Comparative characteristics of cervical sagittal balance parameters and atlantoaxial instability criteria in normal and Down syndrome children

BACKGROUND: Sagittal balance of the spine has received considerable development in recent years. However, most studies focused on the assessment of vertebral–pelvic parameters. The cervical spine has long received insufficient attention from researchers, but this trend has been changing. The study of cervical sagittal balance in children with Down syndrome is beneficial in approaching the preconditions of atlantoaxial instability. AIM: To perform a comparative analysis of cervical sagittal balance parameters and atlantoaxial instability criteria in normal and Down syndrome children. MATERIALS AND METHODS: Radiographs of the cervical spine in the neutral position in lateral projection and postural radiographs of 110 pediatric patients were analyzed retrospectively. The patients were divided into two groups: group 1 (normal), 60 children aged 4–17 years without spinal pathology, and group 2 (Down syndrome), 50 children aged 4–17 years with Down syndrome. The parameters of cervical sagittal balance (Oc-C2, Oc-C7, C1-C2, C2-C7, C2-C7H, C7S, Th1S, TIA, NT) and criteria for atlantoaxial instability (Nakamura angle, ADI, SAC-C1, SAC-C1/SAC-C4) were obtained, and data was statistically analyzed. RESULTS: Significant differences in the parameters C7S, Th1S, and TIA increased in children with Down syndrome. These parameters are involved in cervical lordosis; however, no significant differences in cervical lordosis angles were found. Furthermore, significant differences were noted in the criteria of atlantoaxial instability ADI, SAC-C1, and SAC-C1/SAC-C4 toward their decreasing in children with Down syndrome. CONCLUSION: In patients with Down syndrome, the indices of cervical lordosis are statistically greater than those in normal children. Moreover, the parameters of cervical lordosis in patients with Down syndrome do not differ from those in normal children. Therefore, during flexion, subcompensation of the cervical spine is observed in children with Down syndrome. Given the statistically smaller indicators ADI, SAC-C1, SAC-C1/SAC-C4, low neck muscle tone, and ligamentous hypermobility, these abnormalities can be considered as congenital predisposition factors for atlantoaxial instability in children with Down syndrome.