Anterior spinal overgrowth of the thoracic spine may not be involved in the initiation of adolescent idiopathic scoliosis

OBJECTIVE:
To compare vertebral morphology among adolescent idiopathic scoliosis (AIS) patients, Chiari I malformations (CMS)-associated scoliosis patients and normal controls, with the goal of determining the role of anterior column overgrowth in the development of AIS.

METHODS:
One hundred forty female subjects were enrolled (50 AIS, 40 CMS and 50 controls). Thoracic CT images were obtained for all subjects. Anterior and posterior heights of the vertebral body (VBHa and VBHp) and the height of pedicles (PH) were measured for each level. Finally, ratios of VBHa and VBHp to PH were calculated and compared among the three groups.

RESULTS:
Compared with the control group, both AIS and CMS groups exhibited consistently longer VBHa and VBHp for most thoracic vertebral bodies, while PH of most vertebral bodies were shorter in both AIS and CMS groups. Moreover, the ratios for differential growth between the anterior and posterior elements of each thoracic vertebra in both the AIS and CMS groups were significantly larger than the ratios in the control group. However, for all mentioned parameters, there were no significant differences between the AIS and the CMS groups.

CONCLUSIONS:
Faster growth of the anterior spinal column was confirmed by longer vertebral bodies and shorter pedicles in both patient groups: those with AIS and those with scoliosis secondary to CMS. Relative anterior spinal overgrowth of the thoracic spine is not involved in the initiation of AIS, and the abnormal growth pattern of the vertebral body in AIS might be a secondary change to spinal curve.