Background: Spondylolisthesis occurs when there is an anterior slippage of one vertebral body relative to its caudal vertebral body.

The ideal surgical treatment remains controversial. Some neurosurgery surgeons PLIF but others prefer PLF.

Aim: The aim of the work is to compare the prognosis and outcome between PLIF & PLF in spondylolisthesis.

Patient and Methods: This is a prospective study which was conducted on 40 patients with spondylolisthesis who were admitted to Minia university hospital between March 2020 and September 2021, and were randomly assigned in to 2 groups: 20 patient in each group, the 1st underwent PLIF while the 2nd underwent PLF.

• Results: In PLIF: the mean age was 47.85 (27-61 years). In PLF: the mean age was 46.7 (28-63 years) . all patients were presented with low back pain while radicular pain was present in 65% and 75% in both groups respectively. 85% of patients had a single level lithesis either L4-5 or L5-S1 and 15% had double level lithesis in the PLIF group these percentages were nearly the same in the PLF group with 80% for single level lithesis and 20% percent with double level lithesis. The outcome in the two groups was excellent in 65% and 50% respectively, good in 20% in both groups , fair in 10% and 25% respectively and poor in only 5% of each group. Complication rates were low.

Conclusions: PLIF had advantages in fusion rates , reduction of pain with no other significant difference regarding other points of comparison.