This study was prepared in Bakırköy Prof. Dr. Mazhar Osman Hospital for Neurological and Mental Disorders in 2003. The aim of this study is to investigate the outcome of simple discectomy, discectomy with posterior luinbar interbody fusion (PLIF), and discectomy plus PLIF and posterior transpedicular screw fixation by analysis of X-ray findings. Patients investigated in this study were grouped into three groups namely, simple discectomy, discectomy plus PLIF, and discectomy plus PLIF plus posterior transpedicular screw fixation. There were 23 patients in the first group and 5 patients in each of the other two groups. In the postoperative period, lateral lumbosacral X-rays were taken and measurements of the pre-determined 4 parameters were calculated; intervertebral disc space height and the width, height and narrowest width measurements of the intervertebral foramen were measured. Comparisons between groups and different parameters were done by using `Student T Test' (SPSS for Windows, v-I 1,5). Simple discectomy caused increased degeneration of the disc space. In the second and third group (PLIF and PLIF plus transpedicular screw fixation) degenerative changes were minimal as seen in the first group. The third group was better in this aspect. Transpedicular screw fixation with PLIF group seemed to be superior to the other two groups in term of biomechanical stability and prevention of further degeneration and the second group was inferior to the third but superior to the first group in this aspect.