Analysis of single cage position in transforaminal lumbar interbody fusion through digital images

Purpose The purpose of this study was to investigate the position of single cage inserted using oblique-oriented technique in transforaminal lumbar interbody fusion (TLIF) on digital images of computed tomography (CT). Methods From January to August 2015, 44 consecutive patients with degenerative lumbar disease who underwent TLIF in the L4/5 level were retrospectively studied in our department. The single cage was inserted using the oblique-oriented technique; as the main purpose of the study, its position was analyzed using post-operative digital computed tomography images. Results All cages used in the study had the same length of 36 mm, which were inserted into the discs with a 46.04 ± 3.09-mm horizontal diameter and 34.25 ± 3.59-mm longitudinal diameter. The horizontal and longitudinal diameter of the treated disk established the coordinate. The horizontal and longitudinal coordinate values of the centre of the cage were 0.08 ± 4.12 and 1.20 ± 2.76 mm, respectively. The horizontal distance of the cage centre from the midpoint of the disc negatively correlated with that of the entry point from the midpoint of the disc in the coronal plane. Conclusion A longer single cage can be placed into the L4/5 level disk by inserting it using the oblique-oriented technique. Its center can reach the midpoint of the treated disk in the coronal plane and the anterior position of the disk in the sagittal plane. The entry point of the cage is the further away from the midpoint of the disk; the cage is the more apt to reach the center of the disk in the coronal plane.