Objective      To investigate the morphology of the costo-transverse foramen in adolescent idiopathic scoliosis (AIS) patients and normal people for comparison

and to discuss the feasibility of implantation for epiphyseal growth modulation via that space in treating immature idiopathic scoliosis.       Methods      This is a retrospective study using three-dimensional computerized tomography (CT) to test the costo-transverse foramen in 104 AIS pati

ents (49 males and 75 females

10 years old in average) from July 2005 to March 2013 and 38 matched normal people (15 males and 23 females

11 years old in average) from May 2007 to December 2012. According to the Lenke classification

there were 58 cases of Lenke Ⅰ and 46 cases of Lenke Ⅲ in the AIS group. The average Cobb angle of the main thoracic curve was 45.95 degree in the AIS group. Based on the three-dimensional reconstruction of CT data in Amira software

the cross sectional areas (CSAs) of the costo-transverse foramen in different levels were measured in both AIS and normal people. Comparisons were made within and between the AIS and normal people groups in the aspect of costo-transverse foramen CSA. Furthermore

the correlation between the CSA and the Cobb angle was also analyzed. The possible factors contributing to the foramen CSA were discussed and summarized.       Results      The average CSA in the AIS group ranged from 24.67 mm

2

to 35.57 mm

2

. The CSAs in apex levels were significantly smaller than those in other levels (

P

0.05). The CSA was negatively correlated with the magnitude of Cobb angle （r=-0.068

P

0.05）. The average CSA of normal people group ranged from 28.26 mm

2

to 32.57 mm

2

. The CSA of AIS group was significantly greater than that of the corresponding level in normal people group (

P

0.05).       Conclusion      Comparing to the normal people

the CSA of costo-transverse foramen in AIS patient is greater

which seems to support the proposal of implant placement via this foramen in epiphyseal growth modulation.