Analysis of Pre-existent Vertebral Rotation in the Normal Spine

Summary: A new CT measurement method showed that the normal, non-scoliotic thoracic spine contains a pre-existent axial vertebral rotation to the right, similar to the typical rotational pattern that is seen in idiopathic scoliosis. We assume that idiopathic scoliosis is not a deviation from but merely a decompensation of normal human spinal architecture. Furthermore a relationship was demonstrated between the position of the thoracic aorta and this vertebral rotation.

Study Design: A newly developed CT measurement method was used to investigate axial rotation of thoracic and lumbar vertebrae in the normal, non-scoliotic spine and to analyze its relation to the descending aorta.

Objectives: To identify a pre-existent rotational pattern in the normal, non-scoliotic spine, predisposing to the typical 3D deformity seen in adolescent idiopathic scoliosis (AIS).

Summary of Background Data: The data available on axial rotation measurements in the normal spine are based on standard radiographs or limited to only a few vertebrae. Systematic analysis of the thoracic and lumbar vertebrae of the normal spine, based on computed tomography, has not been performed.

Methods: CT scans of the thorax and abdomen of 38 persons without clinical or radiological evidence of scoliosis were obtained and used to measure vertebral rotation in the transverse plane. Furthermore we developed a simplified 2D model to describe the influence of the pulsatile force of the aorta working on the spine.

Results: The results of the present study show that the normal, non-scoliotic thoracic spine contains a significant axial rotation to the right in 89% of the cases. This curve pattern is present in both males and females. Furthermore we noted a significant correlation between the influence of the pulsatile force of the descending aorta and the angle of the vertebral rotation.

Conclusion: The majority of normal, non-scoliotic spines demonstrate a pre-existent rotation to the right in the thoracic area that is consistent with what is found in idiopathic scoliosis as far as direction and apex is concerned. Furthermore, there appears to be a significant relation between this vertebral rotation and the position of the descending aorta.