Anatomical configuration of the spinal column in the supine position. III. Comparison of adolescent and adult volunteers.

To clarify the anatomical configuration of the spinal column in the adolescent in the supine position, we have studied 10 adolescent (13-17 yr) and 10 adult (26-38 yr) volunteers using magnetic resonance imaging. T1-weighted sagittal midline magnetic resonance images of the spinal column were obtained with subjects in the supine position. The maximum angles of decline of the lumbar spinal canal did not differ between the adolescent (mean 13.6 (SD 3.3) degrees) and adult (12.4 (3.8) degrees) groups. The maximum angles of incline of the upper thoracic spinal canal were smaller in the adolescent group (15.9 (4.7) degrees) than in the adult group (26.4 (5.8) degrees). The median highest point of the lumbar spinal canal was located at L4 (range L3-4 to L4-5) in both groups. The lowest points of the thoracic spinal canal in the adolescent and adult groups were located at T8-9 (T7 to T9) and T8 (T6-7 to T9), respectively. This study showed that thoracic kyphotic curvature in adolescents was reduced significantly in the supine position compared with that in adults. This minimized thoracic kyphosis may explain, in part, the enhanced cephalad spread of subarachnoid hyperbaric anaesthetic solutions in adolescents.