This study was performed to establish a radiological indication and contraindication of indirect decompression in the thoracolumbar burst fracture as well as to clarify an acceptable degree of the canal constriction to enhance neurologic recovery and to prevent the spinal stenosis. The canal diameter ratio (CDR) of the constricted level was determined using pre-and post-operative CAT images of 31 thoracolumbar burst fractures, decompressed indirectly. The acceptable CDR was decided by the lower limit of the 95% confidence interval of the post-operative CDR in cases without neurologic deficit associated with the canal constriction. A radiological indication and contraindication of indirect decompression was establish based on the calculation of the discriminant equation and linear regression equation respectively. The results were as followings.