Introduction: The need for reduction of high grade spondyloisthesis continues to be a source of debate. Recent papers report on better outcomes with “in situ” fusion.

MATERIAL AND Methods: We retrospectively revised 17 patients treated for high grade spondylolisthesis. Average age 16.3 years, average follow-up 76.4 months. Average slip was 78.47%. Posterior approach in 14, double approach in 3. L4-S1 fusion in 16. In 3 patients posterior fusion with double fibular graft and screws was performed. Reduction was performed in 14 cases. Radiographic, clinical data and complications were assessed.

Results: Slip improved from 75.07% to 41.3% (44% correction, p=0.001) and slip angle measured in the superior end plate of L5 from 17.7% to 8.3% (53.1% correction, p=0.05) in the reduction group. There were no permanent neurological complications and no dural tears. Global SRS-22 scores were 4.28 in the reduction group and 4.03 in the non reduction group (p=0.14), satisfaction with the treatment was 4.4. Two patients had to be reoperated because of implant failure and progression. Two asymptomatic screw breaks were noted.

DISCUSSION AND Conclusions: We believe that partial reduction of high grade spondylolisthesis can be safely obtained with a correct surgical technique, rendering slightly better results than “in situ” fusion with no increase in complications.