Comparison of Standing Sagittal Spinal Alignment in Asymptomatic Adolescents and Adults

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Abstract
A retrospective examination of the spine radiographs of 88 asymptomatic adolescents was performed to analyze the indices of regional and segmental sagittal spinal alignment in relation to the sagittal vertical axis as determined by the C7 plumb line. To determine the sagittal spinal alignment in asymptomatic adolescents and to correlate the sagittal vertical axis with the overall sagittal spinal balance and other indices of sagittal spinal alignment. In addition, to compare these results with previously established data for asymptomatic adults. Previous studies of sagittal spinal alignment have included subjects encompassing a wide range of ages. A previous study at the authors' institution established normative data for sagittal spinal alignment in asymptomatic adults. No previous study has reported on the correlation between the sagittal vertical axis and other measurements of sagittal spinal alignment in asymptomatic adolescents. Measurements obtained from the standing lateral spine radiographs of 88 asymptomatic adolescents (age range, 10-18 years) were collected and analyzed using statistical methods. These data were compared with previously established data for asymptomatic adults. There was a striking similarity in regional thoracic kyphosis and lumbar lordosis between adolescents and adults. Despite having similar regional and segmental sagittal alignments, adolescents had a significantly more negative sagittal vertical axis (mean, −5.6 cm) than adults (mean, −3.2 cm; P = 0.0001). Also, unlike that in adults, the sagittal vertical axis in adolescents was not significantly correlated with the distal segmental lumbar lordosis. The sagittal vertical axis in adolescents was significantly correlated with the level of thoracic kyphosis and the distances from the thoracic apex, lumbar apex, and T12 to the C7 plumb line. Sacral inclination, which is a determinant of hip extension and standing pelvic rotation, was correlated with the lumbar apex and the total and segmental lordosis, except at L5-S1. Asymptomatic adolescents tend to stand in greater negative sagittal spinal balance than asymptomatic adults, despite similar regional and segmental alignments in the thoracic and lumbar spine. The role of hip extension, spinopelvic axis rotation, and other sagittal alignment parameters in determining the sagittal vertical axis in adolescents warrants further study.