Sagittal Parameters of Global Spinal Balance

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Abstract
Prospective study of normal sagittal global spinal balance in the Caucasian adult population. To document values for parameters of global spinal balance in 709 asymptomatic adults without spinal pathology. Previous studies have investigated sagittal spinal balance in the normal population, but there is still a need for a large prospective database with normative values on the basis of gender and age. Spinosacral angle (SSA), spinal tilt (ST), and C7 translation ratio were evaluated in 709 asymptomatic adults (354 males and 355 females). Position of C7 plumbline relative to sacrum and hip axis (HA) was also assessed. Comparisons on the basis of gender were performed using analyses of covariance with age as covariate. Relationships between parameters and age were assessed using Spearman's coefficients. Mean SSA, ST, and C7 translation ratio were respectively 130.4° ± 8.1°, 90.8° ± 3.4°, and 0.1° ± 1.9°. Mean ± 2 standard deviations were respectively 110° to 150° for SSA and 85° to 100° for ST. Mean SSA and ST were higher in females but by less than 2°. C7 plumbline was behind the HA in 86% of subjects. Correlations between global balance and age were small (-0.1 ≤ r ≤ 0.1), with only 1 correlation reaching statistical significance (SSA vs. age; r = -0.1), reflecting a slight tendency for SSA to decrease with age. There was no relationship between ST and age. Asymptomatic adults tend to stand with a stable global balance and it is expected that 95% of normal adults have an SSA and ST between 110° to 150° and 85° to 100°, respectively. C7 plumbline in front of the HA is not necessarily associated with a spinal pathology. Results suggest that in adults, anterior displacement of C7 plumbline with respect to sacrum cannot be attributed solely to aging and should raise a suspicion for the risk of developing spinal pathology.