Fig. 1

a Cross inferior vertebral notch to make the corresponding parallel line of the inferior endplate of the vertebral body and intersect the vertebral body at point Q. Point A, 3 mm below point Q, was selected as the observation point on the posterior vertebral body margin to determine whether bone cement entered the spinal canal. b Posterior margin bone cortex points A and B of the thoracic vertebral body were determined on the axial CT view at the same level as in a. c Point A was reconfirmed on the coronal view by a synchronous localization technique. d Line L2 at point A is perpendicular to the inferior endplate on the sagittal view