Uncoupled neuro-osseous growth in adolescent idiopathic scoliosis? A preliminary study of 90 adolescents with whole-spine three-dimensional magnetic resonance imaging

Previous literatures revealed abnormal cross-sectional morphology of spinal cord in AIS, suggesting the presence of disproportional growth between the neural and skeletal system. No accurate measurement of whole spine by MRI multiplanar reconstruction and their correlation with Cobb angle were studied. In this study, MRI three-dimensional reconstruction of the whole spine was performed in 90 adolescents (49 AIS with thoracic/thoracolumbar curve, and 41 age-matched healthy controls). Measurements of the ratio of anteroposterior (AP) and transverse (TS) diameter of the cord, the concave and convex lateral cord space (LCS) were obtained at the apical level in AIS patients. Cerebellar tonsillar level related to the basion-opsithion line, location of conus medullaris, cord length, vertebral column length, cord/vertebral column length ratio were obtained. All of the same parameters were also measured in healthy controls at matched vertebral levels and their correlations with Cobb angle were made. We notice that AP, TS, AP/TS and LCS ratio were increased in AIS subjects with low-lying position of cerebellar tonsillar level and elevating position of conus medullary when compared with healthy controls (P < 0.01). AP, AP/TS and LCS ratio were correlated significantly with Cobb angle (P < 0.05). Cord length and vertebral column length were not significantly different between AIS and control group. However, cord/vertebral column length ratio was significantly smaller in AIS group (P < 0.01). Cord length, vertebral column length and cord/vertebral column length ratio were not related with age or Cobb angle (P > 0.05). These data suggest the presence of uncoupled neuro-osseous growth along the longitudinal axis of spinal cord with associated morphologic changes of cross-sectional configuration and relative position of the cord. Some changes are significantly relevant with Cobb angle, which may indicate pathogenesis of AIS.