59 patients with mid to high grade isthmic spondylolisthesis were randomly assigned into 1 of 2 groups to compare the effectiveness of posterior reduction and internal fixation with ball-point slide-type interbody distractors to only posterior reduction and internal fixation. The results of the study indicated that radiographic outcomes were significantly better for those who received posterior reduction and internal fixation with ball-point slide-type interbody distractors, and recovery rate in terms of ODI and VAS for low back pain improved more in the ball-point slide-type group than the control. Recovery rate of VAS pain for legs was comparable between the two groups following treatment.