Sagittal alignment of cervical spine in adult idiopathic scoliosis

Alignment of the cervical spine (CS) in adolescent idiopathic scoliosis (IS) as well as in asymptomatic adult populations has recently been studied and described as being less lordotic in the adolescent IS population. However, few studies have examined the sagittal alignment of the CS in adult IS or its association with other radiological variables and clinical relevance. The aim of this study is to analyse the sagittal alignment of CS in adult IS and its association with age, alignment of the thoracic, lumbar and global spinal column as well as health-related quality of life (HRQOL) parameters. A retrospective review of prospectively collected data from a multicenter database was performed. Of 468 consecutive adult IS patients, 213 were included in the study; the remainder were excluded due to poor quality X-rays where the CS was not properly visible, or previous surgery. X-rays were measured for the following CS parameters: [Cranial base-C2 (C0-C2) lordosis, C2-C7 lordosis, thoracic (T1) slope, thoracic inlet angle (TIA) and odontoid (Od)-T1 offset using a measurement software]. These measurements were then evaluated for possible associations with patient age and with pre-existing alignment parameters and HRQOL scores using Pearson correlation tests. The average and standard deviations for CS alignment parameters were 32.3A degrees A A +/- A 10.2A degrees for C0-C2; 5.7A degrees A A +/- A 14.1A degrees for C2-C7; 23.9A degrees A A +/- A 11.3A degrees for T1 slope, 70.5A degrees A A +/- A 14.7A degrees for TIA and 20.8A degrees A A +/- A 16.5A degrees for Od-T1 offset. CS alignment showed a significant (p < 0.05) correlation with age, T kyphosis and several other sagittal alignment parameters such as sagittal vertical axis (SVA), global tilt and T1 sagittal tilt, but not with the HRQOL parameters. The sagittal alignment of the CS in adult IS is less lordotic than the normal average while less kyphotic than that of IS of a younger age. It correlates with age, thoracic kyphosis and some global sagittal alignment parameters. These findings suggest that CS alignment is likely a component of the global sagittal alignment strongly affected by thoracic kyphosis, and most probably does not affect HRQOL by itself.