In vivo effects of axial loading on double-curve scoliotic spines.

The in vivo three-dimensional orientation of the vertebral columns in five adolescent idiopathic scoliotic subjects with double curves were examined in standing, supine, and supine positions with Cotrel traction postures using a biplanar radiographic technique. This analysis was compared with that obtained from a previous study on five healthy adolescent subjects to assess the postural changes and mechanical factors relating to the development of double-curve scoliotic deformity. Statistical analysis of vertebral orientation, rotation, disc distraction, and wedging between the normal and scoliotic subjects indicated that central intervertebral disc height and anteroposterior wedging were most consistently altered in double-curve scoliotic deformity. Since these two parameters relate directly to the geometry of the disc, the etiology of double-curve scoliosis may be related to a primary defect affecting the geometry of the intervertebral disc that results in a vertebral column which then undergoes rotational deformity.