Twenty-five consecutive patients who had a variety of lumbar disorders and who underwent lumbar spinal fusion using the Diapason fixator were followed for a mean period of 20 months. The operations included 16 posterior lumbar interbody fusion (PLIF), 7 posterolateral fusion (PLF), and 2 combined PLIF and PLF (PLIF/PLF). As a control group, 38 patients undergoing PLIF using a Steffee VSP plate (VSP) were followed for a mean period of 24 months. There were no significant differences between the two groups regarding the operation time, blood loss, and improvement of preoperative symptoms. However, incidence of incomplete bony union and radiolucent zone around the screws were higher in the Diapason group than in the VSP group. Our study suggests that there was a possibility of insufficient rigidity of screw-rod fixation in the Diapason system.