The evolution of sagittal segmental alignment of the spine during childhood

Study Design. Cross-sectional. Objectives. The purpose of this study is to describe the normative data of the sagittal plane on pediatric age population, and to document the evolution of sagittal alignment with growth. Summary of Background Data. Having normative data about the sagittal plane is an integral part in the planning of the three-dimensional reconstruction of the spine. Segmental sagittal plane analysis on adults has been studied thoroughly; however, there are inadequate data on children. Methods. A total of 151 children (72 girls, 79 boys) without musculoskeletal abnormality between the ages of 3 to 15 years were studied with the 36-inch standing lateral radiograph with the arms flexed at 30degrees. There were a minimum of 10 children, at least 4 of them from one sex, in each age group. Variables measured on the radiograms were as follows: segmental angulations from T1-T2 to L5-S1, angles of global kyphosis (T1-T12) and lordosis (L1-S1), segmental angulations of T2-T5, T10-T12, T10-L2, and L4-S1 levels, T1 and L1 offsets in millimeters, location of thoracic and lumbar apexes, and spinopelvic alignment measurements (angles of alpha and beta, sagittal vertebral axis, and sacropelvic translation). For statistical analysis, the children were grouped in terms of ages: Group I (3-6 years of age), Group II (7-9 years of age), Group III (10-12 years of age), and Group IV (13-15 years of age). Results. One-way analysis of variance showed significant differences between the following parameters among groups: segmental angulations of T1-T2 (P < 0.015), T10-L2 (P < 0.014), L4-S1 (P < 0.001), global kyphosis angle (P < 0.005), global lordosis angle (P < 0.000), thoracic apex (P < 0.007), T1 offset (P < 0.000), sagittal vertebral axis (P < 0.004), and beta angle (P < 0.000). As sagittal vertebral axis increases, there is found to be a higher L1 offset and lower thoracic apex, both of which result in leaning forward. With growing, total thoracic kyphosis and total lumbar lordosis particularly due to lower 2 motion segments were found to be increased, while thoracic apex moved upwards, T1 offset increased, and L1 offset decreased. Older children stood with a more negative SVA, and sacral inclination increased. Conclusion. Sagittal spinal alignment is found to be changing as a child grows. There is a statistically significant difference among different age groups, especially at cervicothoracic, thoracolumbar, and lumbosacral junctions. The position of the sacrum (inclination and translation), and spatial orientation, as well as the global magnitude of thoracic kyphosis, and lumbar lordosis changes with growth. These findings should be taken into consideration for the young patients who require spinal instrumentation. The question "whether sagittal alignment should be restored according to the normative data for the child's age or to the normative data for the adulthood" remains to be answered.