Cervical and Cervicothoracic Sagittal Alignment According to Roussouly Thoracolumbar Subtypes

Study Design.Cross-sectional cohort.Objective.To determine normative radiographic sagittal cervical alignment in asymptomatic volunteers based on Roussouly thoracolumbar sagittal alignment subtypes.Summary of Background Data.Comprehension of differences in cervicothoracic alignment with respect to variations in thoracolumbar alignment is limited.Methods.Asymptomatic adults were recruited and the following parameters measured: PI, PT, SS, LL, orbital tilt, orbital slope, occipital slope and incidence, occiput-C2 lordosis, C2-7 lordosis, occiput-C7 lordosis, CBVA, T1 slope, cervicothoracic alignment, T2-5 kyphosis, and C2-C7 sagittal vertebral alignment (SVA). Each was classified into one of Roussouly's four thoracolumbar subtypes and cervical alignment parameters were compared between groups.Results.Eighty-seven individuals [male-23; female-64; average age 49±16 yr (22-77 yr)] were included for analysis. The four groups were not different by age, sex, and body mass index (BMI). Lumbopelvic parameters (PI, SS, PT, LL) were different between Roussouly types. Average values for all patients included: CBVA (-1±9°), occiput-C2 lordosis (28±9°), occiput-C7 lordosis (39±14°), C2-7 lordosis (11±14°), C2-7 SVA (21±9mm), T1 slope (25±9°), C6-T4 angle (5±8°), T2-5 angle (16±7°), thoracic kyphosis (47±13°). No sagittal radiographic alignment measurements of the cervical spine and cervicothoracic junction were different between groups, except for the global cervical lordosis (occiput-C7 Cobb), which was found to be lowest for Roussouly type 2 (35±14°) and highest for type 4 (48±14°) (P=0.01). Mean C2-C7 sagittal Cobb, T2-T5 sagittal Cobb, and T1 slope were not different between groups.Conclusions.In asymptomatic volunteers, normative sagittal alignment parameters of the cervical spine, cervicothoracic junction, and thoracic spine based on variations in thoracolumbar sagittal alignment, as proposed by Roussouly, are established. These data may guide surgical correction of cervicothoracic deformities to ensure appropriate restoration of normal cervicothoracic parameters to maintain good horizontal gaze and overall sagittal plane alignment.Level of Evidence: 3.