Normal Patterns of Sagittal Alignment of the Spine in Young Adults Radiological Analysis in a Korean Population

Study Design. Radiological analysis and classification of normal patterns of sagittal alignment of the spine. Objective. To classify the patterns of sagittal alignment of the spine in young asymptomatic adults and analyze the differences in the various spinal and pelvic parameters according to these patterns. Summary of Background Data. Previous studies reported that the overall sagittal pattern and balance were more important than the normative values. There are few studies on white populations, classifying the normal patterns of sagittal curvature, and no studies on Asian populations. Methods. Whole spine, standing lateral radiographs of 86 Korean volunteers were taken. The pelvic and spinal parameters (total thoracic kyphosis, horizontal thoracic level, thoracolumbar junctional angle (TLJA), total lumbar lordosis, lower lumbar lordosis, horizontal lumbar level (HLL), lumbar inclination, pelvic tilt, sacral slope (SS), pelvic incidence, spinal balance, spinopelvic balance, and sacropelvic balance) were measured and the correlations of all parameters were analyzed. The volunteers were classified in to three types according to their HLL. The data were analyzed statistically to determine the differences in the parameters and balance between the three types. Results. The HLL showed a significant correlation with the lumbar inclination, junctional level, TLJA, spinal balance, spinopelvic balance, and SS on analyzing the correlation of the parameters. As HLL moved caudally, the TLJA and lumbar inclination increased, whereas the lower lumbar lordosis, pelvic incidence, and SS decreased and spinal balance became more negative. There were no significant differences in total thoracic kyphosis and sacropelvic balance between the three types. Conclusion. The patterns of sagittal alignment could be classified into three types showing that the spinal balance becomes more negative, the lumbar inclination and TLJA increase, the SS and pelvic incidence decrease, and lumbar lordotic curves becomes shorter as the patterns of sagittal curvature move toward type 3. This classification in young adults should be considered individually as a reference for surgeons aiming to restore the lumbar lordosis and sagittal alignment in degenerative lumbar fusion surgery.