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We retrospectively reviewed 57 patients with L4–L5 degenerative spondylolisthesis (L4–L5 DS) who underwent posterior decompression and posterolateral fusion of L4–L5 without (Group A) or with (Group B) transpedicular screw instrumentation at least 2 years earlier. The clinical results and fusion rate were similar between Groups A and B, that is, a 72.4% satisfactory outcome with a fusion rate of 82.8% in Group A versus 82.1% satisfactory outcome with a 92.8% fusion rate in Group B. Screw instrumentation reduced postoperative low back pain and resulted in a lordotic slip angle of L4–L5. However, in patients with radiologically excessive segmental motion showing a translational motion of 3 mm or more, flexion angulation of −5° or less, and a slip angle of −5° or less at the site of spondylolisthesis (L4–L5), the kyphotic slip angle (L4–L5) tended to increase after surgery. In the future, in patients with radiologically excessive segmental motion, this point should be considered, and surgical techniques should be evaluated. Our results suggest that the validity of the general addition of screw instrumentation to L4–L5 fusion for L4–L5 degenerative spondylolisthesis is low.