norm and with Down syndrome

Objective. To analyze the correlations and dependencies of parameters of the cervical sagittal balance, as well as the corresponding compensatory mechanisms on the example of children without orthopedic pathology and children with Down syndrome.

Material and Methods. Digital radiographs of 110 children were used to evaluate the mutual influence of cervical sagittal balance parameters. The age range was 4-17 years. Group 1 included 60 children without identified orthopedic pathology: 26 boys and 34 girls, with an average age 11 years (7.0–14.0 years). Group 2 included 50 children with Down syndrome: 24 boys and 26 girls, with an average age 9 years
(7.0–12.0 years). Based on the digital radiographs, eight key angular parameters of cervical sagittal balance were assessed: O–C2,
O–C7, C1–C2, C2–C7, C7S, T1S, TIA, NT. Statistical analysis of the data was performed using rank correlation analysis and multivariate regression.

Results. In the assessment of rank correlations, the leading positive correlation between the cervical lordosis and thoracic inlet angle (TIA) values was determined. Based on the results of multivariate regression, the main trends in the change in key angles of the cervical sagittal balance in children were determined. An increase in TIA by 1° leads to increase in the C2–C7 angle by an average of 0.6° (p = 0.004) and the C1–C2 angle by 0.4° (p = 0.028) for both girls and boys without identified orthopedic pathology. This rule is also equivalent when the TIA angle decreases with age. At the same time, girls have C2–C7 angle on average 2.9° (p = 0.021) larger and C1–C2 angle 1.2° (p = 0.112) larger than boys. Similar trends are true for children with Down syndrome, but with a less pronounced regression effect of factors. Thus, in children with Down syndrome, an increase in TIA by 1° is associated with a mean increase in the C2–C7 angle by 0.5° (p = 0.004) and  the C1–C2 angle by 0.2° (p = 0.035). Girls have C2–C7 angle on average by 3.1° (p = 0.018) larger than boys. A similar dependence could not be determined for the C1–C2 angle.

Conclusion. The cervical spine, despite its high mobility, has a clear connection with the underlying spine departments. In our work, we succeeded in proving that the thoracic input angle (TIA) having small variability for each specific child, is the basis for the formation of cervical lordosis C2–C7 and local lordosis at the level of C1–C2. The formulas obtained as a result of building the regression models allow, knowing the TIA value, the age and gender of the child, to calculate the theoretical value of C2–C7 and C1–C2 values. This may help to identify signs of both sagittal imbalance and atlantoaxial instability in different groups of children, including those with Down syndrome. At the moment, the obtained formulas are theoretical and need further validation.

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