Introduction: Individuals maintain specific alignment relationships from the skull to the pelvis to maintain painless upright posture. Purpose: evaluate alignment correlations from the cervical spine to the pelvis to determine regional postural adaptations needed to maintain optimal sagittal position and maintenance of horizontal gaze.
Methods: Adult volunteers (n=55; 27 men, mean age=45 years; range 20-77) without history of chronic low back pain or back surgery were evaluated by full-length standing radiographs. Measurements included: C2-C7 cervical lordosis (CL), T4-T12 thoracic kyphosis (TK), L1-S1 lumbar lordosis (LL), pelvic tilt (PT), sagittal vertical axis (SVA), pelvic incidence (PI) and difference between PI and LL (PI-LL). Study cohort was stratified by age (20-39, 40-59, =60 years). Lordosis was denoted positive, kyphosis denoted negative.
Results: Average (SD) regional sagittal parameters were: CL=+11.7° (11), TK=-39.5° (12), LL=+59.6° (11), PI=53.3° (10), PT=14.2° (7) and SS=39.1° (9). Average (SD) global alignment parameters were: SVA=-12mm (41), PI-LL=-6.4° (10) and T1-slope=-24.2° (9). A chain of correlation from the pelvis to the cervical spine was identified: PI and LL (r=0.52, p<0.001), LL and TK (r=-0.34, p=0.011) and TK and CL (r=-0.51, p<0.001). In addition, PT correlated with CL (r=0.310, p=0.021) and CL correlated with SVA (r=0.305, p=0.024). Comparison between age groups demonstrated patients =60 years had larger CL (22.2°) than patients 20-39 years (9.4°; p<0.05) and patients 40-59 years (CL=6.6°; p<0.05). Older patients had higher SVA (22.4mm vs. -28.5, p<0.001) and T1-slope (-31.6° vs. -22°, p=0.001), compared to 20-39 year age group. No significant differences were found between the two younger groups.
Conclusions: A global understanding of sagittal alignment interactions for a wide age range of asymptomatic patients is essential to accurately evaluate and treat adult spinal deformity patients. This study reveals global interactions of the regional curvatures along the entire axial spine including the pelvis in an adult volunteer population.
Patient Care: This research improves our ability to effectively evaluate and treat spinal deformity patients by enhancing our understanding of global sagittal spinal alignment interactions.
Learning Objectives: By the conclusion of this presentation, participants should: (1) appreciate that there are alignment relationships throughout the mobile axial spine and pelvis needed to maintain optimal sagittal position in the asymptomatic adult, (2) appreciate the need to understand alignment and compensatory mechanisms that occur along mobile axial spine and pelvis to maintain upright posture when evaluating patients with spinal disease.