ObjectiveTo compare the clinical efficacies and complications between the posterior lumbar interbody fusion(PLIF) using bilateral pedicle screw fixation and modified PLIF using unilateral pedicle screw fixation. MethodsA total of 96 patients who underwent lumbar spinal fusion operation during Feb. 2007 to May 2009 were divided into 2 groups. Group A included 40 patients (14 males and 26 female, average age being \[52.23±9.75\] years) receiving unilateral modified PLIF; Group B included 56 patients (22 males and 34 female, average age being \[56.02±10.25\] years) receiving bilateral PLIF. Oswestry disability index(ODI), visual analog scale (VAS), operating time, blood loss, length of hospital stay, hospitalization cost, fusion rates, complication rates, intervertebral height and medical expenses were all compared between the two groups. ResultsThe short-term ODI, VAS indices showed no significant difference between the two groups. Blood loss, operating time, and hospitalization cost of group A were significantly less than those in group B (P<0.05). Fusion rate was 100% in both groups 12 months after the operation. ConclusionModified PLIF using unilateral pedicle screw fixation is effective for lumbar spinal fusion, and it has the less trauma, risk and hospitalization cost compared with PLIF using bilateral pedicle screw fixation; but its long-term efficacy still needs to be further observed.