Variations in Sagittal Alignment Parameters Based on Age A Prospective Study of Asymptomatic Volunteers Using Full-Body Radiographs

Study Design.Cross-sectional cohort study.Objective.Describe age-stratified normative values of traditional and novel sagittal alignment parameters.Summary of Background Data.Full-body radiographic techniques can capture coronal and sagittal standing images from the occiput to the foot without stitching or vertical distortion. This provides an ideal method to evaluate measures of global alignment.Methods.Adults with no back or neck symptoms were recruited. Age, body mass index, Neck Disability Index, and Oswestry Disability Index scores were recorded. The following parameters were measured: center sacral vertebral line, Occiput-C2 (O-C2) lordosis, cervical lordosis (C2-C7, CL), thoracic kyphosis (T2-12, TK), T2-T5 kyphosis, T5-T12 kyphosis, thoracolumbar kyphosis (T10-L2), lumbar lordosis (L1-S1, LL), sacral slope, pelvic tilt, pelvic incidence (PI), knee flexion angle, global sagittal angle, T1-pelvis angle, C2-S1 sagittal vertical axis (SVA), C7-S1 SVA, Basion-C7 SVA, B-S1 SVA and Basion to the center of the femoral head SVA and PI minus LL. Comparisons of sagittal alignment parameters between different age groups were performed. A Pearson correlation was used to determine relationships.Results.One hundred fifteen volunteers had imaging suitable for analysis; average age as 50.1 years (range 22-78), average body mass index was 28, average Neck Disability Index was 3.44.4, and average Oswestry Disability Index was 1.74.9. CL (r=-0.34, P=0.001), T1-pelvis angle (r=0.44, P<0.001), knee flexion angle (r=0.42, P<0.001), global sagittal angle (r=0.56, P<0.001), and C7 SVA (r=0.46, P<0.001) all increased with age. LL decreased with age (r=0.212, P=0.039). We were able to establish a chain of correlation extending from the toes to the occiput and report age-based normative values for all parameters.Conclusion.We describe age-based normative sagittal alignment parameters in the adult spine with complete visualization from the occiput to the feet. We describe compensatory changes that occur to maintain sagittal balance. These values may be used as a reference for future studies.Level of Evidence: 4